Pesticide Residue Limits Explained: What Keeps Our Food Safe?

Where do they come from?

Over 1 billion pounds of pesticides are applied yearly to US crops. The rate of corn fields treated with herbicides has gone from between 5%  and 10% in 1952 to around 98% today on a per-acre basis. Similar patterns exist for other major crops, such as cotton and soy^[1]. These pesticides are applied to increase food production, but with such large volumes of something toxic as a requisite component, how can we be sure that the foods we eat are safe?  How are these chemicals assessed, regulated, and monitored to prevent damage to human health and the environment?   

The first stage of protection is registration. Before use, all prospective pesticides must be registered by the EPA. These applications must include, among other information, data on health effects on humans and non-target species and environmental fate. Only after a pesticide is registered can it be used according to specific directions and only on approved crops. Registrations are maintained annually and may be re-assessed by the regulator if new information becomes available or concerns arise. 

Another critical aspect of the safe use of pesticides is the concept of a maximum residue limit (MRL) or Tolerance level, as it is known in the US. The tolerance level is set at a concentration with a "reasonable certainty of no harm." or the No Observed Adverse Effect Level (NOAEL). These levels indicate a legal limit that must not be exceeded for the safe consumption of specific crops. These levels are set at the time of pesticide registration and may be modified based on requested changes to the registration. The setting of these levels involves investigating both potential acute and chronic toxicity as well as the mechanism of toxicity, such as carcinogenicity, endocrine disruption, reproductive toxicity, etc.

Other critical factors considered are the potential exposure to the chemical in terms of what amount of the food in question is likely to be consumed and the protection of vulnerable subsets of the population such as infants, children, seniors, and pregnant people. Globally, most jurisdictions have a similar approach to the setting of MRLs; some may emphasize different aspects of the data. Europe, for example, emphasizes the breakdown of products of the parent pesticide due to plant metabolism or environmental degradation. It must also be noted that global pesticide limits, although variable between jurisdictions, are becoming increasingly harmonized to make globally traded commodities safe and more easily traded. In virtually all jurisdictions, the MRL / Tolerance level has legal standing, and exceedance will typically be dealt with by the seizure of the product and possibly additional legal action. 

This science-based risk management approach keeps our food supply safer for the most part. The underpinnings of this system are a robust and accurate testing regimen that is applied such that accidental exceedances, along with intentional off-label uses and quantities, are caught before they enter the market. Studies by the European Food Safety Authority in 2016 indicated that conventional (i.e., non-organic) crops were 98% compliant with MRLs. This is consistent with newer (2022) data in North America that indicated over 95% of conventional food materials (both plant and animal-based) were compliant with tolerance limits. We believe these high levels of compliance would be unlikely without a robust testing regime to enforce the legal limits. 

To learn more about how pesticide limits are set and monitored, visit our Pesticides page or contact us for further guidance on pesticide safety and compliance testing.

References 

[1] Fernandez-Cornejo, J., Nehring, R., Osteen, C., Wechsler, S., Martin, A., & Vialou, A. (2014). Pesticide use in U.S. agriculture: 21 selected crops, 1960-2008 (Economic Information Bulletin No. 124). United States Department of Agriculture, Economic Research Service. https://www.ers.usda.gov/webdocs/publications/43854/46734_eib124.pdf