Agricultural Chemicals and Their Harmful Effects on Physical and Mental Health

Heather Campbell
 min read

This post explains how our food is affected by agricultural chemicals and their harmful effects on our health, both physically and mentally.

Farmer In Tractor Sprays Field With Young Crop With Agricultural ChemicalsIn the agricultural sector, many chemicals are used for livestock breeding (e.g., antibiotics) and to protect crops and increase their productivity (e.g., insecticides).

Agricultural chemicals and their harmful effects on physical and mental health: Introduction

The use of chemicals in agriculture is widespread nowadays. As a result, many of these substances are then found as residues in the food that reaches our plates.

Unfortunately, these residues can change the intestinal homeostasis (balance), negatively impacting our physical and psychological well-being.

This article explains the different types of agricultural chemicals and their harmful effects on the health of our bodies and minds.


By 2030, some researchers estimate that the number of antibiotics used in agriculture worldwide will exceed 100,000 US tons.

Antibiotics are used in agriculture not only to treat animal diseases but are often added to the feed in subtherapeutic amounts to promote livestock growth and prevent disease.

A subtherapeutic amount means a dose considered below the optimal dose for treating disease. In effect, it means antibiotics are added preventively to avoid disease occurring in the future.

This practice occurs particularly in underdeveloped countries where there is not yet adequate regulation in the sector.

Human exposure occurs not only through food from treated animals but also through antibiotic residues found in the environment, water, and land on which manure is dumped.

As a result, these antibiotics end up contaminating the food chain.

The inappropriate use of antibiotics is a significant public health problem. Hence, much research has been done to measure the content of these antibiotic residues and metabolites in foods of animal origin (such as meat, milk, and eggs).

For example, in an examination of approximately 150 raw meat samples, higher than average percentages of four antibiotics were found:

  • ciprofloxacin,
  • streptomycin,
  • tetracycline, and
  • sulfanilamide.

The massive use of antibiotics in livestock will significantly contribute to the increase of antibiotic resistance in microorganisms, which can then be transmitted to humans through the food chain.

The phenomenon is aggravated by the fact that molecules identical or similar to those used for humans are often used in animals.

But, this is not the only problem related to the improper use of antibiotics. Namely, these molecules also have a significant negative impact on the intestines, causing inflammation, dysbiosis (imbalance), and deregulation of the immune system.

Excessive use of antibiotics in adult humans can also lead to an irreversible change in the gut microbiota. It can cause a change in the metabolites of the microbiota itself, with harmful effects on the health of the whole organism.


Pesticides are chemical products used to destroy an organism harmful to man or his interests.

These products are widely used in agriculture, raising concerns about their high toxicity for humans and the ease with which these substances spread in the soil and water.

Pesticides remain in the environment for a long time, and many contaminate food products (both plant and animal). Often, cattle are fed contaminated feed.

Many pesticides have already been banned because of their danger to human health. However, some are still used in other countries where they contaminate the food chain and water table.

Residues of several pesticides can often be found in the same food. This makes it extremely difficult to predict the consequences of such exposure on the body and gut microbiota.

According to many studies, pesticides can have harmful health effects even at low doses. Since we still do not fully understand how they act and interact, it is wise to take precautions to ensure consumer protection.

Among the pesticides most used in agriculture, we find:

  • herbicides,
  • insecticides, and
  • fungicides.

Let us now discuss these different types of pesticides.


Herbicides are substances used worldwide to prevent the spread of unwanted weeds.

One of the most dangerous and widely used herbicides is glyphosate.

Herbicides are often used on wheat crops before harvest to speed up maturation. Its residues are found as contaminants in various commercial products derived from wheat grown in North America.

Good to know: North America is one of the biggest users of herbicides. In contrast, many European countries prohibit their use before harvesting.


During routine monitoring in Canada in 2017, approximately 3,200 food products were examined, of which 870 were cereal-based.

The observation was as follows:

  • Approximately 30% of the products contained glyphosate residues, particularly cereals (36.6%).
  • Of this 30%, around 4% contained an amount above the permitted limits.

Several studies have shown that glyphosate can induce an imbalance in the intestines (dysbiosis) because it creates an imbalance between bacteria (commensal and pathogenic bacteria).

Secondly, it can trigger various pathological conditions associated with dysbiosis, such as celiac disease and inflammatory bowel syndrome.

Furthermore, a change in the gut microbiota significantly affects mental health: it can lead to anxiety and subsequent depression.

This imbalance led to:

  • a decrease in “good” (commensal) bacteria, including those producing butyric acid; and
  • an increase in “bad” (pathogenic) bacteria.

The latter were also found to be more resistant to glyphosate.

All of these imbalances in the gut microbiota can have negative consequences due to their impact on the regulation of serotonin production. They can also promote mood disorders, including anxiety and depression.

Good to know: Glyphosate has been shown to affect brain plasticity and maternal behavior toward offspring.

Paraquat and atrazine

Other frequently used herbicides are paraquat and atrazine which are considered toxic substances for humans. These herbicides are both banned in Europe but not in the United States.

  • According to some studies, paraquat causes dysbiosis and consequent oxidative damage.
  • Studies indicate that atrazine is an endocrine disruptor. However, it is still frequently used worldwide in many crops (such as wheat, corn, and sugarcane).

All these products have been shown to alter the intestinal microbiota.


Used to target insect pests, insecticides can also have harmful effects on humans, especially with prolonged exposure. Therefore, a series of studies was conducted to establish their impact on the gut microbiota.

Organophosphate pesticides

One of the broadest categories is organophosphate pesticides (OPPs), such as:

Residues of these OPPs are often found in food, especially in fruits and vegetables.

Our intestines can metabolize these substances into diethyl phosphate, affecting our immune and endocrine systems and damaging our intestinal microbiota.

This may also result in an increase in microbial species related to anxiety behavior.

In addition, organophosphate pesticide-induced dysbiosis appears to cause changes in gut hormones in rats and an increase in pro-inflammatory cytokines. All this leads to a consequent increase in intestinal inflammation.


Diazinon is an organophosphate insecticide widely used in agriculture. It can cause oxidative stress and damage the DNA of intestinal cells. In addition, it can alter the microbiota and cause both metabolic disorders and neurological disorders.


Chlorpyrifos (CPF) is another organophosphate pesticide that is no longer used in Europe and the United States today but is still widely used in other countries around the world. It is found as a residue, especially in fruits and vegetables.

Several research studies have shown that chlorpyrifos can significantly affect biological processes even in lower quantities.

In fact, in studies on mice, it has been shown to cause various disorders, including:

  • dysbiosis,
  • low-grade inflammation,
  • bacterial translocation,
  • increase in intestinal permeability, and
  • decrease in insulin sensitivity.

In another study, it was found that ingestion of low doses of chlorpyrifos by rats during pregnancy resulted in altered behavior of the offspring. Therefore, this suggests that human exposure may compromise their ability to adapt to the environment.

In addition, this insecticide has been found to influence the synthesis of short-chain fatty acids, which are linked to brain function and mood.

Other research has also shown the strong neurotoxic activity of chlorpyrifos and its metabolites.

In fact, by examining a group of U.S. children between the ages of 8 and 12, researchers found that high levels of organophosphate pesticides in the urine led to a greater likelihood of attention deficit and hyperactivity disorder (ADHD).


Another class of insecticides that is also widely used is the neonicotinoids. These cause alterations of the gut microbiota and the immune system in insects and rats, as well as dysbiosis and intestinal inflammation.

Although more research is needed to clarify the effect of neonicotinoids on the human microbiota, their use has generated much debate.

Namely, researchers have shown that these substances negatively impact the health of bees, leading to a sharp decline in their numbers.

This is concerning since these insects are essential for the balance and health of natural ecosystems.

In addition, studies have shown that residues of this class of insecticides have been found in honey samples from around the world.

Other types of pesticides

Permethrin is an insecticide used in agriculture and residential disinfestation.

This insecticide not only produces dysbiosis but can also reduce levels of short-chain fatty acids, which is associated with mood disorders.

Aldicarb is another pesticide that can cause dysbiosis. It can alter the intestinal microbiota in mice, influence their metabolism, and induce oxidative stress.


In agriculture, the main fungicides used are:

All these compounds induce inflammatory responses and intestinal dysbiosis in mice.

For example, after zebrafish were exposed to imazalil, researchers found a decrease in intestinal mucus, and dysbiosis resulting in a reduction of lactobacilli and bifidobacteria.

Azoxystrobin also causes an increase in antibiotic-resistance genes in the gut microbiota of worms.

As for epoxiconazole, this fungicide commonly used in agriculture produces dysbiosis and is also hepatotoxic (toxic to the liver) and nephrotoxic (toxic to the kidneys).

Agricultural chemicals and their harmful effects on physical and mental health: Conclusion

In agriculture, many chemicals are used to cultivate fruits and vegetables and to breed livestock.

It is possible to have residues of these chemicals in our food. These can alter our intestinal microbiota and the health of our body.

It is therefore recommended to choose organically grown foods that use as few chemicals as possible.

In addition, it is advisable to adopt a healthy and natural diet to strengthen our intestinal microbiota as much as possible.

About Heather Campbell

As a nutritionist, my field of specialization is science-based nutritional advice but more importantly, it is my goal to share capturing and inspiring stories, examples and solutions which can help plus-size individuals overcome their specific difficulties. Read More