Tuesday, 1 March 2011

Not so Great Lakes?

During my routine scanning of the endometriosis literature an interesting article caught my eye. Here is the abstract for the article, which you will probably notice does not really concern endometriosis (even though it is a keyword for the article). The article concerns uterine leiomyomata (fibroids) and their occurrence in relation to consumption of fish from the great lakes of North America, so this got me thinking and doing a little bit more digging on the subject.

For those like me, who are not native to the Americas, the great lakes are a series of very large bodies of water on the U.S/Canada border. Named Superior, Michigan, Erie, Huron and Ontario, these lakes have several major cities located either on or near them. The trouble is that where there are cities, there’s industry and where there’s industry, there’s pollution. There are probably lots of different types of pollutants that end up in the lakes, however in this case we are going to focus on a particular type, the polychlorinated biphenyls (PCBs).

PCBs are things you definitely don’t want inside your body as they disrupt the endocrine system (your hormonal system) leading to all sorts of unpleasant side effects. The good news is that PCB production has been banned in most countries including the USA (1979) and UK (1981). However, PCBs were still used in these countries and they tend to hang around in the environment for decades (they were also known as persistent organic pollutants). You may, therefore, rightly be wondering if PCBs have been linked with endometriosis. I’m afraid I can’t give you a straight answer on that one yet as nobody seems to have drawn any firm conclusions. There are those studies that say “yes there’s a link”, “oh yes there is definitely a link”, “look, I keep telling you there’s a link there somewhere”. But then there are those studies that say “no link here”, “nope, no link here either”, “seriously, we can’t see any significant link here”. So as far as concrete scientific evidence goes, it’s a resounding shrug of the shoulders followed by a defeatist “I dunno”.

Despite all the contradictory and confusing evidence most agree that PCBs are not good for you, you wouldn’t want them in your water and you sure as hell wouldn’t want them in your salmon fillets. Unfortunately that’s exactly where these PCBs may end up (if you live on the great lakes and eat the fish from there). PCBs are man-made compounds that had a number of uses in industry such as lubricants, hydraulic fluids, plastics and adhesives and it’s an inevitable fact that some ended up getting into the environment, and stayed there. A few studies have found PCB pollution in the sediment of Indiana Harbour on Lake Michigan, and subsequently in the salmon of that lake. I’m not just singling out Lake Michigan here either. PCBs have been found polluting most of the great lakes and getting into the human food chain through fish consumption. PCB levels appear to have dropped steadily though between 1996 and 2006, which is no doubt due to a concerted clean up effort in the lakes and certainly a step in the right direction.

Let’s go full circle and get back to the article I mentioned in the first paragraph. That particular study found some evidence that PCB exposure from fish from the great lakes contributes to an increased risk of uterine leiomyomata (Fibroids). Fibroids have been found to be quite common in women with endometriosis and both diseases share similar risk factors. It’s a shame the original study didn’t give more detail on the incidence of endometriosis in the consumers of great lakes fish and it’s a further shame that there is no consensus to whether or not PCBs are linked to an increased risk of endometriosis. Despite all the uncertainty it is still interesting to find some evidence that increased consumption of great lakes fish may lead to an increase in the body burden of PCBs, which in turn may lead to an increased risk of certain reproductive disorders, including endometriosis.

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