SHELTON (April 1, 2009) – Preliminary data released today by the state Department of Ecology has identified dioxin in sediment throughout Oakland Bay.

Outside of Shelton Harbor, the dioxin is distributed uniformly with an average concentration of 35 parts per trillion (ppt or pg/g). “At first glance, the distribution pattern suggests the dioxin may be a historical legacy,” said John Konovsky, the tribe’s environmental program manager.

Oakland Bay is a very productive shellfish growing area. Studies elsewhere suggest there is very little connection between dioxin concentrations found in sediment and contamination in shellfish:

• In a 2008 Ecology report on neighboring Budd Inlet, sediment samples weretested for dioxin and concentrations ranged from 3 to 60 ppt. Concentrations in littleneck/manila clam samples averaged 0.5 ppt.
• In Similk, Fidalgo and Padilla Bays, a 2006 study by the Swinomish Tribe identified a range of concentrations of organic compounds including dioxin in sediment, but levels in shellfish from those same sites were more uniform and much lower. The report also suggested that health risks from sediment exposure – such as digging for clams – are even lower than eating shellfish.
• A 2007 Humboldt Bay study concluded that dioxin concentrations in shellfish tissue were independent of dioxin levels in sediment. All the tissue directly tested and most reported in the worldwide literature was below concentrations considered to be a risk to human health. Without continual industrial output, dioxin levels in sediment and shellfish decline over time.

“It’s not surprising that shellfish accumulate very little dioxin and are safe to eat,” said Konovsky. “This is because dioxin builds up in fatty tissue and shellfish have a very low fat content.”

Scientists from the state Department of Health also believe that dioxin in the sediment of Oakland Bay does not pose a public health concern for shellfish consumers. When discovered in sediments elsewhere around Puget Sound, dioxin in shellfish has never been found at levels of public health concern.

“Oakland Bay has always been a favorite spot for tribal members to dig clams,” said Andy Whitener, natural resources director for the tribe. “The tribe is committed to working with state and federal governments to do whatever is necessary to clean up the bay. We want to absolutely guarantee the health of our tribal members and the entire community.”

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For more information, contact: Andy Whitener, natural resources director, (360) 432-3800. Jeff Dickison, assistant natural resources director, (360) 432-3815. John Konovsky, environmental program manager, (360) 432-3804.

Reports Cited

Science Applications International Corporation. 2008. Sediment Characterization Study, Budd Inlet, Olympia, WA: Final Data Report. Department of Ecology, Olympia.

Swinomish Tribe. 2006. Bioaccumulative Toxics in Subsistence-Harvested Shellfish—contamination results and risk assessment. La Conner, WA.

Pacific Shellfish Institute. 2007. Status Report and Synopsis of Organic Pollutants in Relation to Shellfish Safety in the Mad River Slough and Humboldt Bay, California. Humboldt Bay Harbor, Recreation and Conservation District, Eureka.

Extremely cold weather combined with very low tides in November 2008 or the unusually large influxs of sediment from the December 2008 and January 2009 storms seems to be taking a toll on clams in Oakland Bay.  Growers report that there are many more dead clams than usual–maybe twice the ususal number especially in upper Oakland Bay and Chapman Cove.

The increase in clam mortality will set up an interesting experiment this summer.  There seems to be a relationship between clams dying and summer nutrient levels/bacteria concentrations in Oakland Bay.  If the hypothesis is correct, this summer’s bacteria concentrations should be higher than 2008 or 2007.   A hot and sunny summer will likely enhance the increase.  We will have the results of the experiment by October 2009.

Fecal Bacteria Concentrations (MF/100 ml) at Stream Mouths

The Squaxin Island Tribe released their winter 2008-09 water sampling results to the Oakland Bay Clean Water District Advisory Committee on March 4th.  Five samples were collected at nine stream mouths between October 2008 and February 2009.  Two of the sampling days, 11/12 and 1/7, occurred during major storm events.  All the samples were analyzed for fecal coliform bacteria at the Department of Ecology Manchester Lab.

The sampling results from the storm days were much higher than the non-storm days.  This is a very common pattern in Western Washington because stormwater picks up large quantities of bacteria as it moves across the landscape.

The results indicate that Uncle John Creek is still a leading source of non-point water pollution entering Oakland Bay.  While there have been significant improvements over the last couple years that have taken Chapman Cove (downstream of Uncle John Creek) off the Department of Health’s water quality threatened list, there is still need for additional improvement to meet water quality standards.

Other creeks like Shelton, Malaney and Goldsborough also play a significant role in moving bacteria from the uplands to marine water.  Their contributions to water pollution must also be investigated and reduced in the near future to meet water quality standards.