NCJ - Dioxin found in Humboldt Bay Oysters But is it a health threat?

Dioxin found in Humboldt Bay Oysters But is it a health threat?

by KEITH EASTHOUSE

Elevated levels of dioxin, one of the deadliest chemicals known, have been found in commercial oysters in Humboldt Bay.

But experts interviewed for this story sharply disagreed about whether the levels -- which ranged from slightly less than one part per trillion to just over four parts per trillion -- are high enough to present a significant public health risk.

The findings are presented in a recently completed 19-page report prepared for Sierra Pacific Industries, which is being sued by environmentalists for allegedly discharging dioxin-containing pollutants into the bay in violation of the Clean Water Act.

The study was done after Coast Seafoods, Inc., the largest operator in Humboldt Bay, and other local oyster companies, raised concerns about the possible contamination of their oyster beds.

The concerns stemmed in part from stories that appeared in the North Coast Journal earlier this summer that mussels and crabs in a part of the Mad River Slough immediately adjacent to Sierra Pacific's Arcata mill contained elevated levels of dioxin.

The new report, done by a Bay-Area based consulting company called Environ, found no pattern in the dioxin detections that points to Sierra Pacific's mill as the source. Additionally, the report said that the concentrations of dioxin that were found in the oysters are much too low to pose a threat to anyone.

"No one will eat enough of those oysters over time to generate a significant health problem," said Richard J. Wenning, senior manager at Environ and the main author of the study.

A scientist hired by the Ecological Rights Foundation, the Oakland-based environmental group that is suing Sierra Pacific, vehemently disagreed.

Marc Lappe, a toxicologist, did not dispute the data that the report is based on. Instead, he challenged the interpretation of that data, saying that the report was a "serious distortion" and "a whitewash [that] does the public a great disservice."

Lappe, who runs a consulting company called the Center for Ethics and Toxics, based in Gualala, Calif., said that the levels of dioxin are high enough that "a strict limit is clearly needed" for people who eat oysters from the bay.

He recommended that adult males consume no more than a single monthly serving of six oysters. He said pregnant women "probably should not eat (Humboldt Bay) oysters" at all.

Lappe called for an "independent entity" to review the oyster data and possibly to do more sampling.

Exposure to dioxin, a byproduct of many industrial processes, is "associated with a wide array of adverse health effects," according to a fact sheet put out by the U.S. Environmental Protection Agency. Dioxin, a group of 210 structurally similar organic chemicals, has been shown to be toxic to virtually every organ and physiological system in the body, including "the liver, the gastrointestinal system, the blood, the skin, the endocrine system, the immune system, the nervous system and the reproductive system," according to the fact sheet. Additionally, the EPA has classified dioxin as a "probable human carcinogen."

As of 1998, according to the fact sheet, 19 states had issued 59 "fish advisories" for dioxins. "These advisories inform the public that dioxins have been found in local fish at levels of public health concern," the fact sheet said. "State advisories recommend either limiting or avoiding consumption of certain fish from specific waterbodies or, in some cases, from specific waterbody types [such as] all freshwater lakes or rivers."

Whether a public health warning is issued for Humboldt Bay shellfish remains to be seen. The Environ study itself or a summarized description of it has been distributed to several government agencies, including the state Department of Health Services, the state Office of Environmental Health Hazard Assessment, the seafood safety unit of the California Food and Drug Branch, the state Department of Fish and Game and the Humboldt County Health Department.

A public health advisory could be devastating to the bay's oyster industry, the largest in the state. Oysters grown in the bay are distributed to restaurants and markets up and down the West Coast.

The Environ report analyzed 12 to 24 oysters collected from nine commercial beds on June 21. The beds are owned by Coast Seafoods, Inc., and the North Bay Shellfish Company. Additionally, oysters and mussels were tested from a storage platform located in the Mad River Slough near the Sierra Pacific mill. Environmentalists and Sierra Pacific consultants clashed on the following issues related to the report.

Disagreement about the amount of Humboldt Bay oysters that can safely be consumed.
The report says that the dioxin levels, which range from 0.8 to 4.3 parts per trillion, are "well below" the 25 parts per trillion limit identified by the U.S. Food and Drug Administration as "a level of concern" in terms of cancer risk.

Environmentalists said the FDA "benchmark," as it's called, is 21 years old and is seriously outdated. They cited a more current standard -- the EPA's "monthly fish consumption limits for dioxins/furans" (an associated substance). That limit, meant to identify an acceptable cancer risk, recommends against ingesting more than 1.2 parts per trillion of dioxin per month from eating fish. Most of the oyster samples that were analyzed from Humboldt Bay contained dixoin at levels in excess of this standard. Wenning, of Environ, acknowledged that the environmentalists "are not wholly incorrect" about the FDA limit being outdated. However, he said there is no newer FDA standard.

Disagreement about how the dioxin levels in Humboldt Bay oysters compares to oysters from elsewhere.
The report emphasizes that the levels are comparable to commercial oysters grown at other locations in the U.S. The report also stresses that oysters in British Columbia near pulp mills contain twice as much dioxin as Humboldt Bay oysters.

Lappe said the assertion that dioxin levels in Humboldt Bay oysters are comparable to U.S. oysters elsewhere is misleading. He said the report itself indicates that Humboldt Bay oysters contain more than seven times as much dioxin as the U.S. average for oysters.

Disagreement about how the average daily intake of dioxin from consumption of Humboldt Bay oysters compares to dioxin intake from other food sources.
The report says that on average people get more dioxin from eating foods such as eggs, milk and beef than they do from eating Humboldt Bay oysters.

Fred Evenson, an attorney with the Ecological Rights Foundation, said that this is misleading because the report uses average intake figures based on the entire U.S. population. "Most Americans don't eat Humboldt Bay oysters, so it comes as no surprise that the average American will take in more dioxin from other sources."

Evenson and Lappe both said that Environ's entire risk assessment is based on the assumption that the average American eats about three oysters a year. That, apparently, is the intake level if consumption is averaged out over the entire population rather than limited to the 10 to 20 percent of the population that eats shellfish.

If you separate out the subset of the population that eats Humboldt Bay oysters, for example, then the consumption of those oysters -- along with the dioxin they contain -- goes up, Evenson and Lappe said.

So far, it does not appear that a scientist uninvolved with the litigation between Sierra Pacific and the Ecological Rights group has had time to review the report, completed in the third week of July. Researchers with the state Health Department and the health hazard office (which has the power to issue public health advisories for fish) who were sent the report were either on vacation this week or otherwise unavailable for comment.

Susan Warner, executive staff director of the state Regional Water Quality Control Board, declined to comment on the report, noting that her agency does not deal with public health matters. Warner said, however, that she suspected that there would be additional sampling of aquatic life in the Mad River Slough and possibly in the commercial oyster beds out in the bay.

In early June, the board asked Sierra Pacific to draw up a workplan to perform a "human health and ecological risk assessment" of the slough, which has long been a popular fishing spot. That decision was taken after dioxin was found in mussels and crabs in the slough by the Ecological Rights group.