What’s the impact?
Pesticides are known to be dangerous to humans. However, they’re frequently used in agriculture to reduce the number of pests that negatively impact crops. This helps farmers produce more food. However, what happens to the pesticides once the foods are harvested? Do they affect our bodies? What can you do to limit the number of pesticides you consume?
Pesticides are chemical or biological agents, which are sprayed on crops or placed in the soil to control pests, such as insects, rodents, weeds, bacteria, mold, and fungus. This allows farmers to prevent large crop losses and boost the number of crops produced. They’ve helped to increase crop yields in modern farming by two to eight times since the 1940s. So, it’s not surprising that they’re widely used to produce food, like fruits, vegetables, wheat, rice, olives, and canola pressed into oil. They’re also used on non-food crops, including cotton, grass, and flowers. In addition, pesticides are applied to crops that are fed to animals that we consume.
Since there are many kinds of pests, there are several kinds of pesticides. Insecticides target insects and their eggs. Herbicides, or weed killers, prevent other plants from crowding out crops. Rodenticides focus on reducing vermin and rodent-borne diseases. Fungicides help prevent fungal rot on harvested crops and seeds. All of these can be synthetic or organic. Synthetic means they’re created in industrial labs and are designed to be stable, have a good shelf life, and be easy to distribute. They’re also designed to target specific pests and have low toxicity to non-target animals and the environment. Organic, or biopesticides, are naturally occurring chemicals, but they may be reproduced in labs for use in organic farming. Examples of pesticides include organophosphates (OP), carbamates (similar to organophosphates, but they’re less toxic), pyrethroids (laboratory-produced version of a natural pesticide found in chrysanthemums), organochlorines (ex. dichlorodiphenyltrichloroethane, or DDT), neonicotinoids (currently under investigation for unintended harm to bees), glyphosate (ex. Roundup). Some biopesticides include rotenone, copper sulfate, horticultural oils, and Bt toxin. According to 2017 data, the most commonly used pesticides in the US are glyphosate (herbicide), atrazine (herbicide), metolachlor-S (herbicide), dichloropropene (insecticide), and 2,4-D (herbicide). Other statistics find that OP pesticides, especially malathion and chlorpyrifos, are widely used. Several OPs have been banned or restricted due to toxic accidental exposures. When it comes to which one is more harmful, some people feel that synthetic pesticides are because of how they’re designed to have a longer shelf life, they may linger in the body and environment. Others think that organic biopesticides are more detrimental because they’re usually less effective, so they need to be used more often and at higher doses. Considering that both types are technically safe at the low levels, the winner of this debate will probably never be known.
Pesticide residue is found in food and water. They can also run off fields or soak through the ground to enter water sources. A new (2020) Consumer Reports examination of five years of data from the US Department of Agriculture (USDA) found that tests on fruits and vegetables detected about 450 pesticides. According to the World Health Organization (WHO), insecticides are typically more toxic to humans than herbicides. However, the level of harm is dependent on the amount and concentration of the pesticide. The other factor is whether a person gets it on their skin, swallows it, or inhales it. The health effects can be both acute and chronic. Symptoms of acute poisoning may appear immediately or a few hours after exposure. Mild poisoning may include headaches, dizziness, nausea, diarrhea, insomnia, and irritation of the throat, eyes, skin, or nose. Moderate symptoms are blurred vision, confusion, vomiting, constriction of the throat, and rapid pulse. Severe symptoms are chemical burns, unconsciousness, an inability to breathe, and excessive phlegm in the airways. If you’ve been exposed to large quantities of pesticides, call Poison Control at 1-800-222-1222.
The people most at-risk for both acute and chronic illnesses are those who are directly exposed to pesticides, such as agricultural workers who apply pesticides and others in the immediate area during and right after pesticides are spread. One long-running project conducted by the University of California, Berkeley, is the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS). The project was started in 1999, and researchers began following hundreds of Latino children, some before they were born, in Salinas, California. This area grows much of US produce. The findings demonstrate that pesticide exposure for pregnant women and during childhood is linked to poor reflexes in infants (a sign of brain and nervous system problems), lower IQ, attention disorders, poorer lung function, and more. This is especially concerning because individuals who face economic and social challenges are more likely to suffer harm from pesticide exposure because of where they live and work.
When it comes to the general population, exposure is much less because it comes from pesticide residues on food and in water. This doesn’t mean that there isn’t risk involved. Several studies have found that chronic, lower dose exposure to pesticides is associated with respiratory problems, memory disorders, skin conditions, depression, miscarriage, birth defects, cancer, and neurological conditions. For adults, the WHO indicates that coming into contact with large amounts of pesticides could affect reproduction and potentially cause cancer. A 2019 study published in JAMA Internal Medicine followed people for 14 years and found that those with the highest levels of exposure to pyrethroid pesticides were three times as likely to die from cardiovascular disease than those with less exposure. A 2016 analysis in Scientific Reports found a correlation between pesticides and an increased risk of Alzheimer’s disease. Other evidence proposes that pesticides disrupt the endocrine system, which is made up of hormones, the glands that produce them, and the receptors in the body that respond to them. The system is delicate, so even small amounts of pesticides could have significant effects. One study involving children looked at the presence of OP in their urine. For the study, children were switched from conventional to organic diets. Researchers found that the urinary concentration of the OP pesticide metabolite immediately dropped so low it was undetectable. Conversely, when a conventional diet resumed, urine concentration of the OP metabolite increased to previous levels. Children are the most at risk because they eat more relative to their body weight than adults eat. There are many concerns about children’s level of exposure because it can be particularly dangerous if it occurs during vulnerable periods of development. A 2010 study in the journal Pediatrics states that children with greater exposure to OP were more likely to be diagnosed with attention deficit hyperactivity disorder (ADHD).
For many years, the use of pesticides was largely unregulated. However, the impact of pesticides on the environment and human health has been under greater scrutiny since the publication of Silent Spring by Rachel Carson in 1962, which described the issues children who came into contact with pesticides were having. As a result, many different studies were conducted to understand what levels of pesticides are harmful. The information was combined to create limits of safe exposures. The lowest dose of a pesticide causing even the most subtle symptom is known as the lowest observed adverse effect level (LOAEL). Sometimes, the term no observed adverse effect level (NOAEL) is used. To create a threshold for exposure that is considered safe, many agencies take the information and add an extra cushion of safety by setting thresholds 100–1,000 times lower than the LOAEL or NOAEL. This keeps the amounts of pesticides on foods well below harmful levels, and violations of these safety standards are uncommon. Currently, over 1000 pesticides are used worldwide to ensure food is not damaged or destroyed by pests. Unfortunately, many older, cheaper pesticides, such as DDT and lindane, remain in soil and water for years. After the 2001 Stockholm Convention (an international treaty that aims to eliminate or restrict the production and use of persistent organic pollutants), these chemicals were banned by countries that signed the agreement. None of the pesticides used on food in international trade today are genotoxic (damaging to DNA, causing mutations or cancer). The WHO reviews the evidence and develops internationally-accepted maximum residue limits with two objectives in mind. The first is to ban pesticides that are most toxic to humans and any that remain in the environment for a long time. The second is to protect public health by setting maximum limits for pesticide residues in food and water.
Assessments of pesticide residues in food are conducted by an independent, international expert scientific group with representatives from the WHO and FAO (Food and Agriculture Organization of the United Nations), resulting in the Joint Meeting on Pesticide Residues (JMPR). The calculations are based on the data submitted for national registrations of pesticides worldwide as well as all scientific studies published in peer-reviewed journals. Once they review everything, the JMPR sets limits for safe intake to ensure that the amount of pesticide residue people are exposed to through eating food over their lifetime will not result in adverse health effects. Next, governments and international risk managers use these acceptable daily intakes, such as the Codex Alimentarius Commission (the intergovernmental standards-setting body for food), to establish maximum residue limits (MRLs) for pesticides in food. Codex standards are the reference for the international food trade. Presently, there are Codex standards for more than 100 different pesticides.
Here in the United States, the regulation of pesticides falls under several government agencies’ authority, including the Food and Drug Administration (FDA), USDA, and Environmental Protection Agency (EPA). The EPA sets the benchmark for safe levels of pesticides in food by enforcing the 1996 Food Quality Protection Act (FQPA). The FQPA has safety standards that require an explicit determination of whether or not a pesticide’s use on food is safe, especially for children, when used according to label directions. They also look at worker exposure and environmental exposure. Any risks to these can lead to cancelations or restrictions on how and when a pesticide can be used, including establishing ‘no spray’ buffer zones to protect the surrounding communities and waterways. To make these determinations, the EPA evaluates every new pesticide and every new use for safety before registration. To do this, they evaluate hundreds of different scientific studies. They take the findings to independent expert panels, such as the FIFRA Scientific Advisory Panel, and consult the National Academy of Sciences on broad scientific policy questions. In addition, they place a high value on transparency to the public by inviting them to comment on the findings during the process, and any concerns that are risen are taken into consideration before a pesticide is approved. Through all this, the agency considers the toxicity of the pesticide, its breakdown products, how much of it is applied/how often, and how much residue remains in or on food by the time it is marketed. This applies to food grown in the US and imported food. After all the information is considered, the EPA sets a maximum legal residue limit, or tolerance, for each treated food. This is the level that if pesticide residue is above triggers enforcement action, and the product will be subject to seizure by the government. In the first ten years after the FQPA, EPA canceled or restricted the use of 270 pesticides for household and food uses because they posed particular threats. One example is carbamates (a group of insecticides that affect the nervous system). From 1995 to 2013, EPA canceled or restricted many carbamates, and children’s exposure rates fell by 70%. Between 1998 to 2008, the EPA withdrew most organophosphates (OP), resulting in detectable residues on tomatoes falling from 37% to 9%. Once a pesticide is registered, the EPA reevaluates its safety every 15 years, considering any new data. To comply with this, in 2007, the EPA began a review of all old pesticides.
The FDA oversees the safety of our food supply, which includes monitoring pesticide residues in food. The USDA keeps a national list of approved synthetic and restricted organic pesticides. The USDA has the Pesticide Data Program (PDP) that collects, analyzes, and reports pesticide residues on agricultural products in the food supply, principally those consumed by infants and children. Every year, the PDP collects over 10,000 samples on 10-15 food commodities and can detect residues at levels far lower than those that pose health risks. As a result of the PDP data, an overall decrease in pesticide residues in food has occurred. The results are made public every year. According to the 2018 data, over 99% of the tested produce contained safe levels of pesticides, and 47.8% had no detectable residue levels.
When it comes to studying pesticides, scientists are limited in the kind of research they can conduct. One way to get clear answers would be to give a group of people a pesticide-laden diet and another group a pesticide-free one. Since this is unethical, other types of studies must be used. Animal studies are limited because of biological differences between humans and animals. Epidemiological studies look at groups of people, their pesticide exposure, and their health outcomes over long periods of time. While this can link pesticides and illness, it can’t prove that the chemicals caused the diseases. Another factor that needs to be considered, but often isn’t, is that health effects may be compounded when multiple pesticides are used together, which frequently happens. Most studies evaluate only the impact of a single type or class of pesticide. Additionally, pesticides are regulated and studied by considering the effects of the product’s active ingredient, but pesticide formulas contain many other substances, and how they affect health is mostly unknown. One criticism of current pesticide safety limits is that some pesticides contain heavy metals, which build up in the body over time. There hasn’t been much research into the impacts this has on health. Another reproach is that the more subtle, chronic health effects caused by pesticides may not be detectable in the types of studies used to establish safe limits. This is why many experts are saying there should be ongoing monitoring of health outcomes in groups with unusually high exposures to help improve regulations.
One area of particular concern is genetically modified organisms (GMOs). These are crops that have had genes added to them to enhance their growth, versatility, or natural pest resistance. It’s key to realize that historically, wild plants were bred to have better characteristics for farming by selectively planting only the most ideal plants available. This form of genetic selection has been used in every plant and animal in our world’s food supply for centuries. This allowed for changes to be made gradually over many generations. GMOs accelerate this process by using scientific techniques to give the target plant a specific genetic trait. With their increased resistance to pests, they require fewer pesticides. Overall, this doesn’t benefit people eating produce since the risk of pesticides on food is already extremely low, but it could reduce the harmful environmental and occupational health effects of synthetic and organic biopesticides. Some people are concerned that GMOs actually pose a health threat. Multiple comprehensive analyses of human and animal studies conclude there is no evidence to support this.
By the year 2050, the United Nations Population Division estimates that there’ll be 9.7 billion people on Earth, close to 30% more people than in 2017. Most of this population growth will occur in developing countries. The FAO estimates that only 20% of new food production is expected to come from an expansion of farming land. This means that 80% of the necessary increases in food production will come from increases in yields and the number of times per year crops can be grown on the same land. All countries need to look at safe ways to make this happen. In the US, many federal policies need to be tweaked to protect consumers from pesticides better. One crucial task is to create a system that will quickly identify banned pesticides on imported produce to keep it out of the country. This falls under the USDA, which would need to alert the FDA so that they could inform the public. When it comes to home-grown products, bans should be placed on the agricultural use of the riskiest pesticides. This roll belongs to the EPA, but legislation proposed in Congress known as the Protect America’s Children from Toxic Pesticides Act of 2020 (which is still under review as of this publication) would apply the FQPA safety factor to all neurotoxins, suspected endocrine disruptors, and any pesticide for which there’s uncertainty about its safety. This would require the EPA to apply the FQPA consistently. This is critical because a February 2020 analysis in the journal Environmental Health looked at 59 pesticide risk assessments from the EPA between 2011 and 2019 and found that the agency didn’t apply the FQPA safety factor to over 85% of nonorganophosphate pesticides. Also, as of 2020, the agency has completed full endocrine screenings on only 52 pesticides. According to the analyzers, the EPA isn’t using the latest science because the tests they’re using don’t consider new evidence on pesticide harms and haven’t incorporated many new scientific techniques. Many experts also feel that there should be an easy-to-search database of the pesticides currently registered with the EPA that the public can access.
In the meantime, this doesn’t mean that you should avoid eating produce. As it is, close to 80% of Americans don’t get the recommended amounts of at least 2½ cups of vegetables and 2 cups of fruits per day for most adults. You can minimize your risk by choosing fruits and vegetables grown with fewer and safer pesticides. The Environmental Working Group (EWG) publishes the Shopper’s Guide to Pesticides in Produce that categorizes what types of produce are most likely to be contaminated. The ‘Dirty Dozen’ of fruits and vegetables include apples, celery, sweet bell peppers, peaches, strawberries, nectarines (imported), grapes, spinach, lettuce, cucumbers, blueberries (domestic), and potatoes. For all of these products and green beans and kale, the EWG recommends eating organic. The organization also lists 15 fruits and vegetables that are safe to eat conventional versions, such as onions, sweet corn, pineapple, avocado, cabbage, sweet peas, asparagus, mangoes, eggplant, kiwi, cantaloupe (domestic), sweet potatoes, grapefruit, watermelon, and mushrooms. The EWG also points out that pesticide residues can be found in fruit and vegetable juices. The other factor to consider is that the levels of pesticides on produce can be reduced by washing, cooking, and food processing. One study discovered that pesticide levels were diminished by 10–80% by various cooking and food processing methods. Even washing with tap water only can reduce residue levels by 60–70%.
Since rinsing conventional produce doesn’t eliminate all pesticide residue, eating an organic diet is the best way to reduce your exposure. Organic has less pesticide residue because farmers must avoid using pesticides and synthetic fertilizers, protect/improve soil and water quality, promote animal welfare, conserve wildlife, and not use genetically modified organisms. However, organic standards permit the use of some pesticides, but only after nonchemical methods have failed. Even then, the pesticides can’t be harmful to people or the environment. Many people believe that organic products are more nutritious, but there’s no conclusive evidence that they’re more nutritious than conventional food. In fact, one 2017 comprehensive review shows that there’s little difference in the nutrient content between organic and non-organic produce. Also, no studies have shown direct health benefits or disease protection from eating an all-organic diet. Another factor is that because of higher production costs, organic produce’s price is 10-40% higher than conventional produce. Some individuals can’t afford to pay more to have these products.
One area of special consideration is people who work on farms because they’re most at risk of exposure to pesticides. To protect those with direct contact with pesticides, employers should provide them with personal protective equipment, such as clothing that prevents pesticides from coming into contact with the skin or being breathed in. In addition, anyone who works with pesticides should get regular checkups with a healthcare professional. For women who are pregnant or breastfeeding, talk to a doctor before working with pesticides.
While it isn’t possible to completely avoid pesticides in food since their use is so widespread, nobody should be exposed to unsafe amounts. We need to continue to strive to create the ideal pesticide that would destroy its target pest without causing any adverse effects to humans, non-target plants, animals, and the environment. In the meantime, we need to keep in mind that the low levels of pesticides found in foods are unlikely to cause us harm. This doesn’t mean that we don’t take steps to limit our exposure whenever possible, though!