Back More
Salem Press

Table of Contents

Encyclopedia of Environmental Issues, 3rd Edition

Pesticides and herbicides (environmental impact)

by D. R. Gossett

Fields of Study: Agriculture; Animal Husbandry; Biochemistry; Biology; Botany; Chemistry; Ecology; Ecosystem Management; Environmental Sciences; Environmental Studies; Forestry; Horticulture; Waste Management;

Key Concepts: Chemicals designed to kill or inhibit the growth of unwanted organisms

Although the use of pesticides, including herbicides, has been beneficial to humankind, enabling increased crop yields and helping to prevent disease, many of the chemicals that have been used to kill pests have had detrimental effects on the environment as well as direct negative effects on human health.

Overview

The major types of pesticides in common use are insecticides (to kill insects), nematocides (to kill nematodes), fungicides (to kill fungi), herbicides (to kill weeds), and rodenticides (to kill rodents). Although the use of pesticides has mushroomed since the introduction of monoculture (the agricultural practice of growing only one crop on a large amount of land), the application of chemicals to control pests is by no means new. The use of sulfur as an insecticide dates to before 500 BCE. Salts from heavy metals such as arsenic, lead, and mercury were used as insecticides from the fifteenth century until the early part of the twentieth century, and residues of these toxic compounds are still being accumulated in plants that are grown in soil where these materials were used. In the seventeenth and eighteenth centuries, natural plant extracts such as nicotine sulfate from tobacco leaves and rotenone from tropical legumes were used as insecticides. Other natural products, such as pyrethrum from the chrysanthemum flower, garlic oil, lemon oil, and red pepper, have long been used to control insects.

Although the use of pesticides, including herbicides, has been beneficial to humankind, enabling increased crop yields and helping to prevent disease, many of the chemicals that have been used to kill pests have had detrimental effects on the environment as well as direct negative effects on human health.

Types of Pesticides

The major types of pesticides in common use are insecticides (to kill insects), nematocides (to kill nematodes), fungicides (to kill fungi), herbicides (to kill weeds), and rodenticides (to kill rodents). Although the use of pesticides has mushroomed since the introduction of monoculture (the agricultural practice of growing only one crop on a large amount of land), the application of chemicals to control pests is by no means new. The use of sulfur as an insecticide dates to before 500 BCE. Salts from heavy metals such as arsenic, lead, and mercury were used as insecticides from the fifteenth century until the early part of the twentieth century, and residues of these toxic compounds are still being accumulated in plants that are grown in soil where these materials were used. In the seventeenth and eighteenth centuries, natural plant extracts such as nicotine sulfate from tobacco leaves and rotenone from tropical legumes were used as insecticides. Other natural products, such as pyrethrum from the chrysanthemum flower, garlic oil, lemon oil, and red pepper, have long been used to control insects.

An American farmworker takes health precautions while preparing pesticides for use on crops. (USDA)

ENVIs2e_p0968_1.jpg

In 1939, the discovery of the utility of Dichloro-diphenyl-trichloroethane (DDT) as a strong insecticide opened the door for the development of a wide array of synthetic organic compounds to be used as pesticides. Chlorinated hydrocarbons such as DDT were the first group of synthetic pesticides. Other commonly used chlorinated hydrocarbons include aldrin, endrin, lindane, chlordane, and mirex. Because of the low biodegradability and long persistence in the environment of these compounds, their use was eventually banned or severely restricted in the United States. Organophosphates such as malathion, parathion, and methamidophos replaced the chlorinated hydrocarbons. These compounds biodegrade in a fairly short time but are generally much more toxic to humans and other animals than the compounds they replaced. In addition, they are water soluble and, therefore, more likely to contaminate water supplies. Carbamates such as carbaryl, maneb, and aldicarb have also been used in place of chlorinated hydrocarbons. These compounds biodegrade rapidly and are less toxic to humans than organophosphates, but they are also less effective in killing insects.

Herbicides, which are used specifically to kill or retard the growth of unwanted plant life, are classified according to the ways in which they work rather than their chemical composition. As their name suggests, contact herbicides such as atrazine and paraquat kill when they come into contact with a plant’s leaf surface; these herbicides generally work by disrupting the photosynthetic mechanism. Systemic herbicides such as diuron and fenuron circulate throughout the plant after being absorbed. They generally mimic the plant hormones and cause abnormal growth to the extent that the plant can no longer supply sufficient nutrients to support growth. Soil sterilants such as triflurain, diphenamid, and daiapon kill microorganisms necessary for plant growth and also act as systemic herbicides.

Pesticide Use

In the United States, approximately 55,000 different pesticide formulations are available, and pesticide use grew by an estimated 183 million kilograms annually from 1996 to 2011. Fungicides account for 7 percent of all pesticides used by farmers, insecticides account for 6 percent, and herbicides account for 76 percent. These pesticides are used primarily on four crops: soybeans, wheat, cotton, and corn. In 2007, the annual expenditure on pesticides each year in the United States had reached approximately $8 billion. On a per-unit-of-land basis, home owners apply approximately five times as much pesticide to their yards as farmers do to their fields. Worldwide, more than 2.5 tons of pesticides are applied each year. Most of these chemicals are applied in developed countries, but the amount of pesticides being used in developing countries is rapidly increasing. Total annual expenditure on pesticides worldwide is nearly $40 billion. A market research report on the use of biopesticides, which are pesticides that are made from natural materials such as plants, animals, and bacteria, valued the global biopesticide market at $37.5 billion in 2011 and estimated the 2017 market value to reach $65.3 billion.

The use of pesticides has had a beneficial impact on the lives of humans by increasing food production and reducing food costs. Even with pesticides, insects and other pests reduce the world’s potential food supply by more than 50 percent. Without pesticides, the losses would be much higher, resulting in increased starvation and higher food costs. Pesticides also increase the profit margin for farmers. It has been estimated that for every dollar spent on pesticides, farmers experience an increase in yield worth three to five dollars. Pesticides appear to work better and faster than alternative methods of controlling pests. These chemicals can rapidly control most pests, are cost-effective, can be easily shipped and applied, and have a long shelf life in comparison with alternative methods. In addition, farmers can quickly switch to different pesticides if the pests they are trying to kill develop genetic resistance to a given pesticide.

Perhaps the most compelling argument for the use of pesticides is the fact that pesticides have saved lives. It has been suggested that since the introduction of DDT, the use of pesticides has prevented approximately seven million premature human deaths from insect-transmitted diseases such as sleeping sickness, bubonic plague, typhus, and malaria. It is likely that even more lives have been saved from starvation because of the increased food production resulting from the use of pesticides. It has been argued that this one benefit far outweighs the potential environmental and health risks of pesticides. In addition, new pesticides are continually being developed, and safer and more effective pest control may be available in the future.

Environmental Concerns

An ideal pesticide would have the following characteristics: It would not kill any organism other than the target pest; it would in no way affect the health of nontarget organisms; it would degrade into nontoxic chemicals in a relatively short time; it would prevent the development of resistance in the organism it is designed to kill; and it would be cost-effective. No pesticide currently available meets all of these criteria, however, and, as a result, a number of environmental problems have developed from the use of pesticides. One of these problems is broad-spectrum poisoning. Most, if not all, chemical pesticides are not selective. In other words, they kill a wide range of organisms rather than just the target pest. The extermination of beneficial insects, such as bees, ladybugs, and wasps, may result in a range of problems, including reduced pollination and explosions in populations of unaffected insects.

When DDT was first used as an insecticide, many people believed that it was the perfect solution for controlling many insect pests. Initially, DDT dramatically reduced the number of problem insects; within a few years, however, a number of insect species had developed genetic resistance to the chemical and could no longer be controlled with it. By the 1990s approximately two hundred insect species had genetic resistance to DDT. Other chemicals were designed to replace DDT, but many insects also developed resistance to these newer insecticides. As a result, although many synthetic chemicals have been introduced into the environment, the pest problem is still as great as it ever was.

Depending on the types of chemicals they contain, pesticides remain in the environment for varying lengths of time. Chlorinated hydrocarbons, for example, can persist in the environment for up to fifteen years. From an economic standpoint, this can be beneficial because the pesticide has to be applied less frequently, but from an environmental standpoint, it can be detrimental. In addition, many pesticides degrade in such a way that their breakdown products, which may also persist in the environment for long periods of time, are often toxic to other organisms.

Pesticides may concentrate in animals as they move up the food chain. All organisms are integral components of at least one food pyramid. While a given pesticide may not be toxic to species at the base, it may have detrimental effects on organisms that feed at the apex because the concentration increases at each higher level of the pyramid, a phenomenon known as biomagnification. With DDT, for example, some birds can be sprayed with the chemical without any apparent effect, but if these same birds eat fish that have eaten insects that contain DDT, they lose the ability to metabolize calcium properly. As a result, they lay soft-shelled eggs, which causes the death of most of their offspring. DDT was banned in the United States in 1972.

Pesticides can also be hazardous to human health. Many pesticides, particularly insecticides, are toxic to humans, and thousands of people have been killed by direct exposure to high concentrations of these chemicals. Many of those who have died have been children who were accidentally exposed to toxic pesticides because of careless packaging and storage. Numerous agricultural laborers, particularly in developing countries where there are no stringent guidelines for the handling of pesticides, have also died as a result of direct exposure to these chemicals. Workers in pesticide factories are also a high-risk group, and many of them have been poisoned through job-related contact with the chemicals. Pesticides have also been suspected of causing long-term health problems such as cancer, and some pesticides have been classified as carcinogens by the US Environmental Protection Agency.

Further Reading

1 

Carson, Rachel. Silent Spring. 50th anniversary ed. Boston: Houghton, 2012.

2 

Connell, Des W. Basic Concepts of Environmental Chemistry. 2nd ed., CRC, 2005.

3 

Edwards, C. A., editor. Environmental Pollution by Pesticides. Springer Science & Business Media, 2013.

4 

“Global Markets for Biopesticides.” BCC Research, Nov. 2012, www.bccresearch.com/market-research/chemicals/biopesticides-market-trends-chm029d.html. Accessed 29 Nov. 2016.

5 

Miller, G. Tyler, Jr., and Scott Spoolman. Living in the Environment: Principles, Connections, and Solutions. 18th ed., Cengage, 2015.

6 

Monaco, Thomas J., Stephen C. Weller, and Floyd M. Ashton. Weed Science: Principles and Practices. 4th ed., 2002.

7 

Ohkawa, H., H. Miyagawa, and P. W. Lee, editors. Pesticide Chemistry: Crop Protection, Public Health, Environmental Safety. Wiley-VCH, 2007.

8 

Whorton, James C. Before Silent Spring: Pesticides and Public Health in Pre-DDT America. Princeton UP, 2015.

Citation Types

Type
Format
MLA 9th
Gossett, D. R. "Pesticides And Herbicides (environmental Impact)." Encyclopedia of Environmental Issues, 3rd Edition, edited by Richard Renneboog, Salem Press, 2019. Salem Online, online.salempress.com/articleDetails.do?articleName=ENVIs2e_0527.
APA 7th
Gossett, D. R. (2019). Pesticides and herbicides (environmental impact). In R. Renneboog (Ed.), Encyclopedia of Environmental Issues, 3rd Edition. Salem Press. online.salempress.com.
CMOS 17th
Gossett, D. R. "Pesticides And Herbicides (environmental Impact)." Edited by Richard Renneboog. Encyclopedia of Environmental Issues, 3rd Edition. Hackensack: Salem Press, 2019. Accessed September 17, 2025. online.salempress.com.