Persistent organic pollutants

Persistent organic pollutants (POPs) are a group of chemicals that have been labelled as being the most dangerous in the world. They are highly toxic, causing an array of adverse effects, notably death, disease and birth defects among humans and animals.

The 12 main persistant chemicals include eight pesticides (aldrin, chlordane, DDT, dieldrin, endrin, heptachlor, mirex and toxaphene), two types of industrial chemicals (polychlorinated biphenyls or PCBs and hexachlorobenzene), and two families of manufacturing by-products (dioxins and furans). Persistant organic pollutants are carbon-based compounds and mixtures with four characteristics; high toxicity, persistence, affinity to fat, and a propensity to evaporate and travel distances.

POPs are having a devastating effect on wildlife and biodiversity across the planet. Wild species show signs of disrupted sexual development and a diminished ability to reproduce. Some species have disappeared altogether because of total reproductive failure.

POPs are pollutants that are likely to lead to exposures of concern to humans and the environment at points remote from the site of release. There is considerable evidence of long range dispersion in the Arctic, where fish, birds and mammals high on the food chain are being exposed at high levels of POPs. Native Inuits, who have a diet that is high in local fish and marine mammals, have levels that exceed the recommended daily intake of these chemicals. It is also clear that POPs-containing air pollution travels long distances and across borders.

Breast-fed children are at the earliest contaminated with persistant organic pollutants (POPs) from their mother's milk, where they naturally collect in the fat content. Most of the POPs are endocrine disruptors; that is, they have been shown to cause hormonal problems through a disruption of the endocrine system, particularly for exposures in the womb and in young children. A number of studies suggest that the effects of PCBs and other of these chemicals can be serious at low levels. The presence of POPs in humans are now recognized causes of immune dysfunction, neurological and behavioural abnormalities and reproductive disorders.

Problems with persistant organic pollutants were first identified in the 1940's and early 1950's just as the "chemical revolution" gained momentum. The production and release of POPs into the environment poses a number of serious problems. POPs do not degrade easily and because of their nature can travel thousands of miles in complex journeys on air, water currents and through the food web, creating international problems. In the 1940's scientists found traces of the man-made pesticide, DDT in human fat and the milk of nursing mothers. Further studies in the 1950's found they had drastic effects upon bird populations and caused thinning in eggshells. While many of the worst chemicals are now banned, old stockpiles of pesticides and industrial chemicals continue to leak, leach and evaporate into the environment from inadequate or deteriorating storage containers.

Acute exposure to POPs in tropical agriculture has caused large numbers of human deaths and injuries, including severe nervous system and liver damage. Further studies link these chemicals to cancers, and new longer term effects, from low level background contamination, create "endocrine disruption," affecting the health and intelligence of the next generation. These endocrine disruptors interfere with the body's own hormones and during prenatal life can alter fetal development, undermine intelligence development, and interfere with the development of the imune system.

POPs are fat-soluble toxic chemicals that do not easily degrade, persist for many years in the environment, concentrate up the food chain, and accumulate in animal and human tissues. They often end up thousands of kilometres from where they are used or released. The growing evidence that some POPs can have serious human health effects has pushed governments to collective action. Although POPs include a wide range of chemicals, much recent research and regulatory action focuses on the industrial PCBs, polychlorinated dioxins and furans (unwanted by-products of various industrial processes) and pesticides such as DDT, chlordane and heptachlor. Despite restrictions on the use of these chemicals in many developed countries, they are still manufactured there for export and remain widely used in developing countries.

Canadain beluga whales have been found with more than 10 times the hazardous waste level of POPs in their bodies. The species has developed several kinds of cancer, twisted spines and skeletal disorders, ulcers, pneumonia, bacterial and viral infections, thyroid abnormalities, all directly linked to the presence of POPs in their environment. Similarly, alligators, fresh water trout, minks and otter all display afflictions linked to the presence of POPs. Further studies reveal a reduction in animal immune system defences, making species vulnerable to disease, such as those epidemic which affected seals, dolphins and porpoises in the 1980s and 1990s. Behavioral effects caused by POPs have been noted in nesting bird populations affecting the hatching and survival of the chicks.