How Can Pesticides Be Safe?

Many people may find it difficult to imagine how a pesticide could ever be safe. To understand how that is possible, it is helpful to make the comparison with something more familiar: electricity.

It is hard to envision modern life without electricity. As much as we enjoy and need this source of energy, it involves some hazards. Electricity can, and sometimes does, cause injury or death.  Yet overall, we think of using electricity as a reasonably safe aspect of our lives.

Safety can’t be precisely defined. What we perceive as safe is something where the benefits more than offset the minimal risks. We can enjoy electricity’s benefits with little risk through two main strategies: 1) using low-hazard forms of electricity and 2) keeping ourselves from being exposed to hazardous forms of electricity.

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The Low-Hazard Approach

Increasingly, we power the devices central to our lifestyles with forms of electricity that are practically non-hazardous. The prime examples would be our cell phones, Bluetooth devices, or portable music players that run on low-voltage, direct current electricity which is nearly incapable of causing us harm.  That same, low-hazard approach plays an important role in pesticide safety.

In the middle of the last century, a number of the early pesticides in use were chemicals that were quite toxic to mammals, and thus to humans. The U.S. began to seriously address the issue with the establishment of the U.S. Environmental Protection Agency (EPA) in 1970. Soon, the truly dangerous pesticides were removed from the market or their use was greatly restricted.

Since then, billions of dollars have been spent on the discovery, testing and regulatory review of new, far less toxic pesticide options. In the charts below, I’ve examined the toxicity of crop protection materials that have been used through looking at historical U.S. Department of Agriculture (USDA) data on Washington State apples and California pesticide reporting data from all crops in 2013. In these charts, the toxicity is based on feeding studies with rats or mice, which is used as an indicator of potential toxicity to humans. Other measures of toxicity have similar trends.

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The EPA has four toxicity categories to classify the acute hazards of pesticide products. For use in apple orchards, the data show that pesticides from EPA Category I, Highly Toxic, were never more than 10% of the total pesticides used, and that their use has steadily declined. These would be pesticides as toxic as the nicotine that is sold for e-cigarettes. Only 0.2% of the pesticides applied to California crops in 2013 were in this category.

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EPA Category II, Moderately Toxic, includes materials with toxicity in the same range as the capsaicin in hot peppers or the caffeine in coffee – familiar and even sought-after natural chemicals in our diets. That category represents very limited use on apples today, and only 18% of what growers applied in California apple orchards in 2013.

The pesticide use category that has grown is termed Slightly Toxic (EPA Category III). Toxicity for crop protection materials in this category is in the same range as the citric acid in a lemon or the vanillin in a vanilla bean.

The largest category of pesticides applied to apples and other crops today is Practically Non-Toxic for mammalian consumption (EPA Category IV). Comparing this to our use of electricity, we can see that low hazard is a major strategy through which we minimize pesticide risk.

To understand how something that is designed to kill or otherwise control a pest could be non-hazardous, consider the example of chocolate which has a flavor ingredient that we humans love but which can be toxic to our pet dogs. Chemicals can have different effects on different species. Scientists use the terms specificity and mode of action to describe how chemicals have their specific effects. With modern pesticides, the mode of action is normally the inhibition of some specific enzyme that is important to the viability of the pest. If the enzyme is inhibited by the pesticide, the pest might stop eating, stop growing and/or die.

That enzyme often isn’t one that even exists in humans and other animals ourselves or in other groups of organisms unlike the pest. A modern insecticide usually only affects enzymes that are found in insects or even a few kinds of insects. A modern herbicide might only inhibit an enzyme that is needed for the growth of plants. A modern fungicide inhibits an enzyme in a pathway of enzymes that is found in certain fungi. While all of these products should still be handled with a reasonable degree of caution, they are, like the electricity that powers our cell phones, low hazard and thus low risk. We can feel safe about their use.

Limiting Exposure Risk When There Is a Hazard

We still need the more hazardous forms of electricity (such as the 120 volt alternating current) for needs like lighting, heat, air conditioning etc. To minimize risk, we’ve developed safe guards such as systems of insulated wiring, childproof plugs, circuit breakers and GFCI outlets to keep us from being exposed to that hazard. Where we need 220 volt service, we have even more ways to avoid exposure. To be connected to the grid we need the extremely hazardous, high-voltage electricity coming to us from wherever it is generated. The high-power transmission lines are designed to make it unlikely that anyone will be exposed to that extremely hazardous form of electricity.

Some pesticides that we need to manage certain pests represent a possible hazard to mammals, like humans, or sometimes to other non-target organisms like birds, fish amphibians or aquatic invertebrates. The safe use of these pesticides is all about limiting exposure. For all pesticides used in agriculture, anyone who is directly involved in the mixing or application of the chemical must follow specific requirements regarding protective clothing and equipment. For low-hazard materials, that might just be gloves, closed shoes and a dust mask. For something that could be a significant human hazard, those restrictions would include a respirator and a protective whole-body TYVEC™ suit.

Restrictions can also dictate how soon after an application anyone can re-enter a treated field (re-entry interval or REI). For low-hazard pesticides, that time period can be a few hours or less. For more hazardous pesticides, the REI can be a number of days. For pesticides that are hazardous to fish or other aquatic organisms, restrictions mandate how close applicators can apply them to waterways. Similarly, for pesticides that are hazardous to bees or other pollinators, restrictions control when applicators can apply them relative to bloom times and/or times of the day when bees and other pollinators are working.

For all pesticides, the EPA conducts an extensive risk assessment and uses that information to set up a detailed set of restrictions designed to prevent the existence of any residues of concern to consumers by the time the crop is harvested. The details of this system are discussed in another post titled, Do I Need to be Concerned about Pesticide Residues on and in My Food?

The moral of this story: just like electricity, pesticides can be used in a way that meets our need for clean, productive farming while giving us a comfortable and functional level of safety.

 

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Do You Need to Worry About Pesticide Residues on Your Food?

Dr. Steve Savage, Crop Protection Benefits Research Institute (CPBRI)

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Some of the healthy fruits and vegetable we can enjoy (Image from Wikimedia)

Many Americans have concerns about pesticide residues on food – particularly for fruits and vegetables. In contrast with that oft-communicated perception, the safety of our food supply is well documented. One reason for this disconnect is that there are activist groups (non-governmental organizations) that consistently promote the idea that consumers should buy organic versions of certain crops in order to avoid pesticides. A recent study documented how that sort of message induces some lower income Americans to simply avoid fruits and vegetables all together. The truth is that our food supply is extremely safe because farmers are careful to use pesticides in ways that don’t lead to residue problems at the consumer level and because of rigorous regulation followed by farmers over the last several decades.

The common perception of organic as a safer option in this regard is also at odds with reality. The United States Department of Agriculture (USDA), which oversees organic certification, clearly states on its National Organic Program website: “Our regulations do not address food safety or nutrition.” Organic farmers can and do use pesticides from an approved list, but that list is not based on safety criteria. Organic growers are limited to natural chemicals and to a limited list of synthetic materials. As with any crop protection material, the EPA has the responsibility to evaluate and regulate their safe use. That oversight is why consumers can confidently enjoy both conventional and organic foods.

In this post I will describe the testing, regulatory and training systems that are in place in the US to protect consumers from risks associated with pesticide residues. I will also describe the intense monitoring system that demonstrates year-after-year that this system is working.

All farmers face challenges from a variety of pests and although they use a number of methods to manage those threats, pesticides are a critical part of that “toolbox.” The broad category “pesticide” includes certain chemicals that occur in nature as well as various synthetic chemicals. There are also pesticide products based on living biological agents. The responsibility for pesticide regulation is with the Environmental Protection Agency or EPA. It determines how pesticides can be used safely, based on their particular intrinsic properties, and by restrictions on how and when they can be used.

 

EPA Risk Assessments

Before any new pesticidal product can be sold in the United States, an extensive list of toxicological tests must be performed and reported to the EPA. The company that makes or which will sell the product is responsible for the cost of this testing, but most of the work is performed in contract labs that are closely audited by EPA. The tests evaluate many different facets of potential toxicity for human and environmental health, both in terms of short-term effects (acute toxicity via consumption, by skin exposure, by inhalation exposure…) and long-term effects on development, organ health, reproduction, and potential carcinogenicity. In addition, a great deal of data has to be generated to show what happens to the chemical over time on the food, and in the environment in terms of its persistence, movement, and breakdown into innocuous ingredients. It costs on the order of $286,000,000 and can take more than 10 years to generate all of this required data. EPA then uses these data to conduct an extensive “risk assessment.” Based on that assessment, EPA develops “label requirements” specifying how, on which plants, when, and how much of the pesticide can be used. These risk assessments cover issues of worker safety, environmental impact and also what sort of residues might be left by the time the crop is harvested, and any potential risk to human health.

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Some safe, delicious apples ready for harvest in western Washington this summer

Pesticide Tolerances (or MRLs)

With regard to pesticide residues at harvest, EPA designs the label requirements to make sure that any residues still present when the food gets to the consumer are below what is called a “tolerance.” (Outside the US this is called an MRL or maximum residue limit). The tolerance is set to insure that there is a substantial margin of safety (typically 100-fold) between the allowed residue and any level to establish reasonable certainty of no harm to humans. EPA then sets limits on how much of the pesticide can be applied and how close to when the crop is going to be harvested so that the tolerance is unlikely to be exceeded when farmers use the product.

These tolerances are very conservative limits and represent such small amounts that they can be difficult to envision. For instance, a tolerance might be five (5) parts per million. That can be visualized as to two drops of water in a five (5) gallon carboy. Some tolerances are set as low as one part per billion (e.g. one drop in 528 carboys). In summary, tolerances are extremely small levels of pesticide residue, set as a conservative standard for human safety, and customized to the specific properties of the each chemical.

Training

In order to be allowed to apply pesticides, farmers have to be trained and certified about how to comply with the chemical-specific label requirements. They have to maintain that training through on-going classes.

Is the System Working?

Every year, as part of a USDA effort called the Pesticide Data Program (PDP), thousands of food samples are randomly gathered from normal food channels and consumer markets. The samples are taken to labs where each sample is screened for the presence of hundreds of different chemical residues. The data that the USDA generates is transparently published both in raw and summarized form. Year after year, what the data show is that the system is working! The vast majority of samples have either no detectable residues or residues that are below the assigned tolerances – mostly far below. On 11/29/16 another year of results (2015) were released and once again documented the safety of our food supply.  The fact that a small residue can be detected does not mean it is of concern. Modern analytical chemists have the ability to detect chemicals at very low levels. The reason that the numbers below tolerance are still published is not that they are of concern, but rather as transparent documentation that these products should be of little concern to consumers and regulators.  Several governmental agencies evaluate this information each year and confirm that consumers can confidently enjoy their food supply without concern about pesticide residues.  The FDA also has a residue testing program from which it concludes, “Results in these reports continue to demonstrate that levels of pesticide residues in the U.S. food supply are well below established safety standards.”  California does its own residue testing and concludes, “California tests show low or no pesticide levels in many fruits and vegetables.” Similar residue testing is conducted in Canada and the EU with equally encouraging results.  With this overwhelming body of evidence, how can the fear of residues persist?

What About the “Dirty Dozen List?”

Unfortunately, each year there is an organization called the Environmental Working Group (EWG) that takes the USDA PDP data and grossly misuses it to create a “Dirty Dozen List.” Instead of looking at how detections relate to carefully developed tolerances, EWG essentially treats all detections as significant – an approach that has been completely rejected by independent experts in the field of toxicology. EWG then recommends that certain crops be sought out as organic. Similarly misguided recommendations to purchase organic are published Consumer Reports. This makes no sense, since organic is not a safety certification. In fact, organic crops often have the same sort of low-level, detectable residues of pesticides as conventional (example data from the US and Canada). This point is conveniently ignored by these organizations.

In conclusion, we have a system in the US that both enables farmers to control pests and which protects consumers so that they can enjoy healthy foods without worrying about pesticide residues.

 

You are welcome to comment here and/or to email me at ssavage@croplifeamerica.org