Persistent Organic Pollutants (College Board AP® Environmental Science): Study Guide

What are persistent organic pollutants?

• Persistent organic pollutants (POPs) are a group of toxic chemicals that are resistant to breakdown

• They are synthetic, carbon-based chemicals that persist in the environment for decades

• These toxins then accumulate in organisms (bioaccumulation) and become more concentrated as they move up the food chain (biomagnification)

• POPs can be naturally, intentionally or unintentionally produced

Sources of POPs

• Some POPs, such as dioxins, can be naturally produced by volcanic eruptions and forest fires

• The industrial boom of post-World War II introduced hundreds of synthetic chemical POPs for commercial usage

• Many of these chemicals helped with pest and disease management, crop productivity, and industry

• Examples of intentionally produced POPs include:

  • Pesticides, such as DDT (dichlorodiphenyltrichloroethane), which is still produced to control mosquitoes that carry malaria

  • Industrial chemicals, such as PCBs (polychlorinated biphenyls), that are used as lubricants and coolants in electrical equipment

  • Solvents in paints and lubricants

• Unintentionally produced POPs include dioxins and furans that are produced as byproducts of

  • industrial processes

  • burning waste such as municipal and medical waste incineration and backyard burning of trash

Distribution of POPs

• POPs can travel in air, water and soil and have been found in remote places far from the point of origin

• This process is called 'global distillation' or the 'grasshopper effect'

• Rivers, seas, and currents can all carry POPs

  • For instance, PCBs discharged into rivers by an industrial plant have the potential to travel downstream and end up in the ocean

• POPs have the ability to build up in animal adipose (fat) tissues and move up the food chain

  • A kingfisher eats trout contaminated with POP

  • Over time, the kingfisher will have higher levels of POP in its body than the fish did

• POPs can stay in soil and sediment for decades or even centuries after being deposited on land and in aquatic bodies

  • POPs are difficult to remove from the soil as they easily bind to the organic matter

  • Organisms that consume the soil then become contaminated

• The wind can carry POPs over vast distances

  • For instance, the jet stream can carry DDT used in crops in one country and deposit it in another

• The production and use of POPs is restricted and banned in some countries due to their harmful effects

Effects of POPs on organisms

• Exposure to POPs has been linked to diseases, deformities, and declines in a variety of wildlife species, including several fish, birds, and mammals

• POPs have reproductive, developmental, behavioral, neurologic, endocrine, and immunologic health consequences in humans

  • The chemical (PCB) have accumulated in marine top predators like killer whales and polar bears, leading to immune and reproductive issues

  • Fish, birds, and mammals in and near the Great Lakes exhibit birth deformities and behavioral disorders

• The main source of POPs for people is contaminated food

• This is especially so for those who rely on traditional food such as fish, shellfish, or high-fat wild foods

  • Indigenous peoples follow diet-related cultural and spiritual traditions

  • Fishing and hunting are part of their traditional lifestyles, with no part of the catch going to waste

  • In remote areas, locally sourced subsistence food may be the only option; therefore, increasing their risk to exposure of POPs

• Exposure to POPs from drinking contaminated water and touching chemicals is less common

• People and other mammals can pass POPs to their offspring through the placenta and breast milk

• POPs and other pollutants are especially harmful to the elderly, children, and people with compromised immune systems

• POPs can cause reproductive issues

  • The bald eagle suffered a sharp decline in the 1960s and 70s due to the long-term effects of DDT thinning their eggshells so much that they could not produce live offspring

• POPs can have significant economic impacts on industries that rely on natural resources, such as fishing and tourism

• Social impacts include loss of livelihoods and community displacement