Agrochemicals

Many important benefits are achieved by the use of agrochemicals. These are largely associated with increased yields of plant and animal crops, and less spoilage during storage. These benefits are substantial. In combination with genetically improved varieties of crop species, agrochemicals have made important contributions to the successes of the "green revolution." This has helped to increase the food supply for the rapidly increasing population of humans on Earth.

However, the use of certain agrochemicals has also been associated with some important environmental and Agrochemical spraying in a Michigan orchard. © Ken Wagner/Phototake NYC. Reproduced by permission. ecological damages. Excessive use of fertilizers, for example, can lead to the contamination of groundwater with nitrate, rendering it unfit for consumption by humans or livestock. Water containing large concentrations of nitrate can poison animals by immobilizing some of the hemoglobin in blood, reducing the ability to transport oxygen. In addition, the run-off of agricultural fertilizer into streams, lakes, and other surface waters can cause an increased productivity of those aquatic ecosystems, a problem known as eutrophication. The ecological effects of eutrophication can include an extensive mortality of fish and other aquatic animals, along with excessive growth of nuisance algae, and an off-taste of drinking water.

The use of pesticides can also result in environmental problems. As was previously noted, pesticides are used in agriculture to reduce the abundance of species of pests (that is, the "targets") to below a level of acceptable damage, which is economically determined. Unfortunately, during many uses of pesticides in agriculture, the exposure of other organisms, including humans, is not well controlled. This is especially true when entire fields are sprayed, for example, when using application equipment drawn by a tractor, or mounted on an airplane or helicopter. During these sorts of broadcast applications, many non-target organisms are exposed to the pesticide. This occurs on the treated site, and also on nearby off-sites as a result of "drift" of the sprayed agrochemical. These non-target exposures cause many unnecessary poisonings and deaths of organisms that are not agricultural pests.

In addition, there is a widespread, even global contamination of the environment with some types of persistent pesticides, especially with organochlorines such as DDT, dieldrin, and aldrin. This contamination involves the widespread presence of pesticide residues in virtually all wildlife, well water, food, and even in humans. Residues of some of the chemicals used in animal husbandry are also believed by some people to be a problem, for example, when traces of antibiotics and bovine growth hormones occur in consumer products such as meat or milk.

Some of the worst examples of environmental damage caused by pesticides have been associated with the use of relatively persistent chemicals, such as DDT. Most modern usage of pesticides involves chemicals that are less persistent than DDT and related chlorinated hydrocarbons. However, severe damages are still caused by the use of some newer pesticides. In North America, for example, millions of wild birds have been killed each year as a non-target effect of the routine use of carbofuran, an agricultural insecticide. This is a substantial ecological price to pay for the benefits associated with the use of that agrochemical.

The use of some pesticides is also risky for humans. About one million pesticide poisonings occur globally every year, resulting in 20,000 fatalities. About one-half of the human poisonings occur in poorer, less-developed countries, even though these places account for only 20% of the world's use of pesticides. This disproportionate risk is due to greater rates of illiteracy in poorer countries, and to lax enforcement of regulations concerning the use of pesticides.

There have been a few examples of pesticides causing extensive toxicity to humans. The most famous case occurred at Bhopal, India, in 1984, in the vicinity of a factory that was manufacturing an agricultural insecticide. In that case, there was an accidental release of about 45 tons (40 tonnes) of deadly methyl isocyanate vapor to the atmosphere. This agrochemical-related emission caused the deaths of about 3,000 people, and more than 20,000 others were seriously injured.

These and other environmental effects of the use of some agrochemicals are unfortunate consequences of the application of these chemical tools to deal with agricultural problems. Researchers are constantly searching for non-chemical ways of dealing with many of these agricultural needs. Much attention is being paid, for example, to developing "organic" methods of enhancing soil fertility and dealing with pests. Unfortunately, economically effective alternatives to most uses of agrochemicals have not yet been discovered. Consequently, modern agricultural industries will continue to rely heavily on the use of agrochemicals to manage their problems of fertility, soil quality, and pests.