Toxicity-Adjusted Exposure to N-Methyl Carbamate and Organophosphate Pesticides in Food

Pesticides are substances or mixtures of substances intended for preventing, destroying, repelling, or mitigating plant or animal pests. They include herbicides, insecticides, fungicides, and rodenticides. More than a billion pounds of pesticides are used in the U.S. each year to control weeds, insects, and other organisms that undermine food production or threaten human health (U.S. EPA, 2017a). Biomonitoring data indicate that people are exposed to pesticides (see Urinary Pesticides). The potential health effects from these exposures—and the main routes by which people are exposed—vary by pesticide, but residue monitoring data suggest that diet is an important route of exposure for many pesticides.

This indicator describes trends in food exposures to two classes of pesticides that have common mechanisms of toxicity: N-methyl carbamates (NMC) and organophosphates (OP). The indicator considers exposure from multiple foods and determines a combined toxicity-weighted exposure to these pesticides. It does not include pesticide exposure through drinking water, because no nationally representative source of pesticide residue data in drinking water exists over time as it does for pesticide residues in food. Dietary exposure modeling techniques developed by EPA’s Office of Pesticide Programs (OPP) are used to estimate NMC and OP cumulative exposures for 1- to 2-year-old children in the U.S. population from 1995 to 2020. The estimated exposures in this indicator account for relative toxicities of individual pesticides within each pesticide class, consumption amounts, consumption frequencies, and pesticide residue levels that would lead to the highest potential for exposure (at the per capita 99.9^th percentile). The indicator tracks changes in pesticide residues over time; it incorporates consumption and toxicity—treated as constant—to show whether changes in residues are important with respect to the amounts of residues being consumed and their relative toxicity. EPA chose children 1 to 2 years old as the sentinel demographic subgroup because children tend to have higher dietary exposures than adults due to their higher food intakes relative to their bodyweights. This indicator also describes the total toxicity-adjusted pounds of NMC and OP pesticides applied to food crops from 1998 to 2019.

Consistent with requirements under the Food Quality and Protection Act (FQPA) of 1996, this indicator looks at pesticides that appear to pose the greatest risk to public health. EPA chose NMC and OP pesticides for this indicator because of their documented toxicities and the availability of publicly available, peer-reviewed cumulative risk assessment (CRA) approaches. Also, these two pesticide groups continue to have important agricultural uses, though EPA has taken measures to restrict or reduce many uses of these pesticides. Note that these indicators describe trends in dietary exposure and pesticide use, but not trends in dietary risks or health outcomes.

The indicator presents two toxicity-adjusted exposure metrics. The first is based on the food exposures from 1995 to 2020 and the second is based on the total pounds of NMC and OP pesticides applied to food crops from 1998 to 2019. Both are reported using the toxicity-adjustment factors for individual pesticides. These metrics are indexed to the year 2006 by dividing the value for a given year by the corresponding value for 2006 and multiplying by 100. EPA chose 2006 as the base year for this indicator because it was the tenth year after the passage of the FQPA, at which point EPA was required by law to have reviewed all pesticide tolerances under stricter FQPA criteria. Additionally, both the NMC and OP CRAs were published during the same timeframe (2006–2007). The indicator uses proprietary data for the toxicity-adjusted pounds applied metric and pulls pesticide residue data from the U.S. Department of Agriculture’s (USDA’s) Pesticide Data Program (PDP), food consumption data from a long-running federal dietary intake survey, and toxicity data from EPA’s risk assessments for NMC and OP pesticides for the toxicity-adjusted food exposure metric.

Toxicity-adjusted food exposures of children to NMC and OP pesticides have decreased over time and toxicity-adjusted pounds of NMC and OP pesticides applied to food crops have also decreased over time.

• Food exposure to NMC pesticides decreased by about 60 percent from 1995 to 2006 and by an additional 30 percentage points from 2006 to 2020, for a total decrease of about 90 percent from 1995 to 2020 (Exhibit 1).
• Food exposure to OP pesticides decreased by about 20 percent from 1995 to 2006 and by an additional 30 percentage points from 2006 to 2020, for a total decrease of about 50 percent from 1995 to 2020 (Exhibit 2).

The numbers of toxicity-adjusted pounds of these pesticides applied each year also show notable decreases.

• For NMC pesticides, the number of pounds applied per year decreased by about 50 percent from 1998 to 2006, and by an additional 40 percentage points from 2006 to 2019 (Exhibit 1), for a total decrease of about 90 percent from 1995 to 2019.
• For OP pesticides, a more marked decline is observed. OP pesticide usage declined by 75 percent from 1998 to 2006, then another 15 percentage points from 2006 to 2019 (Exhibit 2), for a total decrease of about 90 percent from 1995 to 2019.

• This indicator does not cover other pesticides that children could be exposed to through food consumption. Exposure to other pesticides increased and exposure to new pesticides occurred as NMC and OP pesticides were replaced. Decreasing use of and exposure to NMC and OP pesticides is likely to result in more use of and exposure to other pesticide classes, which may include “safer” chemistries with lower toxicity.
• USDA’s PDP does not analyze every food commodity for every NMC and OP pesticide. Over time, USDA has generally expanded the set of pesticides and metabolites analyzed and has used better and better methods to detect chemicals at lower concentrations. However, due to budget constraints, USDA may stop analyzing some chemicals in some commodities (in cases where those chemicals need separate analyses and are not believed to be present in the commodities).
• USDA’s PDP does not sample every commodity each year. This indicator addresses that limitation by using the temporally closest available data for missing years.
• While EPA has received newer toxicological data for some NMC and OP pesticides since the corresponding CRAs were published (U.S. EPA, 2006, 2007), it has not updated the relative potency factors (RPFs) for these chemicals.

The annual 1995–2020 pesticide residue data used in this indicator are from the USDA PDP (USDA, 2017), available from https://www.ams.usda.gov/datasets/pdp. Food consumption data are from the What We Eat in America—Food Commodity Intake Database (U.S. EPA, 2017b) for 2005–2010, publicly available at https://fcid.foodrisk.org. The oral RPFs used in indicator derivation are available in EPA’s CRAs for NMC (U.S. EPA, 2007) and OP (U.S. EPA, 2006) pesticides. The pesticides included in this indicator and their corresponding RPFs (adjusted for their chemical-specific FQPA safety factors and interspecies uncertainty factors) are provided in Section 7 of the technical documentation for this indicator. The data underlying the toxicity-adjusted pounds applied to crops metric are proprietary and are available in an aggregated form. The index values in the exhibits are from EPA OPP (EPA, 2022).

USDA (United States Department of Agriculture). 2017. Pesticide Data Program (PDP) annual data (1995–2020). https://www.ams.usda.gov/datasets/pdp.

U.S. EPA (United States Environmental Protection Agency). 2022. Model output from DEEM-FCID, Version 4.02, from the Office of Pesticide Programs.

U.S. EPA. 2017a. Pesticides industry sales and usage: 2008–2012 market estimates. https://www.epa.gov/sites/production/files/2017-01/documents/pesticides-industry-sales-usage-2016_0.pdf (PDF) (32 pp, 790K).

U.S. EPA. 2017b. Food Commodity Intake Database: What we eat in America. https://fcid.foodrisk.org.

U.S. EPA. 2007. Revised N-methyl carbamate cumulative risk assessment. EPA-HQ-OPP-2007-0935-0003. https://www.regulations.gov/document/EPA-HQ-OPP-2008-0347-0029.

U.S. EPA. 2006. Organophosphorus cumulative risk assessment: 2006 update. EPA-HQ-OPP-2006-0618-0002. https://www.regulations.gov/document/EPA-HQ-OPP-2006-0618-0002.