2,4-D: Concerns about Cancer and Other Serious Illnesses

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Since its introduction in the 1940s, the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) has been widely used to control weeds in agriculture, forestry, and urban and residential settings.

According to documents obtained by public records requests, the U.S. Food and Drug Administration (FDA) forecast sharp increases in the levels of 2,4-D in American food after regulators approved new genetically modified (GMO) crops that tolerate being sprayed directly with 2,4-D. The agency said it expected use of 2,4-D “to triple” after the introduction of these GMO crops. The  U.S. Environmental Protection Agency (EPA) has also approved Dow Agroscience’s “Enlist Duo,” a mixture of glyphosate and 2,4-D for use on GMO corn, cotton and soybean seeds that Dow developed to tolerate the chemicals. 

FDA said 2,4-D use is “expected to triple” due to GMO crops 

Both glyphosate and 2,4-D have been linked to cancer and other health problems, and there is little known about the synergistic toxicity of these chemicals.

Chemical manufacturers are now seeking approval from the U.S. Department of Agriculture (USDA) for five-trait GMO maize seeds that are genetically engineered to tolerate five herbicides: 2,4-D, dicamba, glyphosate, glufosinate and quizaofop.

See our fact sheets on glyphosate and dicamba

What is 2,4-D?

Scientific studies link 2,4-D to certain types of cancer, birth defects, immunosuppression and other health impacts in highly exposed populations including farmers, farmworkers and farming communities. More than 1,000 products containing 2,4-D are sold in the United States. The herbicide, which will kill many broadleaf weeds but not most grasses, comes in many forms, including liquids, dusts, and granules. Use of 2,4-D is so widespread that residues have been detected in surface and groundwater sources.

2,4-D was one of two active ingredients in the “Agent Orange” herbicide formulation used during the Vietnam War, though adverse health effects associated with Agent Orange have been blamed on a separate ingredient – 2,4,5-Trichlorophenoxyacetic acid, and its contaminant, dioxin.

In 2015 the World Health Organization’s International Agency for Research on Cancer (IARC) said a review of scientific literature showed that 2,4-D is “possibly” carcinogenic to humans. IARC said that although there is “inadequate evidence in humans and limited evidence in experimental animals” of ties between 2,4-D and cancer, it based the classification on epidemiological studies that provided “strong evidence that 2,4-D induces oxidative stress … and moderate evidence that 2,4-D causes immunosuppression.”

The IARC classification contradicted a 2007 assessment by the U.S. EPA, which said scientific data did not support a link between human cancer and 2,4-D exposure. The EPA stated that 2,4-D “generally has low toxicity for humans.” However, many experts point out that U.S. regulations have not kept pace with scientific advances for understanding chemical risk. 

Is 2,4-D in our food? 

The EPA allows 2,4-D to be used in the production of fruits and vegetables and is sprayed directly on some crops used for human and animal food. The U.S. FDA has found residues of 2,4-D in food samples but asserts the pesticide traces people consume pose no health dangers. Documents obtained from the FDA through Freedom of Information Act (FOIA) requests show the government forecast sharp increases in the levels of 2,4-D in American food after regulators approved new 2,4-D tolerant crops developed by Dow AgroSciences that tolerate being sprayed directly with the herbicide. 

In March of 2017, the Center for Food Safety and five other organizations sued the EPA over its approval of Dow’s new 2,4-D herbicide, designed to be used with 2,4-D-tolerant crops. The groups alleged the regulatory agency violated its duties under the Pesticide Act and violated its duties to protect endangered species. The group said the agency’s approval of Dow’s “Enlist Duo” product, which combines glyphosate and 2,4-D, was “part of a disturbing, industry-wide trend” in which crops are genetically engineered to withstand being sprayed with multiple pesticides. “While these GE crop systems initially provide a quick-fix way to kill weeds, the intensive spraying triggers rapid evolution of weed resistance to the chemicals. Just as overuse of antibiotics breeds resistant bugs and more antibiotics to kill them, so these GE crop systems drive a toxic spiral of increasing weed resistance and pesticide use.”   

In July 2020 the U.S. Court of Appeals for the Ninth Circuit rejected the claims and ruled that Dow’s Enlist Duo could stay on the market. The court agreed with the petitioners that the EPA did not properly assess harm to the monarch butterflies associated with increased use of 2,4-D. But the court merely instructed the agency to review the risks to monarch butterflies.  

What does science say about health impacts linked to 2,4-D?

Scientific studies link 2,4-D to the following health concerns: 

Non-Hodgkin lymphoma

A systematic review and meta-analysis of studies of associations between 2,4-D and NHL [non-Hodgkin lymphoma] found “new evidence for an association between NHL and exposure to the herbicide 2,4-D… Overall, in our analysis focused on the highest exposure group from each study, we identified a statistically significant association between 2,4-D exposure and increased RRs [relative risks] of NHL.” 2,4-dichlorophenoxyacetic acid (2,4-D) and risk of non-Hodgkin lymphoma: a meta-analysis accounting for exposure levels. Annals of Epidemiology, 2017. 

Systematic review and meta-analyses of nearly three decades of epidemiological research on the relationship between non-Hodgkin lymphoma and occupational exposure to agricultural pesticides finds that “Diffuse large B-cell lymphoma was positively associated with phenoxy herbicide exposure.” Non-Hodgkin Lymphoma and Occupational Exposure to Agricultural Pesticide Chemical Groups and Active Ingredients: A Systematic Review and Meta-Analysis. International Journal of Environmental Research and Public Health, 2014.

A population-based case-control study in Italy found that “the positive association found between phenoxy herbicides exposures and NHL [non-Hodgkin lymphoma], when we restricted the analysis to the subjects who never used personal protective equipment, confirms previously reported associations…” Cancer and Pesticides: An Overview and Some Results of the Italian Multicenter Case–Control Study on Hematolymphopoietic Malignancies. Annals of the New York Academy of Sciences, 2006.

A population-based, case-control study in Nebraska found a “50% excess of NHL [non-Hodgkin lymphoma] associated with mixing or applying 2,4-D. The risk for NHL increased with the average frequency of use to more than threefold among those exposed more than 20 days per year.” A case-control study of non-Hodgkin’s lymphoma and the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) in eastern Nebraska. Epidemiology, 1990.

Birth defects 

Study of rates of adverse birth outcomes in Minnesota, Montana, North Dakota, and South Dakota found that “in rural, agricultural counties where wheat acreage occupies a larger percentage of the land and where use of chlorophenoxy herbicides is higher, anomalies of the circulatory/respiratory and musculoskeletal/integumentary system significantly increased.” Birth Malformations and Other Adverse Perinatal Outcomes in Four U.S. Wheat-Producing States. Environmental Health Perspectives, 2003.

Study of offspring of pesticide appliers in Minnesota found that “the rate of birth defects increased in…offspring born to the general population residing in high-use chlorophenoxy herbicide/fungicide regions…” Pesticide appliers, biocides, and birth defects in rural Minnesota. Environmental Health Perspectives, 1996.

Breast cancer

Case-control study of breast cancer in California farm workers found “suggestive increases” in breast cancer risk “were seen for a phenoxyacetic acid herbicide, 2,4-D, an organophosphate, malathion, and an organochlorine insecticide, chlordane, ” and that the “risk associated with chemical use was stronger in younger women, those with early-onset breast cancer, and those diagnosed earlier.” Breast Cancer Risk in Hispanic Agricultural Workers in California. International Journal of Occupational and Environmental Health, 2013. 

Gastric cancer

Nested case-control study of gastric cancer found that “Working in areas with high use of the phenoxyacetic acid herbicide 2,4-D was associated with gastric cancer…” Agricultural exposures and gastric cancer risk in Hispanic farm workers in California. Environmental Research, 2007. 

Parkinson’s disease 

Case-control study investigating the risk of parkinsonism in occupations found “Three individual compounds, the organochlorine 2,4-dichlorophenoxyacetic acid, the herbicide paraquat, and the insecticide and acaricide permethrin, were associated with more than a 3-fold increased risk of disease”. Occupation and Risk of Parkinsonism: A Multicenter Case-Control Study. Journal of the American Medical Association, 2009.

Amyotrophic lateral sclerosis 

Large nationwide study published in the journal NeuroToxicology (December 2021) reports that “several neurotoxic pesticide exposures estimated using residential location were associated with statistically significant increased risk of ALS (amyotrophic lateral sclerosis). These include the herbicides 2,4-D and glyphosate, and the insecticides carbaryl and chlorpyrifos.” ALS is a progressive nervous system disease that affects nerve cells in the brain and spinal cord, causing loss of muscle control. Pesticides applied to crops and amyotrophic lateral sclerosis risk in the U.S. NeuroToxicology, December, 2021.

Endocrine disruption/thyroid

Study of the association between pesticide use and thyroid diseases found “increased odds of hypothyroidism with ever-use of the herbicides 2,4-D, 2,4,5-T, 2,4,5-TP, alachlor, dicamba, and petroleum oil.Hypothyroidism and pesticide use among male private pesticide applicators in the agricultural health study. Journal of Occupational and Environmental Medicine, 2013.

Sperm disorders/decreased male fertility

Study of the reproductive function of 32 male farmers exposed to 2,4-D found that “2,4-D can affect spermatogenesis in occupationally exposed farmers. The decrease of fertility in exposed subjects results from asthenospermia, necrospermia and teratospermia, frequently associated. The most important pathological aspects of the spermatogenesis of the exposed subjects are increase and permanence over time of abnormal spermatozoa.” Study of reproductive function in persons occupationally exposed to 2,4-dichlorophenoxyacetic acid (2,4-D)Mutation Research Letters, 1991. 

Lipid/glucose metabolism/heart risk

Study on the toxicity of chlorophenoxy herbicides using linear regression found that “exposure to 2,4-D was associated with changes in biomarkers that, based on the published literature, have been linked to risk factors for acute myocardial infarction and type-2 diabetes.” Perturbation of lipids and glucose metabolism associated with previous 2,4-D exposure: a cross-sectional study of NHANES III data, 1988-1994Environmental Health, 2010.

Immunosuppression

Study of blood samples from farmers found that “exposure to commercial 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-chloro-2-methylphenoxyacetic acid (MCPA) formulations may exert short term immunosuppressive effects.” Immunological changes among farmers exposed to phenoxy herbicides: preliminary observations. Occupational and Environmental Medicine, 1996. 

Microbiome perturbations in mice 

Study of sub-chronic low-dose 2,4-D exposure in a mouse model “revealed a distinct gut microbial community with profound changes in diverse microbial pathways including urea degradation, amino acid and carbohydrate metabolism in 2,4-D-treated mice. Moreover, the metabolomics results revealed that the metabolic profiles in treatment group were differentiated from control group in both fecal and plasma samples. Toxic effects on the host of 2,4-D at an occupationally relevant dose were observed indicated by decreased acylcarnitine levels in plasma. These findings indicated that 2,4-D can cause toxicity and substantially impact the gut microbiome in mice at occupationally relevant doses”. Subchronic low-dose 2,4-D exposure changed plasma acylcarnitine levels and induced gut microbiome perturbations in mice. Scientific Reports, 2019.

Where can I find more information about 2,4-D? 

Fact sheets about 2,4-D

Agency for Toxic Substances and Disease Registry, U.S. Department of Health and Human Services: Toxicological Profile for 2,4-Dichlorophenoxyacetic Acid (2,4-D), July 2020.

Natural Resources Defense Council: 2,4-D: The Most Dangerous Pesticide You’ve Never Heard Of.

Beyond Pesticides: Chemical Watch Factsheet 2,4-D

Pesticide Action Network: The risks of the herbicide 2,4-D

Civil Eats: Five Things to Know About 2,4-D, the “Possibly Cancer-Causing Herbicide.”

Journalism and opinion

EPA tosses aside safety data, says Dow pesticide for GMOs won’t harm people, by Patricia Callahan, Chicago Tribune. (12.8.15) “For use on its new genetically engineered corn and soybeans, Dow Chemical Co. is reviving 2,4-D, a World War II-era chemical linked to cancer and other health problems. If these crops are widely adopted, the government’s maximum-exposure projections show that U.S. children ages 1 to 12 could consume levels of 2,4-D that the World Health Organization, Russia, Australia, South Korea, Canada, Brazil and China consider unsafe.” 

Congress questions EPA about Dow’s Enlist Duo pesticide risks, by Patricia Callahan, Chicago Tribune. (2.15.16) “When the EPA approved Enlist Duo in 2014, the agency tossed aside evidence of kidney lesions in lab rats that Dow’s own scientists said were caused by 2,4-D, clearing the way for children to be exposed to levels considered for decades to be unsafe, the Tribune investigation found.”

Reps. Blumenauer, DeFazio, Other Members Call on EPA to Reevaluate Risks of Powerful Herbicide Before Reapproved, Press Release. (2.12.16) “We were concerned to learn that … EPA dismissed a key study linking 2,4-D to kidney abnormalities based on one scientist’s analysis, and in doing so, effectively gave the green light for 41 times more of the chemical to enter the America diet than was previously allowed.”

Agent Orange in Your Backyard: The Harmful Pesticide 2,4-D, by Gina Solomon, The Atlantic. (2.24.12). “Newer science shows that it’s not just a cancer problem, but that this pesticide interferes with several essential hormones, thereby increasing the risks of birth defects and neurologic damage in children. Studies in Midwest wheat-growing areas (where 2,4-D is heavily used) have shown increased rates of certain birth defects, especially in male children, and lower sperm counts in adults.”

Last year it was dicamba, this year it’s 2,4-D, by Johnathan Hettinger, Midwest Center for Investigative Reporting. (3.29.19) “A volatile weed killer linked to cancer and endocrine issues will likely be sprayed on millions more acres of soybeans and cotton across the Midwest and South starting this year. In January, China approved imports of a new genetically modified soybean variety — Enlist E3 soybeans jointly made by Corteva Agriscience, a division of DowDupont and seed company MS Technologies — that can withstand the herbicide 2,4-D.”

What to know before you spray your lawn with pesticides, by Amanda Mascarelli, The Washington Post. (7.7.14) “Researchers are learning a great deal about how vulnerable children’s brains are to pesticides during fetal and early childhood development. “These delicate developmental processes are easily disrupted by very small doses of toxic chemicals that would be virtually harmless for an adult,” said Phil Landrigan, dean for global health and a professor of pediatrics at the Mount Sinai School of Medicine in New York. 

Chemical spray damage results in record $7m negligence court payout, by Clint Jasper, ABC. (8.10.17) A grape grower in Australia was awarded $7 million in damages for losses caused by a neighbor’s negligent spraying of 2,4-D and other chemicals. “The chemical 2,4-D has been at the centre of a number of controversies, including in 2013 when it was revealed imported 2,4-D herbicides contained elevated levels of deadly dioxins.”

WHO unit finds 2,4-D herbicide ‘possibly’ causes cancer in humans, by Carey Gillam, Reuters. (6.22.15)  “IARC’s findings on 2,4-D have been awaited by environmental and consumer groups that are lobbying U.S. regulators to tightly restrict its use, as well as by farm groups and others that defend 2,4-D as an important agent in food production that does not need more restrictions.”

Chemicals on our food: When “safe” may not really be safe, by Carey Gillam, Environmental Health News. (11.27.18) “Toxicologist Linda Birnbaum, who directs the U.S. National Institute of Environmental Health Sciences (NIEHS), has also raised concerns about pesticide dangers through exposures once assumed to be safe …. Last year she called for “an overall reduction in the use of agricultural pesticides” due to multiple concerns for human health, stating that “existing US regulations have not kept pace with scientific advances showing that widely used chemicals cause serious health problems at levels previously assumed to be safe.’”

Chemicals on Our Food: When “Safe” May Not Really Be Safe

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Scientific scrutiny of pesticide residue in food grows; regulatory protections questioned

This article was originally published in Environmental Health News.

By Carey Gillam

Weed killers in wheat crackers and cereals, insecticides in apple juice and a mix of multiple pesticides in spinach, string beans and other veggies – all are part of the daily diets of many Americans. For decades, federal officials have declared tiny traces of these contaminants to be safe. But a new wave of scientific scrutiny is challenging those assertions.

Though many consumers might not be aware of it, every year, government scientists document how hundreds of chemicals used by farmers on their fields and crops leave residues in widely consumed foods. More than 75 percent of fruits and more than 50 percent of vegetables sampled carried pesticides residues in the latest sampling reported by the Food and Drug Administration. Even residues of the tightly restricted bug-killing chemical DDT are found in food, along with a range of other pesticides known by scientists to be linked to a range of illnesses and disease. The pesticide endosulfan, banned worldwide because of evidence that it can cause neurological and reproductive problems, was also found in food samples, the FDA report said.

U.S. regulators and the companies that sell the chemicals to farmers insist that the pesticide residues pose no threat to human health. Most residue levels found in food fall within legal “tolerance” levels set by the Environmental Protection Agency (EPA), regulators say.

“Americans depend on the FDA to ensure the safety of their families and the foods they eat,” FDA Commissioner Scott Gottlieb said in a press release accompanying the agency’s Oct. 1 release of its residue report. “Like other recent reports, the results show that overall levels of pesticide chemical residues are below the Environmental Protection Agency’s tolerances, and therefore don’t pose a risk to consumers.”

The EPA is so confident that traces of pesticides in food are safe that the agency has granted multiple chemical company requests for increases in the allowed tolerances, effectively providing a legal basis for higher levels of pesticide residues to be allowed in American food.

But recent scientific studies have prompted many scientists to warn that years of promises of safety may be wrong. While no one is expected to drop dead from eating a bowl of cereal containing pesticide residues, repeated low level exposures to trace amounts of pesticides in the diet could be contributing to a range of health problems, particularly for children, scientists say.

“There are probably many other health effects; we just haven’t studied them”

A team of Harvard scientists published a commentary in October stating that more research about potential links between disease and consumption of pesticide residues is “urgently needed” as more than 90 percent of the U.S. population has pesticide residues in their urine and blood. The primary route of exposure to these pesticides is through the food people eat, the Harvard research team said.

Several additional Harvard-affiliated scientists published a study earlier this year of women who were trying to get pregnant. The findings suggested that dietary pesticide exposure within a “typical” range was associated both with problems women had getting pregnant and delivering live babies, the scientists said.

“Clearly the current tolerance levels protect us from acute toxicity. The problem is that it is not clear to what extent long-term low-level exposure to pesticide residues through food may or may not be health hazards,” said Dr. Jorge Chavarro, associate professor of the Departments of Nutrition and Epidemiology at the Harvard T.H. Chan School of Public Health, and one of the study authors.

“Exposure to pesticide residues through diet is associated [with] some reproductive outcomes including semen quality and greater risk of pregnancy loss among women undergoing infertility treatments. There are probably many other health effects; we just haven’t studied them sufficiently to make an adequate risk assessment,” Chavarro said.

Toxicologist Linda Birnbaum, who directs the U.S. National Institute of Environmental Health Sciences (NIEHS), has also raised concerns about pesticide dangers through exposures once assumed to be safe. Last year she called for “an overall reduction in the use of agricultural pesticides” due to multiple concerns for human health, stating that “existing US regulations have not kept pace with scientific advances showing that widely used chemicals cause serious health problems at levels previously assumed to be safe.”

In an interview Birnbaum said that pesticide residues in food and water are among the types of exposures that need greater regulatory scrutiny.

“Do I think that levels that are currently set are safe? Probably not,” said Birnbaum. “We have people of different susceptibility, whether because of their own genetics, or their age, whatever may make them more susceptible to these things,” she said.

“While we look at chemicals one at a time, there is a lot of evidence for things acting in a synergistic fashion. A lot of our standard testing protocols, many that were developed 40 to 50 years ago, are not asking the questions we should be asking,” she added.

Legal doesn’t mean safe

Other recent scientific papers also point to troubling findings. One by a group of international scientists published in May found glyphosate herbicide at doses currently considered “safe” are capable of causing health problems before the onset of puberty. More research is needed to understand potential risks to children, the study authors said.

And in a paper published Oct. 22 in JAMA Internal Medicine, French researchers said that when looking at pesticide residue links to cancer in a study of the diets of more than 68,000 people, they found indications that consumption of organic foods, which are less likely to carry synthetic pesticide residues than foods made with conventionally grown crops, was associated with a reduced risk of cancer.

A 2009 paper published by a Harvard researcher and two FDA scientists found 19 out of 100 food samples that children commonly consumed contained at least one insecticide known to be a neurotoxin. The foods the researchers looked at were fresh vegetables, fruits and juices. Since then, evidence has grown about the harmful human health impacts of insecticides, in particular.

Unacceptable levels

“A number of current legal standards for pesticides in food and water do not fully protect public health, and do not reflect the latest science,” said Olga Naidenko, senior science advisor to the non-profit Environmental Working Group, which has issued several reports looking at potential dangers of pesticides in food and water. “Legal does not necessarily reflect ‘safe,'” she said.

One example of how regulatory assurances of safety have been found lacking when it comes to pesticide residues is the case of an insecticide known as chlorpyrifos. Marketed by Dow Chemical, which became the DowDuPont company in 2017, chlorpyrifos is applied to more than 30 percent of apples, asparagus, walnuts, onions, grapes, broccoli, cherries and cauliflower grown in the U.S. and is commonly found on foods consumed by children. The EPA has said for years that exposures below the legal tolerances it set were nothing to worry about.

Yet scientific research in recent years has demonstrated an association between chlorpyrifos exposure and cognitive deficits in children. The evidence of harm to young developing brains is so strong that the EPA in 2015 said that it “cannot find that any current tolerances are safe.”

The EPA said that because of unacceptable levels of the insecticide in food and drinking water it planned to ban the pesticide from agricultural use. But pressure from Dow and chemical industry lobbyists have kept the chemical in wide use on American farms. The FDA’s recent report found it the 11th most prevalent pesticides in U.S. foods out of hundreds included in the testing.

A federal court in August said that the Trump Administration was endangering public health by keeping chlorpyrifos in use for agricultural food production. The court cited “scientific evidence that its residue on food causes neurodevelopmental damage to children” and ordered the EPA to revoke all tolerances and ban the chemical from the market. The EPA has yet to act on that order, and is seeking a rehearing before the full 9th Circuit Court of Appeals.

When asked how to explain its changing positions on chlorpyrifos, an agency spokesman said that the EPA “plans to continue to review the science addressing neurodevelopmental effects” of the chemical.

The fact that it is still in wide use frustrates and angers physicians who specialize in child health and leaves them wondering what other pesticide exposures in food might be doing to people.

“The bottom line is that the biggest public health concerns for chlorpyrifos are from its presence in foods,” said Dr. Bradley Peterson director of the Institute for the Developing Mind at the Children’s Hospital of Los Angeles. “Even small exposures can potentially have harmful effects.”

The EPA decision to continue to allow chlorpyrifos into American diets is “emblematic of a broader dismissal of scientific evidence” that challenges human health as well as scientific integrity, according to Dr. Leonardo Trasande, who directs the Division of Environmental Pediatrics within the Department of Pediatrics at New York University’s Langone Health.

Epidemiologist Philip Landrigan, director of Boston College’s Global Public Health initiative, and a former scientist with the U.S. Centers for Disease Control, is advocating for a ban on all organophosphates, a class of insecticides that includes chlorpyrifos, because of the danger they pose to children.

“Children are exquisitely vulnerable to these chemicals,” said Landrigan. “This is about protecting kids.”

Increased tolerances at industry request

The Federal Food, Drug, and Cosmetic Act authorizes the EPA to regulate the use of pesticides on foods according to specific statutory standards and grants the EPA a limited authority to establish tolerances for pesticides meeting statutory qualifications.

Tolerances vary from food to food and pesticide to pesticide, so an apple might legally carry more of a certain type of insecticide residue than a plum, for instance. The tolerances also vary from country to country, so what the U.S. sets as a legal tolerance for residues of a pesticide on a particular food can – and often is – much different than limits set in other countries. As part of the setting of those tolerances, regulators examine data showing how much residue persists after a pesticide is used as intended on a crop, and they undertake the dietary risk assessments to confirm that the levels of pesticide residues don’t pose human health concerns.

The agency says that it accounts for the fact that the diets of infants and children may be quite different from those of adults and that they consume more food for their size than adults. The EPA also says it combines information about routes of pesticide exposure – food, drinking water residential uses – with information about the toxicity of each pesticide to determine the potential risks posed by the pesticide residues. The agency says if the risks are “unacceptable,” it will not approve the tolerances.

The EPA also says that when it makes tolerance decisions, it “seeks to harmonize U.S. tolerances with international standards whenever possible, consistent with U.S. food safety standards and agricultural practices.”

Monsanto, which became of unit of Bayer AG earlier this year, has successfully asked the EPA to expand the levels of glyphosate residues allowed in several foods, including in wheat and oats.

In 1993, for example, the EPA had a tolerance for glyphosate in oats at 0.1 parts per million (ppm) but in 1996 Monsanto asked EPA to raise the tolerance to 20 ppm and the EPA did as asked. In 2008, at Monsanto’s suggestion, the EPA again looked to raise the tolerance for glyphosate in oats, this time to 30 ppm.

At that time, it also said it would raise the tolerance for glyphosate in barley from 20 ppm to 30 ppm, raise the tolerance in field corn from 1 to 5 ppm and raise the tolerance of glyphosate residue in wheat from 5 ppm to 30 ppm, a 500 percent increase. The 30 ppm for wheat is matched by more than 60 other countries, but is well above the tolerances allowed in more than 50 countries, according to an international tolerance database established with EPA funding and maintained now by a private government affairs consulting group.

“The Agency has determined that the increased tolerances are safe, i.e, there is a reasonable certainty that no harm will result from aggregate exposure to the pesticide chemical residue,” the EPA stated in the May 21, 2008 Federal Register.

“All these statements from EPA – trust us it’s safe. But the truth is we have no idea if it actually is safe,” said Dr. Bruce Lanphear, a clinician scientist at the Child & Family Research Institute, BC Children’s Hospital, and a professor in the faculty of health sciences at Simon Fraser University in Vancouver, British Columbia. Lanphear said that while regulators assume toxic effects increase with dose, scientific evidence shows that some chemicals are most toxic at the lowest levels of exposure. Protecting public health will require rethinking basic assumptions about how agencies regulate chemicals, he argued in a paper published last year.

In recent years both Monsanto and Dow have received new tolerance levels for the pesticides dicamba and 2,4-D on food as well.

Raising tolerances allows farmers to use pesticides in various ways that may leave more residues, but that doesn’t threaten human health, according to Monsanto. In a blog posted last year, Monsanto scientist Dan Goldstein asserted the safety of pesticide residues in food generally and of glyphosate in particular. Even when they exceed the regulatory legal limits, pesticide residues are so minuscule they pose no danger, according to Goldstein, who posted the blog before he retired from Monsanto this year.

About half of foods sampled contained traces of pesticides

Amid the scientific concerns, the most recent FDA data on pesticide residues in food found that roughly half of the foods the agency sampled contained traces of insecticides, herbicides, fungicides and other toxic chemicals used by farmers in growing hundreds of different foods.

More than 90 percent of apple juices sampled were found to contain pesticides. The FDA also reported that more than 60 percent of cantaloupe carried residues. Overall, 79 percent of American fruits and 52 percent of vegetables contained residues of various pesticides – many known by scientists to be linked to a range of illnesses and disease. Pesticides were also found in soy, corn, oat and wheat products, and finished foods like cereals, crackers and macaroni.

The FDA analysis “almost exclusively” is focused on products that are not labeled as organic, according to FDA spokesman Peter Cassell.

The FDA downplays the percentage of foods containing pesticide residues and focuses on the percentage of samples for which there is no violation of the tolerance levels. In its most recent report, the FDA said that more than “99% of domestic and 90% of import human foods were compliant with federal standards.”

The report marked the agency’s launch of testing for the weed killer glyphosate in foods. The Government Accountability Office said in 2014 that both the FDA and the U.S. Department of Agriculture should start regularly testing foods for glyphosate. The FDA did only limited tests looking for glyphosate residues, however, sampling corn and soy and milk and eggs for the weed killer, the agency said. No residues of glyphosate were found in milk or eggs, but residues were found in 63.1 percent of the corn samples and 67 percent of the soybean samples, according to FDA data.

The agency did not disclose findings by one of its chemists of glyphosate in oatmeal and honey products, even though the FDA chemist made his findings known to supervisors and other scientists outside the agency.

Cassell said the honey and oatmeal findings were not part of the agency’s assignment.

Overall, the new FDA report covered sampling done from Oct. 1, 2015, through Sept. 30, 2016, and included analysis of 7,413 samples of food examined as part of the FDA’s “pesticide monitoring program.” Most of the samples were of food to be eaten by people, but 467 samples were of animal food. The agency said that pesticide residues were found in 47.1 percent of the samples of food for people produced domestically and 49.3 percent of food imported from other countries destined for consumer meals. Animal food products were similar, with pesticide residues found in 57 percent of the domestic samples and 45.3 percent of imported foods for animals.

Many imported food samples showed residues of pesticides high enough to break the legal limits, the FDA said. Nearly 20 percent of imported grain and grain product samples showed illegally high levels of pesticides, for example.