An Introduction to Persistent Organic Pollutants

Persistent organic pollutants are chemicals that are persistent in the environment and that have adverse health or environmental effects. Some of these chemicals are pesticides such as DDT and Chlordane, industrial chemicals such as PCBs and industrial byproducts such as dioxins and furans.

These substances, because of their chemical structure, resist chemical and biological breakdown in the environment and consequently can accumulate in organisms. Through bioaccumulation, animals higher in the food chain are more likely to have higher concentrations of these pollutants, often to the degree that the substances cause toxic effects. Since humans are often at the top of the food chain, POPs are a concern for human health. An example of this is the accumulation of PCBs in Great Lakes fish: studies have shown adverse neurological effects in people who eat these fish.

POPs can also travel long distances by air or in water, so that they are found in ecosystems in which they have never been used and far from their source. Animals of the Canadian Arctic have significant levels of PCBs, organochlorine pesticides (like DDT) and metals, and this poses a health risk to the human population that relies on these animals as a food source.

The effects of these chemicals on wildlife populations have been widely studied and clearly pose a hazard. Effects on humans have also been found in numerous studies. POPs have been found to have effects on the developing nervous system, some are carcinogenic, and some probably have effects on the endocrine and immune systems. For these reasons, The United Nations Environment Programme has identified twelve POPs that need to be reduced and eliminated to protect human health.

More Information on POPs

Physicians for Social Responsibility has excellent information on this issue. Health Canada has a web page on the human health effects of PCBs and information on dioxins and furans. Many POPs are pesticides of the organochlorine type. More information on pesticides can be found on our pesticides page.

The Ontario College of Family Physicians Environmental Health Committee has developed a set of modules based on clinical cases which can be used for self-learning or for teaching physicians. These are available on the web for free, including a module on POPs. The ATSDR (the US government’s Agency for Toxic Substances and Disease Registry) has volumes of information on chemicals and their effects on health.


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