Human Health Ambient Water Quality Criteria and Fish

Consumption Rates Frequently Asked Questions

Note the answers below reflect existing EPA policy and guidance as articulated in the 2000

Human Health Methodology

DISCLAIMER

These Frequently Asked Questions FAQs do not impose legally binding requirements on the

US Environmental Protection Agency EPA states tribes or the regulated community nor do

they confer legal rights or impose legal obligations upon any member of the public The Clean

Water Act CWA provisions and the EPA regulations described in this document contain legally

binding requirements These FAQs do not constitute a regulation nor do they change or

substitute for any CWA provision or the EPA regulations

The general description provided here may not apply to a particular situation based upon the

circumstances Interested parties are free to raise questions about the substance of these FAQs

and the appropriateness of their application to a particular situation The EPA retains the

discretion to adopt approaches on a case bycase basis that differ from those described in these

FAQs where appropriate These FAQs are a living document and may be revised periodically

without public notice The EPA welcomes public input on these FAQs at any time

Q1 What is the goal of the human health ambient water quality criteria

Clean Water Act CWA section 303 c2Arequires that water quality standards WQS

protect “public health or welfare enhance the quality of the water and serve the purposes of

the Act].” CWA section 101 a2 establishes as a national goal “water quality which provides

for protection and propagation of fish shellfish and wildlife and recreation in and on the

water wherever attainable.” EPA has interpreted the “fishable” language in section 101 a2 to

refer not only to protecting water quality so the fish and shellfish thrive but when caught they

can also be safely eaten by humans Thus to be consistent with section 101a2the applicable

criteria for such “fishable” designated uses must not only protect the aquatic organisms

themselves but also protect human health through consumption of fish and shellfish1

EPA’s recommended 304 a water quality criteria to protect these “fishable” designated uses

and accompanying risk assessment methodologies reflect the longstanding interpretation that

a designated use consistent with the goals of the Act means that State and Tribal waters should

support safe consumption of fish and shellfish EPA has consistently implemented the Clean

Water Act to ensure that the total rate of consumption of freshwater and estuarine fish and

shellfish including estuarine species harvested in near coastal waters reflects consumption

1 See memorandum from Geoffrey H Grubbs and Robert H Wayland October 2000 posted at

http water epa gov scitech swguidance standards upload 2000 1031standards shellfishpdf

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rates demonstrated by the population of concern In other words EPA expects that the

standards will be set to enable residents to safely consume from local waters the amount of fish

they would normallyconsume from all fresh and estuarine waters including estuarine species

harvested in near coastal waters EPA does not necessarily expect all consumers to eat only

fish from a single State but individuals or groups should be able to do so without concern for

their health It is also important to avoid any suppression effect that may occur when a fish

consumption rate fora given subpopulation reflects an artificially diminished level of

consumption from an appropriate baseline level of consumption for that subpopulation

because of a perception that fish are contaminated with pollutants

This approach is consistent with a principle that every State does its share to protect people

who consume fish and shellfish that originate from multiplejurisdictions In addition the goal

of water quality criteria for human health is to protect people from exposure to pollutants

through fish and water over a lifetime and the goal of a State's designated use should be that

the waters are safe to fish in the context of the total consumption pattern of its residents

Likewise because people are expected to continue consuming fish and shellfish throughout

their lifetime regardless of where they live and this consumption leads to similar exposure to

pollutants it is appropriate to derive protective human health criteria in State and Tribal water

quality standards assuming a lifetime of exposure

Although the human health ambient water quality criteria AWQC are based on chronic health

effects data both cancer and noncancer effects the criteria are intended to also be protective

against adverse effects that may reasonably be expected to occur as a result of elevated acute

or shortterm exposures That is through the use of conservative assumptions with respect to

both toxicity and exposure parameters the resulting AWQC should provide adequate

protection not only for the general population over a lifetime of exposure but also for special

subpopulations who because of high water or fish intake rates or because of biological

sensitivities have an increased risk of receiving a dose that would elicit adverse effects The

Agency recognizes that there may be some cases where the AWQC based on chronic toxicity

may not provide adequate protection for a subpopulation at special risk from shorter term

exposures The Agency encourages States Tribes and others employing the 2000 Human

Health Methodology to give consideration to such circumstances in deriving criteria to ensure

that adequate protection is afforded to all identifiable subpopulations

Q2 What does the fish consumption rate FCR indicate in the calculation for human health

ambient water quality criteria

The FCR indicates the amount of fish and shellfish in kilograms consumed by a person each day

For the purposes of human health ambient water quality criteria the fish and shellfish to be

reflected in the FCR include all of the fish and shellfish consumed that are species found in fresh

and estuarine waters including estuarine species harvested in near coastal waters Because

the overall goal of the criteria is to allow for a consumer to safely consume from local waters

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the amount of fish they would normally consume from all fresh and estuarine waters the FCR

does include fish and shellfish from local commercial aquaculture interstate and international

sources It is not necessary for the FCR to include fish and shellfish species designated as marine

species as that exposure is addressed by relative source contribution see question 4 formore

detail However partitioning of fish and shellfish into the different habitats in order to develop

a FCR can only be done where sufficient data are available for this to be done in a scientifically

defensible manner

For example if a State were to determine through scientifically collected data that its citizens

consumed 25 grams of fish and shellfish per day where 5 grams came from marine fish 5 grams

came from a local fresh water stream 5 grams came from a neighboring state’s fresh waters 5

grams came from international imports of estuarine shellfish and 5 grams came from

aquaculture of a freshwater species then the FCR would be 20 grams per day Only the marine

fish component would be excluded from the FCR see discussion below on relative source

contribution All of the other components represent the amount of fish and shellfish that could

be taken and consumed from local waters if the consumer chose to do so

Q3 How is the exposure to a pollutant due to marine fish consumption accounted for in the

human health ambient water quality criteria

Human health ambient water quality criteria are to account for all sources of exposure to the

pollutants for which they are developed The exposure to pollutants from marine fish and

shellfish species that are not included in the fish consumption rate should be accounted for in

the relative source contribution RSC when setting criteria for threshold noncarcinogens and

nonlinear carcinogens

Q4 What does the relative source contribution RSC indicate in the calculation for the

human health ambient water quality criteria

The relative source contribution component of the human health ambient water quality criteria

AWQC calculation for threshold noncarcinogens and non linear carcinogens allows a

percentage of the reference dose’s exposure to be attributed to ambient water and freshwater

and estuarine fish consumption including estuarine species harvested in near coastal waters

when there are other potential exposure sources The rationale for this approach is that for

pollutants exhibiting threshold effects the objective of the AWQC is to ensure that an

individual’s total exposure from all sources does not exceed that threshold level The RSC

includes but is not limited to exposure to a particular pollutant from marine fish consumption

not included in the fish consumption rate nonfish food consumption fruits vegetables and

grains dermal exposure and respiratory exposure

In the absence of scientific data the application of the EPA’s default value of 20 percent RSC in

calculating 304 a criteria or establishing State or Tribal water quality standards under Section

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303 c will ensure that the designated use for a water body is protected This 20 percent default

for RSC can only be replaced where sufficient data are available to develop a scientifically

defensible alternative value If appropriate scientific data demonstrating that other sources and

routes of exposure besides water and freshwater estuarine fish are not anticipated for the

pollutant in question then the RSC may be raised to the appropriate level based on the data

but not to exceed 80 percent The 80 percent ceiling accounts for the fact that some sources of

exposure may be unknown In cases where an 80 percent RSC is used 20 percent of the

exposure is reserved for unknown sources Although the 20 percent RSC has not been

consistently applied to national 304 a criteria recommendations for noncarcinogenic

pollutants where there are inconsistencies between the 2000 Human Health Methodology

recommendation and implementation in criteria the Human health Methodology should

prevail and the 20 percent RSC applied EPA is moving to complete implementation of this

guidance in existing 304 a criteria

Q5 Should an RSC also be applied to carcinogens

In the case of carcinogens based on linear lowdose extrapolation the AWQC is determined

with respect to the incremental lifetime risk posed by a substance’s presence in water and is

not being set with regard to an individual’s total risk from all sources of exposure Thus the

AWQC represents the water concentration that would be expected to increase an individual’s

lifetime risk of carcinogenicity from exposure to the particular pollutant by no more than one

chance in one million regardless of the additional lifetime cancer riskdue to exposure if any

to that particular substance from other sources For human health criteria this exposure

pathway considers consumption of freshwater and estuarine fish and shellfish as described in

the responses to Q1 and Q2 and drinking water ingestion EPA recommends that the

incremental cancer risk from these exposure pathways not exceed more than 1 in 1,000,000 or

1 in 100,000 for the general population nor exceed more than 1 in 10,000 for any sensitive sub

population such as those who may consume a great deal more fish because of a subsistence

lifestyle States and tribes may consider adjusting the risk level according to guidance in the

2000 Human Health Methodology and mentioned above particularly if exposure to “other”

sources besides water and fish is determined to be significant

Q6 Could a state include a component of marinefish consumption in their FCR forderiving

human health criteria

Yes a state may include consumption of marine species in the FCR Coastal States and

authorized Tribes that believe accounting for total fish consumption ie freshwater estuarine

and marine species is more appropriate for protecting the population of concern may do so In

the instance where the FCR includes freshwater estuarine and all marine fish consumption

EPA recommends that states adjust the RSC estimate to reflect a greater proportion of the

reference dose being attributed to water intake and the marineinclusive FCR exposures

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Including marine fish in the fish consumption rate may be particularly appropriate if a large

proportion of fish consumption for the population to be protected consists of marine fish such

as salmon and this exposure is clearly documented Including marine fish in the fish

consumption rate for criteria calculations would provide some calculations that are more

stringent than those that don’t include marine fish consumption particularly for chemicals that

are highly bioaccumulative

Q7 When fish consumption exposure is represented by a distribution of values what are the

appropriate percentiles to choose

In general EPA considers protection of the general population to be represented by the 90th

percentile of a total exposure distribution utilizing a “per capita” fish consumption distribution

If present in the state subsistence fishers should be considered on a site specific basis EPA has

recommended the 99th percentile of a per capita fish consumption distribution as a surrogate

for subsistence fishers which corresponded to a range of average consumption estimates from

actual surveys for subsistence fishers An analysis of protectiveness of the criteria for the

general population recreational fishers and subsistence fishers should be included in the

criteria documentation

January 18 2013

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