Contact an expert who can comment on the study
The complete study
Summary of the study
Consumption recommendation data at a glance
Frequently asked questions and answers about the new study
What can consumers do to limit their exposure?
Some of the contaminants found in farmed salmon
How the study's farmed salmon consumption recommendations were determined
Background information about world salmon production and consumption
Several small, peer-reviewed pilot studies on farmed salmon
About the study's authors
EPA's Fish Consumption Advisories and the Study’s "Meals per Month" Recommendations
The study examines cancer risk from consuming toxic chemicals in farm raised and wild salmon. Health risks, including cancer risks, represent a combination of toxicity (the potency of a particular chemical) and exposure (the amount of a chemical that a person is exposed to over a certain period of time).
Cancer risk accumulates over a person’s lifetime. How much cancer risk is too much? In general, the goal of many government regulations is to keep cancer risk for individuals lower than one in one million. For example, the goal of the federal Clean Air Act is to keep the probability of getting cancer from breathing or coming into contact with a regulated cancer-causing pollutant to just one in one million more than it would otherwise be in daily life. As a practical matter, many agencies become concerned when a cancer risk exceeds 10 in one million, or one in 100,000.
Setting Regulatory Daily Limits
Cancer toxicity for a given substance may be calculated from animal studies or observations of human exposure - usually inadvertent or workers’ exposures. These are used to calculate an intake level that results in a lifetime cancer risk of less than one in 100,000. Some regulatory agencies may set an acceptable intake at other levels of risk. Note that to do the intake calculations, one must make a few assumptions. In the U.S., for example, the EPA assumes that adults are being exposed.
Setting "Fish Meals per Month" Limits
The U.S. EPA has taken the relationship between the dose and carcinogenicity of a variety of substances found in fish and calculated fish consumption recommendations for fish caught in the wild. The recommendation is for the number of meals an individual should not exceed in a month in order not to exceed an added cancer risk of one in 100,000 for these substances over a range of concentrations. A meal is defined as an eight-ounce portion of fish, and the number of meals per month applies to an adult consuming fish over a 70 year period.
For example, the EPA monthly fish consumption recommendation for dieldrin shows that one meal per month should be consumed if the dieldrin concentration is between 0.0029 and 0.0059 parts per million. If the dieldrin concentration is between 0.00018 and 0.00037 parts per million, then 16 meals per month can be safely consumed.
Applying the Study’s Findings to EPA Consumption Recommendations
For this study, once the levels of PCBs, toxaphene, and dieldrin were measured in farmed and wild salmon, it was a simple matter to use the EPA’s consumption limits to calculate the number of meals per month that could be consumed and still remain below the one in 100,000 risk.
Although dioxins, the fourth substance measured in this study, also have an EPA fish consumption advisory, the agency is in the process of reassessing its dioxin data.
Why Doesn’t the Study Use FDA Limits?
The authors used U.S. EPA fish consumption guidance governing locally caught fish rather than U.S. Food and Drug Administration (FDA) standards governing commercially sold fish because the authors were interested in performing a health-based study and arriving at meaningful conclusions about the true health risks of consuming farmed salmon. While EPA methods take only human health risks into account, FDA is required to consider a range of factors, including effects on the food production system, when it sets its standards. Moreover, FDA doesn’t have standards for several substances found in fish. Its standards for PCBs and dieldrin were set more than 25 years ago and do not reflect the latest scientific and diet information. Both EPA and FDA agree that the FDA levels are inappropriate for setting fish consumption advisories (see last paragraph on p. 1-5 in EPA National Guidance for Fish Advisories), and EPA’s approach has been accepted by many states.