Mirroring a drop in emissions, mercury in tuna also declines

For years, public health experts have warned against eating certain kinds of fish, including tuna, that tend to accumulate mercury. Still, tuna consumption provides more mercury to US consumers than any other source.

But recently, as industry cuts down on its mercury emissions, research has found mercury concentrations in some fish are dropping. The latest study, published in Environmental Science & Technology, reports that this is the case for prized Atlantic bluefin tuna.

Although global mercury emissions continue to rise due largely to increases in coal burning in Asia, emissions in North America between 1990 and 2007 went down 2.8 per cent per year, according to published studies in 2010 and 2013.

Over a similar period, mercury in north Atlantic waters dropped 4.3 percent annually. And between 2001 and 2009, mercury in the air above the north Atlantic declined by 20 per cent, or about 2.5 per cent per year.

To see whether the regional emissions reductions were having an effect on fish at the top of the ocean food chain, researchers from Stony Brook University, the University of Massachusetts and Harvard University collected and analysed tissue samples from nearly 1,300 Atlantic bluefin tuna captured between 2004 and 2012.

Tests for mercury content showed that over this eight-year period, the concentration in the fish dropped an average of 19 per cent. The finding suggests that reductions in mercury emissions could rapidly lead to reduced mercury concentrations in some marine fish, the researchers say.