PANNA: Pesticides and Smog in California


Pesticide Action Network Updates Service (PANUPS)

Pesticides and Smog in California

January 27, 1999

Pesticides used in California fields can cause smog in agricultural regions of the state, according to a report released recently by the Environmental Working Group and Californians for Pesticide Reform. After application, pesticides give off large quantities of reactive organic gases (ROGs, also known as volatile organic compounds) which contribute to formation of smog and which can also cause cancer, birth defects, nerve damage and kidney and heart disease. Approximately 98.9 million pounds of ROGs are emitted from pesticides each year in California — nearly four times the total ROG emissions from petroleum refining, and more than double the ROG emissions from all other industrial sources.

For hours and even days after application, pesticide formulations can evaporate from the soil and vegetation, emitting more chemicals into the air and possibly leading to continued exposure for farmworkers and nearby residents. These evaporating chemicals can include the active ingredients, chemical products of the breakdown of those ingredients and chemical additives — so-called “inert ingredients.” Some pesticides, such as chlorpyrifos and methyl bromide, are so volatile they are considered ROGs.

In California’s San Joaquin Valley, pesticides and fertilizers emit an estimated 34 million pounds of ROGs a year, more than 13% of the region’s total ROG emissions. In Ventura Country, estimated pesticide and fertilizer ROGs are about 2.1 million pounds a year, or 5.6% of the total. In each of these areas, the primary ROG contributor is methyl bromide, which has a potential emissions rate that can be as high as 100%, depending on the brand used.

Because they contribute to formation of smog, ROG emissions are regulated under the U.S. Clean Air Act. To comply with the law, the California Department of Pesticide Regulation (DPR) has established a ROG emissions potential factor for every pesticide registered for use in California. This rating gives the percentage of the chemical that either is or will potentially become airborne ROGs after the pesticide is applied.

As part of the Clean Air Act, each state is required to develop an implementation plan that includes regulations to control ROG emissions. The plan developed by the California DPR has several faults. For example, DPR’s plan does not promote pesticide use reduction as a primary means of reducing emissions. It allows for reductions to be achieved by changing chemical formulations of pesticides or by using a DPR-developed protocol for recalculating emissions factors the agency says will “virtually always” yield a lower emissions factor. In addition, the baseline for the plan was developed by surveying growers who estimated emissions rates of pesticides they used, rather than using data generated by air testing or computer modeling of emissions.

“What You Don’t Know Could Hurt You: Pesticides in California’s Air” also reports on two years of EWG’s air monitoring in counties around the state. Almost two-thirds of the samples contained pesticides known to cause cancer, brain damage, birth defects, acute poisoning or other negative health effects.

The complete report is available online at Copies of the report may be ordered from the EWG, 1718 Connecticut Ave NW, Suite 600, Washington DC 20009; phone (202) 667-6982; fax (202) 232-2592; email for US$20 plus US$3 shipping.

Source/contact: Environmental Working Group California, P.O. Box 29201, The Presidio, San Francisco, CA 94129; phone (415) 561-6698; fax (415) 561-6696; email



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