The toxins Metro Vancouverites flush down their toilets or pour down the drain have likely contributed to the decline of Fraser River sockeye salmon, a panel of scientists told the Cohen Commission which was named after the collapse of the 2009 sockeye run, when just over a million fish returned, a tenth the expected number.
There’s no “smoking gun” that points to sewage effluent as a leading culprit in the dramatic collapse of the 2009 sockeye run, said Dr. Ken Ashley, a BCIT instructor and consultant. But he and others rated it a probable factor in the longer term trend of diminishing salmon returns.
Dr. Peter Ross, a marine mammal toxicologist at the Department of Fisheries and Oceans’ Institute of Oceans Sciences, said there’s growing concern about the discharge of persistent chemicals that accumulate in the environment and threaten fish and sea life.
Emerging chemicals of concern include flame retardants such as PBDEs, bisphenol-A, phthlates, nanoparticles, synthetic musks and personal care products. “PBDEs have been doubling every 3.5 years in harbour seals in the Strait of Georgia,” Ross said, adding very high concentrations have been found in sediments near Metro Vancouver’s sewage treatment outfalls and in Burrard Inlet.
Such chemicals might not kill fish outright but may pose more subtle threats, even at minute levels, the commission heard.
Endocrine disruptors can interfere with hormones and in some cases feminize fish. They can also reduce growth and suppress immune systems. Panelists said sockeye need to “smell their way” back home to their birth streams to spawn and the soup of chemicals mixed into the waters of Georgia Strait and the Fraser River could confuse them and reduce their chances.
Sewage treatment plant monitoring relies on tests of how many sample fish exposed to effluent die within four days but don’t specifically test for many chemicals or consider their longer term cumulative impacts.
Ross supported broader testing of effluent for such chemicals and said he tried but failed to persuade federal officials to make that a requirement in new standards Ottawa has set out to govern sewage treatment.
Ross said tests should look at not just the impact of individual chemicals but the complex mixtures that can form and interact unpredictably in the receiving waters.
Source: BC Local “Toxins down Metro drains threaten salmon: Scientists”, June 17, 2011