Are pesticides in food dangerous? An emergency physician and medical toxicologist answers

Pesticide-related food fears are everywhere. Glyphosate causes cancer. Chemicals in food are making us sick. But what does an emergency physician and medical toxicologist – someone who has spent a career treating actual chemical exposures – actually think about the chemicals used in modern agriculture?

Dr. Liza Dunn spent 16 years as an emergency physician, followed by two years of clinical toxicology work that made her one of the country’s experts in drug overdoses, adverse drug reactions, and pesticide exposures. She is also a mother of three, a humanitarian relief worker who has practiced medicine in Haiti and Kenya, and someone who arrived at her current role as medical affairs lead for Bayer Crop Science not through agriculture but through malnutrition – watching children go blind from preventable vitamin A deficiency and thinking hard about what would actually fix it.

She joined the Food Bullying Podcast to address pesticide and chemical myths directly, explain why a doctor who works in agriculture isn’t a conflict of interest but a public health necessity, and make the case that pesticides are not the threat to human health they’re portrayed as. Glyphosate in particular.

Why doctors should stay in their lane on nutrition and agriculture

This is not a criticism of the medical profession. It’s an observation about training. Medical school is structured around disease: hypertension, diabetes, cancer, cardiac conditions. Nutrition receives minimal formal instruction. Agriculture receives essentially none.

The result, as Dr. Dunn describes it from inside the profession: when doctors speak authoritatively about nutrition or farming practices, they often have less actual information than they realize. The confidence that comes with a medical degree – what she calls the implied power position – can lead patients to act on dietary or food safety advice that isn’t grounded in expertise.

The practical implication: for nutrition guidance, the credential that actually indicates training is RDN. For questions about how food is grown, the people with knowledge are farmers, agricultural scientists, and specialists like Dr. Dunn who have specifically developed expertise at the intersection of medicine and food production. A general practitioner who has read a few news articles about pesticides is not that person.

Why a doctor ended up working in agriculture: malnutrition as a public health crisis

Dr. Dunn’s path from emergency medicine to Bayer Crop Science runs through Haiti twice – once as a 21-year-old who followed her physician father on a medical mission and fell in love with a baby named Fritz, and again after the 2010 earthquake when she organized a relief mission with her residents.

The second trip is where her thinking shifted. She could set broken bones. Deliver babies. Treat infections. But when she left, she left nothing sustainable behind. The underlying problems – malnutrition and insect-borne illness – kept generating the patients she was treating. Fixing the downstream effects without addressing the upstream causes wasn’t medicine. It was a very expensive bandage.

The vast majority of the world’s population lives on three grasses: rice, corn, and wheat. These crops are calorie-dense but often micronutrient-deficient. If you can fortify those staple crops through biotechnology, you can address deficiency diseases at a population scale that no clinic-based intervention can match.

Golden rice, vitamin A deficiency, and the blindness that didn’t have to happen

The most striking example Dr. Dunn offers: golden rice. This is genetically modified rice engineered to produce beta-carotene, a precursor to vitamin A. Vitamin A deficiency is one of the leading causes of blindness in children worldwide. It is entirely preventable.

Golden rice was developed as a public health intervention. The technology was donated and licensed specifically so farmers could grow and replant it freely. It wasn’t a commercial product. It was a gift to address a specific, documented, deadly nutritional deficiency in the populations that need it most.

It has been blocked by Greenpeace for over 20 years.

The opposition rests on GMO fearmongering that the scientific evidence doesn’t support. The claims – that GMOs cause allergy, that they’re toxic, that they’re bad for the environment – have all been tested extensively in the regulatory pipeline. Every GMO crop goes through rigorous evaluation for allergenicity and toxicity before it reaches the market. None of the concerns raised against golden rice have been validated in the evidence. Meanwhile, children continue to go blind from a deficiency that a grain of rice could prevent.

The history of pesticides is actually a history of public health

Before pesticides, soldiers carried flowers into battle. Specifically, chrysanthemums – because chrysanthemums produce a natural chemical called pyrethrum that paralyzes insects. The reason this mattered: across military history, the leading cause of death in combat was not war wounds. It was insect-borne illness. Typhus. Malaria. Yellow fever.

When Napoleon invaded Russia in 1812 with 400,000 soldiers and came out with fewer than 4,000, the conventional explanation was the Russian winter. When archaeologists excavated a mass grave of his soldiers in Lithuania roughly 15 years ago, they found the actual cause: typhus, a louse-borne illness. An insect killed Napoleon’s campaign.

Fast forward to World War II. There was a shortage of pyrethroids and a desperate need for an insecticide with low human toxicity. Swiss chemist Paul Müller discovered DDT. In 1948 he won a Nobel Prize for it. By 1953 the National Academy of Sciences credited DDT with having prevented half a billion insect-borne deaths and a billion insect-borne illnesses worldwide. Sri Lanka recorded just 18 malaria cases that year.

Before DDT, the insecticides available to farmers were nicotine, arsenic, and mercurial compounds – genuinely toxic substances. DDT gave farmers and public health agencies a low-toxicity option for the first time. Locusts, which had been among the most devastating crop pests in history, could now be controlled. A small desert locust swarm can eat food that would feed 35,000 people. There is a current outbreak stretching from East Africa through Yemen, Saudi Arabia, Iran, Pakistan, and India. The food security implications of losing pest control chemistry are not abstract.

From DDT to GMOs: the BT protein story

DDT’s problem, identified by Rachel Carson in Silent Spring, was persistence and non-selectivity. It accumulated up the food chain. It killed insects indiscriminately. It was doing environmental damage that its benefits, however real, couldn’t justify at that scale.

Carson’s recommended alternative was a naturally occurring insecticide produced by a bacterium called Bacillus thuringiensis – BT. BT protein targets specific crop pests. It breaks down quickly. It has very low toxicity for humans. Organic farmers spray it on their crops to this day.

What companies like Bayer, Syngenta, and Monsanto figured out was how to take the gene in that bacterium that produces the insecticidal protein and put it directly into the plant. The plant produces BT protein itself. It no longer needs to be sprayed on from the outside. The result has been a significant reduction in insecticide applications for BT crops – because the protection is built in and precisely targeted.

This is the origin of GMO crops. Not a corporate plot to control the food supply. A public health solution derived directly from a tool that organic farmers already trusted.

Why herbicides protect public health – not just crops

Herbicides kill unwanted plants. The food safety argument against them is that chemicals are being applied near food. The public health argument for them, which Dr. Dunn makes with specific evidence, is that without weed control, toxic plants contaminate the food supply.

In Martinique, 35 people were hospitalized with a severe anticholinergic toxidrome – agitated delirium, hallucinations, hyperthermia – after organic flour was contaminated with datura, a toxic weed. France had to recall a batch of green beans contaminated with the same plant. Abraham Lincoln’s mother died from drinking milk contaminated with white snake root, a weed that concentrates a toxin called tremetol in the tissue of cattle that consume it.

Weed control is not just a yield management strategy. It is the mechanism that keeps toxic plants out of crops, out of animal feed, and out of the food supply.

The environmental case for herbicides adds another dimension: they enable no-till farming. Without herbicides, fields require tillage to control weeds. Tillage releases carbon from the soil, causes erosion, and depletes topsoil. Herbicides allow farmers to plant directly into crop residue, sequestering carbon, reducing erosion, and preserving soil moisture and nutrients. Herbicides, counterintuitively, are one of the tools that make farming more environmentally sustainable.

Is glyphosate safe? An MD and medical toxicologist answers directly

Yes. Dr. Dunn uses glyphosate herself – at her home and at her parents’ property. She describes its safety profile as one of the best on the market: very low toxicity, and no, it does not cause cancer. That assessment comes from someone whose professional training is specifically in chemical exposures and their health effects. It comes from a person who has no ideological stake in agriculture and arrived at this work through humanitarian medicine.

For patients or clients who have questions about glyphosate safety, PesticideFacts.org and the Genetic Literacy Project offer science-based resources for navigating the claims.

Three tips for navigating food chemical myths

Dr. Dunn’s guidance for anyone trying to make sense of food safety information:

1. Focus on nutrition, not what’s absent. Front-of-package claims about what a product doesn’t contain are marketing, not health information. A glyphosate-free label tells you nothing nutritionally meaningful.
2. Get information from credible sources. For nutrition, that means RDNs. For food safety and agricultural chemistry, it means consulting expert resources – PesticideFacts.org and GeneticLiteracyProject.org – not headlines or social media.
3. Recognize that food should be about celebration, not condemnation. Fear-based food decisions don’t improve health outcomes. Evidence-based ones do.

Connect with Dr. Liza Dunn: Follow her on Twitter at @DrLizaMD.

Want to bring an evidence-based, medically credentialed perspective on food safety, GMOs, and pesticides to your next event? Michele Payn speaks to agricultural organizations, agribusinesses, and dietitian associations on food bullying, consumer trust, and the science behind modern food production. Book Michele to speak →