Comparing Clean Water Act (CWA) National Pollutant Discharge Elimination System (NPDES)
Discharge Monitoring Report (DMR) Data and Toxics Release Inventory (TRI) Data
December 2014
Version 1.0
1.0

Overview

This document provides additional background on the two main sources of wastewaterpollution data supporting EPA’s DMR Pollutant Loading Tool or “Loading Tool”(http://cfpub.epa.gov/dmr/). In particular, this document offers insights on how to compare these twodata sources, Discharge Monitoring Reports (DMR) and Toxics Release Inventory (TRI), as well as
considerations for analysis and interpretation. The Loading Tool allows users to compare the DMR data
search results against TRI data search results and vice versa. The tool clearly labels the source of datawhen displaying search results but does not mix TRI or DMR data when calculating pollutant discharges.
2.0

Background on TRI and DMR

The programs under which EPA collects TRI and DMR data are the Emergency Planning andCommunity Right-to-Know Act (EPCRA) and the Clean Water Act (CWA) National Pollutant Discharge
Elimination System (NPDES), respectively.
EPCRA was created to help communities plan for emergencies involving hazardous substances.
The Community Right-to-Know provisions help increase the public’s knowledge and access to
information on chemicals at facilities, their uses, and releases to the environment. TRI collects toxic
chemical use and release data from facilities and provides this information to the public. Each year,
facilities that meet certain thresholds must report their estimated releases and other waste
management activities for listed toxic chemicals. Facilities must report the quantities of toxic chemicals
recycled, collected, and combusted for energy recovery, treated for destruction, or disposed. The TRI listof chemicals includes more than 650 chemicals and chemical categories. In general, chemicals coveredby the TRI Program are those that cause one or more of the following: (1) cancer or other chronic
human health effects; (2) significant adverse acute human health effects; and (3) significant adverse
environmental effects. Please see the TRI program web page 1 for a list of chemicals reported in the TRI
program. Industrial facilities classified as direct dischargers release wastewaters directly into surface
waters of the U.S. Indirect dischargers discharge wastewaters to publicly owned treatment works(POTWs) for further treatment prior to release into the environment. A single facility may have both
direct and indirect discharges.
The NPDES program aims to protect and restore the quality of U.S. rivers, lakes, and coastal
waters through permit requirements to monitor and control pollutant discharges from point sources.
The Clean Water Act requires all point source dischargers to obtain a NPDES permit and reportcompliance with NPDES permit limits via monthly DMRs submitted to the permitting authority. The
permitting authority then enters these data into EPA’s Integrated Compliance Information System (ICISNPDES) or their own state NPDES program database and checks whether the discharger is in compliancewith the NPDES permit requirements. Facilities report pollutant discharge monitoring data in their DMR
as mass-based quantities (e.g., pounds per day) and/or concentrations (e.g., mg/L); however, discharges
1

See: http://www2.epa.gov/toxics-release-inventory-tri-program/tri-listed-chemicals

1are reported using a wide variety of units. Pollutants in ICIS-NPDES include water quality parameters(such as pH and temperature), specific chemicals, conventional parameters [such as biochemical oxygen
demand (BOD 5 ) and total suspended solids (TSS)], and flow rates. Although other pollutants may bedischarged, ICIS-NPDES contain data only for the parameters identified in the facility’s NPDES permit.
Facilities report discharges in concentration or quantity units as average, total, maximum, or minimum
values.
EPA developed the DMR Pollutant Loading Tool to identify facilities that discharge, what
pollutants they are discharging and how much, and where they are discharging. The tool calculates
pollutant loadings from permit and DMR data from ICIS-NPDES, and presents pollutant loadings as
pounds per year and as toxic-weighted pounds per year to account for variations in toxicity among
pollutants. The search results rank dischargers, industries, and watersheds based on pollutant mass andtoxicity, and present “top ten” lists to show which discharges are important, which facilities andindustries are producing these discharges, and which watersheds are impacted. The tool also includes
wastewater pollutant discharge data from TRI.
Figure 1 illustrates the types of wastewater streams that can be characterized using TRI andDMR discharge data. TRI data capture discharges to receiving streams and chemical transfers to POTWs
from industrial facilities. DMR data capture discharges to receiving streams by industrial facilities and
POTWs. Neither data set captures municipal discharges to POTWs.
Municipal discharge
to POTW:
DMR
TRI

Wastewater transfer
to POTW:
DMR
TRI

Industrial discharge
to receiving stream:DMR
TRI

POTW discharge to
receiving stream:
DMR
TRI
Images : Tracey Saxby. Integration and Application Network, University of Maryland Center for Environmental Science (ian.umces.edu/imagelibrary/)

Figure 1. Wastewater Streams in DMR and TRI Data
Figure 2 illustrates the data flow from facilities to ICIS-NPDES and TRI. The figure highlights key
differences in:••••Reporting requirements;
Discharge quantification and measurement methods;
Reporting frequencies; andData uploaded to EPA’s systems.

2

TRI requires reporting for
facility meeting industry,
activity-level, and size
requirements

NPDES permit requires
direct discharging facility
to report DMRs

Chemical release
estimated once
annually using
monitoring data, massbalance, or engineering
estimate

Chemical analysis
performed at afrequency dictatedby NPDES permit

Facility submits
DMR to State
Environmental
Agencies or
permitting
authorities

Facility submits

Toxics
TRI report
directly to EPA
Releasean annual
Inventory on
basisStates upload
permit and DMR
data into ICISDMR Loading Tool
EPA loads data into Loading
Tool, performs calculations
and comparisonsState reporting requirements
differ for majors and non-majors

Figure 2. DMR and TRI Data Reporting
The ICIS-NPDES database is very useful for evaluating wastewater pollutant discharges for thefollowing reasons:•••Is national in scope, including data from all 50 states, territories, and tribes;
Contains discharge data that facilities determine through effluent chemical analyses andmetered flow; andIncludes information for all facilities that discharge directly to surface waters (e.g., rivers, lakes,
and coastal waters).

The data collected in TRI is also very useful for evaluating wastewater pollutant discharges forthe following reasons:••••

TRI includes data from all 50 states, territories, and tribes;
TRI includes transfers to POTWs (i.e., indirect dischargers), not just facilities that discharge
directly to surface waters (i.e., direct discharges);
TRI includes discharge data from manufacturing NAICS codes and some other industrial
categories which may handle significant quantities of toxic chemicals; andTRI includes releases of many chemicals, not just those already identified as problems andlimited in facility discharge permits.

3

2.1

Considerations When Using DMR Data in EPA’s ICIS-NPDES

More than 180,000 industrial facilities and municipal wastewater treatment plants haveobtained NPDES permits for discharges of regulated pollutants. Facilities may be covered underindividual or general NPDES permits. General NPDES permits cover multiple facilities that have similar
discharges and are located in a specific geographic area and apply the same or similar conditions to alldischargers covered under the permit. Individual NPDES permits are unique to each facility. The
limitations and other conditions in an individual permit are based on the facility's operations, type andamount of discharge, and receiving stream, among other factors. ICIS-NPDES does not have DMR data
for all facilities with NPDES permits. All authorized states are required to report facility and some permit
data (PDF) for all facilities (“major” and “non-major”) 2. EPA has facility, permit, and DMR data on mostmajor facilities and less facility and permit data on individually permitted non-major facilities and nonmajor general permit covered facilities (Figure 3).

Figure 3: Number of NPDES Permits in ICIS-NPDES (FY13)
For “major” facilities, EPA expects authorized states to enter compliance and enforcement
information into the national database for at least 95% of their permitted facilities. For “non-major” (or“minor”) facilities, EPA does not require authorized states to enter compliance and enforcement
information into ICIS-NPDES; however, many authorized states are providing the information
voluntarily. The amount of DMR data on non-major permitted facilities in ICIS-NPDES is expected to rise
as more states move towards electronic collection and management of these data. Currently, about halfof the individually permitted non-major facilities have their DMR data in ICIS-NPDES.

2

A “major” NPDES facility is classified as such by the regional administrator, or in the case of approved state
programs, the regional administrator in conjunction with the state director. Major municipal dischargers include all
facilities with design flows of greater than one million gallons per day and facilities with EPA/state approved
industrial pretreatment programs. Major industrial facilities are determined based on specific ratings criteria
developed by EPA/State.

4

The following are some additional limitations of the DMR data collected in EPA’s ICIS-NPDES
database:
•
•
•
•

•

ICIS-NPDES contains data only for pollutants a facility is required by permit to monitor; thefacility is not required to monitor or report all pollutants actually discharged.
ICIS-NPDES includes very limited data characterizing indirect discharges from industrial facilities
to POTWs.
Many of the pollutant parameters included in ICIS-NPDES are not chemical compounds (e.g.,“total Kjeldahl Nitrogen,” “oil and grease”) and cannot have toxic weighting factors (TWFs).
Some facility reports in ICIS-NPDES lack applicable SIC codes and only a few facilities in ICISNPDES provide information on applicable NAICS codes. This can limit the user’s ability to searchon these fields.
DMR data may be entered into the ICIS-NPDES database manually, which leads to data-entry
errors.

Additionally, some NPDES permitted facilities have intermittent discharges and may have one ormore outfalls that don’t discharge for one or more months. ICIS-NPDES has ways of identifying when
there is no discharge at a particular outfall for an entire monitoring period. In such cases, the Loading
Tool does not calculate pollutant loads for these outfalls during these monitoring periods.
EPA also developed a methodology with the states to estimate intermittent discharges that
occurring within a monitoring period (e.g., there is a discharge from the outfall but it only occurs twodays out of the monthly monitoring period). Specifically, the Loading Tool uses three ICIS-NPDES"Duration of Discharge" codes for identifying these intermittent dischargers (50037, 82517, and 81381).
The Loading Tool will automatically adjust the pollutant loading calculation such that the calculation only
estimates pollutant discharges for the time when the outfall is discharging (e.g., two days in the monthinstead of the entire month).
However, not all NPDES permits require permittees to submit these Duration of Discharge codeswhen intermittent discharges occur within a monitoring period. Consequently, the tool may
overestimate pollutant discharges for these intermittent dischargers that do not report these Durationof Discharge codes. NPDES permittees with intermittent discharges are encouraged to engage with theirpermit writers to add one of these Duration of Discharge codes to their DMR.
Considerations When Using EPA’s TRI Data

2.2

TRI provides annual wastewater chemical releases (lb/year) for direct and indirect discharging
facilities. The following are some considerations when using TRI data for evaluating wastewaterpollutant discharges:••

Small establishments (less than 10 employees) are not required to report, nor are facilities that
do not meet the reporting thresholds. Therefore, facilities reporting to TRI may not provide acomplete picture of an industrial.
Release reports are in part based on estimates as there is no requirement for monitoring. In
addition to monitoring information if available, the estimated release reports could be based onemission factors, mass balance or engineering calculations or other methodology which may
result in inaccurately reported releases. For example, TRI encourages facilities to report some
5

•
•
•
•

compounds as present at one-half the detection level if a facility suspects that the compound is
known or reasonably anticipated to be present, even if measured data show the compound is
below its detection level. As a result, many companies are conservative and adopt thisapproach. For facilities with large flows, this can result in large estimates of pounds or TWPE ofpollutant released with no measurements to support that the compound was ever present
above the detection level.
Certain chemicals (e.g., Glycol Ethers are reported as a class, not as individual compounds.
Because the individual compounds in the class have widely varying toxic effects, the potential
toxicity of chemical releases can be inaccurately estimated.
The list of chemicals covered by TRI is not all-inclusive.
Only facilities in certain industrial sectors (identified by NAICS codes) are required to report;
therefore, some sources of water pollutant discharges are not included.
A facility is not required to report releases if the facility does not exceed the chemical activity
threshold.

The following table on the number of TRI reporters that provide data on wastewater pollutant
discharges is showing Figure 4.

Figure 4: Number of TRI Reports with Separate Counts of Direct and Indirect Dischargers
As noted above, TRI does not require facilities to sample and analyze wastewater streams todetermine the quantities of toxic chemicals released. Facilities may estimate releases based on massbalance calculations, published emission factors, site-specific emission factors, or other approaches.
Facilities must indicate the basis of their release estimate using reporting codes, which are provided
below:
M1: continuous monitoring data or measurements;
M2: periodic or random monitoring data or measurements;
C:
mass balance calculations, such as calculation of the amount of the toxic chemical in streams
entering and leaving process equipment;E:published emission factors;
E2: site-specific emission factors; andO:other approaches, such as engineering calculations.

6

Additionally, TRI allows facilities to report releases as specific numbers or as ranges, if
appropriate. Specific estimates are encouraged if data are available to ensure the accuracy; however,
EPA allows facilities to report releases for non-persistent chemicals in the following ranges: 1 to 10
pounds, 11 to 499 pounds, and 500 to 999 pounds. If a release is reported as a range, the Loading Tool
uses the mid-point of the reported range to represent that release.
2.3

DMR Pollutant Loading Tool Comparison Feature

EPA developed the TRI and DMR Comparison Feature in 2013. The Comparison Feature provides
information on the differences in discharges reported in DMRs and to TRI for each reporting year since2007, presented in:•••Pounds per year;
Toxic-weighted pounds per year; andPercent difference.

Figure 5: Loading Tool ‘Compare DMR and TRI’ page
To view the comparison page for an individual facility, users can easily view both DMR and TRI
pollutant discharge estimates in the Loading Tool by using the buttons shown below in Figures 6 and 7.
The comparison feature only compares DMR loadings to TRI direct releases.

7Figure 6: Links available on the Facility Information (DMR) page that navigate to the ‘Compare DMR and
TRI’ page

Figure 7: Links available on the Facility Information (TRI) page that navigate to the ‘Compare DMR and
TRI’ page
DMRs use parameter codes to identify pollutants. These parameter codes are specific to the CAS
number and analysis type. As a result, multiple parameter codes may exist for a single CAS number (e.g.,
total residual chlorine, free available chlorine).
TRI chemicals are identified, for the most part, using CAS numbers. TRI also includes chemical
categories, such as glycol ethers and chlorophenols, which comprise multiple CAS numbers. Whenlinking DMR parameters to TRI chemicals, there is potential for double counting loads when individual
TRI chemicals are also included in TRI chemical categories. For example, 2,4,5-Trichlorophenol is a TRI
chemical but also falls under the chlorophenols chemical category. To avoid double counting, the8Loading Tool groups TRI chemicals within their broader chemical categories, and produced a list of
unique chemical groups that link to multiple CAS numbers.
To create the chemical crosswalk between the two programs, EPA uses the CAS numbers to
identify the DMR parameters and TRI chemicals that should be included in each chemical group. To
match DMR data to TRI-reported discharges, and to avoid double-counting within DMR and TRI, EPA
groups and sums the pollutant discharges in DMR and TRI data to the chemical group level and matches
on a unique chemical group ID. The DMR/TRI/Chemical Group crosswalk is available on the User Guidetab.
The Loading Tool uses Facility Registry System (FRS) identification numbers to link NPDES permit
numbers to TRI facility IDs. FRS uniquely identifies a facility by assigning an identification number (FRS
ID), and uses this FRS ID to link together all regulatory program database records (such as permit IDs andfacility IDs that facilities use in reporting to EPA).
2.4

Summary of General Data Considerations and Potential Uses

As previously noted, not all facilities report the same pollutants on their DMRs or on their TRI
reports to EPA. These differences in pollutant reporting mean that there will likely not be a one-to-one
match between pollutant discharges displayed by the Loading Tool (e.g., EZ Search (DMR) and TRI
Search). In particular, the TRI program focuses on toxic pollutant discharges and the NPDES program
focuses on all aspects of water pollution. Consequently, the results of EZ Search (DMR) may show Total
Suspended Solids (TSS) as the top pollutant discharge while the corresponding TRI search will not display
any results for TSS (as TSS is not a toxic pollutant and is not reported under the TRI program).
Additionally, the universes of facilities that report under the NPDES and TRI programs do not
overlap perfectly. For example, POTWs do not report under the TRI program. Consequently, the Loading
Tool will have pollutant discharge data for a facility that submits DMRs that are imported into ICISNPDES even when the facility does not report under the TRI program. Conversely, the Loading Tool will
have estimates of pollutant discharges to surface waters and POTWs for a TRI reporting facility evenwhen the facility's DMR data is not in ICIS-NPDES. Table 1 summarizes some of the key considerations
for comparing DMR and TRI data.
Table 1. DMR and TRI Data Considerations for a Comparative Analysis
Data
Scope/Limitations

DMR Considerations

Facility universe

Permitting authorities are not required toreport DMR measurements for non-majors
to EPA’s ICIS-NPDES.

Chemical universe

Facilities only report discharges of pollutants
for which their NPDES permit requires themto monitor. Other pollutants may bedischarged but are not reported on DMRs.

Industryclassification

Some facilities in ICIS-NPDES do not have SIC
or NAICS code data. As a result, it may not
9

TRI Considerations
Facilities may be exempt from
reporting due to industry
classification or number of
employees.
Facilities only report chemicals
on the TRI list and may be
exempt from reporting certain
chemicals due to activity
thresholds.
The primary NAICS code in TRI is
associated with the facility’s

be straightforward to determine industrial
classification.
The primary industrial activity reported in
DMR data may differ from the primaryindustrial activity reported in TRI.

Data quality

Data entry errors and incorrectly identified
units of measure can significantly impact
loading calculations.

revenues, and may not relate toits pollutant discharges. 3

Facilities can use engineering
estimates, emissions factors, andmass balances to report
pollutant releases. Not all
releases are based on
measurements.

Users of the Loading Tool can use DMR and TRI data to investigate the following questions forfacilities or industrial sectors of interest:
•
•
•
•
•
•
5.0

What pollutants are discharged? What is the mass (pounds) or hazard (toxic-weighted pound
equivalents) associated with these pollutants?
What facilities or industrial sectors contribute the most wastewater pollution (in terms ofpounds or toxic-weighted pound equivalents) for a geographic area of interest to the user?
What is the geographic distribution of the facilities or industrial sectors of interest to the user?
Are there any discharge trends for the facility or industrial sector?
Is there a match between what is being discharged and an impairment in the receiving
waterbody?
What percentage of the raw pollutant loadings pass through on-site treatment and/or POTW
treatment into surface waters?
Additional Considerations When Using DMR and TRI Data

There are also some additional considerations when comparing DMR and TRI data. The following
discussions provide more information on how to use, compare, and interpret DMR and TRI data.
5.1

Ammonia Reporting

There is a difference in how aqueous ammonia (CAS # 7664-41-7) is reporting to EPA on TRI
reports and on DMRs. This section describes this difference and how to compare DMR and TRI data forthis chemical.
5.1.1

TRI Ammonia Reporting

Ammonia is included on the TRI toxic chemical list with the qualifier "includes anhydrous
ammonia and aqueous ammonia from water dissociable ammonium salts and other sources; 10 percent
of total aqueous ammonia is reportable under this listing." 4 As this qualifier indicates, the quantities
applied to TRI threshold determinations depend on the specific form of ammonia manufactured,
processed, or otherwise used, and released and the discharge of ammonia to POTWs and surface waters
3

See http://tri.supportportal.com/link/portal/23002/23021/Article/21087/What-is-the-definition-of-primaryNAICS-code-How-can-there-be-more-than-one-NAICS-code-for-a-facility
4
See: http://www2.epa.gov/sites/production/files/2014-01/documents/rfi_table_ii_ry2013_112513_abt.pdf

10also depend on the form of ammonia. The term "anhydrous" means "lacking water," whereas "aqueous"means "dissolved in water."
If anhydrous ammonia is manufactured, processed, or otherwise used, then 100 percent of theanhydrous ammonia must be counted when determining whether an activity threshold has been
exceeded. If the facility exceeds an activity threshold for ammonia (anhydrous and/or aqueous), then allof the anhydrous ammonia released and otherwise managed as waste must be included in the facility's
release and other waste management calculations.
Total aqueous ammonia includes both the ionized (NH 4 +) and un-ionized (NH 3 ) forms ofammonia present in aqueous solutions (e.g., wastewater). When a facility manufactures, processes, orotherwise uses aqueous ammonia, it is conducting a threshold activity on 100 percent of the aqueous
ammonia. However, the facility owner or operator counts only 10 percent of the total aqueous ammonia
involved in a covered activity when making threshold determinations. Similarly, when estimating annual
releases and other waste management estimates of ammonia from a facility, only 10 percent of thetotal aqueous ammonia must be included in the calculations. This means that when a facility discharges
aqueous ammonia to a POTW or surface water it will only report 10 percent of the total quantity of
aqueous ammonia released or transferred on its TRI report. If the source of aqueous ammonia is thedissociation of ammonium salts in water, total aqueous ammonia (calculated in terms of NH 3
equivalents) is calculated from the weight percent of the NH 3 equivalents of the ammonium salt. EPA
applies this 10 percent factor to estimate the portion of the aqueous ammonia that is toxic. 5 The
following is an example. 65

See EPA’s rulemaking on this issue for more information (30 June 1995; 60 FR 34179).
U.S. EPA, 2000. “Emergency Planning And Community Right-To-Know Section 313: Guidance for Reporting
Aqueous Ammonia,” EPA 745-R-00-005, December 2000. The example shown here is Example #6 in this TRI
guidance document, which is available at:
http://www2.epa.gov/sites/production/files/documents/2000ammonia.pdf.
611

In a calendar year, a facility uses 1,250,000 pounds of ammonium nitrate,
NH 4 NO 3 , in aqueous solution which is released to waste water streams, thentransferred to a POTW. The NH 3 equivalent wt% of ammonium nitrate is 21.28%.
The total quantity of aqueous ammonia present in solution is 21.28% of the
1,250,000 pounds of ammonia chloride used, or 266,000 pounds.
The quantity applied towards threshold determinations for the ammonia listingis 10 percent of the total quantity of aqueous ammonia present in solution, or
26,600 pounds. The quantity of ammonia reported as released or transferred is
10 percent of the total quantity of aqueous ammonia released or transferred, or
26,600 pounds.
5.1.2

DMR Ammonia Reporting

NPDES permitted facilities that are required to monitor their wastewater for ammonia
discharges typically report all of their discharges of aqueous ammonia (i.e., no 90% reduction factor).
The wastewater analytical methods approved for measurement of for ammonia at Part 136, including
EPA Method 350.1, are designed to measure 100% of the total unionized (NH 3 ) and ionized (NH 4 +) formsof ammonia. Consequently, the permit limits and corresponding DMRs capture 100 percent of theaqueous ammonia discharged by the NPDES regulated entity.
5.1.3

Comparing DMR and TRI Ammonia Reporting

One suggested method to make a direct comparison between TRI and DMR ammonia loads is toestimate TRI ammonia releases by multiplying the reported TRI ammonia release by 10 and thencompare this value to the DMR ammonia load.
5.2

Dioxin Reporting

Dioxin discharges may be reported differently on DMRs and TRI reports and the difference ismainly due to differing EPA guidance on how to report dioxin discharges when the measured
wastewater dioxin concentration is below the laboratory analytical method detection limit. This section
describes this difference and how to compare DMR and TRI data for this chemical group. Dioxin is very
toxic as compared to other wastewater pollutants so even small amount of dioxin (in terms of mass)translate to large amount of toxic pollution (in terms of toxic-weighted pound equivalents or TWPE).
The term ‘dioxins’ refers to polychlorinated dibenzo-p-dioxins (CDDs) and polychlorinateddibenzofurans (CDFs), which constitute a group of persistent bioaccumulative and toxic chemicals. There
are 17 CDDs and CDFs congeners with chlorine substitution of hydrogen atoms at the 2, 3, 7, and 8
positions on the benzene rings, the most toxic of which is 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD).
The 17 compounds (called congeners) are referred to as ‘dioxin-like,’ because they have similar chemical
structure, similar physical-chemical properties, and invoke a common battery of toxic responses, though12the toxicity of the congeners varies greatly. In this document, EPA uses the term “dioxin and dioxin-likecompounds” to refer to all 17 of the 2,3,7,8-substituted CDDs and CDFs.
EPA developed toxic weighting factors (TWFs) for each of the 17 dioxin congeners, ranging from703,584,000 for 2,3,7,8-TCDD to 2,021 for octachlorodibenzofuran. These TWFs convert the mass of thedioxin discharges to toxic pollution (in terms of TWPE). Due to their toxicity and ability tobioaccumulate, the various dioxin congeners have high TWFs relative to most chemicals. As previously
noted, even small mass amounts of dioxin and dioxin-like compound discharges translate into large
amounts of toxic pollution (in terms of TWPE). Table 2 presents the dioxin congener-specific TWFs usedby the Loading Tool.
Table 2. Dioxins Congeners and Their Toxic Weighting Factors
CAS
NumberChemical Name

Abbreviated Name

Toxic Weighting
FactorCDDs
1746-01-6

2,3,7,8-tetrachlorodibenzo-p-dioxin

2,3,7,8-TCDD

703,584,000

40321-76-4

1,2,3,7,8-pentachlorodibenzo-p-dioxin

1,2,3,7,8-PeCDD

692,928,000

39227-28-6

1,2,3,4,7,8-hexachlorodibenzo-p-dioxin

1,2,3,4,7,8-HxCDD

23,498,240

57653-85-7

1,2,3,6,7,8-hexachlorodibenzo-p-dioxin

1,2,3,6,7,8-HxCDD

9,556,480

19408-74-3

1,2,3,7,8,9-hexachlorodibenzo-p-dioxin

1,2,3,7,8,9-HxCDD

10,595,840

35822-46-9

1,2,3,4,6,7,8-heptachlorodibenzo-p-dioxin 1,2,3,4,6,7,8-HpCDD

411,1363268-87-9

1,2,3,4,6,7,8,9-octachlorodibenzo-p-dioxin 1,2,3,4,6,7,8,9-OCDD

6,586

CDFs
51207-31-9

2,3,7,8-tetrachlorodibenzofuran

2,3,7,8-TCDF

43,819,554

57117-41-6

1,2,3,7,8-pentachlorodibenzofuran

1,2,3,7,8-PeCDF

7,632,640

57117-31-4

2,3,4,7,8-pentachlorodibenzofuran

2,3,4,7,8-PeCDF

557,312,000

70648-26-9

1,2,3,4,7,8-hexachlorodibenzofuran

1,2,3,4,7,8-HxCDF

5,760,000

57117-44-9

1,2,3,6,7,8-hexachlorodibenzofuran

1,2,3,6,7,8-HxCDF

14,109,440

72918-21-9

1,2,3,7,8,9-hexachlorodibenzofuran

1,2,3,7,8,9-HxCDF

47,308,800

60851-34-5

2,3,4,6,7,8-hexachlorodibenzofuran

2,3,4,6,7,8-HxCDF

51,204,160

67562-39-4

1,2,3,4,6,7,8-heptachlorodibenzofuran

1,2,3,4,6,7,8-HpCDF

85,76055673-89-7

1,2,3,4,7,8,9-heptachlorodibenzofuran

1,2,3,4,7,8,9-HpCDF

3,033,984

39001-02-0 1,2,3,4,6,7,8,9-octachlorodibenzofuran
1,2,3,4,6,7,8,9-OCDF
2,021
Source: Toxic Weighting Factor Development in Support of the 304(m) Planning Process 7

5.2.1

TRI Dioxin Reporting7

http://water.epa.gov/scitech/wastetech/guide/304m/upload/2005_09_19_guide_304m_2006_toxic_weighting.pdf

13

When detected in facility discharges, dioxin and dioxin-like compounds are found in minutequantities, e.g., one part-per trillion (1 ppt) or less, and as mixtures of dioxin and the dioxin-likecompounds. Wastewater concentrations are measured with high resolution gas chromatography
combined with high resolution mass spectrometry. For example, EPA Method 1613 (used to quantify
CDDs and CDFs in wastewater, solids, air, and tissue samples) can reliably detect these compounds at or
below one part per trillion [i.e., 10 parts per quadrillion (ppq) in water; 1 ppt in solid waste]. This
presents a challenge in terms of interpretation of results in which a CDD/CDF compound is reported by
the analytical laboratory as “Not Detected” (shown as the abbreviation ‘ND’ on lab sheets).
Even with these extremely low levels of detectability with current laboratory methods, it is notpossible to know with certainty if ‘not detected’ (ND) is actually zero (i.e., that dioxin and dioxin-likecompounds are not present in the sample) or if dioxin and dioxin-like compounds really are present in
the sample at some concentration below the laboratory analytical method detection limit. EPA
recommends that facility’s use monitoring data and emission factors that are consistent with EPA
industry specific guidance.
For example, EPA Method 1613 indicates that laboratory results below the analytical method
detection limit should be reported as not detected (ND) or as required by the regulatory authority. For
purposes of threshold determinations and the reporting of releases and other waste management
quantities for dioxin and dioxin-like compounds under EPCRA section 313, either with monitoring data,
or by using the emission factor approach, non-detects are treated as ‘zero’ if that is how the method
being used treats non-detects (e.g., Method 1613). However, facilities should use their best readily
available information to report, so if a facility has better information than provided by these methods
then that information should be used. For example, if a facility is not detecting dioxin or a particulardioxin-like compound using a particular method but has information that shows that they should be
detecting them the facility should use this other information and it may be appropriate to estimate
quantities using one half the detection limit.
If the method being used by a facility to detect dioxin and dioxin-like compounds is not an EPA
approved method and the detection level being used is not as sensitive as those approved for use under
EPA methods then EPA’s EPCRA section 313 guidance with regard to non-detects should be followed.
This guidance states that facilities must use reasonable judgment as to the presence and amount of alisted toxic chemical based on the best readily available information. An indication that a reportablechemical is below detection is not equivalent to stating that the chemical is not present. If thereportable toxic chemical is known to be present, EPA recommends that a concentration equivalent tohalf the detection limit be used to calculate annual environmental releases. Facilities should not
estimate releases solely on monitoring devices (i.e., measured concentrations), they should also rely on
their knowledge of specific conditions at the plant.
This means that EPA requires TRI reporters to make reasonable estimates of their releases tosurface waters and POTWs (in addition to other air, land, and groundwater releases). TRI reporters may
elect to use the product of one-half the laboratory analytical method quantitation limit and the related
wastewater flow, monitoring time period, and appropriate conversion factors to estimate their annual
releases when all of their wastewater monitoring data is below the laboratory analytical method
quantitation limit.
Additionally, beginning with Reporting Year 2000 through 2007, facilities meeting certain
reporting criteria were required to report to TRI the total mass, in grams, of the 17 dioxin and dioxin-like14compounds released to the environment every year. Facilities were given the option to report a facilityspecific congener distribution, which means that if dioxins are released to more than one medium, thefacility can report only one distribution. Consequently, for 2007 the Loading Tool cannot determine if
the single dioxin congener distribution reported by a facility accurately reflects the dioxin distribution in
wastewater. Nevertheless, this dioxin data is the best available information and the Loading Tool uses it
to calculate the reporting facility’s dioxin TWPE. To account for the relative toxicities of the different
dioxin congeners, the Loading Tool first converts the reported dioxin releases from grams to pounds tobe consistent with the units used for other chemicals. The Loading Tool then calculates dioxin TWPE
estimates using the facility-specific congener distributions for all facilities that reported a distribution.
For Reporting Year 2008 and subsequent years, EPA amended the TRI reporting regulations torequire TRI reporters to provide the mass quantities for each individual member of the dioxin anddioxin-like compounds category, if available, for each reportable release or waste management activity. 8
This means that for Reporting Year 2008 and after the Loading Tool can more accurately estimate thetoxicity for any reported dioxin discharges using the mass of each congener and applying the congener
specific TWF.
5.2.2

DMR Dioxin Reporting

The following approach is used for all pollutants reported on DMRs and it particularly relevant
when reviewing dioxin discharges. As previously noted, even small mass amounts of dioxin and dioxinlike compound discharges translate into large amounts of toxic pollution (in terms of TWPE).
If pollutant concentrations for all monitoring periods in a given year are reported below thelaboratory analytical method quantitation limit then the annual load calculated by EZ Search (DMR) forthat parameter is equal to zero. This means that all pollutant concentrations in a given year are either“0” or qualified with “<”. In practical terms this means that pollutants may have been detected aspresent through wastewater sampling but never reliably quantified during the year.
EZ Search (DMR) uses a hybrid approach for calculating pollutant loads when at least one
monitoring period has a pollutant concentration that is above the laboratory analytical method
quantitation limit. This means that pollutants were reliably quantified at least once during the year,
which confirms the presence of the pollutant in the wastewater discharge. In this case the EZ Search(DMR) annual pollutant load is the sum of:••

The product of the pollutant concentrations that are above the laboratory analytical method
quantitation limit and the related wastewater flow, monitoring time period, and the appropriate
conversion factors; andThe product of one-half the laboratory analytical method quantitation limit and the related
wastewater flow, monitoring time period, and the appropriate conversion factors.

It is important to note this method uses the reported laboratory analytical method quantization
limit. In cases where there is no reported laboratory analytical method quantitation limit in ICIS-NPDES,
the EZ Search (DMR) does not make an estimate of the laboratory analytical method quantitation limit
and uses “0” (zero) for the pollutant load for that monitoring period. Additionally, ICIS-NPDES data entry
8

U.S. EPA, 2007. “Dioxin and Dioxin-like Compounds; Toxic Equivalency Information; Community Right-To-Know
Toxic Chemical Release Reporting,” (10 May 2007; 72 FR 26544).

15

errors where the “<” sign or other qualifier is inadvertently omitted means that the Loading Tool willtreat such values without the “<” qualifiers as being above the laboratory analytical method
quantitation limit (even though they may be reported on the paper DMRs with the appropriate “<”
qualifiers). Finally, it is also important to note that the hybrid approach is the method EPA uses tocalculate annual pollutant loadings for its review of industrial sources of wastewater and develop is
Biennial Effluent Guidelines Program Plan (see Section 304(m) of the CWA).
5.2.3

Comparing DMR and TRI Dioxin Reporting

To understand differences between DMR and TRI pollutant discharge estimates it is importantto review the underlying DMR monitoring data. These monitoring data will indicate whether the facility
reported any measurements above the laboratory analytical method quantitation limit. It is also
important to review the TRI data to determine if these reported values are based on monitoring data,
emission factors, of engineering estimates. Additionally, facilities may not be required to monitor andreport dioxin on their DMRs. In this case, you can use the TRI data to supplement the DMR data.
5.3

Metal Compounds Reporting

There may be differences in how metals and metal compounds are reported to EPA on TRI
reports and on DMRs. This section describes this differences and how to compare DMR and TRI data forthese chemical compounds.
5.3.1

TRI Metal Compounds Reporting

For TRI reporting, facilities report annual releases of metal compounds on a single reporting
form for each parent metal and do not specify the individual compound(s) released. In addition, if the
facility is required to report releases of a metal (e.g., zinc) and its compounds (e.g., zinc compounds), thefacility may report both the metal and metal compound on a single form (reported as the metalcompound). For metal compound reporting, the release quantities are based on the mass of the parent
metal, only. To calculate TWPEs for metal compounds, EPA used the TWF for the parent metal. EPA then
combined the TWPEs for the metal and metal compounds (i.e., TWPE reported for “zinc and zinccompounds,” rather than one TWPE for “zinc” and one TWPE for “zinc compounds”). This analysis does
not double count metal discharges because all discharges are separated until the releases are combined.
For example, if a facility reported 5 pounds of zinc and 10 pounds of zinc compounds, the discharges
would be kept separate in the database but displayed as “Zinc and zinc compounds” in the Comparison
tool.
5.3.2

DMR Metal Compounds Reporting

NPDES permits may require permittees to report discharges of different forms of the samepollutant [e.g., 01042 - Copper, total (as Cu) and 01040 - Copper, dissolved (as Cu)]. As a general rule,
the Loading Tool uses pollutant parameters that represent the total mass of the pollutant discharged[e.g., 01042 - Copper, total (as Cu)] as opposed to parameters that only represent a portion of the total
mass of the pollutant discharges [e.g., 01040 - Copper, dissolved (as Cu)]. However, if the NPDES permit
does not require the total mass of the pollutant to be monitored and reported on the DMR [e.g., 01042 Copper, total (as Cu)], then the Loading Tool will use the available parameter [01040 - Copper, dissolved(as Cu)]. Consequently, this might mean that only a portion of the total mass of a pollutant is monitored
and reported on the DMR and total facility discharges of the pollutant will be underestimated.
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5.3.3Comparing DMR and TRI Metal Compounds Reporting

To understand differences between DMR and TRI pollutant discharge estimates it is importantto review the underlying DMR monitoring data. There may be errors in the DMR data reported to ICISNPDES and used in the Loading Tool calculations and the DMR data may only represent a portion of thetotal mass of the pollutant discharged. Additionally, facilities may not be required to monitor and report
some toxic metals on their DMRs even though they are required to report these toxic metals on their TRI
reports. In this case, you can use the TRI data to supplement the DMR data.
5.4

Chlorine Reporting

There is a difference in how chlorine is reported to EPA on TRI reports and on DMRs. Thissection describes these differences.
5.4.1

TRI Chlorine Reporting

Chlorine (CAS 7782-50-5) and chlorine dioxide (10049-04-4) are TRI chemicals and TRI reporters
must report any releases of these chemicals on their TRI forms. It is important to note that these are thegaseous form of chlorine. For example, at standard temperature and pressure, two chlorine atoms form
the diatomic molecule Cl 2 . Most releases of these gases would be fugitive air releases. More
importantly, use of chlorine and chlorine dioxide gas in manufacturing process water or water treatment
should not be reported on TRI reporting forms as no releases are typically expected of either of thesechemicals to water. Chlorine (Cl 2 ) reacts very quickly with water to form HOCl, Cl-, and H+. Although thisis an equilibrium reaction, at a pH above 4 the equilibrium shifts almost completely toward formation ofthese products. Therefore, essentially zero releases of chlorine (Cl 2 ) to water occur under normal
circumstances. Releases of chlorine dioxide to water should be considered but are unlikely based on its
strong oxidizing potential and the constant supply of organics in the waste stream. 9 The following
describes a common TRI reporting error.
“The most common reporting error for chlorine or chlorine dioxide treated water is reporting
discharges or transfers when the chemicals have been treated on site. As indicated above, if thedischarge is maintained at a pH above 4, none of these chemicals are expected to be released towater streams. Although some facilities may monitor the residual chlorine concentration in theirwater, this parameter does not represent the Cl 2 concentration. Residual chlorine is the sum of the
Cl 2 , HOCl, and OCl-concentrations. Because the Cl 2 concentration will be negligible under neutral pH
conditions, direct discharges to water or transfers to a POTW may be reported as zero.”
Source: EPCRA Section 313 Reporting Guidance for Food Processors (U.S. EPA, 1998)

9

U.S. 1998. “EPCRA Section 313 Reporting Guidance for Food Processors,” EPA-745-R-98-011, September 1998.
Available at; http://www.epa.gov/tri/reporting_materials/guidance_docs/pdf/1998/1998food.pdf

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5.4.2DMR Chlorine Reporting

Many NPDES permits require facilities to monitoring their wastewater for Total Residual
Chlorine or Free Available Chlorine. Free Available Chlorine is defined as the concentration of residual
chlorine in water present as dissolved gas (Cl 2 ), hypochlorous acid (HOCl), and/or hypochlorite ion (OCl-).
Total Residual Chlorine (TRC) is the sum of total of Free Available Chlorine and combined (bound)residual chlorine. Total Residual Chlorine or Free Available Chlorine are toxic to aquatic communities
and have TWFs for estimating toxic pollution.
5.4.3

Comparing DMR and TRI Chlorine Reporting

Users of TRI data should consider any reporting of chlorine and chlorine dioxide to surface
waters or POTWs as errors. These data should be excluded from consideration. In order to make a more
direct comparison between TRI and DMR data, you may wish to separately count Total Residual Chlorine
or Free Available Chlorine DMR pollutant discharges as the TRI program does include these chemicals intheir reporting requirements.
5.5

Polycyclic Aromatic Compounds
The TRI program defines polycyclic aromatic compounds (PACs) as the following chemicals. See

Table 3.
Table 3. List of Chemicals in the TRI Polycyclic Aromatic Compound (PAC) Group (N590)
CAS Number
56-55-3
205-99-2
205-82-3
207-08-9
206-44-0
189-55-9
218-01-9
50-32-8
226-36-8
224-42-0
53-70-3
194-59-2
5385-75-1
5.5.1

Chemical Name
Benz(a)anthracene
Benzo(b)fluoranthene
Benzo(j)fluoranthene
Benzo(k)fluoranthene
Benzo(j,k)fluorene
Benzo(r,s,t)pentaphene
Benzo(a)phenanthrene
Benzo(a)pyrene
Dibenz(a,h)acridine
Dibenz(a,j)acridine
Dibenzo(a,h)anthracene
7H-Dibenzo(c,g)carbazole
Dibenzo(a,e)fluoranthene

CAS Number
192-65-4
189-64-0
191-30-0
57-97-642397-64-8
42397-65-9
193-39-5
56-49-53697-24-3
7496-02-8
5522-43-0
57835-92-4

Chemical Name
Dibenzo(a,e)pyrene
Dibenzo(a,h)pyrene
Dibenzo(a,l)pyrene
7,12-Dimethylbenz(a)-anthracene
1,6-Dinitropyrene
1,8-Dinitropyrene
Indeno(1,2,3-cd)pyrene
3-Methylcholanthrene
5-Methylchrysene
6-Nitrochrysene
1-Nitropyrene
4-Nitropyrene

TRI and DMR Reporting for Polycyclic Aromatic Compounds

For reporting to TRI, facilities may not monitor for the individual chemicals in the PACs and may
rely instead on industry emissions estimates or engineering calculations for reporting. NPDES permits
may require permitees to sample and analyze wastewater discharges for some or all of these pollutants
and to report the results on DMRs. The DMR forms do not group these chemicals into one group like the
TRI reporting process.

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5.5.2Comparing DMR and TRI Data for Polycyclic Aromatic Compounds

When understanding differences between DMR and TRI pollutant discharge estimates of toxic
organics it is important to review the underlying DMR monitoring data. There may be errors in the DMR
data reported to ICIS-NPDES and used in the Loading Tool calculations and the DMR data may only
represent a portion of the chemicals listed in the TRI PAC chemical group. Facilities may not be required
to monitor and report some toxic metals on their DMRs even though they are required to report these
toxic organics on their TRI reports. In this case, you can use the TRI data to supplement the DMR data.
Phosphorus (Yellow or White)

5.6

Phosphorus (yellow or white) is the elemental form of phosphorus and is very unstable. It isinsoluble in water but is pyrophoric (i.e., auto-ignites upon contact with air). More important, this formof phosphorus is not the same form of phosphorus commonly measured in wastewater. Users of TRI
data should consider any reporting of phosphorus (yellow or white) to surface waters or POTWs as
errors. These data should be excluded from consideration.
6.0

DMR and TRI Data Quality Improvements

The TRI Program conducts a number of activities every year to ensure the quality of TRI datareported to EPA. These activities range from providing facilities with extensive reporting guidance,
intelligent reporting software, and training prior to the reporting deadline as well as data validation andanalysis after the annual reports are received. TRI compliance and enforcement initiatives also aim toensure that facilities submit on-time and accurate reports of their toxic chemical releases. EPA
enforcement staff target facilities that are non-filers or under-reporters, as these actions prevent the full
public disclosure of toxic chemical releases.
Similarly, EPA has implemented mechanisms to review DMR data quality. For example, EPA
designed the Loading Tool to bring the largest discharges to the top of the results, which helps to expose
outliers and potential data entry errors. The tool provides the following functions to facilitate quality
review:•••

Flags results to indicate if loads are calculated using DMR data that the tool identifies aspotential errors;
Provides underlying data and equations that the tool uses to calculate loads from DMR data;
Links to error reporting forms, where users can report data errors to EPA.

Both TRI and DMR data validation procedures include reviewing the data for internalconsistency as well as comparing to other data sources. Linking TRI reported annual releases to annual
discharge loads calculated using DMR data is not always straightforward due to the differences in thereporting requirements. Therefore, EPA developed the Comparison Feature to make it easier for users
to directly compare TRI releases and DMR loads, and to enhance data validation efforts by highlighting
discharges that have the largest differences between TRI and DMR. EPA, states, and facilities can use theComparison Feature to identify discrepancies in discharges reported to DMR and TRI and investigate
these discharges to identify potential data quality issues.
You can use the Loading Tool to review DMR loading calculation details, raw DMR data, and TRI
data in order to answer the following questions and identify potential data errors:
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•
•
•
•
•

Are the measurements used for loading calculation close to or below detection limits?
Are the loads based on daily maximum measurements?
Does the Loading Tool estimate loads for months where DMR data are missing?
Is TRI release based on the same measurement data that the facility uses for DMR reporting?
Is the TRI release calculated assuming a continuous or intermittent discharge?

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