A recent webinar hosted by the Scientific Society of General Medicine (SSMG) tackled some urgent questions: What exactly are pesticides? How are people exposed to them and who is at the greatest risk? What does current science tell us about their toxicity? The event brought together leading experts to revisit foundational knowledge and present the latest research on this widespread yet often misunderstood class of chemicals.
Before delving into the core issues, speakers were quick to make one crucial point, given the sensitivity of the topic: The aim was not to blame farmers.
“They are the first to be exposed to pesticides, and the suicide rate is alarmingly high. We are absolutely not placing the burden of changing agricultural practices on their shoulders,” emphasised Jessica Beurton, MD, holds a Certificate in Environmental Health and is a core member of the Environment Unit at the SSMG.
Beurton then offered a brief reminder of what pesticides are: chemical products used to target and eliminate unwanted entities, such as weeds, insects, or fungi. Of the 800 pesticides used worldwide, approximately 650 are thought to function as endocrine disruptors. According to the World Health Organization, an endocrine disruptor is an exogenous substance or mixture that interferes with endocrine functions and causes adverse health effects in an otherwise healthy individual.
Exposure
With these elements introduced, the presentation began with questions on how people are exposed to pesticides. Ingestion is the primary route, and children are particularly vulnerable; 67% of foods consumed by children contain at least one pesticide residue compared to 37% for adults.
A study conducted by French Agency for Food, Environmental and Occupational Health & Safety found that 100% of the samples from cereals, fruit juices, vegetables, meat, fish, soups, and purees intended for children contained at least one pesticide residue. The same trend applies to foods that are popular among both children and adults, such as sweet biscuits, compotes, and butter.
“Perhaps even more striking, the study revealed the presence of pesticides banned decades ago, such as dichlorodiphenyltrichloroethane (DDT). This illustrates the persistence of these molecules in our environments,” emphasised Céline Bertrand, a paediatric nurse, educator, and member of the Environment Unit at the SSMG.
Residential exposure is also a concern. Pesticides, including DDT, have been detected in household dust, bed linens, and bath towels. “Only a very small portion of the pesticides used in agriculture reach their intended target. The rest is released into the environment — into soil, water, and air,” Bertrand explained.
Residents living near agricultural zones face greater risks. While 80% of pesticide spray settles within the first 10 m of the ground, airborne dispersion is more unpredictable. In some cases, concentrations peak over 50 m away or even 48 hours after application of the pesticide.
However, occupational exposure remains a serious issue. Among the farmers, there was a strong association with Parkinson’s disease, cognitive disorders, and chronic bronchitis. “We also need to clarify the cancer risks among farmers. A large cohort study, AGRICOH, showed higher risks for certain cancers and lower risks for others, likely linked to outdoor activity.”
“However, this cohort included farmers who used pesticides and others who did not. The data show an increased cancer risk in pesticide users.” Bertrand said. Lung cancer was the most common, followed by prostate cancer, multiple myeloma, and colon cancer. Long-term exposure can also affect DNA and hormone levels, and gene expression in pesticide users.
Exposure begins as early as embryonic development. “The first 1000 days of life — from conception — are a critical window of susceptibility to endocrine disruptors. Puberty is another key period of susceptibility,” added Beurton.
The discussion then turned to the toxicity of the pesticides. While acute poisoning remains rare in the general population, chronic exposure is widespread due to contamination of the troposphere. This chronic toxicity, ranging from immunotoxicity and neurotoxicity to cancer, endocrine disruption, and embryo damage, depends on the mode of action of the active molecule and co-formulants, their persistence in the environment, and the toxicity of their breakdown products (metabolites).
“The breakdown of a pesticide produces metabolites that can be more toxic than the parent molecule and can be found in higher concentrations in the blood. This flies under the radar. In Wallonia, we only monitor about 20 pesticide metabolites, which raises questions,” Bertrand noted.
Among the various toxic effects identified are those on brain development before birth. Prenatal exposure to organophosphate and pyrethroid pesticides has been linked to neurodevelopmental disorders, particularly autism spectrum disorders.
“The earlier exposure during development phase in children, the greater the impact,” Bertrand explained. Each year in Europe, exposure to these substances is estimated to result in a loss of 13 million IQ points. It has also been linked to more than 50,000 cases of intellectual disability, 300 cases of autism, and 20,000 cases of ADHD.
Risk
Surprisingly, some pesticides, including DDT, are obesogenic, with effects that span generations.
Studies have shown that mothers exposed to DDT in the 1960s had daughters who were more likely to develop obesity, and this pattern continued into the next generation. “This clearly illustrates the transgenerational epigenetic effects of pesticides,” Bertrand said.
Pesticides also affect fertility in both men and women. For instance, eating fruits and vegetables with high pesticide residues is associated with a lower likelihood of pregnancy and childbirth after infertility treatment. Men who consume the highest levels of such produce have 49% lower sperm counts and 32% fewer normal sperm than those who consume less.
“While it is still difficult to definitively prove cause-and-effect link in environmental health, the body of evidence linking pesticide exposure to neurological and endocrine diseases, childhood cancers, and immune disorders is growing stronger day by day. This should lead us toward the precautionary and even preventative principle,” Bertrand warned. Certain chemicals classified as carcinogenic, mutagenic, or reprotoxic are still used in Belgium.
Toxic Co-Formulants
The webinar then focused on glyphosate, a common herbicide still surrounded by controversy, partly due to efforts to cast doubt on its risks. However, science is becoming clearer. The active ingredient of glyphosate meets 8 out of 10 criteria for being classified as an endocrine disruptor.
A recent study in mice showed that glyphosate can enter the brain and remain there for months. This led to brain inflammation in both healthy mice and those with Alzheimer’s disease and caused early death in the exposed animals.
One study assessed glyphosate and two glyphosate-based formulations in rats using three dose levels: no observed adverse effect level, the acceptable daily intake, and an intermediate dose. In all cases, researchers observed a higher rate of both benign and malignant tumours across multiple organs compared to control animals. “Tumours were found in the blood, skin, liver, thyroid, nervous system, ovaries, mammary glands, adrenal glands, kidneys, bladder, bones, pancreas, uterus, and spleen,” said Bertrand.
In another study, liver cells were exposed to glyphosate and four different formulations. All of them showed harmful effects within 24 hours — even at doses below those typically used in agriculture.
Chronic in vivo regulatory studies typically assess the glyphosate levels alone. However, experts warn that health effects appear to depend more on the overall formulation than on the glyphosate concentration itself. “That is quite concerning,” said Bertrand. “These co-formulants represent the hidden face of pesticides. In many cases, they increase the toxicity of the active ingredient — or are even more toxic than glyphosate itself.”
Laboratory tests have detected a range of hazardous substances in pesticide formulations, including per- and polyfluoroalkyl substances (PFAS), titanium dioxide, heavy metals such as arsenic, lead, and nickel, and polycyclic aromatic hydrocarbons. Notably, PFAS were found in insecticide products even though their presence was not disclosed on the label. “This should prompt us to rethink how we assess pesticide toxicity and take a much closer look at co-formulants, which can be considered the tip of the iceberg,” Bertrand emphasised.
Shifting the Paradigm
The webinar concluded with a broader reflection of the socio-economic implications of pesticide use. Critics often argue that eliminating pesticides would threaten global food security. However, Beurton challenged this narrative. “Pesticides were introduced after World War II when famine was a real threat. This is no longer the case. Today, we understand their health risks, and we are witnessing a serious decline in biodiversity. It is time to change our approach,” she said.
Beurton highlighted emerging research and pilot projects in agroecology that promote local, organic, seasonal, and minimally processed foods. “The majority of farmers themselves are in favour of this paradigm shift. But they do not want to move forward alone: They need support,” she added.
The price of organic and local food is often criticised, but Beurton pointed out that much of the cost comes from the industrial food system itself. “When you break it down, a large portion of the price goes to processing, imports, packaging, marketing, and supermarkets — not the producers. If you want unprocessed food, you need to get it directly from the producer,” she said.
Food Equity
Beurton also noted that community gardens are growing in number and help make quality food more accessible, especially for low-income families. “Food inequality is a serious and growing issue,” she said.
Finally, she addressed the concern that food production would collapse in the absence of pesticides. “Right now, Wallonia imports 83% of the fruits and vegetables and 67% of the cereals it consumes. Therefore, we are no longer producing our own food, which is a big problem. Supporting small, local producers — even those without organic certification — can help rebuild local food systems and create meaningful social connections,” she concluded.
This story was translated from MediQuality.
