EPA-Expo-Box (A Toolbox for Exposure Assessors)
- Fate & Transport
- Calculation Tools
To estimate human exposure to contaminants in aquatic biota, exposure factor information is needed. Exposure factors are human behaviors and characteristics that help determine an individual's exposure to an agent. Data on fish and shellfish ingestion rates are available in Chapter 10 of EPA’s Exposure Factors Handbook: 2011 Edition . Intake rates are provided in units of g/day or g/kg-day (normalized to body weight). Many of the study-specific intake rate summaries reflect the distribution in the target population, so mean, median, and other percentiles intake rates are often presented.
At the beginning of Chapter 10, recommended values for fish intake are summarized for the general population and recreational marine anglers. Recommended values are not provided for recreational freshwater anglers or Native American fishers because intake data are limited to specific geographic areas for these receptor groups; however, data from relevant studies are presented. Intake rate recommendations for the general population are reported as uncooked fish weights because contaminant concentrations in fish are typically measured in uncooked fish. Chapter 10 also provides “as-prepared” (i.e., as-consumed) consumption rates for the general population in cases where concentration data are adjusted to account for changes after cooking.
Intake rates are provided as per capita or consumer-only data. Consumer-only rates are intake rates pertaining only to those individuals who reported eating the foods during the surveyed period. Per capita rates are defined as rates pertaining to the whole study population, and include both individuals who ingested the food during the survey period and individuals who did not. Per capita intake rates may be used in exposure assessments of the general population for which average dose estimates are of interest. Consumer-only intake rates are more pertinent for assessing specific more vulnerable populations (e.g., subsistence fishers).
The abundance of data in Chapter 10 reflects the variation in consumption rates that are available from relevant studies. Intake rates in Chapter 10 are organized based on the following distinctions.
- Species category. The focus of Chapter 10 is on fish—specifically, finfish and shellfish—however the studies considered and data presented are not limited to these groups; intake values are also provided for seafood (which include finfish and shellfish, but also might include biota such as eel or squid); other defined groups of species (e.g., anadromous, pelagic, bottom fish); and a wide range of individual species.
- Acquisition method. In some cases, intake rates are identified based on whether the fish was purchased or self-caught.
- Characteristics of the survey population. Because intake rates can vary across different receptor groups, rates are presented for the general population, recreational anglers, and Native American fishers and have also been described for characteristics of the individual, including:
- Age (infant, child, adult, and older adult age groups) or life stage (e.g., pregnant or lactating woman, woman of childbearing age)
- Health status (e.g., asthma, angina, cigarette smoking, alcohol consumption). Individuals with pre-existing conditions could be more susceptible to the contaminants they consume in fish.
- Type of water body. Some intake rates are provided for species obtained from marine waters, freshwater/estuarine waters, or the combined habitats.
- Sociodemographic variables. Some intake rates are summarized by race/ethnicity, education level, income level, and similar variables. Specific racial, ethnic, and socioeconomic groups might be disproportionately exposed to certain chemicals due to differences in diets and cultural activities.
- Spatial/temporal factors. Intake rates are often defined for specific geographic regions (particularly for recreational anglers and Native Americans), and also consider urban v. rural locations, day of the week, and season.
Selection of intake rates considering the appropriate category (or categories) above will be dictated by the exposure scenario being evaluated. In addition to intake rates, studies that describe serving size, fish parameter values (fish weight, fat content, moisture content), and the percent use of particular fish preparation/cooking methods are provided.
Other exposure factors that might be needed for assessing ingestion exposures include:
- Body weight (Chapter 8)
- Life expectancy values, specifically when evaluating cancer risk (Chapter 18)
Exposure factor data may be accessed from the Exposure Factors Tab of the Indirect Estimation Module.