Description:
Background: Shellfish have the capacity to accumulate chemical contaminants found in their biotope and therefore present a potential risk for consumers. The Department of Health is conducting a study to assess the chemical risks associated with consumption of shellfish harvested in Oakland Bay, Washington. Oakland Bay is one of the most productive commercial shellfish growing areas in the country. In 2008, the Washington State Department of Ecology (Ecology) conducted a sediment investigation of Oakland Bay by collecting surface sediment samples in the Shelton Harbor and Oakland Bay area. Ecology quantified inorganic and organic compounds. Dioxins were the only chemicals detected above Ecology’s sediment quality standard. The levels of dioxin in the sediment ranged from 4.4 to 54 parts per trillion (ppt) in Oakland Bay and 1 to 175 ppt in Shelton Harbor.
Issue: This initial sediment characterization indicated the need to conduct more sampling to address consumer health concerns regarding potential contaminants in shellfish. Manila clams, oysters and mussels were collected and analyzed for dioxin. The cancer and noncancer risks for three consumption scenarios (tribal population, general population, and recreational consumers) had to be evaluated for this site.
Results: The results of this study (available August 2009) will indicate whether the presence of dioxin levels are associated with intakes that exceed the main exposure limit recommendations proposed to prevent noncancer and/or cancer effects.
Lessons Learned: Several limits must be considered (body weight, sample size, exposure limits, consumption rates, etc) before drawing conclusions about the relative safety of shellfish consumption regarding this end point. For example, there is uncertainty regarding dioxin intake associated with the various consumption scenarios. |