Fish Consumption Advice for Alaskans
DPH takes several steps to analyze the fish contaminant data and develop public health advice. First, the data are screened against EPA Risk-Based Consumption Limit Tables provided in Volume 2 of their guidance. For organic contaminants, DPH generally uses the screening criteria for non-cancer health endpoints rather than cancer health endpoints, because the chronic endpoint risk assessment often is more scientifically defensible. Animal cancer studies usually involve administration of high doses of the test chemical, which may involve mechanisms and risks not associated with lower doses, such as compensatory mitogenesis following tissue damage.6 This mechanism of toxicity would not apply to chronic low-dose exposures, such as exposures from consuming fish from Alaska. 5
Use of cancer endpoints may overestimate true risks because EPA uses a conservative method to calculate the risks posed by environmental carcinogens. Their approach assumes that no threshold exists below which an increased cancer risk does not occur. Extrapolation of effects from high-dose laboratory studies to low environmental levels is based on a linearized multistage no-threshold model. Numerous authors have criticized this approach as being unrealistically conservative, since it does not take into account evidence of thresholds for carcinogenic endpoints, particularly for chemicals such as PCBs and dioxins that act through a promotion mechanism.7-10 Using PCBs as an example, EPA has adopted a high risk and persistence upper- bound slope factor of 2.0 per (mg/kg)/day for PCBs as carcinogens.11 EPA concedes that this slope factor drives a currently recommended seafood screening value for PCBs that “will result in widespread exceedance in waterbodies throughout the country and will drive virtually all fish and shellfish contaminant monitoring programs into the risk assessment phase for PCBs.” 12
If a mean chemical concentration for a fish species exceeds the EPA screening value for unlimited consumption (defined as over 16 meals per month), DPH considers the risk in greater detail. This includes an examination of the evidence behind health-based risk values, the magnitude of safety factors that have been incorporated, and a consideration of the health benefits of fish consumption.
Before 2006, insufficient fish data were available to justify the need to issue restrictive fish consumption recommendations in Alaska. ADEC’s website provides earlier reports that detail the contaminant data for fish from Alaska, and the public health interpretation of the data. 13
In the summer and fall of 2006, ADEC provided a large body of additional data to DPH, describing the mercury content of over 2,300 individual fish from 23 species. Several species had mercury content of potential concern, prompting DPH to implement EPA’s risk management principles.14 As part of this process, ADEC and DPH assembled a committee of scientific experts from Alaska to participate in the risk management process. This committee became known as the Alaska Scientific Advisory Committee for Fish Consumption.
The Alaska Scientific Advisory Committee for Fish Consumption met on November 30, 2006, and agreed that a few Alaska fish species had mercury levels too high to warrant “unrestricted consumption” guidance for the most sensitive members of the population, specifically women who are or can become pregnant, nursing mothers, and young children. After considering the risks of mercury exposure, and the multiple benefits of fish consumption, the committee reached consensus on a strategy to provide balanced, yet protective, fish consumption advice.
Following the committee meeting, ADEC and DPH conducted a series of meetings and workshops with various stakeholders to obtain input. A list of these meetings is presented in Table 1.