Ferriss et al. recently found that exposure to the naturally produced neurotoxin domoic acid (DA) through the recreational razor clam (Siliqua patula) fishery in Washington State may be larger than previously thought. DA is a neurotoxin naturally produced by phytoplankton and that accumulates in seafood during harmful algal blooms. As the prevalence of DA increases in the marine environment, there is a critical need for better data to assess potential risks to human health through DA exposure. During the Winter 2015 and Spring 2016 clamming seasons we distributed surveys to recreational harvesters to determine razor clam consumption in this population. Combining this consumption data with actual DA measurements in razor clams measured by the state monitoring program we estimated the amount of DA a person would consume if they harvested and ate razor clams from the Washington Coast. Human exposure to DA was well within the regulatory limits for the majority of recreational clam harvesters. However, approximately seven percent of total acute exposures (exposures after a single meal of clams) calculated exceeded the level advised in current regulations, In addition, three percent of survey respondents were potentially at risk of chronic DA exposure defined as consuming a minimum of 15 clams per month for 12 consecutive months. This study contributed to the development of a razor clam consumption advisory in Washington State for chronic exposure and identified demographics of recreational clam harvesters who may be at risk of acute DA exposure. Although DA monitoring has prevented acute toxic events, these data point to the need to better understand the potential for more subtle effects of DA exposure on human health to better manage potential public health risks associated with seafood consumption.

Figure 1. Weekly mean domoic acid (DA) levels in razor clams from March 23 to May 7, 2015 (A) and corresponding weekly mean DA exposure (mg DA·kg bodyweight-1·d-1) for recreational harvesters from the last week in March to the first week in May, 2015 (B). DA exposures are aggregated by age and gender. Colors represent four age groups of 10-20 years (light gray), 21-40 years (dark gray), 41-60 years (white), and 61+ years (medium gray), and pattern represents gender (female = solid, male = hatched). The dashed line in the lower panel represents the acute reference dose (ARfD) of 0.075 mg DA·kg bodyweight-1·d-1 that was used to set the legal limit for DA levels in razor clams of 20 mg·kg-1 fresh weight of whole tissue. The error bars represent exposure calculated using DA levels one standard error above/below the mean and consumption rates one standard error above/below the mean.