U.S. Water News Online
GRANTS PASS, Ore. -- Scientists looking for fish tainted by
mercury found them in every fish and every river they sampled across
the West, suggesting that industrial pollution generated around the
world is likely responsible for at least some of it.
The survey of 2,707 fish randomly collected from 626 rivers in 12
states represents the biggest regional sampling yet of mercury in
fish in the West, said Spencer A. Peterson, senior research ecologist
EPA's National Health and Environmental Effects Research Laboratory
The findings by scientists from the EPA and Oregon State
University were reported in this month's issue of the journal
Environmental Science & Technology and came out of an EPA survey
of various environmental factors in rivers conducted between 2000 and
Though the survey found some fish with elevated mercury levels,
suggesting a local source such as an old mercury mine, most levels
were low, in line with canned tuna found in grocery stores, said Alan
T. Herlihy, associate research professor in the OSU Department of
Fisheries and Wildlife.
No attempt was made to specifically link the mercury in the fish
to mercury in the atmosphere, but the low but widespread levels
suggest the mercury came from deposition -- mercury in the atmosphere
falling to the earth in rain and snow, Herlihy added.
While generally below levels considered unsafe for people to eat
from time to time, the mercury could pose a danger to fish and
wildlife that depend on fish for their diet, said Robert M. Hughes, a
fisheries and wildlife research associate professor at OSU who took
part in the study.
Levels were generally higher in fish-eating fish, such as bass,
walleye and pike, than in insect-eating fish, such as trout.
"What's important to note is that the levels are below what we
consider a health concern in most fish," said EPA spokeswoman Suzanne
Elevated mercury levels have been linked to learning disabilities
and developmental delays in children and to heart, nervous system and
kidney damage in adults. Out of concern for the health effects,
several states and the federal government have taken steps to cap
It has long been understood that industrial emissions, such as
coal-fired power plants, are responsible for some percentage of the
mercury found in fish, said Steve Lindberg, a retired research fellow
from the Oakridge National Laboratory, who did not take part in the
study. The question is how much.
About two thirds of the mercury circulating in the atmosphere is
generally considered to come from industrial or human sources, with
the rest from things like volcanoes and other geologic sources,
Lindberg said he is involved in research that has been tracking
specific isotopes of mercury introduced into a lake watershed in
Canada as they show up in fish, and will go on to see how mercury
levels in the fish react when the mercury is cut off.
"It does suggest that concentrations in fish from mercury from the
atmosphere are highly responsive to the amount of mercury being
deposited from the atmosphere," he said. "We would argue in support
of the notion of reducing industrial emissions to reduce the
concentrations of mercury in fish."
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