|Gambell in winter, St. Lawrence Island, Alaska. Photo by Colleen Keane|
Persistent organic pollutants (POPs) are carbon-based chemical compounds and mixtures that include industrial chemicals such as PCBs, pesticides such as DDT, and wastes such as dioxins. POPs also include other pesticides that are currently registered for use in the United States, as well as other industrial chemicals such as brominated flame retardants and perfluorinated chemicals (used for making Teflon). Currently used pesticides such as atrazine, chlorpyrifos, and methoxychlor, while not considered as persistent as other POPs, are now found in Arctic snow and seawater.
POPs released to the environment can travel through air and water to regions far distant from their original sources. POPs can concentrate in living organisms, including humans, to levels with the potential to injure human health and/or the environment even in regions far from where they are used or released.
The cold northern environment and fat-based food web of the Arctic favors the retention and accumulation of POPs. Even in minute quantities, POPs in our bodies can cause cancers, neurological and learning disabilities, hormonal (endocrine) disruption, and subtle changes to reproductive and immune systems. Children are especially vulnerable to exposures to these persistent chemicals. Exposures can occur before birth in utero, from breast milk, and during a child’s early years of rapid growth and development. Workers, people living near industrial plants, Arctic communities, and Indigenous peoples who rely on traditional foods often bear the greatest burden of chemical contamination.
To reduce and eliminate POPs in the Arctic, Alaska Community Action on Toxics supports strong implementation of the Stockholm Convention, a legally-binding United Nations treaty to ban known and potential POPs from global use.
Common Properties of Persistent Organic Pollutants (POPs)i
As a general rule, POPs have a number of common properties:
- POPs are persistent in the environment and they resist degradation through physical, chemical, or biological processes;
- POPs generally are semi-volatile and they evaporate relatively slowly. Persistent substances with this property tend to enter the air, travel long distances on air currents, and then return to earth. The colder the climate, the less POPs tend to evaporate, resulting in their accumulation in regions such as the Arctic, thousands of miles 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.
Global Transport: the “Grasshopper Effect”
Accumulation of persistent organic pollutants (POPs) in northern latitudes is a well-documented phenomenon. This is thought to occur for a variety of reasons. In a process known as global distillation, prevailing ocean and wind currents bring contaminants to the Arctic where they are subsequently trapped by the cold climate. This process is often referred to as the “grasshopper effect,” as chemicals repeatedly evaporate and condense while in their journey toward the Arctic. POPs accumulate in the North because the cold climate causes low evaporation rates, thereby decreasing the grasshopper effect.
Migratory animals are thought to offload their body burdens into Arctic ecosystems through excretion of wastes and during decomposition. The large rivers that empty into Arctic waters contribute as well. The Arctic appears to have a greater capacity for storage of POPs as compared to other regions; therefore, once POPs enter the Arctic, they are readily incorporated within biological systems. POPs are readily stored in the oils and fats of living organisms. All of these forces contribute to a growing burden of pollutants in Arctic air, water, animals, and humans.
Studies, such as the Arctic Monitoring and Assessment Programme (AMAP) 2011 Assessment of Mercury in the Arctic, has shown that toxic mercury levels found in Arctic wildlife is high above natural levels, and the levels are rising at a disturbing rate.
Mercury is a highly toxic element, that is present in liquid form at standard temperatures. The element is absorbed and accumulated in the food chain, causing problems for top-level predators and humans. Among the symptoms for mercury poisoning is birth defects and neurological damage.
Although mercury is present in our environment, most of the rising levels are attributed to mining and burning of coal and oil. Pollution is occurring world-wide and transported by winds and ocean currents to the Arctic.
Owing to their traditional way of life, and reliance on foods obtained from fishing and hunting, indigenous peoples of the Arctic are especially vulnerable to contaminants present in the Arctic environment. From long-range transport from rest of the World, persistent pollutants are present in the food-chains of the Arctic and gets accumulated at the top level – in animals such as whales and seals. Mercury and other heavy metals, persistent organic pollutants such as PCB and DDT (even though they are being faced out) are examples of threats to the health and traditional lifestyles. A change in diet to imported foods create a new set of problems, including a loss of traditions, reliance on outside support and nutrient deficiencies.