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FISH

Executive Summary
Publishing of the Final Report Chemicals in Fish: Consumption of Fish and Shellfish in California and the United States
[11/09/01]

Fishing and fish consumption provide recreational, cultural, and nutritional benefits to fishers and their families. However, because many water bodies and the fish that inhabit them contain chemical contaminants, human consumption of fish and shellfish poses a potential health risk. The magnitude of the risk depends on the amount of fish consumed and the degree of contamination. Evaluation of the potential risks to populations that may be exposed to chemically contaminated fish and/or shellfish requires knowledge of the patterns and rates of fish consumption by these populations. Additionally, fish consumption rates are considered in the development of water quality criteria. Therefore, representative estimates of fish consumption rates are fundamental to agencies and programs that have responsibilities in the protection of human health and aquatic resources.

In order to characterize human exposure to contaminated fish and shellfish, the potentially exposed population must be identified, and the likely types and quantities of fish and shellfish consumed must be determined. Historically, a variety of fish and shellfish consumption rates have been reported and used by different researchers and agencies. However, the default consumption rates that have been proposed may not be representative of the fish-consuming populations for which exposure assessments or other evaluations are being done. Additionally, data that describe local consumption patterns and population characteristics for the population of concern may not be available or feasible to collect. Thus, exposure assessments often have to rely on rates reported in existing studies conducted in other regions and/or for other purposes. Estimates of consumption rates that describe fish and shellfish consumption for a particular population(s) of concern must be derived from the most reliable studies and from those that are most applicable to the population(s) of interest.

When selecting the most appropriate estimates of fish and shellfish consumption, it is essential to identify the context in which the estimated fish consumption rates will be used. In particular, one needs to clearly define the population of concern or "target population." In order to characterize potential risks to public health from consuming contaminated fish and/or shellfish, consumption studies that represent people who actually consume fish and/or shellfish should be used to derive consumption rates for risk assessments where fish consumption is a major exposure pathway and risk factor. Where fish consumption is a minor pathway, as in multipathway assessments for general population exposures, studies that include a broader population (e.g., including infrequent consumers) are more representative of the general population target. The selection of consumption studies and rates to develop water quality criteria must be flexible so that criteria can be targeted to protect different populations. For some chemicals, some regions, and some populations, fish consumption is a major exposure pathway, and for others, it is not. The United States Environmental Protection Agency (U.S. EPA)'s national water quality criteria are targeted at protecting the majority of the general population from chronic adverse health effects. Fish consumption rates from the upper percentiles of the national survey population are considered protective in this case. National general population studies also lend themselves to promoting national consistency where fish consumption is not a major exposure pathway and risk factor. In regions or populations where fish consumption is a major demonstrable exposure pathway, U.S. EPA has developed options for using regional or local consumption studies and fish consumption rates. U.S. EPA encourages states or tribal authorities to select the most appropriate data to adequately protect the most highly exposed population when developing state or local criteria. Alternatively, water quality criteria can be developed without the use of specific local data, but should be based on representative consumption rates such that the criteria will support consumption of fish from the water body at rates at which local users consume fish. In addition, assessors must consider the sources of contaminants for which exposure is being assessed. If the chemical(s) of concern is one with a global distribution, such as methylmercury, then estimates of total fish consumption from all sources, including commercial and sport fish, may be needed to fully evaluate the potential health risks from exposure to this chemical via ingestion of fish and/or shellfish.

In this report, broad definitions of "fish and shellfish" will be used. The term "seafood" is considered here to include any edible organism from any water body. It generally is synonymous with the phrase "fish and shellfish" which is used throughout the report to denote any type of edible aquatic animal, but not including marine mammals, amphibians, or reptiles. "Fish" includes any of various aquatic vertebrate animals having gills and commonly fins, including the bony fishes (those having bony skeletons) and more primitive forms with cartilaginous skeletons (such as sharks and rays). "Shellfish" includes any edible invertebrate animal usually belonging to one of the following taxonomic categories: 1) mollusks, including bivalves, gastropods, and cephalopods; 2) crustaceans; and 3) echinoderms. However, it should be noted that consistency among studies is lacking in terms of which types of seafood were actually included in the study. Therefore, estimates of consumption of fish and particularly shellfish across studies may not (and likely will not) include the same types of organisms.

Per capita consumption rates are estimates derived for the general population inclusive of both consumers and nonconsumers. Thus, per capita rates are primarily useful for trend analyses rather than representing actual consumption. Average per capita rates derived from national surveys for consumption of fish and shellfish by the general population ranged from 10 to 17.9 grams per day. Several analyses of data used to estimate per capita consumption of fish and shellfish found an increase of approximately 25 percent between 1970 and the early 1990's, indicating that the U.S. population as a whole consumed more fish in more recent years.

Consumption rates derived for consumers are preferable to per capita rates for use in describing actual consumption of fish and shellfish in the U.S. However, national data that apply to "consumers only" are limited in several ways. National surveys that have targeted the general U.S. population have determined "acute" consumption patterns for respondents reporting consumption of fish and/or shellfish during the short-term reporting period of the survey. Therefore, the results may not characterize long-term or "usual" consumption rates for consumers. National studies that have been conducted thus far were not designed to fully address consumption of sport fish and shellfish, and are designed to describe the health and diet of the general U.S. population. Therefore, the results of these national surveys are applicable mainly to consumption of commercial fish and shellfish by the general population and are less appropriate for characterizing consumption by fishers or other consumers of sport fish and shellfish.

Regional studies of sport fishing populations reviewed in this report reported overall mean rates for consumption of sport fish ranging from 12.3 to 63.2 grams per day. These studies can be used to derive estimates of sport fish and shellfish consumption for populations in regions where geographic and population characteristics are similar, provided that the limitations of a given study are considered. However, it should be noted that many of these regional studies were conducted at locations where consumption advisories were in place. It is recommended that a range or distribution of consumption rates be used to represent the population as a whole. At the minimum, a measure of central tendency (the median and/or mean values) can be applied if used in concert with an upper percentile rate. The overall mean rates for total fish consumption calculated from the studies that targeted fishing populations and reported on consumption of both sport and commercial fish and shellfish ranged from 16.1 to 61.3 grams per day. These studies indicated that sport fishers consumed commercially available species in addition to sport-caught fish and shellfish.

Consumption rates can vary among subpopulations by race or ethnicity, age, sex, income, fishing mode, region of the country, and other demographic variables. A number of studies have demonstrated trends in higher rates of fish consumption for certain racial or ethnic subpopulations. These studies showed that fish consumption rates were higher for some Asian populations, Blacks, Native Americans, and other minority groups. However, results from various studies are not consistent in the trends reported, and caution should be exercised in making assumptions about subpopulations. In particular, the way in which ethnic or other subgroups are defined can be crucial in shaping the results that are found. In general, however, higher-consuming ethnic subpopulations and other high-end consumers are likely to be represented by upper percentile consumption rates (such as the 95th percentile) derived from a distributional analysis of the data. Some studies also found differences in the patterns of fish consumption (e.g., eating different fish parts) and fishing behavior among subpopulations.

Studies that differentiated fish consumption rates (in grams per day) by age and sex showed that, generally, males consumed more than females did, and the amount of fish consumed increased with age. In many cases, although not all, these differences are likely to correspond to differences in body weight. Exposure assessments should consider body weight as a parameter and use sex and age-specific consumption rates, when available, or adjust for differences in body weight when evaluating subsets of the population. Additionally, there is limited evidence that some elderly fishers consume fish and/or shellfish at rates that exceed (by two to three times) the average for adult sport fish consumers. Although sufficient data may not be available for specific subpopulations of interest, higher consuming individuals and subgroups in the population are likely to be represented by the upper percentile consumption rates derived from a distributional analysis of the dataset (or from default distributions).

Difficulties in defining and evaluating subsistence fishers have resulted in limited information pertaining to consumption rates for subsistence populations. In addition, definitions of what constitutes "subsistence fishing" tend to differ by geographic region and be influenced by perceptions. A few datasets are currently available for sport fishing populations believed to represent or include subsistence fishers (e.g., Native Americans and low-income urban populations). For exposure assessments, use of an upper level intake rate (such as the 95th percentile) from distributions that include subsistence fishers would encompass consumption rates for individuals reporting above-average consumption within these populations and may be representative of consumption by subsistence fishers within these populations. However, in locations where exceptionally high consumption by subsistence populations, or other people, is expected, using data for the subpopulation of interest would be preferable to fully or to better characterize the population.

When fish consumption estimates are to be used to conduct exposure assessments for locally abundant pollutants only, where fish consumption is a major exposure pathway, consumption rates that are applicable to sport fish consumption from the affected water bodies should be used. The first choice for "applicable" consumption rates would be those derived from surveys of the water body in question. When studies from the water body in question are not available, the results of other well-conducted studies deemed appropriate for application to the population at risk and/or water body of concern can be used. Additionally, in order to characterize potential risks to public health from consuming contaminated fish and/or shellfish, consumption rates that apply to people who actually consume sport fish and/or shellfish, rather than per capita estimates, should be used.

In some circumstances, estimates of consumption of fish and/or shellfish from all sources may be appropriate. For example, if a risk assessment is conducted to evaluate exposure to a chemical(s) of concern with a global distribution, such as methylmercury, then rates for total fish consumption from all sources, including commercial and sport fish, may be relevant for evaluating total exposure to the chemical of concern. In addition, for multipathway exposure assessments, it may be appropriate to apply fish consumption estimates that represent individuals who consume sport fish less frequently, or not at all, as well as those who are frequent consumers. High-end rates (e.g., an upper bound consumption rate) from such studies would be protective of the majority of the population.

Estimates of consumption of fish and shellfish derived from consumption studies are useful for risk assessment, and locally applicable data can enhance exposure assessment for local populations. However, estimates of consumption are not critical or necessarily applicable to the development of the recommended guidelines included in fish consumption advisories. Estimates of the rates of consumption by the population using a water body for which an advisory has been developed can be compared to the recommended guidelines, but are not needed to determine acceptable or safe levels of consumption.

The selection of consumption studies and consumption rates to develop water quality criteria is a special situation. In this case, the rates are not used to assess risk but to set limits to prevent the potential for excess risk developing. Selection of consumption rates in these cases must be flexible so that criteria can be targeted to protect different populations. U.S. EPA's national water quality criteria are aimed at protecting the majority of the general population from chronic adverse health effects. National consumption studies and high-end consumption rates from such studies of the entire general population (consumers and nonconsumers) are considered protective in this case. These studies and consumption rates, however, may not be protective of state or local target populations. U.S. EPA has developed a series of preferences for states selecting consumption rates to use to develop water quality criteria. The preferred option for states is to use regional or local consumption studies and consumption rates to adequately protect the most highly exposed population when developing state or local criteria.

The Santa Monica Bay Seafood Consumption Study provides the best available dataset for estimating consumption of sport fish and shellfish in California. This study provided a distribution of consumption rates for the population that regularly fishes and consumes fish and shellfish from Santa Monica Bay, and reflects the range of values and the variability within the population. Consumption of sport fish and/or shellfish by populations in California can be described either by using the full distribution in a stochastic analysis or by using, at a minimum, a measure of central tendency (the median or mean) in concert with an upper percentile intake rate from this distribution. Although this study was conducted on a population fishing from a marine water body, a similar distribution of consumption rates was determined from data on a population fishing from fresh water bodies. Thus, the default values derived from the Santa Monica Bay study can reasonably be applied to fishers using any productive water body in the state. Until reliable data become available which describe consumption of freshwater sport fish in California, it is recommended that the rounded unadjusted values from the Santa Monica Bay study of 21 grams per day for the median, 50 grams per day for the mean, 107 grams per day for the 90th percentile, and 161 grams per day for the 95th percentile rate be used to estimate consumption from both marine and freshwater sources of sport fish and shellfish in California. These values are most applicable to fishers that consume sport fish and shellfish on a regular and frequent basis (i.e., at least once a month). For cases where the target population is the general fishing population and fish is not a major exposure pathway, the adjusted (weighted) results of 30.5 grams per day for the mean value and 85.2 grams per day at the 95th percentile can be used.

Other available data from the studies reviewed suggest that consumption rates for sport-caught marine and estuarine fish tend to be comparable to those for sport-caught freshwater fish. Additional data may be useful to evaluate the potential for differences in consumption of fish obtained from water bodies in specific regions of the U.S. where variables such as access, availability, and productivity of fish and/or shellfish may differ substantially. However, in general, for exposure assessments in which potential risks to consumers from consumption of sport-caught fish from productive water bodies are to be evaluated, the available data do not support using different rates of consumption for fish obtained from marine and fresh water bodies based solely on salinity type.

Studies that specifically address consumption rates for commercial fish and shellfish in California are lacking, although several analyses of national data have indicated that people in the Pacific region consumed slightly more, on average (and per capita), than the overall U.S. population. Therefore, national estimates for consumption of commercial species can be used to approximate consumption by the general population in California that consumes only commercial species. However, studies which address "usual" (versus short-term) intake are needed to more accurately estimate typical rates of consumption of commercial seafood. Additionally, several studies have indicated that total fish consumption by fishers is greater than sport fish consumption (fishers supplement their catch with commercially available species). Therefore, estimates for sport fish consumers should be increased to account for supplemental consumption of commercial species, or total consumption, by sport fishing populations in California. Limited data from the studies reviewed suggested that the difference in amount between sport and total consumption ranged from approximately 8 to 42 grams per day. The proportion of sport and commercial fish and shellfish in the diet may also be influenced by the presence of consumption advisories for fish obtained from local water bodies.

Data are generally unavailable to estimate consumption rates for shellfish, although several studies have shown that shellfish and other invertebrate species were among the most commonly caught species by sport fishers, particularly in certain areas including the Pacific region. In the absence of reliable data on shellfish consumption in California, the rates derived for sport fish consumption by fishing populations in California can reasonably be applied to consumption of shellfish species by those people who catch shellfish as opposed to finfish.

Although reliable estimates of portion size are essential to deriving accurate estimates of consumption rates, data on actual meal size are limited. Assumptions about portion sizes are inconsistent among fish and shellfish consumption studies, but typically ranged from four to eight ounces of fish and/or shellfish per meal. Actual mean meal or portion sizes, when reported, usually ranged from four to eight ounces. Differences in the reporting of raw versus cooked weights, the parts of fish consumed, and methods of preparation can affect the accuracy of estimates of consumption rates that are used in risk assessment or in the development of advisories or water quality criteria. Differences in the ways portion sizes were estimated in surveys may also have a significant impact on the resulting estimates of consumption. U.S. EPA (2000a) suggested that a default value of eight ounces (227 grams) of uncooked fish fillet be used as an average meal size for the general adult population (for a 72-kilogram person) for exposure assessments and fish advisories if population-specific data are not available.

Distributional analyses rather than single point estimates of fish consumption rates are preferred to describe exposure within a population. Using a stochastic analysis will allow a better characterization of consumption in a population and the variability within that population. Each value in a distribution represents a different point in the distribution and, therefore, a different segment of the population. Selection of one over another of these values (i.e., a single point estimate) should only be done when the single value, and what it represents, is appropriate to the question at hand or intended use of the consumption rate estimate. At a minimum, a measure of central tendency (the median or mean) should be selected to represent an average level of consumption in a given population, and should be used in concert with an upper percentile rate of intake derived from a distributional analysis to represent a higher level of consumption, or exposure, in the population.

Studies on fish and shellfish consumption continue to be performed and released. Therefore, review of the fish consumption literature is an ongoing process, but in order to finalize this report, it was necessary to exclude newer work on the subject. Nevertheless, new information that is pertinent should be considered along with this report, as it becomes available.

Follow this link to download the report as a PDF file. (best option if you will want to print the report) (625 KB file size)