Pesticides are natural or synthesized chemicals that take care of unwanted environmental pests. The chemical nature of pesticides is dangerous to most living organisms raising concerns as to the environmental impact of pesticides.
Pesticide use is prominent in agriculture, forestry, aquaculture, and food. We can trace the use of pesticides back several centuries. About 4500 years ago, Sumerians used sulfur compounds to control insects and mites. Salt and seawater were effective environmental pesticides used to keep weeds in check.
Another pesticide we used back in the day is a compound from chrysanthemum cinerariaefolium dried flowers2. The compound, known as pyrethrum, has been around for over 2000 years.
In this article, we explore the various pesticides. We will also explore the impact of pesticide use on the environment at large and regulations that prevent chemical pollution.
Farmers and gardeners use various types of pesticides in agriculture and horticulture to control pests, insects, weeds, and fungi.
People use insecticides to control and get rid of insects. There are two main types of insecticides: organophosphate and carbamate. Organophosphate causes the accumulation of acetylcholine at the neuromuscular junctions. The voluntary muscles start twitching rapidly, eventually causing paralysis. Organophosphate is one of the most toxic insecticides in all vertebrates.
Carbamate works just like organophosphate. It causes the accumulation of acetylcholinesterase inhibition, leading to central nervous system effects. Carbamate has a very broad spectrum of toxicity and is highly toxic to fish.
Pyrethroids are also a very effective insecticide against most agricultural pests. It opens the sodium channels in the neuron pathways, which affect the peripheral and central nervous systems. This causes tremors, incoordination, hyperactivity, and paralysis. Similar to carbamate, pyrethroids are highly toxic to fish.
Organosulfur is an insecticide that destroys mite eggs and has low toxicity to other organisms. Organochlorine pesticides cause sodium and potassium imbalance in the neurons, thus preventing normal transmission of nerve impulses. This causes nerve tremors and convulsions.
Herbicides are a type of pesticide used to control unwanted plants. Application is usually before or during planting to minimize the growth of other vegetation and encourage the growth of crops.
We use herbicides in various places and industries. For instance, forest management uses herbicides to prepare for tree replanting. People also apply them to water areas to control aquatic weeds. Using herbicides is common to prevent the growth of unnecessary weeds in lawns, golf courses, and parks.
Fungicides effectively kill plant-like organisms that don't produce chlorophyll, like molds, mildew, and fungi. We use them in various industries like agriculture, home, and garden to protect flowers, grasses, grains, and fruits.
Fungicides work in various ways. There are contact fungicides that protect plants from pathogen infections. The fungicides act like a protective barrier, preventing infections before the symptoms manifest. However, it doesn’t stop the infections deep into the plant’s system from manifesting.
Systemic fungicides move into the plants to treat diseases. However, it has limited movement. Some systemic fungicides have pesticide properties that stop diseases in their developmental stage5.
Rodenticides are pesticide mixtures used to kill rats and mice. There are three classes of rodenticides: first-generation anticoagulants, second-generation anticoagulants, and acute toxicants.
First and second-generation anticoagulants are pesticide mixtures that work by restricting the blood clotting process in rats, resulting in a lethal hemorrhage. They experience severe pain and internal bleeding for several days before they die.
Unlike the other two groups, the third group of rodenticides, known as acute toxicants, is not as dangerous to non-target animals. An example of this chemical is zinc phosphate. It usually kills the animal that ingests it within a couple of hours. There's no antidote for this pesticide, still making it dangerous for non-target animals when consumed in quantity.
Pesticides enter various water sources through runoff and direct application to water to get rid of pests and mosquitoes. When pesticide residues enter aquatic systems, the lives of aquatic organisms are at risk.
Once pesticides enter aquatic systems, they affect aquatic plants. There is a reduction in water's oxygen, which causes behavioral and psychological changes in fish. Pesticide usage is high, leading to the death of multiple fish species.
Aquatic life absorbs pesticides through three different means:
Using pesticides on aquatic plants lowers the levels of oxygen, leading to the suffocation of fish. It also reduces the productivity levels of fish. Atrazine, a common pesticide chemical, is toxic to fish species and amphibians. It affects their mating and looking for food activities and destroys their habitats4. Also, it affects their ability to avoid predators.
In Europe, a study showed that pesticide runoff affects 27 freshwater fish species. Another report shows that a pesticide known as pentachlorophenol (NaPCP) caused many fish deaths in the rice fields of Surinam.
In India, a study shows that pesticides damage the gills, liver, alimentary canal, and brain of carp and catfish. Also, organophosphate pesticides affect catfish production of yolky eggs3.
Amphibians are also deeply affected by pesticide pollution. Herbicide glyphosate and carbaryl are toxic to them, especially tadpoles and juvenile frogs. Frogs living in areas with high pesticide exposure have smaller sizes and weights than frogs living in pesticide-free areas. Also, their stunted growth makes them easily susceptible to infections and diseases.
Read more: 40 Water Pollution Facts & Statistics.
The impact of pesticides on the terrestrial ecosystem; soil properties and its fauna. When agriculturalists use pesticides, it accumulates in the soil. As the pesticides interact with the soil and its microorganisms, it changes their microbial diversity, biochemical properties, and enzyme activities.
Pesticides also affect the functions of beneficial root microbes like bacteria, fungi, and algae in the soil. It influences their growth, colonization techniques, and their metabolisms. Studies showed sulfonylurea herbicides- metsulfuron-methyl, chlorsulfuron, and thifensulfuron methyl reduces the growth of the fluorescent bacteria Pseudomonas strains that were isolated from agricultural soil.
Reducing Pseudomonas strains in the soil decreases soil fertility, which stunts crop growth. Also, compounds benomyl, captan, and chlorothalonil restrict an indicator of microbial biomass known as peak soil respiration.
Some microbial groups use pesticides as a source of energy. This increases their growth and the rate of disruption in the soil. To test this, researchers gathered bacteria from the wastewater irrigation soil. The soil showed that the bacteria could use chlorpyriphos as the carbon source to boost their growth.
The mineralization of the soil to organic matter is an essential factor that determines the soil's quality and productivity. Pesticide concentrations can also affect the soil's vital biochemical reactions, like nitrogen fixation, nitrification, and ammonification. It affects these reactions by activating and deactivating specific soil microorganisms or enzymes.
An example of this is the application of atrazine, primextra, paraquat, and glyphosate to the soil. It reduced the soil's organic matter by a great deal. After treating the soil, its organic matter increased and stabilized itself. Another of the many ways pesticides affect the soil is the disruption of its enzymatic activities.
A change in the soil's enzyme activities indicates soil degradation. Nitrogenase is an enzyme used by organisms to fix atmospheric nitrogen gas. For instance, applying Carbendazim, Imazetapir, Thiam, Captan, 2,4-D, Quinalphos, Monocrotophos, and Endosulfan pesticides reduces the nitrogenase enzyme activity in the soil.
Another example is the application of Cinosulfuron, Prosulfuron, Thifensulfuron methyl, and Triasulfuron pesticides leads to a decrease in the enzyme that hydrolyzes aryl sulfates in the soil.
Read more: 31 Land Pollution Facts and Statistics.
Apart from the impact of pesticides on soil fauna and organisms, pesticide use affects other diversities that live on land.
Pollinators hold a significant role in the pollination process as a biotic agent. Some of these pollinators are honeybees, bumblebees, beetles, and fruit flies. Pesticide pollution affects the activities of pollinators like foraging, colony mortality, and pollen-collecting efficiency. Studies show that using pesticides like imidacloprid, acetamiprid, clothianidin, thiamethoxam, thiacloprid, dinotefuran, and nitenpyram affects bees' foraging behavior, learning, and memory abilities of bees.
Pesticides affect worker bees' mortality rates and reduce their capacity to distribute pollen, leading to colony collapse. The non-lethal exposure of honey bees to neonicotinoid insecticide (thiamethoxam) leads to high mortality rates because of homing failure at a level that puts the colony at risk of collapse.
Imidacloprid is a pesticide commonly used on global agricultural land. Sub-lethal doses of imidacloprid affect the longevity and foraging of honey bees. A study in an Italian agriculture field showed the assignment of pesticides to the decline in bumblebee bee and butterfly species. In addition, they discovered bees had a higher risk of getting affected by insecticides.
Birds hold a significant position in the food chain and the ecosystem. They help maintain balance in the ecosystem by eating insects like mosquitoes, Japanese beetles, and European corn borer moths. Eating these insects helps keep their population controlled. The absence of birds would lead to an enormous population of insects, causing us to increase our usage of pesticides.
However, pesticide pollution can endanger bird populations, especially farmland bird populations. In the United States, almost 50 pesticides caused the death of raptors, songbirds, game birds, shorebirds, and seabirds.
Birds' pesticide exposure occurs through various means, like directly eating granules, seeds, and crops treated with pesticides. They also come in contact with it by drinking contaminated water, eating contaminated prey or bait, and having direct exposure to pesticide spray.
Interaction with pesticides alters the reproductive behaviors of birds. Synthetic pesticides, which contain chemicals like carbamates, organochlorines, and organophosphates, interrupt raptor birds' feeding and reproductive behaviors. The interruption of behaviors often leads to the death of raptors. Some researchers think that the indirect pesticide effects through the food web on farmland bird species might cause death.
Research shows that 10% of the 672 million birds interacting with pesticides on farmlands yearly die. Another study was conducted in the rice fields of Surinam to learn the effects of pentachlorophenol (NaPCP) on birds. Rice farmers usually spray pentachlorophenol (NaPCP) to remove pomacea snails. However, consuming contaminated food caused large numbers of egrets, herons, and jacana birds to fall sick and die.
Pesticides have improved a part of human beings' standard of living as it helps us fight pests. However, just as multiple pesticides cause environmental contamination, they also negatively affect our health. Babies, toddlers, young children, farmers, and pesticide applicators are susceptible to the dangers of pesticide contamination.
According to the World Health Organization, there are 3 million annual cases of pesticide poisoning. They also recorded 220,000 deaths in developing countries yearly.
Toxic pesticides enter our bodies through eating and drinking contaminated edible items, inhalation, and skin absorption. There are three chemical exposure levels with varying intensity.
Acute toxicity refers to the reaction experienced from a single short-term exposure, while subchronic toxicity is from multiple exposures over several weeks or months. Last, chronic toxicity refers to long-term exposure for years1.
An immediate reaction to exposure to pesticides can include:
These reactions are at the early stages of exposure and rarely cause death in victims. However, chronic effects take years of constant exposure to pesticide pollution. These chronic effects which can damage our internal organs are:
Pesticide usage can also disrupt the endocrine system of the human body. This occurs because there are endocrine-disrupting chemicals in pesticides. These chemicals disrupt the functions of hormones by blocking, displacing, or mimicking to take their natural role in the human body.
The endocrine disruptors are organophosphorus, carbamates, Organochlorines, and pyrethroids. There is also Atrazine, an herbicide that has endocrine-disrupting effects on amphibians.
Apart from endocrine disruption, these chemicals are also responsible for other damage. For instance, pyrethroids cause an allergic skin response, aggressiveness, tremors, and seizures. Interaction with organochlorines leads to hypersensitivity to light, sounds, and touch. It also causes dizziness, nausea, tremors, and seizures.
These pesticides also interfere with the normal nerve signal transduction, and exposure to them causes nausea and vomiting, muscle and chest pain, difficulty breathing, convulsions, coma, and death may occur in severe cases.
Known as biological control methods, introducing natural predators or parasites to manage pest populations offers a promising alternative to chemical pesticides. These beneficial organisms target specific pests effectively, reducing the need for environmentally harmful, broad-spectrum chemical pesticides.
For example, introducing ladybugs controls aphids, while using certain nematode species combats various soil-dwelling pests. Enhancing and supporting natural enemies can ensure effective pest control, minimizing ecological disturbances from chemical pesticide use.
Another approach, Integrated Pest Management (IPM), provides non-chemical strategies for pest management and emphasizes cultural, mechanical, and biological controls.
Practices like crop rotation, intercropping, and pest-resistant crop varieties help break pest life cycles and reduce their impact on crop yields. Mechanical controls, such as traps, barriers, and insect vacuums, physically remove or exclude pests from the growing environment.
When combining these techniques with regular monitoring and targeted interventions, IPM reduces our reliance on chemical pesticides.
Many countries and organizations worldwide promote and support using biological controls and IPM strategies in agricultural settings. In the United States, for example, the Environmental Protection Agency (EPA) and the Food and Agriculture Organization of the United Nations (FAO) actively encourage adopting IPM practices.
Similarly, in Europe, the European Union's Sustainable Use Directive promotes the use of IPM and has set requirements for its implementation by member states.
Despite this growing popularity, non-chemical pest management approaches still need to improve in terms of widespread adoption. Some barriers include a need for knowledge and training, limited availability of biological control agents, and initial costs associated with implementing these practices.
However, as awareness of the environmental impact of chemical pesticides continues to grow, adopting biological control methods and IPM strategies will likely become more prevalent in agriculture and horticulture worldwide.
Looking at the terrible impact of pesticides on our environment, we need to take precautions to reduce the damage. We can't completely stop the use of pesticides. Doing that would mean an onslaught of pests in the environment, and it is bad for the global agricultural land and households on a global scale.
So, here is some pesticide regulation advice you can use to prevent chemical compounds in pesticides from contaminating the environment:
Pesticide use is important in environmental science. We can not ignore the detriment of pests and weeds to the environment. However, pesticide degradation has severe and negative environmental factors. It leads to surface water and groundwater contamination and soil fauna contamination.
Water bodies carry pesticides across distances, contaminating everything in their path. It affects non-target biodiversity that interacts with pesticide-contaminated water. Other animals eat other organisms that consume pesticides, like organochlorine pesticides, risking their lives.
Also, chronic exposure to agricultural insecticides takes its toll on human health. We can experience many health problems. For instance, the chemical reactions in our body can lead to immune system failure. It can also disrupt the reproductive systems and destroy our internal organs.
So, let's take environmental protection seriously. We must follow the safety guidelines put in place to prevent pesticide pollution.
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Bernardes, M. F. F., Pazin, M., Pereira, L. C., & Dorta, D. J. (2015). Impact of Pesticides on Environmental and Human Health. InTech. doi: 10.5772/59710
Kaur, H., & Garg, H. (2014). Pesticides: Environmental Impacts and Management Strategies. InTech. doi: 10.5772/57399
Mahmood, Isra & Imadi, Sameen & Shazadi, Kanwal & Gul, Alvina & Hakeem, Khalid. (2015). Effects of Pesticides on Environment. 10.1007/978-3-319-27455-3_13.
Zubrod, J. P., Bundschuh, M., Arts, G., Brühl, C. A., Imfeld, G., Knäbel, A., ... & Schäfer, R. B. (2019). Fungicides: an overlooked pesticide class?. Environmental science & technology, 53(7), 3347-3365.
Jen’s a passionate environmentalist and sustainability expert. With a science degree from Babcock University Jen loves applying her research skills to craft editorial that connects with our global changemaker and readership audiences centered around topics including zero waste, sustainability, climate change, and biodiversity.
Elsewhere Jen’s interests include the role that future technology and data have in helping us solve some of the planet’s biggest challenges.