Chapter 33: Pesticides

GENERAL CONSIDERATIONS

Pesticides include chemicals, as well as biological and physical agents, used to control a diverse array of pests. The products used have evolved since the 1930s when arsenic was the principal insecticide used. During and after World War II (WWII), organochlorines and cholinesterase inhibitors supplanted many common uses of arsenic, along with the use of synthetic pyrethrins (pyrethroids). Pesticides currently registered in the United States include 1055 active ingredients formulated into 13,413 separate products.

Typified by cholinesterase-inhibiting insecticides and fumigants, older agents have biologically nonselective mechanisms, accounting for their effects on nontarget as well as target organisms. Agents with selective mechanisms occur as incidental materials in some illness investigations, but less often appear as the primary cause of reported illnesses. As discussed in the chapter subsections for individual use categories, the availability of agents with new modes of action has accompanied a gradual elimination of some compounds used for decades.

PESTICIDE USE

A comprehensive database of the 20 most used pesticide active ingredients on six dominant crops and four aggregated crop classes (PEST-CHEMGRIDS) show the global projection between 2015 and 2025 to be the herbicides glyphosate and metam potassium (about 700,000 tons per year), metam and dichloropropene (about 450,000 tons per year), and 2,4-D (about 150,000 tons per year). The most commonly used insecticides are metam potassium and metam, calcium polysulfide (about 50,000 tons per year), and chlorpyrifos (about 20,000 tons per year). Finally, the most used fungicides are metam potassium, petroleum oil (about 150,000 tons per year), and chlorothalonil (about 120,000 tons per year).

California Sales Data

California pesticide sales data from 2016 reflect the use of both agricultural compounds and antimicrobials. Some agricultural processing operations use antimicrobials, and some compounds listed as antimicrobials were also used as agricultural fungicides.

Reported sales for 2016 totaled 1,806,473,576.17 lb, with 1,516,820,420.66 lb (84%) attributable to antimicrobials. Other pesticides accounted for 289,652,862.51 lb use, with reported agricultural use amounting to 209 million pounds (details provided as follows for the most frequently used compounds). The remaining 80 million pounds represented pesticides used for nonagricultural pest control. Cumulative acreage treated totaled 101 million acres, an average treatment frequency of 3.7 times per year; on average 7.7 lb of active ingredient was used for each of the 27 million cultivated acres of cropland in California.

Most frequently used categories of compounds included chlorine, bromine, and iodine compounds; aldehydes; quaternary ammonium compounds; organic alcohols and glycols; organic acids; and isothiazoline compounds (Table 33–1).