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What You Need to Know About Pesticide Residues

what is pesticide residue

There are currently 7.5 billion people living in 246 countries across six of the seven continents on Earth. Each person consumes around five pounds of food on average per day. That means we need to grow, harvest, process, package, and ship 37.5 trillion pounds of food every day just to keep up with the ever-increasing demand.

As a result, the agriculture industry and food manufacturers face constant pressure to protect crops, produce and livestock from potential threats, and perform risk assessments to ensure that they can produce a sufficient amount of food efficiently and reliably. To do so, they use pesticides.

Pesticides: What Are They & What Do They Do?

Pesticide is an umbrella term that refers to any substance designed to repel or destroy pests. These substances include insecticides, herbicides, fungicides, antimicrobials, miticides, rodenticides and repellents used to protect food from animals, insects, weeds and bacteria.

We most commonly associate the use of pesticides with farming and food crops, but pesticides are used throughout food production and packaging facilities to prevent contamination and to protect against pests during transport.

The Environmental Protection Agency (EPA) distinguishes between "active" and "inert" ingredients found in pesticide compounds.

  • Active ingredients prevent, destroy, repel or mitigate pests, or act as a plant regulator, defoliant, desiccant or nitrogen stabilizer.
  • Everything else is considered an inert ingredient: those that do not play a direct role in protecting food from threats, but help ensure product quality.

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Types of Pesticides

Organochlorine Insecticides

Chlorinated hydrocarbon insecticides include DDT, methoxychlor, chlordane, heptachlor, aldrin, dieldrin, endrin, toxaphene, mirex, kepone and lindane. These substances exhibit an acute effect upon insects by interfering with the transmission of nerve impulses along the axon membrane potassium and sodium channels.

Organophosphate Insecticides

Organophosphates are phosphoric or thiophosphoric acid esters of an organic parent compound. These compounds exhibit excellent insecticidal properties and were quickly put into widespread use in the United States in 1946 as a direct replacement for nicotine for controlling aphids and other cereal insects. Organophosphates, like malathion, inhibit acetylcholinesterase activity of nerve tissue. Buildup of acetylcholine results in tremors, with acute doses causing intense tremors and possible fatality. Lesser doses may cause tightness of the chest, lacrimation (tearing eyes/running nose), sweating, nausea, vomiting, weakness, and cramps.

Organonitrogen Pesticides

Organonitrogens exhibit fungicidal, herbicidal, and insecticidal control as well as plant growth regulation. Triazines like atrazine and cyanazine are commonly employed to optimize corn production. Organonitrogen pesticides also include diuron, linuron, prometron, prometryn and diphenylamine. Organonitrogens produce a myriad of effects including photosynthetic inhibition, acaricide toxicity, phytotoxicity, and fungicidal activities. Organonitrogens are generally regarded as low-risk at residue levels.

Carbamate Pesticides

Carbamates are pesticides consisting of the esters of N-methyl (or occasionally N, N-dimethyl) carbamic acid, whose relative toxicity varies depending on chemical structure. Principally, carbamates are insecticides such as aldicarb, carbofuran, carbaryl, methomyl and propoxur. Carbamates work as acetylcholinesterase inhibitors for insect control, while Dithiocarbamates are used in controlling fungi. Inhibition of enzyme activity is more-rapidly reversed in mammals for carbamates than for organophosphates.

Phenoxy Acid Herbicides

Primarily used to control weeds, particularly broadleaf, by killing the plant through excess stimulation of plant growth hormones. The most common compounds are 2.4-D, 2.4-DB, dichlorprop, dicamba, picloram, and dalapon. Concern over toxicity of phenoxy acid pesticides come from the possible co-contamination with tetrachlorodioxin (TCDD), which is extremely toxic and can be found as a byproduct of manufacturing if the manufacturing processes are not properly controlled.

Other Pesticides

Manufacturing and analytical residue technologies exist for a variety of miscellaneous classes of pesticides, including compounds based on sulfonylurea, pyrethrum, quaternary amine, aminophosphonic acid, and other functionalities. These pesticide classes are difficult to include in multiple residue assays because the methods are dependent on specific matrices.

Pesticide Residues

Whenever pesticides are used, the small amounts that remain in or on fruits, vegetables, grains and other foods are called “residues.” Pesticide residues in food are highly-regulated, and while some residues may remain after harvesting, they naturally decline as the pesticide compound breaks down over time. Residues also decrease when products are processed, packaged, and washed.


Before they can be used by farmers and food producers, every pesticide must clear the Environmental Protection Agency (EPA) Pesticide Registration & Evaluation process. To ensure the safety of our food supply, the EPA regulates the amount of each pesticide that may remain in and on foods under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) and the Food Quality Protection Act (FQPA). This amount is known as the “tolerance level.” If residues are found above maximum residue level, the product will become subject to seizure by the EPA, Food and Drug Administration (FDA) or U.S. Department of Agriculture (USDA).

To help monitor tolerance levels and enforce pesticide regulations, the EPA works with the FDA, (USDA), and local agencies across the U.S.

Pesticide Residue Tolerance Levels

Setting tolerance levels is no easy task because they vary for each food product and pesticide, but the EPA has a strict process for determining if a pesticide can be used with “reasonable certainty of no harm.” To do so, the EPA considers:

  • The toxicity of the pesticide and its breakdown products
  • How much of the pesticide is applied and how often
  • How much of the pesticide residue remains in or on food by the time it is marketed and prepared
  • All possible routes of exposure to that pesticide (residues on each crop use, as well as exposure from drinking water and residential exposure)
  • The dietary risks of human consumption

The National Pesticide Information Center provides a convenient search tool to help find the pesticide tolerance level for specific foods.

Testing for Pesticide Residues

Medallion Labs uses a combination of gas chromatography coupled with time-of-flight mass spectrometry (GC/TOFMS) and ultra performance liquid chromatography coupled with tandem mass spectrometry (UPLC/MSMS) to test for pesticide residues.

Pesticide residues are extracted from samples with high water content (fruits, vegetables, etc.) using acidified acetonitrile, or acetonitrile and water for dry samples. The mixture is then treated with a combination of dry extraction media to isolate the residues in the acetonitrile, which is then cleaned using dispersive solid phase extraction, followed by analysis using both (GC/TOFMS) and (UPLC/MSMS) to identify, confirm and quantitate residue levels.

Sample extracts are compared against a matrix standard to assure accurate quantitation. Internal and quality control standards are also analyzed with each sample to ensure quality results. This method is applicable to fruit, vegetable, grain and beverage samples with less than 15% fat content.

Limits of Detection and Quantitation

Limits of detection (LOD) range from 0.001-0.100 ppm for pesticides analyzed by GC/TOFMS and from 0.00001-0.100 ppm by UPLC/MSMS. To ensure reproducibility, limits of quantitation (LOQ) are established for each analyte. Pesticides detected above the LOQ have demonstrated precision. Pesticides detected above the LOD but below the LOQ have been successfully detected but cannot be accurately quantified.

Identifying which pesticides have come in contact with our food is not an easy task. That’s why we’re happy to provide testing services and expert analysis to help you ensure that your products are consistent, safe for consumption and adhere to federal regulations.

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