Persistent organic pollutants (POPs) are a class of highly hazardous chemical pollutants that are recognized as a serious, global threat to human health and to ecosystems. POPs are substances that specifically:

• remain intact for exceptionally long periods of time (many years);
• become widely distributed throughout the environment as a result of natural processes involving soil, water and, most notably, air;
• accumulate in living organisms including humans, and are found at higher concentrations at higher levels in the food chain; and
• are toxic to both humans and wildlife.

Some POPs are pesticides; some are industrial chemicals; and some are unintentionally produced byproducts that are formed during certain combustion and chemical industry processes. Some examples of POPs are DDT, lindane, PCBs and dioxins.

POPs are widely present in the environment in all regions of the world. Every person carries a body burden of POPs, mainly in his or her fatty tissues. Most fish, birds, mammals and other forms of wildlife are also contaminated with POPs.

POPs in the environment pollute the everyday food supply, especially fish, meat, butter and cheese. When people eat POPs-contaminated foods, the POPs accumulate in their fatty tissue. Mothers pass on POPs from their own bodies to their offspring. In humans and other mammals, POPs enter and contaminate the fetus while it is still in its mother’s womb. Since breast milk also contains POPs, infants are further exposed to POPs while nursing.* In non-mammal species, POPs are passed from the mother to offspring though the eggs.

POPs have the potential to harm humans and other organisms even at concentrations that are commonly found in ordinary foods. There is good medical evidence linking the following human illnesses and disabilities to one or more of the POPs:

• Cancers and tumors including soft tissue sarcoma, non-Hodgkin’s lymphoma, breast cancer, pancreatic cancer and adult onset leukemia;
• Neurological disorders including attention deficit disorder, behavior problems such as aggression and delinquency, learning disabilities and impaired memory;
• Immune suppression;
• Reproductive disorders including abnormal sperm, miscarriages, pre-term delivery, low birth weight, altered sex ratios in offspring, shortened period of lactation in nursing mothers and menstrual disorders; and
• Other diseases including increased incidence of type II diabetes, endometriosis, hepatitis and cirrhosis.

POPs are most harmful to the developing fetus, causing health impairments such as neurological disorders and deficits, which continue throughout the child's entire life. POPs are also particularly harmful to infants, children, women, the ill-nourished and some other populations.

* Note: It is recommended that mothers nonetheless continue to nurse their infants. Important nutrients that are contained in breast milk provide the infant with positive benefits that generally outweigh the negative impacts of the POPs. Therefore, mothers are still encouraged to breastfeed unless otherwise instructed by their physician.

'Poisons Without Passports'

POPs concentrate in living organisms to levels where they can injure human health and the environment. POPs do their damage even in regions like the Arctic, far from where they are used or released. Additionally, they tend to accumulate in colder regions, and as global temperatures rise, most and more POPs will be released back into ecosystems.

POPs Common Characteristics

As a general rule, POPs have a number of common properties:

• POPs are persistent in the environment. They resist degradation or breakdown through physical, chemical, or biological processes;
• POPs generally are semi-volatile. They evaporate relatively slowly but when they enter the air, they travel long distances on air currents. They return to earth in rain and snow in the colder areas of the globe, resulting in their accumulation in regions such as the Arctic, thousands of kilometres away from their original sources;
• POPs generally have low water solubility (they do not dissolve readily in water) and high lipid (fat) solubility (they do dissolve easily in fats and oils). Persistent substances with these properties bioaccumulate in fatty tissues of living organisms. In the environment, concentrations of these substances can increase by factors of many thousands or millions as they move up the food chain; and
• POPs have the potential to injure humans and other organisms even at the very low concentrations at which they are now found in the environment, wildlife and humans. Some POPs in extraordinarily small amounts can disrupt normal biological functions, including the activity of natural hormones and other chemical messengers, triggering a cascade of potentially harmful effects.