What Are Pesticides?

The term “pesticide” describes a category of agrochemicals that are used to protect crops from various bacteria and pests, and they are widely used in agricultural processes. Though pesticides have been instrumental in contributing to global agricultural growth, they can be toxic and dangerous to human health.

How Are Pesticides Used in Agricultural Production?

Pesticides include insecticides, molluscicides, nematocides, fungicides, and herbacides and are used to disrupt the ability of certain species to harm crop yields by paralyzing or killing them. Organophosphates and organochlorine pesticides, for example, can cause damage to the nervous systems of unwanted pests by harming neurotransmitting enzymes. The use of pesticides worldwide has grown exponentially over the past sixty years, with approximately 2.3 million tons of industrial pesticides used annually. Agricultural workers generally apply pesticides by spraying them onto crops.

What Are the Human Exposure Pathways for Pesticides from Agriculture?

The spraying of pesticides releases toxins into the air, where they can be inhaled by workers or can travel beyond the area of intended application. Pesticides can also reach people who do not directly work in agriculture when large amounts are washed into streams, lakes, oceans, and groundwater sources by rain or irrigation. The toxins can then be directly ingested in drinking water, or can accumulate in the tissues of aquatic life. Many of the most widely used pesticides have been classified as Persistent Organic Pollutants (POPs), meaning that they have long life-spans, do not biodegrade well, and have the ability to bio-accumulate in living tissue. When large amounts of pesticides build up in food sources, this contaminates the food chain for nearby communities.

What Are the Health Risks Associated with Pesticide Exposure?

According to reports from the World Health Organization, approximately 20,000 agricultural workers die annually from exposure to toxins in pesticides. Though there are many different kinds of pesticides, each with its own particular health impacts from a variety of chemicals, common health effects include skin irritations, respiratory and pulmonary problems, vision loss, damage to nervous and immune systems, birth defects, DNA damage, disruption of the hormonal system, many different forms of cancer, and in some cases, death.

TABLE 16: Chronology of pesticide development (Stephenson and Solomon, 1993)

Period Example Source Characteristics
1800-1920s Early organics, nitro-phenols, chlorophenols, creosote, naphthalene, petroleum oils Organic chemistry, by-products of coal gas production, etc. Often lack specificity and were toxic to user or non-target organisms
1945-1955 Chlorinated organics, DDT, HCCH, chlorinated cyclodienes Organic synthesis Persistent, good selectivity, good agricultural properties, good public health performance, resistance, harmful ecological effects
1945-1970 Cholinesterase inhibitors, organophosphorus compounds, carbamates Organic synthesis, good use of structure-activity relationships Lower persistence, some user toxicity, some environmental problems
1970-1985 Synthetic pyrethroids, avermectins, juvenile hormone mimics, biological pesticides Refinement of structure activity relationships, new target systems Some lack of selectivity, resistance, costs and variable persistence
1985- Genetically engineered organisms Transfer of genes for biological pesticides to other organisms and into beneficial plants and animals. Genetic alteration of plants to resist non-target effects of pesticides Possible problems with mutations and escapes, disruption of microbiological ecology, monopoly on products

 Pesticides & the Lower Susquehanna Watershed

Much of the Lower Susquehanna’s land is in agricultural production. Because we have so many waterways, often adjacent to farmlands, pesticide pollution in our waterways is a very real concern. We review the ongoing science and urge decisionmakers and regulators to protect our waterways and communities. Check out EPA’s new pesticide standards by clicking here.