In 2001, over 3 billion dollars worth of insecticides were purchased in the US, representing over one-third of the total world market. Nearly $1.3 billion was spent on insecticides for home and garden use, nearly as much as that used for commercial agriculture. Over 122 million pounds of the active ingredients in insecticides were used in the US in 2000.
However, active ingredients typically make up 1 percent or less of the volume in an insecticide product—the rest are so-called "inert ingredients"—so the total amount of insecticide products used in the US in 2000 likely exceeded 10 billion pounds. Fifty-nine million US households used some form of insecticide in 2000, or about 56 percent of all households.
Given the widespread use of insecticides in US households and the sheer volume of the chemicals that are released into homes, gardens, and lawns, it's important to remember that they're poisonous, highly-toxic substances. Because of the increased health risks associated with using chemical bug sprays, usage should be absolutely minimized or avoided altogether. Exposure to small amounts of these chemicals can cause serious health problems in humans (especially children) and pets, and even those who don't use bug sprays can suffer from their pervasive use. For example:
- Using pesticides in and around the home can cause a 60 percent increase in the likelihood of children developing neuroblastoma, a serious form of cancer.
- Children who have been exposed to household insecticides and professional extermination methods within the home are three to seven times more likely to develop non-Hodgkin's lymphoma (NHL) compared with children who have not been exposed to pesticides.
- Children living in pesticide-treated homes have nearly a four-times greater than normal risk of developing leukemia. Children living in homes where pesticides are also used in the garden have a risk of developing leukemia 6.5 times greater than normal.
- In a study of household dogs, the risk of developing bladder cancer increased from topical insecticide use. When dogs were exposed to one to two topical pesticide applications per year, there was a 60 percent increased risk of bladder cancer. When the animals were exposed to more than two pesticide applications per year, the risk of developing bladder cancer was 3.5 times greater.
- Prostate and brain cancer risk doubles, and lung cancer risk triples among pesticide applicators (i.e. people employed in the application of pesticides, in this case for 20 years or more). 
Miniscule amounts of some insecticides can be devastating to wildlife like birds and fish and can disrupt ecosystems. Since some insecticides can persist for years, a single application can continue to add toxins to the air, soil, and water around your home for a long time. These chemicals can even harm endangered or threatened species.
Animal species that experience long-term exposure may have health and reproductive problems. Insecticides may also harm the habitat of endangered species because of drift, runoff, or leachates that may contaminate the water, soil, or vegetation used by the species. Both the bald eagle and the peregrine falcon became endangered because of the use of the insecticide DDT, but populations rebounded after use of the insecticide was banned.
Using insecticides on your garden, lawn, or farm may eventually make your insect problems worse. Insects can develop resistance to a particular insecticide, and secondary outbreaks can occur because using insecticides can kill beneficial insects that would otherwise keep unwanted insect populations in check.
Insecticides are used globally in indoor pest management, personal bug sprays, gardening, landscaping, and agriculture to control insect populations that would otherwise cause harm to humans, crops, and other vegetation. Insecticides are usually chemical preparations that are toxic not only to the intended target, but to other insects and animals as well. While the use of insecticides is believed to be one of the main factors behind increases in agricultural productivity during the 20th century, there is growing evidence that organic farming techniques that do not rely on chemical insecticides can meet or exceed the yields of conventional growers.
Pest control chemicals can be classified in various ways. Some are contact insecticides, while others, like systemic insecticides, are only toxic when the plant they are present on are ingested. Pesticides can also be classified by the specific populations they target, such as miticides, mulluscocides, and nematacides.
There are naturally-occurring pesticides like nicotine in tobacco and pyrethrin in chysanthemums, and a wide variety of biopesticides derived from natural substances. These include microbial pesticides, plant-incorporated protectants, and biochemical pesticides.
Chemical insecticides include organochlorides (DDT, for example), organophosphates, carbamates, and inorganic insecticides (typically substances based on arsenic, copper, flourine, and sulfur). The active ingredients in many pesticides for use in the garden are permethrin and tetramethrin (synthetic forms of pyrethrum).
The US Environmental Protection Agency (EPA) regulates the manufacture, distribution, and labeling of insecticides in the US under the Federal Insecticide, Fungicide, and Rodenticide Act. The EPA also studies the impact of insecticides and other pesticides on the environment.
Related health issues
Lawn and gardening insecticides
The health effects of exposure to pesticides depends on the type of pesticide used and the level of exposure. Chemical pesticides and fumigants can irritate the skin or eyes, affect the central nervous system (carbamates and organophosphates), and disrupt the endocrine system; some may be carcinogens. Extreme caution should be exercised when using these products and exposure to humans and animals should be minimized.
Some popular "natural" pesticides can also be toxic to humans and animals. Pyrethrin and rotenone are two examples of natural insecticides that are poisonous to animals and humans and should be applied with caution. Permethrin, a synthetic form of pyrethrin, is a contact insecticide and as such skin contact should be avoided. As a pyrethroid pesticide, it may cause nervous system complications ranging from headaches to convulsions and loss of consciousness. Some animal studies have indicated reduced fertility and possible immune system damage to fetuses exposed to permethrin, however, this has not been observed in humans. The EPA has also classified permethrin as a likely carcinogen. Rotenone, another popular natural insecticide, is derived from a variety of tropical and subtropical plants and can cause skin irritation, kidney and liver damage, and may be implicated in Parkinson's disease.
Personal bug sprays
Insect-borne diseases infect and kill millions of people around the world every year. Mosquitoes, for example, can transmit malaria, yellow fever, dengue fever, and west nile virus. Malaria alone killed nearly 1.3 million people in 2002.
The two most widely used chemicals in personal bug sprays, DEET and permethrin, can have serious possible health implications for humans and other animals. Serious adverse reactions to DEET are relatively rare. However, health problems have been reported in conjunction with use of DEET ranging from skin and eye irritation to psychological problems and even death.
Although DEET is considered safe for use on children by the EPA, it does recommend that application be performed by an adult and that DEET should not be applied to a child's hands to reduce the risk of accidental ingestion. Pregnant women should exercise extra caution in using DEET, as research indicates that after being absorbed through the skin, it can then cross the placenta. However, there is little evidence that this causes harm to the developing fetus.
Perhaps the greatest controversy involves the insecticide DDT, or Dichloro-Diphenyl-Trichlorethane. DDT is considered to be the first "modern" pesticide, and the Swiss chemist Paul Hermann Müller was awarded the Nobel Prize in Physiology or Medicine in 1948 "for his discovery of DDT as a contact poison against several arthropods." DDT was used extensively during and after World War II to control malaria and typhus, and was used by the World Health Organiziation in 1955 in a worldwide program to eliminate malaria.
However, serious environmental implications became apparent in the 1950s, including dramatic declines in native fish and bird populations. In 1962, the book Silent Spring was published by the American biologist Rachel Carson, who alleged that DDT was a carcinogen and was hurting bird populations. The resulting public outcry resulted in a ban on using the insecticide for agricultural purposes in the US and eventually around the world.
The Stockholm Convention of 2001 bars the use of DDT except in public health programs, and in 2006 the World Health Organization announced that it would use DDT as one of its three main tools used to combat malaria. The controversy over DDT use continues today, with public health advocates and environmentalists struggling to balance the need for cost-effective insecticides to protect human populations against the need to protect fragile ecosystems and their denizens.
A more recent controversy surrounds the labeling requirements for insecticides sold in the US The EPA forces manufacturers to list active ingredients on their labels, but critics maintain that inert ingredients (which may be up to 99 percent of the product) should be listed as well. These inert ingredients often work to make the active ingredients more effective, but can cause cancer, nervous system disorders, liver and kidney damage, birth defects, and other problems to users and in the environment.
- biochemical pesticide: A naturally occurring substance that controls pests by nontoxic mechanisms.
- biopesticide:: A pesticide derived from natural materials. There are three major classes of biopesticides: microbial, plant-incorporated protectants (PIPs), and biochemical.
- carbamate pesticide: A substance that is used to control pests by disrupting neurotransmitter activity.
- contact insecticide: A substance that is toxic to insects when they come into contact with it.
- fumigant: Produces a gas that is intended to destroy pests in soil or buildings.
- microbial pesticide: Microorganisms that are used to control insects or other pests.
- miticide: A substance used to kill mites.
- nematicide: A substance used to kill nematodes (microscopic organisms that feed on plant roots).
- organochlorine insecticide: A chlorine-based substance used to indirectly kill an insect. DDT is an example of an organochlorine insecticide.
- organophosphate: A substance that is used to control pests by disrupting neurotransmitter activity. Does not typically persist in the environment. Some are very poisonous to humans (they were used as nerve agents in World War II).
- plant-incorporated-protectant: A substance produced by a plant from genetic material that has been added to the plant.
- pyrethroid pesticide: A synthetic version of the naturally occurring pesticide pyrethrin found in chrysanthemums. Some synthetic pyrethroids are toxic to the nervous system.
- systemic insecticide: A substance that is incorporated by the treated plant, and the insect ingests the insecticide while feeding on the plant.
- Beyond Pesticides
- Extremely Green Gardening Company (organic gardening supplies)
- Gardener's Supply Company (organic gardening supplies)
- The US Environmental Protection Agency - National Pesticide Information Center (NPIC)
- Radcliffe's Integrated Pest Management (IPM) World Textbook
- Sustainable Growth (organic gardening supplies)
- US Environmental Protection Agency - 2000-2001 Pesticide Market Estimates: Sales
- US Environmental Protection Agency - 2000-2001 Pesticide Market Estimates: Usage
- US Environmental Protection Agency - 2000-2001 Pesticide Market Estimates: Producers and Users
- Chemical Pesticides - Health Effects Research
- Canadian Peregrine Foundation - Have peregrine falcons and bald eagles recovered in Ontario to the point that the Province of Ontario should be down listing them?
- Natural Resources Defense Council - Fields of Change: Insect Resistance and Secondary Pest Outbreaks
- University of California, Berkley - Can Organic Farming "Feed the World?"
- Department of Health and Human Services - Agency for Toxic Substances & Disease Registry: ToxFAQs for Pyrethrins and Pyrethroids
- US Environmental Protection Agency - Pesticides: Reregistration - Permethrin Facts
- National Institute of Neurological Disorders and Stoke - Parkinson's Disease Research Web: Summary of the article on pesticides
- World Health Organization - World Health Report 2004
- US Department of Health and Human Services - Agency for Toxic Substances & Disease Registry
- NobelPrize.org - The Nobel Prize in Physiology or Medicine 1948
- Cox, Caroline & Michael Surgan, "Unidentified Inert Ingredients in Pesticides: Implications for Human and Environmental Health" Environmental Health Perspectives 114, No. 12 (2006): 1803-1806