Mercury levels dropping in north Atlantic tuna

(HealthDay)—Mercury levels in one tuna species have decreased along with industrial emissions of the dangerous chemical element, a new study finds.

The results suggest that reductions in mercury emissions could quickly result in lower mercury levels in some species of ocean fish, according to researcher Nicholas Fisher and colleagues. Fisher is a professor at the School of Marine and Atmospheric Sciences at Stony Brook University in Stony Brook, N.Y.

Mercury, a neurotoxin, can harm the nervous system of humans. It accumulates in tuna and other types of fish, which has led to warnings against eating too much tuna, the researchers said in background notes.

Although increased coal burning in Asia has raised mercury emissions globally, levels have fallen in North America 2.8 percent a year between 1990 and 2007, the researchers said.

Over a similar period, mercury in north Atlantic waters dropped 4.3 percent annually. And mercury in the air above the North Atlantic Ocean declined 20 percent from 2001 to 2009, the researchers said.

To assess the effects of those declines, the research team analyzed mercury levels in tissue samples from nearly 1,300 Atlantic bluefin tuna caught between 2004 and 2012.

During that time, mercury levels in the fish fell an average of 19 percent, the researchers said in a news release from the American Chemical Society.

Although encouraging, the study results don't actually prove a direct cause-and-effect relationship between changes in regional mercury emissions and lower levels of the toxin in fish.

The findings were published recently in the journal Environmental Science & Technology.

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