Bird feathers show pollution increase over 120 years
Feathers collected from rare Pacific seabirds over the past 120 years
have shown an increase in a type of toxic mercury that likely comes from
human pollution, US researchers said on Monday.
Scientists at Harvard University took samples from feathers belonging
to the endangered black-footed albatross from two US museum collections,
said the study in the Proceedings of the National Academy of Sciences.
The feathers, which dated from 1880 to 2002, showed "increasing
levels of methylmercury that were generally consistent with historical
global and recent regional increases in anthropogenic mercury
emissions," the study said.
Methylmercury is a neurotoxin that can cause central nervous system
damage and comes from burning fossil fuels.
Rising levels of mercury in fish and seafood are believed to pose
dangers to human health, and pregnant women and young children are
particularly urged to limit the amount of some types of fish in their
diets. "Using these historic bird feathers, in a way, represents the
memory of the ocean," said study co-author Michael Bank, a research
associate in the Department of Environmental Health at Harvard School of
Public Health.
"Our findings serve as a window to the historic and current
conditions of the Pacific, a critical fishery for human populations,"
Bank said.
The highest concentrations in feathers were linked to exposure by the
birds in the post-1990 timeframe, which coincided with a recent spike in
pollution from Asian carbon emissions in the Pacific region, the study
said.
Mercury pollution from Asia went from about 700 tons annually in 1990
to 1,290 tons in 2005, the study said, noting that China became the
largest emitter of such pollutants in 2005 with 635 tons.
Pre-1940 levels of mercury in bird feathers were the lowest in the
study.
The black-footed albatross is listed as endangered by the
International Union for Conservation of Nature, which estimates about
129,000 of them are living in the northern Pacific, mainly near Hawaii
and Japan.
The birds feed primarily on fish, fish eggs, squid and crustaceans.
The high levels of mercury in their feathers could indicate a link
between their high-mercury diets and their decreasing numbers, said the
study.
"Given both the high levels of methylmercury that we measured in our
most recent samples and regional levels of emissions, mercury
bioaccumulation and toxicity may undermine reproductive effort in this
species and other long-lived, endangered seabirds," said lead author
Anh-Thu Vo, a graduate student at the University of California,
Berkeley.
Banks added that "mercury pollution and its subsequent chemical
reactions in the environment may be important factors in species
population declines." AFP
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