Encouraging signs in the toxic sediments of Elliott Bay

A newly released study of toxic chemicals on the bottom of Seattle's Elliott Bay shows signs of improvement in the environmental quality of the sediment, though researchers found some contaminants have increased, the state Department of Ecology said Friday.

The department released the results based on samples taken in the urban bay in 2007. While toxic pollutants are still widespread, researchers said a comparison with a similar 1998 study gives encouraging signs.

"It's kind of a mixed story, but I think there is good news in there," said Margaret Dutch, an Ecology sediment expert who participated in the study.

The findings are part of the Urban Waters Initiative, in which Ecology is examining sediment quality in the marine waters off Puget Sound's larger cities. It began by studying Elliott Bay and the lower reach of the heavily industrialized Duwamish River, which feeds into the bay, and compared findings with samples taken at the same 30 locations in the 1998 study.

In general, the new study found a slight overall reduction in toxicity of the sediment and healthier populations of bottom-dwelling invertebrates, such as worms and small crustaceans.

It found lower levels of several toxic metals, including mercury, lead and tin, and reductions in some chemical compounds such as polychlorinated biphenyls and some types of polycyclic aromatic hydrocarbons.

PCBs, once widely used in transformers and other industrial applications, have been shown to cause cancer, and their manufacture was banned in 1979. PAHs, formed during the incomplete burning of coal, oil, gas and other organic substances, also have been linked to cancer.

Some levels of contaminants increased, including those for zinc and plasticizers, while levels for arsenic, copper, chromium, nickel and cadmium stayed the same.

"We did see some improvements, which we are glad to see," Dutch said. "But there are some compounds that are increasing. We still know that there is work to be done."

Many of the pollutants measured are long-lived and would not be expected to decrease much in 10 years, she said.

Zinc is used in a wide variety of products, including tires, brakes and galvanized metals. Plasticizers or phthalates (THAY'-lates) make plastics more flexible and are used in everything from building materials to personal care products to children's toys. Ecology says zinc at low levels can harm aquatic life, while plasticizers can interfere with human hormones.

Rob Duff, manager of Ecology's environmental assessment program, said that while the changes in sediment health are small, they can help tell whether environmental regulation, pollution control or cleanup efforts are effective.

"These are significant findings for the heart of Puget Sound, where the bulk of the state's population lives," Duff said in a news release.

For scientists, the study will give valuable baseline data for later research, Dutch said.

Although state and federal regulations have helped curb pollution from many industrial sources, Ecology says contaminants still reach Puget Sound from air pollution, stormwater runoff and other sources. The agency lists stormwater pollution, which comes from a huge number of sources as rain washes contaminants into drains, as the top threat to Puget Sound water quality.

The study is part of the state's Urban Waters Initiative, a long-term effort to measure pollutants in the marine waters off Puget Sound's larger cities. The Ecology Department is wrapping up a similar sediment study it conducted last year in Tacoma's Commencement Bay, is presently testing samples taken near Bremerton in June, and will examine Bellingham Bay in 2010, Budd Inlet near Olympia in 2011 and Everett Harbor in 2012.