The environmental effects of pesticides describe the broad series of consequences of using pesticides. The unintended consequences of pesticides is one of the main drivers of the negative impact of modern industrial agriculture on the environment. Pesticides, because they are toxic chemicals meant to kill pest species, can affect non-target species, such as plants, animals and humans. Over 98% of sprayed insecticides and 95% of herbicides reach a destination other than their target species, because they are sprayed or spread across entire agricultural fields. Other agrochemicals, such as fertilizers, can also have negative effects on the environment.

The negative effects of pesticides are not just in the area of application. Runoff and pesticide drift can carry pesticides into distant aquatic environments or other fields, grazing areas, human settlements and undeveloped areas. Other problems emerge from poor production, transport, storage and disposal practices.Tashkent (1998), Part 75. Conditions and provisions for developing a national strategy for biodiversity conservation . Biodiversity Conservation National Strategy and Action Plan of Republic of Uzbekistan. Prepared by the National Biodiversity Strategy Project Steering Committee with the Financial Assistance of The Global Environmental Facility (GEF) and Technical Assistance of United Nations Development Programme (UNDP). Retrieved on 17 September 2007. Over time, repeat application of pesticides increases pest resistance, while its effects on other species can facilitate the pest's resurgence. Alternatives to heavy use of pesticides, such as integrated pest management, and sustainable agriculture techniques such as polyculture mitigate these consequences, without the harmful toxic chemical application.

Environmental modelling indicates that globally over 60% of global agricultural land (~24.5 million km²) is "at risk of pesticide pollution by more than one active ingredient", and that over 30% is at "high risk" of which a third are in high-biodiversity regions. Each pesticide or pesticide class comes with a specific set of environmental concerns. Such undesirable effects have led many pesticides to be banned, while regulations have limited and/or reduced the use of others. The global spread of pesticide use, including the use of older/obsolete pesticides that have been banned in some jurisdictions, has increased overall.

History

The first synthetic herbicides were discovered in the 1930's and 1940's. This was the era when synthetic antibiotics, plastics, and many other materials became available. Synthetic pesticides became popular rapidly after World War II. Crop yields increased significantly through the discovery of 2,4-D. Many insect infestations were addressed by DDT, greatly lowering rates of typhus and malaria worldwide. In 1962, an estimated 85,000,000 kilograms of DDT was produced in the US alone.

Public concern over the undesirable environmental effects of chemicals arose in the early 1960s with the publication of Rachel Carson′s book, Silent Spring. Shortly thereafter, DDT, originally used to combat malaria, and its metabolites were shown to cause population-level effects in raptorial birds. Initial studies in industrialized countries focused on acute mortality effects mostly involving birds or fish.

Modern pesticide usage Today, over 3.5 billion kilograms of synthetic pesticides are used for the world's agriculture in an over $45 billion industry. Current lead agrichemical producers include Syngenta (ChemChina), Bayer Crop Science, BASF, Dow AgroSciences, FMC, ADAMA, Nufarm, Corteva, Sumitomo Chemical, UPL, and Huapont Life Sciences. Bayer CropScience and its acquisition of Monsanto led it to record profits in 2019 of over $10 billion in sales, which herbicide shares growing by 22%, followed closely by Syngenta.

In 2016, the United States consumed of pesticides banned in the EU, of pesticides banned in Brazil and of pesticides banned in China, with most of banned pesticides banned staying constant or increasing in the United States over the past 25 years according to studies.

In the United States, conventional pesticide use peaked in 1979, and by 2007, had been reduced by 25 percent from the 1979 peak level,EPA. 2011. Pesticides industry sales and usage; 2006 and 2007 market estimates. while US agricultural output increased by 43 percent over the same period.

Specific pesticide effects + Pesticide environmental effects Pesticide/class Effect(s) Organochlorine DDT/DDE Endocrine disruptor Thyroid disruption properties in rodents, birds, amphibians and fish Acute mortality attributed to inhibition of acetylcholinesterase activity DDT Egg shell thinning in raptorial birds Carcinogen Endocrine disruptor DDT/Diclofol, Dieldrin and Toxaphene Juvenile population decline and adult mortality in wildlife reptiles DDT/Toxaphene/Parathion Susceptibility to fungal infection Triazine Earthworms became infected with monocystid gregarines Chlordane Interact with vertebrate immune systems Carbamates, the phenoxy herbicide 2,4-D, and atrazine Anticholinesterase Bird poisoning Animal infections, disease outbreaks and higher mortality. Organophosphate Thyroid disruption properties in rodents, birds, amphibians and fish Acute mortality attributed to inhibition of acetylcholine esterase activity Immunotoxicity, primarily caused by the inhibition of serine hydrolases or esterases Oxidative damage Modulation of signal transduction pathways Impaired metabolic functions such as thermoregulation, water and/or food intake and behavior, impaired development, reduced reproduction and hatching success in vertebrates. Carbamate Thyroid disruption properties in rodents, birds, amphibians and fish Impaired metabolic functions such as thermoregulation, water and/or food intake and behavior, impaired development, reduced reproduction and hatching success in vertebrates. Interact with vertebrate immune systems Acute mortality attributed to inhibition of acetylcholine esterase activity Phenoxy herbicide 2,4-D Interact with vertebrate immune systems Atrazine Reduced northern leopard frog (Rana pipiens) populations because atrazine killed phytoplankton, thus allowing light to penetrate the water column and periphyton to assimilate nutrients released from the plankton. Periphyton growth provided more food to grazers, increasing snail populations, which provide intermediate hosts for trematode. Pyrethroid Thyroid disruption properties in rodents, birds, amphibians and fish Thiocarbamate Triazine Triazole Impaired metabolic functions such as thermoregulation, water and/or food intake and behavior, impaired development, reduced reproduction and hatching success in vertebrates. Neonicotinoic/Nicotinoid respiratory, cardiovascular, neurological, and immunological toxicity in rats and humans Disrupt biogenic amine signaling and cause subsequent olfactory dysfunction, as well as affecting foraging behavior, learning and memory. Imidacloprid, Imidacloprid/pyrethroid λ-cyhalothrin Impaired foraging, brood development, and colony success in terms of growth rate and new queen production. Thiamethoxam High honey bee worker mortality due to homing failure (risks for colony collapse remain controversial).FlupyradifuroneLethal and sublethal adverse synergistic effects in bees. Its toxicity depends on season and nutritional stress, and can reduce bee survival, food consumption, thermoregulation, flight success, and increase flight velocity. It has the same mode of action of neonicotinoids. Spinosyns Affect various physiological and behavioral traits of beneficial arthropods, particularly hymenopterans. Bt corn/Cry Reduced abundance of some insect taxa, predominantly susceptible Lepidopteran herbivores as well as their predators and parasitoids. Herbicide Reduced food availability and adverse secondary effects on soil invertebrates and butterflies Decreased species abundance and diversity in small mammals. Benomyl Altered the patch-level floral display and later a two-thirds reduction of the total number of bee visits and in a shift in the visitors from large-bodied bees to small-bodied bees and flies. Herbicide and planting cycles Reduced survival and reproductive rates in seed-eating or carnivorous birds.

Persistent organic pollutants

Persistent organic pollutants (POPs) are compounds that resist degradation and thus remain in the environment beyond their intended term. Some pesticides, including aldrin, chlordane, DDT, dieldrin, endrin, heptachlor, hexachlorobenzene, mirex, and toxaphene, are considered POPs. Some POPs have the ability to volatilize and travel great distances through the atmosphere to become deposited in remote regions. Such chemicals may have the ability to bioaccumulate and biomagnify and can biomagnify (i.e. become more concentrated) up to 70,000 times their original concentrations.Ritter L, Solomon KR, and Forget J, Stemeroff M, and O'Leary C. Persistent organic pollutants: An Assessment Report on: DDT, Aldrin, Dieldrin, Endrin, Chlordane, Heptachlor, Hexachlorobenzene, Mirex, Toxaphene, Polychlorinated Biphenyls, Dioxins and Furans . Prepared for The International Programme on Chemical Safety (IPCS), within the framework of the Inter-Organization Programme for the Sound Management of Chemicals (IOMC). Retrieved on 16 September 2007. POPs can affect non-target organisms in the environment and increase risk to humansCenters for Disease Control and Prevention. Pesticides . cdc.gov. Retrieved on 15 September 2007. by disruption in the endocrine, reproductive, and respiratory systems.

The half-life of pesticides is of great interest. Some pesticides degrade rapidly in the environment, others, called persistent, linger, causing undesired effects. and certain authors maintain that pesticide risk and impact assessment models rely on and are sensitive to information describing dissipation from plants.

The half-life for pesticides is explained in two NPIC fact sheets. Known degradation pathways are through: photolysis, chemical dissociation, sorption, bioaccumulation and plant or animal metabolism.npic.orst.edu: " Pesticide Half-life Fact Sheet", 2015npic.orst.edu: "What Happens to Pesticides Released in the Environment?", 20 September 2017 A USDA fact sheet published in 1994 lists the soil adsorption coefficient and soil half-life for then-commonly used pesticides.usu.edu: "PESTICIDE ADSORPTION AND HALF-LIFE" , October 2004usu.edu: "PESTICIDE ADSORPTION AND HALF-LIFE", February 1999

Environmental effects

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