Memo: Chlorate and Nitrosamine Occurrence Data from States June 21, 2013

Page 1 of 5

Memo

Date:    June 21, 2013

To:    Ali Arvanaghi, U.S. EPA

From:    Brent Ranalli, The Cadmus Group

Subject: Chlorate and Nitrosamine Occurrence Data Gathered by States and Reported to EPA

During the Second Six‐Year Review Process

This memo provides a summary of occurrence findings for chlorate, NDBA, NDEA, NDMA, NDPA,

NMEA, and NPYR from state drinking water databases that were submitted to EPA during the second

Six‐Year Review, or otherwise obtained by EPA from public sources.

Background

Because there is no national database that receives and stores all relevant data regarding the

occurrence of regulated or unregulated contaminants in public drinking water systems, EPA conducted a

voluntary data call‐in from the states, territories, and tribes to obtain regulated contaminant occurrence

data in support of national occurrence assessments conducted for the second Six‐Year Review. EPA

worked with the states and primacy agencies to receive the states’ and agencies’ complete records of

compliance monitoring data (public drinking water system regulated contaminant occurrence data) for

specified contaminants for 1998 through 2005. Using these data, EPA established a high quality national

contaminant occurrence database consisting of data from 47 states/primacy agencies (45 states plus

Region 8 and Region 9 tribes) for the regulated contaminants requested. For more details on the Six‐

Year Review Information Collection Request (ICR) Dataset, refer to USEPA (2009).  

Six states and the Region 9 tribes submitted PWS occurrence data for unregulated contaminants

in addition to their data for regulated contaminants. EPA was able to supplement these data on

unregulated contaminants by downloading additional publicly available monitoring data from state Web

sites (specifically, from Florida and Wisconsin). The result was a collection of unregulated contaminant

monitoring data from nine states (eight states and one tribal entity; this memo uses the term “state” for

SDWA primacy entities for convenience). The nine data sets vary in the range of monitoring dates (in

some cases extending beyond the 1998‐2005 period of interest for Six‐Year Review), the number of

contaminants monitored, the number of systems reporting monitoring, and the number of samples

taken. The number of systems varies widely in completeness of coverage relative to all the PWSs in the

state.  
Memo: Chlorate and Nitrosamine Occurrence Data from States June 21, 2013

Page 2 of 5

Chlorate

California was the only state that submitted monitoring data for chlorate. Drinking water

occurrence data for chlorate were submitted from California for 2001 through 2007 (Exhibit 1 through

Exhibit 3). Chlorate results from approximately 1% of community water systems (CWSs) and 0.1% of

non‐transient non‐community water systems (NTNCWSs) in the State of California were included in the

data submitted. Precise information about methods used and reporting levels is not available for this

data set. Minimum detected concentrations are reported in Exhibit 1; these minimum values may be

suggestive of reporting levels used.

An analysis of the California data indicates that chlorate was detected in 945 (78.4%) of 1,205

drinking water samples. These detections occurred in 24 (53.3%) of the 45 systems that reported data.

Detected concentrations ranged from 0.01 μg/L to 747 μg/L. Ten systems (22.2%) reported detections of

chlorate greater than the HRL.

Exhibit 1: Chlorate State Drinking Water Occurrence Data – Summary of Detected 

Concentrations 

State 

(Date Range) 

Source Water 

Type 

Concentration Value of Detections (μg/L) 

Minimum Median 90th Percentile 99th Percentile Maximum 

California 

(2001-2007)

Ground Water 0.16 22.5 43.5 50.25 51 

Surface Water 0.01 113 244.2 486.18 747 

Total 0.01 110 244 483.84 747 

Exhibit 2: Chlorate State Drinking Water Occurrence Data – Summary of Samples 

State 

(Date Range) 

Source Water 

Type 

Total 

Number 

of 

Samples 

Samples with 

Detections 

Samples with 

Detections > 1⁄2 HRL 

(105 μg/L) 

Samples with 

Detections > HRL 

(210 μg/L) 

Number Percent Number Percent Number Percent 

California 

(2001-2007) 

Ground Water 47 6 12.8% 0 0.0% 0 0.0% 

Surface Water 1,158 939 81.1% 501 43.3% 149 12.9% 

Total 1,205 945 78.4% 501 41.6% 149 12.4% 
Memo: Chlorate and Nitrosamine Occurrence Data from States June 21, 2013

Page 3 of 5

Exhibit 3: Chlorate State Drinking Water Occurrence Data – Summary of Systems 

State 

(Date Range) 

Source Water 

Type 

Total 

Number 

of 

Systems 

Systems with 

Detections 

Systems with 

Detections > 1⁄2 HRL 

(105 μg/L) 

Systems with 

Detections > HRL 

(210 μg/L) 

Number Percent Number Percent Number Percent 

California 

(2001-2007) 

Ground Water 19 4 21.1% 0 0.0% 0 0.0% 

Surface Water 26 20 76.9% 17 65.4% 10 38.5% 

Total 45 24 53.3% 17 37.8% 10 22.2% 

Nitrosamines

Unregulated contaminant monitoring data from California are available for all six of the

nitrosamines. Additional, very limited data on one of the nitrosamines (one sample tested for NDPA) are

available from Illinois. Precise information about methods used and reporting levels is not available for

the state data. Minimum detected concentration values, presented in the tables, may be suggestive of

reporting levels used for particular contaminants.

NDMA drinking water occurrence data were submitted from California (Exhibit 4 through Exhibit

6). The data indicate that NDMA was detected in 1,531 (33.8%) of 4,532 drinking water samples. These

detections occurred in 24 (23.8%) of 101 systems that reported data. Detected concentrations ranged

from 0.001 μg/L to 440 μg/L, with all reported concentrations greater than the HRL of 0.0006 μg/L.

Exhibit 4: NDMA State Drinking Water Occurrence Data – Summary of 

Concentrations Detected 

State 

(Date Range) 

Source Water 

Type 

Concentration Value of Detections (μg/L) 

Minimum Median 90th Percentile 99th Percentile Maximum 

California 

(2001-2007)

Ground Water 0.001 0.01 0.17 0.4 440

Surface Water 0.001 0.009 0.17 0.795 12

Total 0.001 0.009 0.17 0.651 440
Memo: Chlorate and Nitrosamine Occurrence Data from States June 21, 2013

Page 4 of 5

Exhibit 5: NDMA State Drinking Water Occurrence Data – Summary of System 

Data 

State 

(Date Range) 

Source Water 

Type 

Total 

Number 

of 

Systems 

Systems with 

Detections 

Systems with 

Detections > 1⁄2 HRL 

(0.0003 μg/L) 

Systems with 

Detections > HRL 

(0.0006 μg/L) 

Number Percent Number Percent Number Percent 

California 

(2001-2007) 

Ground Water 66 10 15.2% 10 15.2% 10 15.2% 

Surface Water 35 14 40.0% 14 40.0% 14 40.0% 

Total 101 24 23.8% 24 23.8% 24 23.8% 

Exhibit 6: NDMA State Drinking Water Occurrence Data – Summary of Sample 

Data 

State 

(Date Range) 

Source Water 

Type 

Total 

Number 

of 

Samples 

Samples with 

Detections 

Samples with 

Detections > 1⁄2 HRL 

(0.0003 μg/L) 

Samples with 

Detections > HRL 

(0.0006 μg/L) 

Number Percent Number Percent Number Percent 

California 

(2001-2007) 

Ground Water 2,581 998 38.7% 998 38.7% 998 38.7% 

Surface Water 1,951 533 27.3% 533 27.3% 533 27.3% 

Total 4,532 1,531 33.8% 1,531 33.8% 1,531 33.8% 

NDEA drinking water occurrence data were submitted from California (Exhibit 7 through Exhibit

9). The data indicate that NDEA was detected in one (0.9%) of 106 drinking water samples at one (7.1%)

of 14 systems reporting data. The detected concentration was 0.03 μg/L, which is greater than the HRL

of 0.0004 μg/L.

Exhibit 7: NDEA State Drinking Water Occurrence Data – Summary of 

Concentrations Detected 

State 

(Date Range) 

Source Water 

Type 

Concentration Value of Detections (μg/L) 

Minimum Median 90th Percentile 99th Percentile Maximum 

California 

(2001-2007)

Ground Water N/A N/A N/A N/A N/A 

Surface Water 0.03 0.03 0.03 0.03 0.03 

Total 0.03 0.03 0.03 0.03 0.03 
Memo: Chlorate and Nitrosamine Occurrence Data from States June 21, 2013

Page 5 of 5

Exhibit 8: NDEA State Drinking Water Occurrence Data – Summary of System 

Data 

State 

(Date Range) 

Source Water 

Type 

Total 

Number 

of 

Systems 

Systems with 

Detections 

Systems with 

Detections > 1⁄2 HRL 

(0.0002 μg/L) 

Systems with 

Detections > HRL 

(0.0004 μg/L) 

Number Percent Number Percent Number Percent 

California 

(2001-2007) 

Ground Water 7 0 0.0% 0 0.0% 0 0.0% 

Surface Water 7 1 14.3% 1 14.3% 1 14.3% 

Total 14 1 7.1% 1 7.1% 1 7.1% 

Exhibit 9: NDEA State Drinking Water Occurrence Data – Summary of Sample 

Data 

State 

(Date Range) 

Source Water 

Type 

Total 

Number 

of 

Samples 

Samples with 

Detections 

Samples with 

Detections > 1⁄2 HRL 

(0.0002 μg/L) 

Samples with 

Detections > HRL 

(0.0004 μg/L) 

Number Percent Number Percent Number Percent 

California 

(2001-2007) 

Ground Water 14 0 0.0% 0 0.0% 0 0.0% 

Surface Water 92 1 1.1% 1 1.1% 1 1.1% 

Total 106 1 0.9% 1 0.9% 1 0.9% 

NMEA drinking water occurrence data were submitted from California. There were no reported

detections of NMEA in 57 samples from four systems.

NDPA drinking water occurrence data were submitted from California and Illinois. There were

no reported detections of NDPA in 439 samples from 55 systems in California. A single sample from a

single system in Illinois was reported as having been tested for NDPA; the contaminant was not

detected.

NDBA drinking water occurrence data were submitted from California. There were no reported

detections of NDBA in 57 samples from four systems.

NPYR drinking water occurrence data were submitted from California. There were no reported

detections of NPYR in 57 samples from four systems.

References

USEPA. 2009. The Analysis of Regulated Contaminant Occurrence Data from Public Water Systems in

Support of the Second Six‐Year Review of National Primary Drinking Water Regulations. EPA‐

815‐B‐09‐006. October 2009.