Mercury in the Environment: Accumulation in Fish and What You Can do to Reduce Your Risk of Mercury Exposure.

Mercury is one of the first known chemicals, and has been studied for hundreds of years. Yet recently, there has been a substantial increase in government attention and media coverage of mercury. In particular there has been an increase in studying the movement and accumulation of mercury in fish, and the possible risk to humans from consumption of contaminated seafood. In 2004 the Environmental Protection Agency and the Food and Drug Administration released a joint recommendation for the amount of fish people should eat. They recommend not eating more than 6 ounces of fish per week for most fish, including Albacore tuna There are even some fish species that are okay to eat twice a week; these include shrimp, salmon, pollock, catfish, and canned tuna.

Some species are not recommended to be eaten at all, and you can learn more about these recommendations, click > EPA and FDA Questions and Answers on Fish Consumption.

Eating fish does have many healthy advantages, and so balancing these healthy advantages with the risk from mercury is important. Eliminating fish from your diet is not necessary, and as long as you are careful, only eat fish occasionally, and avoid those species which should not be eaten, you can enjoy fish without worrying about mercury.

There are some simple ways to reduce your personal exposure to mercury. Your body actually has natural ways to remove small amounts of mercury, and so very low levels may not be necessarily harmful.

  1. Reduce the amount of large fish consumed. Follow the EPA guidelines or look at the guidelines published by other states. These guidelines are based on national average mercury concentrations for 6 oz fillets.
  2. Increase the amount of time between consumption of fish. The longer you wait until eating fish again the longer your body has to remove any mercury which you may have eaten.
  3. Avoid working or living near industrial factories that use mercury in their manufacturing. If you are curious about a particular factory, look around online to see if mercury is commonly used in manufacturing. If they use mercury it may be a good idea to consult your local environmental regulatory agency to make sure that they are being monitored and to get some information on the plants history of regulation compliance.

How Do Mercury Levels in Fish Become so High?

Mercury ContaminationMany fish species and humans as well, have a natural ability to release mercury from their body. There are naturally produced proteins known as metallothioneins which facilitate removal of some metals. These proteins can take some time to remove all of the mercury in the body. Since the body cannot release the mercury very quickly, it will tend to accumulate in fish. What is worse, this mercury in the fish can pass to any predator that may be so lucky as to make a meal out of the contaminated fish. Larger, longer living fish will thus have a higher level of mercury since they eat more fish over their lifetimes. It is this process, known technically as bioaccumulation that is the reason that the FDA and EPA do not recommend eating large and predatory fish species. Mercury levels will increase the higher up a fish is on the food web.

How Does Mercury Get into the Environment?

Mercury is a naturally occurring metal that can become released into the environment through either natural methods or by anthropogenic, human caused means. Mercury is released naturally by volcanoes, and by the slow release from the weathering of rock. In fact, the amount of mercury released by humans has been larger than that coming from nature ever since the beginning of the industrial revolution. Mercury is released into the environment from several processes, mainly smelting of various metals, combustion of products that contain mercury, and the industrial processes which use mercury such as, pulp and paper manufacturing, paint preservatives, pesticide manufacturing, and battery production amongst others.

What are Some Dangers of Mercury?

In the environment, mercury can affect the number and distribution of fish. Mercury can cause developmental problems in small fish; which in turn can reduce the ability of the young fish to survive and if the younger fish are less able to reproduce that will have effects on the entire population of fish in that area. This can even lead to lower catch numbers and can hurt commercial fishing in the area. Having less of one species of fish can change other species as well. Fewer fish can mean less food for predators so they can’t survive, or the opposite can happen were there are fewer predators to eat the prey and so the prey becomes more abundant. Either way the natural system has been changed and may not ever be able to recover.

In people, mercury has the ability to enter into the fetus while in the womb and can accumulate there. Besides affecting the child at a very young age, mercury is more harmful to young children then to adults. Mercury can cause many problems especially mental problems including incoordination, mental retardation, blindness, seizures and the inability to speak. These horrible effects are the reason that the EPA and FDA especially singled out mothers and would be mothers. In older people, mercury has been found to affect the nervous system, but can also modify the immune system.

Andrew Ryan, BA in Environmental Toxicology.