Human Health Ambient Water Quality 

Criteria: 2015 Update

Office of Water

EPA 820-F-15-001

June 2015

Summary

EPA published final updated ambient water quality 

criteria for the protection of human health for 94 

chemical pollutants. These updated 

recommendations reflect the latest scientific 

information and EPA policies, including updated 

body weight, drinking water consumption rate, fish 

consumption rate, bioaccumulation factors, health

toxicity values, and relative source contributions. 

EPA accepted written scientific views from the public 

from May to August 2014 on the draft updated 

human health criteria and has published responses 

to those comments. EPA water quality criteria serve 

as recommendations to states and tribes authorized 

to establish water quality standards under the Clean 

Water Act.

Background

Ambient water quality criteria developed by EPA 

under Clean Water Act section 304(a) represent 

specific levels of chemicals or conditions in a water 

body that are not expected to cause adverse effects 

to human health. EPA is required to develop and 

publish water quality criteria that reflect the latest 

scientific knowledge. These criteria are not rules, nor 

do they automatically become part of a state’s water 

quality standards. States may adopt the criteria that 

EPA publishes, modify EPA’s criteria to reflect sitespecific conditions, or adopt different criteria based 

on other scientifically-defensible methods. EPA 

must, however, approve any new water quality 

standards adopted by a state before they can be 

used for Clean Water Act purposes.

In this 2015 update, EPA revised 94 of the existing 

human health criteria to reflect the latest scientific 

information, including updated exposure factors 

(body weight, drinking water consumption rates, fish 

consumption rate), bioaccumulation factors, and 

toxicity factors (reference dose, cancer slope factor). 

The criteria have also been updated to follow the 

current EPA methodology for deriving human health 

criteria (USEPA 2000). EPA also developed chemicalspecific science documents for each of the 94 

chemical pollutants. The science documents detail 

the latest scientific information supporting the 

updated final human health criteria, particularly the 

updated toxicity and exposure input values. Specific 

updates are described below.

Due to outstanding technical issues, EPA did not 

update human health criteria for the following 

chemical pollutants at this time: antimony, arsenic, 

asbestos, barium, beryllium, cadmium, chromium (III 

or VI), copper, manganese, methylmercury, nickel, 

nitrates, nitrosamines, N-nitrosodibutylamine, 

N-nitrosodiethylamine, N-nitrosopyrrolidine, 

N-nitrosodimethylamine, N-nitrosodi-n-propylamine, 

N-nitrosodiphenylamine, polychlorinated biphenyls 

(PCBs), selenium, thallium, zinc, or 2,3,7,8-TCDD 

(dioxin).

It is important for states and authorized tribes to 

consider any new or updated section 304(a) criteria 

as part of their triennial review to ensure that state 

or tribal water quality standards reflect current 

science and protect applicable designated uses. EPA 

recently proposed revisions to its water quality 
standards regulations that would, if finalized without 

substantive change, require states during their 

triennial reviews to consider new or updated section 

304(a) recommended criteria and, if they do not 

adopt new or revised criteria for such pollutants, 

provide an explanation to EPA as to why the state 

did not do so. These final updated human health 

criteria recommendations supersede EPA’s previous 

recommendations.

Updated Exposure Inputs

Body Weight

EPA updated the default body weight for human 

health criteria to 80 kilograms based on National 

Health and Nutrition Examination Survey (NHANES) 

data from 1999 to 2006 (USEPA 2011). This 

represents the mean body weight for adults ages 21 

and older. EPA’s previously recommended default 

body weight was 70 kilograms, which was based on 

the mean body weight of adults from the NHANES III 

database (1988-1994).

Drinking Water

EPA updated the default drinking water 

consumption rate to 2.4 liters per day based on 

NHANES data from 2003 to 2006 (USEPA 2011). This 

represents the per capita estimate of community 

water ingestion at the 90th percentile for adults ages 

21 and older. EPA previously recommended a 

default drinking water consumption rate of 2 liters 

per day, which represented the per capita 

community water ingestion rate at the 86th 

percentile for adults surveyed in the US Department 

of Agriculture’s 1994-1996 Continuing Survey of 

Food Intake by Individuals (CSFII) analysis and the 

88th percentile of adults in the National Cancer 

Institute study of the 1977-1978 Nationwide Food 

Consumption Survey.

Fish Consumption

EPA updated the default fish consumption rate to 

22 grams per day. This rate represents the 90th 

percentile consumption rate of fish and shellfish 

from inland and nearshore waters for the U.S. adult 

population 21 years of age and older, based on 

NHANES data from 2003 to 2010 (USEPA 2014). 

EPA’s previously recommended rate of 17.5 grams 

per day was based on the 90th percentile 

consumption rate of fish and shellfish from inland 

and nearshore waters for the U.S. adult population 

and was derived from 1994-1996 CSFII data.

As described in EPA’s human health criteria 

methodology (USEPA 2000), the level of fish 

consumption in highly exposed populations varies by 

geographical location. Therefore, EPA suggests a 

four preference hierarchy for states and authorized 

tribes that encourages use of the best local, state, or 

regional data available to derive fish consumption 

rates. EPA recommends that states and authorized 

tribes consider developing criteria to protect highly 

exposed population groups and use local or regional 

data in place of a default value as more representative

of their target population group(s). The preferred 

hierarchy is: (1) use of local data; (2) use of data 

reflecting similar geography/ population groups; 

(3) use of data from national surveys; and (4) use of 

EPA’s default consumption rates.

Bioaccumulation Factors

EPA’s methodology for deriving human health 

criteria emphasizes using, when possible, measured 

or estimated bioaccumulation factors (BAFs), which 

account for chemical accumulation in aquatic 

organisms from all potential exposure routes (USEPA 

2000). Unlike bioconcentration factors, BAFs account 

for more exposure pathways than direct water 

contact. As a result, the updated criteria will better 

represent exposures to pollutants that affect human 

health. In order to account for the variation in 

bioaccumulation that is due to trophic position of 

the organism, EPA’s methodology (USEPA 2000) 

recommends that BAFs be determined and applied 

to three trophic levels of fish.

EPA selected BAFs using a framework for deriving 

national trophic level-specific BAFs (USEPA 2000; 

USEPA 2003). EPA used field-measured BAFs and 

laboratory-measured bioconcentration factors 

available from peer-reviewed, publicly available 

databases to develop national BAFs. If this 

information was not available, EPA selected octanolwater partition coefficients (Kow values) from peerreviewed sources for use in calculating national 

BAFs. As an additional line of evidence, EPA reported

model-estimated BAFs for every chemical based on
the Estimation Program Interface (EPI) Suite (USEPA 

2012) to support the field-measured or predicted 

BAFs.

Updated Health Toxicity Values

EPA considered all available toxicity values for both 

noncarcinogenic and carcinogenic toxicological 

effects to develop the updated human health 

criteria. EPA's Integrated Risk Information System 

(IRIS) was the primary source for reference dose and 

cancer slope factors for this update. For some 

pollutants, however, more recent toxicity 

assessments were provided by EPA's Office of Water, 

EPA's Office of Pesticide Programs, and international 

or state agencies. EPA followed a systematic process 

to search for and select the toxicity values used to 

derive the final updated human health criteria for

noncarcinogenic and carcinogenic effects. 

Relative Source Contribution

EPA updated the human health criteria to reflect 

chemical-specific relative source contributions (RSC) 

ranging from 20 to 80 percent following the 

Exposure Decision Tree approach described in EPA’s 

methodology (USEPA 2000). EPA recommends 

inclusion of an RSC when developing human health 

criteria for threshold non-carcinogens or non-linear 

carcinogens. The RSC allows a percentage of the 

reference dose’s exposure to be attributed to 

ambient water and fish consumption (including fish 

and shellfish from inland and nearshore waters) 

when there are other potential exposure sources. 

The rationale for this approach is that the objective 

of the water quality criteria is to ensure that an 

individual’s total exposure from all sources does not 

exceed the criteria. Exposures outside of the RSC 

include, but are not limited to, exposure to a 

particular pollutant from ocean fish consumption 

(not included in the fish consumption rate), non-fish 

food consumption (meats, poultry, fruits, 

vegetables, and grains), dermal exposure, and 

respiratory exposure.

Where can I find more information?

To access the Federal Register notice, the final 

updated criteria, and supporting documents visit

EPA’s National Recommended Human Health 

Criteria website at: 

http://water.epa.gov/scitech/swguidance/standards

/criteria/health/.

References

USEPA. 2000. Methodology for Deriving Ambient 

Water Quality Criteria for the Protection of Human 

Health (2000). EPA-822-B-00-004. U.S. 

Environmental Protection Agency, Office of Water, 

Office of Science and Technology, Washington, DC. 

Accessed February 2015. 

http://water.epa.gov/scitech/swguidance/standards/

upload/2005_05_06_criteria_humanhealth_method_

complete.pdf. 

USEPA. 2003. Methodology for Deriving Ambient 

Water Quality Criteria for the Protection of Human 

Health (2000), Technical Support Document. Vol. 2, 

Development of National Bioaccumulation Factors. 

EPA-822-R-03-030. U.S. Environmental Protection 

Agency, Office of Water, Office of Science and 

Technology, Washington, DC. Accessed March 2015. 

http://www.epa.gov/scipoly/sap/meetings/2008/oct

ober/methodology.pdf. 

USEPA. 2011. Exposure Factors Handbook: 2011 

Edition. EPA-600-R-09-052F. U.S. Environmental 

Protection Agency, Office of Research and 

Development, Washington, DC. Accessed February 

2015. http://www.epa.gov/ncea/efh/pdfs/efhcomplete.pdf. 

USEPA. 2012. Estimation Programs Interface (EPI) 

SuiteTM for Microsoft® Windows, v 4.10. U.S. 

Environmental Protection Agency, Office of Pollution 

Prevention and Toxics, Washington, DC. Accessed 

February 2015. 

http://www.epa.gov/oppt/exposure/pubs/episuite.

htm. 

USEPA. 2014. Estimated Fish Consumption Rates for 

the U.S. Population and Selected Subpopulations 

(NHANES 2003-2010). EPA-820-R-14-002. U.S. 

Environmental Protection Agency, Office of Water, 

Washington, DC. Accessed February 2015. 

http://water.epa.gov/scitech/swguidance/fishshellfi

sh/fishadvisories/upload/Estimated-FishConsumption-Rates-for-the-U-S-Population-andSelected-Subpopulations-NHANES-2003-2010.pdf.