EPA 815-R-00-013

Proposed Arsenic in Drinking Water Rule

Regulatory Impact Analysis

Developed for:

Office of Ground Water and Drinking Water

U.S. Environmental Protection Agency

401 M Street, S.W.

Washington, DC 20460

John B. Bennett

 Work Assignment Manager

Developed by:

Abt Associates Inc.

4800 Montgomery Lane

Bethesda, MD 20814

Gerald D. Stedge, Ph.D.

Principal Investigator

June 2000

Table of Contents iii Proposed Arsenic in Drinking Water Rule RIA

Contents

1 Executive Summary ...................................................... 1-1

1.1 Regulatory Background ........................................... 1-1

1.2 Health Effects of Arsenic ........................................... 1-1

1.3 Regulatory Alternatives Considered ................................... 1-2

1.4 Benefits and Costs of the Proposed Rule ............................... 1-3

2 Need for the Proposal .................................................... 2-1

2.1 Introduction ..................................................... 2-1

2.2 Public Health Concerns to be Addressed ............................... 2-2

2.2.1 Health Effects of Arsenic .................................... 2-2

2.2.2 Sources and Mechanisms of Exposure .......................... 2-4

2.3 Regulatory History ................................................ 2-4

2.4 Rationale for the Regulation ......................................... 2-7

2.4.1 Statutory Authority ........................................ 2-7

2.4.2 Economic Rationale for Regulation ............................ 2-8

3. Consideration of Regulatory Alternatives ..................................... 3-1

3.1 Regulatory Approaches ............................................ 3-1

3.1.1 Determining the Standard ................................... 3-1

3.1.2 Determining the MCLG ..................................... 3-1

3.1.3 Determining an MCL ....................................... 3-2

3.1.4 Variances and Exemptions ................................... 3-3

3.1.5 Analytic Methods .......................................... 3-3

3.2 Regulatory Alternatives Considered and Proposed Rule .................... 3-4

3.2.1 Applicability ............................................. 3-4

3.2.2 MCL ................................................... 3-4

3.2.3 Monitoring .............................................. 3-5

3.2.4 Compliance Technologies and Variances ........................ 3-5

3.2.5 Monitoring Waivers ........................................ 3-5

3.2.6 Implementation ........................................... 3-6
Table of Contents iv Proposed Arsenic in Drinking Water Rule RIA

4. Baseline Analysis ........................................................ 4-1

4.1 Introduction ..................................................... 4-1

4.2 Industry Profile .................................................. 4-1

4.2.1 Definitions ............................................... 4-1

4.2.2 Sources of Industry Profile Data .............................. 4-2

4.2.3 Number and Size of Public Water Systems ....................... 4-2

4.2.4 System Size and Population Served ............................ 4-4

4.2.5 Number of Entry Points ..................................... 4-6

4.2.6 Number of Households ..................................... 4-6

4.2.7 Production Profile ......................................... 4-7

4.2.8 Treatment Profile ......................................... 4-10

4.2.9 Financial Profile .......................................... 4-10

4.3 Occurrences of Arsenic ........................................... 4-11

5. Benefits Analysis ....................................................... 5-1

5.1 Nature of Regulatory Benefits ....................................... 5-1

5.2 Health Effects ................................................... 5-1

5.2.1 Overview ................................................ 5-1

5.2.2 Carcinogenic Effects ....................................... 5-2

5.2.3 Noncarcinogenic Effects .................................... 5-3

5.2.4 Susceptible Subgroups ...................................... 5-5

5.2.4.1 Definition ........................................ 5-5

5.2.4.2 Children ......................................... 5-6

5.2.4.3 Genetic Predispositions and Dietary Insufficiency .......... 5-6

5.2.4.4 Individuals with Pre-existing Organ Susceptibilities ......... 5-7

5.2.4.5 Individuals Exposed via Non-water Sources .............. 5-7

5.3 Quantitative Benefits of Avoiding Bladder Cancer ........................ 5-7

5.3.1 Risk Assessment for Bladder Cancer Resulting from Arsenic Exposure . 5-8

5.3.1.1 Risk Assessment Methodology ........................ 5-8

5.3.1.2 Risk Assessment Results and Benefit Estimates ........... 5-16

5.4 Other Benefits of Reductions in Arsenic Exposure ....................... 5-24

5.4.1 Ecological Effects ........................................ 5-24

5.4.2 Drinking Water Quality and Public Perception ................... 5-24
Table of Contents v Proposed Arsenic in Drinking Water Rule RIA

6. Cost Analysis .......................................................... 6-1

6.1 Introduction ..................................................... 6-1

6.2 Methodology .................................................... 6-1

6.2.1 Description of Available Technologies .......................... 6-1

6.2.2 Unit Costs and Compliance Assumptions ........................ 6-4

6.2.3 Monitoring and Administrative Costs .......................... 6-11

6.2.4 Predicting Compliance Decisions (Compliance Decision Tree) ....... 6-14

6.2.5 Calculating Costs ......................................... 6-15

6.3 Results ........................................................ 6-24

6.3.1 National Costs ........................................... 6-24

6.3.2 Costs by System Size and Type .............................. 6-27

6.3.3 Costs per Household ...................................... 6-29

7. Comparison of Costs and Benefits .......................................... 7-1

7.1 Introduction ..................................................... 7-1

7.2 Summary of National Costs and Benefits ............................... 7-1

7.2.1 National Cost Estimates ..................................... 7-1

7.2.2 National Benefits Estimates .................................. 7-1

7.3 Comparison of Benefits and Costs .................................... 7-2

7.3.1 National Net Benefits and National Benefit-Cost Comparison ........ 7-2

7.3.2 Cost-Effectiveness ......................................... 7-5

7.4 Other Benefits ................................................... 7-7

8. Economic Impact Analyses ................................................ 8-1

8.1 Introduction .................................................. 8-1

8.2 Regulatory Flexibility Act and Small Business Regulatory Enforcement 

Fairness Act .................................................. 8-2

8.2.1 Summary of EPA’s Small Business Consultations ................. 8-2

8.2.2 Definition of Small Entity for the Arsenic Rule .................... 8-5

8.2.3 Requirements for the Initial Regulatory Flexibility Analysis .......... 8-6

8.2.4 Small Entity Impacts ....................................... 8-7

8.2.5 Small System Affordability .................................. 8-21
Table of Contents vi Proposed Arsenic in Drinking Water Rule RIA

8.3 Coordination With Other Federal Rules ............................ 8-24

8.4 Minimization of Economic Burden ................................ 8-25

8.5 Unfunded Mandates Reform Act ................................. 8-26

8.5.1 Social Costs and Benefits ................................... 8-27

8.5.2 State and Local Administrative Costs .......................... 8-28

8.5.3 Future Compliance Costs and Disproportionate Budgetary Effects .... 8-28

8.5.4 Macroeconomic Effects .................................... 8-34

8.5.5 Consultation with State, Local, and Tribal Government ............ 8-34

8.5.6 State, Local, and Tribal Government Concerns .................. 8-36

8.5.7 Regulatory Alternatives Considered ........................... 8-36

8.5.8 Impacts on Small Governments .............................. 8-36

8.6 Effect of Compliance With the Arsenic Rule on the Technical, 

Financial, and Managerial Capacity of Public Water Systems ............ 8-37

8.7 Paperwork Reduction Act ...................................... 8-38

8.8 Protecting Children From Environmental Health Risks and Safety Risks .... 8-39

8.9 Environmental Justice .......................................... 8-39

8.10 Health Risk Reduction and Cost Analysis ........................... 8-40

8.10.1 Quantifiable and Non-Quantifiable Health Risk Reduction Benefits . . 8-41

8.10.2 Quantifiable and Non-Quantifiable Costs ...................... 8-43

References ............................................................... R-1

Appendix A: Decision Tree and Decision Matrix .................................. A-1

Appendix B: Bladder Cancer Risk Analysis ...................................... B-1
Table of Exhibits Proposed Arsenic in Drinking Water

vii Rule RIA

Exhibits

Exhibit 1-1 Estimated Monetized Total Cancer Health Benefits and 

Non-Quanitifiable Health Benefits from Reducing Arsenic in CWSs ........ 1-4

Exhibit 1-2 Total National Cost of Compliance ................................... 1-5

Exhibit 1-3 Net Benefits and Benefit-Cost Ratios of Each Regulatory Option ............ 1-6

Exhibit 4-1 Total Number of Systems by Size, Type and Ownership ................... 4-3

Exhibit 4-2 Total Population Served of Water Systems by Source Water, 

System Type and Service Population Category ........................ 4-4

Exhibit 4-3 Characteristics of NCWSs Affected by the Arsenic Rule ................... 4-5

Exhibit 4-4 Average Number of Entry Points per Ground Water System ................ 4-6

Exhibit 4-5 Water Consumption per Residential Connection and Number 

of Residential Connections per System .............................. 4-7

Exhibit 4-6 Design Capacity of CWS Plants by Source, Ownership and System Size ....... 4-8

Exhibit 4-7 Daily Production of CWS Plants by Source, Ownership, and System Size ...... 4-9

Exhibit 4-8 Percentage of CWSs with Various Treatments In-Place ................... 4-10

Exhibit 4-9 Baseline Revenues and Expenses for CWSs ............................ 4-11

Exhibit 4-10 Arsenic Occurrence in CWSs at Various Concentration Levels ............ 4-13

Exhibit 4-11 Number of CWSs Exceeding Various Arsenic MCL Concentrations ........ 4-13

Exhibit 5-1 Adverse Noncarcinogenic Health Effects Reported in Humans in NRC (1999)

 as Potentially Associated with Arsenic, by Organ System Affected ......... 5-4

Exhibit 5-2 Components of the Bladder Cancer Risk Assessment ...................... 5-9

Exhibit 5-3 Source of Water Consumed ........................................ 5-9

Exhibit 5-4 EPA Assumed Life-Time Bladder Risk Estimates for Bladder 

Cancer Among Males .......................................... 5-11
Table of Exhibits Proposed Arsenic in Drinking Water

viii Rule RIA

Exhibit 5-5 Life-Long Relative Exposure Factors ................................. 5-11

Exhibit 5-6 Exposure Factors Used in the NTNC Risk Assessment ................... 5-13

Exhibit 5-7 Composition of NTNCs ........................................... 5-14

Exhibit 5-8 School Children Risk Associated with Current Arsenic Exposure in NTNCs ... 5-15

Exhibit 5-9 Mean Bladder Cancer Risks for U.S. Populations Exposed At 

or Above MCL Options, after Treatment ........................... 5-17

Exhibit 5-10 Exposed Population at 10-4 Risk or Higher for Bladder Cancer After

 Treatment (Community Water Consumption Data) ................... 5-17

Exhibit 5-11 Exposed Population at 10-4 Risk or Higher for Bladder Cancer After

Treatment (Total Water Consumption Data) ......................... 5-17

Exhibit 5-12 Annual Bladder Cancer Cases Avoided from Reducing Arsenic in CWSs ..... 5-18

Exhibit 5-13 Potential Annual Lung Cancer Cases Avoided

from Reducing Arsenic in CWSs .................................. 5-19

Exhibit 5-14 Lifetime Avoided Medical Costs for Survivors (preliminary estimates) ....... 5-21

Exhibit 5-15 Estimated Monetized Bladder Cancer Health Benefits and 

Non-Quantifiable Health Benefits from Reducing Arsenic in CWSs ....... 5-22

Exhibit 5-16 Mean Annual Bladder Cancer Risks, Exposed Population, and 

Annual Cancer Cases Avoided in NTNCs ........................... 5-23

Exhibit 5-17 Sensitive Group Evaluation of Lifetime Risks ......................... 5-23

Exhibit 6-1 Arsenic Rule Treatment Trains by Compliance Technologies 

Component, with Associated Removal Efficiencies ..................... 6-3

Exhibit 6-2 Average Compliance Technology Costs ................................ 6-5

Exhibit 6-3(a) Estimated One-Time State Resources Required for Initiation 

of the Arsenic Rule ............................................ 6-13

Exhibit 6-3(b) Estimated One-Time System Resources Required for Initiation 

of the Arsenic Rule ............................................ 6-13
Table of Exhibits Proposed Arsenic in Drinking Water

ix Rule RIA

Exhibit 6-4 Unit Resources Required for Monitoring, Implementation and Administration . . 6-14

Exhibit 6-5 Flow Regression Parameters by Water Source and System Ownership ........ 6-18

Exhibit 6-6 Arsenic Occurrence by Water Source ................................ 6-18

Exhibit 6-7 Summary of Recommended Cost of Capital Estimates .................... 6-20

Exhibit 6-8 Annual Treatment Costs for Three Large CWSs Expected to Undertake 

or Modify Treatment Practice to Comply with the Arsenic Rule .......... 6-23

Exhibit 6-9 Annual National System and State Compliance Costs

(CWSs and NTNCs Comply With MCL) ........................... 6-25

Exhibit 6-10 Annual National System and State Compliance Costs

(CWSs Comply With MCL / NTNCs Monitor) ....................... 6-26

Exhibit 6-11 Total Annual CWS Treatment Costs Across MCL Options by 

System Size and Type .......................................... 6-27

Exhibit 6-12 Total Annual CWS Monitoring and Administrative Costs Across 

MCL Options by System Size and Type ............................ 6-28

Exhibit 6-13 Number of Households in CWSs Expected to Treat by Size 

Category and MCL Option ...................................... 6-29

Exhibit 6-14 Mean Annual Household Costs Across MCL Options by System Size ....... 6-30

Exhibit 6-15 Annual Treatment Costs Per Household Across Public GW CWSs 

Expected to Treat and Serving <10,000 People (MCL 3μg/L) ........... 6-31

Exhibit 6-16 Annual Treatment Costs Per Household Across Public GW CWSs 

Expected to Treat and Serving <10,000 People (MCL 5μg/L) ........... 6-31

Exhibit 6-17 Annual Treatment Costs Per Household Across Public GW CWSs 

Expected to Treat and Serving <10,000 People (MCL 10μg/L) .......... 6-32

Exhibit 6-18 Annual Treatment Costs Per Household Across Public GW CWSs 

Expected to Treat and Serving <10,000 People (MCL 20μg/L) .......... 6-32

Exhibit 7-1 Summary of Annual National Net Benefits and Benefit-Cost Ratios,

CWSs Comply With MCL / NTNCs Only Monitor ..................... 7-3
Table of Exhibits Proposed Arsenic in Drinking Water

x Rule RIA

Exhibit 7-2 Comparison of Costs and Benefits of Bladder Cancer Cases Avoided

(CWSs Comply with MCL / NTNCs Monitor, 7% Discount Rate) ......... 7-4

Exhibit 7-3 Cost per Bladder Cancer Case Avoided for the Proposed Arsenic Rule ........ 7-5

Exhibit 7-4 Comparison of Annual Costs to Cases of Bladder Cancer per Year

(7% Discount Rate) ............................................ 7-6

Exhibit 7-5 Incremental Cost per Incremental Bladder Cancer Case Avoided

(CWSs, 7% Discount Rate) ...................................... 7-7

Exhibit 8-1 Profile of the Universe of Small Water Systems Regulated Under 

the Arsenic Rule ............................................... 8-6

Exhibit 8-2 Number of CWSs Expected to Undertake or Modify Treatment Practice ....... 8-7

Exhibit 8-3 Number of CWSs Expected to Undertake or Modify Treatment 

Practice (MCL 3μg/L) .......................................... 8-8

Exhibit 8-4 Number of CWSs Expected to Undertake or Modify Treatment 

Practice (MCL 5μg/L) .......................................... 8-8

Exhibit 8-5 Number of CWSs Expected to Undertake or Modify Treatment 

Practice (MCL 10μg/L) ......................................... 8-9

Exhibit 8-6 Number of CWSs Expected to Undertake or Modify Treatment 

Practice (MCL 20μg/L) ......................................... 8-9

Exhibit 8-7 Average Annual System Compliance Costs for CWSs .................... 8-10

Exhibit 8-8 Comparison of CWS Baseline and Post-Compliance Total 

Expenses for Systems Serving <100 People (MCL 3μg/L) .............. 8-11

Exhibit 8-9 Comparison of CWS Baseline and Post-Compliance Total 

Expenses for Systems Serving <100 People (MCL 5μg/L) .............. 8-11

Exhibit 8-10 Comparison of CWS Baseline and Post-Compliance Total 

Expenses for Systems Serving <100 People (MCL 10μg/L) ............. 8-12

Exhibit 8-11 Comparison of CWS Baseline and Post-Compliance Total 

Expenses for Systems Serving <100 People (MCL 20μg/L) ............. 8-12
Table of Exhibits Proposed Arsenic in Drinking Water

xi Rule RIA

Exhibit 8-12 Comparison of CWS Baseline and Post-Compliance Total 

Expenses for Systems Serving 101-500 People (MCL 3μg/L) ............ 8-13

Exhibit 8-13 Comparison of CWS Baseline and Post-Compliance Total 

Expenses for Systems Serving 101-500 People (MCL 5μg/L) ............ 8-13

Exhibit 8-14 Comparison of CWS Baseline and Post-Compliance Total

Expenses for Systems Serving 101-500 People (MCL 10μg/L) ........... 8-14

Exhibit 8-15 Comparison of CWS Baseline and Post-Compliance Total 

Expenses for Systems Serving 101-500 (MCL 20μg/L) ................ 8-14

Exhibit 8-16 Comparison of CWS Baseline and Post-Compliance Total 

Expenses for Systems Serving 501-1,000 People (MCL 3μg/L) .......... 8-15

Exhibit 8-17 Comparison of CWS Baseline and Post-Compliance Total 

Expenses for Systems Serving 501-1,000 (MCL 5μg/L) ................ 8-15

Exhibit 8-18 Comparison of CWS Baseline and Post-Compliance Total 

Expenses for Systems Serving 501-1,000 People (MCL 10μg/L) ......... 8-16

Exhibit 8-19 Comparison of CWS Baseline and Post-Compliance Total

Expenses for Systems Serving 501-1,000 People (MCL 20μg/L) ......... 8-16

Exhibit 8-20 Comparison of CWS Baseline and Post-Compliance Total 

Expenses for Systems Serving 1,001-3,300 People (MCL 3μg/L) ......... 8-17

Exhibit 8-21 Comparison of CWS Baseline and Post-Compliance Total

Expenses for Systems Serving 1,001-3,300 People (MCL 5μg/L) ......... 8-17

Exhibit 8-22 Comparison of CWS Baseline and Post-Compliance Total 

Expenses for Systems Serving 1,001-3,300 People (MCL 10μg/L) ........ 8-18

Exhibit 8-23 Comparison of CWS Baseline and Post-Compliance Total 

Expenses for Systems Serving 1,001-3,300 People (MCL 20μg/L) ........ 8-18

Exhibit 8-24 Comparison of CWS Baseline and Post-Compliance Total 

Expenses for Systems Serving 3,301-10,000 People (MCL 3μg/L) ........ 8-19

Exhibit 8-25 Comparison of CWS Baseline and Post-Compliance Total 

Expenses for Systems Serving 3,301-10,000 People (MCL 5μg/L) ........ 8-19
Table of Exhibits Proposed Arsenic in Drinking Water

xii Rule RIA

Exhibit 8-26 Comparison of CWS Baseline and Post-Compliance Total

 Expenses for Systems Serving 3,301-10,000 People (MCL 10μg/L) ...... 8-20

Exhibit 8-27 Comparison of CWS Baseline and Post-Compliance Total 

Expenses for Systems Serving 3,301-10,000 People (MCL 20μg/L) ....... 8-20

Exhibit 8-28 Mean Annual Costs to Households Served by CWSs, by Size Category ...... 8-22

Exhibit 8-29 Average Annual Cost per CWS by Ownership ......................... 8-30

Exhibit 8-30 Annual Compliance Costs per Household for CWSs Exceeding MCLs ....... 8-32

Exhibit 8-31 Annual Compliance Costs per Household for CWSs Exceeding 

MCLs, as a Percentage of Median Household Income ................. 8-33

Exhibit 8-32 Mean Bladder Cancer Risks, Exposed Population, and Annual 

Cancer Cases Avoided in CWSs .................................. 8-41

Exhibit 8-33 Annual Bladder Cancer Cases Avoided from Reducing Arsenic in CWSs ..... 8-42

Exhibit 8-34 Potential Annual Lung Cancer Cases Avoided from Reducing 

Arsenic in CWSs ............................................. 8-42

Exhibit 8-35 Estimated Monetized Total Cancer Health Benefits and

Non-Quantifiable Health Benefits from Reducing Arsenic in CWSs ........ 8-43

Exhibit 8-36 Summary of the Total Annual National Costs of Compliance ............. 8-44

Exhibit 8-37 Mean Annual Costs per Household in CWSs .......................... 8-45

Exhibit 8-38 Cost per Bladder Cancer Case Avoided for the Proposed Arsenic Rule ...... 8-46
Chapter 1, Executive Summary 1-1 Proposed Arsenic in Drinking Water Rule RIA

Chapter 1: Executive Summary

1.1 Regulatory Background

An enforceable standard of 50 μg/L currently exists for arsenic in community water systems under

the National Interim Primary Drinking Water Regulations (NPDWR) (40 CFR 59566). In

§1412(b)(12)(A) of the SDWA, as amended in 1996, Congress specifically directed EPA to issue

a final regulation by January 1, 2001. At the same time, Congress directed EPA to develop a

research plan to reduce the uncertainty in assessing health risks from low levels of arsenic by

February 2, 1997, and conduct the research in consultation with the National Academy of

Sciences, other Federal agencies, and interested public and private entities.

This document analyzes the impacts of the proposed rule which revises the current standard as

follows: 

1) reduces the current MCL for arsenic in community water systems from 50 μg/L to 5

μg/L; 

2) requires nontransient non-community water systems (NTNC) to perform compliance

monitoring; and 

3) revises the current monitoring requirements to make them consistent with the Standard

Monitoring Framework (40 CFR 141.23(c)).

1.2 Health Effects of Arsenic

Arsenic's carcinogenic role was noted over 100 years ago (NCI, 1999) and has been studied ever

since. The Agency has classified arsenic as a Class A human carcinogen, “based on sufficient

evidence from human data. An increased lung cancer mortality was observed in multiple human

populations exposed primarily through inhalation. Also, increased mortality from multiple internal

organ cancers (liver, kidney, lung, and bladder) and an increased incidence of skin cancer were

observed in populations consuming drinking water high in inorganic arsenic.”

A 1999 NRC report on arsenic states that "epidemiological studies ... clearly show associations of

arsenic with several internal cancers at exposure concentrations of several hundred micrograms

per liter of drinking water." Ten epidemiological studies covering eight organ systems have

quantitative data for risk assessment (NRC, 1999, Table 4-1). The organ systems where cancers

in humans have been identified include skin, bladder, lung, kidney, nasal, liver, and prostate.

Table 10-6 of the same NRC report provides risk parameters for three cancers: bladder, lung, and

liver cancer. Considering all cancers in aggregate, the NRC states that “considering the data on

bladder and lung cancer in both sexes noted in the studies ... a similar approach for all cancers

could easily result in a combined cancer risk on the order of 1 in 100” (at the current MCL of 50

μg/L).
Chapter 1, Executive Summary 1-2 Proposed Arsenic in Drinking Water Rule RIA

New data provide additional health effects information on both carcinogenic and noncarcinogenic

effects of arsenic. A recent study by Tsai et al. (1999) of a population that has been studied over

many years in Taiwan has provided standardized mortality ratios (SMRs) for 23 cancerous and

non-cancerous causes of death in women and 27 causes of death in men at statistically significant

levels in an area of Taiwan with elevated arsenic exposures (Tsai et al., 1999). SMRs are an

expression of the ratio between deaths that were observed in an area with elevated arsenic levels

and those that were expected to occur, based on the mortality experience of the populations in

nearby areas without elevated arsenic levels. Drinking water (250-1,140 μg/L) and soil (5.3-11.2

mg/kg) in the Tsai et al. (1999) population study had very high arsenic content.

Tsai et al. (1999) identified “bronchitis, liver cirrhosis, nephropathy, intestinal cancer, rectal

cancer, laryngeal cancer, and cerebrovascular disease” as possibly “related to chronic arsenic

exposure via drinking water,” which had not been reported before. In addition, the study area had

upper respiratory tract cancers previously only related to occupational inhalation. High male

mortality rate (SMR > 3) existed for bladder, kidney, skin, lung, and nasal cavity cancers and for

vascular disease. However, the authors noted that the mortality range was marginal for leukemia,

cerebrovascular disease, liver cirrhosis, nephropathy (kidney), and diabetes. Females also had

high mortalities for laryngeal cancer. There are, of course, possible differences between the

population and health care in Taiwan and the United States. For example, arsenic levels in the

U.S. are not as high as they were in the study area of Taiwan. However, the study gives an

indication of the types of health effects that may be associated with arsenic exposure via drinking

water.

Arsenic interferes with a number of essential physiological activities, including the actions of

enzymes, essential cations, and transcriptional events in cells (NRC, 1999). A wide variety of

adverse health effects have been associated with chronic ingestion of arsenic in drinking water,

occurring at various exposure levels. Exhibit 5-1 lists the effects on specific organ systems

reported in humans exposed to arsenic and provides descriptive information on the specific

diseases and/or symptoms associated with categories of diseases.

1.3. Regulatory Alternatives Considered

In regulating a contaminant, EPA first sets a maximum contaminant level goal (MCLG), which

establishes the contaminant level at which no known or anticipated adverse health effects occur. 

MCLGs are non-enforceable health goals. For this rulemaking, EPA is proposing an MCLG of

zero. EPA then sets an enforceable maximum contaminant level (MCL) as close as technologically

possible to the MCLG. In addition, EPA may use its discretion in setting the MCL by choosing

an MCL that is protective of public health while also insuring that the quantified and nonquantified costs are justified by the quantified and non-quantified benefits of the rule. For this

rulemaking, EPA is proposing an MCL of 5 μg/L. Chapter 3 describes the process by which EPA

determined both the MCLG and the MCL.
Chapter 1, Executive Summary 1-3 Proposed Arsenic in Drinking Water Rule RIA

EPA considered a range of MCLs in developing the proposed Arsenic Rule, including MCLs of 3,

5, 10, and 20 μg/L. EPA evaluated the following five factors to determine the proposed

Maximum Contaminant Level (MCL): 

• the analytical capability and laboratory capacity, 

• likelihood of water systems choosing various compliance technologies for several

sizes of systems based on source water properties, 

• the national occurrence of arsenic in water supplies. 

• quantified and non-quantified costs and health risk reduction benefits likely to

occur at the MCLs considered, and 

• the effects on sensitive subpopulations.

After evaluating the above factors, EPA considered an MCL of 3 μg/L since this is the level that

has been determined to be as close to the MCLG as is feasible. However, the Agency is using its

discretionary authority in Section 1412(b)(6)(A) to consider setting MCL at a less stringent level. 

The statute requires that the alternative less stringent level be one which maximizes health risk

reduction at a level where costs and benefits are balanced. As a result, EPA considered the

alternative MCL options of 5, 10, and 20 μg/L. These alternative MCL options were considered

because they also provide assurance that the residual risk for both bladder and lung cancer

endpoints will be in the 10-4 range, but at lower anticipated national costs.

The Agency also considered two regulatory options related to the applicability of the proposed

MCL. Specifically, EPA investigated applying both the monitoring and treatment requirements of

the proposed rule to both community water systems (CWS) and non-transient non-community

water systems (NTNC). A CWS is defined as a system that provides piped water to at least 25

people or with at least 15 service connections year-round. A NTNC is a public water systems

that is not defined as a CWS and that regularly serves at least 25 of the same people for at least

six months of the year. After considering the costs and benefits of the proposed rule with regard

to both CWSs and NTNCs, EPA proposes to require CWS to comply with all facets of the

proposed rule, while only requiring NTNCs to comply with the monitoring components of the

rule. The benefit-cost analysis upon which this decision is based is provided in Chapters Five, Six,

and Seven of this RIA. Transient non-community systems, which provide potable water to

continuously changing populations, will not be subject to the proposed rule. 

The proposed rule also includes modifications to the current monitoring requirements, including

the availability of monitoring waivers. A detailed discussion of these changes can be found in

Chapter 3. 

1.4 Benefits and Costs of the Proposed Rule

Quantitative risk metrics (e.g., slope factors or reference doses) are necessary to evaluate cancer

or non-cancer risks. Although arsenic causes numerous health effects, bladder cancer is the only

endpoint for which an Agency-approved metric for evaluating arsenic related risk currently exists. 
1

If “X” is the probability of contracting bladder cancer, then 0.26X is the probability of mortality from

bladder cancer. If lung cancer deaths are 2 to 5 times as high as bladder cancer, then they are, on average, 3.5

times as high and the average probability of mortality from lung cancer would be 3.5 times 0.26X, or 0.91X. Since

we also know that there is a 88% mortality rate from lung cancer, then if the probability of contracting lung cancer

is “Y,” the probability of mortality from lung cancer can also be represented as 0.88Y. Setting the two ways of

deriving the probability of mortality from lung cancer equal, or 0.91X = 0.88Y, one can solve for Y 

(Y= (0.91/0.88) X). Thus Y is approximately equal to X, and the rate of contracting lung cancer is approximately

the same as the rate of contracting bladder cancer.

Chapter 1, Executive Summary 1-4 Proposed Arsenic in Drinking Water Rule RIA

This cancer slope factor (SF) for bladder cancer is used to calculate cases potentially avoided due

to EPA’s proposed drinking water standards. Benefits estimates for avoided cases of bladder

cancer were calculated using mean population risk estimates at various MCL levels. Lifetime risk

estimates were converted to annual risk factors, and applied to the exposed population to

determine the number of cases avoided. These cases were divided into fatalities and non-fatal

cases avoided, based on survival information. The avoided premature fatalities were valued based

on the VSL estimates discussed earlier, as recommended by EPA current guidance for cost/benefit

analysis. The avoided non-fatal cases were valued based on the willingness to pay estimates for

the avoidance of chronic bronchitis. The upper bound estimates include the possibility of the

incidence rate being understated, depending on the survival rate for bladder cancer in the study

area of Taiwan during the Chen study.

The “What if?” scenario for lung cancer benefits was used to estimate benefits for avoided cases

of lung cancer. This scenario is based on the statement in the NRC report “Arsenic in Drinking

Water,” which states that “some studies have shown that excess lung cancer deaths attributed to

arsenic are 2-5 fold greater than the excess bladder cancer deaths (NRC, 1999, pg. 8).” Two-tofive fold greater would be 3.5 fold greater on average. Also in the U.S. the mortality rate from

bladder cancer is 26% and the mortality rate of lung cancer is 88%. This suggests that if the risk

of contracting lung cancer were identical to the risk of contracting bladder cancer, one would

expect 3.4 times the number of deaths from lung cancer as from bladder cancer. Since these

numbers are essentially the same, it seems reasonable to assume that the risk of contracting lung

cancer is essentially the same as the rate of contracting bladder cancer, 1 in the context of this

“what-if” scenario. If the risk of contracting lung cancer from arsenic in drinking water is

approximately equal to the risk of contracting bladder cancer, then the combined risk estimates of

contracting either bladder or lung cancer would be approximately double the risk estimates of

bladder cancer alone.

Numerous other health effects that are likely to be avoided as a result of this rule may generate

significant benefits, and should not be discounted based on the fact that they can’t be quantified at

this time. The estimated total national monetized benefits of the proposed rule and the other rule

options considered are provided in Exhibit 1-1.
Chapter 1, Executive Summary 1-5 Proposed Arsenic in Drinking Water Rule RIA

Exhibit 1-1

Estimated Monetized Total Cancer Health Benefits and

Non-Quantifiable Health Benefits from Reducing Arsenic in CWSs

Arsenic

Level 

(μg/L)

Annual

Bladder Cancer

Health Benefits

($millions)1,2

“What-if” Scenario and Potential Non-Quantifiable

Health Benefits

“What-if” Scenario

Annual

Lung Cancer

Health Benefits

($millions)1,3

Potential Non-Quantifiable

Health Benefits

3 $43.6 - $104.2 $47.2 - $448.0

• Skin Cancer

• Kidney Cancer

• Cancer of the Nasal Passages

• Liver Cancer

• Prostate Cancer

• Cardiovascular Effects

• Pulmonary Effects

• Immunological Effects

• Neurological Effects

• Endocrine Effects

• Reproductive and Developmental

Effects

5 $31.7 - $89.9 $35.0 - $384.0

10 $17.9 - $52.1 $19.6 - $224.0

20 $7.9 - $29.8 $8.8 - $128.0

1. May 1999 dollars.

2. The lower-end estimate is calculated using the lower-end number of bladder cancer cases avoided (see

Exhibit 5-12) and assumes that the conditional probability of mortality among the Taiwanese study group was

100 percent. The upper-end estimate is calculated using the upper-end number of cancer cases avoided (see

Exhibit 5-12) and assumes that the conditional probability of mortality among the Taiwanese study group was 80

percent.

3. These estimates are based on the “what if” scenario for lung cancer, where the risks of a fatal lung cancer

case associated with arsenic are assumed to be 2-5 times that of a fatal bladder cancer case.

For the proposed MCL of 5 μg/L, the estimated monetized bladder cancer health benefits range

from $31.7 million to $89.9 million. Potential lung cancer health benefits, based on the “What-if”

scenario, range from $35.0 million to $384.0 million. More detail about these benefit estimates

are found in Chapter 5. Exhibit 1-2 shows the estimated national cost of compliance of the

proposed rule and the other rule options that were considered. At the proposed MCL of 5 μg/L,

the estimated national cost of compliance is $379 million at a discount rate of 3 percent, and $442

million at a discount rate of 7 percent.
Discount Rate 3% 7% 3% 7% 3% 7%

System Costs

Treatment $639.2 $746.4 -- -- $639.2 $746.4

Monitoring/ 

Administrative

$2.2 $3.0 $0.9 $1.1 $3.1 $4.1

State Costs $1.6 $1.9 $0.6 $0.7 $2.2 $2.6

TOTAL COST $643.1 $751.4 $1.5 $1.8 $644.6 $753.2

System Costs

Treatment $374.0 $436.0 -- -- $374.0 $436.0

Monitoring/ 

Administrative

$2.0 $2.8 $0.9 $1.1 $2.9 $3.9

State Costs $1.3 $1.6 $0.6 $0.7 $2.0 $2.3

TOTAL COST $377.3 $440.4 $1.6 $1.8 $378.9 $442.2

System Costs

Treatment $160.4 $186.7 -- -- $160.4 $186.7

Monitoring/ 

Administrative

$1.8 $2.5 $1.0 $1.1 $2.8 $3.7

State Costs $1.1 $1.3 $0.6 $0.7 $1.7 $2.1

TOTAL COST $163.3 $190.5 $1.6 $1.9 $164.9 $192.4

System Costs

Treatment $58.9 $68.3 -- -- $58.9 $68.3

Monitoring/ 

Administrative

$1.7 $2.4 $1.0 $1.1 $2.7 $3.5

State Costs $1.0 $1.2 $0.7 $0.7 $1.6 $1.9

TOTAL COST $61.6 $71.8 $1.6 $1.9 $63.2 $73.7

*Costs include treatment, O&M, monitoring, and administrative costs to CWSs, monitoring and administrative costs to 

NTNCWSs, and State costs for administration of water programs.

MCL =20 μg/L

CWS

MCL = 3 μg/L

MCL =5 μg/L

MCL = 10 μg/L

NTNC* TOTAL

Exhibit 1-2

Total National Cost of Compliance ($ millions)
Chapter 1, Executive Summary 1-7 Proposed Arsenic in Drinking Water Rule RIA

3 5 10 20

Net Benefits $ (599.5) $ (345.6) $ (145.4) $ (53.7)

Benefit/Cost Ratio 0.07 0.08 0.11 0.13

Net Benefits $ (538.9) $ (287.4) $ (111.2) $ (31.8)

Benefit/Cost Ratio 0.16 0.24 0.32 0.48

Net Benefits $ (707.8) $ (408.7) $ (172.6) $ (63.9)

Benefit/Cost Ratio 0.06 0.07 0.09 0.11

Net Benefits $ (647.2) $ (350.5) $ (138.4) $ (42.0)

Benefit/Cost Ratio 0.14 0.20 0.27 0.42

*Costs include treatment, O&M, monitoring, and administrative costs to CWSs, monitoring and 

administrative costs to NTNCWSs, and State costs for administration of water programs.

The lower-end estimate of bladder cancer cases avoided is calculated using the lower-end risk estimate 

(see Exhibit 5-9) and assumes that the conditional probability of mortality among the Taiwanese study group 

was 100 percent. The upper-end estimate of bladder cancer cases is calculated using the upper-end risk 

estimate (see Exhibit 5-9) and assumes that the conditional probability of mortality among the Taiwanese 

study group was 80 percent. upper bound lower bound upper bound

7% Discount Rate

MCL (μg/L)

3% Discount Rate

lower bound

Exhibit 1-3

Net Benefits and Benefit-Cost Ratios of Each Regulatory Option

(Bladder Cancer Cases Only, in $ millions)

The net benefits and benefit-cost ratios of each regulatory option are provided in Exhibit 1-3,

when only health benefits for bladder cancer cases avoided are quantified. At the proposed MCL

of 5 μg/L, the net benefits range from a high of -$287.4 million to a low of -$345.6 million, at a

discount rate of 3 percent. These net benefits correspond to benefit-cost ratio of 0.24 and 0.08

(also at a 3 percent rate of discount). At a 7 percent discount rate the net benefits range from a

high of -$350.5 million to a low of -$408.7 million. These net benefits correspond to benefit-cost

ratio ranging from 0.20 to 0.07 (also at a seven percent rate of discount).
Chapter 1, Executive Summary 1-8 Proposed Arsenic in Drinking Water Rule RIA

As mentioned above, there are a number of important non-monetized benefits of reducing arsenic

exposure that are not include in the net benefit and benefit-cost calculations. Chief among these

are certain health impacts known to be caused by arsenic (such as skin cancer). In 1988 EPA

published a risk estimate which used the skin cancer data from Taiwan. EPA calculated a

Maximum Likelihood Estimate (MLE) for skin cancer of 3 x 10-5 for females and 7 x 10-5 for

males drinking 2 liters a day contaminated with 1 μg/L of arsenic. At the current MCL of 50

μg/L and two liters per day, the risk would be 5x10-3. A number of epidemiologic studies

conducted in several countries (e.g., Taiwan, Japan, England, Hungary, Mexico, Chile, and

Argentina) report an association between arsenic in drinking water and skin cancer in exposed

populations. Studies conducted in the U.S. have not demonstrated an association between

inorganic arsenic in drinking water and skin cancer. However, these studies may not have

included enough people in their design to detect these types of effects. 

The potential monetized benefits associated with skin cancer reduction would not change the total

benefits of the rule to an appreciable degree, even if the assumption were made that the risk of

skin cancer were equivalent to that of bladder cancer, using EPA’s 1988 risk assessment. Skin

cancer is highly treatable (at a cost of illness of less than $3,500 for basal and squamous cell

carcinomas vs. a cost-of-illness of $178,000 for non-fatal bronchitis) in the U.S., with few

fatalities (less than one percent). 

In addition to potentially reducing the risk of skin and lung cancer, there are also a large number

of other health effects associated with arsenic, as presented in Exhibit 1-1, which are not

monetized in this analysis, due to lack of appropriate data. 

Other benefits not monetized in this analysis include customer peace of mind from knowing

drinking water has been treated for arsenic and reduced treatment costs for currently unregulated

contaminants that may be co-treated with arsenic. To the extent that reverse osmosis is used for

arsenic removal, these benefits could be substantial. Reverse osmosis is the primary point of use

treatment, and it is expected that very small systems will use this treatment to a significant extent. 

(These benefits of avoided treatment cannot currently be monetized; however, they can be readily

monetized in the future, as decisions are made about which currently unregulated contaminants to

regulate.)
Chapter 2, Need for the Proposal 2-1 Proposed Arsenic in Drinking Water Rule RIA

Chapter 2: Need for the Proposal

2.1 Introduction

The Safe Drinking Water Act (SDWA), as amended in 1996, requires the EPA to identify and

regulate substances in drinking water that may have an adverse effect on public health and that are

known or anticipated to occur in public water supplies. National Primary Drinking Water

Regulations (NPDWRs) address risks to public health, and secondary regulations address

aesthetic qualities (such as taste, odor, or color) that relate to public acceptance of drinking

water. For NPDWRs, EPA must either establish a Maximum Contaminant Level (MCL) or, if it is

not economically or technically feasible to monitor the contaminant in drinking water, specify a

treatment technique to remove the contaminant or reduce its concentration in the water supply. 

An enforceable standard of 50 μg/L currently exists for arsenic in community water systems under

the National Interim Primary Drinking Water Regulations (40 CFR 59566). In §1412(b)(12)(A)

of the SDWA, as amended in 1996, Congress specifically directed EPA to propose a NPDWR for

arsenic by January 1, 2000 and issue the final regulation by January 1, 2001. At the same time,

Congress directed EPA to develop a research plan to reduce the uncertainty in assessing health

risks from low levels of arsenic by February 2, 1997 and conduct the research in consultation with

the National Academy of Sciences, other Federal agencies, and interested public and private

entities.

This document analyzes the impacts of the proposed rule which revises the current standard as

follows:

1) reduces the current MCL for arsenic in community water systems from 50 μg/L to 5 μg/L;

2) requires nontransient non-community water systems (NTNC) to perform compliance 

monitoring; and 

3) revises the current monitoring requirements to make them consistent with the Standard

Monitoring Framework (40 CFR 141.23(c)).

Executive Order 12866, Regulatory Planning And Review, requires EPA to estimate the costs

and benefits of the Arsenic Rule in a regulatory impact analysis (RIA). This chapter of the RIA

discusses the public health concerns being addressed by the rule, describes the history of

regulatory efforts concerning arsenic, and discusses the economic rationale for the rule.

Subsequent chapters will accomplish the following:

• discuss the regulatory options considered by EPA (Chapter 3), 

• present the results of the baseline analysis (Chapter 4), 

• examine the benefits of the proposed rule (Chapter 5), 

• present the results of the cost analysis (Chapter 6),

• compare the costs and benefits of the proposed rule and the regulatory options

considered by EPA (Chapter 7), and

• discuss the potential economic impacts of the rule (Chapter 8).
Chapter 2, Need for the Proposal 2-2 Proposed Arsenic in Drinking Water Rule RIA

2.2 Public Health Concerns to be Addressed

This section describes the public health concerns addressed by the proposed Arsenic Rule. A

description of potential health effects associated with arsenic, including effects in sensitive

subpopulations, along with the sources of human exposure to arsenic is presented. In addition,

the section describes current controls that address exposure to arsenic.

2.2.1 Health Effects of Arsenic

Arsenic is a naturally occurring element present in the environment in both organic and inorganic

forms. Inorganic arsenic, the more toxic form, is found in ground water, surface water and many

foods. Chronic exposure to arsenic has been found to result in a variety of adverse health effects,

including skin and internal cancers and cardiovascular and neurological effects. The available

evidence on the health effects of arsenic has recently been reviewed in a report by the National

Research Council (NRC) of the National Academy of Sciences (NAS). The health effects of

inorganic arsenic are summarized here and are described in more detail in Chapter 5. 

Exposures to organic forms of arsenic also occur through ingestion of food and metabolism of

ingested inorganic arsenic. Experimental data on the effects of organic forms of arsenic are not as

well characterized as those for inorganic arsenic, and thus are the subject for future research.

Limited data in animals suggest that some organic forms of arsenic also produce cancer and

non-cancer health effects.

Cancer

EPA has identified arsenic as a group A “known” human carcinogen, based on increased risks of

lung cancer in workers exposed to airborne arsenic and dose-dependent increases in skin cancer

risk in Taiwan. Using data from Taiwan, EPA calculated a Maximum Likelihood Estimate (MLE)

of 3 x 10-5 for females and 7 x 10-5 for males drinking 2 liters a day contaminated with 1 μg/L of

arsenic. The values were combined to give an overall risk of 5 x 10-5 /(μg/L) or 2 μg/L = 1 x 10 -4

risk level. The International Agency for Research on Cancer (IARC) has also classified arsenic as

a human carcinogen. Epidemiological studies have shown evidence of carcinogenic risk by both

inhalation and ingestion.

Unlike most environmental contaminants, there is a large human database available for inorganic

arsenic. However, there is substantial debate among the scientific community over the

interpretation of these data and their application in risk assessment. A number of epidemiologic

studies conducted in several countries (e.g., Taiwan, Japan, England, Hungary, Mexico, Chile,

and Argentina) report an association between arsenic in drinking water and skin cancer in exposed

populations. Increased mortality from internal cancers of liver, bladder, kidney, and lung have

also been reported. 

In 1996, EPA requested that the National Research Council (NRC) of NAS conduct an

independent review of the arsenic toxicity data. NRC was asked to review EPA’s current criteria

(50 μg/L and 0.018 μg/L), evaluate use of recent Taiwan data and other studies to assess the

carcinogenic and non-carcinogenic health effects of arsenic, and recommend changes to EPA’s

risk characterization for arsenic. NRC issued its report on March 23, 1999. A summary of the
Chapter 2, Need for the Proposal 2-3 Proposed Arsenic in Drinking Water Rule RIA

NRC’s results are provided below.

Non-Cancer Health Effects

In addition to cancer, arsenic exposures have been reported to result in other adverse health

effects. These include thickening of the skin, effects on the nervous system such as tingling and

loss of feeling in limbs, hearing impairment, effects on the heart and circulatory system, diabetes,

developmental effects, and effects on the gastrointestinal system and liver. Many of these effects

are observed at concentrations where cancer effects were observed in the epidemiology studies.

Sensitive Subpopulations

Certain sensitive individuals may be at a greater risk of serious illness from exposure to arsenic

than the general population. The NRC report noted that human sensitivity to the toxic effects of

inorganic arsenic exposure is likely to vary based on genetics, metabolism, diet, health status, sex,

and other possible factors. For example, reduced ability to methylate arsenic (converting

inorganic arsenic into less acutely toxic and more readily excreted forms) may result in retention

of more arsenic in the body and increased risk of toxic effects. 

The following groups are cited in various studies as being particularly susceptible to arsenic:

• Children are identified as especially susceptible to health effects from arsenic

because their dose of arsenic will be, on average, higher than that of adults

exposed to similar concentrations due to their higher fluid and food intake relative

to body weight. The NRC report cited one study that suggests that children may

have a lower arsenic-methylation efficiency than adults.

• Pregnant and lactating women are especially vulnerable because of the adverse

reproductive and developmental effects of arsenic. 

• People with poor nutritional status may have a reduced ability to methylate

arsenic.

• Individuals with pre-existing diseases that affect specific organs – in

particular, kidney and liver problems – may be more susceptible to the effects of

arsenic, because these organs act to detoxify arsenic in the body. In addition,

arsenic can directly damage these and other organ systems, as described above. 

Individuals with pre-existing damage or congenital defects in these systems are

more susceptible to health effects from exposure to arsenic. The elderly are more

likely as a group to have pre-existing conditions in the susceptible organ systems. 

Section 5.2.4 discusses the susceptibility of these subgroups in more detail. Due to a lack of

available data, no quantitative analysis of the specific risks to sensitive populations was performed

as part of this RIA.
Chapter 2, Need for the Proposal 2-4 Proposed Arsenic in Drinking Water Rule RIA

2.2.2 Sources and Mechanisms of Exposure

Arsenic is an element that occurs in the earth's crust. Accordingly, there are natural sources of

exposure. Erosion and weathering of rocks deposit arsenic in water bodies and lead to the uptake

of arsenic by animals and plants. Consumption of food and water are the major sources of arsenic

exposure for the majority of U.S. citizens. People may also be exposed from industrial sources, as

arsenic is used in semiconductor manufacturing, petroleum refining, wood preservatives, animal

feed additives and herbicides. 

Arsenic can combine with other elements to form inorganic and organic arsenicals. In general,

inorganic derivatives are regarded as more toxic than the organic forms. While food contains both

inorganic and organic arsenicals, primarily inorganic forms are present in water.

Recently, EPA developed estimates of human exposure to arsenic in drinking water, food, and air

using data from numerous Federal sampling surveys analyzing the occurrence of arsenic in public

water supplies, dietary foods, and ambient air. EPA's national air sampling data bases indicate

very low concentrations of arsenic in both urban and non-urban locations, at levels typically

ranging from about 0.003-0.03 μg/m3. Air is therefore an insignificant source of arsenic intake,

representing typically less than one percent of overall exposure.

EPA reviewed several local and regional studies for comparison purposes. Using the Food and

Drug Administration's (FDA) Total Diet Study, recent dietary analyses indicate that the average

adult's total arsenic intake is about 53 μg/day. However, the FDA analytical methodology does

not differentiate between the organic and inorganic forms of arsenic. For most people living in the

U.S., inorganic arsenic exposure is primarily from food and water sources. Since the inorganic

forms are considered to be more toxic, it is important to estimate the amount of inorganic arsenic

in the diet. To accomplish this estimation, EPA used the FDA data along with a separate study

that characterized arsenic species in foods. This separate characterization indicated that about 20

percent of daily intake of dietary arsenic is in the inorganic form. Conversely, most arsenic

present in drinking water is in the form of inorganic arsenic species.

Accounting for the organic forms of arsenic in food, the dietary intake of inorganic arsenic was

estimated to be approximately 14 μg/day. An adult drinking 2 L/day of water containing 10 μg/L

of arsenic, would obtain 20 μg/day from drinking water, so that drinking water would contribute

about 60 percent of total intake of inorganic arsenic. On the other hand, an adult drinking water

containing 2 μg/L of arsenic would obtain almost 80 percent of the daily inorganic arsenic from

food. 

2.3 Regulatory History

This section provides a chronology and overview of regulatory actions affecting arsenic in

drinking water and recent efforts that have led to this proposed rule-making. The major studies

and data collection efforts that have highlighted the need for new regulation are also summarized.

Current MCL: In 1975, EPA set the National Interim Primary Drinking Water Regulation at 50
Chapter 2, Need for the Proposal 2-5 Proposed Arsenic in Drinking Water Rule RIA

Fg/L (40 FR 59566 December 24, 1975.) This standard was equal to the standard set in 1943 by

the U.S. Public Health Service (US PHS) for interstate water carriers which was not based on a

risk assessment. The MCL was based on EPA's assertion that daily consumption of two liters of

water provides approximately 10 percent of total ingested arsenic of 900 μg/day. Commenters

recommended an MCL of 100 μg/L based on no observed adverse health effects. EPA noted

long-term chronic effects at 300 to 2,750 μg/L, but no chronic effects at 120 μg/L (NIPDWRs,

EPA-570/9-76-003).

Water Quality Criteria: In 1980, EPA announced the availability of Water Quality Criteria

Documents to protect surface water bodies of water from pollutants under the Clean Water Act

(45 FR 79318, November 28, 1980). These criteria are used as guidance to the States in

establishing surface water quality standards and discharge limits for effluents. The criteria for

protection of human health from ingestion of arsenic in contaminated water and aquatic organisms

was 2.2 mg/L, or 0.0022 μg/L. In 1992, the Clean Water Act criteria were recalculated with

updated cancer slope factor data to yield 0.018 μg/L for arsenic (57 FR 60848, December 22,

1992.). 

1985 Proposed MCL: In an Advanced Notice of Proposed Rulemaking (ANPR) published

October 5, 1983 (48 FR 45502), EPA requested comment on whether the arsenic MCL should

consider carcinogenicity, other health effects, and nutritional requirements; and whether MCLs

are necessary for separate valence states. In 1985, EPA then proposed a non-enforceable

Maximum Contaminant Level Goal (MCLG) of 50 μg/L based on a NAS conclusion that 50 μg/L

balanced toxicity and possible essentiality. EPA also requested comment on alternate MCLGs of

100 μg/L based on non-carcinogenic effects and 0 μg/L based on carcinogenicity (50 FR 46936,

November 13, 1985). 

1986 SWDA Amendments: The 1986 SDWA Amendments converted the 1975 interim arsenic

standard to a NPDWR, subject to revision by 1989. 

1988 Risk Assessment Forum Report: EPA's Risk Assessment Forum wrote the Special Report

on Ingested Inorganic Arsenic: Skin Cancer; Nutritional Essentiality (EPA/625/3-87/013), in part,

to evaluate the validity of applying the Taiwan 1968/1977 data to dose-response assessments in

the U.S. At the 50 μg/L standard, the calculated U.S. lifetime risk ranged from 

1 x 10-3 to 3 x 10-3. 

1989: After reviewing EPA's arsenic health effects studies in June 1988, the Science Advisory

Board (SAB) stated in its August 14, 1989, report the following:

• The essentiality of arsenic is suggestive but not definitive;

• Hyperkeratosis may not be a precursor of skin cancer;

• The Taiwan data are adequate to conclude that high doses of ingested arsenic can

cause skin cancer;

• The Taiwan study is inconclusive to determine cancer risk at levels ingested in the

U.S.; and 

• As (III) levels below 200 to 250 μg per day may be detoxified. 

SAB concluded that the dose-response is nonlinear and reported that the 1988 Forum Report did

not apply nonlinearity in its risk assessment. 
1

The Arsenic Research Plan is published at http://www.epa.gov/ORD/WebPubs/final/arsenic.pdf.

Chapter 2, Need for the Proposal 2-6 Proposed Arsenic in Drinking Water Rule RIA

1989: Uncertainty about arsenic risk assessment issues caused the Agency to miss the 1989

deadline for proposing a revised NPDWR, and a citizen suit was filed against EPA. A consent

decree was entered by the court in June, 1990, and was amended several times thereafter before

being dismissed after passage of the 1996 SDWA Amendments.

1994: EPA thoroughly reviewed the available information and determined that: 

• There is evidence of an association between internal cancer and arsenic;

• The risk of internal cancer cannot be quantified using the available epidemiological

data; and 

• The risk assessment will be based on the existing quantified skin cancer risk with a

hazard identification for internal cancer. 

The Safe Drinking Water Act Amendments of 1996, in Section 1412(b)(12)(A) pertaining to

arsenic, directed EPA to take the following actions: 

• Develop an arsenic research strategy within 180 days of enactment; 

• Propose a revised MCL by January 1, 2000; 

• Issue a final regulation by January 1, 2001;

• Assess health effects for sensitive populations;

• List both compliance and variance treatment technologies for small systems;

• Evaluate the incremental costs and benefits of different regulatory options,

accounting for the changes that may result from implementation of other rules;

• Issue an MCL that maximizes health benefits at a cost that is justified by the

benefits; 

• Review MCLs every six years or sooner.

The 1996 amendments also made the following changes:

• The effective date of MCLs is three-to-five years after promulgation of the final

rule. 

• Compliance can be achieved by use of point-of-use (POU) or point-of-entry (POE)

devices that are maintained by the public water system; 

Congress authorized $2.5 million per year from 1997-2000 for the studies. In 1996 and 1997,

Congress appropriated $1 million each year for arsenic research.

EPA is proposing this rule to meet the deadlines specified in the 1996 Amendments. At the same

time, EPA is proceeding with its Arsenic Research Plan, which will address a variety of issues

related to exposure, treatment, and health effects.1

NRC Report: As mentioned above, In 1996, EPA requested that the National Research Council

(NRC) of NAS conduct an independent review of the arsenic toxicity data and evaluate the

scientific validity of EPA’s 1988 risk assessment for arsenic in drinking water. In addition, NRC

was asked to review EPA’s current criteria (50 μg/L and 0.018 μg/L), evaluate use of recent

Taiwan data and other studies to assess the carcinogenic and non-carcinogenic health effects of

arsenic, and recommend changes to EPA’s risk characterization for arsenic. NRC issued its
2

The NRC report is available at http://www.nap.edu/readingroom/enter2.cgi?0309063337.html

Chapter 2, Need for the Proposal 2-7 Proposed Arsenic in Drinking Water Rule RIA

report on March 23, 1999. The report had four conclusions:

• The Taiwan studies provide the best available evidence on the human health effects

of arsenic, and are supported by studies in Chile and Argentina which report

similar results. These studies show that chronic ingestion of inorganic arsenic at

high doses causes bladder and lung cancer, as well as skin cancer.

• Noncancer effects from chronic ingestion of arsenic have been detected at doses of

0.01 mg/kg per day and higher. 

• There is a need for more research to characterize the dose-response relationship

for both cancer and non-cancer endpoints, especially at low doses.

• The current 50 μg/L MCL is not adequately protective of human health, and

therefore requires downward revision as promptly as possible.2

2.4 Rationale for the Regulation

This section discusses the economic rationale for choosing a regulatory approach to address the

public health consequences of drinking water contamination. EPA proves the economic rationale

in response to Executive Order Number 12866, Regulatory Planning and Review, which states:

[E]ach agency shall identify the problem that it intends to address (including, where

applicable, the failures of the private markets or public institutions that warrant new

agency action) as well as assess the significance of that problem (Section 1, b(1)).

In addition, OMB guidance dated January 11, 1996, states that “in order to establish the need for

the proposed action, the analysis should discuss whether the problem constitutes a significant

market failure” (p.3). Therefore, the economic rationale presented in this section should not be

interpreted as the agency’s approach to implementing the Safe Drinking Water Act (SDWA). 

Instead, it is the agency’s justification, as required by the Executive Order, for a regulatory

approach to this public health issue.

2.4.1 Statutory Authority 

Section 1412(b)(1)(A) of the Safe Drinking Water Act requires EPA to establish National Primary

Drinking Water Regulations for contaminants that may have an adverse public health effect, that

are known to occur, or present a substantial likelihood of occurring once in public water systems

(PWSs), at a frequency and level of public health concern and that present a meaningful

opportunity for health risk reduction for persons served by PWSs. This general provision is

supplemented with an additional requirement under Section 1412(b)(12)(A) that EPA propose a

revised MCL for arsenic by January 1, 2000, and issue a final regulation by January 1, 2001. 
3Mansfield (1975) states that natural monopolies exists because the average cost of producing the product

reaches a minimum at an output rate that is enough to satisfy the entire market at a price that is profitable.

Multiple producers competing would produce the product at higher than minimum long-run average cost. 

competition to achieve lower average costs would drive prices down until a single supplier is victorious.

Chapter 2, Need for the Proposal 2-8 Proposed Arsenic in Drinking Water Rule RIA

2.4.2 Economic Rationale for Regulation

In addition to the statutory directive to regulate arsenic, there is also economic rationale for

government regulation. In a perfectly competitive market, market forces guide buyers and sellers

to attain the best possible social outcome. A perfectly competitive market occurs when there are

many producers of a product selling to many buyers, and both producers and buyers have

complete knowledge regarding the products of each firm. There must also be no barriers to entry

in the industry, and producers in the industry must not have any advantage over potential new

producers. Several factors in the public water supply industry do not satisfy the requirements for

a perfect market and lead to market failures that may require regulation.

First, water utilities are natural monopolies. A natural monopoly exists because it is not

economically efficient to have multiple suppliers competing to build multiple systems of pipelines,

reservoirs, wells, and other facilities.3 Instead, a single firm or government entity performs these

functions generally under public control. Under monopoly conditions, consumers are provided

only one level of service with respect to the quality of the product, in this case drinking water

quality. If consumers do not believe the margin of safety in public health protection is adequate,

they cannot simply switch to another water utility or perceived higher quality source of supply

(e.g., bottled water) without incurring additional cost.

Second, there are high information and transaction costs that impede public understanding of the

health and safety issues concerning drinking water quality. The type of health risks potentially

posed by trace quantities of drinking water contaminants involve analysis and distillation of

complex toxicological data and health sciences. EPA recently developed the Consumer

Confidence Report rule to make water quality information more easily available to consumers. 

The Consumer Confidence Report rule requires community water systems to mail their customers

an annual report on local drinking water quality. However, consumers will still have to analyze

this information for its health risk implications. Even if informed consumers are able to engage

utilities regarding these health issues, the costs of such engagement, known as “transaction costs,”

(in this case measured in personal time and commitment) present another significant impediment

to consumer expression of risk preference.

SDWA regulations are intended to provide a level of protection from exposure to drinking water

contaminants that would not otherwise occur in the existing market environment of public water

supply. The regulations set minimum performance requirements for all public water supplies in

order to reduce the risk confronted by all consumers from exposure to drinking water

contaminants. SDWA regulations are not intended to restructure market mechanisms or to

establish competition in supply. Rather, SDWA standards establish the level of service to be 
Chapter 2, Need for the Proposal 2-9 Proposed Arsenic in Drinking Water Rule RIA

provided in order to better reflect public preference for safety. The Federal regulations remove

the high information and transaction costs by acting on behalf of all consumers in balancing the

risk reduction and the social costs of achieving this reduction.
Chapter 2, Need for the Proposal 2-10 Proposed Arsenic in Drinking Water Rule RIA
Chapter 3, Consideration of Regulatory Alternatives 3-1 Proposed Arsenic in Drinking Water Rule RIA

Chapter 3: Consideration of Regulatory Alternatives

3.1 Regulatory Approaches

The Safe Drinking Water Act (SDWA) establishes EPA’s responsibility for ensuring the quality of

drinking water, and defines the mechanisms available to the Agency to protect public health. 

Specifically, the SDWA requires EPA to set enforceable MCLs when technically or economically

feasible or otherwise establish treatment technique requirements for specific contaminants in

drinking water. In meeting this mandate, EPA sets water quality standards by identifying which

contaminants should be regulated and establishing the levels of the contaminant water systems

must attain. This section discusses the approach EPA used in determining the regulatory

alternatives that have been considered.

3.1.1 Determining the Standard

In regulating a contaminant, EPA first sets a maximum contaminant level goal (MCLG), which

establishes the contaminant level at which no known or anticipated adverse health effects occur. 

MCLGs are non-enforceable health goals. For this rulemaking, EPA is proposing an MCLG of

zero. EPA then sets an enforceable maximum contaminant level (MCL) as close as technologically

possible to the MCLG. In addition, EPA may use its discretion in setting the MCL by choosing

an MCL that is protective of public health while also insuring that the quantified and nonquantified costs are justified by the quantified and non-quantified benefits of the rule. For this

rulemaking, EPA is proposing an MCL of 5 μg/L. The following sections describe the process by

which EPA determined both the MCLG and the MCL.

3.1.2 Determining the MCLG

Carcinogens: For many years, Congress supported a goal of zero tolerance for carcinogens in

food and water, and that goal was incorporated into the SDWA of 1974. Under this policy,

contaminants that are classified as probable human carcinogens have had MCLGs set at zero. 

EPA's Office of Science and Technology (OST) (in the Office of Water) develops a cancer risk

range that quantifies the probability that a person will develop cancer during a lifetime of ingesting

water containing the regulated contaminant. Mathematical models have been used to calculate the

drinking water concentration that would lead to excess cancer risks of 10-5 to 10-6 from exposure

to the carcinogen.

Data used in risk estimates usually come from lifetime exposure studies in animals. To predict the

risk for humans, the oral doses used in animal studies are corrected for differences in animal and

human size and surface area.

In 1986, EPA published Guidelines for Carcinogen Risk Assessment in the Federal Register (51

FR 33992). At that time EPA's default assumptions included low-dose linearity to extrapolate the

cancer risk range, which assumes that carcinogenic effects do not exhibit a threshold and that

carcinogens pose risks to humans at any concentration. EPA proposed revised Guidelines for

Carcinogen Risk Assessment in 1996 (61 FR 17960).
Chapter 3, Consideration of Regulatory Alternatives 3-2 Proposed Arsenic in Drinking Water Rule RIA

Noncarcinogens: MCLGs for noncarcinogens are based on Reference Doses (RfDs) and their

Drinking Water Equivalent Levels (DWELs). 

The Reference Dose (RfD, formerly the Acceptable Daily Intake, or ADI), estimates the daily

amount of chemical a person, including sensitive humans, can ingest over a lifetime with little risk

of causing adverse health effects. RfDs are usually expressed in milligrams of chemical per

kilogram of body weight per day (mg/kg/day). Data from chronic (usually two years) or subchronic (usually 90 days) studies of humans or animals provide estimates of the No- or- LowestObserved-Adverse-Effect Level (NOAEL or LOAEL). The NOAEL (or LOAEL) is divided by a

total uncertainty factor (UF) of 1 to 10,000 to obtain the RfD. In the final National Primary

Drinking Water Regulations published on January 30, 1991 (56 FR 3532), EPA applies a UF of 1,

3, or 10 when a NOAEL from a human study is used to account for intraspecies variation and an

uncertainty factor of 100 to a human LOAEL to account for lack of a NOAEL and for species

variation. The UFs provide a margin for variations in species responses, data gaps, and less than

lifetime exposures. Scientific judgement is used to select the total UF factor for specific risk

assessments. 

The Drinking Water Equivalent Level (DWEL) is calculated by multiplying the RfD by an

assumed adult body weight of 70 kg (approx. 154 pounds) and dividing by an average adult water

consumption of 2 liters per day (L/day). The DWEL assumes that 100 percent of the exposure

comes from drinking water. The MCLG is then determined by multiplying the DWEL by the

percentage of the total daily exposure contributed by drinking water (relative source

contribution), set at 20% by default when adequate data are not available, but set between 20 and

80 percent when adequate data are available to estimate exposure. Based on the 1993 RfD (1993

Draft Criteria) for arsenic (0.3 μg/kg/day), the calculated DWEL would be 0.3 μg/kg/day times

70 kg divided by 2 L/day, or 10 μg/L. Due to the three-fold uncertainties noted in the IRIS file

on arsenic, the DWEL could be 3 to 30 μg/L. It should be noted that the toxicological studies

used to determine the effect level and the derivation of the RfD are different from the analysis

conducted in 1975. Additionally, the current policy on relative source contribution, including the

default policy are also different from those used in 1975. 

3.1.3 Determining an MCL

Once an MCLG is established, EPA sets an enforceable standard – in most cases, a Maximum

Contaminant Level (MCL). The MCL is the maximum permissible level of a contaminant in water

that is delivered to any user of a public water system. EPA must set the MCL as close to the

MCLG as feasible. The SWDA defines feasible as the level that may be achieved with the use of

the best available technology, treatment techniques, and other means which EPA finds are

available (after examination for efficacy under field conditions), taking cost to large systems into

consideration. 

After determining an MCL based on affordable technology for large systems, EPA must complete

an economic analysis to determine whether the benefits of the standard justify the costs. If not,

EPA may adjust the MCL for a particular class or group of systems to a level that “maximizes

health risk reduction benefits at a cost that is justified by the benefits” (§1412(b)(6)). 

3.1.4 Variances and Exemptions
Chapter 3, Consideration of Regulatory Alternatives 3-3 Proposed Arsenic in Drinking Water Rule RIA

The 1996 SDWA identifies two classes of technologies for small systems: compliance and

variance technologies. A compliance technology is one that achieves compliance with the MCL

or treatment technique requirement. The 1996 Amendments require EPA to list affordable

compliance technologies for three categories of small systems: those serving 25 to 500 people,

those serving 501 to 3,300 people, and those serving 3,301 to 10,000 people. If EPA cannot

identify an affordable compliance technology for a particular system category, it must then

identify a variance technology instead. The variance technology must achieve the maximum

reduction that is affordable, considering the size of the system and the quality of the source water,

and must be protective of public health. If EPA lists such a variance technology, small systems

will be eligible to apply to the States for a small system variance. States are authorized to grant

variances from standards for systems serving up to 3,300 people if the system cannot afford to

comply with a rule and the system installs the EPA-approved variance technology. States can

grant exemptions to systems serving 3,301 - 10,000 people with EPA approval. 

The Agency published draft national-level affordability criteria in the August 6, 1998, Federal

Register (63 FR 42302). The draft criteria discuss affordable treatment technology

determinations for contaminants regulated before 1996. An average expenditure level of up to

$500 per year was considered affordable for those contaminants. Since EPA identified treatment

technologies for all pre-1996 contaminants with average per household costs below $500 per

year, the Agency did not list any small system variance technologies. 

EPA expects the national-level affordability criteria to be lower than $500 per household per year

for the arsenic rule because water rates are currently increasing faster than median household

income, and because the baseline for annual water bills will rise as treatment is installed to comply

with regulations promulgated after 1996. As part of this RIA, a household level cost analysis was

done to determine if EPA needs to list variance technologies (Chapters 6 and 8).

3.1.5 Analytic Methods

Determination of an MCL depends on the ability of laboratories to reliably measure the

contaminant at the MCL. The SDWA directs EPA to set an MCL “if in the judgement of the

Administrator, it is economically and technologically feasible to ascertain the level of such

contaminant in water in public water systems (Section 1401 (1)(c)(ii)).” EPA must therefore

evaluate the available analytical methods to determine a Practical Quantification Level (PQL),

which is the minimum reliable quantification level that most laboratories can be expected to meet

during day-to-day operations. 

EPA has approved several analytical methods to support compliance monitoring of arsenic at the

current MCL (40 CFR 141.23). In 1994, EPA evaluated available data and determined the PQL

for arsenic to be 2.0 μg/L at an acceptable limit of ± 40%. In its July 1995 report, EPA’s Science

Advisory Board recommended that EPA set the PQL for arsenic using acceptance limits similar to

those applied for other inorganics (± 20% or ± 30 %). Based on more recent information and

these acceptance limits, EPA has established a 1999 PQL for arsenic of 3 μg/L (EPA, MOM

1999) with an acceptance limit of ± 30 percent. While the PQL represents a stringent target for

laboratory performance, the Agency believes most laboratories, using appropriate quality

assurance and quality control procedures, have the capacity to achieve this level on a routine
Chapter 3, Consideration of Regulatory Alternatives 3-4 Proposed Arsenic in Drinking Water Rule RIA

basis. Available data suggest that 75 percent of EPA Regional and State laboratories and 62

percent of non-EPA laboratories were capable of achieving acceptable results at 3 μg/L. 

3.2 Regulatory Alternatives Considered and Proposed Rule

This section describes the components of the proposed rule and the alternatives that were

considered by the Agency. 

3.2.1 Applicability

The Agency investigated applying both the monitoring and treatment requirements of the

proposed rule to both community water systems (CWS) and non-transient non-community water

systems (NTNC). A CWS is defined as a system that provides piped water to at least 25 people or

with at least 15 service connections year-round. A NTNC is a public water systems that is not

defined as a CWS and that regularly serves at least 25 of the same people for at least six months

of the year. After considering the costs and benefits of the proposed rule with regard to both

CWSs and NTNCs, EPA proposes to require CWS to comply with all facets of the proposed rule,

while only requiring NTNCs to comply with the monitoring components of the rule. The benefitcost analysis upon which this decision is based is provided in Chapters Five, Six, and Seven of this

RIA. Transient non-community systems, which provide potable water to continuously changing

populations, will not be subject to the proposed rule. The rule applies to CWSs and NTNCs that

produce water from either primarily ground or surface water sources. 

3.2.2 MCL

EPA considered a range of MCLs in developing the proposed Arsenic Rule, including MCLs of 3,

5, 10, and 20 μg/L. EPA evaluated the following five factors to determine the proposed

Maximum Contaminant Level (MCL): 

• the analytical capability and laboratory capacity, 

• likelihood of water systems choosing various compliance technologies for several

sizes of systems based on source water properties, 

• the national occurrence of arsenic in water supplies. 

• quantified and non-quantified costs and health risk reduction benefits likely to

occur at the MCLs considered, and 

• the effects on sensitive subpopulations.

An MCL of 3 μg/L was considered since this is the level that has been determined to be as close

to the MCLG as is feasible. However, the Agency is using its discretionary authority in Section

1412(b)(6)(A) to consider setting MCL at a less stringent level. The statute requires that the

alternative less stringent level be one which maximizes health risk reduction at a level where costs

and benefits are balanced. As a result, EPA considered the alternative MCL options of 5, 10, and

20 μg/L. These alternative MCL options were considered because they also provide

assurance that the residual risk for both bladder and lung cancer endpoints will be in the 10-4

range, but at lower anticipated national costs.

3.2.3 Monitoring
Chapter 3, Consideration of Regulatory Alternatives 3-5 Proposed Arsenic in Drinking Water Rule RIA

The current monitoring requirements for arsenic (40 CFR 141.23(l)) apply to community water

systems only. EPA is proposing to change the current monitoring requirements and require

systems to monitor for arsenic in accordance with the provisions of 40 CFR 141.23(c), the

Standard Monitoring Framework (SMF). This change will make the arsenic requirements

consistent with the requirements for inorganic contaminants (IOCs) regulated under the Phase

II/V regulations. The proposal would make the following changes to the monitoring requirements

for arsenic:

• NTNC systems will be required to monitor for arsenic for the first time.

• MCL exceedances will trigger quarterly monitoring, as opposed to the current

requirements for three additional samples within one month when exceedances occur. 

• The State will determine when the system is “reliably and consistently” below the

MCL, after a minimum number of samples following an exceedance (two sample for

ground water systems and four for surface water systems), and can return to the

default sampling frequency. (Currently, the system automatically returns to the default

monitoring frequency when a minimum of two consecutive samples are below the

MCL).

• States may grant a nine year monitoring waiver to a system, if it finds that arsenic

detections are the result of natural occurrence and not from human activity. 

(Currently, no monitoring waivers are permitted).

3.2.4 Compliance Technologies and Variances

EPA reviewed several technologies as BAT candidates for arsenic removal. Those technologies

capable of removing arsenic from source water that fulfill the SDWA requirements for BAT

determinations for arsenic are as follows: 

• ion exchange; 

• activated alumina; 

• reverse osmosis ; 

• coagulation assisted microfiltration; 

• modified coagulation/filtration; 

• modified lime softening; 

• point-of-use RO/AA; point-of-entry AA ; and

• oxidation/filtration (including greensand filtration). 

EPA has further determined that these technologies are affordable for all system size categories

and has therefore not identified a variance technology for any system size or source water

combination at the proposed MCL. 

3.2.5 Monitoring Waivers

Under the proposed Arsenic Rule (§141.23(c)(3)), States may grant a nine year monitoring

waiver from sampling requirements to water systems based on the analytical results from previous

sampling and a vulnerability assessment or the assessment from an approved source water

assessment program (provided that the assessments were designed to collect all of the necessary

information needed to complete a vulnerability assessment for a waiver). States issuing waivers
Chapter 3, Consideration of Regulatory Alternatives 3-6 Proposed Arsenic in Drinking Water Rule RIA

must consider the requirements in 40 CFR 141.23(c)(2)-(6). In order to qualify for a waiver,

there must be three previous samples from a sampling point (annual for surface water and three

rounds for ground water) with analytical results reported below the proposed MCL (i.e., the

reporting limit must be < 0.005 mg/L). The use of grandfathered data collected after January 1,

1990, that is consistent with the analytical methodology and detection limits of the proposed

regulation may be used for issuing sampling point waivers.

The current arsenic regulations §141.23(l)-(q) do not permit the use of monitoring waivers. 

However, a State could now use the analytical results from the three previous compliance periods

(1993 to 1995, 1996 to1998, and 1999 to 2001) to issue ground water sampling point waivers. 

Surface water systems must collect annual samples so a State could use the previous three years

sampling data (1999, 2000, and 2001) to issue sampling point waivers. One sample must be

collected during the nine-year compliance cycle that the waiver is effective, and the waiver must

be renewed every nine years. Vulnerability assessments must be based on a determination that the

water system is not susceptible to contamination and arsenic is not a result of human activity (i.e.,

it is naturally occurring).

Although the approved analytical methods can measure to 0.005 mg/L, not all States have

required systems to report arsenic results below 50 μg/L. In this case, the States would not have

adequate data to grant waivers until enough data is available to make the determinations.

EPA believes that some States may have been regulating arsenic under the proposed standardized

inorganic framework. If so, those States will have to ensure that existing monitoring waivers

have been granted using data reported below the new proposed MCL. Otherwise States will have

to notify the systems of the new lower reporting requirements that need to be met to qualify for a

waiver for the proposed MCL. 

3.2.6 Implementation

The following schedule is proposed for implementation of the proposed rule:

• States must submit applications for primacy revisions within two years after

promulgation, unless the State requests and is granted a two year extension.

• The rule will be effective three years after promulgation (January 1, 2004).

• All systems must complete initial sampling by December 31, 2004.

• If capital improvements are needed to achieve compliance, systems may apply to the

State for a two year extension.

If EPA makes a national finding that capital improvements are necessary at the majority of

systems, then the rule will become effective five years after promulgation (January 1, 2006). In

this case, systems will have to complete the initial round of monitoring by December 31, 2007 (for

ground water systems), or December 31, 2006 (for surface water systems.)
Chapter 4, Baseline Analysis 4-1 Proposed Arsenic in Drinking Water Rule RIA

Chapter 4: Baseline Analysis

4.1 Introduction

This chapter presents baseline information to describe the operational and financial characteristics

of water systems in the absence of the proposed Arsenic Rule. The baseline information provides

a basis for EPA’s analysis of the costs, benefits and economic impacts of the regulatory options

considered. This chapter includes data on the number of water systems regulated, the population

affected, current treatment practices, raw and treated water quality, and socio-economic impacts. 

In addition, this chapter provides information to support the Agency’s national-level affordability

determination.

The baseline is assumed to be current conditions, as reflected in the most recent available data. In

some cases, changes in the industry have occurred or will occur that are not reflected in the

available data; for example, changes in operations induced by a regulation that will take effect

prior to the Arsenic Rule.

4.2 Industry Profile 

4.2.1 Definitions

According to EPA’s definition, public water systems (PWSs) include community water systems

(CWSs) and non-community water systems (NCWSs). NCWSs are further classified as either

transient or non-transient. The proposed rule will affect all public water systems except for

transient non-community water systems. The following definitions will help the reader follow the

discussion in this chapter:

• Public water systems (PWS) serve 25 or more people or has 15 or more service

connections and operates at least 60 days per year. A PWS can be publicly-owned or

privately-owned. 

• Community water systems (CWS) serve at least 15 service connections used by yearround residents, or regularly serve at least 25 year-round residents. 

• Non-community water systems (NCWS) do not have year-round residents, but serve at

least 15 service connections used by travelers or intermittent users for at least 60 days

each year, or serve an average of 25 individuals for at least 60 days a year.

• Non-transient non-community water systems (NTNC) serve at least 25 of the same

persons over six months per year (e.g., factories, schools, office buildings, and hospitals).

• Transient non-community water systems (TNC) serve fewer than 25 of the same

persons over six months per year (e.g., many restaurants, rest stops, parks).

Public water systems are also classified by their water source as being surface water (e.g., drawn

from lakes, streams, rivers, etc.) or ground water (e.g., drawn from wells or springs). 
Chapter 4, Baseline Analysis 4-2 Proposed Arsenic in Drinking Water Rule RIA

4.2.2 Sources of Industry Profile Data

EPA uses two primary sources of data to characterize the universe of ground water systems: the

Safe Drinking Water Information System (SDWIS) and the Community Water System Survey

(CWSS). 

EPA’s SDWIS contains data on all PWSs as reported by States and EPA regions. This source

reflects both mandatory and optional reporting components. States must report the system

location, system type (CWS, NTNC, or TNC), primary raw water source (ground water or

surface water), and violations. Optional reporting fields include type of treatment and ownership

type. Because providing some data is discretionary, EPA does not have complete data on every

system for these parameters. This is particularly common for non-community systems.

The second source of information, the CWSS, is a detailed survey of surface and ground water

CWSs conducted by EPA in 1995 and published in 1997 (EPA, 1997). The CWSS is stratified to

represent the complete population of CWSs across the U.S. The CWSS includes information

such as revenues, expenses, treatment practices, source water protection measures, and plant

capacity. There is no equivalent survey such as the CWSS to define treatment practices in noncommunity water systems.

4.2.3 Number and Size of Public Water Systems 

Exhibit 4-1 shows the number of systems in the U.S. by source water (ground or surface) and

system size (measured by the number of people served), based on the December 1998 SDWIS

data. In the U.S. there are a total of 63,984 ground water systems and 11,843 surface water

systems, including CWSs and NTNCs. All are potentially affected by the proposed Arsenic Rule.

Some ground water sources (e.g., riverbank infiltration/galleries) are directly impacted by adjacent

source water bodies and are separately identified in SDWIS as ground water under the direct

influence of surface water (GWUDI). Since these systems would have similar occurrence as

surface water systems, GWUDI systems are considered surface water systems in this analysis. 

SDWIS also provides system data by ownership. As previously described, PWSs include both

publicly-owned and privately-owned systems. This detail is also provided in Exhibit 4-1, where

any systems referred to as “other” in the SDWIS database has been presented as a privatelyowned system.

The majority (95%) of PWSs are small systems that serve fewer than 10,000 people. 89 percent

of PWSs serve 3,300 people or fewer; 77 percent serve fewer than 1,000 people; 67 percent serve

fewer than 500 people; and 34 percent serve fewer than 100 people.
Chapter 4, Baseline Analysis 4-3 Proposed Arsenic in Drinking Water Rule RIA

<100 101- 501- 1,001- 3,301- 10,001- 50,001- 100,001-

500 1,000 3,300 10,000 50,000 100,000 1,000,000

Ground Water

Public 1,335 4,678 2,868 4,167 1,993 1,011 105 50 16,207

Private 12,942 10,380 1,821 1,547 466 205 26 11 28,303

Total 14,277 15,058 4,689 5,714 2,459 1,216 131 61 44,510

Surface Water

Public 394 1,117 917 2,012 1,656 1,436 260 217 8,009

Private 698 886 303 408 188 171 40 44 3,053

Total 1,092 2,003 1,220 2,420 1,844 1,607 300 261 11,062

Total 15,369 17,061 5,909 8,134 4,303 2,823 431 322 54,352

Ground Water

Public 1,725 3,108 1,163 337 23 9 0 0 6,365

Private 7,965 3,930 815 355 39 5 0 0 13,109

Total 9,690 7,038 1,978 692 62 14 0 0 19,474

Surface Water

Public 58 63 19 24 6 3 1 1 175

Private 213 232 87 56 17 1 0 0 606

Total 271 295 106 80 23 4 1 1 781

Total 9,961 7,333 2,084 772 85 18 1 1 20,255

Source: Safe Drinking Water Information System (SDWIS), December 1998 freeze.

NTNCWS

SOURCE TOTAL

CWS

Exhibit 4-1

Total Number of Systems by Size, Type, and Ownership
Chapter 4, Baseline Analysis 4-4 Proposed Arsenic in Drinking Water Rule RIA

4.2.4 System Size and Population Served

All PWSs are potentially subject to the proposed requirements of the Arsenic Rule, with the

exception of TNCs. The majority of systems to be regulated are community water systems, which

also serve, on average, more people than NTNCs. Exhibit 4-2 provides information on the

average populations served by CWSs for each system size category. 

Exhibit 4–2

Total Population Served of Water Systems by

Source Water, System Type, and Service Population Category

Service

Population

Category

Community Non-Transient

Non-Community Ground water Surface Water

< 100 859,777 61,450 -

101–500 3,741,017 570,448 -

501–1,000 3,457,163 921,449 -

1,001–3,300 10,631,422 4,797,855 -

3,301–10,000 14,095,015 10,995,980 -

10,001–50,000 25,004,779 36,819,575 -

50,001–100,000 8,609,455 20,500,370 -

100,001-1,000,000 14,575,556 65,375,183 -

> 1,000,000 2,855,494 28,658,586 -

Total 83,829,678 168,700,896 31,968,181

Source: Safe Drinking Water Information System (SDWIS), December 1998 freeze.

Those NTNCs determined to be affected by the Arsenic Rule are presented in Exhibit 4-3 by type

of system. The NCWSs are much smaller than CWSs on average and vary substantially in their

characteristics. Schools account for more than half of the affected NCWSs (8,414 of 16,410),

followed by office parks (950), daycare centers (809) and food manufacturing facilities (768). 

Prisons serve the largest number of people on average (1,820). All other system types serve an

average of 500 people or fewer.
Chapter 4, Baseline Analysis 4-5 Proposed Arsenic in Drinking Water Rule RIA

Exhibit 4-3

Characteristics of NCWSs Affected by the Arsenic Rule

Service Area Type # of Systems Avg. Pop. Design Flow/System (mpd) Avg. Flow/System (mpd)

Daycare Centers 809 76 0.005114 0.001068

Highway Rest Areas 15 407 0.008895 0.001970

Hotels/Models 351 133 0.01892 0.004540

Interstate Carriers 287 123 0.002853 0.00056

Medical Facilities 367 393 0.116623 0.033945

Mobile Home Parks 104 185 0.026164 0.006498

Restaurants 418 370 0.003907 0.000793

Schools 8,414 358 0.033269 0.008476

Service Stations 53 230 0.00511 0.001067

Summer Camps 46 146 0.021758 0.005299

Water Wholesalers 266 173 0.163659 0.049381

Agricultural

Products/Services 368 76 0.019882 0.004796

Airparks 101 60 0.002608 0.000507

Construction 99 53 0.000914 0.000159

Churches 230 50 0.005287 0.001108

Campgrounds/RV Parks 123 160 0.021428 0.00521

Fire Departments 41 98 0.018623 0.004461

Federal Parks 20 39 0.006528 0.001399

Forest Service 107 42 0.001351 0.000245

Golf and Country Clubs 116 101 0.011796 0.002692

Landfills 78 44 0.005253 0.0011

Mining 119 113 0.012322 0.002825

Amusement Parks 159 418 0.017084 0.004055

Military Bases 95 395 0.069538 0.019159

Migrant Labor Camps 33 63 0.010212 0.002295

Misc. Recreation Services 259 87 0.002468 0.000477

Nursing Homes 130 107 0.04107 0.0107

Office Parks 950 136 0.00769 0.001677

Prisons 67 1,820 0.532196 0.182

Retailers (Non-food related) 695 174 0.003787 0.000766

Retailers (Food related) 142 322 0.005789 0.001225

State Parks 83 165 0.004828 0.001002

Non-Water Utilities 497 170 0.013288 0.003071

Manufacturing: Food 768 372 0.045384 0.01195

Manufacturing: Non-Food 0 0 0.015723 0.003785

Sum 16,410

Weighted Average 981 0.028 0.007

Source: EPA, 1999a. Geometries and Characteristics of Public Water Systems, Table 7.5 and Table 7.6.
Chapter 4, Baseline Analysis 4-6 Proposed Arsenic in Drinking Water Rule RIA

4.2.5 Number of Entry Points

If water systems employ more than one water supply source, they may have more than one

treatment facility. For estimation purposes this analysis assumes a treatment facility at every entry

point to the distribution system. As a result, the total number of entry points is an important

determinant of compliance costs. Exhibit 4–4 presents the distribution of entry points per ground

water CWS by system service population category. 

Exhibit 4-4

Average Number of Entry Points per Ground Water System

Upper Bound

95%

Confidence 

Service Population Category

< 100

101-

500

501-

1,000

1,001 -

3,300

3,301 -

10,000

10,001 -

50,000

50,001 -

100,000 > 100,000

Percentile

Mean 1 1 2 2 2 4 6 9

5th 1 1 1 1 1 1 1 1

50th (median) 1 1 1 1 2 3 4 5

95th 2 3 3 5 5 12 22 28

Source: EPA, 1999a. Geometries and Characteristics of Public Water Systems, Table 5.2.

In this respect, surface water systems are unlike ground water systems in that little variation in the

number of entry points was reported among surface water systems. Even for large population

categories, the majority of surface water systems reported only one or two entry points. (EPA,

1999a). This finding was supported by data recently collected from the Information Collection

Request for large surface water systems.

4.2.6 Number of Households

Another method for estimating the effect of regulations on customers is to determine the cost per

household. This measure is often used instead of per capita cost because it is a more accurate

representation of how customers are billed, per household, not per person. Exhibit 4-5 shows the

average number of connections for CWSs by size, water source, and ownership. The number of

connections, or households, ranges from an average of 30 residential service connections for

CWSs serving fewer than 100 people to an average of more than 56,000 residential connections

for CWSs serving more than 100,000 people (EPA, 1999b. Drinking Water Baseline Handbook,

B4.2.2(b)). 

Household consumption does not vary substantially across size category or ownership type. The

mean water consumption ranges from 81,000 gallons per year to 127,000 gallons per year per

household.
Chapter 4, Baseline Analysis 4-7 Proposed Arsenic in Drinking Water Rule RIA

Ground Surface

< 100 Public 81 46 24

Private 92 29 37

101-500 Public 93 128 192

Private 110 99 105

501-1,000 Public 97 314 315

Private 88 321 321

1,001-3,300 Public 82 663 774

Private 102 601 565

3,301-10,000 Public 87 2,130 2,304

Private 124 1,572 2,120

10,001-50,000 Public 108 6,075 6,737

Private 110 7,432 6,862

50,001-100,000 Public 122 20,278 19,427

Private 96 27,423 24,432

100,001-1,000,000 Public 127 59,969 69,985

Private 114 55,047 76,833

Source: *EPA, 1997. CWSS, Vol. II: Detailed Summary Result Tables and 

Methodology Report,Table 1-14; 

** EPA, 1995. CWSS: mean residential connections exclude purchased 

systems.

Connections per System 

by Source**

Mean Water 

Consumption* 

(kgal/yr)

System 

Type Population

Exhibit 4-5

Water Consumption per Residential Connection and

Number of Residential Connections per System

4.2.7 Production Profile

Exhibit 4-6 shows the average design capacity (in thousands of gallons) of CWS plants by source,

ownership, and system size categories. Design capacity is the maximum amount of water a plant

can deliver. Exhibit 4-7 provides the daily production of CWSs (in thousands of gallons) for the

same categories. Daily production is the average amount of water a plant delivers in a day.
Exhibit 4-6

Design Capacity of CWS Plants

by Source, Ownership, and System Size

(Thousands of Gallons)

Primary Source/

Ownership Type

Service Population Category

<25 25-100 101-500 501-1,000

1,001-

3,300

3,301-

10,000

10,001-

50,000

50,001-

100,000

100,001-

1,000,000 >1,000,000

Ground water 6.27 21.86 86.86 251.0 619.5 1864 6673 20785 67379 392939

Public 4.84 29.46 123.67 305.0 740.3 2152 7365 22614 67994 401175

Private 6.50 21.34 77.30 232.1 560.6 1683 6347 18234 75629 -

Purchased-Public - 5.71 27.37 81.4 223.0 801 3380 19796 26765 -

Purchased-Private 0.89 4.99 24.78 79.5 200.6 824 2748 8690 - -

Surface Water 1.30 20.32 92.60 239.3 617.9 1818 6682 19707 69224 554759

Public 1.14 25.79 130.90 318.2 807.8 2218 7887 22337 77298 584889

Private 3.19 18.13 75.69 214.2 527.3 1582 6165 15869 61381 296609

Purchased-Public 0.04 5.71 29.01 81.8 241.1 854 3698 13206 43650 -

Purchased-Private 1.12 4.99 24.65 73.6 213.8 719 2933 12788 29270 -

GW under

influence

- 22.16 87.20 247.5 631.6 1779 7499 18482 - -

Public - 33.29 111.32 291.2 760.0 2077 8992 20195 - -

Private - 21.53 81.77 227.4 618.5 1802 - - - -

Purchased-Public - - 30.21 97.1 209.3 461 2319 - - -

Purchased-Private - 2.54 29.83 94.3 - 905 - - - -

Source: Drinking Water Baseline Handbook, Table B1.5.3.
Exhibit 4-7

Daily Production of CWS Plants

by Source, Ownership, and System Size

(Thousands of Gallons)

Primary Source/

Ownership Type

Service Population Category

<25 25-100 101-500 501-1,000

1,001-

3,300

3,301-

10,000

10,001-

50,000

50,001-

100,000

100,001-

1,000,000 >1,000,000

Ground water 1.35 5.33 24.40 78.50 212 715 2,914 10,187 37,224 259,751

Public 0.96 6.72 33.20 90.50 243 796 3,129 10,900 37,095 267,256

Private 1.39 4.80 20.30 69.30 18 635 2,802 9,121 44,760 -

Purchased-Public - 5.11 23.50 68.20 182 634 2,585 14,496 19,455 -

Purchased-Private 0.85 4.54 21.60 67.30 166 656 2,119 6,502 - -

Surface Water 0.39 6.91 33.70 90.70 244 753 2,932 9,069 33,667 295,680

Public 0.28 7.51 41.60 106.20 284 823 3,133 9,387 34,749 293,439

Private 0.95 6.15 28.60 87.30 230 748 3,225 8,907 38,094 206,950

Purchased-Public 0.04 5.11 24.90 68.50 197 675 2,821 9,766 31,351 -

Purchased-Private 1.06 4.54 21.50 62.40 176 575 2,258 9,472 21,215 -

GW under

influence

- 5.41 24.50 77.30 217 679 3,313 8,951 - -

Public - 7.70 29.50 86.00 250 765 3,907 9,611 - -

Private - 4.85 21.30 67.70 207 686 - - - -

Purchased-Public - - 25.90 80.90 171 370 1,789 - - -

Purchased-Private - 2.36 25.9 79.4 - 719 - - - -

Source: EPA, 1999b. Drinking Water Baseline Handbook, Table B1.5.1.
Chapter 4, Baseline Analysis 4-10 Proposed Arsenic in Drinking Water Rule RIA.

4.2.8 Treatment Profile

Exhibit 4-8 below presents information regarding in-place treatment technologies that affect

arsenic concentrations in delivered water. The current treatment in place will determine the likely

remedy that systems will select in order to come into compliance with the new MCL.

Exhibit 4-8

Percentage of CWSs with Various Treatments In-Place

Primary

Source/ Type

of Treatments

Service Population Category

< 100 101-500 501-

1,000

1,001-

3,300

3,301-

10,000

10,001-

50,000

50,001-

100,000

100,001-

1,000,000 > 1,000,000

Ground Water Systems

Ion Exchange 0.7% 1.6% 3.8% 1.9% 4.6% 3.3% 1.2% 0.0% -

Reverse

Osmosis

0.0% 1.2% 0.0% 0.9% 1.2% 0.7% 1.2% 0.0% -

Coagulation/

Flocc.

1.5% 5.4% 4.2% 3.4% 8.1% 15.1% 24.2% 25.2% -

Lime/Soda Ash

Softening

2.1% 3.7% 4.1% 5.2% 7.0% 12.2% 17.4% 32.4% -

Surface Water Systems

Ion Exchange 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% -

Reverse

Osmosis

0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% -

Coagulation/

Flocc.

27.5% 52.6% 70.2% 78.5% 95.4% 94.5% 93.7% 99.5% -

Lime/Soda Ash

Softening

3.9% 8.1% 20.5% 17.5% 10.8% 6.9% 5.7% 5.1% -

Source: EPA, 1999a. Geometries and Characteristics of Public Water Systems, Tables 6-1and 6-2.

4.2.9 Financial Profile 

EPA developed a baseline financial profile of all CWSs based on CWSS data. Exhibit 4-9 shows

revenues, expenses, and net revenues by size and ownership. Revenues and expenses are reported

in thousands of dollars and are based on 1995 data. The smallest systems, i.e., those serving 100

people or fewer, have an average revenue of less than $10,000 per year, while the largest systems,

i.e., those serving more than 100,000 people, have an average annual revenue of over $35 million. 

Exhibit 4–9 presents the mean total expenses for all community water systems by service

population category. Annual expenses range from a mean of approximately $7,000 per year for

the smallest systems to over $28 million for the largest systems. In general, revenues exceed

expenses; however, for systems that serve fewer than 500 people, expenses frequently exceed
Chapter 4, Baseline Analysis 4-11 Proposed Arsenic in Drinking Water Rule RIA.

<100 101-500 501-1,000

1,001-

3,300

3,301-

10,000

10,001-

50,000

50,001-

100,000

100,001-

1,000,000

Publicly-Owned

Revenues $9,677 $39,023 $103,981 $238,163 $714,414 $2,701,280 $8,933,319 $35,439,984

Expenses $14,747 $38,781 $96,015 $217,900 $626,242 $2,188,092 $8,010,010 $31,492,090

Net Revenues ($5,070) $242 $7,966 $20,263 $88,172 $513,188 $923,309 $3,947,895

Privately-Owned

Revenues $7,009 $36,206 $110,375 $234,610 $702,382 $3,728,501 $10,188,865 $38,755,625

Expenses $7,366 $37,681 $101,612 $226,307 $621,296 $2,973,931 $8,188,989 $33,333,252

Net Revenues ($356) ($1,476) $8,764 $8,304 $81,086 $754,570 $1,999,877 $5,422,372

All Systems

Revenues $7,486 $37,644 $105,999 $237,326 $711,788 $2,829,324 $9,075,183 $35,750,697

Expenses $8,683 $38,243 $97,782 $219,879 $625,162 $2,286,048 $8,030,233 $31,664,628

Net Revenues ($1,198) ($599) $8,218 $17,447 $86,626 $543,277 $1,044,950 $4,086,070

Source: EPA, 1995. CWSS.

Expense data include operating costs, interest payments, and "other" expenses from systems reporting non-zero values.

Revenue data include total revenues from systems reporting zero values. 

System Size Category

Exhibit 4-9

Baseline Revenues and Expenses for CWSs

revenues.

Unfortunately, there is no available information characterizing non-transient non-community

water system revenues. This is primarily due to the fact that these systems generally do not

operate water systems to generate revenue, but to support their primary business. It should also

be noted that there are potential limitations with using the revenue and expense data from the

CWSS since the data are based on only one year of information during which time all systems may

not have accounted for all water-related revenues.

4.3 Occurrences of Arsenic

EPA has relied on a variety of data sources to evaluate the occurrence of arsenic in community

water systems and non-transient non-community systems. This information supports EPA’s

assessment of baseline conditions, including (1) the number of systems expected to exceed various

MCL options, and (2) the population exposed to different levels of arsenic. 

In 1992, EPA conducted an analysis of the number of systems that would be impacted by various

arsenic MCL options, ranging 0.5 Fμg/L to > 50 Fμg/L. These projections were based on the

following national surveys:

• 1984-1986 National Inorganic and Radionuclide Survey (NIRS) for ground water

systems; 

• 1976-1977 National Organic Monitoring Survey for surface water systems; 
Chapter 4, Baseline Analysis 4-12 Proposed Arsenic in Drinking Water Rule RIA.

• 1978-1980 Rural Water Survey for surface water systems; and 

• 1978 Community Water Supply Survey for surface water systems.

EPA estimated that approximately 150 CWSs and NTNCs with ground water sources and five

CWSs and NTNCs with surface water sources would exceed 50 Fg/L, and that approximately

4,500 CWSs and NTNCs with ground water sources and 350 CWSs and NTNCs with surface

water sources would exceed 5 Fg/L. 

These data sources have several limitations. First, the surveys used for surface water systems

were conducted primarily before 1980. It is likely that arsenic occurrence has changed in the past

two decades due to changes in raw water sources or the addition of filtration treatment to comply

with the Surface Water Treatment Rule (SWTR). In addition, many of the survey responses had

relatively high minimum reporting limits (5 Fg/L). Therefore, it is statistically difficult to

extrapolate low-level arsenic occurrence. 

EPA has subsequently received new data from EPA offices, States, public water utilities, and

associations supporting a new evaluation of baseline occurrences. These data, based on recent

samples, benefit from improved analytical techniques with lower detection limits and lower

reporting limits. The new data include the following:

• Arsenic MCL compliance monitoring data for ground and surface water

community water systems in 25 states; 

• A 1992-1993 national survey of 140 large ground and surface water systems

(greater than 10,000 people), which was performed by the Metropolitan Water

District of Southern California (MWDSC); 

• A 1993 survey examining low levels of arsenic occurrence in surface water and

ground water in the State of California (Association of California Water Agencies;

ACWA); and

• A 1996 national survey of approximately 500 ground and surface water systems

serving more than 1,000 people performed by American Water Works Association

(AWWA).

In addition, the US Geological Survey (USGS) worked extensively with EPA to share arsenic

ambient ground water occurrence data through an Interagency Agreement. 

EPA (1999c) used the MCL compliance monitoring data from 25 states to develop an improved

estimate of national baseline arsenic occurrence. The estimates based on this data are comparable

to those based on the other sources listed above.
Chapter 4, Baseline Analysis 4-13 Proposed Arsenic in Drinking Water Rule RIA.

2 3 5 10 15 20 25 30 40 50

GW 27.20 19.90 12.10 5.43 3.13 2.06 1.45 1.08 0.66 0.44

SW 9.93 6.01 2.90 0.75 0.40 0.26 0.19 0.14 0.09 0.07

Source: EPA, 1999c. Arsenic Occurrence in Public Drinking Water Supplies.

% of systems greater than (μg/L)

Source

Exhibit 4-10

Arsenic Occurrence in CWSs at Various Concentration Levels (μg/L)

MCL 3

GW 3,024 3,256 1,058 1,406 696 434 53 33

SW 62 109 67 137 94 76 16 16

MCL 5

GW 1,898 2,048 671 893 444 286 35 21

SW 32 57 34 70 50 41 8 8

MCL 10

GW 874 934 312 424 218 144 19 11

SW 10 18 11 23 16 13 3 4

MCL 20

GW 343 377 126 177 91 61 8 5

SW 3 5 3 5 5 3 1 1

<100 101-500 501-1,000 1,001-

3,300

3,301-

10,000

10,001-

50,000

50,001-

100,000

100,001-

1,000,000

Exhibit 4-11

Number of CWSs Exceeding Various Arsenic MCL Concentrations (μg/L)

EPA used statistical techniques to assess 

(1) the national distribution of mean arsenic concentrations in water systems, 

(2) the distribution of source means within systems, and 

(3) the number of systems with at least one source above various MCLs. 

Exhibit 4-10 shows the percentage of systems with an arsenic occurrence in excess of ten different

concentration levels, ranging from 2 μg/L to 50 μg/L. Less than one percent of ground water and

surface water systems have a concentration level of arsenic greater than 50 μg/L. In contrast, 27

percent of ground water systems and 10 percent of surface water systems have an arsenic

concentration greater than 2 μg/L. 

Exhibit 4-11 provides a summary of the number of systems expected to exceed various MCLs,

based on the results of EPA’s revised occurrence estimates. 
Chapter 4, Baseline Analysis 4-14 Proposed Arsenic in Drinking Water Rule RIA.
Chapter 5, Benefits Analysis 5-1 Proposed Arsenic in Drinking Water Rule RIA

Chapter 5: Benefits Analysis

5.1 Nature of Regulatory Benefits

The benefits associated with reductions of arsenic in drinking water arise from a reduction in

adverse human health effects. To a lesser degree benefits may also accrue from positive

ecological effects and an avoidance of costly consumers behaviors aimed at avoiding exposure,

such as the cost of bottled water.

The value to consumers of a reduction in the risk of adverse health effects includes the following

components:

• The avoidance of medical costs and productivity losses associated with illness;

• The avoidance of the pain and suffering associated with illness; 

• The losses associated with risk and uncertainty, also called the "risk premium;" and

• The reduction in risk of premature mortality.

This conceptual valuation framework goes beyond valuing out-of-pocket medical costs and lost

time to include the value consumers place on avoiding pain and suffering and the risk premium. 

The risk premium represents the damages associated with risk and uncertainty, captured in the

expression of consumer's "willingness-to-pay" for the reduction in risk of illness (Freeman, 1979). 

This chapter first presents information on the multiple adverse health effects associated with

arsenic, followed by a quantitative risk analysis of a single arsenic related endpoint, bladder

cancer. Due to the large number of potential health effects can’t be quantified, it is likely that the

estimated benefits associated with avoidance of bladder cancer considerably underestimate the

total benefits of a reduction of arsenic in drinking water. 

5.2 Health Effects

5.2.1 Overview 

Exposure to arsenic has many potential health effects which have been described in two recent

publications: Arsenic in Drinking Water by the National Research Council (NRC, 1999), and the

Agency for Toxic Substances and Disease Registry's Draft Toxicological Profile for Arsenic

(ATSDR, 1998). These two sources provide descriptions of health effects which are summarized

in this section, along with additional information provided from the recent literature. 

Ingestion of inorganic arsenic can result in both cancer and non-cancer health effects (NRC,

1999). Exposure may also occur via other routes of exposure including inhalation and dermal

exposure. There is a large human effects database available for inorganic arsenic. However, the

effects of organic forms of arsenic are not as well characterized as those for inorganic arsenic. 

The proposed rule addresses both organic and inorganic forms of arsenic. 

The nature of the health effects avoided by reducing arsenic levels in drinking water is a function
Chapter 5, Benefits Analysis 5-2 Proposed Arsenic in Drinking Water Rule RIA

of characteristics unique to each individual and the level and timing of exposure. Therefore, the

relationship between exposure and response is quite complex. This section describes potential

health effects, but does not reach conclusions about specific effects that might occur due to the

current levels of arsenic in our country’s drinking water.

5.2.2 Carcinogenic Effects 

Arsenic's carcinogenic role was noted over 100 years ago (NCI, 1999) and has been studied since

that time. The Agency has classified arsenic as a Class A human carcinogen, “based on sufficient

evidence from human data. An increased lung cancer mortality was observed in multiple human

populations exposed primarily through inhalation. Also, increased mortality from multiple internal

organ cancers (liver, kidney, lung, and bladder) and an increased incidence of skin cancer were

observed in populations consuming drinking water high in inorganic arsenic.” (EPA, IRIS web

site extracted 8/99).

The International Agency for Research on Cancer (IARC) concluded that inhalation of inorganic

arsenic caused skin and lung cancer in humans. The 1999 NRC report on arsenic states that

"epidemiological studies ... clearly show associations of arsenic with several internal cancers at

exposure concentrations of several hundred micrograms per liter of drinking water" (NRC, 1999).

Ten epidemiological studies, covering eight organ systems, present quantitative data useful for

risk assessment (NRC, 1999, Table 4-1). The organ systems where cancers in humans have been

identified include skin, bladder, lung, kidney, nasal, liver, and prostate.

Table 10-6 of the NRC report provides risk parameters for three cancers: bladder, lung, and liver

cancer. Considering all cancers in aggregate, the NRC states in their Risk Characterization

section that “considering the data on bladder and lung cancer in both sexes noted in the studies in

chapter 4, a similar approach for all cancers could easily result in a combined cancer risk on the

order of 1 in 100” (at the current MCL of 50 μg/L).

New data provide additional health effects information on both carcinogenic and noncarcinogenic

effects of arsenic. A recently study by Tsai et al. (1999) of a population that has been studied

over many years in Taiwan has provided statistically significant standardized mortality ratios

(SMRs) for 23 cancerous and non-cancerous causes of death in women and 27 causes of death in

men. SMRs are an expression of the ratio between deaths that were observed in an area with

elevated arsenic levels and those that were expected to occur, based on the mortality experience

of the populations in nearby areas without elevated arsenic levels. Drinking water (250-1,140

μg/L) and soil (5.3-11.2 mg/kg) in the Tsai et al. (1999) population study had very high arsenic

content.

Tsai et al. (1999) identified “bronchitis, liver cirrhosis, nephropathy, intestinal cancer, rectal

cancer, laryngeal cancer, and cerebrovascular disease” as possibly “related to chronic arsenic

exposure via drinking water.” In addition, the study area had upper respiratory tract cancers

previously only related to occupational inhalation. High male mortality rate (SMR > 3) existed

for bladder, kidney, skin, lung, and nasal cavity cancers and for vascular disease. However, the

authors noted that the mortality range was marginal for leukemia, cerebrovascular disease, liver

cirrhosis, nephropathy (kidney), and diabetes. Females also had high mortalities for laryngeal
Chapter 5, Benefits Analysis 5-3 Proposed Arsenic in Drinking Water Rule RIA

cancer. The SMRs calculated by Tsai et al. (1999) used the one cause of death noted on the

death certificates. Many chronic diseases, including some cancers, do not result in mortality.

Consequently, the impact indicated by the SMR will underestimate the total impact of these

diseases.

There are, of course, possible differences between the population and health care in Taiwan and

the United States. For example, arsenic levels in the U.S. are not nearly as high as they were in

the study area of Taiwan. However, the study gives an indication of the types of health effects

that may be associated with arsenic exposure via drinking water.

5.2.3 Noncarcinogenic Effects

Arsenic interferes with a number of essential physiological activities, including the actions of

enzymes, essential cations, and transcriptional events in cells (NRC, 1999). A wide variety of

adverse health effects have been associated with chronic ingestion of arsenic in drinking water,

occurring at various exposure levels.

Effects on specific organ systems reported in humans exposed to arsenic are listed below in

Exhibit 5-1 (NRC, 1999). Exhibit 5-1 provides descriptive information on the specific diseases

and/or symptoms associated with categories of diseases.
Chapter 5, Benefits Analysis 5-4 Proposed Arsenic in Drinking Water Rule RIA

Exhibit 5-1

Adverse Noncarcinogenic Health Effects Reported in Humans in NRC (1999) as

Potentially Associated with Arsenic, by Organ System Affected

cutaneous effects • hyperpigmentation

• hyperkeratoses

• melanosis

gastrointestinal and hepatic

effects

• noncirrhotic portal hypertension

• gastrointestinal hemorrhage secondary to esophageal varices

• hepatic enlargement

• splenic enlargement

• periportal fibrosis of the liver

• obliterative intimal hypertrophy of intrahepatic venules resulting in obstruction of portal

venous flow, increased splenic pressures, and hypersplenism, and cirrhosis of the liver

• diarrhea

• cramping

cardiovascular and peripheral

vascular effects

• peripheral vascular disease (blackfoot disease) 

• gangrene of the feet 

• coldness and numbness in the extremeties

• intermittent claudication 

• ulceration

• spontaneous amputation 

• Raynaud's syndrome 

• acrocyanosis

• ischemic heart disease

cardiovascular and peripheral

vascular effects (in children)

• arterial spasms in fingers and toesm

• esenteric artery thrombosis

• cerebrovascular disease

• extensive coronary occlusions

• cerebrovascular occlusions

• ischemia of the tongue

• Raynaud's syndrome

• gangrene in extremities

hematological effects • anemia - normocytic, megoblastic

• leukopenia - neutropenia, lymphopenia, eosinophilia

• thrombocytopenia

• reticulocytosis

• erythroid hyperplasia

pulmonary effects • chronic cough

• restrictive and obstructive lung disease

• emphysema

immunological effects • impaired immune response (more specific effects observed in human cell studies and

animal studies- see source)

neurological effects • peripheral neuropathy

endocrine effects • diabetes mellitus

reproductive and developmental

effects

• spontaneous abortion

• perinatal death

• stillbirth

• low birth weight

• birth defects including coarctation of the aorta and others

reproductive and developmental

effects*

• neural tube defects

• ophthalmic abnormalities

• numerous skeletal abnormalities

• urogenital abnormalities

• growth retardation

*Notes in parenthesis indicate where health effects were observed in animal studies rather than human studies.

NRC reports results of numerous animal reproductive and developmental studies and notes that there are “very

few” human studies.
Chapter 5, Benefits Analysis 5-5 Proposed Arsenic in Drinking Water Rule RIA

5.2.4 Susceptible Subgroups

This section discusses the nature of special susceptibilities and identifies population subgroups

that may be at higher risk than the general population when exposed to arsenic. 

5.2.4.1 Definition 

A susceptible subgroup exhibits a response that is different or enhanced when compared to the

responses of most people exposed to the same level of arsenic (ATSDR, 1998). Many diseases

affect certain subgroups of the population disproportionately. The subgroups may be defined by

age, gender, race, ethnicity, socioeconomic status, pre-existing medical conditions, behavioral or

physiological differences, or other characteristics. For example, there are pre-existing medical

conditions that will increase susceptibility to most toxins, such as a pre-existing disease in the

toxin’s target organ. Very few diseases affect all population groups (ages, sexes, races) equally. 

For purposes of evaluating potential benefits to different segments of the population, it is useful to

evaluate whether there are susceptible subpopulations that require consideration. The benefit of

reducing their exposure may be considerably higher than the benefit associated with reducing

exposure among the general population (on a per capita basis).

Special susceptibilities may be indicated by known differences in biological processes that are

essential to detoxification of a toxin. In addition to identifying susceptible subgroups based on

biological processes, susceptible subgroups are often identified by observing higher-than-average

rates of the disease of interest. Increases in the rates of reported diseases may be due to a variety

of factors. Some of these indicate an increased susceptibility; others are matters of personal

choice and may not be considered relevant in a benefits analysis. One way to approach this issue is

to evaluate increased susceptibility when it is based on an increased risk of disease due to factors

reasonably beyond the control of the subpopulation. Factors that are usually beyond the control

of the individual that may cause increased susceptibility include: 

• Constitutional limitations (e.g., illnesses, genetic abnormalities, birth defects such as enzyme

deficiencies);

• Concurrent synergistic exposures that cannot reasonably be controlled (e.g., at home or in

the workplace); and

• Normal constitutional differences (i.e., differences based on sex, age, race, ethnicity, etc).

Other factors that are not usually considered beyond the individual’s control include personal

choices, such as smoking, drinking, and drug use. Choice of place of residence or work may or

may not be treated as a relevant factor. Ultimately, which types of factors should be included in

identifying susceptible subgroups is a matter of public policy.

No studies were located by ATSDR (1998) that focused exclusively on evaluating unusual

susceptibility to arsenic. However, some members of the population are likely to be especially

susceptible due to a variety of factors. These factors include increased dose (intake per unit of

body weight) in children, genetic predispositions, and dietary insufficiency (ATSDR, 1998), as
Chapter 5, Benefits Analysis 5-6 Proposed Arsenic in Drinking Water Rule RIA

well as pre-existing health conditions. 

5.2.4.2 Children

One often-identified susceptible subgroup is children. Due to their increased fluid and food intake

in relation to their body weight (NAS, 1995), their dose (milligrams per kilogram of body weight

per day - mg/kg/day) of arsenic will be, on average, greater than that of adults. For example, an

intake of 1.2 liters per day in a 70 kg adult yields an overall water intake of 0.017 liters per kg of

body weight. An infant who consumes 1 liter per day and weighs 10 kg is consuming 0.1 liter per

kg of body weight, which is more than 5 times the water intake per kg of an adult. Any

contaminant which is present in the water will be delivered at a correspondingly higher level, on a

daily basis. Foy et al., noted that in studies of chronic exposure, children appear to be more

severely affected, probably due to a higher exposure per body weight (1992 citation, reported in

ATSDR, 1998).

The increased daily dose in children can be effectively considered for noncarcinogenic effects

because toxicity is evaluated in terms of exposures that can range from relatively short-term to

long-term exposure. However, carcinogenic effects (i.e., bladder cancer) are evaluated based on a

lifetime of exposure, which takes into consideration the elevated dose that occurs in children. 

Because the only health effect measured in this benefits assessment is bladder cancer, a sensitivity

analysis to consider higher doses of arsenic during childhood was not necessary. However, the

numerous noncarcinogenic effects listed in Exhibit 5-1 may be of greater concern for children than

adults. As the table indicates, many severe cardiovascular effects have been observed in children. 

Avoidance of these effects constitutes an unquantified benefit of the rule.

The adverse reproductive effects listed in Exhibit 5-1 give evidence of the susceptibility of a child. 

The toxic mechanism of action of arsenic involves the inhibition of proliferation of cells, as well as

impairment of the embryonal cell division and mitosis (cell reproduction) (Dong and Luo, 1993,

Jha et al., 1992, Petres et al., 1977, Leonard and Lauwerys, 1980, Li and Chou, 1992, Mottet and

Ferm, 1983 reported in ATSDR, 1998). Arsenic also causes chromosomal aberrations (Jha et al.,

1992, Leonard and Lauwerys, 1980, reported in ATSDR, 1998). These all have serious adverse

implications for critical developmental processes. 

In addition, arsenic crosses the placenta and preferentially accumulates in the embryonic

neuroepithelium, as well as occurring in breast milk (Somogyi and Beck, 1994, reported in

ATSDR, 1998). The neuroepithelium is particularly susceptible during development because the

process of neurulation is being carried out, which involves the development of the neural tube and

other essential structures (Dallaire and Beliveau, 1992, Edelman, 1992, Gunn et al., 1992, Li and

Chou, 1992, Morris-Kay et al., 1994, Scheonwolf and Smith, 1990, Taubeneck et al., 1994,

reported in ATSDR, 1998). 

5.2.4.3 Genetic Predispositions and Dietary Insufficiency

Methylation of arsenic in the liver is a pathway for the detoxification of inorganic arsenic. 

Individuals who are deficient in essential enzymes for this process, or who have a dietary

deficiency of methyl donors (choline or methionine), will be at greater risk following inorganic
Chapter 5, Benefits Analysis 5-7 Proposed Arsenic in Drinking Water Rule RIA

arsenic exposure (Buchet and Lauwerys, 1987; Vahter and Marafante, 1987; Brouwer et al., 1992

cited in ATSDR, 1998). However, liver disease does not appear to increase risk at low levels of

arsenic exposure (Buchet et al., 1982; Geubel et al., 1988 cited in ATSDR, 1998). Therefore,

these factors are not expected to increase risk levels for a significant portion of the U.S.

population.

5.2.4.4 Individuals with Pre-existing Organ Susceptibilities

Individuals may have increased susceptibilities based on specific organ-related factors. Those

with pre-existing diseases (e.g., kidney disease), as well as those with congenital defects (a single

kidney) will be at greater risk from a toxin that either causes additional damage to that organ, or

that relies on that organ for detoxification. In the case of arsenic, both the kidneys and liver are

used to detoxify and remove the contaminant. Both single high doses and long-term low doses

may cause an accumulation of arsenic in the liver and kidneys, which can impair function. In

addition, these organs may be directly damaged by arsenic exposure. A review of Tables 5-1 and

5-2 indicates other organ systems that are targets of arsenic toxicity, including the cardiovascular

system (heart, veins, arteries), hematopoietic system, endocrine system, cutaneous system,

pulmonary system, gastrointestinal system, immune system, and peripheral nervous system. In

individuals with pre-existing damage to these systems or congenital defects in the systems, the

likelihood of risk is greater. Due to the higher incidence of most types of disease among the

elderly, they are more likely to have pre-existing conditions in these organ systems. 

5.2.4.5 Individuals Exposed via Non-water Sources

Although arsenic is ubiquitous at low levels, it is not generally found at levels of concern in food

or air, in the absence of elevated local sources. Where background levels are high, however,

(e.g., elevated levels in water) it is reasonable to consider the contribution to total exposure that

may occur from soil, food, and other local sources. When anthropogenic sources are known to

generate elevated arsenic levels in water (e.g., a local smelter), it is more likely that other media

may be contaminated as well. The total exposure from all sources is a critical component of

evaluating potential health risks and the benefits of avoiding contaminated drinking water in these

cases. A reduction in arsenic in drinking water will reduce the overall exposure to individuals in

living in contaminated areas (e.g., around certain Superfund sites) or workers exposed to arsenic

on the job. Total exposure from all sources is of particular concern for noncancer risks, because

background levels from non-drinking water sources will determine whether the total exposure

leads to an exceedence of a threshold for effects.

5.3 Quantitative Benefits of Avoiding Bladder Cancer

Quantitative risk metrics (e.g., slope factors or reference doses) are necessary to evaluate cancer

or non-cancer risks. Although arsenic causes numerous health effects, bladder cancer is the only

endpoint for which an Agency-approved metric for evaluating arsenic related risk currently exists. 

This cancer slope factor (SF) for bladder cancer is adequate data to perform a risk assessment and

was used to calculate cases potentially avoided due to EPA’s proposed drinking water standards. 

Benefits estimates for avoided cases of bladder cancer were calculated using mean population risk

estimates at various MCL levels. Lifetime risk estimates were converted to annual risk factors,
Chapter 5, Benefits Analysis 5-8 Proposed Arsenic in Drinking Water Rule RIA

and applied to the exposed population to determine the number of cases avoided. Due to a lack

of risk data, health benefit estimates for lung cancer were quantified based on the assumption that

the risks of a fatal lung cancer case associated with arsenic are 2-5 times that of a fatal bladder

cancer case.

5.3.1 Risk Assessment for Bladder Cancer Resulting from Arsenic Exposure

5.3.1.1 Risk Assessment Methodology

Risk assessment is based on the analysis of scientific data to determine the likelihood, nature, and

magnitude of harm to public health associated with particular agents, and involves three main

analytical components: hazard identification (dose-response assessment), exposure assessment,

and risk characterization. Exhibit 5-2 illustrates the steps in a traditional risk assessment process

for characterizing the potential human cancer associated with contaminants in drinking water.

Community Water Systems

The following sections summerize how risk reductions were calculated for populations exposed to

arsenic levels at or above 3 μg/L. The approach for this analysis included five components, which

are described in more detail below. First, EPA used data from the recent EPA water consumption

study. Second, Monte-Carlo simulations were used to develop relative exposure factors. Third,

arsenic occurrence estimates identified the population exposed to levels above 3 μg/L. Fourth,

risk distributions were chosen for the analysis from the 1999 NRC report. Finally, EPA

developed estimates of the actual risks faced by exposed populations using Monte-Carlo

simulations, using the relative exposure factors, occurrence, and risk distributions mentioned

above. A more detailed description of the risk methodology is provided in Appendix B. 

Water Consumption.

EPA recently updated its estimates of per capita daily average estimates of water consumption

(EPA, 1999). The estimates used data from the combined 1994, 1995, and 1996 Continuing

Survey of Food Intakes by Individuals (CSFII), conducted by the U.S. Department of Agriculture

(USDA). The CSFII is a complex, multistage area probability sample of the entire U.S. and is

conducted to survey the food and beverage intake of the U.S. Estimates of water consumed

include direct water, indirect water and total water. “Direct” water is tap water consumed

directly as a beverage. “Indirect” water is defined as water added to foods and beverages during

final preparation at home or by food service establishments such as school cafeterias and

restaurants. For the purpose of the report, indirect water did not include “intrinsic” water which

consists of water found naturally in foods (biological water) and water added by commercial food

and beverage manufactures (commercial water). “Total” water refers to combined direct and

indirect water consumption.
Chapter 5, Benefits Analysis 5-9 Proposed Arsenic in Drinking Water Rule RIA

Exhibit 5-2

Components of the Bladder Cancer Risk Assessment

HAZARD

IDENTIFICATION

EXPOSURE

ASSESSMENT

RISK

CHARACTERIZATION

Toxicity

(dose-response) × Exposure = Health Effects

o

Population Size and Distribution

o

Ingestion/Dose Human Intake Factors

Concentration of Contaminant in

o

Finished Drinking Water Supply and

Available for Human Consumption

Concentration of Contaminant in Source

o

Water

Exhibit 5-3

Source of Water Consumed

Source Direct Tap Water

(drinking)

Indirect Tap Water

(from food and beverages)

Bottled water

Community Tap X X

Other Tap Sources X X

Total X X X

Per capita water consumption estimates are reported by source. Sources include community tap

water, bottled water, and water from other sources, including water from household wells and

rain cisterns, and household and public springs. For each source, the mean and percentiles of the

distribution of average daily per capita consumption are reported. The estimates are based on an

average of 2 days of reported consumption by survey respondents. 

The estimated mean daily average per capita consumption of community tap water by individuals
Chapter 5, Benefits Analysis 5-10 Proposed Arsenic in Drinking Water Rule RIA

in the U.S. population is 1 liter/person/day. For total water, which includes bottled water, the

estimated mean daily average per capita consumption is 1.2 liters per/person/day. These estimates

of water consumption are based on a sample of 15,303 individuals in the 50 States and the District

of Columbia. The sample was selected to represent the entire population of the U.S. based on

1990 census data.

The estimated 90th percentile of the empirical distribution of daily average per capita

consumption of community tap water for the U.S. population is 2.1 liters/person/day; the

corresponding number for daily average per capita consumption of total water is 2.3 

liters/person/day. In other words, current consumption data indicate that 90 percent of the U.S.

population consumes approximately 2 liters/person/day, or less.

Water consumption estimates for selected subpopulations in the U.S. are described in the CSFII,

including per capita water consumption by source for gender, region, age categories, economic

status, race, and residential status and separately for pregnant women, lactating women, and

women in childbearing years. The water consumption estimates by age were used in the

computation of the relative exposure factors discussed below.

Monte-Carlo analysis.

Monte-Carlo analysis is a technique for analyzing problems where there are a large number of

combinations of input values which makes it impossible to calculate every possible result. A

random number generator is used to select input values from pre-defined distributions. For each

set of random numbers a single scenario’s result is calculated. As the simulation runs, the model

is recalculated for each new scenario that continues until a stopping criteria is reached. For the

risk distributions calculated in this report, the simulations were carried out 2,000 times. For each

simulation, a relative exposure factor, occurrence estimate, and individual risk estimate were

calculated. These calculations resulted in estimates of the actual risks faced by populations

exposed to arsenic concentrations in their drinking water. The underlying risk distribution are

described below.

NRC risk distributions.

In its 1999 report, "Arsenic in Drinking Water," the NRC analyzed bladder cancer risks using data

from Taiwan. In addition, NRC examined evidence from human epidemiological studies in Chile

and Argentina, and concluded that risks of bladder and lung cancer had comparable risks to those

“in Taiwan at comparable levels of exposure (NRC, 1999, page 7).” The NRC also examined the

implications of applying different statistical analyses to the newly available Taiwanese data for the

purpose of characterizing bladder cancer risk. For Taiwanese male bladder cancer, using a

Poisson regression model and no data on unexposed populations, yielded a risk at the current

MCL of 1 to 1.347 per 1,000 ( NRC, 1999, Table 10-11). In Table 10-12 of the report, excess

lifetime risk estimates for bladder cancer in males, calculated using EPA’s 1996 cancer guidelines,

is presented (EPA 1996). EPA selected two of these distributions to be representative of the risks

and uncertainty involved (selecting relatively high and relatively low estimates). These
1

 All of these risk distributions are linear in the mean, and thus may be conservative assumptions, as the

NRC report suggested the true relationship may be sublinear. If the true relationship is sublinear, i.e., lower than

the straight line from 50 μg/L to zero, the true risks at levels below 50 μg/L are being overestimated.

Chapter 5, Benefits Analysis 5-11 Proposed Arsenic in Drinking Water Rule RIA

distributions are shown in Exhibit 5-4. 1

Exhibit 5-4

EPA Assumed Life-Time Bladder Risk Estimates for Bladder Cancer Among Males

(Risk per 1,000 Men)

Mean 95% Upper Confidence Limit

0.731 0.807

1.237 1.548

Relative Exposure Factors. 

A Monte-Carlo analysis generated male and female relative exposure factors (REFs) for each of

the broad age categories used in the water consumption study. Lifetime male and female REFs

were then calculated, where the life-long REFs indicate the sensitivity of exposure to an individual

relative to the sensitivity of exposure of an “average” person weighing 70 kilograms and

consuming 2 liters of water per day. These life-long REFs can be directly multiplied by the

average drinking water consumption to provide estimates of individual lifetime consumption

practices. In this analysis, EPA combined the water consumption data with data on population

weight from the U.S. Census. Distributions for both community tap water and total water

consumption were used because the community tap water estimates may underestimate actual tap

water consumption. The weight data included a mean and a distribution of weight for male and

females on a year-to-year basis. The means and standard deviations of the life-long REFs derived

from this analysis are shown in Exhibit 5-5.

Exhibit 5-5

Life-Long Relative Exposure Factors

Community Water Consumption Data Total Water Consumption Data

Male Mean = 0.60

s.d. = 0.61

Mean = 0.73

s.d. = 0.62

Female Mean = 0.64

s.d. = 0.6

Mean = 0.79

s.d. = 0.61

Non-Transient Non-Community Water Systems

Determination of system and individual exposure factors.

In the past, the Agency has directly used SDWIS population estimates for assessing the risks

posed to users of NTNC water systems. In other words, it was assumed that the same person

received the exposure on a year round basis. Under this approach it was generally assumed that all
2For example, airports constitute only about a hundred of the NTNC water systems. Washington’s Reagan

National and Dulles, Dallas/Fort Worth, Seattle/Tacoma, and Pittsburgh airports are the five largest of the airports. 

SDWIS reports that these five airports serve about 300,000 people. In actuality, Bureau of Transportation Statistics

suggest that they serve about eleven million passengers per year. Examination of this information and other BTS

statistics suggests that these airports serve closer to seven million unique individuals over the course of a year and

that exposure occurs on an average of ten times per year per individual customer, not 270 times. 

3For example, travel industry statistics provide information on total numbers of hotel stays, vacancy rates,

traveler age ranges, and average duration of stay. These figures can be combined with the SDWIS peak day

Chapter 5, Benefits Analysis 5-12 Proposed Arsenic in Drinking Water Rule RIA

NTNC users were exposed for 270 days out of the year and obtained fifty percent of their daily

consumption from these systems. As a comparison, TNC users are assumed to use the system for

only ten days per year. 

With the recent completion of Geometries and Characteristics of Public Water Systems (EPA,

1999), however, the Agency has developed a more comprehensive understanding of NTNC water

systems. These systems provide water in due course as part of operating another line of business. 

Many systems are classified as NTNC, rather than TNC water systems, solely because they

employ sufficient workers to trigger the “25 persons served for over six months out of the year”

requirement. Client utilization of these systems is actually much less and more similar to exposure

in TNC water systems. For instance, it is fairly implausible that highway rest areas along

interstate highways serve the same population on a consistent basis (with the exception of long

distance truckers). Nevertheless, there are highway rest areas in both NTNC and TNC system

inventories. The Geometries and Characteristics of Public Water Systems report suggests that

population figures reported in SDWIS which have been used for past risk assessments generally

appear to reflect the number of workers in the establishment coupled with peak day customer

utilization. 

Under these conditions use of the SDWIS figures for population greatly overestimates the actual

individual exposure risk for most of the exposed population and also severely underestimates the

number of people exposed to NTNC water2. Adequately characterizing individual and population

risks necessitates some adjustment of the SDWIS population figures. For chronic contaminants,

such as arsenic, health data reflect the consequences of a lifetime of exposure. Consequently, risk

assessment requires the estimation of the portion of total lifetime drinking water consumption that

any one individual would receive from a particular type of water system. In turn, one needs to

estimate the appropriate portions for daily, days per year, and year per lifetime consumption. 

These estimates need to be prepared for both the workers at the facility and the “customers” of

the facility.

This adjustment was accomplished through a comprehensive review of government and trade

association statistics on entity utilization by SIC code. These figures, coupled with SDWIS

information relating to the portion of a particular industry served by non-community water

systems, made possible the development of two estimates needed for the risk assessment:

customer cycles per year and worker per population served per day. These numbers are required

to distinguish the more frequent and longer duration exposure of workers from that of system

customers3. A more detailed characterization of the derivation of these numbers is contained in
population estimates to allocate daily population among workers, customers and vacancies. The combination of

these factors provides an estimate of the number of independent customer cycles experienced in a year.

Chapter 5, Benefits Analysis 5-13 Proposed Arsenic in Drinking Water Rule RIA

the docket. Exhibit 5-6 provides the factors used in the NTNC risk assessment to account for the

intermittent nature of exposure.

Exhibit 5-6

Exposure Factors Used in the NTNC Risk Assessment

NTNCWS # cycles

per yr

worker/

pop/day

worker

fraction

daily

worker

days/yr

worker

exposure

years

customer

fraction

daily

days of

use/yr

customer

exposure

years

Water

wholesalers

1.00 0.000 - - - 0.25 270 70

Nursing homes 1.00 0.230 0.50 250 40 1.00 365 10

Churches 1.00 0.010 0.50 250 40 0.50 52 70

Golf/country clubs 4.50 0.110 0.50 250 40 0.50 52 70

Food retailers 2.00 0.070 0.50 250 40 0.25 185 70

Non-food retailers 4.50 0.090 0.50 250 40 0.25 52 70

Restaurants 2.00 0.070 0.50 250 40 0.25 185 70

Hotels/motels 86.00 0.270 0.50 250 40 1.00 3.4 40

Prisons/jails 1.33 0.100 0.50 250 40 1.00 270 3

Service stations 7.00 0.060 0.50 250 40 0.25 52 54

Agricultural

products/services 7.00 0.125 0.50 250 40 0.25 52 50

Daycare centers 1.00 0.145 0.50 250 10 0.50 250 5

Schools 1.00 0.073 0.50 200 40 0.50 200 12

State parks 26.00 0.016 0.50 250 40 0.50 14 70

Medical facilities 16.40 0.022 0.50 250 40 1.00 6.7 10.3

Campgrounds/RV 22.50 0.041 0.50 180 40 1.00 5 50

Federal parks 26.00 0.016 0.50 250 40 0.50 14 70

Highway rest areas 50.70 0.010 0.50 250 40 0.50 7.2 70

Misc. recreation

service

26.00 0.016 0.50 250 40 1.00 14 70

Forest Service 26.00 0.016 1.00 250 40 1.00 14 50

Interstate carriers 93.00 0.304 0.50 250 40 0.50 2 70

Amusement parks 90.00 0.180 0.50 250 10 0.50 1 70

Exhibit 5-6

Exposure Factors Used in the NTNC Risk Assessment (continued)
Chapter 5, Benefits Analysis 5-14 Proposed Arsenic in Drinking Water Rule RIA

NTNCWS #

cycles

per yr

worker/

pop/day

worker

fraction

daily

worker

days/yr

worker

exposure

years

customer

fraction

daily

days of

use/yr

customer

exposure

years

Summer camps 8.50 0.100 1.00 180 10 1.00 7 10

Airports 36.50 0.308 0.50 250 40 0.25 10 70

Military bases 1.000 0.50 250 40

Non-water utilities 1.000 0.50 250 40

Office parks 1.000 0.50 250 40

Manufacturing: Food 1.000 0.50 250 40

Manufacturing:

Non-food

1.000 0.50 250 40

Landfills 1.000 1.00 250 40

Fire departments 1.000 1.00 250 40

Construction 1.000 1.00 250 40

Mining 1.000 1.00 250 40

Migrant labor camps 1.000 1.00 250 40

Once the population adjustment factors were derived, it was possible to determine the actual

population served by NTNC water systems. Exhibit 5-7 provides a breakout of these figures by

type of establishment. Although not included in Exhibit 5-7, there are other equally 

important characteristics to note about these systems. With notable exceptions (such as the

airports in Washington, DC and Seattle), the systems generally serve a fairly small population on

any given day. In fact, 99 percent of the systems serve less than 3,300 users on a daily basis. This

means that water production costs will be relatively high on a per gallon basis.

Exhibit 5-7

Composition of NTNCs

(Percentage of Total NTNCWS Population Served by Sector)

Schools 9.7 Medical

Facilities

8 Interstate Carriers 7.1 Campgrounds 1.3

Manufacturing 2.7 Restaurants 0.9 State Parks 8.6 Misc.

Recreation

1.8

Airports 26.1 Non-food Retail 1.6 Amusement Parks 17.7 Other 3.5

Office Parks 0.6 Hotels/Motels 9.2 Highway Rest Area 1.0

Risk calculation.

Calculations of individual risk were prepared for each industrial sector. Even within a given

sector, however, risk varies as a function of an individual’s relative water consumption, body

weight, vulnerability to arsenic exposure, and the water arsenic concentration. Computationally,

risks were estimated by performing Monte-Carlo modeling. The approach used was similar to the

modeling technique applied in estimating the community water system risk estimation, but with
4For example, water consumption among school children was weighted to reflect consumption between

ages 6 and 18, while factory worker consumption was weighted over ages 20 to 64. 

5Community groundwater occurrence information was used since NTNC systems are almost exclusively

supplied by groundwater sources. Further, as there was no depth dependence of arsenic levels observed in the

community information, it is believed that the data are an adequate approximation.

Chapter 5, Benefits Analysis 5-15 Proposed Arsenic in Drinking Water Rule RIA

two notable exceptions. First, each realization in a given sector was multiplied by the portion of

lifetime exposure factor presented in Exhibit 5-4 to reflect the decreased consumption associated

with the NTNC system. Secondly, relative exposure factors were limited to age specific ratings

where appropriate4. For example, in the case of school children, water consumption rates and

weights for six to eighteen year-olds were used. 

To illustrate the process, it was assumed that a child would attend only NTNCWS-served schools

for all twelve years, a somewhat improbable likelihood. Further, it was assumed that a child

would get half of their daily water consumption at school (for an average first grader this would

correspond to roughly nine ounces of water per school day). Finally, it was assumed that the

child would have perfect attendance and attend school for 200 days per year. Exhibit 5-8 below

provides a sample output for the upper bound individual risk distribution to school children

resulting from exposure to the range of untreated arsenic observed in community groundwater

systems5, as well as an estimate based on more moderate assumptions of four ounces per day and

150 days attendance for four years. Upper and lower bound risk distributions were prepared for

both workers and “customers” at all types of NTNC water systems and are contained in Appendix

B. 

Exhibit 5-8

School Children Risk Associated with Current Arsenic Exposure in NTNCs

Exposure Risks Moderate Exposure

Scenario

Upper Bound

Scenario

Mean Lifetime Risk 0.0087 x 10-4 0.079 x 10-4

90th Percentile Lifetime Risk 0.019 x 10-4 0.17 x 10-4

Lifetime Bladder Cancers [out of 575,000 students] 0.5 x 10-4 4.5 x 10-4

The distribution of overall population risks was determined as part of the same simulation by

developing sector weightings to reflect the total portion of the NTNCWS population served by

each sector. Population weighted proportional sampling of the individual sectors provided an

overall distribution of risk among those exposed at NTNC systems.
Chapter 5, Benefits Analysis 5-16 Proposed Arsenic in Drinking Water Rule RIA

5.3.1.2 Risk Assessment Results and Benefit Estimates

Community Water Systems

Estimated Risk Reductions.

Estimated risk reductions for bladder cancer at various MCL levels were developed using MonteCarlo simulations. These simulations combined the distributions of relative risk factors associated

with arsenic levels at or above 3μg/L, and the distribution of general bladder cancer risk taken

from the National Research Council report. Since the relative risk and occurrence distributions

represent primarily population and occurrence variability, and the cancer risk distributions

represent primarily uncertainty about the true risk, the combined distributions contain both

variability and uncertainty. These combined distributions provide more accurate estimates of the

actual risks faced by the exposed population, including the portion of the population facing

various levels of risk.

Estimated risk levels for bladder cancer at various MCL levels are shown in Exhibit 5-9. Results

based on both the community water consumption data and the total water consumption data are

shown. Populations at or above 10-4 risk levels are also summed in Exhibit 5-9. Since there is

uncertainty about these numbers, it is assumed that the range 1 - 1.5 x 10-4 represents a risk level

of essentially 10-4. It is then assumed that risks above 1.5 x 10-4 represent risks greater than 10-4. 

The after treatment occurrence distributions were assumed to reflect treatment to 80 percent of

the MCL level. The latter assumption is made since water systems tend to treat below the MCL

level in order to provide a margin of safety. 

Exhibit 5-10 provides an estimate about percentages of the exposed populations and the number

of people exposed at 10-4 risk levels and above, and, using the stated definition for an over 10-4

risk level, above 10-4. The numbers in this table are based on community water consumption data

and show that at an MCL of 3 μg/L, only a small number (not quantified) face a level of risk

greater than 10-4. At an MCL of 5 μg/L, about 0.3 to 0.8 million face such risk levels. At an

MCL of 10 μg/L, 0.8 to 4 million are at risk, and at an MCL of 20 μg/L, about 2.4 to 6.4 million

would be exposed at such levels. Exhibit 5-11 gives similar information using total water

consumption data.
Chapter 5, Benefits Analysis 5-17 Proposed Arsenic in Drinking Water Rule RIA

Exhibit 5-9

Mean Bladder Cancer Risks for U.S. Populations

Exposed At or Above MCL Options, after Treatment1

MCL

(μg/L)

Mean Exposed

Population Risk

(Community Water

Consumption data)

Mean Exposed

Population Risk

(Total Water

Consumption data)

Mean Exposed

Population Risk

(composite of available

consumption data)

3 2.1 -3.6 x 10-5 2.6 - 4.5 x 10-5 2.1 - 4.5 x 10-5

5 3.6 - 6.1 x 10-5 4.4 - 7.5 x 10-5 3.6 - 7.5 x 10-5

10 5.5 - 9.2 x 10-5 6.7 - 11.4 x 10-5 5.5 - 11.4 x 10-5

20 6.9 - 11.6 x 10-5 8.4 - 13.9 x 10-5 6.9 - 13.9 x 10-5

1The bladder cancer risks presented in this table provide our “best” estimates at this time. Actual risks could be

lower, given the various uncertainties discussed, or higher, as these estimates assume that the probability of illness

from arsenic exposure in the U.S. is equal to the probability of death from arsenic exposure among the Taiwanese

study group. 

Exhibit 5-10

Exposed Population at 10-4 Risk or Higher for Bladder Cancer After Treatment1

(Community Water Consumption data)

MCL

(μg/L)

% at 10-4 Risk

or higher

Population at 10-4 risk or

higher (millions)

% over 10-4* Population over

10-4 (millions)

3 <1 - 2.6% < 0.3 - 0.7 < 1% ‡

5 1.5 - 12% 0.4 - 3.2 < 1 - 3% < 0.3 - 0.8

10 11 - 34% 2.9 - 9.1 3 - 15% 0.8 - 4

20 19.5 - 41% 5.2 - 11 9 - 24% 2.4 - 6.4

1The bladder cancer risks presented in this table provide our “best” estimates at this time. Actual risks could be

lower, given the various uncertainties discussed, or higher, as these estimates assume that the probability of illness

from arsenic exposure in the U.S. is equal to the probability of death from arsenic exposure among the Taiwanese

study group. 

*where over 10-4 means 1.5 x 10-4 or above; ‡ too low to calculate

Exhibit 5-11

Exposed Population at 10-4 Risk or Higher for Bladder Cancer After Treatment1

(Total Water Consumption data)

MCL

(μg/L)

% at 10-4 Risk

or higher

Population at 10-4 risk or

higher (millions)

% over 10-4* Population over

10-4 (millions)

3 < 1 - 3% < 0.3 - 0.8 < 1% ‡

5 3 - 18% 0.8 - 4.8 < 1 - 4% 0.3 - 1.1

10 16 - 50% 4.3 - 13.4 4 - 23% 1.1 - 6.2

20 26 - 53% 7 - 14.2 13 - 33% 3.5 - 8.9

1The bladder cancer risks presented in this table provide our “best” estimates at this time. Actual risks could be

lower, given the various uncertainties discussed, or higher, as these estimates assume that the probability of illness

from arsenic exposure in the U.S. is equal to the probability of death from arsenic exposure among the Taiwanese

study group. 

*where over 10-4 means 1.5 x 10-4 or above; 

‡ too low to calculate
Chapter 5, Benefits Analysis 5-18 Proposed Arsenic in Drinking Water Rule RIA

One adjustment was necessary in order to use the risk distributions contained in the NRC report

to calculate arsenic induced bladder cancer cases at each MCL. As mentioned above, the NRC

risk distributions were based on the Taiwanese studies. In these studies, information on arsenic

related bladder cancer deaths was reported. In order to use these data to determine the

probability of contracting bladder cancer as a result of exposure to arsenic, we must assume a

probability of mortality given the onset of arsenic induced bladder cancer among the Taiwanese

study population. We have decided to bracket the uncertainty about this parameter. For the

lower-end estimate of bladder cancer cases, we assume that this conditional probability is 100

percent. In other words, we are assuming that everyone in the Taiwanese study group that

contracted bladder cancer died of it. Therefore, for the lower-end estimate of bladder cancer

cases, no adjustment to the number of cases estimated using the NRC risk distribution is needed. 

For the upper-end estimate of bladder cancer cases, we assume that this conditional probability is

80 percent. In other words, we are assuming that for every arsenic induced bladder cancer death

recorded among the Taiwanese study population, 1.25 people actually had arsenic induced

bladder cancer. Therefore, we multiplied the number of bladder cases derived using the upper-end

NRC risk distribution by 1.25 to determine our estimate of the upper-end number of bladder

cancer cases at each MCL. 

The number of bladder cancer cases avoided at each MCL are shown in Exhibit 5-12, and range

from 22 to 52 at an MCL of 3 μg/L, 16 to 45 at an MCL of 5 μg/L, 9 to 26 at an MCL of 10

μg/L, and 4 to 15 at an MCL of 20 μg/L. 

Exhibit 5-12

Annual Bladder Cancer Cases Avoided from Reducing Arsenic in CWSs

Arsenic Level

(μg/L)

Reduced Mortality

Cases**

Reduced Morbidity

Cases**

Total Bladder Cancer

Cases Avoided*

3 6 - 14 16 - 39 22 - 52

5 4 - 12 12 - 33 16 - 45

10 2 - 7 7 - 19 9 - 26

20 1 - 4 3 - 11 4 - 15

* The lower-end estimate of bladder cancer cases avoided is calculated using the lower-end risk estimate (see

Exhibit 5-9) and assumes that the conditional probability of mortality among the Taiwanese study group was 100

percent. The upper-end estimate of bladder cancer cases avoided is calculated using the upper-end risk estimate

(see Exhibit 5-9) and assumes that the conditional probability of mortality among the Taiwanese study group was

80 percent.

**Assuming 20-year mortality rate in the U.S. of 26 percent.

Using the “What if?” Scenario for Lung Cancer Benefits

The “What if?” scenario for lung cancer benefits was used to estimate benefits for avoided cases

of lung cancer. This scenario is based on the statement in the NRC report “Arsenic in Drinking

Water,” which states that “some studies have shown that excess lung cancer deaths attributed to

arsenic are 2-5 fold greater than the excess bladder cancer deaths (NRC, 1999, pg. 8).” Two-tofive fold greater would be 3.5 fold greater on average. Also in the U.S. the mortality rate from

bladder cancer is 26% and the mortality rate of lung cancer is 88%. This suggests that if the risk
6

If “X” is the probability of contracting bladder cancer, then 0.26X is the probability of mortality from

bladder cancer. If lung cancer deaths are 2 to 5 times as high as bladder cancer, then they are, on average, 3.5

times as high and the average probability of mortality from lung cancer would be 3.5 times 0.26X, or 0.91X. Since

we also know that there is a 88% mortality rate from lung cancer, then if the probability of contracting lung cancer

is “Y,” the probability of mortality from lung cancer can also be represented as 0.88Y. Setting the two ways of

deriving the probability of mortality from lung cancer equal, or 0.91X = 0.88Y, one can solve for Y 

(Y= (0.91/0.88) X). Thus Y is approximately equal to X, and the rate of contracting lung cancer is approximately

the same as the rate of contracting bladder cancer.

Chapter 5, Benefits Analysis 5-19 Proposed Arsenic in Drinking Water Rule RIA

of contracting lung cancer were identical to the risk of contracting bladder cancer, one would

expect 3.4 times the number of deaths from lung cancer as from bladder cancer. Since these

numbers are essentially the same, it seems reasonable to assume that the risk of contracting lung

cancer is essentially the same as the rate of contracting bladder cancer,6 in the context of this

“what-if” scenario. If the risk of contracting lung cancer from arsenic in drinking water is

approximately equal to the risk of contracting bladder cancer, then the combined risk estimates of

contracting either bladder or lung cancer would be approximately double the risk estimates of

bladder cancer alone.

The number of lung cancer cases avoided for reducing arsenic in CWSs is presented in Exhibit 5-

13, and range from 8 to 80 at an MCL of 3 μg/L, 6 to 68 at an MCL of 5 μg/L, 3 to 40 at an

MCL of 10 μg/L, and 2 to 23 at an MCL of 20 μg/L.

Exhibit 5-13

Potential Annual Lung Cancer Cases Avoided from Reducing Arsenic in CWSs

Arsenic Level

(μg/L)

Reduced Mortality

Cases

Reduced Morbidity

Cases

Total Lung Cancer

Cases Avoided

3 7 - 70 1 - 10 8 - 80

5 5 - 60 1 - 8 6 - 68

10 3 - 35 0 - 5 3 - 40

20 1 - 20 0 - 3 2 - 23

Economic Measurements of the Value of Risk Reduction

The evaluation stage in the analysis of risk reductions involves estimating the value of reducing

the risks. The following sections describe the use of the benefits valuation techniques to estimate

the value of the risk reductions attributable to the regulatory options for arsenic in drinking water. 

First, the approach for valuing the reductions in fatal risks is described, followed by a description

of the approach for valuing the reductions in nonfatal risks.

The benefits described in this RIA are assumed to begin to accrue on the effective date of the rule

and are based on a calculation referred to as the “value of a statistical life” (VSL). Of the many

VSL studies, the Agency recommends using estimates from 26 specific studies that have been
7

 U.S. Environmental Protection Agency, The Benefits and Costs of the Clean Air Act, 1970 to 1990,

October 1997, Appendix I; and U.S. Environmental Protection Agency, Guidelines for Preparing Economic

Analysis (Review Draft), June 1999, Chapter 7.

Chapter 5, Benefits Analysis 5-20 Proposed Arsenic in Drinking Water Rule RIA

peer reviewed and extensively reviewed within the Agency.7 These estimates, which are derived

from wage-risk and contingent valuation studies, range from $0.7 million to $16.3 million and

approximate a Wiebull distribution with a mean of $4.8 million (in 1990 dollars). Most of these

26 studies examine willingness to pay in the context of voluntary acceptance of higher risks of

immediate accidental death in the workplace in exchange for higher wages. This value is sensitive

to differences in population characteristics and perception of risks being valued.

EPA updated the VSL estimate from the The Benefits and Costs of the Clean Air Act, 1970 to

1990 report to a value of $5.8 million in 1997 dollars, according to internal guidance on economic

analyses (personal communication, John Bennett 5/15/00). In order to directly compare the

estimated national costs of compliance, the VSL used in this analysis was updated from the

January 1997 value to $6.06 million in May 1999 dollars, using the Consumer Price Index (CPIU) for all items.

Several factors may influence the estimate of economic benefits associated with avoided cancer

fatalities, including:

1. a possible “cancer premium” (i.e., the additional value or sum that people may be willing to

pay to avoid the experiences of dread, pain and suffering, and diminished quality of life

associated with cancer-related illness and ultimate fatality);

2. the willingness of people to pay more over time to avoid mortality risk as their income rises;

3. a possible premium for accepting involuntary risks as opposed to voluntary assumed risks;

4. the greater risk aversion of the general population compared to the workers in the wage-risk

valuation studies;

5. “altruism” or the willingness of people to pay more to reduce risk in other sectors of the

population; and

6. a consideration of health status and life years remaining at the time of premature mortality. 

Use of certain of these factors may significantly increase the present value estimate. EPA

therefore believes that adjustments should be considered simultaneously. The Agency also

believes that there is currently neither a clear consensus among economists about how to

simultaneously analyze each of these adjustments nor is there adequate empirical data to support

definitive quantitative estimates for all potentially significant adjustment factors. As a result, the

primary estimates of economic benefits presented in the analysis of this proposed rule rely on the

unadjusted estimate.

To estimate the monetary value of reduced fatal risks (i.e., risks of premature death from cancer)

predicted under different regulatory options, value of a statistical life (VSL) estimates are

multiplied by the number of premature fatalities avoided. VSL does not refer to the value of an

identifiable life, but instead to the value of small reductions in mortality risks in a population. A

"statistical" life is thus the sum of small individual risk reductions across an entire exposed

population. For example, if 100,000 people would each experience a reduction of 1/100,000 in
Chapter 5, Benefits Analysis 5-21 Proposed Arsenic in Drinking Water Rule RIA

their risk of premature death as the result of a regulation, the regulation can be said to "save" one

statistical life (i.e., 100,000 x 1/100,000). If each member of the population of 100,000 were

willing to pay $20 for the stated risk reduction, the corresponding value of a statistical life would

be $2 million (i.e., $20 x 100,000). VSL estimates are appropriate only for valuing small changes

in risk; they are not values for saving a particular individual's life.

Estimates of the willingness to pay to avoid treatable, nonfatal cancers are the ideal economic

measures used to value reductions in nonfatal risks. Unfortunately, this information is not

available for bladder cancer. However, willingness to pay (WTP) data to avoid chronic bronchitis

is available, and has previously been employed by OGWDW (the microbial/disinfection byproduct (MDBP) rulemaking) as a surrogate to estimate the WTP to avoid non-fatal bladder

cancer. A WTP central tendency estimate of $607,162 (May 1999$) is used to monetize the

benefits of avoiding non-fatal cancers (this value was updated from the $536,000 value EPA

updated to 1997$ from the Viscusi et al. 1991 study).

To ground-truth the use of the chronic bronchitis WTP value as a proxy for bladder cancer WTP,

EPA has also developed cost of illness estimates for bladder cancer, as reported in Exhibit 5-14. 

These estimates of direct medical costs are derived from a study conducted by Baker et al.

(1989), which uses data from a sample of Medicare records for 1974 - 1981. These data include

the total charges for inpatient hospital stays, skilled nursing facility stays, home health agency

charges, physician services, and other outpatient and medical services. EPA combined these data

with estimates of survival rates and treatment time periods to determine the average costs of

initial treatment and maintenance care for patients who do not die of the disease. This value of

$178,405 at a 3 percent discount rate, serves as a low-end estimate of the WTP to avoid bladder

cancer and does not include the value of avoided pain and suffering, lost productivity, or risk

premium.

Exhibit 5-14

Lifetime Avoided Medical Costs for Survivors

(preliminary estimates1)

Type of

Cancer

Date Data

Collected Number of Cases Studied

Estimated

Mortality Rate

Mean Value per

Nonfatal Case

(Discount Rate) 1

Bladder 1974-1981 5% of 1974 

Medicare patients

(sample from national statistics)

26 percent

(after 20 years)

$178,405 (3%)

$147,775 (7%)

(for typical individual

diagnosed at age 70)

1. May 1999 dollars

Source: U.S. Environmental Protection Agency, Cost of Illness Handbook (draft), September 1998.

Estimates of Cancer Health Benefits of Arsenic Reduction

Benefits estimates were calculated using mean population risk estimates at various MCL levels

(the composite values of the mean population risks presented in Exhibit 5-9). Lifetime risk

estimates were converted to annual risk factors, and applied to the exposed population to

determine the number of bladder cases avoided per year (Exhibit 5-12). Exhibit 5-13 describes
Chapter 5, Benefits Analysis 5-22 Proposed Arsenic in Drinking Water Rule RIA

the number of lung cancer cases avoided per year. These cases were divided into fatal and nonfatal cases avoided, based on survival information. The avoided premature fatalities were valued

based on the VSL estimates discussed earlier, as recommended by current EPA guidance for

cost/benefit analysis (EPA, 1997). The avoided non-fatal cases were valued based on the

willingness to pay estimates for the avoidance of chronic bronchitis.

The results of the benefits valuation are presented in Exhibit 5-15. Total annual health benefits

resulting from bladder cancer cases avoided range from $43.6 to $104.2 at an MCL of 3 μg/L, 

$31.7 to $89.9 at an MCL of 5 μg/L, $17.9 to $52.1 at an MCL of 10 μg/L, and $7.9 to $29.8 at

an MCL of 20 μg/L. Potential annual health benefits from avoided cases of lung cancer, when

estimated based on the “what if” scenario in which the risks of a fatal lung cancer case associated

with arsenic is assumed to be two to five times that of a fatal bladder cancer case, range from

$47.2 to $448.0 at an MCL of 3 μg/L, $35.0 to $384.0 at an MCL of 5 μg/L, $19.6 to $224.0 at

an MCL of 10 μg/L, and $8.8 to $128.0 at an MCL of 20 μg/L. In addition, other potential nonquantifiable health benefits are summarized in Exhibit 5-15.

Exhibit 5-15

Estimated Monetized Total Cancer Health Benefits and

Non-Quantifiable Health Benefits from Reducing Arsenic in CWSs

Arsenic

Level 

(μg/L)

Annual

Bladder Cancer

Health Benefits

($millions)1,2

“What-if” Scenario and Potential Non-Quantifiable

Health Benefits

“What-if” Scenario

Annual

Lung Cancer

Health Benefits

($millions)1,3

Potential Non-Quantifiable

Health Benefits

3 $43.6 - $104.2 $47.2 - $448.0

• Skin Cancer

• Kidney Cancer

• Cancer of the Nasal Passages

• Liver Cancer

• Prostate Cancer

• Cardiovascular Effects

• Pulmonary Effects

• Immunological Effects

• Neurological Effects

• Endocrine Effects

• Reproductive and Developmental

Effects

5 $31.7 - $89.9 $35.0 - $384.0

10 $17.9 - $52.1 $19.6 - $224.0

20 $7.9 - $29.8 $8.8 - $128.0

1. May 1999 dollars.

2. The lower-end estimate is calculated using the lower-end number of bladder cancer cases avoided (see

Exhibit 5-12) and assumes that the conditional probability of mortality among the Taiwanese study group was

100 percent. The upper-end estimate is calculated using the upper-end number of cancer cases avoided (see

Exhibit 5-12) and assumes that the conditional probability of mortality among the Taiwanese study group was 80

percent.

3. These estimates are based on the “what if” scenario for lung cancer, where the risks of a fatal lung cancer

case associated with arsenic are assumed to be 2-5 times that of a fatal bladder cancer case.
Chapter 5, Benefits Analysis 5-23 Proposed Arsenic in Drinking Water Rule RIA

Non-Transient Non-Community Water Systems

Exhibit 5-16 presents a summary of the risk and benefit analyses for regulation of arsenic in

NTNC water systems. Exhibit 5-17 presents risk figures for three particular sets of individuals:

children in daycare centers and schools, and construction workers. Construction and other

strenuous activity workers comprise an extremely small portion of the population served by

NTNC systems (less than 0.1 percent), but face the highest relative risks of all NTNCWS users

(90th percentile risks of 0.7 to 1.6 x 10-4 lifetime risk).

Exhibit 5-16

Mean Bladder Cancer Risks, Exposed Population,

and Annual Cancer Benefits in NTNCs1

Arsenic

Level

(μg/L)

Mean Exposed Population

Risk (10-4)

Total Bladder Cancer

Cases Avoided

per Year

Annual Benefits

($millions)2

lower

bound

upper

bound

lower

bound

upper

bound

lower

bound

upper

bound

3 0.0046 0.01 0.132 0.294 $0.610 $2.717

5 0.0077 0.017 0.104 0.229 $0.481 $2.116

10 0.012 0.026 0.064 0.147 $0.296 $1.359

20 0.015 0.033 0.039 0.088 $0.180 $0.814

baseline 0.019 0.042 -- -- -- --

1. Note that this table does not include lung cancer benefits.

2. May 1999 dollars

Exhibit 5-17

Sensitive Group Evaluation of Lifetime Risks

Group Mean Risk 90th Percentile Risk

Forest Service, Construction and Mining Workers 3.2 - 7 x 10-5 7.2 - 16 x 10-5

School Children 3.8 - 7.9 x 10-6 0.84 - 1.7 x 10-5

Day Care Children 3.4 - 6.8 x 10-6 0.74 - 1.5 x 10-5

However, there is considerable uncertainty about these exposure numbers, as it is quite likely that

they overestimate consumption. The risks for children are much lower with an upper bound, 90th

percentile estimate of 1.7 x 10-5 lifetime risk. What is not possible to determine from the analysis

of NTNC systems is the extent to which there is overlap of individual exposure between the

various sectors. NTNC establishments generally constitute a small portion of their SIC sectors. 

In conjunction with the observation that NTNC populations would only serve about eleven

percent of the total population if all sectors were mutually exclusive, it would seem reasonable to

treat the SIC groups independently. However, it is equally plausible that there are communities

where one individual might go from an NTNC day care center to a series of NTNC schools and

then work in an NTNC factory. Unfortunately, the Agency presently has no basis for
Chapter 5, Benefits Analysis 5-24 Proposed Arsenic in Drinking Water Rule RIA

quantitatively estimating the extent to which this would occur.

The Agency is quite concerned about the potential for local issues to arise with respect to

combined arsenic exposures. In the rare community where all ground water is contaminated with

the highest levels of arsenic, risks could be outside of the Agency’s traditionally allowable range.

5.4 Other Benefits of Reductions in Arsenic Exposure

Although health effects are the primary focus of this analysis, arsenic also has negative impacts on

the ecology and on public perceptions and acceptance of drinking water. These are briefly

discussed below.

5.4.1 Ecological Effects

Ecological effects are not quantified in this benefits assessment. However, they are anticipated to

occur at levels of severity that are in proportion to the levels of contamination that occur. Since

drinking water is ultimately reintroduced into the environment, arsenic contamination of drinking

water is of concern for its potential adverse impacts on the ecology. The avoidance of ecological

effects resulting from the proposed rule constitutes an non-quantified benefit of the rule.

Arsenic has numerous ecological effects on multiple biological systems, as indicated in the health

effects listed in Exhibit 5-1. While there are differences in the function and disease induction

between humans and animals, there are also striking similarities. The anatomy and physiology of

most animal systems share many common elements, including most of the basic organ systems and

biochemical processes. Effects observed in humans are generally assumed to be similar to those

observed in animals, with the exception of higher cognitive functions. This is the basis for the

extensive animal laboratory testing programs and requirements that EPA uses to evaluate the

toxicity of chemicals on humans.

It is likely that most if not all of the effects observed in humans (listed in Exhibit 5-1) will also be

observed in animals. As noted above, there are also numerous animal studies that have

demonstrated effects in various species. Arsenic, a heavy metal, bioaccumulates in many

biological materials and can move through the food chain through a variety of pathways. In

addition to damage caused directly on ecological systems, ecological effects may indirectly cause

adverse effect in humans, through ingestion of contaminated plants or animals. 

5.4.2 Drinking Water Quality and Public Perception

It is well established that the public often avoids the use of tap water that is suspected to be

contaminated. In this context, contamination may suggest biological, chemical, or other water

quality issues. When public perception of water quality declines, consumers purchase bottled

water if they have the means to do so. In addition or as an alternative, they may avoid the use of

tap water, ingesting and cooking with other liquids, substituting pre-mixed baby formula, and

using other strategies to limit ingestion. Consumer avoidance of tap water sources usually results

in costs to the consumers, either in the cost of obtaining substitute fluids or potential health

impacts of reduced fluid intake. In addition, there are numerous cases where government
Chapter 5, Benefits Analysis 5-25 Proposed Arsenic in Drinking Water Rule RIA

agencies have provided bottled water due to biological or chemical contamination. The levels of

contamination at which the government activities occur vary depending on a variety of factors. 

The relationship between arsenic in tap water and changes in consumer behavior or government

interventions is a complex one. Factors that impact the choice to avoid tap water depend on

public information that is provided on levels of contamination, potential health effects, individual

aversions to risk taking, and other considerations. A quantitative evaluation of these responses

and the potential benefits of avoiding associated costs to the consumer or governments is not

included in this benefits assessment. However, it is clear that many consumers purchase bottled

water (a multimillion dollar industry) or invested in other methods of improving drinking water

quality, such as point-of-use (POU) devices, specifically to avoid ingestion of contaminants such

as arsenic. Thus, it is reasonable to conclude that a reduction in arsenic contamination will have

the long-term effect of restoring some level of consumer confidence in the water supply.
Chapter 5, Benefits Analysis 5-26 Proposed Arsenic in Drinking Water Rule RIA
Chapter 6, Cost Analysis 6-1 Proposed Arsenic in Drinking Water Rule RIA

Chapter 6: Cost Analysis

6.1 Introduction

This chapter presents the national cost estimates for the proposed Arsenic Rule. The costs

associated with the proposed rule include: 1) costs borne by water systems to comply with the

new MCL standard and modified monitoring requirements, and 2) costs to the States to

implement and enforce the rule. Section 6.2 describes the inputs and methodologies used to

estimate costs, including the following:

• a description of the technologies that may be used by systems to achieve the MCL

(Section 6.2.1), 

• the unit costs of different technologies for complying with the MCLs (Section 6.2.2),

• system and State unit costs for monitoring and administration functions (Section 6.2.3),

• the methods used to predict systems’ compliance methods and the methods used to

calculate costs (Section 6.2.4). 

Section 6.3 presents the results of the cost analysis, including the following:

• a summary of national costs for the different regulatory options (Section 6.3.1), 

• costs by system size and type for the proposed option (Section 6.3.2), 

• and household costs (Section 6.3.3).

6.2 Methodology

6.2.1 Description of Available Technologies

In 1993, EPA developed a document entitled Treatment and Occurrence-Arsenic in Potable

Water Supplies (EPA,1993) which summarized the results of pilot-scale studies examining

low-level arsenic removal, from 50 parts per billion (ppb or μg/L) down to 1 ppb or less. EPA

convened a panel of outside experts in January 1994 to review this document and comment on the

ability of the technologies to achieve various MCLs. The Agency has since sought stakeholder

input on the use of various technologies for arsenic removal under different conditions, and has

incorporated that input into its estimates of technology performance and costs. The results are

documented in the Cost and Technology Document for the Arsenic Rule (US EPA, July 1999). 

The technology cost functions and removal efficiencies presented in that document are used as

inputs for the cost analyses presented in this RIA.

EPA reviewed fourteen treatment technologies. Of these, five are the most relevant for small

systems:

• Ion exchange

• Activated alumina

• Reverse osmosis

• Nanofiltration

• Electrodialysis reversal
Chapter 6, Cost Analysis 6-2 Proposed Arsenic in Drinking Water Rule RIA

Two technologies are used primarily in larger systems and are not expected to be installed solely

for arsenic removal:

• Coagulation/filtration

• Lime softening

Finally, seven additional alternative technologies were characterized as still emerging:

• Iron-oxide coated sand

• Granular ferric hydroxide

• Iron filings

• Sulfur-modified iron

• Greensand filtration

• Iron addition with microfiltration

• Conventional iron/manganese removal 

Some technologies generate wastes which require disposal, or require pre-treatment (e.g., preoxidation or corrosion control)in order to be effective. These associated requirements were

identified for different technologies and system types, and their costs were included in the costs of

treatment where relevant. 

In addition to these centralized treatment options, small systems may elect to use point-of-use

(POU) or point-of-entry (POE) devices to achieve compliance with the MCLs. POE involves

whole house treatment, whereas POU treats water at the tap. The available POE/POU

technologies for arsenic removal are essentially smaller versions of reverse osmosis, activated

alumina, and ion exchange. The technologies will have to be maintained by the water system,

involving some additional recordkeeping and maintenance costs. 

Finally, some systems may elect to comply with the lower MCL by obtaining water from

alternative sources that meet the standard, or by interconnecting with another water system to

combine treatment or share the cost of treatment (referred to as “regionalization”).

The result of the review of technologies that would effectively remove arsenic and bring a water

system into compliance is summarized in Exhibit 6-1. The list includes 25 treatment trains

available to systems, consisting of various combinations of compliance technologies, waste

disposal technologies, or pre-treatment technologies as required.
POTW Evaporation 

Pond

NonHazardous 

Landfill

Direct 

Discharge

Chemical 

Precipitation

Mechanical 

DeWatering

NonMechanical 

DeWatering

1 Regionalization 90%

2 Alternate Source 90%

3 Modify Lime Softening T 80%

4 Modify Coagulation/Filtration T 95%

5 Anion Exchange (25 mg/L SO4) T T T 95%

6 Anion Exchange (150 mg/L SO4) T T T 95%

7 Anion Exchange (25 mg/L SO4) T T T T 95%

8 Anion Exchange (150 mg/L SO4) T T T T 95%

9 Activated Alumina (2,000 BV) T* T 90%

10 Activated Alumina (10,000 BV) T* T 90%

11 Reverse Osmosis T T T 95%

12 Reverse Osmosis T T T 95%

13 Reverse Osmosis T T T T 95%

14 Coagulation Assisted Microfiltration T T T 90%

15 Coagulation Assisted Microfiltration T T T 90%

16 Oxidation Filtration (Greensand) T** 50%

17 Anion Exchange (25 mg/L SO4) T T T T 95%

18 Anion Exchange (150 mg/L SO4) T T T T 95%

19 Activated Alumina (2,000 BV) T T T 90%

20 Activated Alumina (10,000 BV) T T T 90%

21 Anion Exchange (90 mg/L SO4) T T T 95%

22 Anion Exchange (90 mg/L SO4) T T T T 95%

23 POE Activated Alumina T T 99%

24 POU Reverse Osmosis T 99%

25 POU Activated Alumina T 99%

* non-hazardous landfill (for spent media)

** POTW for backw ash stream

PreOxidationRemoval 

Efficiency

Treatment Technology

Waste Disposal Technology

Corrosion 

Control

Exhibit 6-1

Arsenic Rule Treatment Trains by Compliance Technologies Component, with Associated Removal Efficiencies
Chapter 6, Cost Analysis 6-4 Proposed Arsenic & Drinking Water Rule RIA

6.2.2 Unit Costs and Compliance Assumptions

Treatment

EPA estimated the costs of the various compliance technologies, including centralized treatment

technologies (with associated waste disposal and pre-treatment), POE/POU treatment, and

regionalization. Costs of each treatment train are estimated as functions of system size; design

flow is used to calculate capital costs and average flow is used to calculate operating and

maintenance (O&M) costs. Exhibit 6-2 presents a summary of compliance technology costs by

cost component for the treatment trains listed in Exhibit 6-1, annualized over 20 years at a seven

percent discount rate. Costs are in May 1999 dollars and are based on average and design flows

for median populations of each system size category, assuming one entry point per system. Note

that the capital and O&M cost components are listed separately for the treatment and waste

disposal components of the treatment train, and totaled to equal the annual cost, excluding

corrosion control or pre-oxidation costs. Detailed descriptions of the assumptions and

methodologies used to develop these cost estimates are available in the Cost and Technology

Document for the Arsenic Rule (US EPA, July 1999).
Size Category Treatment Train No. 1 2 3 4 5 6 7 8

< 100

Treatment Capital Costs $ 280,000 $ 20,000 $ 8,830 $ 7,370 $ 39,477 $ 39,477 $ 39,477 $ 39,477

Treatment O&M Costs $ - $ - $ 12,617 $ 7,107 $ 5,614 $ 12,669 $ 5,614 $ 12,669

Waste Disposal Capital Costs $ - $ - $ 7,400 $ 7,400 $ 3,955 $ 3,955 $ 16,534 $ 47,004

Waste Disposal O&M Costs $ - $ - $ 564 $ 564 $ 464 $ 566 $ 1,435 $ 3,251

Annual Costs (7%) $ 26,430 $ 1,888 $ 14,713 $ 9,065 $ 10,178 $ 17,335 $ 12,336 $ 24,084

101-500

Treatment Capital Costs $ 280,000 $ 20,000 $ 13,530 $ 8,858 $ 83,934 $ 83,934 $ 83,934 $ 83,934

Treatment O&M Costs $ - $ - $ 14,520 $ 7,556 $ 10,099 $ 22,763 $ 10,099 $ 22,763

Waste Disposal Capital Costs $ - $ - $ 7,400 $ 7,400 $ 3,955 $ 3,955 $ 69,282 $ 201,124

Waste Disposal O&M Costs $ - $ - $ 1,575 $ 1,575 $ 694 $ 1,370 $ 4,988 $ 11,698

Annual Costs (7%) $ 26,430 $ 1,888 $ 18,071 $ 10,666 $ 19,089 $ 32,430 $ 29,549 $ 61,369

501-1000

Treatment Capital Costs $ 280,000 $ 20,000 $ 20,397 $ 11,244 $ 132,451 $ 132,451 $ 132,451 $ 132,451

Treatment O&M Costs $ - $ - $ 18,056 $ 8,403 $ 16,999 $ 39,246 $ 16,999 $ 39,246

Waste Disposal Capital Costs $ - $ - $ 7,400 $ 7,400 $ 3,955 $ 3,955 $ 145,896 $ 423,558

Waste Disposal O&M Costs $ - $ - $ 3,528 $ 3,528 $ 1,137 $ 2,920 $ 9,626 $ 23,102

Annual Costs (7%) $ 26,430 $ 1,888 $ 24,207 $ 13,691 $ 31,012 $ 55,041 $ 52,898 $ 114,831

1,001-3,300

Treatment Capital Costs $ 280,000 $ 20,000 $ 32,164 $ 16,823 $ 770,479 $ 770,479 $ 770,479 $ 770,479

Treatment O&M Costs $ - $ - $ 28,499 $ 11,005 $ 35,971 $ 86,719 $ 35,971 $ 86,719

Waste Disposal Capital Costs $ - $ - $ 7,697 $ 7,697 $ 3,955 $ 3,955 $ 343,395 $ 997,008

Waste Disposal O&M Costs $ - $ - $ 10,072 $ 10,072 $ 2,598 $ 8,033 $ 20,943 $ 51,831

Annual Costs (7%) $ 26,430 $ 1,888 $ 42,333 $ 23,391 $ 111,670 $ 167,853 $ 162,055 $ 305,388

Exhibit 6-2

Average Compliance Technology Costs (Treatment Train 1 through 8)

NOTE:

1) Refer to Exhibit 6-1 for a description of treatment train technologies.

2) Average costs per size category are based on median population and associated flows, assuming one entry point per system.
Size Category Treatment Train No. 1 2 3 4 5 6 7 8

3,300-10,000

Treatment Capital Costs $ 280,000 $ 20,000 $ 225,058 $ 239,649 $ 2,495,535 $ 2,495,535 $ 2,495,535 $ 2,495,535

Treatment O&M Costs $ - $ - $ 49,872 $ 113,459 $ 8,922 $ 8,922 $ 8,922 $ 8,922

Waste Disposal Capital Costs $ - $ - $ 9,334 $ 9,334 $ 5,085 $ 5,085 $ 859,811 $ 3,312,119

Waste Disposal O&M Costs $ - $ - $ 32,781 $ 32,781 $ 8,312 $ 26,268 $ 49,672 $ 127,510

Annual Costs (7%) $ 26,430 $ 1,888 $ 104,778 $ 169,742 $ 253,275 $ 271,231 $ 375,315 $ 684,633

10,001-50,000

Treatment Capital Costs $ 280,000 $ 20,000 $1,237,501 $1,393,797 $ 9,160,742 $ 9,160,742 $ 9,160,742 $ 9,160,742

Treatment O&M Costs $ - $ - $ 162,684 $ 736,014 $ 33,090 $ 33,090 $ 33,090 $ 33,090

Waste Disposal Capital Costs $ - $ - $ 10,898 $ 10,898 $ 5,085 $ 5,981 $ 3,945,421 $ 15,570,260

Waste Disposal O&M Costs $ - $ - $ 157,559 $ 157,559 $ 36,512 $ 124,966 $ 166,059 $ 448,436

Annual Costs (7%) $ 26,430 $ 1,888 $ 438,083 $1,026,166 $ 934,791 $ 1,023,330 $ 1,436,278 $ 2,815,958

50,001-100,000

Treatment Capital Costs $ 280,000 $ 20,000 $2,055,598 $1,853,803 $ 19,339,675 $ 19,339,675 $ 19,339,675 $ 19,339,675

Treatment O&M Costs $ - $ - $ 368,722 $1,137,506 $ 70,123 $ 70,123 $ 70,123 $ 70,123

Waste Disposal Capital Costs $ - $ - $ 13,766 $ 13,766 $ 5,735 $ 7,076 $ 9,956,569 $ 33,925,583

Waste Disposal O&M Costs $ - $ - $ 413,912 $ 413,912 $ 94,447 $ 327,739 $ 357,083 $ 993,137

Annual Costs (7%) $ 26,430 $ 1,888 $ 977,967 $1,727,703 $ 1,990,640 $ 2,224,058 $ 3,192,564 $ 6,091,123

100,001-1,000,000

Treatment Capital Costs $ 280,000 $ 20,000 $6,936,516 $3,672,160 $139,484,072 $139,484,072 $139,484,072 $ 139,484,072

Treatment O&M Costs $ - $ - $2,753,482 $2,931,378 $ 497,678 $ 497,678 $ 497,678 $ 497,678

Waste Disposal Capital Costs $ - $ - $ 48,804 $ 48,804 $ 9,572 $ 20,505 $ 62,342,119 $ 140,291,110

Waste Disposal O&M Costs $ - $ - $3,402,673 $3,402,673 $ 769,897 $ 2,691,813 $ 2,038,240 $ 5,985,719

Annual Costs (7%) $ 26,430 $ 1,888 $6,815,520 $6,685,285 $ 14,434,787 $ 16,357,736 $ 21,586,882 $ 32,892,195

Exhibit 6-2 continued

Average Compliance Technology Costs (Treatment Train 1 through 8)

NOTE:

1) Refer to Exhibit 6-1 for a description of treatment train technologies.

2) Average costs per size category are based on median population and associated flows, assuming one entry point per system.
Size Category 9 10 11 12 13 14 15 16

< 100

$ 49,780 $ 49,780 $ 156,629 $ 156,629 $ 156,629 $ 65,210 $ 65,210 $ 24,983

$ 2,816 $ 2,816 $ 25,439 $ 25,439 $ 25,439 $ 13,108 $ 13,108 $ 7,747

$ - $ - $ 3,520 $ 3,520 $ 40,587 $ 23,260 $ 27,122 $ 3,955

$ 21 $ 21 $ 1,368 $ 1,368 $ 11,267 $ 3,701 $ 2,088 $ 464

$ 7,536 $ 7,536 $ 41,924 $ 41,924 $ 55,322 $ 25,160 $ 23,911 $ 10,943

101-500

$ 210,637 $ 210,637 $ 433,067 $ 433,067 $ 433,067 $ 145,362 $ 145,362 $ 104,869

$ 9,693 $ 9,693 $ 51,709 $ 51,709 $ 51,709 $ 17,159 $ 17,159 $ 9,495

$ - $ - $ 3,457 $ 3,457 $ 70,251 $ 26,273 $ 37,421 $ 3,955

$ 137 $ 137 $ 11,724 $ 11,724 $ 17,439 $ 4,941 $ 2,299 $ 694

$ 29,712 $ 29,712 $ 104,639 $ 104,639 $ 116,658 $ 38,301 $ 36,711 $ 20,462

501-1000

$ 485,414 $ 485,414 $ 710,071 $ 710,071 $ 710,071 $ 304,855 $ 304,855 $ 218,393

$ 23,047 $ 23,047 $ 92,892 $ 92,892 $ 92,892 $ 28,132 $ 28,132 $ 12,948

$ - $ - $ 3,552 $ 3,552 $ 109,999 $ 31,420 $ 52,696 $ 3,955

$ 360 $ 360 $ 31,207 $ 31,207 $ 27,080 $ 7,330 $ 2,707 $ 1,137

$ 69,227 $ 69,227 $ 191,460 $ 191,460 $ 197,381 $ 67,205 $ 64,590 $ 35,073

1,001-3,300

$ 1,302,755 $ 1,302,755 $ 1,623,013 $ 1,623,013 $ 1,623,013 $ 726,146 $ 726,146 $ 507,481

$ 67,590 $ 67,590 $ 222,259 $ 222,259 $ 222,259 $ 37,152 $ 37,152 $ 24,350

$ - $ - $ 4,571 $ 4,571 $ 152,058 $ 51,820 $ 122,455 $ 3,955

$ 1,099 $ 1,099 $ 74,606 $ 74,606 $ 40,523 $ 21,160 $ 5,696 $ 2,598

$ 191,659 $ 191,659 $ 450,497 $ 450,497 $ 430,336 $ 131,746 $ 122,950 $ 75,224

Exhibit 6-2 continued

Average Compliance Technology Costs (Treatment Train 9 through 16)

NOTE:

1) Refer to Exhibit 6-1 for a description of treatment train technologies.

2) Average costs per size category are based on median population and associated flows, assuming one entry point per system.
Size Category 9 10 11 12 13 14 15 16

3,300-10,000

$ 3,803,627 $ 3,803,627 $ 3,935,731 $ 3,935,731 $ 3,935,731 $ 1,510,476 $ 1,510,476 $ 1,253,212

$ 219,658 $ 219,658 $ 561,953 $ 561,953 $ 561,953 $ 73,586 $ 73,586 $ 63,448

$ - $ - $ 5,382 $ 5,382 $ 197,836 $ 118,824 $ 410,913 $ 5,085

$ 3,630 $ 3,630 $ 108,199 $ 108,199 $ 65,423 $ 21,276 $ 22,801 $ 8,312

$ 582,324 $ 582,324 $ 1,042,166 $ 1,042,166 $ 1,017,556 $ 248,656 $ 277,753 $ 190,535

10,001-50,000

$ 15,997,473 $ 15,997,473 $ 15,030,714 $ 15,030,714 $ 15,030,714 $ 5,348,970 $ 5,348,970 $ 4,186,608

$ 1,075,859 $ 1,075,859 $ 2,429,780 $ 2,429,780 $ 2,429,780 $ 280,577 $ 280,577 $ 283,584

$ - $ - $ 7,898 $ 7,898 $ 476,817 $ 177,968 $ 907,819 $ 5,085

$ 17,881 $ 17,881 $ 526,046 $ 526,046 $ 153,221 $ 55,113 $ 61,314 $ 36,512

$ 2,603,788 $ 2,603,788 $ 4,375,365 $ 4,375,365 $ 4,046,803 $ 857,394 $ 932,488 $ 715,762

50,001-100,000

$ 38,371,441 $ 38,371,441 $ 35,105,717 $ 35,105,717 $ 35,105,717 $ 7,496,682 $ 7,496,682 $ 8,718,795

$ 2,834,902 $ 2,834,902 $ 5,457,968 $ 5,457,968 $ 5,457,968 $ 580,569 $ 580,569 $ 735,847

$ - $ - $ 12,515 $ 12,515 $ 988,706 $ 285,159 $ 1,816,207 $ 5,735

$ 47,159 $ 47,159 $ 1,376,897 $ 1,376,897 $ 333,600 $ 124,631 $ 139,960 $ 94,447

$ 6,504,053 $ 6,504,053 $ 10,149,778 $ 10,149,778 $ 9,198,627 $ 1,439,750 $ 1,599,600 $ 1,653,828

100,001-1,000,000

$ 312,631,164 $ 312,631,164 $ 268,100,910 $ 268,100,910 $ 268,100,910 $ 16,835,071 $ 16,835,071 $ 50,584,105

$ 23,343,166 $ 23,343,166 $ 40,762,901 $ 40,762,901 $ 40,762,901 $ 4,050,692 $ 4,050,692 $ 6,008,680

$ - $ - $ 69,107 $ 69,107 $ 7,263,436 $ 1,459,396 $ 12,597,315 $ 9,572

$ 388,505 $ 388,505 $ 10,542,021 $ 10,542,021 $ 2,436,597 $ 935,117 $ 1,009,510 $ 769,897

$ 53,241,841 $ 53,241,841 $ 76,618,275 $ 76,618,275 $ 69,191,945 $ 6,712,677 $ 7,838,411 $ 11,554,262

Exhibit 6-2 continued

Average Compliance Technology Costs (Treatment Train 9 through 16)

NOTE:

1) Refer to Exhibit 6-1 for a description of treatment train technologies.

2) Average costs per size category are based on median population and associated flows, assuming one entry point per system.
Size Category 17 18 19 20 21 22 23

3,300-10,000

$ 2,495,535 $ 2,495,535 $ 3,803,627 $ 3,803,627 $ 3,173,443 $ 1,644,085 $ 562,676

$ 8,922 $ 43,567 $ 219,658 $ 219,658 $ 822,852 $ 586,793 $ 861,662

$ 120,582 $ 120,582 $ 4,624 $ 4,624 $ - $ - $ -

$ 43,485 $ 43,485 $ 36,409 $ 36,409 $ - $ - $ -

$ 299,350 $ 333,995 $ 615,539 $ 615,539 $ 1,274,679 $ 820,874 $ 941,775

10,001-50,000

$ 9,160,742 $ 9,160,742 $ 15,997,473 $ 15,997,473 $ 13,884,129 $ 7,198,773 $ 2,462,155

$ 33,090 $ 165,678 $ 1,075,859 $ 1,075,859 $ 3,866,644 $ 2,643,298 $ 3,842,689

$ 271,621 $ 271,621 $ 6,097 $ 6,097 $ - $ - $ -

$ 67,770 $ 67,770 $ 175,430 $ 175,430 $ - $ - $ -

$ 991,208 $ 1,123,796 $ 2,761,913 $ 2,761,913 $ 5,843,432 $ 3,668,241 $ 4,193,244

50,001-100,000

$ 19,339,675 $ 19,339,675 $ 38,371,441 $ 38,371,441 $ 34,069,251 $ 17,673,110 $ 6,042,288

$ 70,123 $ 350,577 $ 2,834,902 $ 2,834,902 $ 9,909,392 $ 6,602,335 $ 9,539,669

$ 548,757 $ 548,757 $ 8,799 $ 8,799 $ - $ - $ -

$ 117,662 $ 117,662 $ 461,046 $ 461,046 $ - $ - $ -

$ 2,065,112 $ 2,345,566 $ 6,918,771 $ 6,918,771 $ 14,760,087 $ 9,118,589 $ 10,399,955

100,001-1,000,000

$ 139,484,072 $ 139,484,072 $ 312,631,164 $ 312,631,164 $ 239,916,151 $ 124,585,586 $ 42,558,851

$ 497,678 $ 2,488,884 $ 23,343,166 $ 23,343,166 $ 76,696,105 $ 48,323,042 $ 68,900,160

$ 3,945,878 $ 3,945,878 $ 41,919 $ 41,919 $ - $ - $ -

$ 699,342 $ 699,342 $ 3,790,974 $ 3,790,974 $ - $ - $ -

$ 14,735,792 $ 16,726,998 $ 56,648,268 $ 56,648,268 $ 110,854,767 $ 66,061,227 $ 74,959,583

Exhibit 6-2 continued

Average Compliance Technology Costs (Treatment Train 17 through 23)

NOTE:

1) Refer to Exhibit 6-1 for a description of treatment train technologies.

2) Average costs per size category are based on median population and associated flows, assuming one entry point per system.
Size Category 17 18 19 20 21 22 23

< 100

$ 39,477 $ 39,477 $ 49,780 $ 49,780 $ 26,357 $ 13,619 $ 4,671

$ 5,614 $ 6,431 $ 2,762 $ 2,762 $ 5,420 $ 4,433 $ 6,725

$ 32,187 $ 32,187 $ 3,500 $ 3,500 $ - $ - $ -

$ 7,404 $ 7,404 $ 584 $ 584 $ - $ - $ -

$ 19,782 $ 20,599 $ 8,375 $ 8,375 $ 9,172 $ 6,372 $ 7,390

101-500

$ 83,934 $ 83,934 $ 210,637 $ 210,637 $ 152,478 $ 78,866 $ 27,027

$ 10,099 $ 13,220 $ 9,793 $ 9,793 $ 34,134 $ 26,552 $ 39,804

$ 37,318 $ 37,318 $ 3,500 $ 3,500 $ - $ - $ -

$ 7,447 $ 7,447 $ 1,712 $ 1,712 $ - $ - $ -

$ 28,991 $ 32,113 $ 31,719 $ 31,719 $ 55,844 $ 37,781 $ 43,652

501-1000

$ 132,451 $ 132,451 $ 485,414 $ 485,414 $ 374,156 $ 193,617 $ 66,325

$ 16,999 $ 15,164 $ 23,236 $ 23,236 $ 87,479 $ 66,321 $ 98,815

$ 46,083 $ 46,083 $ 3,500 $ 3,500 $ - $ - $ -

$ 7,713 $ 7,713 $ 3,888 $ 3,888 $ - $ - $ -

$ 41,565 $ 39,729 $ 73,274 $ 73,274 $ 140,750 $ 93,888 $ 108,258

1,001-3,300

$ 770,479 $ 770,479 $ 1,302,755 $ 1,302,755 $ 1,049,843 $ 543,574 $ 186,123

$ 35,971 $ 21,577 $ 67,590 $ 67,590 $ 258,026 $ 189,924 $ 280,998

$ 70,291 $ 70,291 $ 3,665 $ 3,665 $ - $ - $ -

$ 18,846 $ 18,846 $ 11,170 $ 11,170 $ - $ - $ -

$ 134,179 $ 119,786 $ 202,077 $ 202,077 $ 407,500 $ 267,317 $ 307,497

Exhibit 6-2 continued

Average Compliance Technology Costs (Treatment Train 17 through 23)

NOTE:

1) Refer to Exhibit 6-1 for a description of treatment train technologies.

2) Average costs per size category are based on median population and associated flows, assuming one entry point per system.
Chapter 6, Cost Analysis 6-11 Proposed Arsenic in Drinking Water Rule RIA

6.2.3 Monitoring and Administrative Costs

Monitoring Costs

Monitoring under the existing arsenic standard occurs annually for surface water systems, and

triennially for ground water systems. Currently, when triggered by a violation the system must

perform three additional tests within the month. Under the proposed rule to be promulgated in

January 2001, systems will still perform monitoring annually (for surface water systems) or every

three years (for ground water systems); however, when triggered by a violation, the system will

perform quarterly monitoring rather than three more samples in one month. All large systems

must comply no later than three years after promulgation (by December 31, 2004). Small systems

must comply within five years of promulgation. Specifically, small surface water systems must

comply by December 31, 2006, and small ground water systems must comply by December 31,

2007.

If quarterly monitoring is required it will continue until the State determines that the system is

“reliably and consistently” below the MCL. States are able to make this determination after

ground water systems have taken two quarterly samples and surface water systems have taken

four quarterly samples. Additionally, States may grant a nine year monitoring waiver to qualifying

systems, an option not previously available. To be eligible for a waiver, a system must meet the

following criteria:

1. Demonstrate adequate source water protection;

2. Demonstrate that the arsenic is naturally occurring;

3. Demonstrate that three previous samples were below the MCL.

The proposed requirements will impose new costs for some systems as follows:

• NTNCs will incur the full costs of the monitoring requirements for the first time, unless

they are located in States that already require NTNCs to monitor for arsenic. For NTNCs

that are currently required to monitor for arsenic, the incremental monitoring costs will

depend on how the proposed national requirements compare with the current State

requirements. (It is assumed that states currently require NTNCs to monitor using the

ground water requirements. It is also assumed that NTNCs will continue to follow the

ground water requirements under the revised rule.)

• CWSs may incur additional costs if they find exceedances more frequently at the proposed

MCL. 

The cost of monitoring includes preparing and analyzing the sample. Collecting the sample,

arranging for delivery to the laboratory, and reviewing the results of the analysis is assumed to

require one hour of the system operator’s time (at an estimated cost of $28 per hour). EPA has

assumed that all systems are equipped to collect samples. Therefore, no additional costs are

assumed for installing taps, re-piping of wells or other investments to permit sampling. EPA has

assumed that systems will utilize one of two laboratory methods: 1) stabilized temperature

platform graphite furnace atomic absorption (STP-GFAA) or 2) graphite furnace atomic
Chapter 6, Cost Analysis 6-12 Proposed Arsenic in Drinking Water Rule RIA

absorption (GFAA). Both techniques cost $40 per sample. 

Total net monitoring costs were estimated over a 20 year period at discount rates of three and

seven percent. The net costs are equal to the difference between the cost of the proposed

monitoring requirements and the cost of the current monitoring requirements. Cost and hour

burden, to the system and the State are listed below in Exhibit 6-4. The cost of routine

monitoring, triggered monitoring, waiver application and public notification are all included in the

total system costs. Miscellaneous costs related to sending samples to be analyzed and sending

public notification to customers are also included in the system cost.

During the first year of implementation all systems will incur costs related to routine monitoring. 

In addition, systems in violation will incur cost related to triggered quarterly monitoring. Under

the revised rule, a percentage of the systems will have monitoring waivers in subsequent years

when monitoring is required Monitoring waivers are not granted under the existing rule,

therefore the number of systems required to conduct routine monitoring under the revised rule is

less than that under the existing rule. For this reason, the annual net cost of monitoring between

the revised rule and the existing rule may be negative, or less expensive, after the initial year of

implementation. The inputs and methodology associated with this analysis are presented in detail

in the Information Collection Request for the Proposed Arsenic in Drinking Water Rule (EPA

,1999)

Administrative Costs

States and systems will incur administrative costs to implement the revised arsenic program

proposed under the Arsenic Rule. States and systems will need to allocate time for their staff to

establish and maintain the programs necessary to comply with the revised arsenic standard and the

new monitoring requirements. Exhibit 6-3(a) lists the one-time state activities involved in starting

up the program following promulgation of the proposed rule. For example, start-up activities

may include developing and adopting state regulations that meet the new Federal arsenic

requirements. Resources are estimated in terms of full time equivalents (FTEs), which EPA has

assumed to cost $64,480 per FTE, including overhead and fringe. Systems also have start-up

costs for reviewing the regulation and training operators. Exhibit 6-3(b) lists the one-time system

start-up activities. The two primary activities that systems will perform to comply with the

revised arsenic rule are reading and understanding the rule and operator training. For all systems

the estimated time required to review the rule is eight hours. Systems serving fewer than 10,000

people have an estimated time of 16 hours to train operators; the estimated time for systems

serving more than 10,000 people is 32 hours. The rate for all start-up activities for systems

serving fewer than 10,000 people is $15.03 per hour and $29.03 per hour for systems serving

more than 10,000 people.

States will also be required to spend time responding to systems that report MCL exceedances or

systems that request a waiver (Exhibit 6-4). Hour burdens for States to review waiver

applications, record monitoring of a sample, and issue a violation letter are the same for small and

large systems. The number of hours required to review a single permit is twice as large for

systems serving more than 10,000 people than for systems serving less than 10,00 people. The
Chapter 6, Cost Analysis 6-13 Proposed Arsenic in Drinking Water Rule RIA

unit cost for all activities is consistent across all activities and size categories ($41.47 per hour)

(EPA, 1997). 

The number of hours required at the system level to perform the responsibilities related to

monitoring are the same for systems serving fewer than 3,300 people and systems serving more

than 3,300 people. However, the hourly rate for systems serving more than 3,300 people is

almost double ($29.03) the rate for systems serving fewer than 3,300 people ($15.03).

Exhibit 6-3 (a)

Estimated One-Time State Resources Required for Initiation of the Arsenic Rule

Administrative Activity

Estimated State

Resources (FTE) Estimated Cost

One Time Start-up Activities

Regulation Adoption and Program Development (CWS) 0.5 $32,200

System Training and Technical Assistance (CWS) 1.0 $64,500

System Training and Technical Assistance (NTNC) 1.0 $64,500

Staff Training (CWS) 0.23 $14,800

Subtotal CWS Costs 1.73 $111,500

Subtotal NTNCs Cost 1.0 $64,500

National Total* CWS Costs 100.34 $6,467,000

National Total* NTNCWS Costs 58.0 $3,741,000

*National totals include estimates for all states, territories, and tribes.

Exhibit 6-3 (b)

Estimated One-Time System Resources Required for Initiation of the Arsenic Rule

System Size Category < 10,000 people > 10,000 people

One Time Start-up Activity Hours Rate Hours Rate

Reading and Understanding

Rule

8 $15.03 8 $29.03

Operator Training 16 $15.03 32 $29.03
Chapter 6, Cost Analysis 6-14 Proposed Arsenic in Drinking Water Rule RIA

Exhibit 6-4

Unit Resources Required for Monitoring, Implementation, and Administration*

System Size Category < 10,000 people > 10,000 people

State Activity Hours Rate Hours Rate

Review a waiver application 8 $41.47 8 $41.47

Record monitoring of a

sample result

1 $41.47 1 $41.47

Issue a single violation letter 4 $41.47 4 $41.47

Review a single permit 16 $41.47 16 $41.47

<3,000 people >3,300 people

System Activity Hours Rate Hours Rate

Apply for a waiver 16 $15.03 16 $29.03

Take a sample 1 $15.03 1 $29.03

Report a sample 1 $15.03 1 $29.03

Prepare and Send Public

Notification

8 $15.03 8 $29.03

*Estimates are provided in May 1999 dollars, updated from 1997 dollars using the CPI-U for all items. 

Source: Information Collection Request for the Public Water System Supervision Program. 

6.2.4 Predicting Compliance Decisions (Compliance Decision Tree)

There is substantial variability in how systems will elect to comply with the Arsenic Rule. Choices

of compliance method will vary depending on baseline source water arsenic concentrations,

system size and location, types of treatment currently in place, and availability of alternative

sources. In addition, the source water pH, total dissolved solids, sulfides and other salts can

change the effectiveness of technologies in removing arsenic. 

The RIA reflects this variability by predicting a range of compliance responses for different system

types and sizes. The compliance decision tree specifies the percentage of systems in different

categories that will choose specific compliance options, given the removal required by the MCL

option and the baseline occurrence of arsenic in source water. For example, for a target MCL of

10 μg/L, the decision tree specifies the probability of different compliance choices for systems

with different baseline influent concentrations (e.g., <10 μg/L, 10-20 μg/L, etc.), different sizes

(e.g., population < or > 1,000), different sources (ground water or surface water), and different

existing treatment facilities. The compliance choices are defined by a treatment technology and

(where relevant) a waste disposal option, and/or pre-treatment technology.

EPA reviewed a draft of the compliance decision tree at an American Water Works Association

(AWWA) technical workgroup meeting in February 1999, and made revisions based on the

comments received at that meeting. The final compliance decision tree, as well as a discussion of
Chapter 6, Cost Analysis 6-15 Proposed Arsenic in Drinking Water Rule RIA

the assumptions made during its development, is provided in Appendix A (“Cost Analysis

Appendix”) by system size and type.

6.2.5 Calculating Costs

Different methods were used to assess costs for three different categories of systems. A MonteCarlo simulation model (SafeWaterXL) was used to estimate costs for community water systems,

excluding the largest CWSs. A deterministic spreadsheet analysis was performed for NTNC

water systems, while a separate case-by-case analysis were performed for the very large systems

(serving more than one million people) that are expected to exceed one or more MCL options in

the baseline. The costs for the three system categories were then summed to calculate total

national costs. The methodology for calculating the costs for each of these system categories is

described separately below, beginning with a description of the SafeWaterXL model.

CWS Costs

The national cost of compliance across CWSs (except those serving over one million people) was

estimated using SafeWaterXL, a Monte-Carlo simulation model developed in Microsoft Excel©

using the Crystal Ball© Monte-Carlo simulation add-in. SafeWaterXL forecasts a distribution of

costs around the mean compliance cost expected for each system size category. The Monte-Carlo

provides the flexibility to incorporate as much data as is available, while maintaining uncertainty

bounds to prevent any individual input from skewing the results. When sample data is not

available as single point estimates, this technique is an invaluable tool.

Historically most drinking water regulatory impact analyses used point-estimates to describe the

average system-level costs. By using SafeWaterXL, this analysis contains more detailed

descriptions of system-level cost. SafeWater XL describes system-level costs in terms of a

distribution. From the distribution, mean and median costs are available, as well as percentile

costs. 

Model Structure

SafeWaterXL determines regulatory compliance costs for individual systems and subsequently

calculates a national average based on the mean value of these data points. To do so, each system

is assigned a random concentration from an occurrence distribution. This system concentration is

distributed across the number of sites of possible contamination for that system. The average

number of sites per system is determined based on the distribution of system intake sites for the

size category as estimated from the CWSS. However, SafeWaterXL does not assume that all

sites are equally likely to exceed the MCL standard. The likelihood of contamination is

determined on a site-by-site basis. The sum of the mean arsenic concentration of all sites within a

system must equal the mean arsenic concentration of the system. Given this upper bound, each

site is assigned a concentration based on the assumed relative standard deviation (RSD) around

the mean system occurrence. 

The model then compares the concentration at each site to the proposed MCL standard; no costs

are incurred for those sites whose concentrations fall below the specified MCL. If the site is
Chapter 6, Cost Analysis 6-16 Proposed Arsenic in Drinking Water Rule RIA

determined to be in violation of the MCL, then SafeWaterXL calculates the percent reduction in

arsenic concentration required to reduce the site concentration to 80 percent of the MCL standard

(this is a safety factor which includes a 20 percent excess removal to account for system overdesign). A treatment train is then assigned to the site based on a decision tree for the size and

type of the system. The decision tree and the selected treatment train reflect the removal

efficiencies of the chosen technology. For example, a technology is chosen based on matching the

removal efficiencies and the percentage removal required at the site (SafeWaterXL identifies three

categories of required removal: < 50 percent, 50-90 percent, > 90 percent).

In this manner, capital and O&M costs are calculated at the site level for the selected treatment

train. The system’s cost of compliance is then determined by summing across the treating sites. 

For each system in SDWIS in which a violation is expected, a cost is calculated with this method,

thereby creating an estimate of national compliance costs. Since household costs are also

calculated for each system, a similar distribution of the cost of compliance at the household level

are also created.

In order to develop more detailed results the compliance decision tree is employed at the site

level, so that only those sites requiring treatment would incur costs. The resulting total national

compliance cost is expected to be a truer representation of the impact of the Arsenic Rule on

systems. The sections below will describe the data needed to develop cost estimates for the entire

universe of systems affected by the Arsenic Rule. After the discussion of data requirements, the

SafeWaterXL model is described as it is used for this rule

Model Inputs

Number of Systems: The universe of public and private ground and surface water systems is

taken from Safe Drinking Water Information System (SDWIS), EPA's national regulatory

database for the drinking water program. Based on data extracted December 1998, a total of

54,352 CWSs and 20,255 NTNCs are subject to the new requirements proposed under the

Arsenic Rule. It is necessary to compile this data by system size, water source, and ownership, as

costs may vary by these characteristics. SafeWaterXL calculates costs for public and private

systems (the latter also includes “other” or “ancillary” systems), and surface and ground water

systems. A summary table of this breakdown is provided in Chapter 4, “Baseline Analysis.”

Entry points per System: SafeWaterXL estimates each system’s cost of compliance at the

treatment site level. This modeling approach is used because a system may include more than one

treatment site. Entry points are used as a proxy for potential or actual points of treatment. For

example, a given water system may have three entry points: one entry point that currently treats,

while two may not have treatment in place. Data on the distribution of the number of system

entry points for each size category and type was extracted from the Community Water Supply

Survey (CWSS). Linear interpolation was used to estimate values for the number of sites in cases

where there were no survey data (see Chapter 4, “Baseline Analysis”).

Population Served by System: A system’s size is determined by the number of people served by

that system. These numbers were extracted from the SDWIS database (see Chapter 4, “Baseline

Analysis”). Systems are grouped into eight categories to help identify systems with related
Chapter 6, Cost Analysis 6-17 Proposed Arsenic in Drinking Water Rule RIA

Average Flow ' aA@ (Population)

bA

(Equation 1)

Design Flow ' max

2 @ Average Flow

aD@ (Population)

bD

(Equation 2)

characteristics so that any data or resources may be pooled during analysis. SafeWaterXL

recognizes the following size categories: 

• < 100 

• 101-500 

• 501-1000 

• 1,001-3,300 

• 3,301-10,000 

• 10,001-50,000 

• 50,001-100,000 

• 100,001- 1,000,000

Flow Rate Parameters: System size is further defined by its flow, which is calculated as a power

law function of the population served. These functions were derived by EPA, and their derivation

can be found in the Model Systems report (Geometries and Characteristics of Public Water

Systems, May 1999, EPA pending). The equation form is shown below.

Where: aA, bA, aD, bD = the regression parameters derived for flow vs. 

population

Population = the population served by the appropriate system type and 

primary source. 

The regression parameters used in the cost model are provided in Exhibit 6-5. Values are

provided for design and average flow for public and private ground water and surface water

supplies. SafeWaterXL divides system design flow and average daily flow equally among all entry

points. Treatment costs are only assigned to the minimum portion of flow that must be treated in

order to achieve the new concentration standard, a process referred to as “blending”.
Chapter 6, Cost Analysis 6-18 Proposed Arsenic in Drinking Water Rule RIA

a b a b

Ground Water

Public 0.08558 1.05840 0.54992 0.95538

Private 0.06670 1.06280 0.41682 0.96078

Public-Purch 0.04692 1.10190 0.31910 0.99460

Private-Purch 0.05004 1.08340 0.32150 0.97940

Surface Water

Public 0.14004 0.99703 0.59028 0.94573

Private 0.09036 1.03340 0.35674 0.96188

Public-Purch 0.04692 1.11020 0.20920 1.04520

Private-Purch 0.05004 1.08340 0.20580 1.00840

Average Flow Design Flow

Exhibit 6-5

Flow Regression Parameters

by Water Source and System Ownership

3 5 10 20

GW 19.90 12.10 5.43 2.06

SW 6.01 2.90 0.75 0.26

% of systems greater than (ppb)

Source

Exhibit 6-6

Arsenic Occurrence by Water Source

Average Consumption per Household: Household costs depend on the average annual

consumption per residential connection. These mean estimates are provided in Chapter 4,

“Baseline Analysis.” Depending on the system’s characteristics, SafeWaterXL multiplies the

appropriate mean consumption (kgal) with the system’s computed cost per thousand gallons to

arrive at the average annual cost of compliance per household for a community water system.

Mean System Occurrence: Arsenic occurrence data are based on the EPA’s Arsenic Occurrence

in Public Drinking Water Supplies report and are represented by a lognormal distribution. The

distribution is truncated at 50 μg/L, the current arsenic standard, because it is assumed that all

arsenic reductions attributable to the new standard start at the previous standard (i.e. all systems

are currently in compliance with the current standard). Baseline occurrence is distinguished

between ground and surface water systems and is provided in Chapter 4 (“Baseline Analysis”) as a

lognormal distribution. Exhibit 6-6 shows the percent of ground and surface water systems with

arsenic concentrations greater than 3, 5, 10, and 20 parts per billion (ppb).
Chapter 6, Cost Analysis 6-19 Proposed Arsenic in Drinking Water Rule RIA

Fraction of flow treated ' min

(

TreatmentTarget

SiteConcentration

&1) @ (% Site Flow)

% Removal Efficiency

(Equation 4)

Relative Intra-System Standard Deviation of Arsenic Concentrations: The relative intra-system

standard deviation of the site concentrations within a system is calculated using data from a 25

state arsenic occurrence study (“Arsenic Occurrence in Public Drinking Water Supplies,” EPA

1999). SafeWaterXL uses a default value of 0.64. This standard deviation is applied to the mean

system concentration to generate individual entry points concentrations within the system. 

Compliance Decision Trees: The decision trees represent EPA's best estimate of the treatment

train technologies system operators will choose to achieve a particular percentage reduction in

arsenic concentration. Decision trees are specific to the system’s size categories and source

water. These are provided in Appendix A, “Cost Analysis Appendix.”

Removal Efficiencies, Treatment Target, and Blending: Each treatment train is associated with an

arsenic removal efficiency that is assumed to be constant across system types. The removal

efficiencies for the 25 treatment trains available under the Arsenic Rule were presented in Exhibit

6-1. SafeWaterXL employs these efficiencies with the blending principle, to determine the

amount of flow that requires treatment in order for the entry point to meet the treatment target. 

Blending uses the entry point concentration and treatment train removal efficiency to determine

the fraction of flow required to obtain the treatment target. The treatment target is set at 80

percent of the MCL and represents the level to which systems will be over-designed to ensure

compliance with the MCL.

SafeWaterXL employs the blending concept through the following equation at the entry point

level:

Where: Treatment Target = the target MCL with 80% safety factor

Site Concentration = arsenic concentration at the site

% Removal Efficiency = % removal efficiency of treatment train chosen

% Site Flow = % of total flow at that site

Note that the blending technique is used only for the those systems expected to require greater

than 90 percent removal in order to achieve compliance with the new MCL standard. In addition,

SafeWaterXL does not employ this technique for those systems that select treatment trains

involving POE or POU devices.

Equipment Life, Discount Rate and Capitalization Rates: System and State implementation costs

are tracked for a twenty-year period. This time frame was selected for two reasons: 

1) technologies are estimated to have a twenty-year life (which includes replacement for some

technologies with lives shorter than twenty years); 
Chapter 6, Cost Analysis 6-20 Proposed Arsenic in Drinking Water Rule RIA

Ownership Type Size Category Estimated After-Tax 

Cost of Capital

NON-SMALL

Investor owned 10,001-50,000 5.26%

>50,000 5.94%

Publicly owned 10,001-50,000 5.26%

>50,000 5.23%

SMALL

Private 1-500 4.17%

501-10,000 4.17%

Public 1-500 5.10%

501-10,000 5.20%

Source: Development of Cost of Capital Estimates for Public 

Water Systems (Draft Final Report). Prepared for U.S. EPA by 

Apogee/Hagler Bailly, Inc. under subcontract to International 

Consultants, Inc. June 1998.

Exhibit 6-7 

Summary of Recommended Cost of Capital Estimates 

(as of March 1998)

2) water systems often finance their capital improvements over a twenty year period.

Two different adjustments are made in this analysis in order to render future costs comparable

with current costs, reflecting the fact that a cost outlay today is a greater burden than an

equivalent cost outlay sometime in the future. The first adjustment is made when the cost

estimates that are derived are being used as an input in benefit-cost analysis. In this instance,

costs are annualized using a social discount rate so that the costs of each regulatory option can be

directly compared with the annual benefits of the corresponding regulatory option. Annualization

is the same process as calculating a mortgage payment; the result is a constant annual cost to

compare with constant annual benefits. 

The choice of an appropriate social discount rate has been, and continues to be, a very complex

and controversial issue among economists and policy makers alike. Therefore, the Agency

compares costs and benefits using two alternative social discount rates, in part to determine the

effect the choice of social discount rate has on the analysis. The annualized costs of each

regulatory option are calculated and displayed using both a seven percent discount rate required

by the Office of Management and Budget (OMB) and a three percent discount rate which the

Agency believes more closely approximates the true social discount rate.

The second adjustment is made when the cost estimates that are derived are being used as an

input into an economic impact analysis, such as an affordability analysis or an analysis of systemlevel costs or household-level costs. In these cases, rather than use a social discount rate when

determining the annualized costs, an actual cost-of-capital rate is used instead. This rate should

reflect the true after-tax cost of capital water systems face, net of any government grants or

subsidies. The cost of capital rates used in this analysis are shown in Exhibit 6-7 above.
Chapter 6, Cost Analysis 6-21 Proposed Arsenic in Drinking Water Rule RIA

NTNC Costs

The cost for NTNCs is estimated using the mean values for system population for each system

service category, as shown in Chapter Four. As with the CWSs, cost is annualized over a twentyyear period, at discount rates of three and seven percent. Assumptions regarding the monitoring

schedule correspond to the monitoring schedule for small ground water systems, including hour

burdens and hourly labor rates. The remaining assumptions required for determining cost are

described below.

Number of Systems, Sites per System and the Population Served: The non-transient noncommunity water supply treatment decisions are modeled similarly to those for community water

supplies. The number of non-transient non-community water supplies is taken from EPA’s

SDWIS, and include those systems as described in Geometries and Characteristics of Public

Water Supplies. For each service area type, the report lists the number of systems and the

average population served. The non-food manufacturing service area combines 16 categories that

were listed separately in the report. For this service area, the number of systems is the sum of the

16 categories and the average population served is the mean of the individual populations

weighted by the number of corresponding systems. Each of these systems has only a single site.

System Flows and Treatment Choices: For each service area, both design and average flows have

been derived by the Agency using literature values and best engineering judgment. There is no

primary survey data for non-community water systems that is equivalent to the CWSS that

provided data for the community water system flow calculations (Smith, personal

communication). The design flow is used to calculate the treatment capital costs while the

average flow is used in the operating and maintenance cost equations. For the non-transient noncommunity water supplies, one of two treatment technologies was chosen based on the level of

the design flow. For service areas with design flows less than 2,000 gallons per day, POE

activated alumina is used; for all others, centralized activated alumina with 2,000 bed volume is

chosen (Kapadia, 1999a personal communication). Both treatment trains include pre-oxidation

and the centralized activated alumina also includes non-hazardous landfilling of the spent media

(Kapadia, 1999a personal communication). 

Mean Arsenic Occurrence: The arsenic occurrence distribution used for ground water

community water supplies is also used for non-transient non-community water supplies. The

number of systems exceeding the MCL for each service area was calculated from the percent of

the distribution between the MCL and 100 μg/L. For this analysis, 100 μg/L was chosen as the

upper concentration limit because the non-transient non-community supplies have not been

previously regulated and occurrence values above the 50 μg/L regulatory level are possible. 

Removal Efficiencies, Treatment Target, and Blending: The removal efficiency associated with

both POE activated alumina and centralized activated alumina is 95 percent. The NTNC model

uses this efficiency with the blending principle in the case of centralized activated alumina to

determine the amount of flow that requires treatment in order for the site to meet the treatment

target. The treatment target is set at 80 percent of the MCL and represents the level to which

systems will be over-designed to ensure compliance with the MCL. For POE activated alumina 
Chapter 6, Cost Analysis 6-22 Proposed Arsenic in Drinking Water Rule RIA

systems, all the flow is treated which may result in finished water below the treatment target

concentration.

Equipment Life, Discount Rate, and Capitalization Rates: As with the community water

supplies, the system implementation costs are tracked for a 20 year period. For the two service

areas using POE activated alumina, construction and forest service, the equipment is assumed to

last ten years with purchases in year zero and year ten. For the centralized activated alumina the

equipment is estimated to last 20 years. The cost estimates are annualized in the same manner as

those for the community water supplies.

Very Large CWS Costs

EPA evaluated the regulatory costs of compliance for very large systems that would be subject to

the new arsenic drinking water regulation. The nation’s 25 largest drinking water systems (i.e.,

those serving a million people or more) supply approximately 38 million people and generally

account for about 15 to 20 percent of all compliance-related costs. Accurately determining these

costs for future regulations is critical. As a result, EPA has developed compliance cost estimates

for the arsenic and radon regulations for each individual system that serves greater than 1 million

persons. These cost estimates help EPA to more accurately assess the cost impacts and benefits of

the arsenic regulation. The estimates also help the Agency identify lower cost regulatory options

and better understand current water systems’ capabilities and constraints.

The system costs were calculated for the 24 public water systems that serve a retail population

greater than 1 million persons and one public water system that serves a wholesale population of

16 million persons. The following are distinguishing characteristics of these very large systems: 

(1) a large number of entry points from diverse sources; 

(2) mixed (i.e. ground and surface) sources; 

(3) occurrence not conducive to mathematical modeling; 

(4) significant levels of wholesaling; 

(5) sophisticated in-place treatment; 

(6) retrofit costs dramatically influenced by site-specific factors; and 

(7) large amounts of waste management and disposal which can 

 contribute substantial costs. 

Generic models cannot incorporate all of these considerations; therefore, in-depth

characterizations and cost analyses were developed utilizing several existing databases and

surveys. 

The profile for each system contains information such as design and average daily flows,

treatment facility diagrams, chemical feed processes, water quality parameters, system layouts,

and intake and aquifer locations. System and treatment data were obtained from the following

sources: 
Chapter 6, Cost Analysis 6-23 Proposed Arsenic in Drinking Water Rule RIA

3 5 10 20

Phoenix, AZ 1,360,751

Annual cost (3%) $ 4.2 $ 4.1 $ 1.8 $ 0.2

Annual cost (7%) $ 4.8 $ 4.7 $ 2.1 $ 0.2

Houston, TX 2,216,830

Annual cost (3%) $ 4.5 $ 1.6 $ 0.4 $ 0.4

Annual cost (7%) $ 5.3 $ 1.9 $ 0.4 $ 0.4

Los Angeles, CA 3,700,000

Annual cost (3%) $ 2.3 $ 1.8 $ 1.8 $ 1.8

Annual cost (7%) $ 2.3 $ 1.8 $ 1.8 $ 1.8

Population 

Served

MCL (μg/L) Large CWSs

Exhibit 6-8

Annual Treatment Costs for Three Large CWSs Expected to

Undertake or Modify Treatment Practice to Comply with the Arsenic Rule

($ millions)

(1) the Information Collection Rule (1997); 

(2) the Community Water Supply Survey (1995); 

(3) the Association of Metropolitan Water Agencies Survey (1998); 

(4) the Safe Drinking Water Information System (SDWIS); and 

(5) the American Water Works Association WATERSTATS Survey (1997)

While these sources contained much of the information necessary to perform cost analyses, the

Agency was still missing some of the detailed arsenic occurrence data in these large water

systems. Where major gaps existed, especially in ground water systems, occurrence data obtained

from the States of Texas, California, and Arizona, the Metropolitan Water District of Southern

California Arsenic Study (1993), the National Inorganic and Radionuclides Study (EPA, 1984),

and utility data was used. Based on data from the studies, detailed costs estimates were derived

for each of the very large water systems.

Cost estimates were generated for each system at several MCL options. The total capital costs

and operational and maintenance (O&M) costs were calculated using the profile information

gathered on each system, conceptual designs (i.e., vendor estimates and RS Means), and modified

EPA cost models (i.e., Water and WaterCost models). The models were modified based on the

general cost assumptions developed in the Phase I Water Treatment Cost Upgrades (EPA, 1998). 

EPA consulted with the system operators to determine how each system would comply with

various MCL options and to assess the costs of their compliance responses. Preliminary cost

estimates were sent to all of the systems for their review. Approximately 30 percent of the

systems responded by submitting revised estimates and/or detailed arsenic occurrence data. 

Based on the information received, EPA revised the cost estimates for those systems. EPA

developed cost estimates for three very large systems that are expected to have arsenic levels

below 50 μg/L. These systems are located in Houston, TX, Phoenix, AZ, and Los Angeles, CA. 

This analysis resulted in the estimated costs listed in Exhibit 6-8.
Chapter 6, Cost Analysis 6-24 Proposed Arsenic in Drinking Water Rule RIA

6.3 Results

This section presents the results of the national cost analysis. Unless otherwise specified, national

costs are presented in May 1999 dollars throughout this chapter.

6.3.1 National Costs

Exhibit 6-9 shows the total national cost breakdown across the four MCL options for the Arsenic

Rule. The system and state cost components of the total annual compliance costs are presented at

discount rates of three and seven percent. Expected system costs include treatment costs,

monitoring costs, and administrative costs of compliance. State costs include monitoring and

administrative costs of implementation. These cost components are also displayed. Exhibits 6

through 9 and 6 through 10 show the annual national costs of the Arsenic Rule under two

scenarios. Exhibits 6 through 9 shows the costs when both CWSs and NTNCs are required to

comply with an MCL. Exhibits 6 through 10 shows the costs when CWSs are required to comply

with an MCL, and NTNCs are only required to monitor for Arsenic. 

Under the both scenarios, CWS costs are approximately $641 million at the 3 μg/L MCL, $376

million at the 5 μg/L MCL, $162 million at the 10 μg/L MCL, and $61 million at the 20 μg/L

MCL (at a three percent discount rate). State costs associated with CWS administration, at a 3

percent discount rate, are approximately $2.2 million at the 3 μg/L MCL, $1.7 million at the 5

μg/L MCL, $1.5 million at the 10 μg/L MCL, and $1.3 million at the 20 μg/L MCL. 

When compliance with an MCL is required, the cost to NTNCs ranges from $26 million at the 3

μg/L MCL, $16 million at the 5 μg/L MCL, $7 million at the 10 μg/L MCL, and $4 million at the

20 μg/L MCL (at a three percent discount rate). State costs associated with NTNC

administration, at a three percent discount rate, are approximately $1.2 million at the 3 μg/L

MCL, $1.1 million at the 5 μg/L MCL, $1 million at the 10 μg/L MCL, and $1 million at the 20

μg/L MCL. When NTNCs are only required to monitor, their costs are approximately $1 million

across the MCLs (at a three percent discount rate). State costs associated with NTNC

administration under this scenario, at a three percent discount rate, also are approximately $1

million across the MCLs.
Discount Rate 3% 7% 3% 7% 3% 7%

System Costs

Treatment $639.2 $746.4 $25.2 $30.5 $664.4 $777.0

Monitoring/ 

Administrative

$2.2 $3.0 $1.0 $1.2 $3.2 $4.2

State Costs $1.6 $1.9 $0.8 $0.9 $2.4 $2.9

TOTAL COST $643.1 $751.4 $27.0 $32.7 $670.1 $784.0

System Costs

Treatment $374.0 $436.0 $14.7 $17.8 $388.7 $453.8

Monitoring/ 

Administrative

$2.0 $2.8 $1.0 $1.2 $3.0 $3.9

State Costs $1.3 $1.6 $0.8 $0.9 $2.1 $2.5

TOTAL COST $377.3 $440.4 $16.4 $19.8 $393.8 $460.2

System Costs

Treatment $160.4 $186.7 $6.1 $7.4 $166.5 $194.1

Monitoring/ 

Administrative

$1.8 $2.5 $1.0 $1.2 $2.8 $3.7

State Costs $1.1 $1.3 $0.7 $0.8 $1.8 $2.1

TOTAL COST $163.3 $190.5 $7.8 $9.3 $171.1 $199.9

System Costs

Treatment $58.9 $68.3 $2.1 $2.6 $61.0 $70.8

Monitoring/ 

Administrative

$1.7 $2.4 $2.2 $2.4 $3.9 $4.9

State Costs $1.0 $1.2 $0.7 $0.8 $1.7 $2.0

TOTAL COST $61.6 $71.8 $5.0 $5.8 $66.5 $77.6

CWS NTNC

MCL = 10 mg/L

MCL = 20 mg/L

TOTAL

MCL = 3 mg/L

MCL = 5 mg/L

Exhibit 6-9

Annual National System and State Compliance Costs

(CWSs and NTNCs Comply With MCL)

($ millions)
Discount Rate 3% 7% 3% 7% 3% 7%

System Costs

Treatment $639.2 $746.4 -- -- $639.2 $746.4

Monitoring/ 

Administrative

$2.2 $3.0 $0.9 $1.1 $3.1 $4.1

State Costs $1.6 $1.9 $0.6 $0.7 $2.2 $2.6

TOTAL COST $643.1 $751.4 $1.5 $1.8 $644.6 $753.2

System Costs

Treatment $374.0 $436.0 -- -- $374.0 $436.0

Monitoring/ 

Administrative

$2.0 $2.8 $0.9 $1.1 $2.9 $3.9

State Costs $1.3 $1.6 $0.6 $0.7 $2.0 $2.3

TOTAL COST $377.3 $440.4 $1.6 $1.8 $378.9 $442.2

System Costs

Treatment $160.4 $186.7 -- -- $160.4 $186.7

Monitoring/ 

Administrative

$1.8 $2.5 $1.0 $1.1 $2.8 $3.7

State Costs $1.1 $1.3 $0.6 $0.7 $1.7 $2.1

TOTAL COST $163.3 $190.5 $1.6 $1.9 $164.9 $192.4

System Costs

Treatment $58.9 $68.3 -- -- $58.9 $68.3

Monitoring/ 

Administrative

$1.7 $2.4 $1.0 $1.1 $2.7 $3.5

State Costs $1.0 $1.2 $0.7 $0.7 $1.6 $1.9

TOTAL COST $61.6 $71.8 $1.6 $1.9 $63.2 $73.7

MCL =20 mg/L

CWS

MCL = 3 mg/L

MCL =5 mg/L

MCL = 10 mg/L

NTNC* TOTAL

Exhibit 6-10

National Annual System and State Compliance Costs

(CWSs Comply With MCL / NTNCs Monitor)

($ millions)
Chapter 6, Cost Analysis 6-27 Proposed Arsenic in Drinking Water Rule RIA

3 5 10 20

<100 $ 22.5 $ 13.9 $ 6.3 $ 2.4

101-500 $ 66.7 $ 41.0 $ 17.9 $ 6.9

501-1,000 $ 35.6 $ 21.8 $ 9.5 $ 3.6

1001-3300 $ 83.4 $ 49.0 $ 21.2 $ 7.9

3,301-10,000 $ 93.9 $ 53.9 $ 23.2 $ 8.3

10,001-50,000 $ 166.8 $ 96.2 $ 40.6 $ 14.3

50,001-100,000 $ 59.3 $ 34.0 $ 14.2 $ 5.0

100,001-1,000,000 $ 100.0 $ 56.6 $ 23.5 $ 8.0

1,000,000 + $ 11.0 $ 7.6 $ 4.0 $ 2.4

<100 $ 24.8 $ 15.3 $ 6.9 $ 2.6

101-500 $ 73.5 $ 45.1 $ 19.7 $ 7.6

501-1,000 $ 40.2 $ 24.7 $ 10.7 $ 4.1

1001-3300 $ 96.7 $ 56.7 $ 24.5 $ 9.1

3,301-10,000 $ 113.7 $ 65.1 $ 28.0 $ 10.0

10,001-50,000 $ 199.6 $ 115.2 $ 48.6 $ 17.1

50,001-100,000 $ 70.6 $ 40.5 $ 16.9 $ 6.0

100,001-1,000,000 $ 114.9 $ 65.0 $ 27.0 $ 9.2

>1,000,000 $ 12.4 $ 8.5 $ 4.4 $ 2.5

3% Discount Rate

7% Discount Rate

System Size

MCL (μg/L)

Exhibit 6-11

Total Annual CWS Treatment Costs Across MCL Options

by System Size and Type

($ millions)

6.3.2 Costs by System Size and Type

This section presents the overall national compliance costs for water systems and for states at

three and seven percent discount rates. Exhibits 6-11 and 6-12 show a detailed breakout of

treatment and monitoring and administrative costs, respectively, by system type and size for the

various MCLs.
Chapter 6, Cost Analysis 6-28 Proposed Arsenic in Drinking Water Rule RIA

3 5 10 20

<100 $ 0.5 $ 0.5 $ 0.4 $ 0.4

101-500 $ 0.5 $ 0.5 $ 0.5 $ 0.5

501-1,000 $ 0.2 $ 0.2 $ 0.1 $ 0.1

1001-3300 $ 0.2 $ 0.2 $ 0.2 $ 0.2

3,301-10,000 $ 0.3 $ 0.2 $ 0.2 $ 0.2

10,001-50,000 $ 0.3 $ 0.3 $ 0.2 $ 0.2

50,001-100,000 $ 0.1 $ 0.1 $ 0.04 $ 0.03

100,001-1,000,000 $ 0.1 $ 0.1 $ 0.04 $ 0.03

<100 $ 0.6 $ 0.6 $ 0.6 $ 0.6

101-500 $ 0.7 $ 0.7 $ 0.7 $ 0.7

501-1,000 $ 0.2 $ 0.2 $ 0.2 $ 0.2

1001-3300 $ 0.3 $ 0.3 $ 0.3 $ 0.3

3,301-10,000 $ 0.4 $ 0.3 $ 0.3 $ 0.3

10,001-50,000 $ 0.4 $ 0.4 $ 0.3 $ 0.3

50,001-100,000 $ 0.1 $ 0.1 $ 0.1 $ 0.05

100,001-1,000,000 $ 0.1 $ 0.1 $ 0.1 $ 0.04

System Size

MCL (μg/L)

3% Discount Rate

7% Discount Rate

Exhibit 6-12

Total Annual CWS Monitoring and Administrative Costs Across MCL Options

by System Size and Type ($ millions)
Chapter 6, Cost Analysis 6-29 Proposed Arsenic in Drinking Water Rule RIA

3 93,886 366,195 355,994 1,006,599 1,623,698 3,254,167 1,452,752 3,084,826

5 58,654 229,192 223,048 626,510 1,012,724 2,084,853 905,886 1,806,388

10 26,856 103,290 102,186 290,138 477,938 997,914 465,003 936,602

20 10,525 41,357 40,811 117,842 195,671 405,714 188,798 364,907

<100 101-500 501-1,000 1,001-

3,300

3,301-

10,000

10,001-

50,000

50,001-

100,000

100,001-

1,000,000

Exhibit 6-13

Number of Households in CWSs Expected to Treat

by Size Category and MCL (μg/L) Option

6.3.3 Costs per Household

Household level costs are considered a good proxy for the affordability of rule compliance with

regard to CWSs, since water systems recover costs at the household level through increased

water rates. This of course assumes that non-residential customers of water systems, such as

businesses, can pass along any increase in water costs to their customers through increased prices

on their goods or services. In order to calculate the number of households served by systems that

will treat, the expected number of treating systems is multiplied by the average number of

households per system (varies by system type and size). Exhibit 6-13 presents the total number of

households served by CWS that treat, by size category.

SafeWaterXL determines household costs separately for each affected CWS, by first dividing the

CWSs annual compliance cost by the CWS’s average daily flow (1,000 gallons per day), and then

multiplied by 365 days to determine the CWS’s cost of compliance per 1,000 gallons produced. 

Finally, the CWS’s cost of compliance per 1,000 gallons (kgal) is multiplied by the average annual

consumption per residential connection (kgal), to arrive at the average annual cost of compliance

per household for the CWS. The estimates of average annual consumption per residential

connection used in this analysis are provided in Chapter 4, “Baseline Analysis.”

Given expected household costs for each individual system, the average is then calculated for each

size category. Exhibit 6-14 shows the average annual household costs by system size, across the

four regulatory options. 

The range of household costs for the MCL of 5 μg/L ranges from less than $2 to approximately

$373; the costs for the MCL of 3 μg/L range from less than $3 to $374; the costs for the MCL of

10 μg/L, range from less than $1 to $378; and the costs for the MCL of 20 μg/L, range from less

than $1 to $398.

Exhibits 6–15 through 6-18 compare the distribution of annual household costs across public

water systems serving fewer than 10,000 people, for MCLs 3, 5, 10, and 20, respectively. The

exhibits demonstrate the maximum annual costs that different percentages of households in

treating systems face. Comparison of Exhibits 6-15 through 6-18 illustrates that regulatory

compliance costs decrease across MCLs. This observation is depicted by the consistent shift to

the left of cost curves across system size categories, when comparing incremental increases in the

MCL. 
Chapter 6, Cost Analysis 6-30 Proposed Arsenic in Drinking Water Rule RIA

3 5 10 20

<100 $368.13 $363.65 $357.17 $348.72

101-500 $258.68 $253.64 $246.38 $237.67

501-1,000 $106.07 $103.74 $98.35 $93.25

1,001-3,300 $63.61 $60.38 $56.51 $51.80

3,301-10,000 $44.28 $40.77 $37.04 $32.52

10,001-50,000 $36.39 $33.22 $29.13 $24.99

50,001-100,000 $29.52 $26.64 $22.80 $19.44

100,001-1,000,000 $23.47 $21.20 $18.32 $15.41

1,000,000 + $2.70 $1.73 $0.89 $0.55

All categories $43.73 $39.18 $33.05 $23.62

MCL (μg/L)

SIZE CATEGORIES

Exhibit 6-14

Mean Annual Household Costs Across MCL Options by System Size
Chapter 6, Cost Analysis 6-31 Proposed Arsenic in Drinking Water Rule RIA

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

$0 $100 $200 $300 $400 $500 $600

Maximum Annual Household Treatment Costs

Percentage of Households

0-100

101-500

501-1,000

1,001-3,300

3,301-10,000

Exhibit 6-16

Annual Treatment Costs Per Household Across Public GW CWSs

Expected to Treat and Serving < 10,000 People

MCL 5 μg/L

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

$0 $100 $200 $300 $400 $500 $600

Maximum Annual Household Treatment Costs

Percentage of Households

0-100

101-500

501-1,000

1,001-3,300

3,301-10,000

Exhibit 6-15

Annual Treatment Costs Per Household Across Public GW CWSs

Expected to Treat and Serving < 10,000 People

MCL 3 μg/L
Chapter 6, Cost Analysis 6-32 Proposed Arsenic in Drinking Water Rule RIA

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

$0 $100 $200 $300 $400 $500 $600

Maximum Annual Household Treatment Costs

Percentage of Households

0-100

101-500

501-1,000

1,001-3,300

3,301-10,000

Exhibit 6-17

Annual Treatment Costs Per Household Across Public GW CWSs

Expected to Treat and Serving < 10,000 People

MCL 10 μg/L

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

$0 $100 $200 $300 $400 $500 $600

Maximum Annual Household Treatment Costs

Percentage of Households

0-100

101-500

501-1,000

1,001-3,300

3,301-10,000

Exhibit 6-18

Annual Treatment Costs Per Household Across Public GW CWSs

Expected to Treat and Serving < 10,000 People

MCL 20 μg/L
Chapter 6, Cost Analysis 6-33 Proposed Arsenic in Drinking Water Rule RIA
Chapter 7, Comparison of Costs and Benefits 7-1 Proposed Arsenic in Drinking Water Rule RIA

Chapter 7: Comparison of Costs and Benefits

7.1 Introduction

In this RIA, EPA has analyzed the cost and benefits of regulating arsenic concentrations in

drinking water to four different MCL standards. The four options considered reflect increasing

levels of protection against exposure to arsenic in drinking water, employing a range of MCLs

from 20 μg/L to 3 μg/L. As the MCL provisions for the four options become increasingly strict,

the associated costs and benefits also increase incrementally. Chapter 5 (“Benefits Analysis”)

describes in detail the estimated national health benefits of the Arsenic Rule options, while

Chapter 6 (“Cost Analysis”) describes the projected national compliance cost estimates. This

chapter presents a summary and comparison of the national benefits and costs and a costeffectiveness analysis for each of the MCL options.

7.2 Summary of National Costs and Benefits

7.2.1 National Cost Estimates

National compliance costs to PWSs for treatment (both annualized capital and O&M), monitoring

and administrative activities, and costs to states, including any one-time start-up costs, for

regulatory implementation and enforcement, were estimated and described in Chapter 6. The

national costs for community water systems to comply with the four MCL options ranges from

$61.6 million (MCL=20 μg/L) to $643.1 million (MCL=3 μg/L) annually based on a discount rate

of three percent. Assuming a seven percent discount rate, the range of total national cost for

community water systems ranges from $71.8 million to $751.4 million annually. The national cost

of compliance with the Arsenic Rule options for NTNCs is approximately $1.5 million at a 3

percent discount rate, and $2 million at a 7 percent discount rate.

7.2.2 National Benefits Estimates

Chapter 5 contains a detailed summary of the methodology used to estimate a range of national

health benefits from avoided bladder cancer cases as a result of the four Arsenic Rule MCL

options. The dollar value of the estimated health benefits associated with each of the four rule

options were calculated based on lower and upper bound estimates of avoided bladder cancer

cases. Although the value of reducing the risk of lung cancer was estimated, these estimates

contain a great deal of uncertainty. Therefore, only the value of reducing the risk of bladder

cancer will be used in the comparison of benefits and costs. For community water systems that

must install treatment equipment or make other modifications to their treatment processes

resulting in reduced arsenic concentrations, the national benefits range from $7.9 million

(MCL=20 μg/L) to $43.6 million (MCL=3 μg/L) annually, based on the lower bound estimates of

bladder cancer cases avoided. Under the upper bound scenario, the health benefits from avoided

bladder cancer increase from $29.8 million at an MCL of 20 μg/L to $104.2 million annually at an

MCL of 3 μg/L.
Chapter 7, Comparison of Costs and Benefits 7-2 Proposed Arsenic in Drinking Water Rule RIA

7.3 Comparison of Benefits and Costs

This section presents a comparison of total national benefits and costs for each of the Arsenic

Rule options considered. Three separate analyses are considered, including a summary of

benefit/cost ratios and net-benefits, a direct comparison of aggregate national cost and benefits,

and the results of a cost-effectiveness analysis of each regulatory option.

7.3.1 National Net Benefits and National Benefit-Cost Comparison

Exhibit 7-1 describes the net benefits and the benefit/cost ratios under various MCL options for

PWSs at 3 and 7 percent discount rates. Under both the lower and upper bound scenarios of

avoided bladder cancer cases in Exhibit 7-1, the net benefits are negative and decreasing as the

Arsenic Rule MCL options become increasingly more stringent. Similarly, the benefit/cost ratios

are less than one and decrease with each more stringent MCL option. Costs outweigh the

quantified benefits under the four MCL options, with benefit/cost ratios all below one, and range

from 0.07 (MCL=3 μg/L) to 0.48 (MCL=20 μg/L) at a 3 percent discount rate, and from 0.06

(MCL=3 μg/L) to 0.42 (MCL=20 μg/L) at a 7 percent discount rate. Of the MCL options

examined, the net benefits are maximized at an MCL of 20 μg/L. The benefit cost ratio is also

greatest at an MCL of 20 μg/L.
Chapter 7, Comparison of Costs and Benefits 7-3 Proposed Arsenic in Drinking Water Rule RIA

3 5 10 20

Net Benefits $ (599.5) $ (345.6) $ (145.4) $ (53.7)

Benefit/Cost Ratio 0.07 0.08 0.11 0.13

Net Benefits $ (538.9) $ (287.4) $ (111.2) $ (31.8)

Benefit/Cost Ratio 0.16 0.24 0.32 0.48

Net Benefits $ (707.8) $ (408.7) $ (172.6) $ (63.9)

Benefit/Cost Ratio 0.06 0.07 0.09 0.11

Net Benefits $ (647.2) $ (350.5) $ (138.4) $ (42.0)

Benefit/Cost Ratio 0.14 0.20 0.27 0.42

*Costs include treatment, O&M, monitoring, and administrative costs to CWSs, monitoring and 

administrative costs to NTNCWSs, and State costs for administration of water programs.

The lower-end estimate of bladder cancer cases avoided is calculated using the lower-end risk estimate 

(see Exhibit 5-9) and assumes that the conditional probability of mortality among the Taiwanese study group 

was 100 percent. The upper-end estimate of bladder cancer cases is calculated using the upper-end risk 

estimate (see Exhibit 5-9) and assumes that the conditional probability of mortality among the Taiwanese 

study group was 80 percent. upper bound lower bound upper bound

7% Discount Rate

MCL (μg/L)

3% Discount Rate

lower bound

Exhibit 7-1

Summary of Annual National Net Benefits and Benefit-Cost Ratios,

CWSs Comply With MCL and NTNCs Only Monitor*

(Bladder Cancer Cases Only, in $ millions)
Chapter 7, Comparison of Costs and Benefits 7-4 Proposed Arsenic in Drinking Water Rule RIA

$-

$100.00

$200.00

$300.00

$400.00

$500.00

$600.00

$700.00

$800.00

$ millions

Costs $753.16 $442.21 $192.40 $73.72 

Benefits (upper bound) $104.20 $89.90 $52.10 $29.80 

Benefits (lower bound) $43.60 $31.70 $17.90 $7.90 

3 ug/L 5 ug/L 10 ug/L 20 ug/L

Exhibit 7-2

Comparison of Costs and Benefits of Bladder Cancer Cases Avoided

(CWSs Comply with MCL / NTNCs Monitor, 7% Discount Rate)

Exhibit 7-2 graphically depicts the absolute difference between the total value of national costs

and benefits under each proposed MCL at a 7 percent discount rate.

Finally, Exhibit 7-3 shows the results of an analysis in which the average national cost of

achieving each unit reduction in cases of bladder cancer avoided, was calculated. The average

annual cost per cancer case avoided was computed at each MCL option, for both 3 and 7 percent

discount rates. At a 3 percent discount rate, the cost per bladder cancer case ranges from $12.3

million to $29.4 million at an MCL of 3 μg/L, from $8.4 million to $23.8 million at an MCL of 5

μg/L, from $6.3 million to $18.3 million at an MCL of 10 μg/L, and from $4.2 million to $15.9

million at an MCL of 20 μg/L. At a 7 percent discount rate, the cost per bladder cancer case

ranges from $14.4 million to $34.4 million at an MCL of 3 μg/L, from $9.8 million to $27.7

million at an MCL of 5 μg/L, from $7.3 million to $21.4 million at an MCL of 10 μg/L, and from

$4.9 million to $18.6 million at an MCL of 20 μg/L.
Chapter 7, Comparison of Costs and Benefits 7-5 Proposed Arsenic in Drinking Water Rule RIA

Arsenic Level 

(μg/L) lower bound** upper bound**

3 $ 29.4 $ 12.3

5 $ 23.8 $ 8.4

10 $ 18.3 $ 6.3

20 $ 15.9 $ 4.2

3 $ 34.4 $ 14.4

5 $ 27.7 $ 9.8

10 $ 21.4 $ 7.3

20 $ 18.6 $ 4.9

3% Discount Rate

7% Discount Rate

*Costs all treatment, O&M, monitoring, and administrative costs to CWSs, 

monitoring and administrative costs to NTNCWSs, and State costs for 

administration of water programs.

**Lower/upper bounds correspond to estimates of bladder cancer cases avoided.

Exhibit 7-3

Cost per Bladder Cancer Case Avoided for the Proposed Arsenic Rule

(CWSs Comply with MCL / NTNCs Monitor, in $ millions)
Chapter 7, Comparison of Costs and Benefits 7-6 Proposed Arsenic in Drinking Water Rule RIA

7.3.2 Cost-Effectiveness

Cost-effectiveness analysis is another commonly used measure of the economic efficiency with

which regulatory options are meeting the intended regulatory objectives. Exhibit 7-4 is a

comparison of annual national costs (computed at a seven percent discount rate) and annual cases

of bladder cancer avoided at each MCL option. The two lines represent the cost per cancer case

avoided under the lower and upper bound estimates of bladder cancer cases avoided. These

plotted lines depict the trend in marginal cost and benefits (expressed as health effects avoided)

between each point on these curves (corresponding to each MCL option). Points along these

lines represent each increment of cost that is incurred in order to achieve the next increment of

risk reduction, i.e. additional bladder cancer case avoided. The steepness of the curves under

both benefits scenarios suggests that additional increments of risk reduction and benefits are

achieved at increasingly greater cost to the nation.
Chapter 7, Comparison of Costs and Benefits 7-7 Proposed Arsenic in Drinking Water Rule RIA

$-

$100

$200

$300

$400

$500

$600

$700

$800

- 10 20 30 40 50 60

Bladder Cancer Cases Avoided per Year

Annual Cost ($ millions)

based on lower bound estimates of avoided cases based on upper bound estimates of avoided cases

Exhibit 7-4

Comparison of Annual Costs to Cases of Bladder Cancer per Year

(7% Discount Rate)

Exhibit 7-5 further reinforces the fact that as the MCL becomes more stringent, the incremental

cost per cancer case avoided increases. For example, the additional cases of bladder cancer

avoided in moving from an MCL of 10 μg/L to 5 μg/L are achieved at a cost per case of $13

million annually under the high bound and seven percent discount rate scenario. Similarly, in

moving from an MCL of 5 μg/L to a more stringent MCL of 3 μg/L, the cost per case avoided

increases to $44 million per year under this same scenario.

3 μg/L

5 μg/L

10 μg/L

20 μg/L
Chapter 7, Comparison of Costs and Benefits 7-8 Proposed Arsenic in Drinking Water Rule RIA

$-

$10

$20

$30

$40

$50

$60

Incremental Cost per Incremental

Bladder Cancer Case ($ millions)

MCL 20 ug/L $18 $5 

MCL 10 ug/L $24 $11 

MCL 5 ug/L $36 $13 

MCL 3 ug/L $52 $44 

Lower bound estimates of avoided cases Upper bound estimates of avoided cases

Exhibit 7-5

Incremental Cost per Incremental Bladder Cancer Case Avoided

(CWSs, 7% Discount Rate, in $ millions)

7.4 Other Benefits

Exhibit 5-15 provides the estimated benefits associated with the results of the “What-if” scenario

for lung cancer. At an MCL of 5 μg/L, EPA estimates that the potential benefit of reducing the

risk of lung cancer ranges from $35 to $384 million. Also, Chapter 5 discusses a number of

important non-monetized benefits of reducing arsenic exposure. Chief among these are certain

health impacts known to be caused by arsenic (such as skin cancer). In 1988 EPA published a

risk estimate which used the skin cancer data from Taiwan. EPA calculated a Maximum

Likelihood Estimate (MLE) for skin cancer of 3 x10-5 for females and 7 x 10-5 for males drinking

2 liters a day contaminated with 1 μg/L of arsenic. At the current MCL of 50 μg/L and two liters

per day, the risk would be 5x10-3. A number of epidemiologic studies conducted in several

countries (e.g., Taiwan, Japan, England, Hungary, Mexico, Chile, and Argentina) report an

association between arsenic in drinking water and skin cancer in exposed populations. Studies

conducted in the US have not demonstrated an association between inorganic arsenic in drinking

water and skin cancer. However, these studies may not have included enough people in their

design to detect these types of effects. 

The potential monetized benefits associated with skin cancer reduction would not change the total
Chapter 7, Comparison of Costs and Benefits 7-9 Proposed Arsenic in Drinking Water Rule RIA

benefits of the rule to an appreciable degree, even if the assumption were made that the risk of

skin cancer were equivalent to that of bladder cancer, using EPA’s 1988 risk assessment. Skin

cancer is highly treatable (at a cost of illness of less than $3,500 for basal and squamous cell

carcinomas vs. a cost-of-illness of $178,000 for non-fatal bronchitis) in the U.S., with few

fatalities (less than 1%). 

In addition to potentially reducing the risk of skin cancer, there are also a large number of other

health effects associated with arsenic, as presented in Exhibit 5-1, which are not monetized in this

analysis, due to lack of appropriate data. 

Other benefits not monetized in this analysis include customer peace of mind from knowing

drinking water has been treated for arsenic and reduced treatment costs for currently unregulated

contaminants that may be co-treated with arsenic. To the extent that reverse osmosis is used for

arsenic removal, these benefits could be substantial. Reverse osmosis is the primary point of use

treatment, and it is expected that very small systems will use this treatment to a significant extent. 

(These benefits of avoided treatment cannot currently be monetized; however, they can be readily

monetized in the future, as decisions are made about which currently unregulated contaminants to

regulate.)
Chapter 8, Economic Impact Analyses 8-1 Proposed Arsenic in Drinking Water Rule RIA

Chapter 8: Economic Impact Analyses

8.1 Introduction

EPA is required to perform a series of analyses that addresses the distribution of regulatory

impacts associated with the proposed Arsenic Rule. This chapter presents analyses that support

EPA’s compliance with the following federal mandates: 

• Executive Order 12886 (Regulatory Planning and Review);

• Regulatory Flexibility Act (RFA) of 1980, as amended by the Small Business Regulatory

Enforcement Fairness Act (SBREFA) of 1996; 

• National Affordability determination required by the 1996 amendments to the Safe

Drinking Water Act (SDWA); 

• Unfunded Mandates Reform Act (UMRA) of 1995; 

• Technical, Financial, and Managerial Capacity Assessment required by Section 1420(d)(3)

of the 1996 amendments to the Safe Drinking Water Act (SDWA); 

• Executive Order 13045 (Protection of Children From Environmental Health Risks and

Safety Risks); 

• Executive Order 12989 (Federal Actions to Address Environmental Justice in Minority

Populations and Low-Income Populations);

• Paperwork Reduction Act; and

• Health Risk Reduction and Cost Analysis (HRRCA) as required by Section 1412(b)(3)(C)

of the 1996 SDWA Amendments;

• Initial Regulatory Flexibility Analysis (IRFA)

These analyses draw on the cost analyses presented in Chapter 6 and an analysis of administrative

requirements presented in a separate document, Information Collection Request for the Arsenic

Rule. Throughout this chapter, it is assumed that CWSs will have to comply with the newly

proposed MCL, while NTNCs will only have to monitor for Arsenic.

Several of these federal mandates require an explanation of why the rule is necessary, the

statutory authority upon which it is based, and the primary objectives it is intended to achieve. 

Background information on the problems addressed by the proposed rule, and EPA's statutory

authority for promulgating the rule are presented in Chapter 2. In this chapter, Section 8.2

presents the RFA and SBREFA analysis of impacts on small entities. Also described are the

economic impacts of the proposed rule on households. Section 8.3 discusses coordination of the

arsenic rule with other Federal rules. The minimization of economic burden, UMRA, system

capacity assessments, and the Paperwork Reduction Act are addressed in Sections 8.4, 8.5, 8.6

and 8.7, respectively. Section 8.8 discusses the rules’ protection of children’s health, Section 8.9

addresses environmental justice issues and Section 8.10 contains the HRRCA.
Chapter 8, Economic Impact Analyses 8-2 Proposed Arsenic in Drinking Water Rule RIA

8.2 Regulatory Flexibility Act and Small Business Regulatory Enforcement

Fairness Act

8.2.1 Summary of EPA’s Small Business Consultations 

Under the Regulatory Flexibility Act, 5 U.S.C. 601 et seq., as amended by the Small Business

Regulatory Enforcement Fairness Act of 1996, EPA is required to prepare a regulatory flexibility

analysis unless the Agency certifies that a rule will not have “a significant economic impact on a

substantial number of small entities.” If it is determined that the rule will have a significant impact

on a substantial number of small entities the Agency must convene a Small Business Advocacy

Review (SBAR) Panel prior to publication of the proposed rule. The SBAR Panel has 60 days to

consult with small entity representatives (SERs) likely to be impacted by the rule and to make

recommendations designed to reduce the impact of the proposed rule on small entities. The

Agency must consider these recommendations when drafting the proposed rule. 

As required by section 609(b) of the RFA, as amended by SBREFA, EPA also conducted

outreach to small entities and convened a Small Business Advocacy Review Panel to obtain

advice and recommendations of representatives of the small entities that potentially would be

subject to the rule’s requirements. 

EPA identified 22 representatives of small entities, in this situation small systems, that were most

likely to be subject to the proposal. In December, 1998, EPA prepared and distributed to the

small entity representatives (SERs) an outreach document on the arsenic rule titled “Information

for Small Entity Representatives Regarding the Arsenic in Drinking Water Rule” (EPA 1998 ). 

On December 18, 1998, EPA held a SER conference call for small systems from Washington D.C.

to provide a forum for input on key issues related to the planned proposal of the arsenic in

drinking water rule. These issues included, but were not limited to issues related to the rule

development, such as arsenic health risks, treatment technologies, analytical methods, and

monitoring. Fifteen SERs from small water systems participated on the call from the following

States: Alabama, Arizona, California, Georgia, Massachusetts, Montana, Nebraska, New

Hampshire, New Jersey, Utah, Virginia, Washington, and Wisconsin. 

Efforts to identify and incorporate small entity concerns into this rulemaking culminated with the

convening of a SBAR Panel on March 30, 1999, pursuant to section 609 of RFA/SBREFA. The

four person Panel was headed by EPA’s Small Business Advocacy Chairperson and included the

Director of the Standards and Risk Management Division within EPA’s Office of Ground Water

and Drinking Water, the Administrator of the Office of Information and Regulatory Affairs with

the Office of Management and Budget, and the Chief Counsel for Advocacy of the SBA. For a

60-day period starting on the convening date, the Panel reviewed technical background

information related to this rulemaking, reviewed comments provided by the SERs, and met on

several occasions. The Panel also conducted its own outreach to the SERs and held a conference

call on April 21, 1999 with the SERs to identify issues and explore alternative approaches for

accomplishing environmental protection goals while minimizing impacts to small entities. 

Consistent with the RFA/SBREFA requirements, the Panel evaluated the assembled materials and

small-entity comments on issues related to the elements of the IRFA (See section 8.2.1) . A copy
Chapter 8, Economic Impact Analyses 8-3 Proposed Arsenic in Drinking Water Rule RIA

of the June 4, 1999 Panel report is included in the docket for this proposed rule (U.S. EPA,

1999). 

The proposed rule addresses all of the recommendations on which the Panel reached consensus. 

In addition, to help small systems comply with the arsenic rule, EPA is committed to addressing

several other Panel recommendations regarding guidance, which are discussed in detail in the

pages to follow.

Treatment Technologies, Waste Disposal, and Cost Estimates

The Panel recommended the following: further develop the preliminary treatment and waste

disposal cost estimates; fully consider these costs when identifying affordable compliance

technologies for all system size categories; and provide information to small water systems on

possible options for complying with the MCL, in addition to installing any listed compliance

technologies. 

In response to these recommendations the Treatment and Cost document describes: development

of cost estimates for treatment and waste disposal; identification of affordable compliance

technologies, including the consideration of cost; and options for complying with the MCL other

than installing compliance technologies, such as selecting to regionalize.

Regarding POU devices, the Panel recommended the following: continue to promote the use of

POU devices as alternative treatment options for very small systems where appropriate; account

for all costs, including costs that may not routinely be explicitly calculated; consider liability issues

from POU/POE devices when evaluating their appropriateness as compliance technologies; and

investigate waste disposal issues with POE devices. 

In response to these recommendations, EPA will include in the proposed rule’s preamble: an

expanded description regarding available POU compliance treatment technologies and conditions

under which POU treatment may be appropriate for very small systems; a description of the

components which contribute to the POU cost estimates; a discussion that clarifies that water

systems will be responsible for POU operation and maintenance to prevent liability issues from

customers maintaining equipment themselves.

Relevance of Other Drinking Water Regulations

The Panel recommended the following: include discussion of the co-occurrence of arsenic and

radon in the proposed rule for arsenic; take possible interactions among treatments for different

contaminants into account in costing compliance technologies and determining whether they are

nationally affordable for small systems; and encourage systems to be forward-looking and test for

the multiple contaminants to determine if and how they would be affected by the upcoming rules. 

In response, the proposed rule’s preamble will include a discussion on the co-occurrence analysis

of radon and arsenic: the treatment section of the preamble will be expanded to describe the

relationship of treatment for arsenic with other drinking water rules and how this issue was taken
Chapter 8, Economic Impact Analyses 8-4 Proposed Arsenic in Drinking Water Rule RIA

into account in cost estimates. In addition, the preamble will encourage systems to consider other

upcoming rules when making future plans on monitoring or treatment.

Small Systems Variance Technologies and National Affordability Criteria

The Panel recommended the following: include a discussion of the issues surrounding appropriate

adjustment of its national affordability criteria to account for new regulatory requirements;

consider revising its approach to national affordability criteria, to the extent allowed by statutory

and regulatory requirements, to address the concern that the current cumulative approach for

adjusting the baseline household water bills is based on chronological order rather than risk; and

examine the data in the 1995 Community Water Supply Survey to determine if in-place treatment

baselines can be linked with the current annual water bill baseline in each of the size categories for

the proposed rule.

In response to these recommendation, the treatment section of proposed rule’s preamble will

include an expanded discussion about the national affordability criteria and how it may be adjusted

to account for new regulations. In addition, information regarding methodology and rationale will

be added to explain the national affordability approach.

Monitoring and Arsenic Species

The Panel recommended the following: EPA consider allowing States to use recent compliance

monitoring data to satisfy initial sampling requirements or to obtain a waiver; and that EPA

continue to explore whether or not to make a regulatory distinction between organic and

inorganic arsenic based on compliance costs and other considerations. 

In response, the monitoring section of the rule’s preamble and the proposed regulatory language

will describe the allowance of monitoring data that meet analytical requirements and have

reporting limits sufficiently below the revised MCL and collected after 1990. 

Considerations in setting the MCL

The Panel recommended the following: in performing its obligations under SDWA EPA should

take cognizance of the scientific findings, the large scientific uncertainties, the large potential

costs (including treatment and waste disposal costs), and the fact that this standard is scheduled

for review in the future; give full consideration to the provisions of the Executive Order 12866

and to the option of exercising the new statutory authority under SDWA Sections 1412(b)(4)(C)

and 1412(b)(6)(A) in the development of the arsenic rule; and fully consider all of the “risk

management” components of its rulemaking effort to ensure that the financial and other impacts

on small systems are factored into its decision-making processes. The Panel also recommended

that EPA take into account both quantifiable and non-quantifiable costs and benefits of the

standard and the needs of sensitive sub-populations.

In response to all these recommendations, EPA describes in detail the factors that were

considered in setting in the MCL and provides the rationale for this selection. 
Chapter 8, Economic Impact Analyses 8-5 Proposed Arsenic in Drinking Water Rule RIA

Applicability of proposal

The Panel recommended that EPA carefully consider the appropriateness of extending the scope

of the rule to Non-Transient, Non-Community Water Systems (NTNCWSs). 

In response, the arsenic proposal does not apply to NTNCWSs and the MCL section of the rule’s

preamble will describe the basis for this decision, including the incremental costs and benefits

attributable to coverage of these water systems. 

Other Issues

The Panel recommended that EPA encourage small systems to discuss their infrastructure needs

for complying with the arsenic rule with their primacy agency to determine their eligibility for

DWSRF loans, and if eligible, to ask for assistance in applying for the loans. In response, the

UMRA analysis has been expanded to discuss funding options for small systems and to encourage

systems to be proactive in communicating with their primacy agency.

Regarding health effects, the Panel recommended the following: further evaluate the Utah study

and its relationship to the studies on which the NRC report was based and give it appropriate

weight in the risk assessment for the proposed arsenic standard; and examine the NRC

recommendations in the light of the uncertainties associated with the report’s recommendations,

and any new data that may not have been considered in the NRC report. In response to these

recommendations, the benefits analysis includes a discussion of the qualitative benefits evaluation

and use of research data.

8.2.2 Definition of Small Entity for the Arsenic Rule

The Agency has proposed, taken comment, and finalized its intent to define “small entity” as a

public water system that serves 10,000 or fewer persons for purposes of its regulatory flexibility

assessments under the RFA for all future drinking water regulations. (See the Consumer

Confidence Reports Final Rule, 63 FR 44511, Aug. 19, 1998 and Proposed Rule, 63 FR 7620

Feb.13, 1998.) The Agency discussed at length, in the preamble to the proposed Consumer

Confidence rule, the basis for its decision to use this definition and to use a single definition of

small public water system whether the system was a “small business”, “small nonprofit

organization”, or “small governmental jurisdiction.” EPA also consulted with the Small Business

Administration on the use of this definition as it relates to small businesses. The Agency has used

this definition in developing subsequent regulations under the Safe Drinking Water Act. In

defining small entities in this manner, EPA recognizes that baseline conditions in source water and

treatment and operational practices may differ for systems serving fewer than 10,000 people

versus systems serving 10,000 or more persons. 

According to the latest estimates (December 1998) contained in the EPA's public water system

database, Safe Drinking Water Information System (SDWIS), there are 54,352 community water

systems and 20,255 non-transient noncommunity water supplies providing potable water to the

public. Of these, 90 percent of the CWSs (50,776) and nearly all of the NTNCWSs (20,235) are
Chapter 8, Economic Impact Analyses 8-6 Proposed Arsenic in Drinking Water Rule RIA

<100 101-500 501-1,000 1,001-3,300 3,301-10,000

Publicly-Owned:

CWS 1,729 5,795 3,785 6,179 3,649

NCWS 1,783 3,171 1,182 361 29

Privately-Owned:

CWS 13,640 11,266 2,124 1,955 654

NCWS 8,178 4,162 902 411 56

Total Systems:

CWS 15,369 17,061 5,909 8,134 4,303

NCWS 9,961 7,333 2,084 772 85

TOTAL 25,330 24,394 7,993 8,906 4,388

Source: Safe Drinking Water Information System (SDWIS), December 1998 freeze.

Type Water System Size Category

System

Exhibit 8-1

Profile of the Universe of Small Water Systems

Regulated Under the Arsenic Rule

classified by EPA as small entities. Exhibit 8-1 presents a breakdown of the universe of small

water systems by size category, type, and ownership.

Of the total number of small systems governed by the proposed rule, 72 percent of the systems are

CWSs and 28 percent are NTNCWSs. A table of the total number of systems regulated by the

proposed rule is provided in Chapter 4, “Baseline Analysis.”

8.2.3 Requirements for the Initial Regulatory Flexibility Analysis

The Regulatory Flexibility Act requires EPA to complete an Initial Regulatory Flexibility Analysis

(IRFA) addressing the following:

• The need for the rule;

• The objectives of and legal basis for the proposed rule;

• A description of, and where feasible, an estimate of the number of small entities to

which the rule will apply;

• A description of the proposed reporting, record keeping, and other compliance

requirements of the rule, including an estimate of the types of small entities, which

will be subject to the requirements and the type of professional skills necessary for

preparation of reports or records;

• An identification, to the extent practicable, of all relevant federal rules that may

duplicate, overlap, or conflict with the proposed rule; and
Chapter 8, Economic Impact Analyses 8-7 Proposed Arsenic in Drinking Water Rule RIA

MCL 3

GW 3,024 3,256 1,058 1,406 696 434 53 33

SW 62 109 67 137 94 76 16 16

MCL 5

GW 1,898 2,048 671 893 444 286 35 21

SW 32 57 34 70 50 41 8 8

MCL 10

GW 874 934 312 424 218 144 19 11

SW 10 18 11 23 16 13 3 4

MCL 20

GW 343 377 126 177 91 61 8 5

SW 3 5 3 5 5 3 1 1

<100 101-500 501-1,000 1,001-

3,300

3,301-

10,000

10,001-

50,000

50,001-

100,000

100,001-

1,000,000

Table 8-2

Number of CWSs Expected to Undertake or Modify Treatment Practice

• A description of “any significant regulatory alternatives” to the proposed rule that

accomplish the stated objectives of the applicable statutes, and that minimize any

significant economic impact of the proposed rule on small entities. Significant

regulatory alternatives may include:

! Establishing different compliance or reporting requirements or timetables that take

into account the resources of small entities;

! Clarifying, consolidating, or simplifying compliance and reporting requirements

under the rule for small entities;

! Using performance rather than design standards; and

! Exempting small entities from coverage of the rule or any part of the rule.

8.2.4 Small Entity Impacts

The results of the economic impact analysis for small water systems under the MCL options of 3,

5, 10, and 20 μg/L are summarized below. Estimates of the number of small systems expected to

be affected and the cost of complying with each component of the regulatory approach are

presented.

As seen in Exhibit 8-2, at an MCL of 5 μg/L, approximately thirteen percent of community water

systems serving less than 100 people are expected to be affected by the Arsenic Rule. In general,

for the small systems size categories, the Arsenic Rule is expected to affect approximately twelve

percent of the universe of CWSs.

It is useful to put the number of systems affected by the rule in to context by comparing the

number of systems expected to be affected by the promulgation of the Arsenic Rule to the number

of systems not expected to undertake or modify any of their existing treatment practices. Exhibits

8-3, 8-4, 8-5, and 8-6 show these comparisons for MCLs of 3, 5, 10, 20 μg/L.. 
Chapter 8, Economic Impact Analyses 8-8 Proposed Arsenic in Drinking Water Rule RIA

0

1,500

3,000

4,500

6,000

7,500

9,000

10,500

12,000

13,500

15,000

Number of Systems

Treating GW systems 1,898 2,048 671 893 444

Not treating GW systems 12,379 13,010 4,018 4,821 2,015

Treating SW systems 32 57 34 70 50

Not treating SW systems 1,060 1,946 1,186 2,350 1,794

<100 101-500 501-1,000 1,001-3,300 3,301-10,000

Exhibit 8-4

Number of CWSs Expected to Undertake or Modify Treatment Practice

MCL 5 μg/L

0

1,500

3,000

4,500

6,000

7,500

9,000

10,500

12,000

13,500

15,000

Number of Systems

Treating GW systems 3,024 3,256 1,058 1,406 696

Not treating GW systems 11,253 11,802 3,631 4,308 1,763

Treating SW systems 62 109 67 137 94

Not treating SW systems 1,030 1,894 1,153 2,283 1,750

<100 101-500 501-1,000 1,001-3,300 3,301-10,000

Exhibit 8-3

Number of CWSs Expected to Undertake or Modify Treatment Practice

MCL 3 μg/L
Chapter 8, Economic Impact Analyses 8-9 Proposed Arsenic in Drinking Water Rule RIA

0

1,500

3,000

4,500

6,000

7,500

9,000

10,500

12,000

13,500

15,000

Number of Systems

Treating GW systems 874 934 312 424 218

Not treating GW systems 13,403 14,124 4,377 5,290 2,241

Treating SW systems 10 18 11 23 16

Not treating SW systems 1,082 1,985 1,209 2,397 1,828

<100 101-500 501-1,000 1,001-3,300 3,301-10,000

Exhibit 8-5

Number of CWSs Expected to Undertake or Modify Treatment Practice

MCL 10 μg/L

0

1,500

3,000

4,500

6,000

7,500

9,000

10,500

12,000

13,500

15,000

Number of Systems

Treating GW systems 343 377 126 177 91

Not treating GW systems 13,934 14,681 4,563 5,537 2,368

Treating SW systems 3 5 3 5 5

Not treating SW systems 1,089 1,998 1,217 2,415 1,839

<100 101-500 501-1,000 1,001-3,300 3,301-10,000

Exhibit 8-6

Number of CWSs Expected to Undertake or Modify Treatment Practice

MCL 20 μg/L
Chapter 8, Economic Impact Analyses 8-10 Proposed Arsenic in Drinking Water Rule RIA

<100 101-500 501-1,000 1,001-3,300 3,301-

10,000

3

Treatm e n t** $ 7,523 $ 20,551 $ 33,440 $ 58,153 $ 131,121

Monitoring/ 

Adminis tra tive $ 37 $ 37 $ 34 $ 36 $ 76

5

Treatm e n t** $ 7,414 $ 20,163 $ 32,745 $ 54,633 $ 120,330

Monitoring/ 

Adminis tra tive $ 35 $ 35 $ 32 $ 33 $ 69

1 0

Treatm e n t** $ 7,316 $ 19,460 $ 31,018 $ 50,892 $ 109,215

Monitoring/ 

Adminis tra tive $ 34 $ 34 $ 30 $ 30 $ 63

2 0

Treatm e n t** $ 7,124 $ 18,705 $ 29,347 $ 46,472 $ 95,928

Monitoring/ 

Adminis tra tive $ 34 $ 33 $ 29 $ 28 $ 55

*CWS system costs were calculated using a commercial discount rate.

**Treatment cost only applies if system undertakes or modifies treatm ent for arsenic.

MCL (μ g/L)

CWS Size Ca tegory

Exhibit 8-7

Average Annual System Compliance Costs for CWSs*

Exhibit 8-7 details the average system-level annual compliance costs for small systems that are

expected to undertake or modify treatment. As one would expect, the costs, per treating system,

are slightly higher under the most stringent MCL.

Of course, system treatment costs range within size each size catagory. Also, it is important to

look at both absolute compliance costs, as well as compliance costs relative to current operating

expenditures. Using data on total current expenses from the CWSS (1995), EPA developed a

Monte-Carlo simulation model to estimate the effect of increased small system expenditures as a

result of Arsenic Rule compliance. Exhibits 8-8 through 8-17 show the distribution of system

compliance costs, as well as the distribution of the percentage increase in total operating expenses

that will result from the proposed arsenic rule. A separate exhibit is provided for each small size

catagory and each proposed MCL.
Chapter 8, Economic Impact Analyses 8-11 Proposed Arsenic in Drinking Water Rule RIA

$0

$10,000

$20,000

$30,000

$40,000

$50,000

$60,000

$70,000

$80,000

$90,000

10.0% 20.0% 30.0% 40.0% 50.0% 60.0% 70.0% 80.0% 90.0% 95.0% 97.5% 99.9%

Percentage of Systems

Maximum System Expenses

10.0%

100.0%

1000.0%

Percentage Increase in System 

Expenses

After Rule Expenses Baseline Expenses Percent Increase in Expenses

Exhibit 8-9

Comparison of CWS Baseline and Post-Compliance Total Expenses

for Systems Serving <100 People (MCL 5 μg/L)

$0

$10,000

$20,000

$30,000

$40,000

$50,000

$60,000

$70,000

$80,000

$90,000

10.0% 20.0% 30.0% 40.0% 50.0% 60.0% 70.0% 80.0% 90.0% 95.0% 97.5% 99.9%

Percentage of Systems

Maximum System Expenses

10.0%

100.0%

1000.0%

Percentage Increase in System 

Expenses

After Rule Expenses Baseline Expenses Percent Increase in Expenses

Exhibit 8-8

Comparison of CWS Baseline and Post-Compliance Total Expenses

for Systems Serving < 100 People (MCL 3 μg/L)
Chapter 8, Economic Impact Analyses 8-12 Proposed Arsenic in Drinking Water Rule RIA

$0

$10,000

$20,000

$30,000

$40,000

$50,000

$60,000

$70,000

$80,000

10.0% 20.0% 30.0% 40.0% 50.0% 60.0% 70.0% 80.0% 90.0% 95.0% 97.5% 99.9%

Percentage of Systems

Maximum System Expenses

10.0%

100.0%

1000.0%

Percentage Increase in System 

Expenses

After Rule Expenses Baseline Expenses Percent Increase in Expenses

Exhibit 8-10

Comparison of CWS Baseline and Post-Compliance Total Expenses

for Systems Serving < 100 People (MCL 10 μg/L)

$0

$10,000

$20,000

$30,000

$40,000

$50,000

$60,000

$70,000

$80,000

$90,000

10.0% 20.0% 30.0% 40.0% 50.0% 60.0% 70.0% 80.0% 90.0% 95.0% 97.5% 99.9%

Percentage of Systems

Maximum System Expenses

10.0%

100.0%

1000.0%

Percentage Increase in System 

Expenses

After Rule Expenses Baseline Expenses Percent Increase in Expenses

Exhibit 8-11

Comparison of CWS Baseline and Post-Compliance Total Expenses

for Systems Serving < 100 People (MCL 20 μg/L)
Chapter 8, Economic Impact Analyses 8-13 Proposed Arsenic in Drinking Water Rule RIA

$0

$200,000

$400,000

$600,000

$800,000

$1,000,000

$1,200,000

10.0% 20.0% 30.0% 40.0% 50.0% 60.0% 70.0% 80.0% 90.0% 95.0% 97.5% 99.9%

Percentage of Systems

Maximum System Expenses

10.0%

100.0%

1000.0%

Percentage Increase in System 

Expenses

After Rule Expenses Baseline Expenses Percent Increase in Expenses

Exhibit 8-13

Comparison of CWS Baseline and Post-Compliance Total Expenses

for Systems Serving 101-500 People (MCL 5 μg/L)

$0

$200,000

$400,000

$600,000

$800,000

$1,000,000

$1,200,000

10.0% 20.0% 30.0% 40.0% 50.0% 60.0% 70.0% 80.0% 90.0% 95.0% 97.5% 99.9%

Percentage of Systems

Maximum System Expenses

10.0%

100.0%

1000.0%

Percentage Increase in System 

Expenses

After Rule Expenses Baseline Expenses Percent Increase in Expenses

Exhibit 8-12

Comparison of CWS Baseline and Post-Compliance Total Expenses

for Systems Serving 101-500 People (MCL 3 μg/L)
Chapter 8, Economic Impact Analyses 8-14 Proposed Arsenic in Drinking Water Rule RIA

$0

$200,000

$400,000

$600,000

$800,000

$1,000,000

$1,200,000

10.0% 20.0% 30.0% 40.0% 50.0% 60.0% 70.0% 80.0% 90.0% 95.0% 97.5% 99.9%

Percentage of Systems

Maximum System Expenses

10.0%

100.0%

1000.0%

Percentage Increase in System 

Expenses

After Rule Expenses Baseline Expenses Percent Increase in Expenses

Exhibit 8-14

Comparison of CWS Baseline and Post-Compliance Total Expenses

for Systems Serving 101-500 People (MCL 10 μg/L)

$0

$200,000

$400,000

$600,000

$800,000

$1,000,000

$1,200,000

10.0% 20.0% 30.0% 40.0% 50.0% 60.0% 70.0% 80.0% 90.0% 95.0% 97.5% 99.9%

Percentage of Systems

Maximum System Expenses

10.0%

100.0%

1000.0%

Percentage Increase in System 

Expenses

After Rule Expenses Baseline Expenses Percent Increase in Expenses

Exhibit 8-15

Comparison of CWS Baseline and Post-Compliance Total Expenses

for Systems Serving 101-500 People (MCL 20 μg/L)
Chapter 8, Economic Impact Analyses 8-15 Proposed Arsenic in Drinking Water Rule RIA

$0

$200,000

$400,000

$600,000

$800,000

$1,000,000

$1,200,000

$1,400,000

$1,600,000

$1,800,000

$2,000,000

10.0% 20.0% 30.0% 40.0% 50.0% 60.0% 70.0% 80.0% 90.0% 95.0% 97.5% 99.9%

Percentage of Systems

Maximum System Expenses

10.0%

100.0%

1000.0%

Percentage Increase in System 

Expenses

After Rule Expenses Baseline Expenses Percent Increase in Expenses

Exhibit 8-17

Comparison of CWS Baseline and Post-Compliance Total Expenses

for Systems Serving 501-1,000 People (MCL 5 μg/L)

$0

$200,000

$400,000

$600,000

$800,000

$1,000,000

$1,200,000

$1,400,000

$1,600,000

$1,800,000

$2,000,000

10.0% 20.0% 30.0% 40.0% 50.0% 60.0% 70.0% 80.0% 90.0% 95.0% 97.5% 99.9%

Percentage of Systems

Maximum System Expenses

10.0%

100.0%

1000.0%

Percentage Increase in System 

Expenses

After Rule Expenses Baseline Expenses Percent Increase in Expenses

Exhibit 8-16

Comparison of CWS Baseline and Post-Compliance Total Expenses

for Systems Serving 501-1,000 People (MCL 3 μg/L)
Chapter 8, Economic Impact Analyses 8-16 Proposed Arsenic in Drinking Water Rule RIA

$0

$200,000

$400,000

$600,000

$800,000

$1,000,000

$1,200,000

$1,400,000

$1,600,000

$1,800,000

$2,000,000

10.0% 20.0% 30.0% 40.0% 50.0% 60.0% 70.0% 80.0% 90.0% 95.0% 97.5% 99.9%

Percentage of Systems

Maximum System Expenses

10.0%

100.0%

1000.0%

Percentage Increase in System 

Expenses

After Rule Expenses Baseline Expenses Percent Increase in Expenses

Exhibit 8-18

Comparison of CWS Baseline and Post-Compliance Total Expenses

for Systems Serving 501-1,000 People (MCL 10 μg/L)

$0

$200,000

$400,000

$600,000

$800,000

$1,000,000

$1,200,000

$1,400,000

$1,600,000

$1,800,000

$2,000,000

10.0% 20.0% 30.0% 40.0% 50.0% 60.0% 70.0% 80.0% 90.0% 95.0% 97.5% 99.9%

Percentage of Systems

Maximum System Expenses

1.0%

10.0%

100.0%

1000.0%

Percentage Increase in System 

Expenses

After Rule Expenses Baseline Expenses Percent Increase in Expenses

Exhibit 8-19

Comparison of CWS Baseline and Post-Compliance Total Expenses

for Systems Serving 501-1,000 People (MCL 20 μg/L)
Chapter 8, Economic Impact Analyses 8-17 Proposed Arsenic in Drinking Water Rule RIA

$0

$500,000

$1,000,000

$1,500,000

$2,000,000

$2,500,000

$3,000,000

10.0% 20.0% 30.0% 40.0% 50.0% 60.0% 70.0% 80.0% 90.0% 95.0% 97.5% 99.9%

Percentage of Systems

Maximum System Expenses

1.0%

10.0%

100.0%

1000.0%

Percentage Increase in System 

Expenses

After Rule Expenses Baseline Expenses Percent Increase in Expenses

Exhibit 8-21

Comparison of CWS Baseline and Post-Compliance Total Expenses

for Systems Serving 1,001-3,300 People (MCL 5 μg/L)

$0

$500,000

$1,000,000

$1,500,000

$2,000,000

$2,500,000

$3,000,000

10.0% 20.0% 30.0% 40.0% 50.0% 60.0% 70.0% 80.0% 90.0% 95.0% 97.5% 99.9%

Percentage of Systems

Maximum System Expenses

1.0%

10.0%

100.0%

1000.0%

Percentage Increase in System 

Expenses

After Rule Expenses Baseline Expenses Percent Increase in Expenses

Exhibit 8-20

Comparison of CWS Baseline and Post-Compliance Total Expenses

for Systems Serving 1,001-3,000 People (MCL 3 μg/L)
Chapter 8, Economic Impact Analyses 8-18 Proposed Arsenic in Drinking Water Rule RIA

$0

$500,000

$1,000,000

$1,500,000

$2,000,000

$2,500,000

$3,000,000

10.0% 20.0% 30.0% 40.0% 50.0% 60.0% 70.0% 80.0% 90.0% 95.0% 97.5% 99.9%

Percentage of Systems

Maximum System Expenses

1.0%

10.0%

100.0%

1000.0%

Percentage Increase in System 

Expenses

After Rule Expenses Baseline Expenses Percent Increase in Expenses

Exhibit 8-22

Comparison of CWS Baseline and Post-Compliance Total Expenses

for Systems Serving 1,001-3,300 People (MCL 10 μg/L)

$0

$500,000

$1,000,000

$1,500,000

$2,000,000

$2,500,000

$3,000,000

10.0% 20.0% 30.0% 40.0% 50.0% 60.0% 70.0% 80.0% 90.0% 95.0% 97.5% 99.9%

Percentage of Systems

Maximum System Expenses

1.0%

10.0%

100.0%

1000.0%

Percentage Increase in System 

Expenses

After Rule Expenses Baseline Expenses Percent Increase in Expenses

Exhibit 8-23

Comparison of CWS Baseline and Post-Compliance Total Expenses

for Systems Serving 1,001-3,000 People (MCL 20 μg/L)
Chapter 8, Economic Impact Analyses 8-19 Proposed Arsenic in Drinking Water Rule RIA

$0

$1,000,000

$2,000,000

$3,000,000

$4,000,000

$5,000,000

$6,000,000

10.0% 20.0% 30.0% 40.0% 50.0% 60.0% 70.0% 80.0% 90.0% 95.0% 97.5% 99.9%

Percentage of Systems

Maximum System Expenses

1.0%

10.0%

100.0%

1000.0%

Percentage Increase in System 

Expenses

After Rule Expenses Baseline Expenses Percent Increase in Expenses

Exhibit 8-24

Comparison of CWS Baseline and Post-Compliance Total Expenses

for Systems Serving 3,301-10,000 People (MCL 3 μg/L)

$0

$1,000,000

$2,000,000

$3,000,000

$4,000,000

$5,000,000

$6,000,000

10.0% 20.0% 30.0% 40.0% 50.0% 60.0% 70.0% 80.0% 90.0% 95.0% 97.5% 99.9%

Percentage of Systems

Maximum System Expenses

1.0%

10.0%

100.0%

1000.0%

Percentage Increase in System 

Expenses

After Rule Expenses Baseline Expenses Percent Increase in Expenses

Exhibit 8-25

Comparison of CWS Baseline and Post-Compliance Total Expenses

for Systems Serving 3,301-10,000 People (MCL 5 μg/L)
Chapter 8, Economic Impact Analyses 8-20 Proposed Arsenic in Drinking Water Rule RIA

$0

$1,000,000

$2,000,000

$3,000,000

$4,000,000

$5,000,000

$6,000,000

10.0% 20.0% 30.0% 40.0% 50.0% 60.0% 70.0% 80.0% 90.0% 95.0% 97.5% 99.9%

Percentage of Systems

Maximum System Expenses

1.0%

10.0%

100.0%

1000.0%

Percentage Increase in System 

Expenses

After Rule Expenses Baseline Expenses Percent Increase in Expenses

Exhibit 8-26

Comparison of CWS Baseline and Post-Compliance Total Expenses

for Systems Serving 3,301-10,000 People (MCL 10 μg/L)

$0

$1,000,000

$2,000,000

$3,000,000

$4,000,000

$5,000,000

$6,000,000

10.0% 20.0% 30.0% 40.0% 50.0% 60.0% 70.0% 80.0% 90.0% 95.0% 97.5% 99.9%

Percentage of Systems

Maximum System Expenses

1.0%

10.0%

100.0%

1000.0%

Percentage Increase in System 

Expenses

After Rule Expenses Baseline Expenses Percent Increase in Expenses

Exhibit 8-27

Comparison of CWS Baseline and Post-Compliance Total Expenses

for Systems Serving 3,301-10,000 People (MCL 20 μg/L)
Chapter 8, Economic Impact Analyses 8-21 Proposed Arsenic in Drinking Water Rule RIA

8.2.5 Small System Affordability

Section 1415(e)(1) of SDWA allows States to grant variances to small water systems (i.e.,

systems having fewer than 10,000 customers) in lieu of complying with an MCL if EPA

determines that there are no nationally affordable compliance technologies for that system

size/water quality combination. The system must then install an EPA-listed variance treatment

technology (§1412(b)(15)) that makes progress toward the MCL, if not necessarily reaching it. 

To list variance technologies, three showings must be made: 

1) EPA must determine, on a national level, that there are no compliance technologies that

are affordable for the given small system size category/source water quality combination.

2) If there is no nationally affordable compliance technology, then EPA must identify a

variance technology the may not reach the MCL but that will allow small systems to make

progress toward the MCL (it must achieve the maximum reduction affordable). This

technology must also be listed as a small systems variance technology by EPA in order for

small systems to be able to rely on it for regulatory purposes.

3) EPA must make a finding on a national level, that use of the variance technology would be

protective of public health. 

States must then make a site-specific determination for each system as to whether or not the

system can afford to meet the MCL based on State-developed affordability criteria. If the State

determines that compliance is not affordable for the system, it may grant a variance, but it must

establish terms and conditions, as necessary, to ensure that the variance is adequately protective

of human health.

In the Agency’s draft national-level affordability criteria published in the August 6, 1998 Federal

Register, EPA discussed the affordable treatment technology determinations for the contaminants

regulated before 1996. The national-level affordability criteria were derived as follows. First an

“affordability threshold” was calculated. The affordability threshold was based on the total annual

household water bill as a percentage of household income. In developing this threshold value,

EPA considered the percentage of median household income spent by an average household on

comparable goods and services such items as housing (28%), transportation (16%), food (12%),

energy and fuels (3.3%), telephone (1.9%), water and other public services (0.7%), entertainment

(4.4%) and alcohol and tobacco (1.5%). 

Another of the key factors that EPA used to select an affordability threshold was cost

comparisons with other risk reduction activities for drinking water. Section 1412(b)(4)(E)(ii) of

the SDWA identifies both Point-of-Entry and Point-of-Use devices as options for compliance

technologies. EPA examined the projected costs of these options. EPA also investigated the

costs associated with supplying bottled water for drinking and cooking purposes. The median

income percentages that were associated with these risk reduction activities were: Point-Of-Entry

(> 2.5%), Point-of-Use (2%) and bottled water (> 2.5%). 
Chapter 8, Economic Impact Analyses 8-22 Proposed Arsenic in Drinking Water Rule RIA

3 5 10 20

<100 $368.13 $363.65 $357.17 $348.72

101-500 $258.68 $253.64 $246.38 $237.67

501-1,000 $106.07 $103.74 $98.35 $93.25

1,001-3,300 $63.61 $60.38 $56.51 $51.80

3,301-10,000 $44.28 $40.77 $37.04 $32.52

10,001-50,000 $36.39 $33.22 $29.13 $24.99

50,001-100,000 $29.52 $26.64 $22.80 $19.44

100,001-1,000,000 $23.47 $21.20 $18.32 $15.41

1,000,000 + $2.70 $1.73 $0.89 $0.55

All categories $43.73 $39.18 $33.05 $23.62

MCL (μg/L)

SIZE CATEGORIES

Exhibit 8-28

Mean Annual Costs to Households Served by CWSs, by Size Category

Based on the foregoing analysis, EPA developed an affordability criteria of 2.5% of median

household income, or about $750, for the affordability threshold (EPA, 1998). The median water

bill for households in each small system category was then subtracted from this threshold to

determine the additional expenditure per household that was considered affordable for new

treatment. This difference is referred to as the “available expenditure margin.” Based on EPA’s

1995 Community Water System Survey, median water bills were about $250 per year for small

system customers. Thus, an average available expenditure margin of up to $500 per year per

household was considered affordable for the contaminants regulated before 1996. EPA next

identified treatment technologies for all pre-1996 contaminants with average per household costs

below $500 per year. Therefore it was not necessary to list any small system variance

technologies for existing contaminant rules. 

Applying this criterion to the case of arsenic in drinking water, EPA has determined that

affordable technologies exist for all system size categories and has therefore not identified a

variance technology for any system size or source water combination at the proposed MCL. (See

Exhibit 8-28, Mean Annual Household Costs Across MCL Options by System Size.) In other

words, annual household costs after installation of the compliance technology are projected to be

below the available affordability threshold for all system size categories for the proposed MCLs. 

EPA solicits comment on its determination in this case as well as its affordability criteria more

generally.
Chapter 8, Economic Impact Analyses 8-23 Proposed Arsenic in Drinking Water Rule RIA

EPA recognizes that individual water systems may have higher than average treatment costs,

fewer than average households to absorb these costs, or lower than average incomes, but believes

that the affordability criteria should be based on characteristics of typical systems and should not

address situations where costs might be extremely high or low or excessively burdensome. EPA

believes that there are other mechanisms that may address these situations to a certain extent. In

any case, EPA believes that small system variances should be the exception and not the rule.

EPA expects the available expenditure margin to be lower than $500 per household per year for

the Arsenic Rule because some sources of data, for example the Current Population Survey,

indicate that water rates are currently increasing faster than median household income. Thus, the

"baseline" for annual water bills will rise as treatment is installed for compliance with regulations

promulgated after 1996, but before the Arsenic Rule is promulgated. 

EPA notes, however, that high water costs are often associated with systems that have already

installed treatment to comply with a NPDWR. Such in-place treatment facilities may facilitate

compliance with future standards. EPA’s approach to establishing the national-level affordability

criteria did not incorporate a baseline for in-place treatment technology. Assuming that systems

with high baseline water costs would need to install a new treatment technology to comply with a

NPDWR may thus overestimate the actual costs for some systems. 

To investigate this issue, during the derivation of the national-level affordability criteria, EPA

examined a group of five small surface water systems with annual water bills above $500 per

household per year. All of these systems had installed disinfection and filtration technologies to

comply with the Surface Water Treatment Rule. If these systems were required to install

treatment to comply with the revised arsenic standard, modification of the existing processes

would be much more cost-effective than adding a new technology. As a result, because these

systems have already made the investment in treatment technology, and the cost is incorporated

into current annual household water bills, costs to the household may not increase substantially.

Installing new technologies may interfere with treatment in-place or require additional treatment

to address side effects which will increase costs over the arsenic treatment technology base costs.

(An example is corrosion control for lead and copper, which may need to be adjusted to

accommodate other treatment). While EPA tries to account for such interference in its cost

estimates for each new compliance technology, it is not possible to anticipate all the site specific

issues which may arise. 

EPA believes that there is another mechanism in the SDWA to address cost impacts on small

systems composed primarily of low-income households. Systems that meet criteria established by

the State could be classified disadvantaged communities under Section 1452(d) of the SDWA. 

They can receive additional subsidization under the Drinking Water State Revolving Fund

(DWSRF) program, including forgiveness of principal. Under DWSRF, States must provide a

minimum of 15% of the available funds for loans to small communities and have the option of

providing up to 30% of the grant to provide additional loan subsidies to the disadvantaged

systems, as defined by the State.
Chapter 8, Economic Impact Analyses 8-24 Proposed Arsenic in Drinking Water Rule RIA

8.3 Coordination With Other Federal Rules

Several Federal drinking water rules are under development involving treatment requirements that

may relate to the treatment of arsenic for this drinking water rule. Although it is very difficult to

determine how compliance with the proposed Arsenic Rule might effect compliance with other

drinking water regulations, the following briefly describes each rule, the impact the Arsenic Rule

may have on that rule, and/or how each rule may impact the arsenic standard. The Arsenic Rule is

expected to be promulgated in a similar time frame as the Ground Water Rule, the Radon Rule,

and the Microbial and Disinfection By-Product Rule. 

Ground Water Rule (GWR)

The goals of the GWR are to: (1) provide a consistent level of public health protection; (2)

prevent waterborne microbial disease outbreaks; (3) reduce endemic waterborne disease; and (4)

prevent fecal contamination from reaching consumers. To assure public health protection, EPA

has the responsibility to develop a GWR which not only specifies the appropriate use of

disinfection, but also addresses other components of ground water systems. This general

provision is supplemented with an additional requirement that EPA develop regulations specifying

the use of disinfectants for ground water systems as necessary. To meet these requirements, EPA

is working with stakeholders to develop a GWR proposal by Fall 1999 and a final rule by Fall

2000. 

The GWR will result in more systems using disinfection. If a system does add a disinfection

technology, it may contribute to arsenic pre-oxidation. This largely depends on the type of

disinfection technology employed. For example, if a system chooses a technology such as

ultraviolet radiation, it may not affect arsenic pre-oxidation. However, if it chooses chlorination,

it will contribute to arsenic pre-oxidation. Arsenic pre-oxidation from arsenic (III) to arsenic (V)

will enhance the removal efficiencies of the technologies. Another option is that systems may use

membrane filtration for the GWR. In that case, depending on the size of the membrane, some

arsenic removal can be achieved. Thus, the GWR is expected to alleviate some of the burden of

the Arsenic Rule.

Radon

Like the Ground Water Rule, the Radon Rule will also be finalized before the Arsenic Rule. In

the 1996 Amendments to the SDWA, Congress [Section 1412(b)(13)] directed EPA to propose

an MCLG and NPDWR for radon by August 1999 and finalize the regulation by August 2000

(§1412 (b)(13)). One option for compliance with the Radon Rule is that systems may employ

aeration. Aeration alone, however, will not likely be sufficient to oxidize arsenic (III) to arsenic

(V). However, if systems do aerate, they may be required by State regulations to also disinfect. 

The disinfection process may oxidize the arsenic, depending on the type of disinfection employed. 

In particular, ultraviolet disinfection may not assist in arsenic oxidation (still under investigation

by US EPA), whereas chemical disinfection or oxidation is likely to. Thus, the Radon Rule is

expected to alleviate some of the burden of the Arsenic Rule.
Chapter 8, Economic Impact Analyses 8-25 Proposed Arsenic in Drinking Water Rule RIA

Microbial and Disinfection By-product Regulations

To control disinfection and disinfection byproducts and to strengthen control of microbial

pathogens in drinking water, EPA is developing a group of interrelated regulations, as required by

the SDWA. These regulations, referred to collectively as the Microbial Disinfection By-product

(M/DBP) Rules, are intended to address risk trade-offs between the two different types of

contaminants. 

EPA proposed a Stage 1 Disinfectants/Disinfection By-products Rule (DBPR) and Interim

Enhanced Surface Water Treatment Rule (IESWTR) in July 1994. EPA issued the final Stage 1

DBPR and IESWTR in November, 1998.

The Agency has finalized and is currently implementing a third rule, the Information Collection

Rule, that will provide data to support development of subsequent M/DBP regulations. These

subsequent rules include a Stage 2 DBPR and a companion Long-Term 2 Enhanced Surface

Water Treatment Rule (LT2ESWTR).

Stage 1 DBPR and IESWTR will primarily affect large surface water systems, so EPA does not

expect much overlap with small systems treating for arsenic. Stage 2 DBPR and possibly the

LT2ESWTR, however, would have significance as far as arsenic removal is concerned. For

systems removing DBP precursors, systems may use nanofiltration. The use of nanofiltration

would also be relevant for removing arsenic, and as a result, would ease some burden when

systems implement these later rules.

8.4 Minimization of Economic Burden

The proposed Arsenic Rule includes several provisions that will insure that the economic burden

to water systems is minimized, while still ensuring that the public health objectives of the rule are

met. First, the rule is developed around the concept of a performance target known as the

maximum contaminant level (MCL). Rather than prescribe a single treatment technique that must

be installed in all water systems, EPA is only requiring those systems that currently provide

finished water with an arsenic concentration above the target to undertake or modify treatment.

As seen above, this will exclude the vast majority of systems from having to undertake any

additional treatment under this proposed rule. In addition, if a system does have to undertake or

modify treatment, EPA is allowing systems to choose from a broad list of technologies, and is

encouraging systems to choose the treatment technique that minimizes their total costs.

Second, EPA is allowing states to grant nine year monitoring waivers to those systems that have a

history of arsenic monitoring results below the proposed MCL, and that do not show a substantial

risk of future arsenic contamination. This provision of the rule will further reduce the cost to

systems that currently provide finished water with low arsenic concentrations.

Finally, EPA is allowing small systems with finished water concentrations above the proposed

MCL to install POU or POE technologies. This option will further allow small systems to

minimize their total cost of compliance with the proposed rule.
Chapter 8, Economic Impact Analyses 8-26 Proposed Arsenic in Drinking Water Rule RIA

8.5 Unfunded Mandates Reform Act

Title II of the Unfunded Mandates Reform Act of 1995 (UMRA), P.L. 104-4, establishes

requirements for Federal agencies to assess the effects of their regulatory actions on State, local,

and Tribal governments, and the private sector. Under UMRA Section 202, EPA generally must

prepare a written statement, including a cost-benefit analysis, for proposed and final rules with

"Federal mandates" that may result in expenditures to State, local, and Tribal governments, in the

aggregate, or to the private sector, of $100 million or more in any one year.

Before promulgating an EPA rule for which a written statement is needed, Section 205 of the

UMRA generally requires EPA to identify and consider a reasonable number of regulatory

alternatives and adopt the least costly, most cost effective or least burdensome alternative that

achieves the objectives of the rule. The provisions of Section 205 do not apply when they are

inconsistent with applicable law. Moreover, Section 205 allows EPA to adopt an alternative

other than the least costly, most cost effective or least burdensome alternative if the Administrator

publishes an explanation why the more “costly” alternative was preferred for the final rule. 

Prior to establishing any regulatory requirements that may significantly or uniquely affect small

governments, including Tribal governments, EPA must develop a small government agency plan

under Section 203 of the UMRA . The plan must provide for notifying potentially affected small

governments, enabling officials of affected small governments to have meaningful and timely input

in the development of EPA regulatory proposals with significant Federal intergovernmental

mandates, and informing, educating and advising small governments on compliance with the

regulatory requirements. 

EPA has determined that this rule contains a Federal mandate that may result in expenditures of

$100 million or more for State, local, and Tribal governments, in the aggregate and the private

sector in any one year. Accordingly, under Section 202 of the UMRA, EPA is obligated to

prepare a written statement addressing: 

1. The authorizing legislation;

2. Cost-benefit analysis including an analysis of the extent to which the costs of State, local

and Tribal governments will be paid for by the Federal government;

3. Estimates of future compliance costs and disproportionate budgetary effects;

4. Macro-economic effects;

5. A summary of EPA’s consultation with State, local, and Tribal governments and their

concerns, including a summary of the Agency’s evaluation of those comments and

concerns; and

6. Identification and consideration of regulatory alternatives and the selection of the least

costly, most cost-effective or least burdensome alternative that achieves the objectives of

the rule.
Chapter 8, Economic Impact Analyses 8-27 Proposed Arsenic in Drinking Water Rule RIA

The legislative authority for the arsenic rule is discussed in Chapter 2. Items two through five are

addressed below, with the exception of future compliance costs, which are discussed in Chapter 6. 

Regulatory alternatives, the last item, are addressed in Chapters 3, 6 and 7. 

8.5.1 Social Costs and Benefits

Chapters Five, Six and Seven contain a detailed cost-benefit analysis in support of the Arsenic

Rule. At a 7 percent discount rate, the proposed rule is expected to have a total annualized cost

of $645 million for a MCL of 3 μg/L, $445 million for a MCL 5 μg/L, $195 million for a MCL of

10 μg/L, and $63.9 million for a MCL of 20 μg/L.

EPA estimates the proposed arsenic rule will have total health benefits as a result of avoided

bladder cancer cases of approximately $43.6 to $104.2 million if the MCL were set at 3 μg/L,

$31.7 to $89.9 million if the MCL were to be set at 5 μg/L, $17.9 to $52.1 million if the MCL

were set at 10 μg/L, and $7.9 to $29.8 million if the MCL were set at 20 μg/L. These monetized

health benefits of reducing arsenic exposures in drinking water are attributable to the reduced

incidence of fatal and non-fatal bladder cancer. Currently under baseline assumptions (no control

of arsenic exposure), there are annual fatal cancers and non-fatal cancers associated with arsenic

exposures through CWSs. At an arsenic MCL level of 3 μg/L, an estimated 6 to 14 fatal cancers

and 16 to 39 non-fatal cancers per year are prevented; at a arsenic level of 5 μg/L, an estimated 4

to 12 fatal cancers and 12 to 33 non-fatal cancers per year are prevented; at 10 μg/L, 2 to 7 fatal

and 7 to 19 non-fatal cancers per year are prevented; and at 20 μg/L, 1 to 4 fatal and 3 to 11 nonfatal cancers per year are prevented.

EPA estimates that should avoided lung cancer cases be monetized as well, the potential benefits

from reducing lung cancer cases would range from $47.2 to $448.0 million at an MCL of 3 μg/L, 

$35.0 to $384.0 million at an MCL of 5 μg/L, $19.6 to $224.0 million at an MCL of 10 μg/L,

and $8.8 to $128.0 million at an MCL of 20 μg/L. EPA estimates that the potential number of

lung cancer cases avoided ranges from 8 to 80 at an MCL of 3 μg/L, from 6 to 68 at an MCL of 5

μg/L, from 3 to 40 at an MCL of 10 μg/L, and from 2 to 23 at an MCL of 20 μg/L. A more

detailed discussion of the lung cancer risk and benefits calculation may be found in Chapter 5,

“Benefits Analysis.”

In addition to quantifiable benefits, in Chapter 5, EPA has identified many potential nonquantifiable benefits associated with reducing arsenic exposures in drinking water. These

potential benefits are not able to be quantified at this time, but may include reduced risk skin

cancer, and numerous non-cancerous health effects. In addition, certain non-health related benefits

may exists, such as ecological improvements and an increase in consumers’ perception of drinking

water. 

8.5.2 State Administrative Costs
Chapter 8, Economic Impact Analyses 8-28 Proposed Arsenic in Drinking Water Rule RIA

States will incur a range of administrative costs in complying with the arsenic rule. Administrative

costs can include program management, inspections, and enforcement activities. EPA estimates

the total annual costs of State administrative activities for compliance with the MCL at a 7

percent discount rate are approximately $5.5 million for an MCL of 3 μg/L, $5.0 million for an

MCL of 5 μg/L, $4.6 million at an MCL of 10μg/L, and $4.4 million for an MCL of 20μg/L.

Various Federal programs exist to provide financial assistance to State, local, and Tribal

governments in complying with this rule. The Federal government provides funding to States that

have a primary enforcement responsibility for their drinking water programs through the Public

Water Systems Supervision (PWSS) Grants program. Additional funding is available from other

programs administered either by EPA or other Federal agencies. These include the Drinking

Water State Revolving Fund (DWSRF) and Housing and Urban Development’s Community

Development Block Grant Program. For example, the SDWA authorizes the Administrator of the

EPA to award capitalization grants to States, which in turn can provide low cost loans and other

types of assistance to eligible public water systems. The DWSRF also assists public water

systems with financing the costs of infrastructure needed to achieve or maintain compliance with

SDWA requirements. Each State will have considerable flexibility to determine the design of its

program and to direct funding toward its most pressing compliance and public health protection

needs. States may also, on a matching basis, use up to ten percent of their DWSRF allotments for

each fiscal year to assist in running the State drinking water program.

Under PWSS Program Assistance Grants, the Administrator may make grants to States to carry

out public water system supervision programs. One State use of these funds is to develop

primacy programs. States may “contract” with other State agencies to assist in the development

or implementation of their primacy program. However, States may not use program assistance

grant funds to contract with regulated entities (i.e., water systems). PWSS Grants may be used

by States to set-up and administer a State program which includes such activities as: public

education, testing, training, technical assistance, developing and administering a remediation grant

and loan or incentive program (excludes the actual grant or loan funds), or other regulatory or

non-regulatory measures.

8.5.3 Future Compliance Costs and Disproportionate Budgetary Effects

To meet the requirement in Section 202 of the UMRA, EPA analyzed future compliance costs

and possible disproportionate budgetary effects of the MCL options. The Agency believes that

the cost estimates, shown in Exhibit 8-7 and discussed in more detail in Chapter Six, accurately

characterize future compliance costs of the proposed rule.

With regard to the disproportionate impacts, EPA considered available data sources in analyzing

the disproportionate impacts upon geographic or social segments of the nation or industry. No

rationale for disproportionate impacts based on geographic area were identified. To the extent

that there may be disproportionate impacts to low-income or other segments of the population,

EPA will prepare a small entity compliance guide, a monitoring/analytical manual, and a small

systems technology manual that will assist the public and private sector. To fully consider the

potential disproportionate impacts of this proposed rule, this analysis also developed three other

measures: 
Chapter 8, Economic Impact Analyses 8-29 Proposed Arsenic in Drinking Water Rule RIA

(1) reviewing the impacts on small versus large systems; 

(2) reviewing the costs to public versus private water systems; and 

(3) reviewing the household costs for the proposed rule.

The first measure, the national impacts on small versus large systems, is shown in Exhibit 8-29. 

Small systems are defined as those systems serving 10,000 people or less and large systems are

those systems that serve more than 10,000 people. 

The second measure of disproportionate impacts evaluated is the relative total costs to public

versus private water systems, by size. Exhibit 8-29 also presents the annual system level costs for

public and private systems by system size category for 3 μg/L, 5 μg/L, 10 μg/L, and 20 μg/L. 

The costs are comparable for public and private systems across system sizes for all options. For

example, for systems serving less than 100 people at the 5 μg/L MCL public system treatment

costs are $9 thousand and private system treatment costs are $7 thousand. This pattern may be

due in large part to the limited number of treatment options, resulting in similar treatment choices

by both public or private systems.
Chapter 8, Economic Impact Analyses 8-30 Proposed Arsenic in Drinking Water Rule RIA

System Size Total Cost

Public Private All Systems

<100 $ 9,475 $ 7,354 $ 7,559

101-500 $ 25,228 $ 18,570 $ 20,588

501-1,000 $ 34,688 $ 31,646 $ 33,474

1,001-3,300 $ 60,929 $ 51,097 $ 58,189

3,301-10,000 $ 135,573 $ 111,396 $ 131,197

10,001-1,000,000 $ 578,591 $ 547,969 $ 573,423

1,000,000 + $ 3,885,713 -- $ 3,885,713

<100 $ 9,720 $ 7,212 $ 7,450

101-500 $ 24,560 $ 18,223 $ 20,198

501-1,000 $ 34,124 $ 30,697 $ 32,778

1,001-3,300 $ 57,277 $ 48,198 $ 54,666

3,301-10,000 $ 124,552 $ 102,005 $ 120,399

10,001-1,000,000 $ 518,647 $ 459,930 $ 508,640

1,000,000 + $ 2,669,474 -- $ 2,669,474

<100 $ 9,453 $ 7,135 $ 7,350

101-500 $ 23,584 $ 17,675 $ 19,551

501-1,000 $ 32,271 $ 29,160 $ 31,048

1,001-3,300 $ 53,357 $ 44,785 $ 50,921

3,301-10,000 $ 113,338 $ 91,244 $ 109,278

10,001-1,000,000 $ 458,340 $ 415,520 $ 450,835

1,000,000 + $ 1,395,498 -- $ 1,395,498

<100 $ 9,121 $ 6,950 $ 7,157

101-500 $ 22,778 $ 16,954 $ 18,738

501-1,000 $ 30,493 $ 27,668 $ 29,376

1,001-3,300 $ 48,399 $ 41,625 $ 46,501

3,301-10,000 $ 99,872 $ 79,128 $ 95,983

10,001-1,000,000 $ 394,742 $ 334,737 $ 384,868

1,000,000 + $ 921,121 -- $ 921,121

Treatment and Monitoring Costs

*Costs were calculated at a commercial interest rate and include system 

treatment, monitoring, and administrative costs; note that systems serving over 

1 million people are public surface water systems.

MCL = 3 μ g/L

MCL = 5 μ g/L

MCL = 10 μ g/L

MCL = 20 μ g/L

Exhibit 8-29

Average Annual Cost per CWS by Ownership
Chapter 8, Economic Impact Analyses 8-31 Proposed Arsenic in Drinking Water Rule RIA

The third measure, household costs, can also be used to gauge the impact of a regulation and to

determine whether there are disproportionately higher impacts in particular segments of the

population. A detailed analysis of household cost impacts by system size is presented in Chapter

6. The costs for households served by public and private water systems are presented in Exhibit

8-30. As expected, cost per household increases as system size decreases. Cost per household is

higher for households served by smaller systems than larger systems for two reasons. First,

smaller systems produce less water than large systems and are therefore unable to utilize

economies of scale. Consequently, each household must bear a greater percentage share of the

system’s costs.

Table 8-30 presents the costs per household for systems exceeding the MCL. For each size

category there is a moderate difference in annual cost per household for 3 μg/L, 5 μg/L, 10 μg/L

and 20 μg/L across source and ownership. In general, costs per household are higher for private

systems than for public systems. This difference could be attributable to a discrepancy in the cost

of capital for public versus private entities. For public systems, the cost per household ranges

from approximately $25 to $342 per year at 5 μg/L and from approximately $22 to $329 per year

at 10 μg/L (excluding systems serving greater than 1 million people). For private systems, the

ranges are $22 to $369 per year, and $19 to $363 per year, respectively. The range of costs for 3

μg/L and 20 μg/L is similar.

To further evaluate the impacts of these household costs, the average costs per household were

compared to median household income data for each system-size category. The result of this

calculation, presented in Exhibit 8-31 for public and private systems, indicate a household’s likely

share of incremental costs in terms of its household income. For all system sizes and MCLs

average household costs as a percentage of median household income are less than one percent.
Chapter 8, Economic Impact Analyses 8-32 Proposed Arsenic in Drinking Water Rule RIA

Public Private Public Private

<100 $ 338.44 $ 374.86 $ 328.94 $ 335.61

101-500 $ 218.59 $ 285.61 $ 135.98 $ 183.96

501-1,000 $ 108.63 $ 112.60 $ 45.44 $ 46.72

1,001-3,300 $ 62.17 $ 83.24 $ 21.13 $ 27.91

3,301-10,000 $ 44.67 $ 62.96 $ 18.34 $ 22.94

10,001-1,000,000 $ 31.29 $ 31.29 $ 26.49 $ 22.81

1,000,000 + -- -- $ 2.70 --

<100 $ 341.78 $ 369.21 $ 323.48 $ 330.05

101-500 $ 213.11 $ 280.76 $ 135.22 $ 182.65

501-1,000 $ 106.00 $ 108.40 $ 44.86 $ 46.35

1,001-3,300 $ 58.31 $ 77.54 $ 20.07 $ 26.57

3,301-10,000 $ 40.60 $ 57.25 $ 16.89 $ 21.54

10,001-1,000,000 $ 28.12 $ 28.63 $ 24.73 $ 21.91

1,000,000 + -- -- $ 1.73 --

<100 $ 329.17 $ 363.09 $ 317.80 $ 325.64

101-500 $ 203.40 $ 273.04 $ 132.74 $ 180.88

501-1,000 $ 99.45 $ 102.19 $ 42.98 $ 44.48

1,001-3,300 $ 53.70 $ 71.97 $ 18.62 $ 25.49

3,301-10,000 $ 36.30 $ 50.41 $ 14.68 $ 18.55

10,001-1,000,000 $ 24.09 $ 24.47 $ 22.03 $ 19.06

1,000,000 + -- -- $ 0.89 --

<100 $ 320.13 $ 352.42 $ 310.11 $ 324.84

101-500 $ 195.99 $ 262.01 $ 132.68 $ 179.93

501-1,000 $ 93.27 $ 96.63 $ 42.26 $ 44.04

1,001-3,300 $ 48.03 $ 66.12 $ 18.20 $ 24.87

3,301-10,000 $ 31.38 $ 44.14 $ 13.35 $ 17.53

10,001-1,000,000 $ 20.27 $ 20.39 $ 19.96 $ -

1,000,000 + -- -- $ 0.55 --

MCL = 20 μg/L

*Costs to households were calculated at a commercial interest rate and include system 

treatment, monitoring, and administrative costs; note that systems serving over 1 million 

people are public surface water systems.

MCL = 10 μg/L

MCL = 5 μg/L

Groundwater Surface Water

System Size

MCL = 3 μg/L

Exhibit 8-30

Annual Compliance Costs per Household for 

CWSs Exceeding MCLs
Chapter 8, Economic Impact Analyses 8-33 Proposed Arsenic in Drinking Water Rule RIA

Public Private Public Private

<100 0.85% 0.95% 0.83% 0.85%

101-500 0.55% 0.72% 0.34% 0.46%

501-1,000 0.27% 0.28% 0.11% 0.12%

1,001-3,300 0.16% 0.21% 0.05% 0.07%

3,301-10,000 0.11% 0.16% 0.05% 0.06%

10,001-1,000,000 0.08% 0.08% 0.07% 0.06%

1,000,000 + -- -- 0.01% --

<100 0.86% 0.93% 0.82% 0.83%

101-500 0.54% 0.71% 0.34% 0.46%

501-1,000 0.27% 0.27% 0.11% 0.12%

1,001-3,300 0.15% 0.20% 0.05% 0.07%

3,301-10,000 0.10% 0.14% 0.04% 0.05%

10,001-1,000,000 0.07% 0.07% 0.06% 0.06%

1,000,000 + -- -- 0.00% --

<100 0.83% 0.92% 0.80% 0.82%

101-500 0.51% 0.69% 0.33% 0.46%

501-1,000 0.25% 0.26% 0.11% 0.11%

1,001-3,300 0.14% 0.18% 0.05% 0.06%

3,301-10,000 0.09% 0.13% 0.04% 0.05%

10,001-1,000,000 0.06% 0.06% 0.06% 0.05%

1,000,000 + -- -- 0.00% --

<100 0.81% 0.89% 0.78% 0.82%

101-500 0.49% 0.66% 0.33% 0.45%

501-1,000 0.24% 0.24% 0.11% 0.11%

1,001-3,300 0.12% 0.17% 0.05% 0.06%

3,301-10,000 0.08% 0.11% 0.03% 0.04%

10,001-1,000,000 0.05% 0.05% 0.05% 0.00%

1,000,000 + -- -- 0.00% --

*Costs to household were calculated at a commercial interest rate and include system 

treatment, monitoring, and administrative costs; median household income in May 1999 

was $39,648 updated from the 1998 annual median household income from the Census 

MCL = 10 μg/L

MCL = 5 μg/L

Groundwater Surface Water

System Size

MCL = 3 μg/L

MCL = 20 μg/L

Exhibit 8-31

Annual Compliance Costs per Household for CWSs Exceeding MCLs,

as a Percent of Median Household Income
Chapter 8, Economic Impact Analyses 8-34 Proposed Arsenic in Drinking Water Rule RIA

8.5.4 Macroeconomic Effects

As required under UMRA Section 202, EPA is required to estimate the potential macro-economic

effects of the regulation. These include effects on productivity, economic growth, full

employment, creation of productive jobs, and international competitiveness. Macro-economic

effects tend to be measurable in nationwide econometric models only if the economic impact of

the regulation reaches 0.25 percent to 0.5 percent of Gross Domestic Product (GDP). In 1998,

real GDP was $7,552 billion so a rule would have to cost at least $18 billion annually to have a

measurable effect. A regulation with a smaller aggregate effect is unlikely to have any measurable

impact unless it is highly focused on a particular geographic region or economic sector. The

macro-economic effects on the national economy from the arsenic rule should be negligible based

on the fact that, assuming 100 percent compliance with an MCL, the total annual costs are

approximately $750 million at the 3 μg/L level, $440 million at the 5 μg/L level, $190 million at

the 10 μg/L level, and $73 million at the 20 μg/L level (at a 7 percent discount rate). In addition,

the costs are not expected to be highly focused on a particular geographic region or industry

sector.

8.5.5 Consultation with State, Local, and Tribal Government

Under UMRA section 204, EPA is to provide a summary of its consultation with elected

representatives (or their designated authorized employees) of affected State, local, and Tribal

governments in this rulemaking. EPA initiated consultations with governmental entities and the

private sector affected by this rulemaking through various means. This included five stakeholder

meetings announced in the Federal Register and open to any one interested in attending in person

or by phone, and presentations at meetings of the American Water Works Association (AWWA),

the Association of State Drinking Water Administrators (ASDWA), the Association of California

Water Agencies (ACWA), and the Association of Metropolitan Water Agencies (AMWA). 

Participants in EPA’s stakeholder meetings also included representatives from the National Rural

Water Association, AMWA, ASDWA, AWWA, ACWA, Rural Community Assistance Program,

State departments of environmental protection, State health departments, State drinking water

programs, and a Tribe. EPA also made presentations at Tribal meetings in Nevada, Alaska, and

California. 

To address the proposed rule’s impact on small entities, the Agency consulted with

representatives of small water systems and convened a Small Business Advocacy Review Panel in

accordance with the Regulatory Flexibility Act (RFA) as amended by the Small Business

Regulatory Enforcement Fairness Act (SBREFA). Two of the small entity representatives were

elected officials from local governments. EPA also invited State drinking water program

representatives to participate in a number of workgroup meetings. In addition to these

consultations, EPA participated in and gave presentations at AWWA’s Technical Workgroup for

Arsenic. State public health department and drinking water program representatives, drinking

water districts, and ASDWA participated in the Technical Workgroup meetings. A summary of

State, local, and Tribal government concerns on this proposed rulemaking is shown in the next

section.
Chapter 8, Economic Impact Analyses 8-35 Proposed Arsenic in Drinking Water Rule RIA

In order to inform and involve Tribal governments in the rulemaking process, EPA staff attended

the 16th Annual Consumer Conference of the National Indian Health Board on October 6-8, 1998

in Anchorage, Alaska. Over nine hundred attendees representing Tribes from across the country

were in attendance. During the conference, EPA conducted two workshops for meeting

participants. The objectives of the workshops were to present an overview of EPA’s drinking

water program, solicit comments on key issues of potential interest in upcoming drinking water

regulations, and to solicit advice in identifying an effective consultative process with Tribes for the

future. 

EPA, in conjunction with the Inter Tribal Council of Arizona (ITCA), also convened a Tribal

consultation meeting on February 24-25, 1999, in Las Vegas, Nevada to discuss ways to involve

Tribal representatives, both Tribal council members and tribal water utility operators, in the

stakeholder process. Approximately twenty-five representatives from a diverse group of Tribes

attended the two-day meeting. Meeting participants included representatives from the following

Tribes: Cherokee Nation, Nezperce Tribe, Jicarilla Apache Tribe, Blackfeet Tribe, Seminole

Tribe of Florida, Hopi Tribe, Cheyenne River Sioux Tribe, Menominee Indian Tribe, Tulalip

Tribes, Mississippi Band of Choctaw Indians, Narragansett Indian Tribe, and Yakama Nation. 

The major meeting objectives were to: 

(1) identify key issues of concern to Tribal representatives; 

(2) solicit input on issues concerning current OGWDW regulatory efforts; 

(3) solicit input and information that should be included in support of future drinking

water regulations; and 

(4) provide an effective format for Tribal involvement in EPA’s regulatory

development process. 

EPA staff also provided an overview on the forthcoming arsenic rule at the meeting. The

presentation included the health concerns associated with arsenic, EPA’s current position on

arsenic in drinking water, the definition of an MCL, an explanation of the difference between

point-of-use and point-of-entry treatment devices, and specific issues for Tribes. The following

questions were posed to the Tribal representatives to begin discussion on arsenic in drinking

water: 

(1) What are the current arsenic levels in your water systems? 

(2) What are Tribal water systems affordability issues in regard to arsenic? 

(3) Does your Tribe use well water, river water or lake water? 

(4) Does your Tribe purchase water from another drinking water utility? 

The summary for the February 24-25, 1999 meeting was sent to all 565 Federally recognized

Tribes in the United States. 

EPA also conducted a series of workshops at the Annual Conference of the National Tribal

Environmental Council which was held on May 18-20, 1999 in Eureka, California. 

Representatives from over 50 Tribes attended all, or part, of these sessions. The objectives of the

workshops were to provide an overview of forthcoming EPA regulations affecting water systems;

discuss changes to operator certification requirements; discuss funding for Tribal water systems;
Chapter 8, Economic Impact Analyses 8-36 Proposed Arsenic in Drinking Water Rule RIA

and to discuss innovative approaches to regulatory cost reduction. Meeting summaries for EPA’s

Tribal consultations are available in the public docket for this proposed rulemaking. 

8.5.6 State, Local, and Tribal Government Concerns 

State and local governments raised several concerns, including the high costs of the rule to small

systems; the burden of revising the State primacy program; the high degree of uncertainty

associated with the benefits; and the high costs of including Non-Transient Non-Community

Water Systems (NTNCWSs). EPA modified the revision of State primacy in order to decrease

the burden of the new arsenic regulation in response to State concerns, to minimize paperwork

and documentation of existing programs that would manage the arsenic regulation.

Tribal representatives were generally supportive of regulations which would ensure a high level of

water quality, but raised concerns over funding for regulations. With regard to the forthcoming

proposed arsenic rule, many Tribal representatives saw the health benefits as highly desirable, but

felt that unless additional funds were made available, implementing the regulation would be

difficult for many Tribes. 

EPA understands the State, local, and Tribal government concerns with the above issues. The

Agency believes the options for small systems, proposed for public comment in this rulemaking,

will address stakeholder concerns pertaining to small systems and will help to reduce the financial

burden to these systems.

8.5.7 Regulatory Alternatives Considered

As required under Section 205 of the UMRA, EPA considered several regulatory alternatives in

developing an MCL for arsenic in drinking water. In preparation for this consideration, this

Regulatory Impact Analysis evaluated arsenic levels of 3 μg/L, 5 μg/L, 10 μg/L, and 20 μg/L. 

Also evaluated were two scenarios for NTNCWSs: NTNCWSs treat and monitor, NTNCWSs

only monitor and do not treat.

This analysis also evaluated national costs and benefits of States choosing to reduce arsenic

exposure in drinking water. EPA believes that the regulatory approaches proposed for arsenic in

today’s notice are the most cost-effective options that achieve the objectives of the rule and

provide the highest degree of public health protection. 

8.5.8 Impacts on Small Governments

In developing this rule, EPA consulted with small governments pursuant to section 203 of the

UMRA to address impacts of regulatory requirements in the rule that might significantly or

uniquely affect small governments. In preparation for the proposed Arsenic Rule, EPA conducted

analysis on small government impacts and included small government officials or their designated

representatives in the rule making process. EPA conducted stakeholder meetings on the

development of the arsenic rule which gave a variety of stakeholders, including small

governments, the opportunity for timely and meaningful participation in the regulatory

development process. Groups such as the National Association of Towns and Townships, the
Chapter 8, Economic Impact Analyses 8-37 Proposed Arsenic in Drinking Water Rule RIA

National League of Cities, and the National Association of Counties participated in the proposed

rulemaking process. Through such participation and exchange, EPA notified potentially affected

small governments of requirements under consideration and provided officials of affected small

governments with an opportunity to have meaningful and timely input into the development of the

regulatory proposal. 

In addition, EPA will educate, inform, and advise small systems, including those run by small

governments, about the arsenic rule requirements. One of the most important components of this

process is the Small Entity Compliance Guide, required by the Small Business Regulatory

Enforcement Fairness Act of 1996 after the rule is promulgated. This plain-English guide will

explain what actions a small entity must take to comply with the rule. Also, the Agency is

developing fact sheets that concisely describe various aspects and requirements of the Arsenic

Rule.

8.6 Effect of Compliance With the Arsenic Rule on the Technical, Financial,

and Managerial Capacity of Public Water Systems

Section 1420(d)(3) of the SDWA as amended requires that, in promulgating a NPDWR, the

Administrator shall include an analysis of the likely effect of compliance with the regulation on the

technical, financial, and managerial capacity of public water systems. The following analysis has

been performed to fulfill this statutory obligation.

Overall water system capacity is defined in EPA guidance (EPA 816-R-98-006) (EPA 1998) as

the ability to plan for, achieve, and maintain compliance with applicable drinking water standards.

Capacity has three components: technical, managerial, and financial.

Technical capacity is the physical and operational ability of a water system to meet SDWA

requirements. Technical capacity refers to the physical infrastructure of the water system,

including the adequacy of source water and the adequacy of treatment, storage, and distribution

infrastructure. It also refers to the ability of system personnel to adequately operate and maintain

the system and to otherwise implement requisite technical knowledge. A water system's technical

capacity can be determined by examining key issues and questions, including: 

• Source water adequacy. Does the system have a reliable source of drinking water? Is the

source of generally good quality and adequately protected?

• Infrastructure adequacy. Can the system provide water that meets SDWA standards?

What is the condition of its infrastructure, including well(s) or source water intakes,

treatment, storage, and distribution? What is the infrastructure's life expectancy? Does the

system have a capital improvement plan?

• Technical knowledge and implementation. Is the system's operator certified? Does the

operator have sufficient technical knowledge of applicable standards? Can the operator

effectively implement this technical knowledge? Does the operator understand the system's

technical and operational characteristics? Does the system have an effective operation and

maintenance program?
Chapter 8, Economic Impact Analyses 8-38 Proposed Arsenic in Drinking Water Rule RIA

Managerial capacity is the ability of a water system to conduct its affairs in a manner enabling the

system to achieve and maintain compliance with SDWA requirements. Managerial capacity refers

to the system's institutional and administrative capabilities. Managerial capacity can be assessed

through key issues and questions, including:

• Ownership accountability. Are the system owner(s) clearly identified? Can they be held

accountable for the system?

• Staffing and organization. Are the system operator(s) and manager(s) clearly identified? Is

the system properly organized and staffed? Do personnel understand the management

aspects of regulatory requirements and system operations? Do they have adequate

expertise to manage water system operations? Do personnel have the necessary licenses

and certifications?

• Effective external linkages. Does the system interact well with customers, regulators, and

other entities? Is the system aware of available external resources, such as technical and

financial assistance?

Financial capacity is a water system's ability to acquire and manage sufficient financial resources

to allow the system to achieve and maintain compliance with SDWA requirements. Financial

capacity can be assessed through key issues and questions, including:

• Revenue sufficiency. Do revenues cover costs? Are water rates and charges adequate to

cover the cost of water?

• Credit worthiness. Is the system financially healthy? Does it have access to capital through

public or private sources?

• Fiscal management and controls. Are adequate books and records maintained? Are

appropriate budgeting, accounting, and financial planning methods used? Does the system

manage its revenues effectively?

Generally, water systems are not expected to require significantly increased technical, financial, or

managerial capacity to comply with these new requirements.

8.7 Paperwork Reduction Act

The information collected as a result of this rule will allow the States and EPA to evaluate PWS

compliance with the rule. For the first three years after promulgation of this rule, the major

information requirements pertain to monitoring, and compliance reporting. Responses to the

request for information are mandatory (Part 141). The information collected is not confidential.

EPA is required to estimate the burden on PWS for complying with the final rule. Burden means

the total time, effort, or financial resources expended by persons to generate, maintain, retain, or

disclose or provide information to or for a Federal agency. This includes the time needed to
Chapter 8, Economic Impact Analyses 8-39 Proposed Arsenic in Drinking Water Rule RIA

review instructions; develop, acquire, install, and utilize technology and systems for the purposes

of collecting, validating, and verifying information, processing and maintaining information, and

disclosing and providing information; adjust the existing ways to comply with any previously

applicable instructions and requirements; train personnel to be able to respond to a collection of

information; search data sources; complete and review the collection of information; and transmit

or otherwise disclose the information. The Information Collection Rule for the Proposed Arsenic

Rule estimated a total burden of 3.33 million hours for 3 μg/L, 3.23 million hours for 5 μg/L, 3.15

million hours for 10 μg/L, and 3.11 for 20 μg/L.

8.8 Protecting Children From Environmental Health Risks and Safety Risks

Executive Order (EO) 13045 (62 FR 19885, April 23, 1997) applies to any rule initiated after

April 21, 1997, or proposed after April 21, 1998, that (1) is determined to be “economically

significant” as defined under E.O. 12866 and (2) concerns an environmental health or safety risk

that EPA has reason to believe may have a disproportionate effect on children. If the regulatory

action meets both criteria, EPA must evaluate the environmental health or safety effects of the

planned rule on children, and explain why the planned regulation is preferable to other potentially

effective and reasonably feasible alternatives considered by EPA.

As described in Chapter 5 (“Benefits Analysis”), there is insufficient toxicological data to

distinguish morbidity and mortality differences by age groups. No studies were located by

ATSDR (1998) that focused exclusively on evaluating unusual susceptibility to arsenic. However,

some members of the population are likely to be especially susceptible. For example, Chapter 5

describes several non-carcinogenic effects that may be of greater concern to children than adults,

such as cardiovascular or reproductive effects. Similarly, arsenic has been suggested to pose

significant problems in fetal development. This increased susceptibility may be due to a variety of

factors. These factors include increased dose (intake per unit of body weight) in children, genetic

predispositions, and dietary insufficiency (ATSDR, 1998), as well as pre-existing health

conditions.

Because children have increased fluid and food intake in relation to their body weight (NAS,

1995), their dose (milligrams per kilogram of body weight per day - mg/kg/day) of arsenic will be,

on average, greater than that of adults. For example, an intake of 1.2 liters per day in a 70 kg

adult yields an overall water intake of 0.017 liters per kg of body weight. An infant who

consumes 1 liter per day and weighs 10 kg is consuming 0.1 liter per kg of body weight, which is

more than 5 times the water intake per kg of an adult. Any contaminant which is present in the

water will be delivered at a correspondingly higher level, on a daily basis. Foy et al. noted that in

studies of chronic exposure, children appear to be more severely affected, probably due to a

higher exposure per body weight (1992 citation, reported in ATSDR, 1998). ATSDR (1998)

identified a need for additional data on the exposure of children in their arsenic analysis.

8.9 Environmental Justice

Executive Order 12898 establishes a Federal policy for incorporating environmental justice into

Federal agency missions by directing agencies to identify and address disproportionately high and

adverse human health or environmental effects of its programs, policies, and activities on minority
Chapter 8, Economic Impact Analyses 8-40 Proposed Arsenic in Drinking Water Rule RIA

and low-income populations. The Executive Order requires the Agency to consider environmental

justice issues in the rulemaking and to consult with Environmental Justice (EJ) stakeholders. 

The Agency has considered environmental justice related issues concerning the potential impacts

of this regulation and has determined that there are no substantial disproportionate effects. 

Because the arsenic rule applies to all community water systems, the majority of the population,

including minority and low-income populations will benefit from the additional health protection.

8.10 Health Risk Reduction and Cost Analysis

Section 1412(b)(3)(C) of the 1996 Amendments requires EPA to prepare a Health Risk

Reduction and Cost Analysis (HRRCA) in support of any NPDWR that includes an MCL. 

According to these requirements, EPA must analyze each of the following when proposing a

NPDWR that includes an MCL: 

1. quantifiable and non-quantifiable health risk reduction benefits for which there is a factual

basis in the rulemaking record to conclude that such benefits are likely to occur as the

result of treatment to comply with each level; 

2. quantifiable and non-quantifiable health risk reduction benefits for which there is a factual

basis in the rulemaking record to conclude that such benefits are likely to occur from

reductions in co-occurring contaminants that may be attributed solely to compliance with

the MCL, excluding benefits resulting from compliance with other proposed or

promulgated regulations;

3. quantifiable and non-quantifiable costs for which there is a factual basis in the rulemaking

record to conclude that such costs are likely to occur solely as a result of compliance with

the MCL, including monitoring, treatment, and other costs, and excluding costs resulting

from compliance with other proposed or promulgated regulations;

4. the incremental costs and benefits associated with each alternative MCL considered;

5. the effects of the contaminant on the general population and on groups within the general

population, such as infants, children, pregnant women, the elderly, individuals with a

history of serious illness, or other sub-populations that are identified as likely to be at

greater risk of adverse health effects due to exposure to contaminants in drinking water

than the general population;

6. any increased health risk that may occur as the result of compliance, including risks

associated with co-occurring contaminants; and 

7. other relevant factors, including the quality and extent of the information, the uncertainties

in the analysis, and factors with respect to the degree and nature of the risk. 

This analysis summarizes EPA’s estimates of the costs and benefits associated with various

arsenic levels. The summary tables below characterize aggregate costs and benefits, impacts on
Chapter 8, Economic Impact Analyses 8-41 Proposed Arsenic in Drinking Water Rule RIA

affected entities, and tradeoffs between risk reduction and compliance costs. This analysis also

summarizes the effects of arsenic on the general population as well as any sensitive subpopulations and provides a discussion on the uncertainties in the analysis.

8.10.1 Quantifiable and Non-Quantifiable Health Risk Reduction Benefits

Arsenic ingestion has been linked to a multitude of health effects, both cancerous and noncancerous. These health effects include cancer of the bladder, lungs, skin, kidney, nasal passages,

liver, and prostate. Arsenic ingestion has also been attributed to cardiovascular, pulmonary,

immunological, neurological, endocrine, and reproductive and developmental effects. A complete

list of the arsenic related health effects reported in humans is shown in Chapter 5. Of all the

health effects noted above, current research on arsenic exposure has only been able to define

scientifically defensible risks for bladder cancer. That is, EPA has adequate data to perform a risk

assessment on bladder cancer. Because there is currently a lack of strong evidence on the risks of

other arsenic-related health effects, the Agency has based its assessment of the quantifiable health

risk reduction benefits on the risks of arsenic induced bladder cancers. Avoided cases of lung

cancer presented in Exhibit 8-34 were estimated based on a comparison of lung cancer incidence

to bladder cancer indicidence. 

The quantifiable health benefits of reducing arsenic exposures in drinking water are attributable to

the reduced number of fatal and non-fatal bladder cancers. Exhibit 8-32 shows a range of mean

bladder cancer risks for exposed populations at or above arsenic levels of 3, 5, 10, and 20 μg/L in

CWSs. Exhibit 8-33 shows the corresponding health risk reductions (number of total bladder

cancers avoided and the proportions of fatal and non-fatal bladder cancers avoided) at 3, 5, 10,

and 20 μg/L. These ranges of total, fatal, and non-fatal bladder cancer cases are based on the

range of risks shown in Exhibit 8-32.

Exhibit 8-32

Mean Bladder Cancer Risks, Exposed Population,

and Annual Cancer Cases Avoided in CWSs1

Arsenic Level

(μg/L)

Mean Exposed

Population Risk

Population

Exposed

Total Bladder Cancer

Cases Avoided per Year

3 2.1 - 4.5 x 10-5 34,599,915 22 - 52

5 3.6 - 7.5 x 10-5 21,347,435 16 - 45

10 5.5 - 11.4 x 10-5 8,530,370 9 - 26

20 6.9 - 13.9 x 10-5 3,579,085 4 - 15

1The bladder cancer risks presented in this table provide our “best” estimates at this time. Actual risks could be

lower, given the various uncertainties discussed, or higher, as these estimates assume that the probability of illness

from arsenic exposure in the U.S. is equal to the probability of death from arsenic exposure among the Taiwanese

study group.
Chapter 8, Economic Impact Analyses 8-42 Proposed Arsenic in Drinking Water Rule RIA

Exhibit 8-33

Annual Bladder Cancer Cases Avoided from Reducing Arsenic in CWSs1

Arsenic Level

(μg/L)

Total Bladder Cancer

Cases Avoided

Reduced Mortality

Cases*

Reduced Morbidity

Cases*

3 22 - 52 6 - 14 16 - 39

5 16 - 45 4 - 12 12 - 33

10 9 - 26 2 - 7 7 - 19

20 4 - 15 1 - 4 3 - 11

* The lower-end estimate of bladder cancer cases avoided is calculated using the lower-end risk estimate (see

Exhibit 5-9) and assumes that the conditional probability of mortality among the Taiwanese study group was 100

percent. The upper-end estimate of bladder cancer cases avoided is calculated using the upper-end risk estimate

(see Exhibit 5-9) and assumes that the conditional probability of mortality among the Taiwanese study group was

80 percent.

**Assuming 20-year mortality rate in the U.S. of 26 percent.

Health benefit estimates for lung cancer were also quantified based on the “what if?” scenario,

where the risks of a fatal lung cancer case associated with arsenic are assumed to be 2-5 times

that of a fatal bladder cancer case. More detail on lung cancer health benefits is provided in

Chapter 5, “Benefits Analysis.” Exhibit 8-34 shows the resulting annual lung cancer cases

avoided as a result of the “what if?” scenario analysis.

Exhibit 8-34

Potential Annual Lung Cancer Cases Avoided from Reducing Arsenic in CWSs

Arsenic Level

(μg/L)

Total Lung Cancer

Cases Avoided

Reduced Mortality

Cases*

Reduced Morbidity

Cases*

3 8 - 80 7 - 70 1 - 10

5 6 - 68 5 - 60 1 - 8

10 3 - 40 3 - 35 0 - 5

20 2 - 23 1 - 20 0 - 3

The Agency has developed monetized estimates of the health benefits associated with the risk

reductions from arsenic exposures. The approach used in this analysis for the measurement of

health risk reduction benefits is the monetary value of a statistical life (VSL) applied to each fatal

cancer avoided. For non-fatal cancers, willingness to pay (WTP) data to avoid chronic bronchitis

is used as a surrogate to estimate the WTP to avoid non-fatal bladder cancers. A WTP central

tendency estimate of $607,162 (May 1999$) is used to monetize the benefits of avoiding nonfatal cancers (this value was updated from the $536,000 value EPA updated to 1997$ from the

Viscusi et al. 1991 study). The bladder cancer, lung cancer, and non-quantifiable health benefits

are summarized in Exhibit 8-35. Total annual health benefits resulting from bladder cancer cases

avoided range from $43.6 to $104.2 million at an MCL of 3 μg/L, $31.7 to $89.9 million at an

MCL of 5 μg/L, $17.9 to $52.1 million at an MCL of 10 μg/L, and $7.9 to $29.8 million at an

MCL of 20 μg/L. Potential annual health benefits resulting from lung cancer cases avoided range

from $47.2 to $448.0 million at an MCL of 3 μg/L, $35.0 to $384.0 million at an MCL of 5
Chapter 8, Economic Impact Analyses 8-43 Proposed Arsenic in Drinking Water Rule RIA

μg/L, $19.6 to $224.0 million at an MCL of 10 μg/L, and $8.8 to $128.0 million at an MCL of

20 μg/L.

Exhibit 8-35

Estimated Monetized Total Cancer Health Benefits and

Non-Quantifiable Health Benefits from Reducing Arsenic in CWSs

Arsenic

Level 

(μg/L)

Annual

Bladder Cancer

Health Benefits

($millions)1,2

“What-if” Scenario and Potential Non-Quantifiable Health

Benefits

“What-if” Scenario

Annual

Lung Cancer

Health Benefits

($millions)1,3

Potential Non-Quantifiable

Health Benefits

3 $43.6 - $104.2 $47.2 - $448.0

• Skin Cancer

• Kidney Cancer

• Cancer of the Nasal Passages

• Liver Cancer

• Prostate Cancer

• Cardiovascular Effects

• Pulmonary Effects

• Immunological Effects

• Neurological Effects

• Endocrine Effects

• Reproductive and Developmental

Effects

5 $31.7 - $89.9 $35.0 - $384.0

10 $17.9 - $52.1 $19.6 - $224.0

20 $7.9 - $29.8 $8.8 - $128.0

1. May 1999 dollars.

2. The lower-end estimate is calculated using the lower-end number of bladder cancer cases avoided (see

Exhibit 5-12) and assumes that the conditional probability of mortality among the Taiwanese study group was

100 percent. The upper-end estimate is calculated using the upper-end number of cancer cases avoided (see

Exhibit 5-12) and assumes that the conditional probability of mortality among the Taiwanese study group was 80

percent.

3. These estimates are based on the “what if” scenario for lung cancer, where the risks of a fatal lung cancer

case associated with arsenic are assumed to be 2-5 times that of a fatal bladder cancer case.

Reductions in arsenic exposures may also be associated with non-quantifiable benefits. EPA has

identified several potential non-health non-quantifiable benefits associated with regulating arsenic

in drinking water. These benefits may include any customer peace of mind from knowing that

their drinking water has been treated for arsenic. To the extent that the Arsenic Rule can reduce

households’ perception of the health risks associated with arsenic in drinking water, household

averting actions and costs to avoid these risks, such as buying bottled water or installing home

treatment systems, could also be reduced.

8.10.2 Quantifiable and Non-Quantifiable Costs

The costs of reducing arsenic to various levels are summarized in Exhibit 8-36, which shows that,

as expected, aggregate arsenic mitigation costs increase with decreasing arsenic levels. Total

national costs at a 7 percent discount rate range are: $753.2 million per year at 3 μg/L; $442.2

million per year at 5 μg/L; $192.4 million per year at 10 μg/L; $73.7 million per year at 20 μg/L. 
Chapter 8, Economic Impact Analyses 8-44 Proposed Arsenic in Drinking Water Rule RIA

Discount Rate 3% 7% 3% 7% 3% 7%

System Costs

Treatment $639.2 $746.4 -- -- $639.2 $746.4

Monitoring/ 

Administrative

$2.2 $3.0 $0.9 $1.1 $3.1 $4.1

State Costs $1.6 $1.9 $0.6 $0.7 $2.2 $2.6

TOTAL COST $643.1 $751.4 $1.5 $1.8 $644.6 $753.2

System Costs

Treatment $374.0 $436.0 -- -- $374.0 $436.0

Monitoring/ 

Administrative

$2.0 $2.8 $0.9 $1.1 $2.9 $3.9

State Costs $1.3 $1.6 $0.6 $0.7 $2.0 $2.3

TOTAL COST $377.3 $440.4 $1.6 $1.8 $378.9 $442.2

System Costs

Treatment $160.4 $186.7 -- -- $160.4 $186.7

Monitoring/ 

Administrative

$1.8 $2.5 $1.0 $1.1 $2.8 $3.7

State Costs $1.1 $1.3 $0.6 $0.7 $1.7 $2.1

TOTAL COST $163.3 $190.5 $1.6 $1.9 $164.9 $192.4

System Costs

Treatment $58.9 $68.3 -- -- $58.9 $68.3

Monitoring/ 

Administrative

$1.7 $2.4 $1.0 $1.1 $2.7 $3.5

State Costs $1.0 $1.2 $0.7 $0.7 $1.6 $1.9

TOTAL COST $61.6 $71.8 $1.6 $1.9 $63.2 $73.7

*Costs include treatment, O&M, monitoring, and administrative costs to CWSs, monitoring and administrative costs to 

NTNCWSs, and State costs for administration of water programs.

MCL =20 μg/L

CWS

MCL = 3 μg/L

MCL =5 μg/L

MCL = 10 μg/L

NTNC* TOTAL

Exhibit 8-36

Summary of the Total Annual National Costs of Compliance

($ millions)
Chapter 8, Economic Impact Analyses 8-45 Proposed Arsenic in Drinking Water Rule RIA

3 5 10 20

<100 $368.13 $363.65 $357.17 $348.72

101-500 $258.68 $253.64 $246.38 $237.67

501-1,000 $106.07 $103.74 $98.35 $93.25

1,001-3,300 $63.61 $60.38 $56.51 $51.80

3,301-10,000 $44.28 $40.77 $37.04 $32.52

10,001-50,000 $36.39 $33.22 $29.13 $24.99

50,001-100,000 $29.52 $26.64 $22.80 $19.44

100,001-1,000,000 $23.47 $21.20 $18.32 $15.41

1,000,000 + $2.70 $1.73 $0.89 $0.55

All categories $43.73 $39.18 $33.05 $23.62

MCL (μg/L)

SIZE CATEGORIES

Exhibit 8-37

Mean Annual Costs per Household in CWSs

The cost impact of reducing arsenic in drinking water at the household level was also assessed. 

Exhibit 8-37 examines the cost per household for each system size category. As shown in the

table, costs per household decrease as system size increases. However, costs per household do

not vary significantly across arsenic levels. This is because costs do not vary significantly with

removal efficiency; once a system installs a treatment technology to meet an MCL, costs based

upon the removal efficiency that the treatment technology will be operated under remain relatively

flat. Per household costs are, however, somewhat lower at less stringent arsenic levels. This is

due to the assumption that some systems would blend water at these levels and treat only a

portion of the flow in order to meet the target MCL. 
Chapter 8, Economic Impact Analyses 8-46 Proposed Arsenic in Drinking Water Rule RIA

Arsenic Level 

(μg/L) lower bound** upper bound**

3 $ 29.4 $ 12.3

5 $ 23.8 $ 8.4

10 $ 18.3 $ 6.3

20 $ 15.9 $ 4.2

3 $ 34.4 $ 14.4

5 $ 27.7 $ 9.8

10 $ 21.4 $ 7.3

20 $ 18.6 $ 4.9

3% Discount Rate

7% Discount Rate

*Costs all treatment, O&M, monitoring, and administrative costs to CWSs, 

monitoring and administrative costs to NTNCWSs, and State costs for 

administration of water programs.

**Lower/upper bounds correspond to estimates of bladder cancer cases avoided.

Exhibit 8-38

Cost per Bladder Cancer Case Avoided for the Proposed Arsenic Rule

(CWSs Comply with MCL / NTNCs Monitor, in $ millions)

Exhibit 8-38 illustrates the cost per bladder cancer case avoided, based on national cost estimates

which include all the costs of treatment, O&M, monitoring and administrative costs to CWSs,

monitoring and administrative costs to NTNCWSs, and all State costs for administration of water

programs. At a 3 percent discount rate, cost per case ranges from approximately $29.4 million at

an arsenic level of 3 μg/L (lower bound estimate of avoided bladder cancer cases) to $4.2 million

at an MCL of 20 μg/L (upper bound of avoided bladder cancer cases). Similarly the range at a 7

percent discount rate is $34.3 million to $4.9 million.
References R-1 Proposed Arsenic in Drinking Water Rule RIA.

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Gunn, TM, et al. 1992. Further genetic studies of the cause of exancephaly in SELH mice.

Teratology. 45:679-86.

International Consultants, Inc. (ICI) and Malcolm Pirnie, Inc. (MPI) (1999). Technologies and

Costs for the Removal of Arsenic from Drinking Water, Prepared for the United States

Environmental Protection Agency, Office of Ground Water and Drinking Water,

Standards and Risk Management Division, Targeting and Analysis Branch, April 1999.

Jha, AN, et al. 1992. Genotoxic effects of sodium arsenite on human cells. Mutat Res. 1992

284:(2):215-21.

Kapadia, Amit 1999a. E-mail from Amit Kapadia, USEPA to Michael Muller, Abt Associates,

July 1.

Kapadia, Amit 1999b. Telephone conversation between Amit Kapadia, USEPA and Michael

Muller, Abt Associates, July.

Leonard, A and Lauwerys, RR. 1980. Carcinogenicity, teratogenicity and mutagenicity of arsenic.

Mutat Res. 75(1):49-62.
References R-3 Proposed Arsenic in Drinking Water Rule RIA.

Li, W and Chou, IN. 1992. Effects of sodium arsenite on the cytoskeleton and cellular glutathione

levels in cultured cells. Toxicol Appl Pharmacol 114(1): 132-9.

Morris-Kay, GM, et al. 1994. Normal neurulation in mammals. In Ciba Foundation Symposium,

neural tube defects. New York: John Wiley & Sons, 51-69.

Mottet, NK and Ferm, VH. 1983. The congenital teratogenicity and perinatal toxicity of metals. 

In reproduction and development toxicity of metals. Clarkson TW, Nordberg GF, and

Sager, PR, eds. New York: Plenum Press, 93-125.

National Academy of Sciences. 1995. Risk Assessment in the Federal Government.

National Cancer Institute. 1999.

National Research Council. 1999. Arsenic in Drinking Water.

Petres, J, et al. 1977. Effects of arsenic cell metabolism and cell proliferation: cytogenetic and

biochemical studies. Environ. Health Perspect. 19:223-7.

Scheonwolf, GC and Smith, JL. 1990. Mechanisms of neurulation: traditional viewpoint and

recent advances. Development. 109:243-270.

SDWIS, 1998. December 1998 freeze.

Smith, Ben 1999a. Facsimile from Ben Smith, USEPA to Michael Muller, Abt Associates, June

30.

Somogyi, A and Beck, H. 1991. Nurturing and breast-feeding exposure to chemicals in breast

milk. International Workshop on the Impact of the Environment on Reproductive Health,

Copenhagen, Denmark, September 30-October 4, 1991. Environ Health Perspect 101

(suppl.2): 45-52.

Subramanian, K.S., T. Viraraghavan, T. Phommavong and S. Tanjore (1997). "Manganese

Greensand for Removal of Arsenic in Drinking Water," Water Quality Research Journal

Canada, 32:3:551-561.

Taubeneck, MW, et al. 1994. Altered material zinc metabolism following exposure to diverse

developmental toxicants. Reprod Toxicol 8(1):25-40.

Tsai, SM, et al. 1999. Mortality for certain diseases in areas with high levels of arsenic in drinking

water. Arch Environ Health. 54(3):186-93.
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Vahter, M. and Marafante, E. 1987. Effects of low dietary intake methionine, choline, or proteins

on the biotransformation of arsenite in the rabbit. Toxiol Lett. 37: 41-46.

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Appendix A, Decision Tree and Decision Matrix A-1 Proposed Arsenic in Drinking Water Rule RIA

Appendix A: Decision Tree and Decision Matrix

A.1 Introduction

The purpose of this appendix is to present the rationale behind the development of the decision

tree and associated decision matrix. It includes an overview of the decision tree structure and

major factors impacting the decision- making process. The following list outlines the contents of

this appendix:

A.2 BACKGROUND - Presents a brief history of the arsenic regulation and the

statutory requirements impacting EPA and the decision-making process.

A.3 DECISION TREE OVERVIEW - Outlines the decision tree and presents major

factors affecting the decision-making process.

A.4 MAJOR FACTORS AFFECTING THE DECISION TREE - Presents the

rationale for selecting parameters which impact the decision tree, including MCL,

population, water type, region, and co-occurrence of solutes.

A.5 ADDITIONAL FACTORS AFFECTING THE DECISION TREE - Presents

other parameters in the process which impact the decision tree, including: corrosion

control, pre-oxidation, regionalization, and alternative technologies.

A.6. ARSENIC RULE-MAKING DECISION MATRIX - Complete copy of the

decision matrix developed for the arsenic rule-making process. These are provided in

Exhibits A-2 through A-17.

A.7. REFERENCES.

A.2 Background

In 1998 and 1999, EPA conducted technology and cost evaluations for the removal of arsenic

from drinking water. These evaluations looked into the effectiveness of various removal

technologies and the capital and operations and maintenance (O&M) costs associated with each

process. The following were evaluated and determined effective to varying degrees:

• Coagulation/Filtration (C/F);

• Modified Coagulation/Filtration (modifications to existing C/F plants);

• Direct Filtration (DF);

• Coagulation Assisted Microfiltration (CMF);

• Lime Softening (LS);

• Modified Lime Softening (modifications to existing LS plants);
Appendix A, Decision Tree and Decision Matrix A-2 Proposed Arsenic in Drinking Water Rule RIA

• Activated Alumina (AA);

• Ion Exchange (IX);

• Ultrafiltration (UF);

• Nanofiltration (NF);

• Reverse Osmosis (RO); 

• Greensand Filtration (GF); and

• Point-of-Entry (POE) and Point-of-Use (POU) Treatment Options.

The technology and cost evaluation yielded a document entitled Technologies and Costs for the

Removal of Arsenic From Drinking Water (ICI and MPI, 1999). The document includes detailed

evaluations of the above technologies, capital and O&M cost estimates for each of the listed

technologies, as well as other technologies that were considered ineffective or unproven.

EPA used the information contained in the technologies and costs (T&C) document to develop a

regulatory decision tree. The decision tree was then used to fashion a decision matrix which

contains the probability that a given system will choose a treatment technology based on the

percent removal required to meet the proposed MCL. The decision matrix, unit cost curves for

treatment and waste disposal (illustrated in the T&C), treatment-in-place data and occurrence

estimates will be used to develop national cost of compliance estimates. 

A.3 Decision Tree Overview

The decision tree is a flow chart that details the thought process involved in estimating which

treatments will be installed to comply with the four MCL options. The decision tree was

developed under the overriding assumption that systems would attempt to comply with the

proposed MCL by choosing the lowest cost approach. However, it was also recognized that

some systems may not be able to choose the lowest cost technology, because they face certain

constraints. Therefore, the “branches” of the decision tree represent constraining factors that

must be taken into consideration when estimating which treatment technology a system will

select. The following questions were used to define the branches of the decision tree. A detailed

explanation of the rationale behind each question is presented in the next section.

1. What is the target MCL?

2. What is the influent arsenic concentration of the system?

3. What is the population of the system?

4. In what region of the country is the system located?

5. Does the system utilize ground or surface water?

6. Does the system currently have some type of treatment in place?
Appendix A, Decision Tree and Decision Matrix A-3 Proposed Arsenic in Drinking Water Rule RIA

7. Are there any co-occurrence issues that preclude the use of a particular treatment

technology?

8. What disposal options are available for the treatment technology selected?

Even though these eight questions represent major decisions within the decision tree structure and

each question must be answered to complete a branch of the tree, the tree was structured to limit

the number of branches that must be considered during the development of the decision matrix. 

By first selecting the target MCL and influent arsenic concentration, some branches of the tree are

eliminated early in the process. For example, if the target MCL is 20 Fg/L and the influent arsenic

levels are between 10 and 20 Fg/L, no removal is necessary, and therefore the probability of

choosing any treatment technology is zero. Similar logic was applied to other decisions factors.

A.4 Major Factors Affecting the Decision Tree

This section explains the rationale behind selecting each particular decision factor. Specifically,

this section will discuss the following:

• the MCL target, 

• influent arsenic concentration, 

• population, 

• region where the system is located, 

• source water, 

• whether a system has existing treatment in place, 

• co-occurrence of solutes, and 

• waste disposal issues.

A.4.1 MCL Target

The MCL target is the single most important factor in development of the decision tree because it

is essential for determining all other branches of the tree. The decision tree is structured such

that selection of the target MCL is the first step in the decision process. Four MCL scenarios

will be analyzed as part of the regulatory development process (3 Fg/L, 5 Fg/L, 10 Fg/L, and 20

Fg/L).

A.4.2 Influent Arsenic Concentration

When coupled with the MCL target, the influent arsenic concentration was of major importance in

developing the decision tree. In developing the decision tree, influent arsenic concentrations were

grouped into four categories: less than 10 Fg/L, 10 to 20 Fg/L, 20 to 30 Fg/L, and 30 to 50 Fg/L. 

Given the MCL under consideration, the influent arsenic concentration determines what percent

removal of arsenic is needed, if any, and lays the groundwork for remaining decisions in the tree. 

Percent removal is critical for determining what additional technologies may be feasible. For

example, if a surface water plant has an influent arsenic level of 50 Fg/L, and the target MCL is 2
1Required removal percentages in the decision tree are based on worst cast scenarios and therefore

correspond with the upper bound of the arsenic concentration range for each category.

Appendix A, Decision Tree and Decision Matrix A-4 Proposed Arsenic in Drinking Water Rule RIA

Fg/L, then 96 percent removal is required.1 Research indicates that lime softening is only capable

of achieving approximately 80 percent removal; thus, lime softening would not be a viable

treatment option in this branch of the decision tree. Likewise, in the decision matrix, the

probability of choosing lime softening as a treatment technology would be zero whenever the

percent removal is over 80 percent.

A.4.3 System Size

System size, or population, also plays a significant role in determining the treatment options

available to a system, as well as the affordability of a particular technology for a system. EPA 

established nine size categories to be used in the decision tree and RIA process: 

1. 25 to 100; 

2. 101-500;

3. 501-1,000;

4. 1,001-3,300; 

5. 3,301-10,000; 

6. 10,001-50,000; 

7. 50,001-100,000; 

8. 100,001-1,000,000; and 

9. greater than 1,000,000. 

In developing the decision tree EPA grouped size categories one through three (25 to 1,000

people) and four though eight (1,001 to 1,000,000 people) because POE and POU treatment

options are considered viable treatment alternatives only for the three smallest categories. With

these groupings, the available technologies are constant for each of the size categories within each

group. However, the probability of choosing a given technology is still assigned dependent on

system size category. Therefore, in the development of the decision matrix, the probabilities that

certain technologies are chosen change for each of the size categories. Hence, the decision matrix 

accommodates each of the eight size categories (one through eight) individually. Systems within

the ninth size category (greater than 1,000,000) will be addressed on a case-by-case basis by EPA,

and will fall outside the scope of the decision tree process.

A.4.4 Region

The region of the nation that a system resides in does not effect the treatment options available. 

Therefore, the decision tree is structured in such a way that, regardless of the region, the branches

are identical, and in fact refer to the same pages within the decision tree. However, the number of

systems that may select a particular option as defined in the decision matrix, is region-specific. 

EPA has decided that the nation can be divided into three regions for the purpose of the decision
Appendix A, Decision Tree and Decision Matrix A-5 Proposed Arsenic in Drinking Water Rule RIA

making process: 1) Southwest Region; 2) Northwest Region; and 3) East Region. The regions

were selected based upon availability of water (i.e., scarcity of water) and availability of land. In

the Southwest Region, for example, water may be scarce and treatment technologies that generate

large volumes of reject water, such as RO, may not be appropriate. In the East Region, water

scarcity is much less a concern than the availability of land. Technologies or disposal options that

require significant amounts of land are less likely to be utilized in the East Region. The

Northwest Region, by comparison, is less affected by the scarcity of water or land availability than

either of the other two regions.

A.4.5 Source Water 

The source of the system’s raw water, either ground water or surface water, plays a major role in

determining the technologies that may already be in use by a system and what treatment options

are available if a system needs to install a new treatment facility.

For example, greensand filtration is affected by the level of iron in the raw water. Influent levels

greater than 300 mg/L (ppm) are conducive to removal of arsenic by greensand filtration. Surface

waters typically have low iron content, whereas ground waters often have levels in excess of 300

mg/L (Subramanian, et al., 1997). Accordingly, greensand filtration was not considered a viable

removal technology for surface water systems.

To determine the types of treatment that are currently being utilized throughout the country, EPA

reviewed the Community Water Systems Survey (CWSS). EPA determined there are few

surface water systems utilizing RO, IX or AA. As a result, when approximating the treatment in

place options, RO, IX, and AA were omitted for surface water systems.

Arsenic removal is significantly more efficient when arsenic is present as arsenate (As5+). 

Research has demonstrated many of the technologies considered perform poorly when arsenite

(As3+) is the predominant form (ICI and MPI, 1999). Arsenite can be easily oxidized to arsenate

using conventional oxidation methods, such as chlorination and potassium permanganate addition. 

Ground waters typically contain higher levels of As3+, whereas As5+ is the dominant species in

surface waters. As a result, ground waters are more likely to install pre-oxidation and use higher

oxidant doses, whereas surface waters may be able to get by with little or no pre-oxidation

capacity.

A.4.6 Systems with Treatment In-Place

If a system currently has treatment in-place it will significantly impact the decision tree. Many

existing treatment facilities will be able to achieve the necessary removal with little or no

modification, particularly at high MCLs. At the lower MCLs (2 and 5 Fg/L), existing facilities

may be able to add polishing steps or make some modifications to the existing system to achieve

the required removal level. Table 1 outlines the treatment technologies included in the decision

tree, the percent removal assumed capable without modification or polishing, and the maximum

percent removal.
Appendix A, Decision Tree and Decision Matrix A-6 Proposed Arsenic in Drinking Water Rule RIA

A.4.7 Systems without Treatment In-Place

Many factors affect the decision tree when considering the addition of a treatment option to

systems with no current treatment in place. Source water type and quality, system size, required

arsenic removal, and removal achievable by a particular technology are all major considerations. 

Many of these considerations have been discussed earlier in Section 4, however, source water

quality, i.e., co-occurrence of solutes, is discussed in Section 4.8.

For ground water systems (any size) without treatment in-place, the most suitable treatment

technologies are IX, AA and RO, though CF and LS may be used. CF and LS are best suited

for large surface water systems without treatment in-place while IX, AA and RO are best suited

for small surface water systems without treatment in-place. In either case, RO is not a suitable

treatment technology in regions where water is scarce. Modified CF and LS are for those surface

water systems that already have CF or LS in-place.

The SDWA identifies POE and POU treatment units as potentially affordable technologies, but

stipulates that POE and POU treatment systems “shall be owned, controlled and maintained by the

public water system, or by a person under contract with the public water system to ensure proper

operation and compliance with the maximum contaminant level or treatment technique and

equipped with mechanical warnings to ensure that customers are automatically notified of

operational problems.”

Preliminary affordability determinations have shown that POE and POU technologies will only be

considered viable for small systems. These determinations have shown the cost breakpoint to be

in the area of 200 persons served. This estimate does not account for waste disposal costs, which

would make central treatment estimates more expensive, thus increasing the breakpoint. As a

result, POE and POU units are only included in the decision tree for systems with populations

fewer than 1,000 individuals.
Appendix A, Decision Tree and Decision Matrix A-7 Proposed Arsenic in Drinking Water Rule RIA

Exhibit A-1

Treatment Technologies for Systems with Treatment In-Place and Percent Removals

Assumed and Achievable

Treatment Technology Percent Removal of

In-Place System

Maximum Percent

Removal1

Coagulation/Filtration2 50 95

Lime Softening2 50 80

Coagulation Assisted Microfiltration NA 90

Ion Exchange 95 >95

Activated Alumina 95 >95

Reverse Osmosis 95 >95

Greensand Filtration3 90 90

POE Activated Alumina NA >95

POU Ion Exchange NA >95

1 - For Percent Removals of In-Place Systems that are very close to Maximum Percent Removals (e.g., 95% and > 95%) polishing steps

may be required.

2 - Maximum Percent Removal involves modification to existing system in the form of additional chemical feed systems, pumping, piping,

etc.

3 - EPA is currently evaluating the removals achievable by this process. The final decision matrix may reflect significantly lower removals,

e.g., 50%.

NA - Not Applicable

A.4.8 Co-Occurrence of Solutes

There are a number of solutes and water quality parameters that may effect the viability of a

particular treatment option. Total dissolved solids (TDS), silica, sulfate and iron can all be major

detractors/benefactors for the use of a particular technology. The decision tree simply cannot

account for each individual situation where the influent water quality plays a role in selecting the

treatment option. Utilities are encouraged to read the T&C document (ICI and MPI, 1999) to

gather additional information on parameters which impact the performance of a particular

technology.

The decision tree uses influent sulfate and iron levels as decision factors in selecting treatment

technologies. Sulfate has been shown to decrease the effectiveness of ion exchange processes for

arsenic removal; therefore, these processes are not generally recommended where influent sulfate

levels exceed 120 mg/L (Clifford, et al., 1998). Iron, on the other hand, significantly improves the

effectiveness of greensand filtration (Subramanian, et al., 1997). Greensand filtration is best

suited for ground waters (which typically contain higher levels of iron than surface waters) with

high influent levels of iron (300 mg/L).

The decision tree has been structured to accommodate the impact of sulfate and iron on treatment
Appendix A, Decision Tree and Decision Matrix A-8 Proposed Arsenic in Drinking Water Rule RIA

effectiveness. For ground water sources, both sulfate and iron levels are considered. Ion

exchange is not considered a feasible treatment option when sulfate levels exceed 120 mg/L, and

greensand filtration is not considered viable when the iron level falls below 300 mg/L. For surface

waters in which high iron levels are rare, only sulfate has been considered. For purposes of

approximating national cost, greensand filtration is not considered a treatment option for surface

water systems. Ion exchange is not considered a feasible treatment option when the sulfate level

exceeds 120 mg/L. Therefore, in the development of the decision matrix, the probability that a

system will choose a particular technology is assumed with an eye on the regional levels of iron

and sulfate.

A.4.9 Waste Disposal

Waste handling and disposal options are specific to the treatment technology selected and the

availability of disposal options does not vary by system size in the decision tree. However, the

probability that a system will utilize a particular option does vary with system size. For example,

evaporation ponds may not be suitable for large systems in the Northwest Region where climatic

conditions do not facilitate evaporation. Mechanical dewatering devices can be expensive and

may require significant operator attention and may not be suitable for small systems.

A.4.9.1 Mechanical Dewatering

Mechanical dewatering processes include centrifuges, vacuum-assisted dewatering beds, belt filter

presses, and plate and frame filter presses. Such processes generally have high capital, as well as

high O&M costs, compared to similar capacity non-mechanical dewatering processes (e.g.,

storage lagoons). Due to the high costs, such processes are generally not suitable for application

with very small water systems.

Filter presses have been used in industrial processes for years and have been increasing in the

water treatment industry over the past several years. The devices have been successfully applied

to both lime softening process sludge and coagulation/filtration process sludge. Filter presses

require little land, have high capital costs, and are labor intensive. 

Centrifuges have also been used in the water industry for years. Centrifugation is a continuous

process requiring minimal time to achieve the optimal coagulation/filtration. Centrifuges have low

land requirements and high capital costs. They are more labor intensive than non-mechanical

alternatives, but less intensive than filter presses. Again, due to the capital and O&M

requirements, centrifuges are more suitable for larger water systems.

A.4.9.2 Evaporation Ponds and Drying Beds

Evaporation ponds and drying beds are non-mechanical dewatering technologies wherein

favorable climatic conditions are used to dewater waste brines generated by treatment processes

such as reverse osmosis and ion exchange. Ponds and drying beds are not generally suitable for

lime softening or coagulation/filtration. Evaporation is an extremely land intensive waste handling

option requiring shallow basins with large surface areas which can be an important consideration

in densely populated regions. Evaporation ponds and drying beds have few operation and
Appendix A, Decision Tree and Decision Matrix A-9 Proposed Arsenic in Drinking Water Rule RIA

maintenance requirements but are only feasible in regions with high temperatures, low humidity,

and low precipitation.

A.4.9.3 Storage Lagoons

Lagoons are the most common, and often least expensive, method to thicken or dewater

treatment sludge, however, they are land intensive. Storage lagoons are best suited for

dewatering lime softening process sludge, though they have been applied with some success to

coagulation/filtration process sludge. Coagulation/filtration process sludge do not typically

dewater well in storage lagoons. Thickened coagulation/filtration process sludge can be difficult

to remove from lagoons and often require dredging or vacuum pumping by knowledgeable

experts. 

Since lagooning is a land intensive process, it has limited applicability in densely populated

regions, or regions with limited land availability. Lagoons are best suited for areas with favorable

climatic conditions, i.e., high temperatures, low humidity, and low precipitation. In fact, in

northern climates, winter freezing can dehydrate coagulation/filtration sludge.

A.4.9.4 Direct Discharge

Direct discharge to a surface water body is a common method of disposal for water treatment

byproducts. No pretreatment or concentration of the byproduct stream is necessary prior to

discharge, and the receiving water dilutes the waste concentration and gradually incorporates the

sludge or brine. The primary cost associated with direct discharge is that of the piping. Direct

discharge requires little oversight and operator experience and maintenance are minimal. This

method has been used to successfully dispose of lime softening and coagulation/filtration process

sludge materials, as well as brine streams generated at reverse osmosis and ion exchange water

plants.

A.4.9.5 POTW Discharge

Indirect discharge (POTW discharge) is a commonly used method of disposal for filter backwash

and brine waste streams. Coagulation/filtration and lime softening sludge materials have also been

successfully disposed of in this manner. The primary cost associated with POTW discharge is that

of the piping. Additional costs associated with POTW discharge may include lift stations,

additional piping for access to the sewer system, and any cost incurred by the POTW in

accommodating the increased demands on the POTW.

A.4.9.6 Dewatered Sludge Land Application

Dewatered sludge can be disposed of by spreading the material over an approved land surface. 

Land application is limited by the availability of land. In areas where grassland, farmland, or

forested land is unavailable, transportation can significantly affect the cost effectiveness of this

disposal option. Land application can be a means of final disposing of lime softening sludge, and

to a lesser degree, coagulation/filtration sludge. Lime softening sludge can be used to neutralize
Appendix A, Decision Tree and Decision Matrix A-10 Proposed Arsenic in Drinking Water Rule RIA

soil pH while coagulation/filtration sludge offer no benefit to soil chemistry and are generally used

as fill material.

A.4.9.7 Sanitary Landfill Disposal

Two forms of sanitary landfill are commonly used for disposal of water treatment byproducts:

monofills and commercial nonhazardous waste landfills. In some parts of the country, decreasing

landfill availability, rising costs, and increasing regulations are making landfill disposal more

expensive. Costs associated with the development of monofills are generally less than those

associated with commercial nonhazardous water landfill. 

A.5 Additional Factors Affecting the Decision Tree

A.5.1 Pre-Oxidation

As mentioned above, inorganic arsenic occurs in two primary valence states, arsenite (As III) and

arsenate (As V). As(III) is dominant in ground waters while surface waters more typically

contain As(V). As(III) is easily oxidized to As(V) by conventional oxidation technologies such as

chlorination and potassium permanganate addition. Each of the treatment technologies

considered in the decision tree remove As(V) more readily than As(III) and as a result, preoxidation may be necessary depending upon source water conditions.

Pre-oxidation is included in the decision tree for all treatment technologies. Systems without

treatment in-place may already be chlorinating which may meet pre-oxidation requirements. For

those systems, pre-oxidation may or may not need to be installed. Similarly, systems with

treatment in-place may have pre-oxidation in-place which could meet the pre-oxidation

requirements. For single-house (POE) or single tap (POU) treatment options, centralized preoxidation is required.

A.5.2 Corrosion Control

Many of the treatment technologies considered in the decision tree (e.g., LS, AA, IX, and RO) 

remove hardness and alkalinity. Removal of hardness and alkalinity can reduce the pH of finished

water and lead to corrosion problems within the system. Hardness and alkalinity, at the

appropriate levels, act as buffers against corrosion in the treatment plant and distribution system. 

At these levels, alkalinity and hardness form protective coatings (metal hydroxides), control pH

and enhance the buffer effect against corrosion. Corrosion control is included in the decision tree

for all new constructions, that is, systems without existing treatment plants. It was assumed that

existing plants had adequate corrosion control in-place.

A.5.3 Regionalization

The term regionalization is used to define the process of purchasing water or transporting water

from one community to another. Numerous operational and other factors including 
Appendix A, Decision Tree and Decision Matrix A-11 Proposed Arsenic in Drinking Water Rule RIA

1) the availability of water, 

2) water quality, 

3) geography, and 

4) economic factors influence the decision to implement regionalization. 

Water quality also plays a role in the decision-making process. For example, if a community’s

source water is contaminated, it may be less expensive for the community to purchase water from

another community than to treat its own water source. Regionalization is considered an option

only for small systems (<1mgd) in the decision tree.

A.5.4 Alternative Technologies

Technologies and Costs for the Removal of Arsenic from Drinking Water (ICI and MPI, 1999)

evaluated four arsenic removal technologies that were not included in the decision tree: 

1) Sulfur-Modified Iron, 

2) Granular Ferric Hydroxide, 

3) Iron Filings, and 

4) Iron Oxide Coated Sand. 

The technologies were not included in the decision tree for reasons which are summarized below. 

A.5.4.1 Sulfur-Modified Iron

A patented Sulfur-Modified Iron (SMI) process for arsenic removal has recently been developed. 

During this process, powdered iron, powdered sulfur, and the oxidizing agent (H2O2 in

preliminary tests) are thoroughly mixed and added to the water to be treated. The oxidizing agent

serves to convert As(III) to As(V). Arsenic removal utilizing the SMI process seems to be 

dependent on the iron to arsenic level as well as pH. Flow distribution problems were evident, as

several columns became partially plugged during operation.

All experimentation on the SMI process has been at the bench-scale level, and involves only batch

processes. The literature is unclear about removal efficiency since results varied from less than 10

to 99 percent, depending on conditions. It appears that O&M for such a system would be

expensive and would require a highly trained operator. Finally, by the admission of the

researchers, disposal costs might outweigh the increased adsorption capacity.

A.5.4.2 Granular Ferric Hydroxide

A new removal technique for arsenate is adsorption by granular ferric hydroxide (GFH) in fixed

bed reactors. Although the competition of sulfate on arsenate adsorption was not very strong,

phosphate competed strongly with arsenate which reduced arsenate removal with GFH. 
Appendix A, Decision Tree and Decision Matrix A-12 Proposed Arsenic in Drinking Water Rule RIA

Currently, GFH media costs approximately $4,000 per ton. In addition to the high cost of the

media, the direct deposition of spent GFH as hazardous waste is favored

A.5.4.3 Iron Filings

The Iron Filings process is essentially a filter technology, much like greensand filtration, wherein

the source water is filtered through a bed of sand and iron filings. Unlike some technologies (i.e.

ion exchange), sulfate is actually introduced in this process to encourage arsenopyrite

precipitation.

While this process seems to be quite effective, its use as a drinking water treatment technology

appears to be limited. There is no indication that this technology can reduce arsenic levels below

approximately 25 ppb. This technology also suffers from a study design which failed to test its

effectiveness at influent levels of concern in drinking water. Since the study design called for such

high influent levels - 470 to 20,000 ppb - there is no data to indicate how the technology performs

at normal source water arsenic levels, which most certainly are below the 470 ppb level used in

experimentation. This technology needs to be further evaluated before it should be recommended

as an approved arsenic removal technology for drinking water.

A.5.4.4 Iron Oxide Coated Sand

Iron oxide coated sand (IOCS) is a rare process that has shown some tendency for arsenic

removal. IOCS consists of sand grains coated with ferric hydroxide which are used in fixed bed

reactors to remove various dissolved metal species. Factors such as pH, arsenic oxidation state,

competing ions, EBCT, and regeneration time have significant effects on the removals achieved

with IOCS. Like other processes, the media must be regenerated upon exhaustion. IOCS has

only limited experience having only been tested at bench-scale. High levels of arsenite could

reduce IOCS effectiveness because the bonding is strong and may permanently damage the media. 

Natural organic matter may also be problematic for arsenic removal. IOCS also takes a

considerable amount of time to produce in a laboratory setting. At full-scale this would likely

result in high capital cost. 

A.6 Arsenic Rule Making Decision Matrix

The actual decision tree is illustrated as a flow chart and occupies over 300 written pages. Rather

than include the decision tree as part of this appendix, the decision matrix is presented. The

decision matrix contains the actual assumptions regarding compliance decisions that were used to

estimate system compliance costs. The decision tree is presented in Exhibits A-2 to A-16. Each

exhibit provides the decision matrix for a particular source water and size category pair (e.g.

Exhibit A-2 contains the decision matrix for ground water systems serving fewer than 100

people). The first column described the treatment technology train associated with the row. The

next three columns present three different decision probabilities for each technology treatment

train, depending on the required percentage reduction in influent arsenic (e.g. in the cost analysis,

a system which needed to remove between 50 and 90 percent of the influent arsenic would have a

seven percent chance of choosing treatment technology train 24, Reverse Osmosis POU with precorrosion control).
No. Treatment Technology Train <50% 50-90% >90%

 1 Regionalization 0.0 0.0 0.0

 2 Alternate Source 0.0 0.0 0.0

 3 Modify Lime Softening and pre-oxidation 3.0 3.0 1.0

 4 Modify Coagulation/Filtration and pre-oxidation 2.0 2.0 1.0

 5 Anion Exchange (25 mg/l SO4) and POTW waste disposal and corrosion control and pre-oxidation 2.0 2.0 17.0

 6 Anion Exchange (150 mg/l SO4) and POTW waste disposal and corrosion control and pre-oxidation 0.0 0.0 0.0

 7 Anion Exchange (25 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 2.0 2.0 17.0

 8 Anion Exchange (150 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

 9 Activated Alumina (2,000 BV) and non-hazardous landfill (for spent media) and pre-oxidation 60.0 70.0 0.0

10 Activated Alumina (10,000 BV) and non-hazardous landfill (for spent media) and pre-oxidation 0.0 0.0 0.0

11 Reverse Osmosis and direct discharge waste disposal and corrosion control and pre-oxidation 0.0 0.0 0.0

12 Reverse Osmosis and POTW waste disposal and corrosion control and pre-oxidation 0.0 0.0 0.0

13 Reverse Osmosis and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

14 Coagulation Assisted Microfiltration and mechanical de-watering/non-hazardous landfill waste disposal and pre-oxidation 0.0 0.0 0.0

15 Coagulation Assisted Microfiltration and non-mechanical de-watering/non-hazardous landfill waste disposal and pre-oxidation 0.0 0.0 0.0

16 Oxidation Filtration (Greensand) and POTW for backwash stream 18.0 0.0 0.0

17 Anion Exchange (25 mg/l SO4) and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

18 Anion Exchange (150 mg/l SO4) and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

19 Activated Alumina (2,000 BV) and POTW/non-hazardous landfill and pre-oxidation 0.0 0.0 0.0

20 Activated Alumina (10,000 BV) and POTW/non-hazardous landfill and pre-oxidation 0.0 0.0 0.0

21 Anion Exchange (90 mg/l SO4) and POTW waste disposal and corrosion control and pre-oxidation 0.0 0.0 18.0

22 Anion Exchange (90 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 18.0

23 POE Activated Alumina and corrosion control and pre-oxidation 4.0 7.0 8.0

24 POU Reverse Osmosis and pre-oxidation 4.0 7.0 10.0

25 POU Activated Alumina and pre-oxidation 5.0 7.0 10.0

Sum of Probabilities: 100.00 100.00 100.00

Percent of Treatment Required to 

Achieve MCL

Exhibit A-2

Probability Decision Tree: Ground Water Systems Serving 100 People
No. Treatment Technology Train <50% 50-90% >90%

 1 Regionalization 0.0 0.0 0.0

 2 Alternate Source 0.0 0.0 0.0

 3 Modify Lime Softening and pre-oxidation 3.0 3.0 1.0

 4 Modify Coagulation/Filtration and pre-oxidation 4.0 4.0 2.0

 5 Anion Exchange (25 mg/l SO4) and POTW waste disposal and corrosion control and pre-oxidation 24.0 18.0 17.0

 6 Anion Exchange (150 mg/l SO4) and POTW waste disposal and corrosion control and pre-oxidation 0.0 0.0 0.0

 7 Anion Exchange (25 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 24.0 18.0 17.0

 8 Anion Exchange (150 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

 9 Activated Alumina (2,000 BV) and non-hazardous landfill (for spent media) and pre-oxidation 0.0 0.0 0.0

10 Activated Alumina (10,000 BV) and non-hazardous landfill (for spent media) and pre-oxidation 0.0 0.0 0.0

11 Reverse Osmosis and direct discharge waste disposal and corrosion control and pre-oxidation 0.0 0.0 0.0

12 Reverse Osmosis and POTW waste disposal and corrosion control and pre-oxidation 0.0 0.0 0.0

13 Reverse Osmosis and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

14 Coagulation Assisted Microfiltration and mechanical de-watering/non-hazardous landfill waste disposal and pre-oxidation 0.0 0.0 0.0

15 Coagulation Assisted Microfiltration and non-mechanical de-watering/non-hazardous landfill waste disposal and pre-oxidation 0.0 0.0 0.0

16 Oxidation Filtration (Greensand) and POTW for backwash stream 18.0 0.0 0.0

17 Anion Exchange (25 mg/l SO4) and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

18 Anion Exchange (150 mg/l SO4) and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

19 Activated Alumina (2,000 BV) and POTW/non-hazardous landfill and pre-oxidation 0.0 0.0 0.0

20 Activated Alumina (10,000 BV) and POTW/non-hazardous landfill and pre-oxidation 0.0 0.0 0.0

21 Anion Exchange (90 mg/l SO4) and POTW waste disposal and corrosion control and pre-oxidation 7.0 19.0 18.0

22 Anion Exchange (90 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 6.0 19.0 18.0

23 POE Activated Alumina and corrosion control and pre-oxidation 4.0 6.0 9.0

24 POU Reverse Osmosis and pre-oxidation 5.0 6.0 9.0

25 POU Activated Alumina and pre-oxidation 5.0 7.0 9.0

Sum of Probabilities: 100.00 100.00 100.00

Percent of Treatment Required to 

Achieve MCL

Exhibit A-3

Probability Compliance Decision Tree: Ground Water Systems Serving 101-500 People
No. Treatment Technology Train <50% 50-90% >90%

 1 Regionalization 0.0 0.0 0.0

 2 Alternate Source 0.0 0.0 0.0

 3 Modify Lime Softening and pre-oxidation 2.0 2.0 1.0

 4 Modify Coagulation/Filtration and pre-oxidation 2.0 2.0 1.0

 5 Anion Exchange (25 mg/l SO4) and POTW waste disposal and corrosion control and pre-oxidation 24.0 18.0 17.0

 6 Anion Exchange (150 mg/l SO4) and POTW waste disposal and corrosion control and pre-oxidation 0.0 3.0 13.0

 7 Anion Exchange (25 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

 8 Anion Exchange (150 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

 9 Activated Alumina (2,000 BV) and non-hazardous landfill (for spent media) and pre-oxidation 0.0 0.0 0.0

10 Activated Alumina (10,000 BV) and non-hazardous landfill (for spent media) and pre-oxidation 0.0 0.0 0.0

11 Reverse Osmosis and direct discharge waste disposal and corrosion control and pre-oxidation 0.0 0.0 0.0

12 Reverse Osmosis and POTW w aste disposal and corrosion control and pre-oxidation 0.0 0.0 0.0

13 Reverse Osmosis and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

14 Coagulation Assisted Microfiltration and mechanical de-watering/non-hazardous landfill waste disposal and pre-oxidation 0.0 0.0 0.0

15 Coagulation Assisted Microfiltration and non-mechanical de-w atering/non-hazardous landfill waste disposal and pre-oxidation 0.0 0.0 0.0

16 Oxidation Filtration (Greensand) and POTW for backw ash stream 18.0 0.0 0.0

17 Anion Exchange (25 mg/l SO4) and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 24.0 18.0 17.0

18 Anion Exchange (150 mg/l SO4) and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 0.0 19.0 13.0

19 Activated Alumina (2,000 BV) and POTW/non-hazardous landfill and pre-oxidation 0.0 0.0 0.0

20 Activated Alumina (10,000 BV) and POTW/non-hazardous landfill and pre-oxidation 0.0 0.0 0.0

21 Anion Exchange (90 mg/l SO4) and POTW waste disposal and corrosion control and pre-oxidation 15.0 19.0 19.0

22 Anion Exchange (90 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 15.0 19.0 19.0

23 POE Activated Alumina and corrosion control and pre-oxidation 0.0 0.0 0.0

24 POU Reverse Osmosis and pre-oxidation 0.0 0.0 0.0

25 POU Activated Alumina and pre-oxidation 0.0 0.0 0.0

Sum of Probabilities: 100.00 100.00 100.00

Percent of Treatment Required to 

Achieve MCL

Exhibit A-4

Probability Compliance Decision Tree: Ground Water Systems Serving 501-1,000 People 
No. Treatment Technology Train <50% 50-90% >90%

 1 Regionalization 0.0 0.0 0.0

 2 Alternate Source 0.0 0.0 0.0

 3 Modify Lime Softening and pre-oxidation 3.0 3.0 1.0

 4 Modify Coagulation/Filtration and pre-oxidation 3.0 3.0 1.0

 5 Anion Exchange (25 mg/l SO4) and POTW waste disposal and corrosion control and pre-oxidation 24.0 18.0 17.0

 6 Anion Exchange (150 mg/l SO4) and POTW waste disposal and corrosion control and pre-oxidation 0.0 0.0 13.0

 7 Anion Exchange (25 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

 8 Anion Exchange (150 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

 9 Activated Alumina (2,000 BV) and non-hazardous landfill (for spent media) and pre-oxidation 0.0 0.0 0.0

10 Activated Alumina (10,000 BV) and non-hazardous landfill (for spent media) and pre-oxidation 0.0 0.0 0.0

11 Reverse Osmosis and direct discharge waste disposal and corrosion control and pre-oxidation 0.0 0.0 0.0

12 Reverse Osmosis and POTW w aste disposal and corrosion control and pre-oxidation 0.0 0.0 0.0

13 Reverse Osmosis and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

14 Coagulation Assisted Microfiltration and mechanical de-watering/non-hazardous landfill waste disposal and pre-oxidation 8.0 10.0 0.0

15 Coagulation Assisted Microfiltration and non-mechanical de-w atering/non-hazardous landfill waste disposal and pre-oxidation 8.0 10.0 0.0

16 Oxidation Filtration (Greensand) and POTW for backw ash stream 18.0 0.0 0.0

17 Anion Exchange (25 mg/l SO4) and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 24.0 18.0 17.0

18 Anion Exchange (150 mg/l SO4) and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 13.0

19 Activated Alumina (2,000 BV) and POTW/non-hazardous landfill and pre-oxidation 0.0 0.0 0.0

20 Activated Alumina (10,000 BV) and POTW/non-hazardous landfill and pre-oxidation 0.0 0.0 0.0

21 Anion Exchange (90 mg/l SO4) and POTW waste disposal and corrosion control and pre-oxidation 6.0 19.0 19.0

22 Anion Exchange (90 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 6.0 19.0 19.0

23 POE Activated Alumina and corrosion control and pre-oxidation 0.0 0.0 0.0

24 POU Reverse Osmosis and pre-oxidation 0.0 0.0 0.0

25 POU Activated Alumina and pre-oxidation 0.0 0.0 0.0

Sum of Probabilities: 100.00 100.00 100.00

Percent of Treatment Required to 

Achieve MCL

Exhibit A-5

Probability Compliance Decision Tree: Ground Water Systems Serving 1,001-3,300 People
No. Treatment Technology Train <50% 50-90% >90%

 1 Regionalization 0.0 0.0 0.0

 2 Alternate Source 0.0 0.0 0.0

 3 Modify Lime Softening and pre-oxidation 3.0 3.0 1.0

 4 Modify Coagulation/Filtration and pre-oxidation 8.0 8.0 4.0

 5 Anion Exchange (25 mg/l SO4) and POTW waste disposal and corrosion control and pre-oxidation 24.0 18.0 17.0

 6 Anion Exchange (150 mg/l SO4) and POTW waste disposal and corrosion control and pre-oxidation 0.0 0.0 12.0

 7 Anion Exchange (25 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

 8 Anion Exchange (150 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

 9 Activated Alumina (2,000 BV) and non-hazardous landfill (for spent media) and pre-oxidation 0.0 0.0 0.0

10 Activated Alumina (10,000 BV) and non-hazardous landfill (for spent media) and pre-oxidation 0.0 0.0 0.0

11 Reverse Osmosis and direct discharge waste disposal and corrosion control and pre-oxidation 0.0 0.0 0.0

12 Reverse Osmosis and POTW w aste disposal and corrosion control and pre-oxidation 0.0 0.0 0.0

13 Reverse Osmosis and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

14 Coagulation Assisted Microfiltration and mechanical de-watering/non-hazardous landfill waste disposal and pre-oxidation 2.0 8.0 0.0

15 Coagulation Assisted Microfiltration and non-mechanical de-w atering/non-hazardous landfill waste disposal and pre-oxidation 3.0 7.0 0.0

16 Oxidation Filtration (Greensand) and POTW for backw ash stream 18.0 0.0 0.0

17 Anion Exchange (25 mg/l SO4) and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 24.0 18.0 17.0

18 Anion Exchange (150 mg/l SO4) and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 11.0

19 Activated Alumina (2,000 BV) and POTW/non-hazardous landfill and pre-oxidation 0.0 0.0 0.0

20 Activated Alumina (10,000 BV) and POTW/non-hazardous landfill and pre-oxidation 0.0 0.0 0.0

21 Anion Exchange (90 mg/l SO4) and POTW waste disposal and corrosion control and pre-oxidation 9.0 19.0 19.0

22 Anion Exchange (90 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 9.0 19.0 19.0

23 POE Activated Alumina and corrosion control and pre-oxidation 0.0 0.0 0.0

24 POU Reverse Osmosis and pre-oxidation 0.0 0.0 0.0

25 POU Activated Alumina and pre-oxidation 0.0 0.0 0.0

Sum of Probabilities: 100.00 100.00 100.00

Percent of Treatment Required to 

Achieve MCL

Exhibit A-6

Probability Compliance Decision Tree: Ground Water Systems Serving 3,301-10,000 People 
No. Treatment Technology Train <50% 50-90% >90%

 1 Regionalization 0.0 0.0 0.0

 2 Alternate Source 0.0 0.0 0.0

 3 Modify Lime Softening and pre-oxidation 5.0 5.0 2.0

 4 Modify Coagulation/Filtration and pre-oxidation 4.0 4.0 2.0

 5 Anion Exchange (25 mg/l SO4) and POTW waste disposal and corrosion control and pre-oxidation 24.0 18.0 17.0

 6 Anion Exchange (150 mg/l SO4) and POTW waste disposal and corrosion control and pre-oxidation 0.0 0.0 12.0

 7 Anion Exchange (25 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

 8 Anion Exchange (150 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

 9 Activated Alumina (2,000 BV) and non-hazardous landfill (for spent media) and pre-oxidation 0.0 0.0 0.0

10 Activated Alumina (10,000 BV) and non-hazardous landfill (for spent media) and pre-oxidation 0.0 0.0 0.0

11 Reverse Osmosis and direct discharge waste disposal and corrosion control and pre-oxidation 0.0 0.0 0.0

12 Reverse Osmosis and POTW w aste disposal and corrosion control and pre-oxidation 0.0 0.0 0.0

13 Reverse Osmosis and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

14 Coagulation Assisted Microfiltration and mechanical de-watering/non-hazardous landfill waste disposal and pre-oxidation 22.0 28.0 0.0

15 Coagulation Assisted Microfiltration and non-mechanical de-w atering/non-hazardous landfill waste disposal and pre-oxidation 21.0 27.0 0.0

16 Oxidation Filtration (Greensand) and POTW for backw ash stream 0.0 0.0 0.0

17 Anion Exchange (25 mg/l SO4) and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 24.0 18.0 17.0

18 Anion Exchange (150 mg/l SO4) and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 12.0

19 Activated Alumina (2,000 BV) and POTW/non-hazardous landfill and pre-oxidation 0.0 0.0 0.0

20 Activated Alumina (10,000 BV) and POTW/non-hazardous landfill and pre-oxidation 0.0 0.0 0.0

21 Anion Exchange (90 mg/l SO4) and POTW waste disposal and corrosion control and pre-oxidation 0.0 0.0 19.0

22 Anion Exchange (90 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 19.0

23 POE Activated Alumina and corrosion control and pre-oxidation 0.0 0.0 0.0

24 POU Reverse Osmosis and pre-oxidation 0.0 0.0 0.0

25 POU Activated Alumina and pre-oxidation 0.0 0.0 0.0

Sum of Probabilities: 100.00 100.00 100.00

Percent of Treatment Required to 

Achieve MCL

Exhibit A-7

Probability Compliance Decision Tree: Ground Water Systems Serving 10,001-50,000 People 
No. Treatment Technology Train <50% 50-90% >90%

 1 Regionalization 0.0 0.0 0.0

 2 Alternate Source 0.0 0.0 0.0

 3 Modify Lime Softening and pre-oxidation 3.0 3.0 1.0

 4 Modify Coagulation/Filtration and pre-oxidation 4.0 4.0 2.0

 5 Anion Exchange (25 mg/l SO4) and POTW waste disposal and corrosion control and pre-oxidation 23.0 18.0 17.0

 6 Anion Exchange (150 mg/l SO4) and POTW waste disposal and corrosion control and pre-oxidation 0.0 0.0 12.0

 7 Anion Exchange (25 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

 8 Anion Exchange (150 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

 9 Activated Alumina (2,000 BV) and non-hazardous landfill (for spent media) and pre-oxidation 0.0 0.0 0.0

10 Activated Alumina (10,000 BV) and non-hazardous landfill (for spent media) and pre-oxidation 0.0 0.0 0.0

11 Reverse Osmosis and direct discharge waste disposal and corrosion control and pre-oxidation 0.0 0.0 0.0

12 Reverse Osmosis and POTW w aste disposal and corrosion control and pre-oxidation 0.0 0.0 0.0

13 Reverse Osmosis and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

14 Coagulation Assisted Microfiltration and mechanical de-watering/non-hazardous landfill waste disposal and pre-oxidation 24.0 29.0 0.0

15 Coagulation Assisted Microfiltration and non-mechanical de-w atering/non-hazardous landfill waste disposal and pre-oxidation 23.0 28.0 0.0

16 Oxidation Filtration (Greensand) and POTW for backw ash stream 0.0 0.0 0.0

17 Anion Exchange (25 mg/l SO4) and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 23.0 18.0 17.0

18 Anion Exchange (150 mg/l SO4) and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 13.0

19 Activated Alumina (2,000 BV) and POTW/non-hazardous landfill and pre-oxidation 0.0 0.0 0.0

20 Activated Alumina (10,000 BV) and POTW/non-hazardous landfill and pre-oxidation 0.0 0.0 0.0

21 Anion Exchange (90 mg/l SO4) and POTW waste disposal and corrosion control and pre-oxidation 0.0 0.0 19.0

22 Anion Exchange (90 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 19.0

23 POE Activated Alumina and corrosion control and pre-oxidation 0.0 0.0 0.0

24 POU Reverse Osmosis and pre-oxidation 0.0 0.0 0.0

25 POU Activated Alumina and pre-oxidation 0.0 0.0 0.0

Sum of Probabilities: 100.00 100.00 100.00

Percent of Treatment Required to 

Achieve MCL

Exhibit A-8

Probability Compliance Decision Tree: Ground Water Systems Serving 50,001-100,000 People 
No. Treatment Technology Train <50% 50-90% >90%

 1 Regionalization 0.0 0.0 0.0

 2 Alternate Source 0.0 0.0 0.0

 3 Modify Lime Softening and pre-oxidation 10.0 10.0 5.0

 4 Modify Coagulation/Filtration and pre-oxidation 5.0 5.0 2.0

 5 Anion Exchange (25 mg/l SO4) and POTW w aste disposal and corrosion control and pre-oxidation 0.0 0.0 17.0

 6 Anion Exchange (150 mg/l SO4) and POTW w aste disposal and corrosion control and pre-oxidation 0.0 0.0 10.0

 7 Anion Exchange (25 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

 8 Anion Exchange (150 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

 9 Activated Alumina (2,000 BV) and non-hazardous landfill (for spent media) and pre-oxidation 0.0 0.0 0.0

10 Activated Alumina (10,000 BV) and non-hazardous landfill (for spent media) and pre-oxidation 0.0 0.0 0.0

11 Reverse Osmosis and direct discharge w aste disposal and corrosion control and pre-oxidation 0.0 0.0 0.0

12 Reverse Osmosis and POTW w aste disposal and corrosion control and pre-oxidation 0.0 0.0 0.0

13 Reverse Osmosis and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

14 Coagulation Assisted Microfiltration and mechanical de-w atering/non-hazardous landfill w aste disposal and pre-oxidation 43.0 43.0 0.0

15 Coagulation Assisted Microfiltration and non-mechanical de-w atering/non-hazardous landfill w aste disposal and pre-oxidation 42.0 42.0 0.0

16 Oxidation Filtration (Greensand) and POTW for backw ash stream 0.0 0.0 0.0

17 Anion Exchange (25 mg/l SO4) and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 17.0

18 Anion Exchange (150 mg/l SO4) and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 11.0

19 Activated Alumina (2,000 BV) and POTW/non-hazardous landfill and pre-oxidation 0.0 0.0 0.0

20 Activated Alumina (10,000 BV) and POTW/non-hazardous landfill and pre-oxidation 0.0 0.0 0.0

21 Anion Exchange (90 mg/l SO4) and POTW w aste disposal and corrosion control and pre-oxidation 0.0 0.0 19.0

22 Anion Exchange (90 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 19.0

23 POE Activated Alumina and corrosion control and pre-oxidation 0.0 0.0 0.0

24 POU Reverse Osmosis and pre-oxidation 0.0 0.0 0.0

25 POU Activated Alumina and pre-oxidation 0.0 0.0 0.0

Sum of Probabilities: 100.00 100.00 100.00

Percent of Treatment Required to 

Achieve MCL

Exhibit A-9

Probability Compliance Decision Tree: Ground Water Systems Serving 100,001-1,000,000 People 
No. Treatment Technology Train <50% 50-90% >90%

 1 Regionalization 0.0 0.0 0.0

 2 Alternate Source 0.0 0.0 0.0

 3 Modify Lime Softening and pre-oxidation 4.0 4.0 2.0

 4 Modify Coagulation/Filtration and pre-oxidation 22.0 22.0 11.0

 5 Anion Exchange (25 mg/l SO4) and POTW w aste disposal and corrosion control and pre-oxidation 2.0 2.0 17.0

 6 Anion Exchange (150 mg/l SO4) and POTW w aste disposal and corrosion control and pre-oxidation 0.0 0.0 0.0

 7 Anion Exchange (25 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 2.0 2.0 17.0

 8 Anion Exchange (150 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

 9 Activated Alumina (2,000 BV) and non-hazardous landfill (for spent media) and pre-oxidation 56.0 46.0 0.0

10 Activated Alumina (10,000 BV) and non-hazardous landfill (for spent media) and pre-oxidation 0.0 0.0 0.0

11 Reverse Osmosis and direct discharge w aste disposal and corrosion control and pre-oxidation 0.0 0.0 0.0

12 Reverse Osmosis and POTW w aste disposal and corrosion control and pre-oxidation 0.0 0.0 0.0

13 Reverse Osmosis and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

14 Coagulation Assisted Microfiltration and mechanical de-w atering/non-hazardous landfill w aste disposal and pre-oxidation 0.0 0.0 0.0

15 Coagulation Assisted Microfiltration and non-mechanical de-w atering/non-hazardous landfill w aste disposal and pre-oxidation 0.0 0.0 0.0

16 Oxidation Filtration (Greensand) and POTW for backw ash stream 0.0 0.0 0.0

17 Anion Exchange (25 mg/l SO4) and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

18 Anion Exchange (150 mg/l SO4) and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

19 Activated Alumina (2,000 BV) and POTW/non-hazardous landfill and pre-oxidation 0.0 0.0 0.0

20 Activated Alumina (10,000 BV) and POTW/non-hazardous landfill and pre-oxidation 0.0 0.0 0.0

21 Anion Exchange (90 mg/l SO4) and POTW w aste disposal and corrosion control and pre-oxidation 0.0 0.0 3.0

22 Anion Exchange (90 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 3.0

23 POE Activated Alumina and corrosion control and pre-oxidation 5.0 8.0 15.0

24 POU Reverse Osmosis and pre-oxidation 5.0 8.0 16.0

25 POU Activated Alumina and pre-oxidation 4.0 8.0 16.0

Sum of Probabilities: 100.00 100.00 100.00

Percent of Treatment Required to 

Achieve MCL

Exhibit A-10

Probability Decision Tree: Surface Water Systems Serving 100 People 
No. Treatment Technology Train <50% 50-90% >90%

 1 Regionalization 0.0 0.0 0.0

 2 Alternate Source 0.0 0.0 0.0

 3 Modify Lime Softening and pre-oxidation 9.0 9.0 4.0

 4 Modify Coagulation/Filtration and pre-oxidation 53.0 53.0 26.0

 5 Anion Exchange (25 mg/l SO4) and POTW w aste disposal and corrosion control and pre-oxidation 15.0 17.0 16.0

 6 Anion Exchange (150 mg/l SO4) and POTW w aste disposal and corrosion control and pre-oxidation 0.0 0.0 0.0

 7 Anion Exchange (25 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 14.0 17.0 16.0

 8 Anion Exchange (150 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

 9 Activated Alumina (2,000 BV) and non-hazardous landfill (for spent media) and pre-oxidation 0.0 0.0 0.0

10 Activated Alumina (10,000 BV) and non-hazardous landfill (for spent media) and pre-oxidation 0.0 0.0 0.0

11 Reverse Osmosis and direct discharge w aste disposal and corrosion control and pre-oxidation 0.0 0.0 0.0

12 Reverse Osmosis and POTW w aste disposal and corrosion control and pre-oxidation 0.0 0.0 0.0

13 Reverse Osmosis and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

14 Coagulation Assisted Microfiltration and mechanical de-w atering/non-hazardous landfill w aste disposal and pre-oxidation 0.0 0.0 0.0

15 Coagulation Assisted Microfiltration and non-mechanical de-w atering/non-hazardous landfill w aste disposal and pre-oxidation 0.0 0.0 0.0

16 Oxidation Filtration (Greensand) and POTW for backw ash stream 0.0 0.0 0.0

17 Anion Exchange (25 mg/l SO4) and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

18 Anion Exchange (150 mg/l SO4) and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

19 Activated Alumina (2,000 BV) and POTW/non-hazardous landfill and pre-oxidation 0.0 0.0 0.0

20 Activated Alumina (10,000 BV) and POTW/non-hazardous landfill and pre-oxidation 0.0 0.0 0.0

21 Anion Exchange (90 mg/l SO4) and POTW w aste disposal and corrosion control and pre-oxidation 0.0 2.0 19.0

22 Anion Exchange (90 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 0.0 2.0 19.0

23 POE Activated Alumina and corrosion control and pre-oxidation 3.0 0.0 0.0

24 POU Reverse Osmosis and pre-oxidation 3.0 0.0 0.0

25 POU Activated Alumina and pre-oxidation 3.0 0.0 0.0

Sum of Probabilities: 100.00 100.00 100.00

Percent of Treatment Required to 

Achieve MCL

Exhibit A-11

Probability Decision Tree: Surface Water Systems Serving 101-500 People 
No. Treatment Technology Train <50% 50-90% >90%

 1 Regionalization 0.0 0.0 0.0

 2 Alternate Source 0.0 0.0 0.0

 3 Modify Lime Softening and pre-oxidation 19.0 19.0 8.0

 4 Modify Coagulation/Filtration and pre-oxidation 73.0 73.0 36.0

 5 Anion Exchange (25 mg/l SO4) and POTW w aste disposal and corrosion control and pre-oxidation 8.0 8.0 16.0

 6 Anion Exchange (150 mg/l SO4) and POTW w aste disposal and corrosion control and pre-oxidation 0.0 0.0 0.0

 7 Anion Exchange (25 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

 8 Anion Exchange (150 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

 9 Activated Alumina (2,000 BV) and non-hazardous landfill (for spent media) and pre-oxidation 0.0 0.0 0.0

10 Activated Alumina (10,000 BV) and non-hazardous landfill (for spent media) and pre-oxidation 0.0 0.0 0.0

11 Reverse Osmosis and direct discharge w aste disposal and corrosion control and pre-oxidation 0.0 0.0 0.0

12 Reverse Osmosis and POTW w aste disposal and corrosion control and pre-oxidation 0.0 0.0 0.0

13 Reverse Osmosis and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

14 Coagulation Assisted Microfiltration and mechanical de-w atering/non-hazardous landfill w aste disposal and pre-oxidation 0.0 0.0 0.0

15 Coagulation Assisted Microfiltration and non-mechanical de-w atering/non-hazardous landfill w aste disposal and pre-oxidation 0.0 0.0 0.0

16 Oxidation Filtration (Greensand) and POTW for backw ash stream 0.0 0.0 0.0

17 Anion Exchange (25 mg/l SO4) and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 16.0

18 Anion Exchange (150 mg/l SO4) and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

19 Activated Alumina (2,000 BV) and POTW/non-hazardous landfill and pre-oxidation 0.0 0.0 0.0

20 Activated Alumina (10,000 BV) and POTW/non-hazardous landfill and pre-oxidation 0.0 0.0 0.0

21 Anion Exchange (90 mg/l SO4) and POTW w aste disposal and corrosion control and pre-oxidation 0.0 0.0 12.0

22 Anion Exchange (90 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 12.0

23 POE Activated Alumina and corrosion control and pre-oxidation 0.0 0.0 0.0

24 POU Reverse Osmosis and pre-oxidation 0.0 0.0 0.0

25 POU Activated Alumina and pre-oxidation 0.0 0.0 0.0

Sum of Probabilities: 100.00 100.00 100.00

Percent of Treatment Required to 

Achieve MCL

Exhibit A-12

Probability Decision Tree: Surface Water Systems Serving 501-1,000 People 
No. Treatment Technology Train <50% 50-90% >90%

 1 Regionalization 0.0 0.0 0.0

 2 Alternate Source 0.0 0.0 0.0

 3 Modify Lime Softening and pre-oxidation 16.0 16.0 8.0

 4 Modify Coagulation/Filtration and pre-oxidation 76.0 76.0 35.0

 5 Anion Exchange (25 mg/l SO4) and POTW w aste disposal and corrosion control and pre-oxidation 8.0 8.0 16.0

 6 Anion Exchange (150 mg/l SO4) and POTW w aste disposal and corrosion control and pre-oxidation 0.0 0.0 0.0

 7 Anion Exchange (25 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

 8 Anion Exchange (150 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

 9 Activated Alumina (2,000 BV) and non-hazardous landfill (for spent media) and pre-oxidation 0.0 0.0 0.0

10 Activated Alumina (10,000 BV) and non-hazardous landfill (for spent media) and pre-oxidation 0.0 0.0 0.0

11 Reverse Osmosis and direct discharge w aste disposal and corrosion control and pre-oxidation 0.0 0.0 0.0

12 Reverse Osmosis and POTW w aste disposal and corrosion control and pre-oxidation 0.0 0.0 0.0

13 Reverse Osmosis and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

14 Coagulation Assisted Microfiltration and mechanical de-w atering/non-hazardous landfill w aste disposal and pre-oxidation 0.0 0.0 0.0

15 Coagulation Assisted Microfiltration and non-mechanical de-w atering/non-hazardous landfill w aste disposal and pre-oxidation 0.0 0.0 0.0

16 Oxidation Filtration (Greensand) and POTW for backw ash stream 0.0 0.0 0.0

17 Anion Exchange (25 mg/l SO4) and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 16.0

18 Anion Exchange (150 mg/l SO4) and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

19 Activated Alumina (2,000 BV) and POTW/non-hazardous landfill and pre-oxidation 0.0 0.0 0.0

20 Activated Alumina (10,000 BV) and POTW/non-hazardous landfill and pre-oxidation 0.0 0.0 0.0

21 Anion Exchange (90 mg/l SO4) and POTW w aste disposal and corrosion control and pre-oxidation 0.0 0.0 13.0

22 Anion Exchange (90 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 12.0

23 POE Activated Alumina and corrosion control and pre-oxidation 0.0 0.0 0.0

24 POU Reverse Osmosis and pre-oxidation 0.0 0.0 0.0

25 POU Activated Alumina and pre-oxidation 0.0 0.0 0.0

Sum of Probabilities: 100.00 100.00 100.00

Percent of Treatment Required to 

Achieve MCL

Exhibit A-13

Probability Decision Tree: Surface Water Systems Serving 1,001-3,300 People 
No. Treatment Technology Train <50% 50-90% >90%

 1 Regionalization 0.0 0.0 0.0

 2 Alternate Source 0.0 0.0 0.0

 3 Modify Lime Softening and pre-oxidation 7.0 7.0 3.0

 4 Modify Coagulation/Filtration and pre-oxidation 85.0 85.0 42.0

 5 Anion Exchange (25 mg/l SO4) and POTW w aste disposal and corrosion control and pre-oxidation 8.0 8.0 16.0

 6 Anion Exchange (150 mg/l SO4) and POTW w aste disposal and corrosion control and pre-oxidation 0.0 0.0 0.0

 7 Anion Exchange (25 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

 8 Anion Exchange (150 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

 9 Activated Alumina (2,000 BV) and non-hazardous landfill (for spent media) and pre-oxidation 0.0 0.0 0.0

10 Activated Alumina (10,000 BV) and non-hazardous landfill (for spent media) and pre-oxidation 0.0 0.0 0.0

11 Reverse Osmosis and direct discharge w aste disposal and corrosion control and pre-oxidation 0.0 0.0 0.0

12 Reverse Osmosis and POTW w aste disposal and corrosion control and pre-oxidation 0.0 0.0 0.0

13 Reverse Osmosis and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

14 Coagulation Assisted Microfiltration and mechanical de-w atering/non-hazardous landfill w aste disposal and pre-oxidation 0.0 0.0 0.0

15 Coagulation Assisted Microfiltration and non-mechanical de-w atering/non-hazardous landfill w aste disposal and pre-oxidation 0.0 0.0 0.0

16 Oxidation Filtration (Greensand) and POTW for backw ash stream 0.0 0.0 0.0

17 Anion Exchange (25 mg/l SO4) and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 16.0

18 Anion Exchange (150 mg/l SO4) and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

19 Activated Alumina (2,000 BV) and POTW/non-hazardous landfill and pre-oxidation 0.0 0.0 0.0

20 Activated Alumina (10,000 BV) and POTW/non-hazardous landfill and pre-oxidation 0.0 0.0 0.0

21 Anion Exchange (90 mg/l SO4) and POTW w aste disposal and corrosion control and pre-oxidation 0.0 0.0 12.0

22 Anion Exchange (90 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 11.0

23 POE Activated Alumina and corrosion control and pre-oxidation 0.0 0.0 0.0

24 POU Reverse Osmosis and pre-oxidation 0.0 0.0 0.0

25 POU Activated Alumina and pre-oxidation 0.0 0.0 0.0

Sum of Probabilities: 100.00 100.00 100.00

Percent of Treatment Required to 

Achieve MCL

Exhibit A-14

Probability Decision Tree: Surface Water Systems Serving 3,301-10,000 People 
No. Treatment Technology Train <50% 50-90% >90%

 1 Regionalization 0.0 0.0 0.0

 2 Alternate Source 0.0 0.0 0.0

 3 Modify Lime Softening and pre-oxidation 8.0 8.0 4.0

 4 Modify Coagulation/Filtration and pre-oxidation 92.0 92.0 48.0

 5 Anion Exchange (25 mg/l SO4) and POTW w aste disposal and corrosion control and pre-oxidation 0.0 0.0 16.0

 6 Anion Exchange (150 mg/l SO4) and POTW w aste disposal and corrosion control and pre-oxidation 0.0 0.0 0.0

 7 Anion Exchange (25 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

 8 Anion Exchange (150 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

 9 Activated Alumina (2,000 BV) and non-hazardous landfill (for spent media) and pre-oxidation 0.0 0.0 0.0

10 Activated Alumina (10,000 BV) and non-hazardous landfill (for spent media) and pre-oxidation 0.0 0.0 0.0

11 Reverse Osmosis and direct discharge w aste disposal and corrosion control and pre-oxidation 0.0 0.0 0.0

12 Reverse Osmosis and POTW w aste disposal and corrosion control and pre-oxidation 0.0 0.0 0.0

13 Reverse Osmosis and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

14 Coagulation Assisted Microfiltration and mechanical de-w atering/non-hazardous landfill w aste disposal and pre-oxidation 0.0 0.0 0.0

15 Coagulation Assisted Microfiltration and non-mechanical de-w atering/non-hazardous landfill w aste disposal and pre-oxidation 0.0 0.0 0.0

16 Oxidation Filtration (Greensand) and POTW for backw ash stream 0.0 0.0 0.0

17 Anion Exchange (25 mg/l SO4) and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 16.0

18 Anion Exchange (150 mg/l SO4) and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

19 Activated Alumina (2,000 BV) and POTW/non-hazardous landfill and pre-oxidation 0.0 0.0 0.0

20 Activated Alumina (10,000 BV) and POTW/non-hazardous landfill and pre-oxidation 0.0 0.0 0.0

21 Anion Exchange (90 mg/l SO4) and POTW w aste disposal and corrosion control and pre-oxidation 0.0 0.0 8.0

22 Anion Exchange (90 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 8.0

23 POE Activated Alumina and corrosion control and pre-oxidation 0.0 0.0 0.0

24 POU Reverse Osmosis and pre-oxidation 0.0 0.0 0.0

25 POU Activated Alumina and pre-oxidation 0.0 0.0 0.0

Sum of Probabilities: 100.00 100.00 100.00

Percent of Treatment Required to 

Achieve MCL

Exhibit A-15

Probability Decision Tree: Surface Water Systems Serving 10,001-50,000 People 
No. Treatment Technology Train <50% 50-90% >90%

 1 Regionalization 0.0 0.0 0.0

 2 Alternate Source 0.0 0.0 0.0

 3 Modify Lime Softening and pre-oxidation 5.0 5.0 2.0

 4 Modify Coagulation/Filtration and pre-oxidation 85.0 85.0 42.0

 5 Anion Exchange (25 mg/l SO4) and POTW w aste disposal and corrosion control and pre-oxidation 0.0 0.0 16.0

 6 Anion Exchange (150 mg/l SO4) and POTW w aste disposal and corrosion control and pre-oxidation 0.0 0.0 0.0

 7 Anion Exchange (25 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

 8 Anion Exchange (150 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

 9 Activated Alumina (2,000 BV) and non-hazardous landfill (for spent media) and pre-oxidation 0.0 0.0 0.0

10 Activated Alumina (10,000 BV) and non-hazardous landfill (for spent media) and pre-oxidation 0.0 0.0 0.0

11 Reverse Osmosis and direct discharge w aste disposal and corrosion control and pre-oxidation 0.0 0.0 0.0

12 Reverse Osmosis and POTW w aste disposal and corrosion control and pre-oxidation 0.0 0.0 0.0

13 Reverse Osmosis and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

14 Coagulation Assisted Microfiltration and mechanical de-w atering/non-hazardous landfill w aste disposal and pre-oxidation 5.0 5.0 0.0

15 Coagulation Assisted Microfiltration and non-mechanical de-w atering/non-hazardous landfill w aste disposal and pre-oxidation 5.0 5.0 0.0

16 Oxidation Filtration (Greensand) and POTW for backw ash stream 0.0 0.0 0.0

17 Anion Exchange (25 mg/l SO4) and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 16.0

18 Anion Exchange (150 mg/l SO4) and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

19 Activated Alumina (2,000 BV) and POTW/non-hazardous landfill and pre-oxidation 0.0 0.0 0.0

20 Activated Alumina (10,000 BV) and POTW/non-hazardous landfill and pre-oxidation 0.0 0.0 0.0

21 Anion Exchange (90 mg/l SO4) and POTW w aste disposal and corrosion control and pre-oxidation 0.0 0.0 12.0

22 Anion Exchange (90 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 12.0

23 POE Activated Alumina and corrosion control and pre-oxidation 0.0 0.0 0.0

24 POU Reverse Osmosis and pre-oxidation 0.0 0.0 0.0

25 POU Activated Alumina and pre-oxidation 0.0 0.0 0.0

Sum of Probabilities: 100.00 100.00 100.00

Percent of Treatment Required to 

Achieve MCL

Exhibit A-16

Probability Decision Tree: Surface Water Systems Serving 50,001-100,000 People 
No. Treatment Technology Train <50% 50-90% >90%

 1 Regionalization 0.0 0.0 0.0

 2 Alternate Source 0.0 0.0 0.0

 3 Modify Lime Softening and pre-oxidation 5.0 5.0 2.0

 4 Modify Coagulation/Filtration and pre-oxidation 94.0 94.0 47.0

 5 Anion Exchange (25 mg/l SO4) and POTW w aste disposal and corrosion control and pre-oxidation 0.0 0.0 16.0

 6 Anion Exchange (150 mg/l SO4) and POTW w aste disposal and corrosion control and pre-oxidation 0.0 0.0 0.0

 7 Anion Exchange (25 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

 8 Anion Exchange (150 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

 9 Activated Alumina (2,000 BV) and non-hazardous landfill (for spent media) and pre-oxidation 0.0 0.0 0.0

10 Activated Alumina (10,000 BV) and non-hazardous landfill (for spent media) and pre-oxidation 0.0 0.0 0.0

11 Reverse Osmosis and direct discharge w aste disposal and corrosion control and pre-oxidation 0.0 0.0 0.0

12 Reverse Osmosis and POTW w aste disposal and corrosion control and pre-oxidation 0.0 0.0 0.0

13 Reverse Osmosis and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

14 Coagulation Assisted Microfiltration and mechanical de-w atering/non-hazardous landfill w aste disposal and pre-oxidation 1.0 1.0 0.0

15 Coagulation Assisted Microfiltration and non-mechanical de-w atering/non-hazardous landfill w aste disposal and pre-oxidation 0.0 0.0 0.0

16 Oxidation Filtration (Greensand) and POTW for backw ash stream 0.0 0.0 0.0

17 Anion Exchange (25 mg/l SO4) and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 16.0

18 Anion Exchange (150 mg/l SO4) and chemical precipitation/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 0.0

19 Activated Alumina (2,000 BV) and POTW/non-hazardous landfill and pre-oxidation 0.0 0.0 0.0

20 Activated Alumina (10,000 BV) and POTW/non-hazardous landfill and pre-oxidation 0.0 0.0 0.0

21 Anion Exchange (90 mg/l SO4) and POTW w aste disposal and corrosion control and pre-oxidation 0.0 0.0 10.0

22 Anion Exchange (90 mg/l SO4) and evaporation pond/non-hazardous landfill and corrosion control and pre-oxidation 0.0 0.0 9.0

23 POE Activated Alumina and corrosion control and pre-oxidation 0.0 0.0 0.0

24 POU Reverse Osmosis and pre-oxidation 0.0 0.0 0.0

25 POU Activated Alumina and pre-oxidation 0.0 0.0 0.0

Sum of Probabilities: 100.00 100.00 100.00

Percent of Treatment Required to 

Achieve MCL

Exhibit A-17

Probability Decision Tree: Surface Water Systems Serving 100,001-1,000,000 People 
Appendix B, Bladder Cancer Risk Analysis B-1 Proposed Arsenic in Drinking Water Rule RIA

Appendix B: Bladder Cancer Risk Analysis

B.1 Community Water Systems

In order to calculate the number of bladder cancer cases avoided due to each regulatory option,

EPA developed a Monte-Carlo based risk model. This model is summarized in Chapter 5. This

appendix provides a more detailed description of the risk analysis, including the assumptions and

calculations used in the analysis. 

The following sections explain how we calculated risk reductions for populations exposed to

arsenic concentrations of 3 Fg/L and above in CWSs. First, the data used in the analysis will be

presented. Second, the calculations used in the analysis will be explained. Finally, the results of

the analysis will be explained.

B.1.1 Data Inputs

The inputs into a Monte-Carlo analysis can be separated into two categories, those data that

describe variation across a population, and those data that describe uncertainty in the underlying

population values. In the CWS risk analysis, two data inputs have elements of uncertainty, water

consumption and the risk distributions (lifetime risk at 50 Fg/L, assuming consumption of 2 L per

day, and 70 kg body weight). In order to best understand the results of the analysis, it is

important to separate out the effects of variation and uncertainty. 

This is accomplished in the following manner. Two different distributions for water consumption

are used. As described in the next section, one includes “total water consumption” and one

includes “community water consumption.” The former captures the upper bound of water

consumption, and the latter captures the lower bound. Likewise, two different distributions for

lifetime risk are used. As described below, the first captures the lower bound of lifetime risk

(mean 0.731/1,000 people, 95% upper confidence limit 0.807/1,000 people) and the second

captures the upper bound of lifetime risk (mean 1.237/1,000 people, 95% upper confidence limit

1.548/1,000 people). Therefore, throughout the analysis, two scenarios are carried out. The

“Lower Bound” scenario uses the lower bound water consumption and lifetime risk assumptions. 

The “Upper Bound” scenario uses upper bound water consumption and lifetime risk assumptions. 

The range of results within one scenario represent the variation within the population. The

difference in results between the two scenarios captures the uncertainty in the risk analysis. 

B.1.1.1 Water Consumption

EPA recently updated its estimates of personal (per capita) daily average estimates of water

consumption (Estimated per Capita Water Consumption in the United States, external review

draft, EPA 1999). The estimates used data from the combined 1994, 1995, and 1996 Continuing

Survey of Food Intakes by Individuals (CSFII), conducted by the U.S. Department of Agriculture
Appendix B, Bladder Cancer Risk Analysis B-2 Proposed Arsenic in Drinking Water Rule RIA

1.00 321.00 641.00 961.00 1,281.00

Consumption Male <1 LB

Exhibit B-2

Water Consumption (ml) Male Less Than 1 Year Old (Lower Bound)

(USDA). The CSFII is a complex, multistage area probability sample of the entire U.S. and is

conducted to survey the food and beverage intake of the U.S. Estimates of water consumed

include “Community Water” and “Total Water.” Community Water includes water consumed

directly as a beverage as well as water added to foods and beverages during final preparation at

home or by food service establishments such as school cafeterias and restaurants. “Total”

includes Community Water plus bottled water (see Exhibit B-1).

Exhibit B-1

 Source of Water Consumed

Source Direct 

(drinking)

Indirect

 (from food and beverages)

Bottled water

Community

Water

X X

Total 

Water

X X X

Water consumption estimates for selected subpopulations in the U.S. are described in the analysis,

including per capita water consumption by source for gender, region, age categories, economic

status, race, and residential status and separately for pregnant women, lactating women, and

women in childbearing years. The water consumption estimates by age and sex were used in the

computation of bladder cancer cases avoided, and are shown in Exhibits B-2 through B-21.
Appendix B, Bladder Cancer Risk Analysis B-3 Proposed Arsenic in Drinking Water Rule RIA

7.00 1,001.25 1,995.50 2,989.75 3,984.00

Consumption Male 11-19 LB

Exhibit B-4

Water Consumption (ml) Male 11-19 Years Old (Lower Bound)

4.00 435.75 867.50 1,299.25 1,731.00

Consumption Male 1-10 LB

Exhibit B-3

Water Consumption (ml) Male 1-10 Years Old (Lower Bound)
Appendix B, Bladder Cancer Risk Analysis B-4 Proposed Arsenic in Drinking Water Rule RIA

12.00 1,302.00 2,592.00 3,882.00 5,172.00

Consumption Male 20-64 LB

Exhibit B-5

Water Consumption (ml) Male 20-64 Years Old (Lower Bound)

30.00 919.50 1,809.00 2,698.50 3,588.00

Consumption Male 65+ LB

Exhibit B-6

Water Consumption (ml) Male Over 64 Years Old (Lower Bound)
Appendix B, Bladder Cancer Risk Analysis B-5 Proposed Arsenic in Drinking Water Rule RIA

7.00 397.00 787.00 1,177.00 1,567.00

Consumption Male <1 UB

Exhibit B-7

Water Consumption (ml) Male Under 1 Year Old (Upper Bound)

14.00 464.75 915.50 1,366.25 1,817.00

Consumption Male 1-10 UB

Exhibit B-8

Water Consumption (ml) Male 1-10 Years Old (Upper Bound)
Appendix B, Bladder Cancer Risk Analysis B-6 Proposed Arsenic in Drinking Water Rule RIA

28.00 1,023.75 2,019.50 3,015.25 4,011.00

Consumption Male 11-19 UB

Exhibit B-9

Water Consumption (ml) Male 11-19 Years Old (Upper Bound)

224.00 1,117.50 2,011.00 2,904.50 3,798.00

Consumption Male 65+ UB

Exhibit B-11

Water Consumption (ml) Male Over 64 Years Old (Upper Bound)

65.00 1,451.00 2,837.00 4,223.00 5,609.00

Consumption Male 20-64 UB

Exhibit B-10

Water Consumption (ml) Male 20-64 Years Old (Upper Bound)
Appendix B, Bladder Cancer Risk Analysis B-7 Proposed Arsenic in Drinking Water Rule RIA

10.00 403.50 797.00 1,190.50 1,584.00

Consumption Female <1 LB

Exhibit B-12

Water Consumption (ml) Female Under 1 Year Old (Lower Bound)
Appendix B, Bladder Cancer Risk Analysis B-8 Proposed Arsenic in Drinking Water Rule RIA

6.00 508.00 1,010.00 1,512.00 2,014.00

Consumption Female 1-10 LB

Exhibit B-13

Water Consumption (ml) Female 1-10 Years Old (Lower Bound)

7.00 654.75 1,302.50 1,950.25 2,598.00

Consumption Female 11-19 LB

Exhibit B-14

Water Consumption (ml) Female 11-19 Years Old (Lower Bound)
Appendix B, Bladder Cancer Risk Analysis B-9 Proposed Arsenic in Drinking Water Rule RIA

11.00 1,091.00 2,171.00 3,251.00 4,331.00

Consumption Female 20-64 LB

Exhibit B-15

Water Consumption (ml) Female 20-64 Years Old (Lower Bound)

16.00 936.25 1,856.50 2,776.75 3,697.00

Consumption Female 65+ LB

Exhibit B-16

Water Consumption (ml) Female Over 64 Years Old (Lower Bound)
Appendix B, Bladder Cancer Risk Analysis B-10 Proposed Arsenic in Drinking Water Rule RIA

19.00 523.00 1,027.00 1,531.00 2,035.00

Consumption Female 1-10 UB

Exhibit B-18

Water Consumption (ml) Female 1-10 Years Old (Upper Bound)

24.00 431.50 839.00 1,246.50 1,654.00

Consumption Female <1 UB

Exhibit B-17

Water Consumption (ml) Female Under 1 Year Old (Upper Bound)
Appendix B, Bladder Cancer Risk Analysis B-11 Proposed Arsenic in Drinking Water Rule RIA

23.00 788.00 1,553.00 2,318.00 3,083.00

Consumption Female 11-19 UB

Exhibit B-19

Water Consumption (ml) Female 11-19 Years Old (Upper Bound)
Appendix B, Bladder Cancer Risk Analysis B-12 Proposed Arsenic in Drinking Water Rule RIA

89.00 1,257.75 2,426.50 3,595.25 4,764.00

Consumption Female 20-64 UB

Exhibit B-20

Water Consumption (ml) Female 20-64 Years Old (Upper Bound)
Appendix B, Bladder Cancer Risk Analysis B-13 Proposed Arsenic in Drinking Water Rule RIA

316.00 1,161.75 2,007.50 2,853.25 3,699.00

Consumption Female 65+ UB

Exhibit B-21

Water Consumption (ml) Female Over 64 Years Old (Upper Bound)

B.1.1.2 Body Weight

In this analysis, EPA used body weight data from the U.S. census (DOC, 1999). The body weight

data included a mean and a distribution of weight for male and females on a year-to-year basis

throughout a lifetime (70 years). These data were used to develop statistical distributions of body

weight for each sex and age category included in the water consumption study discussed above. 

The body weight distributions are provided in Exhibits B-22 through B-31.
Appendix B, Bladder Cancer Risk Analysis B-14 Proposed Arsenic in Drinking Water Rule RIA

 Normal distribution with parameters:

Mean 9.4

Standard Dev. 1.3

5.50 7.45 9.40 11.35 13.30

male wt<1

Exhibit B-22

Body Weight (kg) Male Less Than 1 Year Old

 Normal distribution with parameters:

Mean 22.1

Standard Dev. 1.4

17.90 20.00 22.10 24.20 26.30

1 to 10

Exhibit B-23

Body Weight (kg) Male 1-10 Years Old
Appendix B, Bladder Cancer Risk Analysis B-15 Proposed Arsenic in Drinking Water Rule RIA

 Normal distribution with parameters:

Mean 58.5

Standard Dev. 3.8

47.10 52.80 58.50 64.20 69.90

11 to 19

Exhibit B-24

Body Weight (kg) Male 11-19 Years Old

 Normal distribution with parameters:

Mean 79.1

Standard Dev. 6.3

60.20 69.65 79.10 88.55 98.00

20 to 64

Exhibit B-25

Body Weight (kg) Male 20-64 Years Old
Appendix B, Bladder Cancer Risk Analysis B-16 Proposed Arsenic in Drinking Water Rule RIA

 Normal distribution with parameters:

Mean 74.8

Standard Dev. 12.8

36.40 55.60 74.80 94.00 113.20

65 & over

Exhibit B-26

Body Weight (kg) Male Over 64 Years Old

 Normal distribution with parameters:

Mean 8.8

Standard Dev. 1.2

5.20 7.00 8.80 10.60 12.40

<1

Exhibit B-27

Body Weight (kg) Female Under 1 Year Old
Appendix B, Bladder Cancer Risk Analysis B-17 Proposed Arsenic in Drinking Water Rule RIA

 Normal distribution with parameters:

Mean 21.6

Standard Dev. 1.5

17.10 19.35 21.60 23.85 26.10

1 to 10

Exhibit B-28

Body Weight (kg) Female 1-10 Years Old

 Normal distribution with parameters:

Mean 53.8

Standard Dev. 3.6

43.00 48.40 53.80 59.20 64.60

11 to 19

Exhibit B-29

Body Weight (kg) Female 11-19 Years Old
Appendix B, Bladder Cancer Risk Analysis B-18 Proposed Arsenic in Drinking Water Rule RIA

 Normal distribution with parameters:

Mean 65.8

Standard Dev. 7

44.80 55.30 65.80 76.30 86.80

20 to 64

Exhibit B-30

Body Weight (kg) Female 20-64 Years Old

 Normal distribution with parameters:

Mean 66.6

Standard Dev. 13.8

25.20 45.90 66.60 87.30 108.00

65 & over

Exhibit B-31

Body Weight (kg) Female Over 64 Years Old
1

 We do not have data on the rates of survival for bladder cancer in the Taiwanese villages in the study

and at the time of data collection. We do know that the relative survival rates for bladder cancer in developing

countries overall ranged from 23.5% to 66.1 % in 1982-1992 (“Cancer Survival in Developing Countries,”

International Agency for Research on Cancer, World Health Organization, Publication No. 145, 1998). The ageadjusted annual incidence rates of bladder cancer in Taiwan in 1996 for males and females, respectively, were 7.36

and 3.09 per 100,000, with corresponding annual mortality rates of 3.21 and 1.44 per 100,000 (correspondence

from Chen to Herman Gibb, January 3, 2000). 

Appendix B, Bladder Cancer Risk Analysis B-19 Proposed Arsenic in Drinking Water Rule RIA

B.1.1.3 Lifetime Risk of Bladder Cancer

In its 1999 report, Arsenic in Drinking Water, the National Research Council (NRC) analyzed

bladder cancer risks using data from Taiwan. In addition, NRC examined evidence from human

epidemiological studies in Chile and Argentina, and concluded that risks of bladder and lung

cancer were comparable to those “in Taiwan at comparable levels of exposure (NRC 1999, page

7).” The NRC also examined the implications of applying different mathematical procedures to

the newly available Taiwanese data for the purpose of characterizing bladder cancer risk.

These risk distributions are based on bladder cancer mortality data in Taiwan, in a section of

Taiwan where arsenic concentrations in the water are very high by comparison to those in the

U.S. It is also an area of very low incomes and poor diets, and the availability and quality of

medical care is not of high quality, by U.S. standards. In its estimate of bladder cancer risk, the

Agency assumed, that within the Taiwanese study area, the risk of contracting bladder cancer was

relatively close to the risk of dying from bladder cancer (that is, that the bladder cancer morbidity

rate was equal to the bladder cancer mortality rate).1

In the NRC report, two tables are provided which provide six lifetime risk distributions at the

current MCL of 50 ug/L, which EPA’s senior scientist feel are appropriate to use in this risk

analysis. Table 10-11 of the report shows three risk estimates based on the Taiwanese male

bladder cancer data, using a Poisson regression model (the models differ based on assumptions

regarding the availability of baseline data about the exposed population). The means of the risk

distributions are 0.731, 0.911, and 1.049 per 1,000 people. Table 10-12 of the report presents

excess lifetime risk estimates at the current MCL of 50 ug/L for bladder cancer in males

calculated using EPA’s 1996 proposed revisions to the cancer guidelines (EPA 1996) (the

models differ based on assumptions regarding the availability of baseline data about the exposed

population). The means of these distributions are: 1.237, 1.129, and 1.111 cases per 1,000

people.

EPA has no means by which to choose one of these lifetime risk estimates over the other,

therefore, as mentioned above, the Agency has chosen to estimate the range of uncertainty

concerning the lifetime risk estimates. This was done by using the lowest lifetime risk estimate in

the “Lower Bound” scenario, and using the highest lifetime risk estimate in the “Upper Bound”

scenario. These risk estimates are shown in Exhibits B-32 And B-33 respectively.
Appendix B, Bladder Cancer Risk Analysis B-20 Proposed Arsenic in Drinking Water Rule RIA

 Normal distribution with parameters:

Mean 0.731

Standard Dev. 0.0388

0.61 0.67 0.73 0.79 0.85

Lifetime Risk/1000 LB

Exhibit B-32

Lifetime Bladder Cancer Risk at 50 Fg/L per 1,000 people (Lower Bound)

 Normal distribution with parameters:

Mean 1.237

Standard Dev. 0.159

0.76 1.00 1.24 1.48 1.71

Lifetime Risk/1000 UB

Exhibit B-33

Lifetime Bladder Cancer Risk at 50 Fg/L per 1,000 People (Upper Bound)
Appendix B, Bladder Cancer Risk Analysis B-21 Proposed Arsenic in Drinking Water Rule RIA

3.00 14.75 26.50 38.25 50.00

GW Occurrence No Treatment

Exhibit B-34

Post-Compliance Exposure Distribution (Fg/L) at MCL= 50 Fg/L 

(Ground Water)

B.1.1.4 Arsenic Occurrence Estimates

EPA used statistical techniques to assess the national distribution of mean arsenic concentrations

in water systems. A detailed explanation of the occurrence data used in the risk analysis can be

found in the Occurrence and Exposure Document for the Arsenic in Drinking Water Rule (EPA,

1999). For each MCL under consideration, the Post-Compliance Exposure Distribution at

different concentrations (μg/L) is provided in Exhibits B-34 to B-38 for ground water and

Exhibits B-39 to B-43 for surface water. Two important caveats should be mentioned. First, the

risk analysis only applies to persons exposed to arsenic concentrations at or above 3 μg/L. This

represents the feasible range (at concentrations below this level, arsenic concentrations can not be

accurately measured). Second, for each MCL, it is assumed that all systems will provide finished

water with a maximum concentration equal to 80 percent of the MCL. This assumption is

consistent with industry practice, and the same assumption was made in the calculation of the

proposed rule’s costs.
Appendix B, Bladder Cancer Risk Analysis B-22 Proposed Arsenic in Drinking Water Rule RIA

3.00 4.75 6.50 8.25 10.00

GW Occurence MCL=10

Exhibit B-36

Post-Compliance Exposure Distribution (Fg/L) at MCL= 10 Fg/L

(Ground Water)

3.00 7.25 11.50 15.75 20.00

 GW Occurance MCL=20

Exhibit B-35

Post-Compliance Exposure Distribution (Fg/L) at MCL= 20 Fg/L

(Ground Water)
Appendix B, Bladder Cancer Risk Analysis B-23 Proposed Arsenic in Drinking Water Rule RIA

2.399 2.400 2.400 2.401 2.401

GW Occurence MCL=3

Exhibit B-38

Post-Compliance Exposure Distribution (Fg/L) at MCL= 3 Fg/L 

(Ground Water)

3.000 3.500 4.000 4.500 5.000

GW occurence MCL=5

Exhibit B-37

Post-Compliance Exposure Distribution (Fg/L) at MCL= 5 Fg/L 

(Ground Water)
Appendix B, Bladder Cancer Risk Analysis B-24 Proposed Arsenic in Drinking Water Rule RIA

3.00 7.25 11.50 15.75 20.00

SW Post treatment occ @ 20

Exhibit B-40

Post-Compliance Exposure Distribution (Fg/L) at MCL= 20 Fg/L

(Surface Water)

3.00 14.75 26.50 38.25 50.00

E37

Exhibit B-39

Post-Compliance Exposure Distribution (Fg/L) at MCL= 50 Fg/L

(Surface Water)
Appendix B, Bladder Cancer Risk Analysis B-25 Proposed Arsenic in Drinking Water Rule RIA

3.00 3.50 4.00 4.50 5.00

SW Post treatment occ @ 5(feasible)

Exhibit B-42

Post-Compliance Exposure Distribution (Fg/L) at MCL= 5 Fg/L

(Surface Water)

3.00 4.75 6.50 8.25 10.00

SW Post treatment occ @ 10(feasible)

Exhibit B-41

Post-Compliance Exposure Distribution (Fg/L) at MCL= 10 Fg/L

(Surface Water)
Appendix B, Bladder Cancer Risk Analysis B-26 Proposed Arsenic in Drinking Water Rule RIA

2.40 2.40 2.40 2.40 2.40

SW Post treatment occ @ 3

Exhibit B-43

Post-Compliance Exposure Distribution (Fg/L) at MCL= 3 Fg/L

(Surface Water)

B.1.1.5 CWS Population Affected

As mentioned above, the target population for the CWS risk analysis is people exposed to arsenic

at levels at or above 3 Fg/L, as this is considered the feasible level. Exhibit B-44 provides the

population served by both surface water and ground water CWSs. In addition, the percentage of

people served that are exposed at arsenic levels above 3 Fg/L is provided. Ground water systems

with finished water concentration above the minimum feasible level serve 16.5 million people,

while surface water systems with finished water above 3 Fg/L serve 10.1 million people, for a

total exposed population of 26.7 million people. Systems serving over1 million people were

identified from a system-by-system data collection.
Appendix B, Bladder Cancer Risk Analysis B-27 Proposed Arsenic in Drinking Water Rule RIA

Exhibit B-44

Total Population Served by Water Systems 

By Source Water, System Type and Service Population Category

Service

Population

Category

Community

Groundwater Surface Water

< 100 859,777 61,450

101–500 3,741,017 570,448

501–1,000 3,457,163 921,449

1,001–3,300 10,631,422 4,797,855

3,301–10,000 14,095,015 10,995,980

10,001–50,000 25,004,779 36,819,575

50,001–100,000 8,609,455 20,500,370

100,001-1,000,000 14,575,556 65,375,183

> 1,000,000 2,855,494 28,658,586

Total Population Served 83,829,678 168,700,896

Percentage of Population Over 3Fg/L 19.70% 6.01%

Population Served Over 3Fg/L By Source Type 16,514,447 10,138,923

Total Population Served Over 3Fg/L 26,653,370

SOURCE PERCENTAGE (Percentage of Total

Population Served Over 3Fg/L) 

62% 38%

Source: Safe Drinking Water Information System (SDWIS), December 1998 freeze.

In addition, since the daily water consumption and body weight associated with each age category

varies by sex, it is necessary to know the percentage of the population made up by each sex. In

this risk analysis, it is assumed that 51.9 percent of the population is female, and 48.1 percent is

male (DOC, 1999).

B.1.2 CWS Risk Model

The CWS risk analysis is a Monte-Carlo based simulation model. This section will explain each

step is the simulation. The Monte-Carlo simulation is conducted at each MCL option (50, 20, 10,

5 and 3 Fg/L). In addition, for each MCL option, the simulation is carried out for both the

“Lower Bound” and “Upper Bound” scenarios discussed above. Therefore, the simulation model

is carried out ten times. Each of these ten “runs” of the model is independent of the other, and can

be discussed in isolation. Therefore, this section will include a generalized discussion of the

model. The inputs that are used will depend on the MCL option and scenario being evaluated. It

is important not to confuse a “run” of the model” as just described, with a model iteration. Each
Appendix B, Bladder Cancer Risk Analysis B-28 Proposed Arsenic in Drinking Water Rule RIA

REF

C

mai W

mai

mai

=

























70

2

*

REF

C

fai W

fai

fai

=

























70

2

*

LREFmi REFmai Na

a

=









 ∑ *  / 70

LREFfi REFfai Na

a

=









 ∑ *  / 70

run of the model consists of 10,000 iterations. Within a single iteration, the model pulls a value

for each variable from its input distribution (e.g. body weight) and calculates a value for each

output variable (e.g. lifetime risk). This is done 10,000 times for each model run. The results of

the model run is the distribution of the 10,000 values for each output variable.

The first step of each iteration is to calculate the relative exposure factor for each sex and age

category. As shown in the following equation, the relative exposure factor is a function of daily

water consumption and body weight.

where;

REF = relative exposure factor

C = daily water consumption (L)

W = body weight (kg)

i = model iteration number

a = age category

m = male

f = female

Next, lifetime relative exposure factors are calculated for each sex using the relative exposure

factors and information regarding the number of years in each age catagory (e.g. a person spends

nine years in the 1-10 year old age category).

where;

LREF = lifetime relative exposure factor

N = number of years in age category

The model then determines, for this iteration, if the modeled individual is a male or a female. This
Appendix B, Bladder Cancer Risk Analysis B-29 Proposed Arsenic in Drinking Water Rule RIA

LREF

LREF if RN MP

LREF otherwise

i

mi

fi

=

 ≤





1

AS

AS if RN GP

AS otherwise

i

gi

si

=

 ≤





2

LR (RF LREF AS ) i i i i = * * / 50 *10

is done using a random number generator and information concerning the sex distribution of the

population.

where;

RN1 = random number from 0 to 1

MP = percentage of the population that is male (48.1%)

For each iteration, the model assumes that the individual is consuming water from either a surface

water system or a ground water system. If the individual is assumed to be associated with a

surface water system, then the arsenic concentration is chosen from the surface water

concentration distribution; likewise, if the person is assumed to be associated with a ground water

CWS, the arsenic concentration is chosen from the ground water concentration distribution.

where;

AS= concentration of arsenic (Fg/L)

RN2= random number from 0 to 1

GP= percentage of the population served by ground water (62%)

Finally, the lifetime risk of bladder cancer associated with this iteration is calculated.

where;

LR= lifetime risk of bladder cancer per 10,000 people

RF= lifetime risk of bladder cancer per 1,000 people, assuming

consumption of 2 liters per day, a body weight of 70 kg, and an

arsenic concentration of 50Fg/L.

In order to calculate the expected number of cancer cases associated with the model run, the

mean lifetime risk is multiplied by the exposed population, as follows:
Appendix B, Bladder Cancer Risk Analysis B-30 Proposed Arsenic in Drinking Water Rule RIA

CA

LR

N

P

i

i

=

































∑

*

10,000

where;

CA = expected number of bladder cancer cases

P = population

N = number of iterations

B.1.3 CWS Bladder Cancer Risk Estimates

Exhibits B-45 through B-54 provide the results of the CWS risk analysis. These exhibits provide

the mean and standard deviation of expected cases of bladder cancer per 10,000 people, as well as

the full distribution of expected risk values. The results for each MCL option are provided for

both the Lower and the Upper Bound Scenarios. 

As mentioned above, these results can be used to calculate the expected number of bladder

cancers nationwide by multiplying the mean expected risk associated with an MCL option by the

exposed population (in 10,000s). Likewise, the population exposed to a certain risk threshold

(e.g. 10-4), at a given an MCL, can be obtained by using the distribution of expected risk values.

These results are provided in Chapter 5 of this RIA.
Appendix B, Bladder Cancer Risk Analysis B-31 Proposed Arsenic in Drinking Water Rule RIA

S ta tis tics : V a lue

Mean 0.85

S tanda rd Dev ia tio n 1.06

Frequency Chart

 x10-4

.000

.014

.028

.042

.056

0

139

278

417

556

0.00 1.00 2.00 3.00 4.00

10,000 Trials 209 Outliers

Forecast: Ind. Lifetime Risk/10000 Untreated LB

Exhibit B-45

CWS Number of Cancer Cases per 10,000 people

Baseline Under Lower Bound Scenario 

S ta tis tics : V a lue

Mean 1.74

S tanda rd Dev ia tio n 1.97

Frequency Chart

 x10-4

.000

.013

.025

.038

.050

0

126

252

378

504

0.00 1.75 3.50 5.25 7.00

10,000 Trials 285 Outliers

Forecast: Ind. Lifetime Risk/10000 Untreated UB

Exhibit B-46

CWS Number of Cancer Cases per 10,000 people

Baseline Under Upper Bound Scenario 
Appendix B, Bladder Cancer Risk Analysis B-32 Proposed Arsenic in Drinking Water Rule RIA

S ta tis tics : V a lue

Mean 0.70

S tanda rd Dev ia tio n 0.59

Frequency Chart

 x10-4

.000

.009

.017

.026

.035

0

87.25

174.5

261.7

349

0.00 0.56 1.13 1.69 2.25

10,000 Trials 282 Outliers

Forecast: Ind. Lifetime Risk/10000 MCL=20 LB

Exhibit B-47

CWS Number of Cancer Cases per 10,000 people

MCL = 20 Fg/L Under Lower Bound Scenario

S ta tis tics : V a lue

Mean 1.47

S tanda rd Dev ia tio n 1.16

Frequency Chart

 x10-4

.000

.008

.017

.025

.034

0

84.75

169.5

254.2

339

0.00 1.13 2.25 3.38 4.50

10,000 Trials 285 Outliers

Forecast: Ind. Lifetime Risk/10000 MCL=20 UB

Exhibit B-48

CWS Number of Cancer Cases per 10,000 people

MCL = 20 Fg/L Under Upper Bound Scenario
Appendix B, Bladder Cancer Risk Analysis B-33 Proposed Arsenic in Drinking Water Rule RIA

S ta tis tics : V a lue

Mean 0.57

S tanda rd Dev ia tio n 0.37

Frequency Chart

 x10-4

.000

.008

.015

.023

.030

0

75.75

151.5

227.2

303

0.00 0.44 0.88 1.31 1.75

10,000 Trials 135 Outliers

Forecast: Ind. Lifetime Risk/10000 MCL=10 LB

Exhibit B-49

CWS Number of Cancer Cases per 10,000 people

MCL = 10 Fg/L Under Lower Bound Scenario

S ta tis tics : V a lue

Mean 1.19

S tanda rd Dev ia tio n 0.72

Frequency Chart

 x10-4

.000

.008

.016

.024

.031

0

78.5

157

235.5

314

0.00 0.88 1.75 2.63 3.50

10,000 Trials 128 Outliers

Forecast: Ind. Lifetime Risk/10000 MCL=10 UP

Exhibit B-50

CWS Number of Cancer Cases per 10,000 people

MCL = 10 Fg/L Under Upper Bound Scenario
Appendix B, Bladder Cancer Risk Analysis B-34 Proposed Arsenic in Drinking Water Rule RIA

S ta tis tics : V a lue

Mean 0.37

S tanda rd Dev ia tio n 0.20

Frequency Chart

.000

.007

.014

.021

.029

0

71.25

142.5

213.7

285

0.00 0.25 0.50 0.75 1.00

10,000 Trials 164 Outliers

Forecast: Ind. Lifetime Risk/10000 MCL=5 LB

Exhibit B-51

CWS Number of Cancer Cases per 10,000 people

MCL = 5 Fg/L Under Lower Bound Scenario

S ta tis tics : V a lue

Mean 0.78

S tanda rd Dev ia tio n 0.38

Frequency Chart

 x10-4

.000

.007

.014

.022

.029

0

72.25

144.5

216.7

289

0.00 0.50 1.00 1.50 2.00

10,000 Trials 121 Outliers

Forecast: Ind. Lifetime Risk/10000 MCL=5 UB

Exhibit B-52

CWS Number of Cancer Cases per 10,000 people

MCL = 5 Fg/L Under Upper Bound Scenario
Appendix B, Bladder Cancer Risk Analysis B-35 Proposed Arsenic in Drinking Water Rule RIA

S ta tis tics : V a lue

Mean 0.22

S tanda rd Dev ia tio n 0.12

Frequency Chart

 x10-4

.000

.006

.013

.019

.026

0

63.75

127.5

191.2

255

0.00 0.14 0.28 0.41 0.55

10,000 Trials 253 Outliers

Forecast: Ind. Lifetime Risk/10000 MCL=3 LB

Exhibit B-53

CWS Number of Cancer Cases per 10,000 people

MCL = 3 Fg/L Under Lower Bound Scenario

S ta tis tic s : V a lue

Mean 0.47

S tanda rd Dev ia tio n 0.22

Frequency Chart

.000

.007

.013

.020

.027

0

66.75

133.5

200.2

267

0.00 0.28 0.55 0.83 1.10

10,000 Trials 203 Outliers

Forecast: Ind. Lifetime Risk/10000 MCL=3 UB

Exhibit B-54

CWS Number of Cancer Cases per 10,000 people

MCL = 3 Fg/L Under Upper Bound Scenario
Appendix B, Bladder Cancer Risk Analysis B-36 Proposed Arsenic in Drinking Water Rule RIA

B.2 Non-Transient Non-Community Water Systems

B.2.1 Data Inputs

Most of the data described above under the CWS risk model is also used in the NTNC risk model. 

This includes water consumption, body weight, and lifetime risk estimates (at 50 Fg/L, 2 L

consumption, and 70 kg body weight). Also, the ground water arsenic concentrations at each

MCL used in the CWS risk model are used in the NTNC risk model. 

B.2.1.1 NTNC Service Categories, Population and Exposure Time

The main differences between the CWS and NTNC risk models are how population is distributed

among the different types of establishments that make up the NTNC category of systems, and the

extent to which the worker and customer populations within a service category are exposed to

arsenic (both in terms of length of exposure and drinking water consumed).

In addition to the CWS data already discussed, Exhibits B-55 and B-56 provide all of the data

inputs necessary to model the bladder cancer risk associated with NTNC systems. First, note that

in Exhibit B-55, the NTNC universe has been divided into 35 service categories. This was

accomplished using the system descriptions in SDWIS (EPA, 1999b). For each service category,

the total number of NTNCs and the population served by these NTNCs is taken from SDWIS. 

The population served by each NTNC often varies daily; the SDWIS population numbers are

interpreted to mean the peak population served (both workers and customers). 

The next data field in Exhibit B-55 is the number of customer cycles per year, or the number of

times each year the customer base turns over. For example, if this parameter equals one, then the

same customer’s are served each day. If the value is seven, then seven sets of customers use the

facility. The next field is the number of workers per person per day. For example, if the value is

0.1, as in the case of summer camps, then 10 percent of the peak population served (from

SDWIS) is assumed to be workers. Both the number of customer cycles per year assumptions

and workers per person per day data assumptions were made after investigating numerous data

sources, including trade-journals and trade association information. 

The next set of data fields in Exhibit B-55 are assumptions about the characteristics of the

workers in each service type. The percent of workers’ daily consumption is the percentage of

drinking water consumed on a work day that is consumed at work. This value is assumed to be

either 50 percent or 100 percent, depending on the service category. The number of days a person

works is assumed to be 250 for all service categories. The number of years a person works at the

NTNC establishment is assumed to be either 40 or 10, depending on the service category.

Information regarding customer behavior is provided in the next set of data fields in Exhibit B-55. 

The percent of customers’ daily consumption is the percentage of total drinking water consumed

on a day that the customer visits the NTNC, that is consumed at the NTNC. This value is

assumed to be either 25 percent, 50 percent or 100 percent, depending on the service category.
Appendix B, Bladder Cancer Risk Analysis B-37 Proposed Arsenic in Drinking Water Rule RIA

TCc = Pc CCc − WPc( * )*(1 )

TWc = Pc*WPc

PWLE

PWDC DW YW

c

c c c

=

* *

365*70

PCLE

PCDC DC YC

c

c c c

=

* *

365*70

The number of days a customer visits the NTNC is provided for each service category. For

example, the value for nursing homes of 365 indicates that nursing home customers are served by

the nursing home year round, while the value for churches of 52 indicates that churches are

assumed to serve their customers once per week. The number of years a person is assumed to

visits each service category is also provided.

Finally, the total exposed worker and customer populations for each service category are

provided in Exhibit B-55. These numbers are calculated as follows:

where:

TC= total number of customers

TW= total number of workers

P= SDWIS population

WP= workers per person per day

CC= number of customer cycles per year

c= NTNC service category

Exhibit B-56 provides the final set of data required to estimate bladder cancer risk from NTNCs. 

The percent of worker lifetime exposure is the percent of lifetime water consumption which is

consumed at the NTNC by a worker. The percent of customer lifetime exposure is the percent of

lifetime water consumption consumed at the NTNC by a customer. These numbers are calculated

as follows:

where;

PWLE =percent of worker lifetime exposure 

PCLE =percent of customer lifetime exposure 

PWDC =percentage of workers daily consumption

PCDC =percentage of customers daily consumption

DW =worker days per year

DC =customer days per year

YW =worker years

YC =customer years
Appendix B, Bladder Cancer Risk Analysis B-38 Proposed Arsenic in Drinking Water Rule RIA

Returning to Exhibit B-56, the worker age bracket is the age range (corresponding to the age

ranges used in the CWS risk analysis) that a NTNC worker is assumed to fall in. For all service

categories, the worker age bracket is assumed to be 20-64 years of age. The customer age

bracket is the age range (corresponding to the age ranges used in the CWS risk analysis) that a

NTNC customer is assumed to be in. For most service categories, the customer age bracket is

assumed to be 0-70 years of age (all ages). However, certain service categories only serve certain

age groups (e.g. nursing homes and schools), therefore more specific age ranges are assumed. 
Number 

of 

Systems

Total 

SDWIS 

Population

Number of 

Customer 

Cycles/Year

Worker 

Per 

Person 

Per Day

Percent of 

Worker's 

Daily 

Consumption

Worker 

Days Per 

Year

Worker 

Years

Percent of 

Customer's 

Daily 

Consumption

Customer 

Days Per 

Year

Customer 

Years

Total 

Worker 

Population

Total 

Customer 

Population

Water Wholesalers 266 66,018 1.00 0 n/a n/a n/a 25.0% 270.00 70.00 0 66,018

Mobile Home Parks 104 19,240 1.33 0.046 50.0% 250 40 100.0% 270.00 35.00 885 24,412

Nursing Homes 130 13,910 1.00 0.23 50.0% 250 40 100.0% 365.00 10.00 3,199 10,711

Churches 230 11,500 1.00 0.01 50.0% 250 40 50.0% 52.00 70.00 115 11,385

Golf and Country Clubs 116 11,716 4.50 0.11 50.0% 250 40 50.0% 52.00 70.00 1,289 46,923

Retailers (Food related) 142 45,724 2.00 0.07 50.0% 250 40 25.0% 185.00 70.00 3,201 85,047

Retailers (Non-food related) 695 120,930 4.50 0.09 50.0% 250 40 25.0% 52.00 70.00 10,884 495,208

Restaurants 418 154,660 2.00 0.07 50.0% 250 40 25.0% 185.00 70.00 10,826 287,668

Hotels/Motels 351 46,683 86.00 0.27 50.0% 250 40 100.0% 3.40 40.00 12,604 2,930,759

Prisons/Jails 67 121,940 1.33 0.1 50.0% 250 40 100.0% 270.00 3.00 12,194 145,962

Service Stations 53 12,190 7.00 0.06 50.0% 250 40 25.0% 52.00 54.00 731 80,210

Agricultural Products/Services 368 27,968 7.00 0.125 50.0% 250 40 25.0% 52.00 50.00 3,496 171,304

Daycare Centers 809 61,484 1.00 0.145 50.0% 250 10 50.0% 250.00 5.00 8,915 52,569

Schools 8,414 3,086,012 1.00 0.073 50.0% 200 40 50.0% 200.00 12.00 225,279 2,860,733

State Parks 83 106,895 26.00 0.016 50.0% 250 40 50.0% 14.00 70.00 1,710 2,734,802

Medical Facilities 367 163,631 16.40 0.022 50.0% 250 40 100.0% 6.70 10.30 3,600 2,624,510

Campgrounds/RV Parks 123 19,680 22.50 0.041 50.0% 180 40 100.0% 5.00 50.00 807 424,645

Federal Parks 20 780 26.00 0.016 50.0% 250 40 50.0% 14.00 70.00 12 19,956

Highway Rest Areas 15 6,105 50.70 0.01 50.0% 250 40 50.0% 7.20 70.00 61 306,428

Misc. Recreation Services 259 22,533 26.00 0.016 50.0% 250 40 100.0% 14.00 70.00 361 576,484

Forest Service 107 4,494 26.00 0.016 100.0% 250 40 100.0% 14.00 50.00 72 114,974

Interstate Carriers 287 35,301 93.00 0.304 50.0% 250 40 50.0% 2.00 70.00 10,732 2,284,963

Amusement Parks 159 76,462 90.00 0.18 50.0% 250 10 50.0% 1.00 70.00 13,763 5,642,896

Summer Camps 46 6,716 8.50 0.1 100.0% 180 10 100.0% 7.00 10.00 672 51,377

Airports 101 326,860 36.50 0.308 50.0% 250 40 25.0% 10.00 70.00 100,673 8,255,830

Military Bases 95 67,525 n/a 1 50.0% 250 40 n/a n/a n/a 67,525 0

Non-Water Utilities 497 84,490 n/a 1 50.0% 250 40 n/a n/a n/a 84,490 0

Office Parks 950 181,600 n/a 1 50.0% 250 40 n/a n/a n/a 181,600 0

Manufacturing: Food 768 285,696 n/a 1 50.0% 250 40 n/a n/a n/a 285,696 0

Manufacturing: Non-Food 3,356 588,792 n/a 1 50.0% 250 40 n/a n/a n/a 588,792 0

Landfills 78 3,432 n/a 1 100.0% 250 40 n/a n/a n/a 3,432 0

Fire Departments 41 4,018 n/a 1 100.0% 250 40 n/a n/a n/a 4,018 0

Construction 99 5,247 n/a 1 100.0% 250 40 n/a n/a n/a 5,247 0

Mining 119 13,447 n/a 1 100.0% 250 40 n/a n/a n/a 13,447 0

Migrant Labor Camps 33 2,079 n/a 1 100.0% 250 40 n/a n/a n/a 2,079 0

Subtotal = 1,662,407 30,305,774

TOTAL = 31,968,181

Exhibit B-55

NTNC Population and Exposure Time Data
Appendix B, Bladder Cancer Risk Analysis B-40 Proposed Arsenic in Drinking Water Rule RIA

Percent 

of Worker 

Lifetime 

Exposure

Percent of 

Customer 

Lifetime 

Exposure

Worker 

Age 

Bracket

Customer 

Age 

Bracket

Water Wholesalers 0.00% 18.49% n/a all

Mobile Home Parks 19.57% 36.99% 20 to 64 all

Nursing Homes 19.57% 14.29% 20 to 64 65+

Churches 19.57% 7.12% 20 to 64 all

Golf and Country Clubs 19.57% 7.12% 20 to 64 all

Retailers (Food related) 19.57% 12.67% 20 to 64 all

Retailers (Non-food related) 19.57% 3.56% 20 to 64 all

Restaurants 19.57% 12.67% 20 to 64 all

Hotels/Motels 19.57% 0.53% 20 to 64 all

Prisons/Jails 19.57% 3.17% 20 to 64 20 to 64

Service Stations 19.57% 2.75% 20 to 64 16 to 70

Agricultural Products/Services 19.57% 2.54% 20 to 64 all

Daycare Centers 4.89% 2.45% 20 to 64 <5

Schools 15.66% 4.70% 20 to 64 6 to 18

State Parks 19.57% 1.92% 20 to 64 all

Medical Facilities 19.57% 0.27% 20 to 64 all

Campgrounds/RV Parks 14.09% 0.98% 20 to 64 all

Federal Parks 19.57% 1.92% 20 to 64 all

Highway Rest Areas 19.57% 0.99% 20 to 64 all

Misc. Recreation Services 19.57% 3.84% 20 to 64 all

Forest Service 39.14% 2.74% 20 to 64 all

Interstate Carriers 19.57% 0.27% 20 to 64 all

Amusement Parks 4.89% 0.14% 20 to 64 all

Summer Camps 7.05% 0.27% 20 to 64 11 to 19

Airports 19.57% 0.68% 20 to 64 all

Military Bases 19.57% 0.00% 20 to 64 n/a

Non-Water Utilities 19.57% 0.00% 20 to 64 n/a

Office Parks 19.57% 0.00% 20 to 64 n/a

Manufacturing: Food 19.57% 0.00% 20 to 64 n/a

Manufacturing: Non-Food 19.57% 0.00% 20 to 64 n/a

Landfills 39.14% 0.00% 20 to 64 n/a

Fire Departments 39.14% 0.00% 20 to 64 n/a

Construction 39.14% 0.00% 20 to 64 n/a

Mining 39.14% 0.00% 20 to 64 n/a

Migrant Labor Camps 39.14% 0.00% all n/a

Exhibit B-56

NTNC Percent of Lifetime Exposure and Age at Exposure
Appendix B, Bladder Cancer Risk Analysis B-41 Proposed Arsenic in Drinking Water Rule RIA

REF

C

mai W

mai

mai

=

























70

2

*

REF

C

fai W

fai

fai

=

























70

2

*

B.2.2 The NTNC Risk Model

Just like the CWS risk analysis, the NTNC risk analysis is a Monte-Carlo based simulation model. 

This section will explain each step is the simulation. The Monte-Carlo simulation is conducted at

each MCL option (50, 20, 10, 5 and 3 Fg/L). In addition, for each MCL option, the simulation is

carried out for both the “Lower Bound” and “Upper Bound” scenarios just like in the CWS case. 

Therefore, the simulation model is carried out ten times. Each of these ten “runs” of the model is

independent of the other, and can be discussed in isolation. Therefore, this section will include a

generalized discussion of the model. The inputs that are used will depend on the MCL option and

scenario being evaluated at the time. It is important not to confuse a “run” of the model” as just

described, and a model iteration. Each run of the model consists of 10,000 iterations. Within a

single iteration, the model pulls a value for each variable from its input distribution (e.g. body

weight) and calculates a value for each output variable (e.g. lifetime risk). This is done for 10,000

times for each model run. The results of the model run is the distribution of the 10,000 values for

each output variable.

The first step of each iteration is to calculate the relative exposure factor for each sex and age

category. This is done exactly as it was done in the CWS risk analysis. As shown in the

following equations, the relative exposure factor is a function of daily water consumption and

body weight.

where;

REF = relative exposure factor

C = daily water consumption (L)

W = body weight (kg)

i = model iteration number

a = age category

m = male

f = female

Next, the lifetime risk of bladder cancer (1/100,000 people) is calculated for workers and

customers of each sex for each service category. The next four equations, therefore are:
Appendix B, Bladder Cancer Risk Analysis B-42 Proposed Arsenic in Drinking Water Rule RIA

WLR PWLE AS RF

REF Z

Z

fci ci gi i

fai ac

a

ac

a

=





















∑

∑

* *( / )*

( * )

50 *100

WLR PWLE AS RF

REF Z

Z

mci ci gi i

mai ac

a

ac

a

=





















∑

∑

* *( / )*

( * )

50 *100

CLR PCLE AS RF

REF Z

Z

mci ci gi i

mai ac

a

ac

a

=





















∑

∑

* *( / )*

( * )

50 *100

CLR PCLE AS RF

REF Z

Z

fci ci gi i

fai ac

a

ac

a

=





















∑

∑

* *( / )*

( * )

50 *100

WLR

WLR if RN MP

WLR otherwise ci

mci

fci

=

 ≤





1

CLR

CLR if RN MP

CLR otherwise ci

mci

fci

=

 ≤





1

where;

WLR = worker lifetime risk (per 100,000 people)

CLR = customer lifetime risk (per 100,000 people)

AS = arsenic concentration (Fg/L)

RF = risk of bladder cancer at 50 Fg/L, 2 liters consumption per day,

and 70 kg body weight

Z = years spent in age category

g = ground water

The sex of the worker and customer is then chosen for the iteration to determine the worker and

customer risk for each service category:
Appendix B, Bladder Cancer Risk Analysis B-43 Proposed Arsenic in Drinking Water Rule RIA

TC TCc

c

= ∑

TW TWc

c

= ∑

WPR

TW

TW TC c

c

=

( + )

CPR

TC

TW TC c

c

=

( + )

where;

RN1 = random number between 0 and 1

MP = percentage of the population that is male

Finally, the lifetime risk for the model iteration is determined by choosing among the 70

combinations of worker and customer risk over of the 35 service categories. This is accomplished

using a population weighted probability distribution. First, the total worker and customer

populations served are computed.

Next, the probability that the lifetime risk for the model iteration will be equal to the worker

lifetime risk associated with a service category is calculated:

where;

WPR =probability of choosing lifetime risk estimate for any iteration to

be equal to the lifetime risk estimate of a worker in a given

service category

Likewise, the probability that the lifetime risk for the model iteration will be equal to the customer

lifetime risk associated with a service category is calculated:

where;

CPR =probability of choosing lifetime risk estimate for any iteration to

be equal to the lifetime risk estimate of a customer in a given

service category
Appendix B, Bladder Cancer Risk Analysis B-44 Proposed Arsenic in Drinking Water Rule RIA

LR

WLR with obability WPR

CLR with obability CPR

i

ci c

ci c

=











Pr

Pr

M

CA

LR

N

i

i TC TW

N

=

























+ =

∑

1

100 000

*

( )

,

Given these probabilities, the lifetime risk estimate for each model iteration is chosen as follows:

where;

LR =Lifetime risk (1/100,000)

In order to calculate the expected number of cancer cases associated with the model run, the

mean lifetime risk is multiplied by the exposed population as follows: 

where;

CA = expected number of bladder cancer cases

N = number of iterations

B.2.3 NTNC Risk Results

Exhibits B-57 through B-66 provide the results of the NTNC risk analysis. These exhibits

provide the mean and standard deviation of expected cases of bladder cancer per 100,000 people,

as well as the full distribution of expected risk values. The results for each MCL option are

provided for both the Lower Bound Scenario and the Upper Bound Scenario. 

As mentioned above, these results can be used to calculate the expected number of bladder cancer

cases nationwide by multiplying the mean expected risk associated with an MCL option by the

exposed population (in 100,000s). Likewise, the population exposed to a certain risk threshold

(e.g. 10-4), at a given an MCL, can be obtained by using the distribution of expected risk values.

These results are provided in Chapter 5 of this RIA.
Appendix B, Bladder Cancer Risk Analysis B-45 Proposed Arsenic in Drinking Water Rule RIA

Statistics: Value

Mean 1.9E - 01

Standard Deviation 6.6E - 01

Frequency Chart

 x10-5

.000

.086

.171

.257

.342

0

855.2

3421

0.0E+0 5.0E-1 1.0E+0 1.5E+0 2.0E+0

10,000 Trials 151 Outliers

Forecast: Ind. Lifetime Composite Risk/100K NTNC

Exhibit B-57

NTNC Expected Number of Cancer Cases per 100,000 people

Baseline Under Lower Bound Scenario 

Statistics: Value

Mean 4.1E - 01

Standard Deviation 1.3E+00

Frequency Chart

.000

.080

.161

.241

.321

0

803.5

3214

0.0E+0 1.0E+0 2.0E+0 3.0E+0 4.0E+0

10,000 Trials 162 Outliers

Forecast: Ind. Lifetime Composite Risk/100K NTNC U

Exhibit B-58

NTNC Expected Number of Cancer Cases per 100,000 people

Baseline Under Upper Bound Scenario 
Appendix B, Bladder Cancer Risk Analysis B-46 Proposed Arsenic in Drinking Water Rule RIA

Statistics: V a lue

Mean 1.6E-01

Standard Deviation 4.4E-01

Frequency Chart

 x10-5

.000

.070

.141

.211

.281

0

703.2

2813

0.0E+0 3.8E-1 7.5E-1 1.1E+0 1.5E+0

10,000 Trials 174 Outliers

Forecast: Ind. Lifetime Composite Risk/100K NTNC

Exhibit B-59

NTNC Expected Number of Cancer Cases per 100,000 people

MCL = 20 Fg/L Under Lower Bound Scenario 

Statistics: Value

Mean 3.2E-01

Standard Deviation 8.4E-01

Frequency Chart

.000

.057

.115

.172

.230

0

574.5

2298

0.0E+0 6.9E-1 1.4E+0 2.1E+0 2.8E+0

10,000 Trials 199 Outliers

Forecast: Ind. Lifetime Composite Risk/100K NTNC U

Exhibit B-60

NTNC Expected Number of Cancer Cases per 100,000 people

MCL = 20 Fg/L Under Upper Bound Scenario 
Appendix B, Bladder Cancer Risk Analysis B-47 Proposed Arsenic in Drinking Water Rule RIA

Statistics: Value

Mean 1.2E - 01

Standard Deviation 3.3E - 01

Frequency Chart

 x10-5

.000

.052

.104

.155

.207

0

518.2

2073

0.0E+0 2.5E-1 5.0E-1 7.5E-1 1.0E+0

10,000 Trials 222 Outliers

Forecast: Ind. Lifetime Composite Risk/100K NTNC

Exhibit B-61

NTNC Expected Number of Cancer Cases per 100,000 people

MCL = 10 Fg/L Under Lower Bound Scenario 

Statistics: Value

Mean 2.6E-01

Standard Deviation 6.4E-01

Frequency Chart

.000

.046

.092

.138

.184

0

460.7

921.5

1843

0.0E+0 5.0E-1 1.0E+0 1.5E+0 2.0E+0

10,000 Trials 266 Outliers

Forecast: Ind. Lifetime Composite Risk/100K NTNC U

Exhibit B-62

NTNC Expected Number of Cancer Cases per 100,000 people

MCL = 10 Fg/L Under Upper Bound Scenario 
Appendix B, Bladder Cancer Risk Analysis B-48 Proposed Arsenic in Drinking Water Rule RIA

Statistics: Value

Mean 7.6E-02

Standard Deviation 2.0E-01

Frequency Chart

 x10-5

.000

.046

.092

.138

.184

0

461

922

1844

0.0E+0 1.5E-1 3.0E-1 4.5E-1 6.0E-1

10,000 Trials 250 Outliers

Forecast: Ind. Lifetime Composite Risk/100K NTNC

Exhibit B-63

NTNC Expected Number of Cancer Cases per 100,000 people

MCL = 5 Fg/L Under Lower Bound Scenario

Statistics: Value

Mean 1.6E-01

Standard Deviation 3.9E-01

Frequency Chart

.000

.044

.088

.131

.175

0

438

876

1752

0.0E+0 3.1E-1 6.3E-1 9.4E-1 1.3E+0

10,000 Trials 261 Outliers

Forecast: Ind. Lifetime Composite Risk/100K NTNC U

Exhibit B-64

NTNC Expected Number of Cancer Cases per 100,000 people

MCL = 5 Fg/L Under Upper Bound Scenario
Appendix B, Bladder Cancer Risk Analysis B-49 Proposed Arsenic in Drinking Water Rule RIA

Statistics: Value

Mean 4.7E-02

Standard Deviation 1.2E-01

Frequency Chart

 x10-5

.000

.052

.103

.155

.207

0

516.7

2067

0.0E+0 1.0E-1 2.0E-1 3.0E-1 4.0E-1

10,000 Trials 244 Outliers

Forecast: Ind. Lifetime Composite Risk/100K NTNC

Exhibit B-65

NTNC Expected Number of Cancer Cases per 100,000 people

MCL = 3 Fg/L Under Lower Bound Scenario

Statistics: Value

Mean 1.0E-01

Standard Deviation 2.4E-01

Frequency Chart

.000

.045

.090

.135

.180

0

450.2

900.5

1801

0.0E+0 2.0E-1 4.0E-1 6.0E-1 8.0E-1

10,000 Trials 248 Outliers

Forecast: Ind. Lifetime Composite Risk/100K NTNC U

Exhibit B-66

NTNC Expected Number of Cancer Cases per 100,000 people

MCL = 3 Fg/L Under Upper Bound Scenario