The animals at the top of the food chain are affected most severely. At each trophic level of the food chain, the toxins remain in the tissues of the animals – so the concentration of toxin becomes most concentrated in the body tissues of the animals at the top of the food chain.

Biomagnification occurs when slightly larger organisms called zooplankton feed upon the contaminated phytoplankton and in turn absorb POPs into their own tissues at a higher concentration. The more contaminated phytoplankton a zooplankton eats, the more pollutants it will have in its body.

It occurs when the toxic burden of a large number of organism at a lower trophic level is accumulated and concentrated by a predator in a higher trophic level. The concentration of some chemicals in the fatty tissue of top predators can be millions of times higher than the concentration in the open water.

Thus, a biomagnified toxin potentially becomes most harmful to top predators, including humans who eat meat or fish. If bioaccumulators destroy keystone species in an ecosystem, such as predators that control prey populations, it can lead to the loss or extinction of many species.

This is biomagnification, and it means that higher-level predators-fish, birds, and marine mammals-build up greater and more dangerous amounts of toxic materials than animals lower on the food chain.

DDT can only be used in the US for public health emergencies, such as controlling vector disease. Today, DDT is manufactured in North Korea, India, and China. India remains the largest consumer of the product for vector control and agricultural use.

The United States banned the use of DDT in 1972, but some countries still use the chemical. It is still in use outside the United States for the control of mosquitoes that spread malaria. DDT and its related chemicals persist for a long time in the environment and in animal tissues.

DDT is cheaper than other pesticides, more effective, and not harmful to human beings or animals. It costs only $1.44 per year to spray one house with DDT. The more toxic substitutes cost as much as 10 to 20 times more and require more frequent applications, making spraying programs prohibitively expensive.

Because DDT can travel long distances and accumulate in the body, millions of humans and animals worldwide have buildups of the chemical in their tissue, even though it may have been used on another continent. …

DDT has one of the longest residual efficacy periods of any IRS insecticide, lasting 6 to 12 months.

Common DDT-contaminated sediment remediation options include dredging, capping, and natural attenuation. Sediment washing and phytoremediation have also been used in contaminated sites.

High amounts of DDT exposure can lead to problems with the nervous system and liver. Animal studies conducted with DDT indicate very high doses may cause effects on the nervous system, kidney, liver and immune system, but it is not known if humans are affected in the same way as animals.

The most important actions you can take to reduce the PCBs and DDT in your diet are to cut back on animal fats and watch the type of fish you eat. Choose fish wisely. Check with state advisories before eating sport-caught fish or shellfish, which are often high in PCBs and DDT.

DDT is resistant to metabolism by living beings and hence tends to accumulated. The presence of DDT in a bird’s body leads to thinning of eggshells leading to death of the chicks before hatching. This explains the declining population of birds because of DDT.