Of all the pollutants being released into the environment by human activity, persistent organic pollutants – POPs – are among the most dangerous. These pesticides, industrial chemicals, or unwanted byproducts of industrial and other processes are highly toxic and long-lasting, and cause an array of adverse effects, including disease and birth defects in humans and animals. Some of the severe health impacts of POPs include cancer, damage to the central and peripheral nervous systems, reproductive disorder, and disruption of the immune system. Many of these chemicals accumulate in the fatty tissues of humans and other animals making them even more dangerous higher up the food chain