Arsenic in Oregon clams triggers consumption advisory

Softshell clams along the entire Oregon coast contain elevated levels of arsenic, and clammers should permanently limit how many they eat, the Oregon Health Authority plans to announce July 15.

The state health agency sent an email to coastal health and government officials just before the July 4 holiday weekend alerting them to the pending advisory and asking them to keep the information under wraps.

But several have refused, saying the public deserves to know right away.

"I think anything that comes from a public organization with information that has an advisory certainly should be released to the public as soon as it's been vetted," said Michael McNickle, environmental health director at the Clatsop County Health Department.

McNickle said he directed the information to be posted publicly on the department's web site as soon as Friday, when a regular weekly newsletter comes out.

The state Department of Environmental Quality found elevated arsenic levels in samples of softshell clams taken in 2013 as part of its water quality toxics monitoring program.

OHA received the results in March of this year and confirmed them with follow-up sampling conducted in April, spokesman Jonathan Modie said in an email. It received those results in May and finished its analysis of health risks in June.

Modie declined to release details about the arsenic levels or the pending advisory.

But the Statesman Journal obtained documents — a technical advisory and a Q & A — outlining both.

They show that levels of inorganic arsenic over the U.S. Environmental Protection Agency screening level of 0.7 milligram per kilogram of tissue were found in whole softshell clams, also known as steamers, from areas along the whole coast.

Levels in the North Coast were highest, with an average of 4.87 mg/kg. The Mid-Coast followed at an average of 1.39 mg/kg, and the South Coast had the least, at 0.77 mg/kg.

The documents show that the arsenic is concentrated in the clams' siphon sheaths, which usually are removed before cooking.

Without the siphon sheaths, levels averaged 0.26 mg/kg on the North Coast, 0.11 mg/kg on the Mid-Coast, and 0.084 on the South Coast.

OHA will recommend limiting consumption, depending upon where they were harvested, to between one and four meals per month for whole clams, and between 11 and 33 meals per month for clams from which the siphon sheaths have been removed, the documents show.

A meal ranges from ¼ cup for a toddler to one cup for an adult.

DEQ also tested for contaminants in purple varnish clams and Olympia oysters. None were over EPA screening levels.

Arsenic is a trace metal and chemical element that occurs naturally in sediments, bedrock, groundwater, plants, and animals. Inorganic arsenic is the toxic form of arsenic. This form is often associated with natural geology and rock formations but can also be introduced into the environment from pressure-treated wood, outdoor building materials, and by agriculture and industrial activities, OHA wrote in its technical report.

"Oregon's geology is naturally high in arsenic, and it is difficult to definitively identify the specific source of arsenic in the environment and in shellfish," the report reads.

According to OHA, chronic (long-term) exposure to inorganic arsenic can increase the risk of cancers of the skin, bladder, liver and lung. Chronic exposure can also cause wart-like skin problems, increase the risk of diabetes and cardiovascular problems (such as high blood pressure), and cause neurological problems including painful numbness or "pins and needles" sensations in toes and fingers.

The Oregon Department of Fish and Wildlife issues about 180,000 recreational shellfish harvest licenses each year. It estimates that fewer than 0.1 percent of recreational clam digger trips focus on harvesting softshell clams.

However, OHA warned, "It is possible that a clam digger consistently collecting from one particular spot over a lifetime could get clams that are consistently higher or lower than the mean used to calculate this advisory."

Some government officials, meanwhile, are urging the agency to make the information public immediately.

"I'm thinking, why should I know this information without the general public knowing," Newport city councilor David Allen said. "To me the bigger issue isn't the health advisory, it's the fact that the agency was sitting on the information."

tloew@statesmanjournal.com, (503) 399-6779 or follow at Twitter.com/Tracy_Loew