Synthetic pesticides are man-made chemicals designed specifically to kill or repel pests. They are used mainly in agriculture, though their use is not limited to the field but also in other industries and also for domestic use.

The use of synthetic pesticides began in the United States of America (USA) in the 1930s. Its popularity soared after World War II and its use became widespread all over the USA.

Carson turned her attention to conservation in the late 1950s. She saw the use of pesticides as the root of the problem to many environmental concerns she observed, particularly DDT. It was promoted by government and industry for agricultural and domestic use. It was used in widespread urban aerial sprays. There were many federal proposals for widespread pesticide spraying, which Carson followed closely.

Effects & Environmental Concerns

Carson argues that the use of pesticides are generally detrimental to the environment. Their effects are rarely limited to target pests and often end up killing or affecting other organisms and affecting the ecosystem balance.

Bioaccumulation

Once these pesticides entered the biosphere… they not only killed bugs but also made their way up the food chain to threaten fish and bird populations and could eventually sicken children.

Bioaccumulation is the process by which a chemical builds up in an organism. The main environmental problem with chemicals like DDT is that they are not broken down easily by the natural environment. Once it is sprayed on a certain area of land, it can stay there and continue killing insects for years. If it is sprayed on a lake or water body, its effects can be much more dire. It is absorbed by the plants and animals in the lake. As the creatures in the lake feed on their prey, they accumulate the chemical in their bodies from the organisms that they eat. This way, the chemical accumulates upwards of a food chain. The predator sitting at the top of the food chain will therefore have the highest concentration of the chemical in their bodies.

Health Effects

Silent Spring… made a powerful case for the idea that if humankind poisoned nature, nature would in turn poison mankind.

As chemicals accumulate up the food chain, they would eventually find their way into our bodies, mankind being one of the top predators of the food web. DDT has been killing off harmless insects and have been accumulated in the bodies of birds that have eaten organisms which have taken up the chemical in their bodies. Some of DDT’s most harmful effects are seen in predatory birds. Reports from the 1970s describe behavioral and reproductive abnormalities found among predatory birds like the balding eagle, particularly the thinning of eggshells which reduce offspring and drive some species to near extinction.

The effects of DDT on humans at low doses are unknown. As time progresses, there has been mounting evidence of health effects on DDT and its breakdown product, DDE on humans, including and not limited to: male infertility, liver, reproductive and nervous system damage, and miscarriage. Exposure in high doses can cause tremors, vomiting and seizures. It has also been identified as a possible carcinogen.

Modern-day use of pesticides

In response to the concern raised by Silent Spring and consequent scientific findings of the adverse effects of DDTs and similar synthetic chemicals on the environment, the USA banned DDT in the 1970s. However, it is still used outside the USA to control mosquitoes that spread malaria, especially in countries like Africa. These chemicals stay in the environment for a long time and continue to accumulate in the bodies of different organisms.