Zapping Diazinon

By Steven Zien

In December of 2000, the Environmental Protection Agency (EPA) announced a voluntary agreement with manufacturers to remove and phase out certain uses of the organophosphate pesticide diazinon. (Organophosphates are a group of chemicals derived from nerve gas agents developed during World War II.) This action was taken to address The Food Quality Protection Act (FQPA), enacted in 1996, which sets a more stringent safety standard for most pesticides and offers special protection for children. The FQPA requires the review of more than 9,000 pesticide tolerances by 2006. This new assessment is based on a scientific review that determined diazinon poses risks to humans, birds, and other forms of wildlife. This phase out and removal of some uses of diazinon adds a greater measure of protection for children by eliminating the most important sources of their exposure.

Under the agreement between EPA and the manufacturers, all indoor uses of diazinon will be canceled, and all outdoor residential uses will be phased over the next few years. These actions will end about 75 percent of the current use of diazinon. EPA and the registrants have further agreed to remove about one third of the agricultural crop uses of diazinon. This will help mitigate risks to workers, birds and other wildlife, drinking water resources, and the environment.

About 75 percent of diazinon currently is used in and around the home. It accounts for about 30 percent of the homeowner use insecticide market. Most of this is allocated to outdoor residential uses (39 percent), lawn care operators (19 percent), and pest control operators (11 percent). Home lawn care use accounts for most residential use, but less risk than the indoor use. California, Texas and Florida use the most.

The agreement will result in the termination of all retail sales of diazinon for all indoor uses by the end of 2002. It also ends sales of the residential lawn care use of diazinon in 2003. Production, formulation, and sales to retailers are scheduled to phase out and end completely during 2003.

EPA took this action primarily because of the risk to children to exposure in the home. Potential routes of exposure for children include inhalation of vapors and airborne particles and skin contact. Diazinon is one of the leading causes of acute insecticide poisoning for humans (and wildlife). The majority of human incidents occur in the home.

Symptoms of acute diazinon poisoning in humans include headache, nausea, dizziness, excessive salivation, tearing, blurry vision, slow heartbeat, muscle weakness, loss of coordination, and respiratory depression. Diazinon exposure also causes abnormal eye movements, damage to skeletal muscles, and inflammation of the pancreas. Research with humans and human cells has shown that diazinon can cause genetic damage (mutagenic).

Broadcast application of diazinon to turf poses one of the greatest pesticide risks to birds. Just one granule or seed treated with diazinon is enough to kill a small bird. Diazinon had the highest number of reported bird kill incidents of any registered pesticide from 1994 to 1998. Birds of many species have been killed, including ducks, geese, hawks, songbirds, woodpeckers, and others. Residential use of diazinon accounted for over half of these incidents. Diazinon is also very highly toxic to freshwater fish and invertebrates following acute exposure. Diazinon is highly toxic to bees, as well as beneficial predatory and parasitic insects and mites.

Diazinon is one of the most common pesticides in air, rain, and fog. It is commonly detected in surface waters in urban areas as a result of runoff from residential use. Cancellation of all outdoor residential uses of diazinon is expected to reduce human exposure to diazinon through drinking water, since residential applications are potentially a major source of drinking water contamination.

Stopping the use of diazinon should be easy since there are so many alternatives. This does not mean simply switching to a different synthetic pesticide. The University of California Integrated Pest Management Project recommends that you first properly identify the cause of the pest problem. It may not be an insect that needs treatment, but rather improved watering, drainage, or fertilization. Diseases, herbicide drift, dog urine are other possible causes that need to be ruled out before making an application of any insect control product. Locate and identify the insect before making any application.

In many cases, applications of frequent forceful water sprays can keep the pest within tolerable levels. Bacillus thuringiensis (Bt) is an effective environmentally sound, biological control for a broad range of caterpillar pests in the garden and landscape. Beneficial nematodes, another biological control, can keep over 200 soil borne pests below damaging levels. For crawling insects such as ants, use barriers of sticky stuff (Tanglefoot or Stickem) to keep them at bay. Least toxic pesticides such as insecticidal soap, and horticultural oil, and botanical pesticides such as neem, pyrethrin, rotenone, garlic and various plant oils (such as cinnamon, mint, or basil oil) provide a variety of control options that do not resort to more toxic synthetic pesticides. Remember to always read and follow label directions.

EPA's ban on diazinon was enacted to improve both human and environmental safety. Although the insecticide's use is not immediately being prohibited, it would be prudent to terminate its use now. If you decide to discontinue use, contact your state or local hazardous waste disposal program or the local solid waste collection service for information on proper disposal. You also can refer to the disposal directions on pesticide product labeling. For information on household hazardous waste disposal programs in your area, contact Waste Watch or call 1-800-CLEANUP.

For additional information on the diazinon agreement or other aspects of the Agency's pesticide regulatory program, contact EPA's Office of Pesticide Programs at (703) 305-5017, or visit their web site,

Steven Zien is a member of the Garden Writers Association of America, and he specializes in soils, pesticides, and pest management. He lives in Citrus Heights, California.

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