WASHINGTON — Some good news from the government scientists who study pollution in U.S. coastal waters: A newly released 20-year study shows overall levels of pesticides and industrial chemicals generally are decreasing.
The Mussel Watch program of the National Oceanographic and Atmospheric Administration examined levels of 140 chemicals from 1986 to 2005 in coastal areas and estruaries of Alaska, Hawaii, Puerto Rico, the East and West coasts, the Gulf of Mexico and the Great Lakes. Mussel Watch is the longest continuous contaminant monitoring program in U.S. coastal waters.
Gunnar Lauenstein, an oceanographer who's the lead scientist of the program, said the levels are continuing to decrease, many years after environmental laws were enacted in the 1970s.
"Different regions have different stories," Lauenstein said, with some contaminants increasing in some regions.
But, Lauenstein said, "when you look at all the numbers and evaluate them statistically, it shows that on a national basis, concentrations are going down."
The pesticide DDT shows significant decreasing trends around the country, even in Southern California, which had the heaviest concentrations, Lauenstein said. Industrial chemicals, such as PCBs, a material used in electrical products, including transformers, also show declines.
PCBs are transported through the atmosphere over long distances.
The report said that most organic contaminants do not have natural sources, but they are distributed everywhere.
Some problems highlighted in the report include oil-related compounds from motor vehicles and shipping, which continue to flow into the waters. NOAA also is studying flame retardants, known as PBDEs, and plans to release findings later this year about the effects they have on marine and human health.
No overall national trends could be determined for trace metals. High levels of metals and organic contaminants remain near urban and industrial areas.
The report also found that levels of tributyl-tin, a compound that was used to kill marine organisms on boat hulls, were declining. The compound affected not only the organisms it was meant to kill but also other marine and fresh-water life. Tributyl-tin was regulated in the late 1980s and its use is also decreasing nationally.
Under the Mussel Watch program, scientists collect mussels, or in some places oysters, every year at some 300 sites and and measure the contaminants that accumlate in their fatty tissue. Mussels and oysters don't have great ability to metabolize the organisms, and so their tissue is a good indicator of what's going on in the water, Lauenstein said.
Although many scientific studies have been written about the findings, the online report released Monday was designed to be used by the general public and policymakers as well. The monitoring will continue and the report will be updated.
National-scale studies like the one from the Mussel Watch program as rare but important, because they allow scientists to make connections that they couldn't do if they were only looking at one locale or region, Gary Matlock, the director of NOAA's
National Center for Coastal Ocean Science, wrote in an introduction to the report. Making those links "is an important and necessary part of solving environmental problems."
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The report (large .pdf) is available at http://NSandT.noaa.gov