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.”
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.
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.