How Bioaccumulation and Biomagnification of Pollutants is Affecting Our Food Supply

When pollutants, such as those found in contaminated stormwater runoff, enter the food chain faster then they leave it, we can say that they have been bioaccumulated. Bioaccumulation problems are associated with high or frequent exposures to toxic chemicals in the environment. These contaminants can be anything from pesticides and fertilizers to industrial manufacturing effluent and air pollution.

An example of bioaccumulation could be when an animal drinks polluted water or breaths tainted air. These toxic chemicals in the air and water enter the animal’s body at a higher dose than what is normally expected to occur in an everyday setting. This can either kill or injure the animal and sets the stage for residual contamination and future biomagnification to occur.

Biomagnification occurs when the concentrations of the toxic substances increase as they move upward through the food chain. Biomagnification can only happen when the chemicals are fat soluble, have a long life span, and be biologically active (reactive to organic matter). What this means is that a small or normally insignificant amount of a contaminant in the environment can slowly collect inside of an organism and eventually grow to concentration that could cause great harm to it.

A perfect example of biomagnification is the mercury that is sometimes found in tuna fish. The concentration of mercury in the environment in which the fish resides is extremely low. However, its concentration is magnified as it moves upward through the food chain. Over the lifespan of the tuna, the concentration of mercury in its body has slowly increased to levels that may potentially be harmful to humans.

Another great example of chemical biomagnification is the story of the insecticide DDT. This chemical was made popular in the early 1940’s by its success in controlling mosquitoes. By the 1960’s, biomagnification of DDT had occurred to such a degree that bird populations (including the bald eagle) were beginning to suffer. The concentration of DDT was found to have had an overall increase of more than 500,000 times going from the minute amount used to protect crops to the top of the food chain. Eventually, the use of DDT was banned in the United States in 1972. Many of bird species that were affected by this chemical have since made a considerable recovery.

Now that we know what bioaccumulation and biomagnification is, lets discuss this in terms of our food supply. Farmers use a variety of chemical pesticides to control insects and other pests that can damage their crops. The pesticides help improve growing efficiencies by increasing the amount of food that can be produced from a field. The major downside to these chemicals is that they can be harmful to humans if consumed in high enough concentrations or doses. Fear of adverse health affects caused by pesticide contamination is one reason why the organic food movement was created.

Many of these pesticides are essentially harmless when a human is exposed to a single dose of residual chemical that is left on a fruit or vegetable. However, when the exposures to the chemical occur on a frequent basis, some pesticides can be bioaccumulated within our bodies. Over a long period of time, adverse health affects such as cancer can be created by the increased concentrations of these substances within our own bodies. Besides bacteria, this is the major reason that you must always wash your produce (in fact, you should always wash your Organic produce as well just to be safe).

Pesticides can also be leeched into the environment by stormwater runoff from farm fields. The chemicals can then easily become absorbed into plants and consumed by game wildlife and farm animals. The result is the biomagnification of the pesticide within the food chain. We can then later become exposed to the toxic pesticides when we eat the meat from these contaminated animals.

The Environmental Protection Agency does have strict regulations on the use of pesticides, though they have little control over produce grown outside of the US. In addition to this, the EPA and several private companies have already tested many of these chemicals to determine what the adverse health affects of over exposure is and if they can be bioaccumulated. Unfortunately though, there is plenty of work yet to be completed. There are literally thousands of chemicals that still require testing. Experiments with these substances are often very expensive and time consuming.

Buying Organic produce is probably one of the best ways to protect yourself from the adverse health impacts of pesticides. If that is not an option, or if it is just too much for your budget, try and buy locally grown fruits and vegetables instead. Better yet, try growing a garden of your own! Remember, there are many natural or chemical free alternatives to pesticides that you can use to stop pests from eating your food. For example, the state of New Jersey has a great document on safe and natural alternatives to pesticides (see resources below). And lastly, don't forget to thoroughly wash all of your produce (and your hands) before consuming or cooking them.

^{DProgram. Bioaccumulation: Why Fukushima Matters. April 27, 2011. <http://dprogram.net/2011/04/27/bioaccumulation-why-fukushima-matters/>}

^{Marietta College Department of Biology & Environmental Science. Bioaccumulation and Biomagnification. April 3, 2002. <http://www.marietta.edu/~biol/102/2bioma95.html>}

^{McGraw-Hill Companies, Inc. Bioaccumulation. 2011. <http://www.mhhe.com/biosci/esp/2001_gbio/folder_structure/ec/m3/s4/>}

^{National Oceanic and Atmospheric Administration. Biomagnification. 2011. <http://oceanexplorer.noaa.gov/edu/learning/player/lesson13/l13la1.html>}

^{State of New Jersey, Pesticide Control Program. Alternatives to Pesticides. 2011. <http://www.state.nj.us/dep/enforcement/pcp/administration/alternative.pdf>}

^{United States Geological Survey. Mercury in Aquatic Ecosystems. 2011. <http://toxics.usgs.gov/investigations/mercury.html>}