Pesticide Residues: The More You Know

November 23, 2016

Pesticide Residues: The More You Know

 By: Dr. Steve Savage, Crop Protection Benefits Research Institute (CPBRI) @grapedoc



Many Americans have concerns about pesticide residues on their food, particularly for fruits and vegetables. Yet, the safety of our food supply in this regard is well documented. NGO’s consistently promote the idea that consumers should buy organic versions of certain crops in order to avoid possibly consuming residues from pesticides. A recent study documented how that sort of message induces some Americans with lower incomes to simply avoid fruits and vegetables all together. The truth is that our food supply is extremely safe due to rigorous regulations instituted by the U.S. Environmental Protection Agency (EPA) and the Food and Drug Administration (FDA).  Farmers are also careful to use pesticides in ways that don’t lead to residue problems at the consumer level.


The common perception of organic as a safer option in this regard is also at odds with reality. The U.S. 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. As with any pesticide, organic-approved products are subject to EPA oversight, and that is why consumers can confidently enjoy either conventional or organic foods.


In this post, I will describe the testing, training and regulatory systems that are in place in the U.S. 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. Pesticide products may also be based on living biological agents. The responsibility for pesticide regulation is with the EPA, which regulates how and when various pesticides can be used safely based on their particular intrinsic properties.


EPA Risk Assessments


Before a company can sell any new pesticide product, researchers must perform an extensive list of toxicological tests and submit the results to the EPA. The company that makes or sells the product is responsible for the cost of this testing, but most of the work is performed in contract labs which are closely audited by the EPA. The tests evaluate many different facets of potential toxicity both in terms of short-term effects (acute toxicity via exposure, e.g., by skin exposure or by inhalation exposure) and long-term effects on development, organ health, reproduction and potential carcinogenicity.


In addition, researchers must generate a great deal of data to show what happens to the chemical over time on food and in the environment in terms of its persistence, movement and breakdown into innocuous ingredients. It costs approximately $286,000,000 and takes more than 10 years to generate all of this required data (See March 2016 Report by Philips McDougall). The EPA uses all this information to conduct an extensive risk assessment. Based on that analysis, the EPA develops label requirements specifying how, when and how much of the pesticide can be used and where it can be used. These rules cover issues of worker safety, environmental impact and what sort of residues might be left by the time the crop is harvested.



Ripe Washington State apples ready for harvest, Photo by Dr. Steve Savage

Crop Protection Benefits Research Institute (CPBRI)


Tolerances (or Maximum Residue Levels)


With regard to harvest residues, the EPA designs the label requirements for the application of pesticides to make sure that any residues still present when the food gets to the consumer are below what is called a tolerance (outside the U.S., this is called a maximum residue level). The EPA sets a tolerance to ensure a substantial margin of safety, typically 100-fold, between the permitted residue level and any level that could even theoretically cause harm to humans. The EPA then sets limits on how much of the pesticide can be applied and how close to when the crop is harvested so that the tolerance is unlikely to ever be exceeded when farmers use the product.


These tolerance levels are conservative and represent such small amounts that they can be difficult to envision. For instance, a tolerance might be five parts per million. That can be visualized as two drops of water in a five-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 quantities set as a conservative standard for safety, customized to the specific properties of the chemical in question.




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


Is the System Working?


Does this system work to protect consumers? That question is evaluated every year as part of a U.S. Department of Agriculture (USDA) effort called the Pesticide Data Program (PDP) (see my related article). Researchers gather thousands of random food samples from normal food channels and take them to labs for evaluation. The USDA screens each sample for the presence of hundreds of different chemical residues. The USDA transparently publishes the data it generates in both raw and summarized form.


Year after year, the PDP data show that the system is working tremendously well (see my related article). The vast majority of samples have either no detectable residues or have residues that are below the assigned tolerances – mostly far below. The fact that researchers can detect a small residue does not mean it is of concern. Modern analytical chemists have the ability to detect chemicals at exceptionally low levels.


The reason the USDA publishes the numbers below tolerance is to transparently document the lack of concern. Several agencies look over this information each year and affirm that consumers can confidently enjoy their food supply without concern about pesticide residues. Researchers conduct similar residue testing in Canada and the European Union (EU) with equally encouraging results (read more about testing in Canada and testing in the EU).


What About the “Dirty Dozen List?”


Unfortunately, each year an organization called the Environmental Working Group (EWG) takes the USDA PDP data and grossly misuses it to create a so-called “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 consumers purchase the organic varieties of certain crops. This makes no sense since organic is not a safety certification. In fact, organic crops often have the same sort of low-level, detectable pesticide residues as conventional crops (see example data from the U.S. and example data from Canada). This point is conveniently ignored by EWG.


So what does this mean for consumers? While information distributed by EWG leads to confusion, consumers can rest assured and eat up, having full confidence in our food supply. Without a doubt, the U.S. food system both enables farmers to control pests and also to protect consumers so that they can enjoy healthy foods without worrying about pesticide residue.