Environmental Pollution and Disease

1. What are the differences between persistence, bio-accumulation and biological magnification? How are these chemical characteristics interrelated?

There are three different characteristics of DDT, all of which contribute to its impact on the overall environment. With persistence, the chemical structures of synthetic pesticides not found in nature contribute to how they take many years to break down into less toxic forms. This allows certain chemicals with extreme stability to carry on for a long period of time before eventually breaking down.

It is thanks to the bio-accumulation of high concentration levels of pesticides that allows said pesticides to be stored in an organism's body, when it is not metabolized or excreted for a period of time. This buildup of a persistent toxic substance is often located in the fatty tissues.

Finally, Biological Magnification is the increased concentration of toxic chemicals in the tissues of organisms that are at a higher level in the food web. Since organisms on the higher levels tend to have greater concentrations of bio-accumulated pesticide in their bodies than those who are on the lower chains, a species that is lower on the food chain is able to retain a lower consumption of pesticides. For example, a food chain in Long Island was sprayed with DDT over a period of years for mosquito control, and while the algae and other plankton contained 0.04 ppm, the shrimp that grazed on the plankton had a DDT concentration of 0.16 ppm in it's tissues. This lead all the way up to the top carnivores, each of them containing 75.5 ppm levels from consuming the levels below it.

2. How did the 1980 chemical spill in Lake Apopka affect alligators?

During the chemical spill of Lake Apopka, Florida, DDT and other harmful agricultural chemicals were released upon the lake-water. The popular habitat of male alligators was greatly affected, and because DDT has high estrogenic properties, this caused their testosterone levels to decrease. This lead to their reproductive organs either becoming too small or becoming feminized, and so the mortality rate for eggs in Lake Apopka was extremely high, reducing the alligator population for many years.