Mercury And Fish

What is meant by the term 'boomerang toxics'?

We coined that term boomerang toxics to mean the kinds of chemicals that we fairly thoughtlessly threw out into the environment over the course of the last four or five decades that went out in our air plumbs from smoke stacks that went out in our hazardous waste and oily sludge's that we let go into rivers. And eventually these chemicals got into water bodies, got into fish and they've come back to us they boomeranged back to us on our dinner plate in terms of again, things like fish, things like beef, and dairy that have from chemicals that settle on to soil and get taken up into dairy and meat by the action of bioaccumulation in these different kinds of animals. So they boomerang out in terms of our waste they boomerang back in terms of our dinner plate and many of these are globe trotting chemicals such that what we throw away here may end up in a polar bear, may end up in some bodies diet in the Far East. It's all one small planet when it comes to these kinds of toxins.

What is 'mercury'?

Mercury is an element that we traditionally know about it from our know about it from out contact with fever thermometers because it was that liquid that goes up when your fever goes up it registers higher because it expands as it heats. So mercury has been used in a lot of light switches it has been used in batteries and so it enters the environment when we burn things that have mercury. That's why mercury have been taken out of batteries. As a matter of fact a good example is in the Everglades because fish levels of mercury have spiked in the 1990's and early 2000's from all the button batteries from hearing aids in South Florida that were getting burnt in incinerators. The plumb of mercury exhaust was going out into the Everglades depositing in the fish and so nobody could eat the fish from the Everglades because of that. Since then we've taken mercury out of batteries and the Everglades are coming back.

What are the dangers of mercury in fish?

Mercury is something that is toxic to the developing nervous system. When a baby's nervous system is forming, in utero, inside of the womb, the way the brain is organized, is, there's critical points of development, where the centers of the brain activity are organizing themselves. Mercury interferes with the movement of neurons into the centers of activity. And so mercury can be highly toxic to the developing brain and effect the way children learn post-nasally. The effects are irreversible, and so it's very important for pregnant women and for young children to have as little mercury as possible. Zero would be a nice goal, we can't get down to zero but we know that the major source of mercury in our environment, in the human environment is from eating fish.

Who should be most cautious of mercury exposure from fish?

It's very important to follow fish consumption advisories if you're pregnant, or if you're planning to become pregnant, because the half life of mercury in the body is about two months. Which means that it takes a long time to clear out of your system so that even before you think about becoming pregnant, if you're a woman of child bearing age, you should only eat the right fish. Fish is important to eat during pregnancy because it's got nutrients that are very important for brain development, however, mercury counteracts that and it can really be a drag on brain development. The most damaging effects of mercury are on the developing fetus because brain development is at a critical stage during that time and in the first couple of years of life as the brain is still evolving. And so, pregnant women and young children should avoid mercury to the greatest extent possible. People often ask about breast milk, and there are so many benefits from breast feeding including; positive affects on the immune system and neurodevelopment that women should always nurse their children if at all possible. However, nursing mothers should also decrease their exposure to mercury by eating the right fish.

What is a 'fish consumption advisory'?

A fish consumption advisory is when an official body, like the state government or a local health department, tells folks in that town what fish may be high in contaminants that should be either not eaten at all or eaten in moderation so that people can eat fish safely knowing what the limits are to safe consumption, because in general the more they get exposed to things like mercury, the greater the risks are. So a fish consumption advisory tells people, like pregnant women, how much fish they can safely eat and not worry about a risk to their developing baby.

Where can I find my local fish consumption advisory?

Fish Consumption Advisories are usually issued by state health departments through newsletters and fact sheets and press releases. Usually these health departments will have a website where they'll post advisories for their local water bodies in that state. There are also federal websites that talk about fish consumption advisories across the whole country, and so you can click on your state and find out what advisories there are in your locale. Also, fish consumption advisories may pertain to commercial fish that you can buy at the supermarket, or at the restaurant. Those Advisories may be posted in supermarkets, or you may also have to go to your health department to find out what Advisories they have for fish in your local markets.

How are mercury levels in fish measured?

The mercury can be sampled in any fish species, there's a fairly easy test to do. The fish is broken up into little blocks and sent off to the lab where they can digest the fish. Mercury is not supposed to be in fish and it stands out as a unique element that's very easy to test for. The levels are usually recorded in the parts million and one or two parts per million is a very high concentration. Even though it doesn't sound like a lot, it's a very high concentration of mercury in fish that can lead to bad effects on brain development.

When were mercury levels in fish first discovered to be a risk to humans?

We understand the toxicity and the dangers of mercury in fish from the epidemiology study of populations of people who eat a lot of fish. So for example, there is an island off of Europe called the Faroe Islands. The offspring of women there, who ate a lot fish during pregnancy, experienced six month delays in learining in school. They were about six months behind everyone else in terms of academic achievement in the Faroe Islands school system. Some populations of people are actually less affected by mercury in fish. It may be because of the kinds of fish they're eating. For example, there's another island off of India that's been heavily studied, called the Seychelles Islands. Those people have less effects from mercury in fish. However, we here in the United States probably are in between those two populations and there is evidence that we are also affected and our children's brain development is affected by fish levels of mercury.

Can fish from the market be high in mercury?

There are certain fish from the supermarket that can be high in mercury. In particular, swordfish is among the highest and most popular fish in the supermarket that people tend to run into that can be high in mercury. Also, shark and tilefish can also be very high in mercury. Intermediate levels of mercury in the supermarket fish are canned tuna - that is white or albacore tuna. It doesn't matter if it is packed in oil or packed in water. The white tuna tends to be from bigger older fish, albacore, and that can be moderately high in mercury. Tuna steak, which you often find in sushi, could be moderately high in mercury. Those kinds of species you should only eat one meal a week of. Whereas swordfish and shark, if you're a pregnant woman you shouldn't eat any of that at all during your pregnancy.

Which fish are typically low in mercury?

Fortunately, there's many types of fish in the supermarket that are low in mercury and should be eaten more liberally, and that, for example, includes salmon. Salmon is high in omega 3 fatty acids, which is a beneficial nutrient from fish and it does help brain development, and that is because they're farm raised or because they come from very wild places north of Alaska. Those fish tend to be low in mercury. Also cod and haddock, flounder -- those species tend to be low in mercury. There are fish consumption advisories that you can find, from the FDA, that you can find from your local health department. Go through the whole list of different kinds of fish, and which ones are low, intermediate, or high in mercury, so that you can know what you can eat more of, and what you should avoid completely.