Effects of Pesticides on the Environment and Human Health

Pesticide health effects fall into five groups: nervous system, skin and eye, cancer, reproductive and endocrine effects. People are exposed through the skin, lungs, mouth and eyes. Acute poisoning ranges from mild skin irritation to coma or even death. Long-term effects include tumors, nervous system disorders, birth defects, reproductive effects and endocrine disruption. Pesticides also affect the environment by contaminating water, soil and air, driving biodiversity loss and leading to pest resistance. Approval rules limit harm to people and the environment. Following the label and wearing protective clothing and equipment reduces exposure.

What Are the Health Effects of Pesticides?

The health effects of pesticides fall into five groups: nervous system, skin and eye, cancer, reproductive and endocrine effects. Pesticides produce different effects depending on the pesticide type, as the EPA states. Key effects include:

• Nervous system effects: Organophosphates and carbamates affect the nervous system, and pyrethrins and pyrethroids affect the central nervous system. Mild poisoning brings fatigue, headache and dizziness.
• Skin and eye irritation: Dermatitis, inflammation of the skin, is generally accepted as the most commonly reported effect of pesticide exposure. The eyes and the mucous membranes of the nose feel raw and scratchy.
• Cancer: Some pesticides may be carcinogens, and some are genotoxic, meaning they damage DNA and can cause mutations or cancer.
• Reproductive effects: Long-term pesticide exposure can cause adverse effects on reproduction. Suspected effects include birth defects and toxicity to a fetus.
• Endocrine effects: Some pesticides affect the hormone or endocrine system in the body.

Pesticides cause chronic poisoning, and its symptoms may not become evident for weeks, months, or even years, unlike acute poisoning.

A 2024 study by Chander Shekhar finds that chronic exposure to pesticides presents significant health risks. Those risks are highest for individuals in high-exposure environments like agriculture. Pesticides produce symptoms that range from a mild skin irritation to coma or even death.

WHO assesses the risks of pesticides to people, in collaboration with FAO, and recommends protection measures. The Agency for Toxic Substances and Disease Registry protects communities from harmful health effects of hazardous substances.

Which Pesticide Classes Affect the Nervous System?

Organophosphates and carbamates affect the nervous system, and these pesticide classes act through one enzyme. Many organophosphate and carbamate insecticides work by inhibiting the enzyme acetylcholinesterase. Acetylcholinesterase breaks down the neurotransmitter acetylcholine. Inhibition of this enzyme stops the breakdown of acetylcholine. Pyrethrins and pyrethroids affect the central nervous system.

Organophosphate insecticides form a diverse group of phosphorus-containing organic compounds, used widely around the world in agriculture and vector control. Carbamate insecticides inhibit acetylcholinesterase strongly yet reversibly, which explains their agricultural use. Pyrethroid insecticides are synthetic derivatives of natural pyrethrins extracted from Chrysanthemum cinerariaefolium.

Organophosphate insecticides account for 38% of the globally used pesticides because of their high efficacy. Exposure to organophosphate insecticides of high, moderate, slight and low toxicity can all harm the nervous system. Children and heavily exposed workers are the people most affected. Paper-based acetylcholinesterase inhibition assays detect organophosphate and carbamate pesticides, which shows how exposure is measured.

Michael Eddleston of the University of Oxford studied the management of acute organophosphorus pesticide poisoning.

Do Pesticides Cause Cancer?

It depends. Some pesticides are carcinogens, and no source supports one answer for all pesticides. Some pesticides are genotoxic, meaning they damage DNA, which can cause mutations or cancer.

The International Agency for Research on Cancer identifies carcinogenic hazards through its Monographs programme. In March 2015 it classified glyphosate as probably carcinogenic to humans (Group 2A). A working group of 17 experts from 11 countries evaluated five organophosphate insecticides and herbicides, including glyphosate. It found strong evidence of genotoxicity for pure glyphosate and glyphosate formulations.

A 2019 study by Luoping Zhang pooled human epidemiological studies of glyphosate-based herbicides. The current meta-analysis suggests a compelling link between exposures to glyphosate-based herbicides and increased risk for non-Hodgkin lymphoma.

Non-Hodgkin lymphoma was examined in a larger systematic review of pesticide chemical groups. The review extracted associations with 21 pesticide chemical groups and 80 active ingredients from 44 papers. Phenoxy herbicides, carbamate insecticides, organophosphorus insecticides and lindane were positively associated with non-Hodgkin lymphoma.

Chemical pesticides link to chronic diseases that range from various types of cancers to neurological disorders. These diseases include developmental delays in children and effects on reproductive capacity and infertility.

How Do People Get Exposed to Pesticides?

People get exposed to pesticides through four routes: dermal (skin), inhalation (lungs), oral (mouth), and the eyes. Pesticides may be ingested if stored improperly in food or beverage containers.

At least two pesticides were present in the bodies of 84% of survey participants in a human biomonitoring study. The study ran from 2014 to 2021 in five European countries. Pesticides are used in non-agricultural settings such as forestry, roads, railways and urban areas. Urban areas include public parks, playgrounds and gardens.

The National Health and Nutrition Examination Survey assesses the health and nutritional status of adults and children. Its findings are used to determine the prevalence of major diseases and risk factors for diseases.

Paraquat products registered in the United States are Restricted Use Pesticides. Only trained certified applicators may use them.

Chander Shekhar reviewed pesticide exposure and its risks in Toxicology reports.

What Are the Symptoms of Acute Pesticide Poisoning?

The symptoms of acute pesticide poisoning range from mild skin irritation to coma or even death. Pesticide poisoning shows in three groups of symptoms. Key symptoms include:

• Mild systemic signs: Mild poisoning brings fatigue, headache, dizziness and blurred vision. It brings excessive sweating and salivation, nausea and vomiting, and stomach cramps or diarrhea. Chlorpyrifos is an organophosphate insecticide, acaricide and miticide used primarily to control foliage and soil-borne insect pests.
• Skin, eye and airway irritation: The eyes, the mucous membranes of the nose, and the linings of the mouth and back of the throat feel raw and scratchy.
• Severe poisoning with paralysis, coma or death: Exposure to organophosphate insecticides of every toxicity can cause nausea, vomiting, muscle tremors and convulsions. Organophosphate insecticides induce neuropathy through nicotinic or muscarinic receptors, or by phosphorylating acetylcholinesterase.

A 2008 study by Michael Eddleston in the Lancet reviews acute organophosphorus pesticide poisoning. Some organophosphorus pesticides might prove very difficult to treat with current therapies.

Paraquat toxicity is the subject of an EPA safety message for pesticide application educators. The message highlights the negative repercussions of misusing paraquat.

What Are the Long-Term Health Effects of Pesticides?

The long-term health effects of pesticides include tumors, nervous system disorders, birth defects, reproductive effects and endocrine disruption. Chronic pesticide poisoning may not become evident for weeks, months, or even years. Key effects include:

• Cancer and tumors: Certain pesticides are suspected to produce benign or malignant tumors and genetic changes.
• Nervous system disorders: Alzheimer’s disease and Parkinson’s disease are the most common disorders connected to pesticide neurotoxicity. Suggested biologic mechanisms exist for specific pesticides that may increase Parkinson’s disease risk.
• Birth defects and reproductive effects: Certain pesticides are suspected to cause birth defects, toxicity to a fetus and reproduction effects. Blood disorders and nerve disorders are suspected as well.
• Endocrine disruption: Certain pesticides are suspected to cause endocrine disruption. Maternal exposure to dichlorodiphenyltrichloroethane (DDT) is associated with risk of obesity in middle age.

A 2024 study titled A systematic review of pesticide exposure, associated risks, and long-term human health impacts covers these effects. Evidence indicates strong associations with several long-term health conditions. Additional research is necessary to elucidate dose-response relationships and mechanisms of action.

Are Children More Vulnerable to Pesticides?

Yes. Children are more vulnerable to pesticides because their organs, nervous systems and immune systems are still developing. Pesticide levels were consistently higher in children than in adults.

Children are at the highest risk of accidental ingestion. The CHAMACOS study is a longitudinal cohort study of mother-child pairs living in a California farmworker community.

A 2018 study by Cécile Chevrier reviewed cohort evidence on children. There were no adverse neurodevelopmental outcomes at 6 years of age following prenatal exposure to pesticides. Cohort evidence on neurodevelopment is therefore mixed.

Atrazine, a common water contaminant in the U.S., has been associated with adverse birth outcomes in previous studies.

Do Pesticides Disrupt Hormones?

Yes. Some pesticides disrupt hormones by affecting the hormone or endocrine system in the body. Endocrine disruptors are substances that interfere with hormones and hormone balance. The endocrine effects can be activated by very low concentrations of chemicals.

The Endocrine Disruptor Screening Program uses a two-tiered approach to screen pesticides, chemicals and environmental contaminants. It tests their potential effect on estrogen, androgen and thyroid hormone systems.

A 2020 study by Linda G Kahn of New York University reviews endocrine-disrupting chemicals. Evidence has accumulated for cognitive deficits and attention-deficit disorder in children after prenatal exposure to organophosphate pesticides. The same evidence covers bisphenol A and polybrominated flame retardants. Systematic evaluation is needed of the probability and strength of these exposure-outcome relations. The growing evidence supports urgent action to reduce exposure to endocrine-disrupting chemicals.

Dichlorodiphenyltrichloroethane and its persistent metabolite p,p′-DDE have an extensively investigated effect on obesity. Carbamate insecticides carbaryl and carbofuran bind directly to melatonin receptors, a new mechanism that could impact human health.

Who Is Most at Risk From Pesticide Exposure?

The people most at risk from pesticide exposure are of three kinds. The first are agricultural workers who apply pesticides. The second are workers in chemical manufacture and applicators with long-term exposure. The third are people in low-income communities.

Agricultural workers belong to the population most at risk, which WHO defines as those directly exposed to pesticides. A 2021 study by Jean V Varghese reports an increased risk of cancer among the pesticide applicators. Positive exposure-response relationships were observed for 31 pesticides in that review.

Chemical manufacturing workers and applicators exposed to high pesticide levels for many years run the greatest chronic risk. The Agricultural Health Study follows licensed pesticide applicators and their spouses from Iowa and North Carolina. It began in 1993 to learn how agricultural, lifestyle and genetic factors affect the health of farming populations.

Carbamate insecticides are associated with psychological distress and depression in agricultural workers after occupational exposure. Non-Hodgkin lymphoma is linked to occupational exposure to agricultural pesticide chemical groups and active ingredients.

Low-income communities face exposure because many pesticides are heavily used in urban and low-income communities.

How Do Pesticides Affect the Environment?

Pesticides affect the environment by contaminating water, soil and air, driving biodiversity loss and leading to pest resistance. Pesticide use poses significant hazards to the environment and public health.

A 2024 study by Rajwinder Kaur in The Science of the total environment reviews the consequences of pesticides. The review focuses on the consequences for targeted and non-targeted organisms, including the health and well-being of humans.

From 2011 to 2020, pesticide sales in the EU-27 remained relatively stable at around 350,000 tonnes per year.

The Stockholm Convention on Persistent Organic Pollutants is an international environmental treaty signed in Stockholm on 22 May 2001. It took effect on 17 May 2004 and aims to eliminate or restrict persistent organic pollutants.

Dichlorodiphenyltrichloroethane is banned in most but not all countries, yet its metabolite p,p′-DDE persists in serum and adipose tissue samples.

Neonicotinoid insecticides leave residues below acute and chronic toxicity levels, yet reliable data are lacking. Most analyses ran near the detection limit and covered only few crops.

Shifting towards agroecology, intercropping and crop diversification could reduce dependency on pesticides while maintaining crop yields.

Do Pesticides Contaminate Water and Soil?

Yes. Older pesticides contaminate water and soil, and some remain there for years. Some of the older, less costly pesticides can remain for years in soil and water.

In 2020, one or more pesticides were detected above thresholds of concern at 22% of monitoring sites. These sites are in rivers and lakes across Europe.

Residues were found in 83% of agricultural soils tested in a 2019 study.

Rajwinder Kaur of Chitkara College of Pharmacy calls pesticides an alarming detriment to health and environment.

Atrazine monitoring ran under the EPA Atrazine Monitoring Program between 2006 and 2008. The Safe Drinking Water Act is the primary US federal law intended to ensure safe drinking water. It requires the EPA to establish National Primary Drinking Water Regulations for contaminants that may cause adverse public health effects.

Do Pesticides Harm Pollinators and Biodiversity?

Yes. Pesticides harm pollinators and biodiversity, together with other stressors. Pesticides act as one of these stressors, with parasites and lack of flowers.

A 2015 study by Dave Goulson shows that chronic exposure to multiple interacting stressors is driving honey bee colony losses. The same stressors drive declines of wild pollinators.

Falling insect populations indirectly affect insect-eating birds and farmland birds. Extensive pesticide use is one of the primary factors behind their decline in Europe.

Pesticide use threatens key ecosystem services by affecting pollinators, soil microorganisms and pest control agents.

Neonicotinoid insecticides control pests in many crops but can affect non-target organisms such as pollinators. Laboratory studies describe lethal and sublethal effects on the foraging behavior, learning and memory of bees. Field studies at field-realistic dosages observed no effects, so uncertainty remains.

How Are Pesticides Regulated to Limit Harm?

Pesticides are regulated through approval rules that limit harm to people and the environment. Pesticide toxicity categories are determined by the effects caused if the pesticide is consumed. The same effects are weighed when the pesticide is inhaled or placed in contact with the skin.

Two statutes give EPA broad authority over pesticides: FIFRA and the Food Quality Protection Act. The Food Quality Protection Act of 1996 amended FIFRA and fundamentally changed EPA’s regulation of pesticides. Before registration, the applicant must show that use will not generally cause unreasonable adverse effects on the environment.

Active substances are approved if they are safe for people’s health and cause no unacceptable environmental effects. Regulation (EC) No 1107/2009 governs the placing of plant protection products on the market. Directive 2009/128/EC aims to achieve a sustainable use of pesticides in the EU. It does so by reducing the risks and impacts of pesticide use on human health and the environment.

The EU targets a 50% reduction in the use and risk of chemical pesticides by 2030. This target belongs to the Farm to Fork strategy.

The European Food Safety Authority publishes guidance for assessing the risks of pesticides to birds and mammals. The Codex Alimentarius sets maximum residue limits for pesticides in food.

A 2000 study titled Effectiveness of interventions in reducing pesticide overexposure and poisonings examines interventions against overexposure.

How Can Exposure to Pesticides Be Reduced?

To limit exposure to pesticides, follow the label instructions and wear personal protective clothing and equipment. Train supervisors, applicators and co-workers to recognize the symptoms of pesticide poisoning. Store and dispose of pesticides correctly. Exposure to pesticides can be reduced by all four steps.

Applicators can minimize or nearly eliminate exposure and thus reduce hazard. They do so by following the label instructions, using personal protective clothing and equipment, and handling the pesticide properly.

A 2000 study by M C Keifer showed that PPE was effective in reducing exposure.

Supervisors, applicators and co-workers should receive training to help them recognize symptoms of pesticide poisoning. If pesticides were always stored and disposed of correctly, children would never have access to them.

The Worker Protection Standard covers pesticide safety for agricultural employers. Integrated Pest Management is an effective and environmentally sensitive approach that relies on a combination of common-sense practices. Integrated Pest Management programs use current, comprehensive information on the life cycles of pests and their interaction with the environment.

Correct handling of paraquat prevents spills and the pouring of the pesticide into other containers.