Friday, August 21, 2009

Mercury in Fish

A report just came out today showing that even recreationally caught fish in US backwaters have dangerous levels of mercury.

We've known about mercury in ocean fish for many years, but not as much in freshwater streams, but it's now looking like many of those fish are also above accepted levels. Fish is so good for you this a real blow, not to mention I also enjoy fish now and then. Where does the mercury come from? A certain amount is in the environment naturally and washes into streams or is evaporated and carried as rain, more is from the mining industry (for both mercury and gold - where mercury is used in processing), and more comes from burning fossil fuels (which have mercury in them that are released when burnt). The mercury gets into the smaller organisms, like plankton, which is then eaten by little fish, who are then eaten by big fish, and so moves up the food chain, getting more concentrated as it goes.

The big difference here is that there was a study that came out a few years ago that suggested large ocean going fish were picking up mercury (or methylmercury which is the 'bad' form) from natural sources, rather than pollution. These freshwater fish though are though to be picking it up from pollution rather than natural sources. The levels of mercury in tuna have apparently not changed over the last 20 years, despite atmospheric levels increasing to much higher levels, whereas these freshwater fish have seen increases in mercury levels over the years.

So here is a recent list of high and low - but even in the high, the EPA still says that eating fish twice a week is still safe.

High Mercury
Shark
Swordfish
King Mackerel
Tilefish
Bass

Low Mercury
Shrimp
Light tuna
Salmon
Trout
Scallop

2 comments:

PleaseRecycle said...

This was so depressing. We are familiar with the problem though because a) Matt(dh) loves to fish in local lakes and streams and b) Georgia and South Carolina streams have some of the highest mercury levels in fish (I think it's the slow blackwater rivers where there are a lot of micro-organisms).

We never eat anything Matt catches though.

nicola said...

thanks for this post, rhian. a couple friends and i were just talking about fish (and then ultimately meat, other foods, and then food containers) as we watched our children play. i never cared as much as i do now that i have these fresh little bodies and brains i am trying to protect.