The Facts About Diazinon

Why is diazinon dangerous?

December 5, 2000

The Facts About Diazinon: Memo to Garden Writers

Diazinon was safe, now it isn't


December 5, 2000

TO: Garden writers
FR: Sean Gray, Environmental Working Group Pesticide Policy Analyst
RE: New EPA decision phasing out diazinon

Within the last six months, the U.S. Environmental Protection Agency (US EPA) has sharply restricted the nation's #1 and now #2 home use insecticides, Dursban and diazinon. Both these chemicals are organophosphates, or nerve gas derivatives, and the EPA determined that they were too dangerous to use in the home and especially around children. But, the removal of Dursban and diazinon from the marketplace means gardeners nationwide will be asking you about better ways to keep unwanted pests out of their garden.

So, how can your readers protect their gardens from bugs?

While organic gardening is a sustainable alternative, gardeners might still want synthetic pesticides for a variety of reasons. The best answer is to use a pesticide specific to the insect rather than a massive application of a powerful toxin. For specific problems that cannot be solved without synthetic chemicals, there are a variety of new "reduced risk" and bio-pesticides. These new pesticides are usually safer for humans and affect only the target pest (and closely related organisms). The EPA is currently in the process of creating a web site with information about these reduced risk pesticides, but it won't be ready until sometime in 2001.

As an example, the EPA suggested alternatives for dealing with termites after the decision to ban Dursban. Their list included some of the "reduced risk" pesticides mixed with some pyrethroids and synthetic pyrethroids. (However, we should note that pyrethroids should not be used near open water due to acute toxicity to shellfish.) The EPA recommended anything from the following list for termites: permethrin, cypermethrin, imidacloprid, fipronil, bifenthrin, esfenvalerate, deltamethrin, cyfluthrin, or bait systems using sulfluramid, hexaflumeron, diflubenzuron, or hydramethylnon.

For non-synthetic and organic alternatives, the Northwest Coalition for Alternatives to Pesticides has created fact sheets of non-chemical alternatives for a variety of different pest problems. These should be your first source when responding to questions about alternatives to Dursban and diazinon. The information is available online at, and there is also a link on our website,

Despite their popularity, Dursban and diazinon have now been determined unsafe for the men, women, children, and infants who come into contact with them. This contradicts the repeated safety assurances over the years from EPA and the pesticide industry. If Dursban and diazinon are unsafe now, then they’ve ALWAYS been unsafe. If the 1996 Food Quality Protection Act (FQPA), the law that ordered the systematic safety evaluation of each pesticide, had been in place in the 1940's when these pesticides were introduced, they never would have been registered.

Dursban and diazinon belong to the family of insecticides known as organophosphates (OPs). OPs were derived from World War II chemical warfare and act as neurological toxins on insects, mammals, and even humans. In humans, they inhibit the production of an enzyme, acetyl cholinesterase, which keeps your brain and nervous system functioning smoothly. Minor exposures may lead to headaches, nausea, dizziness, weakness, and drowsiness. More serious exposure can cause comas, seizures, and death. Infants and children are especially at risk to low doses because relatively small doses of OP pesticides can affect nervous system development.

Since OPs work on individual organisms, effective use requires heavy and repeated applications of the insecticide. These repeated broad application techniques lend themselves to excessive human exposure even when following the package directions. For example, in the Preliminary Occupational and Residential Risk Assessment for Diazinon published by the EPA, application of diazinon by a home gardener provided exposures up to 3500 times a "safe" dose (20x for a push spreader, 288x for a spray wand, and 3500x for applying with a paintbrush).

Even though today's agreement will allow diazinon to be manufactured until 2003, we don't think the risks of diazinon to home gardeners, their families and their pets are worth it. We recommend all gardeners stop using products containing the chemical immediately. We hope you will urge your readers to do the same.