Are pesticides harmful to humans and the environment?

Last Updated : 05 August 2024

As the population grows and agricultural land remains limited, it is important to ensure that farms are as productive as they can be. In modern agriculture, pesticides are critical for the productivity of farming systems and for safeguarding consumers from the ill effects of pest-damaged foods. However, if used in excess or incorrectly, their residues can end up on our plates and negatively impact our health. This article will explore what pesticides are and whether they are a cause for concern.

What are pesticides?

Pesticides, frequently referred to as plant protection products, are a broad category of chemicals that are used to control, repel, or eliminate pests. Pesticides play a key role in modern agriculture, contributing to the increase in yields that has been achieved in recent decades for most major cereal, fruit and vegetable crops. The use of pesticides has also allowed growers to produce crops in otherwise unsuitable locations and to extend growing seasons while maintaining product quality.

Pesticides encompass a wide range of products including herbicides, insecticides, fungicides, and more, depending on the target organism. Herbicides, a subset of pesticides, are specifically formulated to kill or prevent the growth of unwanted plants or weeds. Insecticides, another key group within the pesticide family, are used for controlling or eradicating insects that pose threats to crops, agricultural infrastructure, or human and animal health. Pesticides typically have two main components: an active ingredient that targets and kills pests, and inert ingredients, which make up the majority of the product.¹ These inert ingredients can include solvents, substances that help the active ingredient adhere to surfaces, and chemicals that protect the active ingredient from sunlight damage.¹

Which foods contain pesticides?

Pesticides are used for growing all kinds of food. As a result, residues can end up in anything that is grown using conventional agricultural techniques. In addition to the pesticides applied during cultivation, crops can also absorb pesticides that have lingered in the soil from past applications. Residues can also end up in animal-based foods such as milk, eggs, and meat through animal feed that contains high amounts of pesticide residue.

In the European Union a comprehensive legislative framework was established including rules for the approval of active substances, in which foods they can be used and their permissible residues levels. Pesticide residues are the very small amounts of pesticides that can remain in or on a crop after harvesting or storage. These residues can make their way into food products made from these crops. Pesticide residues also include any breakdown products or metabolites from the pesticide.

Foods are tested for pesticides against maximum residue levels (MRLs) determined by regulatory organisations. MRLs refer to the highest level of pesticide residue that is legally allowed in or on food products and animal feeds, based on good agricultural practices and the minimal amount necessary to protect the crop. MRLs are set by regulatory bodies to ensure that the use of pesticides does not lead to harmful levels of chemical residues in food, thereby protecting consumer health.
These limits are determined after thorough evaluation of scientific data and are meant to be significantly lower than levels that could pose health risks.

The European Food Safety Authority (EFSA) publishes a periodic report that examines pesticide residue levels in foods on the European market. The 2022 report showed that of the food products sampled, 96.3% fell below the MRLs.² This rate was similar to that observed in 2021. Food products that exceeded the MRLs triggered legal sanctions and enforcement actions.

Exceeding an MRL does not automatically mean that the food is unsafe. Instead, if residues exceed the MRL, it could indicate non-compliance with the approved usage instructions, but it does not necessarily imply an immediate health risk. To assess the potential health risk, the sum of pesticide residues across all consumed crops is compared to health-based guidance values such as the Acceptable Daily Intake (ADI). The ADI represents the amount of a pesticide that can be ingested daily over a lifetime without appreciable health risk.³ Each specific pesticide has its own ADI. Estimated dietary exposure to pesticide residues is very low for most EU consumers, indicating a low health risk. In the cases where the estimated dietary exposure for a specific pesticide/product combination exceeded safe levels, or when no safe level for a pesticide could be set, authorities took action to protect by removing the product from the market or recalling it before sale.²

Are pesticides harmful to human health?

Pesticides have direct and indirect impacts on human health. The main route of exposure for humans is through food consumption. Exposure to pesticides leads to both short-term (acute) and long-term (chronic) health issues.⁴ While acute poisoning is uncommon unless an individual works with pesticides on a regular basis, chronic exposure to low doses of pesticides can result in various long-term health problems.⁴

Certain pesticides can act as endocrine disruptors, mimicking or interfering with hormones in the body , which can result in reproductive and developmental disorders.⁵ Continuous exposure to high amounts of toxic pesticides like chlordecone, lindane, endosulfan, and carbofuran is known to cause adverse effects such as liver damage, reproductive system disruption, and neurological impairment.⁴
Pesticides can also disrupt cellular processes and cause DNA damage, potentially leading to development of cancerous cells.⁴ Particularly, the pesticide glyphosate has been linked to an increased risk of developing tumours.⁶

In order to prevent these negative health effects, the use of pesticides and their presence in food is very strictly regulated. EFSA is continuously reviewing the potential toxicity of authorised active substances which are generally approved for a period of 10 years. After this time period it is possible for an applicant to apply for renewal. When assessing the possible negative effects, it is important to remember that the ‘dose makes the poison.’ In other words, the potential toxic effects of pesticides depend on how much people are exposed to. To prevent someone from ingesting too much, EFSA sets a maximum amount for each pesticide that may still be on food. As result, European consumers do not usually come in contact with pesticides in high enough quantities to cause health issues. Eating the recommended 5-a-day (at least 400 g of fruits and vegetables per day) far outweighs any potential negative effects of pesticide residues on fruits and vegetables.

Can pesticides be washed off? Does cooking destroy pesticides?

Yes, washing can help remove some pesticide residues from fresh produce like fruits and vegetables as well as grains, if the residues are on the surface. However, it is important to note that if the pesticide has penetrated the tissues of the food, washing may not be as effective in removing it. Factors like the type of pesticide, its water solubility, and the washing method used can influence how much residue is removed.⁷ For instance, pesticides with higher water solubility are generally easier to wash off. Washing with hot water may also improve the removal of pesticide residues.⁷ Using special fruit and vegetable soaps to wash off pesticides are generally considered unnecessary.⁸

Similarly, cooking can also impact pesticide residues. Blanching, boiling, and frying can lead to the degradation or removal of some pesticides, particularly those that are sensitive to heat or hydrolysis .⁷ However, not all pesticides are affected by cooking, and some may even become more concentrated in the food due to moisture loss.⁷ Peeling or trimming the skin of fruits and vegetables is considered to be an efficient method for reducing pesticide residues. By removing the outer layers, which tend to have higher concentrations of pesticides compared to the insides of the fruit or vegetables, consumers can substantially reduce their exposure in some cases.⁹ However, other valuable components such as dietary fibre, vitamins, and minerals may also be lost in this process.

Do pesticides kill bees?

Pesticides can negatively affect the health of other animals such as birds, fish, small herbivores, and insects. Recently, their impact on bees has been a topic of much discussion. Bees are important for agroecosystems because they pollinate plants, thus allowing the continued production of food.

Pesticides, particularly insecticides, have a significant negative impact on bees. Research shows that when farmers use more insecticides, there is a decrease in the number and variety of wild bees in the surrounding areas shortly after.⁹ Bees can come into contact with these chemicals either by touching them or eating them during pollination. Some insecticides can cause stress in bees, making their bodies work harder to protect themselves.⁹ This can affect their ability to find food and take care of their young and even reduce their lifespan.⁹ Particularly, neonicotinoids, which are a group of highly effective and versatile insecticides, are associated with the decline of bees in Europe.¹⁰

Summary

In summary, pesticides are widely used in agriculture to protect crops from pests and diseases. However, their presence in food raises concerns about potential health risks for consumers. EFSA sets a maximum amount for each pesticide that may still be on food. As result, European consumers do not usually come in contact with pesticides in high enough quantities to cause health issues. Eating the recommended 5-a-day (at least 400 g of fruits and vegetables per day) far outweighs any potential negative effects of pesticide residues on fruits and vegetables. Continued research and regulation are necessary to minimise the risks associated with pesticide exposure while ensuring the safety of our food supply and natural environment.

References

1. Deadman, M. L. (2017). Sources of pesticide residues in food: Toxicity, exposure, and risk associated with use at the farm level. Pesticide Residue in Foods: Sources, Management, and Control, 7-35.
2. European Food Safety Authority (EFSA), Carrasco Cabrera, L., Di Piazza, G., Dujardin, B., Marchese, E., & Medina Pastor, P. (2024). The 2022 European Union report on pesticide residues in food. EFSA Journal, 22(4), e8753.
3. Vicini, J. L., Jensen, P. K., Young, B. M., & Swarthout, J. T. (2021). Residues of glyphosate in food and dietary exposure. Comprehensive Reviews in Food Science and Food Safety, 20(5), 5226-5257.
4. Kalyabina, V. P., Esimbekova, E. N., Kopylova, K. V., & Kratasyuk, V. A. (2021). Pesticides: formulants, distribution pathways and effects on human health–a review. Toxicology reports, 8, 1179-1192.
5. Warner, G. R., Mourikes, V. E., Neff, A. M., Brehm, E., & Flaws, J. A. (2020). Mechanisms of action of agrochemicals acting as endocrine disrupting chemicals. Molecular and cellular endocrinology, 502, 110680.
6. Thongprakaisang, S., Thiantanawat, A., Rangkadilok, N., Suriyo, T., & Satayavivad, J. (2013). Glyphosate induces human breast cancer cells growth via estrogen receptors. Food and chemical toxicology, 59, 129-136.
7. Yigit, N., & Velioglu, Y. S. (2020). Effects of processing and storage on pesticide residues in foods. Critical reviews in food science and nutrition, 60(21), 3622-3641.
8. Food Safety Authority of Ireland. Salads and vegetables. Accessed 27 May 2024.
9. Ara, Z. G., & Haque, A. R. (2021). A comprehensive review on synthetic insecticides: Toxicity to pollinators, associated risk to food security, and management approaches. Journal of Biosystems Engineering, 46, 254-272.
10. Sgolastra, F., Medrzycki, P., Bortolotti, L., Maini, S., Porrini, C., Simon-Delso, N., & Bosch, J. (2020). Bees and pesticide regulation: lessons from the neonicotinoid experience. Biological Conservation, 241, 108356.