WASHINGTON (AP) -
In much of the world’s oceans, levels of the metal mercury are double to
triple what they were before the industrial revolution, a new study says.
there’s more mercury from human sources - mostly burning fossil fuels and
mining for gold - than scientists had thought.
The study assessed
inorganic mercury, which in the ocean gets converted into the toxic
methylmercury found in seafood. When pregnant women, nursing mothers and
young children eat too much methylmercury-tainted seafood, there’s an
increased risk of nervous system problems in the developing child.
The new results
don’t provide any immediate conclusions about eating fish, says Carl Lamborg
of the Woods Hole Oceanographic Institute in Massachusetts. His study is
published Wednesday in the journal Nature.
“Everywhere on the
planet is contaminated with mercury to some extent,” he said.
His study found
that mercury concentration varied by depth, generally higher at the surface
and mid-level depths than in deep water. But in the North Atlantic, high
concentrations reached even deeper than 3,300 feet.
In general, mercury
levels between the surface and 330 feet deep were more than triple
pre-industrial times levels, Lamborg said. Between 330 and 3,300 feet deep,
they were about 150 percent greater than the levels from more than a century
ago. But they were only about 10 percent higher at depths greater than 3,300
feet, except for the North Atlantic.
of the world’s ocean mercury from man-made sources is in water that’s
shallower than 3,300 feet, the study found.
The study is
important and will help scientists eventually understand how mercury gets
into the marine food chain and us, said University of Michigan Earth
sciences professor Joel Blum, who wasn’t part of the study.