Pesticide

The word pesticide derives from the Latin pestis (plague) and caedere (kill). The Food and Agriculture Organization (FAO) has defined pesticide as: : any substance or mixture of substances intended for preventing, destroying, or controlling any pest, including vectors of human or animal disease, unwanted species of plants or animals, causing harm during or otherwise interfering with the production, processing, storage, transport, or marketing of food, agricultural commodities, wood and wood products or animal feedstuffs, or substances that may be administered to animals for the control of insects, arachnids, or other pests in or on their bodies. The term includes substances intended for use as a plant growth regulator, defoliant, desiccant, or agent for thinning fruit or preventing the premature fall of fruit. Also used as substances applied to crops either before or after harvest to protect the commodity from deterioration during storage and transport. Biopesticides according to the EPA include microbial pesticides, biochemical pesticides, and plant-incorporated protectants. Pesticides can be classified into structural classes, with many structural classes developed for each of the target organisms listed in the table. A structural class is usually associated with a single mode of action, whereas a mode of action may encompass more than one structural class. The pesticidal chemical (active ingredient) is mixed (formulated) with other components to form the product that is sold, and which is applied in various ways. Pesticides in gas form are fumigants. Pesticides can be classified based upon their mode of action, which indicates the exact biological mechanism which the pesticide disrupts. The modes of action are important for resistance management, and are categorized and administered by the insecticide, herbicide, and fungicide resistance action committees. Pesticides may be systemic or non-systemic. A systemic pesticide moves (translocates) inside the plant. Translocation may be upward in the xylem, or downward in the phloem or both. Non-systemic pesticides (contact pesticides) remain on the surface and act through direct contact with the target organism. Pesticides are more effective if they are systemic. Systemicity is a prerequisite for the pesticide to be used as a seed-treatment. Pesticides can be classified as persistent (non-biodegradable) or non-persistent (biodegradable). A pesticide must be persistent enough to kill or control its target but must degrade fast enough not to accumulate in the environment or the food chain in order to be approved by the authorities. == History ==

From ancient times until the 1950s the pesticides used were inorganic compounds and plant extracts. The inorganic compounds were derivatives of copper, arsenic, mercury, sulfur, among others, and the plant extracts contained pyrethrum, nicotine, and rotenone among others. The less toxic of these are still in use in organic farming. In the 1940s the insecticide DDT, and the herbicide 2,4-D, were introduced. These synthetic organic compounds were widely used and were very profitable. They were followed in the 1950s and 1960s by numerous other synthetic pesticides, which led to the growth of the pesticide industry. == Development of new pesticides ==

The aim is to find new compounds or agents with improved properties such as a new mode of action or lower application rate. Another aim is to replace older pesticides which have been banned for reasons of toxicity or environmental harm or have become less effective due to development of resistance. The process starts with testing (screening) against target organisms such as insects, fungi or plants. Inputs are typically random compounds, natural products, compounds designed to disrupt a biochemical target, compounds described in patents or literature, or biocontrol organisms. Compounds that are active in the screening process, known as hits or leads, cannot be used as pesticides, except for biocontrol organisms and some potent natural products. These lead compounds need to be optimised by a series of cycles of synthesis and testing of analogs. For approval by regulatory authorities for use as pesticides, the optimized compounds must meet several requirements. In addition to being potent (low application rate), they must show low toxicity to non-target organisms, low environmental impact, and viable manufacturing cost. The cost of developing a pesticide in 2024 was estimated to be 301 million US dollars. It has become more difficult to find new pesticides. More than 100 new active ingredients were introduced in the 2000s and less than 40 in the 2010s. Newer pesticides with lower application rates tend to have more complex structures, and thus more often contain chiral centres. However, if a viable enantioselective manufacturing route cannot be found, then the racemate is registered and used. ==Uses==

In addition to their main use in agriculture, pesticides have a number of other applications. Pesticides are used to control organisms that are considered to be harmful, or pernicious to their surroundings. For example, they are used to kill mosquitoes that can transmit potentially deadly diseases like West Nile virus, yellow fever, and malaria. They can also kill bees, wasps or ants that can cause allergic reactions. Insecticides can protect animals from illnesses that can be caused by parasites such as fleas. Uncontrolled pests such as termites and mold can damage structures such as houses. Integrated pest management, the use of multiple approaches to control pests, is becoming widespread and has been used with success in countries such as Indonesia, China, Bangladesh, the U.S., Australia, and Mexico. Each use of a pesticide carries some associated risk. Proper pesticide use decreases these associated risks to a level deemed acceptable by pesticide regulatory agencies such as the United States Environmental Protection Agency (EPA) and the Pest Management Regulatory Agency (PMRA) of Canada. DDT, sprayed on the walls of houses, is an organochlorine that has been used to fight malaria vectors (mosquitos) since the 1940s. The World Health Organization recommend this approach. It and other organochlorine pesticides have been banned in most countries worldwide because of their persistence in the environment and human toxicity. DDT has become less effective, as resistance was identified in Africa as early as 1955, and by 1972 nineteen species of mosquito worldwide were resistant to DDT. ==Amount used==

Total pesticides use in agriculture in 2023 was 3.73 million tonnes of active ingredients (Mt), a 2% decrease compared with 2022, a 14 percent increase in a decade, and a doubling since 1990. Pesticides use per area of cropland in 2023 was 2.40 kg per hectare (kg/ha), a decrease of 2 percent compared with 2022; use per value of agricultural production was 0.88 g per international dollar (g/I$) (−4%); and use per person was 0.45 kg per capita (kg/cap) (−3%). ==Benefits==

Pesticides increase agricultural yields. Median yield increases range between 12% and 27% when pesticides are used, depending on the crop. Another study found that not using pesticides reduced crop yields by about 10%. A study conducted in 1999, found that a ban on pesticides in the United States may result in a rise of food prices, loss of jobs, and an increase in world hunger. There are two levels of benefits for pesticide use, primary and secondary. Primary benefits are direct gains from the use of pesticides and secondary benefits are effects that are more long-term. • Animal lives saved and disease reduced Controlling organisms that harm other human activities and structures • Drivers view unobstructed • Tree/brush/leaf hazards prevented • Wooden structures protected In one study, it was estimated that for every dollar ($1) that is spent on pesticides for crops results in up to four dollars ($4) in crops which would otherwise be lost to insects, fungi and weeds. In general, farmers benefit from having an increase in crop yield and from being able to grow a variety of crops throughout the year. Consumers of agricultural products also benefit from being able to afford the vast quantities of produce available year-round. ==Disadvantages==

On the cost side of pesticide use there can be costs to the environment and costs to human health. Pesticides safety education and pesticide applicator regulation are designed to protect the public from pesticide misuse, but do not eliminate all misuse. Reducing the use of pesticides and choosing less toxic pesticides may reduce risks placed on society and the environment from pesticide use. mimicking hormones causing reproductive problems, and also causing cancer. A 2007 systematic review found that "most studies on non-Hodgkin lymphoma and leukemia showed positive associations with pesticide exposure" and thus concluded that cosmetic use of pesticides should be decreased. There is substantial evidence of associations between organophosphate insecticide exposures and neurobehavioral alterations. Limited evidence also exists for other negative outcomes from pesticide exposure including neurological, birth defects, and fetal death. 2014 epidemiological review found associations between autism and exposure to certain pesticides, but noted that the available evidence was insufficient to conclude that the relationship was causal. Owing to inadequate regulation and safety precautions, 99% of pesticide-related deaths occur in developing countries that account for only 25% of pesticide usage. Exposure to pesticide residues from eating food According to the American Cancer Society there is no evidence that pesticide residues in food increase the risk of people getting cancer. A 2009 study estimated that lifetime exposure to pesticide residues from eating fruits and vegetables results in only 4.2 and 3.2 minutes of lost life per person in Switzerland and the United States, respectively. Non-occupational pesticide use Pesticides are also found in majority of U.S. households with 88 million out of the 121.1 million households indicating that they use some form of pesticide in 2012. As of 2007, there were more than 1,055 active ingredients registered as pesticides, which yield over 20,000 pesticide products that are marketed in the United States. The American Academy of Pediatrics recommends limiting exposure of children to pesticides and using safer alternatives: One study found pesticide self-poisoning the method of choice in one third of suicides worldwide, and recommended, among other things, more restrictions on the types of pesticides that are most harmful to humans. Pesticide use among agricultural workers The World Health Organization and the UN Environment Programme estimate that 3 million agricultural workers in the developing world experience severe poisoning from pesticides each year, resulting in 18,000 deaths. Other occupational exposures besides agricultural workers, including pet groomers, groundskeepers, and fumigators, may also put individuals at risk of health effects from pesticides. At-home pesticide use, use of unregulated products, and the role of undocumented workers within the agricultural industry makes characterizing true pesticide exposure a challenge. It is estimated that 50–80% of pesticide poisoning cases are unreported. Underreporting of pesticide poisoning is especially common in areas where agricultural workers are less likely to seek care from a healthcare facility that may be monitoring or tracking the incidence of acute poisoning. The extent of unintentional pesticide poisoning may be much greater than available data suggest, particularly among developing countries. Globally, agriculture and food production remain one of the largest industries. In East Africa, the agricultural industry represents one of the largest sectors of the economy, with nearly 80% of its population relying on agriculture for income. Farmers in these communities rely on pesticide products to maintain high crop yields. Some East Africa governments are shifting to corporate farming, and opportunities for foreign conglomerates to operate commercial farms have led to more accessible research on pesticide use and exposure among workers. In other areas where large proportions of the population rely on subsistence, small-scale farming, estimating pesticide use and exposure is more difficult. Pesticide poisoning into choline and acetate by acetylcholinesterase Pesticides may exhibit toxic effects on humans and other non-target species, the severity of which depends on the frequency and magnitude of exposure. Toxicity also depends on the rate of absorption, distribution within the body, metabolism, and elimination of compounds from the body. Commonly used pesticides like organophosphates and carbamates act by inhibiting acetylcholinesterase activity, which prevents the breakdown of acetylcholine at the neural synapse. Excess acetylcholine can lead to symptoms like muscle cramps or tremors, confusion, dizziness and nausea. Studies show that farm workers in Ethiopia, Kenya, and Zimbabwe have decreased concentrations of plasma acetylcholinesterase, the enzyme responsible for breaking down acetylcholine acting on synapses throughout the nervous system. Other studies in Ethiopia have observed reduced respiratory function among farm workers who spray crops with pesticides. Numerous exposure pathways for farm workers increase the risk of pesticide poisoning, including dermal absorption walking through fields and applying products, as well as inhalation exposure. Measuring exposure to pesticides There are multiple approaches to measuring a person's exposure to pesticides, each of which provides an estimate of an individual's internal dose. Two broad approaches include measuring biomarkers and markers of biological effect. The former involves taking direct measurement of the parent compound or its metabolites in various types of media: urine, blood, serum. Biomarkers may include a direct measurement of the compound in the body before it's been biotransformed during metabolism. Other suitable biomarkers may include the metabolites of the parent compound after they've been biotransformed during metabolism. Better understanding of how pesticides elicit their toxic effects is needed before this method of exposure assessment can be applied to occupational exposure of agricultural workers. Alternative methods to assess exposure include questionnaires to discern from participants whether they are experiencing symptoms associated with pesticide poisoning. Self-reported symptoms may include headaches, dizziness, nausea, joint pain, or respiratory symptoms. Because of critical development periods of the fetus and newborn children, these non-working populations are more vulnerable to the effects of pesticides, and may be at increased risk of developing neurocognitive effects and impaired development. Furthermore, pesticide use can adversely impact neighboring agricultural activity, as pests themselves drift to and harm nearby crops that have no pesticide used on them. In addition, pesticide use reduces invertebrate biodiversity in streams, contributes to pollinator decline, destroys habitat (especially for birds), and threatens endangered species. in particular DDT and other organochlorine pesticides, which were stable and lipophilic, and thus able to bioaccumulate in the body and the food chain. and which spread throughout the planet. Persistent pesticides are no longer used for agriculture, and will not be approved by the authorities.) residues can still be detected in humans at levels 5 to 10 times lower than found in the 1970s. Pesticides now have to be degradable in the environment. Such degradation of pesticides is due to both innate chemical properties of the compounds and environmental processes or conditions. For example, the presence of halogens within a chemical structure often slows down degradation in an aerobic environment. Adsorption to soil may retard pesticide movement, but also may reduce bioavailability to microbial degraders. Pesticide contamination in the environment can be monitored through bioindicators such as bee pollinators. Additional costs include the registration process and the cost of purchasing pesticides: which are typically borne by agrichemical companies and farmers respectively. The registration process can take several years to complete (there are 70 types of field tests) and can cost $50–70 million for a single pesticide. At the beginning of the 21st century, the United States spent approximately $10 billion on pesticides annually. ==Resistance==

The use of pesticides inherently entails the risk of resistance developing. Various techniques and procedures of pesticide application can slow the development of resistance, as can some natural features of the target population and surrounding environment. ==Alternatives==

Alternatives to pesticides are available and include methods of cultivation, use of biological pest controls (such as pheromones and microbial pesticides), genetic engineering (mostly of crops), and methods of interfering with insect breeding. These methods are becoming increasingly popular and often are safer than traditional chemical pesticides. Cultivation practices Cultivation practices include polyculture (growing multiple types of plants), crop rotation, planting crops in areas where the pests that damage them do not live, timing planting according to when pests will be least problematic, and use of trap crops that attract pests away from the real crop. In other systems, trap crops can fail to reduce pest densities at a commercial scale, even when the trap crop works in controlled experiments. Use of other organisms Release of other organisms that fight the pest is another example of an alternative to pesticide use. These organisms can include natural predators or parasites of the pests. and the gypsy moth. This is a costly and slow approach that only works on some types of insects. Push pull strategy Push-pull technique: intercropping with a "push" crop that repels the pest, and planting a "pull" crop on the boundary that attracts and traps it. Effectiveness Some evidence shows that alternatives to pesticides can be equally effective as the use of chemicals. A study of Maize fields in northern Florida found that the application of composted yard waste with high carbon to nitrogen ratio to agricultural fields was highly effective at reducing the population of plant-parasitic nematodes and increasing crop yield, with yield increases ranging from 10% to 212%; the observed effects were long-term, often not appearing until the third season of the study. Pesticide resistance is increasing and that may make alternatives more attractive. ==Types==

Biopesticides Biopesticides are certain types of pesticides derived from such natural materials as animals, plants, bacteria, and certain minerals. For example, canola oil and baking soda have pesticidal applications and are considered biopesticides. Biopesticides fall into three major classes: • Microbial pesticides which consist of bacteria, entomopathogenic fungi or viruses (and sometimes includes the metabolites that bacteria or fungi produce). Entomopathogenic nematodes are also often classed as microbial pesticides, even though they are multi-cellular. • Biochemical pesticides or herbal pesticides are naturally occurring substances that control (or monitor in the case of pheromones) pests and microbial diseases. • Plant-incorporated protectants (PIPs) have genetic material from other species incorporated into their genetic material (i.e. GM crops). Their use is controversial, especially in many European countries. By pest type Pesticides that are related to the type of pests are: ==Regulation==

International In many countries, pesticides must be approved for sale and use by a government agency. Worldwide, 85% of countries have pesticide legislation for the proper storage of pesticides and 51% include provisions to ensure proper disposal of all obsolete pesticides. Though pesticide regulations differ from country to country, pesticides, and products on which they were used are traded across international borders. To deal with inconsistencies in regulations among countries, delegates to a conference of the United Nations Food and Agriculture Organization adopted an International Code of Conduct on the Distribution and Use of Pesticides in 1985 to create voluntary standards of pesticide regulation for many countries. The FAO claims that the code has raised awareness about pesticide hazards and decreased the number of countries without restrictions on pesticide use. Three other efforts to improve regulation of international pesticide trade are the United Nations London Guidelines for the Exchange of Information on Chemicals in International Trade and the United Nations Codex Alimentarius Commission. The former seeks to implement procedures for ensuring that prior informed consent exists between countries buying and selling pesticides, while the latter seeks to create uniform standards for maximum levels of pesticide residues among participating countries. United States of hazardous herbicide in the US In the United States, the Environmental Protection Agency (EPA) is responsible for regulating pesticides under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) and the Food Quality Protection Act (FQPA). Studies must be conducted to establish the conditions in which the material is safe to use and the effectiveness against the intended pest(s). The EPA regulates pesticides to ensure that these products do not pose adverse effects to humans or the environment, with an emphasis on the health and safety of children. Pesticides produced before November 1984 continue to be reassessed in order to meet the current scientific and regulatory standards. All registered pesticides are reviewed every 15 years to ensure they meet the proper standards. These records must be made available to employees and state or territorial environmental regulatory agencies. In addition to the EPA, the United States Department of Agriculture (USDA) and the United States Food and Drug Administration (FDA) set standards for the level of pesticide residue that is allowed on or in crops. The EPA looks at what the potential human health and environmental effects might be associated with the use of the pesticide. In addition, the U.S. EPA uses the National Research Council's four-step process for human health risk assessment: (1) Hazard Identification, (2) Dose-Response Assessment, (3) Exposure Assessment, and (4) Risk Characterization. In 2013 Kaua'i County (Hawaiʻi) passed Bill No. 2491 to add an article to Chapter 22 of the county's code relating to pesticides and GMOs. The bill strengthens protections of local communities in Kaua'i where many large pesticide companies test their products. The first legislation providing federal authority for regulating pesticides was enacted in 1910. Their benefits include lower impact on human health and other living organisms, reduced groundwater contamination, and lower dose rates. Canada EU EU legislation has been approved banning the use of highly toxic pesticides including those that are carcinogenic, mutagenic or toxic to reproduction, those that are endocrine-disrupting, and those that are persistent, bioaccumulative and toxic (PBT) or very persistent and very bioaccumulative (vPvB) and measures have been approved to improve the general safety of pesticides across all EU member states. In 2023 The Environment Committee of European Parliament approved a decision aiming to reduce pesticide use by 50% (the most hazardous by 65%) by the year 2030 and ensure sustainable use of pesticides (for example use them only as a last resort). The decision also includes measures for providing farmers with alternatives. ==Residue==

Pesticide residue refers to the pesticides that may remain on or in food after they are applied to food crops. The maximum residue limits (MRL) of pesticides in food are carefully set by the regulatory authorities to ensure, to their best judgement, no health impacts. Regulations such as pre-harvest intervals also often prevent harvest of crop or livestock products if recently treated in order to allow residue concentrations to decrease over time to safe levels before harvest. Exposure of the general population to these residues most commonly occurs through consumption of treated food sources, or being in close contact to areas treated with pesticides such as farms or lawns. Persistent pesticides are no longer used for agriculture, and will not be approved by the authorities. Because the half life in soil is long (for DDT 2–15 years == See also ==