According to the National Center for Environmental Health (NCEH) of the Center for Disease Control, pesticides are substances used to kill, repel, or control pests — any unwanted plant or animal. Pests can cause damage to crops, humans, or other animals, make farming difficult by building homes in or around fields, or kill crops, or other animals.
Shelby Dill, executive director of the Imperial Valley Vegetable Growers Association and the Coalition of Labor, Agriculture and Business of Imperial Valley, explained the use of pesticides.
“Essentially, farmers use pesticides to control weeds, pests, and diseases that will be harmful to the consumer and to the crop. The purpose of pesticides is to protect the health of the consumer, as well as the health of the crop,” said Dill.
Because of the wide variety of different pests, there are several different types of pesticides. Some familiar household products are considered pesticides. For example, insect repellents, cleaning products, and weed killers are all pesticides. Pesticides are categorized by the type of pest they control or the source material in the pesticide.
Disinfectants, or antimicrobials, are designed to kill bacteria, viruses, fungi, mold, and mildew. Many household cleaners used as antimicrobials are pesticides, which is stated on the label. The EPA regulates disinfectant pesticides.
Fumigation is a pest control method that uses gas or vapor to eliminate pests. Fumigants can be released into the air or injected into the soil. Fumigant pesticides are used on grains and other crops after they’ve been harvested to reduce insects such as ticks and mites, nematodes, slugs and snails, and fungal diseases.
Fungicide pesticides are used to kill fungi and their spores on plants and surfaces where mold or mildew grow.
Herbicides, which are designed to kill or control plants, have sub-categories due to the high toxicity of some and the lower risk from exposure of others. Paraquat is a restricted-use herbicide because it concentrates in lung tissue and causes pulmonary damage. Other herbicides are safe enough to be mixed into fertilizers to prevent the growth of certain weeds, while others are used in crop production and home lawn care.
Insecticides are chemicals used to kill unwanted insects. Certain insects — like the olive leaf scorch, whitefly, and asian citrus psyllid — can damage or kill crops. They are classified based on structure and function.
Imperial County Agricultural Commissioner Carlos Ortiz said some pests can be managed through mechanical control, pesticides, or herbicides.
“Pests can be devastating to our County,” said Ortiz.
Repellents, including bugspray and moth balls, are applied to surfaces and discourage pests from landing or climbing on that surface. These can be used to protect people from diseases carried by mosquitoes and ticks.
Rodenticides are used to kill rodents, including mice, rats, squirrels, woodchucks, chipmunks, porcupines, nutria, and beavers. All mammals — including humans, cats, and dogs — are affected by rodenticides in similar ways. Rodenticides, just like all other pesticides, are regulated for safety and health concerns.
“If farmers did not use pesticides, the crops would have to compete with the weeds and insects, and yields would be significantly decreased. The crops could also be lost completely due to these pests,” said Dill.
Because of the widespread use of agricultural chemicals, people are exposed to low levels of pesticides through residues in foods and contaminated drinking water. According to the NCEH, scientists do not have a clear understanding of the chronic health effects of pesticide exposures, which is why the EPA is responsible for approving pesticides and evaluating the risk of pesticides to humans.
The EPA conducts risk assessment when evaluating the risk potential of pesticides. New pesticides are evaluated before they enter the market and existing pesticides are periodically re-evaluated. The process includes an ecological risk assessment, human health risk assessment, and assessments of pesticide cumulative risk.
Before pesticide products can be sold, the EPA must first ensure the product does not pose any unreasonable risks to plants, wildlife, and the environment. The ecological assessment includes a pollinator risk assessment, which is part of a long-term strategy to advance the science of assessing the risks posed by pesticides to bees. The ecological assessment also determines geographically specific pesticide-use limitations for the protection of threatened and endangered species and their designated critical habitats.
The human health risk assessment is the process to estimate the nature and probability of adverse health effects in humans who may be exposed to the chemicals in the product. According to the National Poison Control Center, pesticides were 3.6 percent cause of poisoning exposure reported to poison control centers in 2018.
The EPA also participates in initiatives to reduce pesticide drift, which is the process in which pesticide dust or droplets move through the air at the time of application, or shortly after, to sites other than the intended area. Pesticides can be carried to different areas, including nearby homes, schools, and playgrounds, farm workers in adjacent fields, wildlife, plants, and bodies of water. Pesticide drift can damage nearby crops and affect people’s health and the environment, if not properly applied.
According to the EPA website, it was required to conduct a new type of risk assessment due to the Food Quality Protection Act of 1996. A common mechanism of toxicity is identified when two or more substances cause a common toxic effect by the same sequence of major biochemical events. The cumulative risk assessment is designed to evaluate the risk of a common toxic effect.
Despite possible risks, the NCEH said pesticides may increase crop production, preserve produce, combat insect infestations, and control exotic species.
“The world’s population is projected to reach 9.8 billion people by the year 2020. With an increase in population size, that comes with a larger demand for food. So, we need as large as yields for crops as we can possibly get. It’s really all about sustainability, and pesticide use helps us become more sustainable,” said Dill.