The Facts About Diazinon

Why is diazinon dangerous?

Diazinon is one of a class of pesticides called organophosphates (OPs), chemicals that were originally developed by the German company I.G. Farben as nerve gases during World World II. Even short-term exposure to diazinon and other OPs can damage the brain and nervous system. Symptoms can range from headaches, nausea, dizziness, and seizures to paralysis, multiple chemical sensitivity syndrome, comas, and death in extreme cases. Pesticide industry studies conducted on laboratory animals show that children are more susceptible to diazinon than are adults. After reviewing thousands of scientific studies--most of which were generated by the pesticide industry--the EPA concluded in June 2000 that all common household uses of diazinon are unsafe.

Fact Sheet

This fact sheet presents data culled from EPA’s draft risk assessment for diazinon. The risk estimates will change as the manufacturer submits new studies; however, it is highly unlikely that the EPA will find the risks from these uses acceptable.

Primary Manufacturer

Syngenta (formerly Novartis, a Swiss Pesticide and Pharmaceutical firm)
With production in Macintosh, AL

Other Manufacturers


First Marketed

1948 (according to EPA Pesticide Products Information System)

Pounds Used Per Year

6 million pounds (tied with Dursban for home and garden use)

Primary Usage

  • Outdoor application by homeowners (39%)
  • Lawn care operators (19%)
  • Exterminators (11%)
  • Flea & Tick Collars

Consumer Product Names

Spectracide, Real-Kill, Ortho, Cutter, Peters, Hot Shots, No-Pest, K-Rid and others

Largest Food Uses

  • Almonds (170,000 lbs.)
  • Prunes (66,000 lbs.)
  • Peaches (61,000 lbs.)
  • Pecans (85,000 lbs.)
  • Plums (64,000 lbs.)
  • Sweet Corn, Fresh (48,000 lbs.)

Closely followed by Head Lettuce, Stone Fruits and Berries

Indoor Use is Deemed Unsafe for Small Children

Novartis (now Syngenta) announced on July 24, 2000 that it would no longer support diazinon’s indoor uses including greenhouse application. The company cites lack of funds for the required testing, but EWG suspects that Novartis has given up hope in light of the EPA assessment.

EPA's Risk Assessment shows that children are exposed to diazinon at up to 400 times the EPA's safe dose 24 hours after professional treatment in cracks and crevices.

Exposure Route


(times EPA's 'safe' dose)


(times EPA's 'safe' dose)

Inhalation Exposure 24 Hours After Treatment



Dermal Exposure 24 Hours After Treatment



(*) EPA provided a number of different dermal scenarios. This represents the lowest risk.

Source: USEPA Preliminary Occupational and Residential Risk Assessment for Diazinon (PORRAD)

Diazinon can Pollute Surface and Ground Water

Diazinon is the most frequently detected insecticide in US Geologic Survey’s National Ambient Water Quality Assessment (NAWQA) program. It is found in 24 states plus the District of Columbia, including every major river basin. Diazinon has been found in drinking water wells at levels exceeding EPA’s ‘safe’ level. Diazinon could contribute to unsafe drinking water exposures for children.

Diazinon Poses a Risk to Pacific Salmon

Runoff of diazinon has reached unsafe levels in Northwest watersheds creating a threat to salmon populations. Diazinon interferes with juvenile Chinook salmon’s ability to detect alarm chemicals in the water leaving them vulnerable to predator attacks. Since diazinon is a broad spectrum insecticide, it also impacts the insects and other animals on which the young salmon feed. The dose of diazinon inhibits reproductive behaviors and may also cause genetic damage in fish. The EPA has come under a lawsuit for failing to develop a plan to safeguard salmon from pesticides under the Endangered Species Act.

Source: Cox, C., 2000, Lethal Lawns: Diazinon Use Threatens Salmon Survival, J. Pesticide Reform.

ALL Uses are Currently Deemed Unsafe for the Home Applicator

Application Method

Exceeds EPA’s ‘Safe’ Dose by a factor of

Lawn Granules Applied with Push Spreader


Lawn Granules Applied with ‘Belly Grinder’


Lawn Application with Garden Hose Sprayer


Typical Garden Application with Spray Wand


Typical Garden Application with Paint Brush


Note: Table does not list all uses. Estimates include both dermal and inhalation risk


Diazinon Victims

Source: EPA Review of Diazinon Incident Reports, 1998

Two female gardeners in Singapore knocked over a container of diazinon. After cleaning up the spill, one of the women experienced diarrhea, dizziness, frothing at the mouth, and pulmonary edema requiring a respirator. She later developed acute pancreatitis.

An 18 month old boy in Michigan was accidentally fed "roach milk" (5% diazinon). The boy was taken to the hospital in a coma. He recovered with treatment. (Detroit News, November 29, 1985)

A six-year-old girl had her hair washed for head lice with diazinon. She was hospitalized after full cardiac and respiratory arrest.

Diazinon has been cited in more than 200 lawsuits involving acute poisonings, chronic conditions and at least one death.

Symptoms of Exposure to Diazinon

Exposure to diazinon can result in headaches, diarrhea, or comas depending on the level of exposure. Below is a list of common signs and symptoms of exposure.

Common early or mild signs/symptoms

Present in the moderate or severe poisoning

Presence signifying life-threatening severity

Muscle weakness

Tightness in chest
Difficult breathing
Abdominal pain
Memory loss
Poor concentration
Heavy salivation
Profuse sweating
Blurred vision
Pinpoint pupils

Respiratory arrest
Pulmonary edema
Loss of reflexes
Flaccid paralysis

Source: Review of Diazinon Incident Reports, USEPA Memo, July 1998

Regulatory History


Product first marketed in the US.


Product reviewed by the EPA under the "Special Review" process. Golf course and sod farm uses were cancelled due to high risk for birds feeding on these properties. Home lawn use, however, is maintained. The decision also prohibited application on food crops grown in greenhouses. (51 FR 35034 amended in 52 FR 5656)


Registrant-requested hearing confirmed 1986 decision.


Decision finalized to cancel all use on golf courses and sod farms.


Diazinon has come under FQPA review, which will assess impact on humans, not just birds.

 Syngenta's Human Testing

Syngenta (Novartis) Doses Humans with Diazinon in an Effort to Save the Pesticide

Earlier this year, Syngenta (at that time Novartis) fed diazinon to humans in a last ditch attempt to save home and garden uses of the chemical. Human studies have been on the increase as companies have sought to avoid the extra public health protections required by the Food Quality Protection Act. In particular, pesticide companies have sought to eliminate the ten fold layer of protection that is applied to safety standards that are based on animal trials, as a way of minimizing the regulatory effect of the extra protections that the law now requires for children.

The Syngenta studies are in direct violation of EPA’s policy on human studies, under which the EPA does not accept human studies for the determination of a chemicals’ “no effect level.” A no effect level is the stepping stone from which the agency determines a safe exposure dose. The reason that EPA does not accept this type of human study is clear: in order to determine the dose that produces no effect, test animals, in this case humans, must be exposed to doses of the pesticide that cause toxic effects. This is a particularly unsavory prospect given the neurotoxic properties of diazinon.

It is unlikely that Syngenta was not aware of EPA’s policy at the time the studies were conducted. Human testing has been a very high profile issue at the EPA since 1998, when Administrator Carol Browner ordered an independent review of the agency’s human testing policy. Documents submitted to the EPA by Syngenta reveal that the company has conducted at least direct oral dosing studies of diazinon toxicity in human “volunteers” in the past two years.

References to the studies are contained in a Syngenta (Novartis) document innocuously entitled, “An Assessment of the Dermal Absorption of Diazinon and A Rebuttal to EPA’s Use of the Default Dermal Absorption Value of 100%.” The studies themselves, Novartis Studies No. 587-98, and 615-98, which are cited in the references, reveal the clear purpose of the work. Boysen, M.G. (2000), for example, is entitled: "A randomized double-blind ascending, acute, oral dose study of diazinon to determine the no effect level (NOEL) for plasma and RBC cholinesterase activity in normal healthy volunteers.”

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.

Letter to Retailers

EWG Asks Retailers to Stop Selling Diazinon Immediately

December 5, 2000

Dear Retailers,

Today the Environmental Protection Agency (EPA) released its final risk assessment of the insecticide diazinon, a heavily used home and garden pesticide contained in hundreds of products sold under the brand names Ortho, Spectracide, Real Kill and others. EPA's massive review of thousands of scientific studies concluded that diazinon poses health risks far greater than Agency guidelines allow. That conclusion compelled the manufacturers and the EPA to agree on a phase out of all home and garden products containing diazinon. Manufacture of products for indoor use will cease in 2001. However, today’s action allows continued manufacture of lawn and garden products containing diazinon for up to three years, with no time limit on the continued sale of existing stocks. The continued sale of products that are known to be unsafe is completely unacceptable. We ask you to cease the sale of diazinon products immediately.

Last summer, the EPA published a draft risk assessment for diazinon which concluded that virtually all home uses of diazinon, including lawn and garden products, are unsafe by wide margins, even when used according to the label directions. This prompted the primary manufacturer, Novartis (now known as Syngenta), to halt efforts to defend the safety of all indoor uses of diazinon and to voluntarily withdraw these uses of the product from the market. The announcement today builds on that decision, but unfortunately allows the continued manufacture and sale of outdoor use products containing diazinon for at least the next three years. Diazinon is also a threat to Pacific salmon and is the pesticide found most often in surface waters in the United States, primarily due to its heavy use on lawns, where it washes into streams following rains.

As with last summer’s decision to ban another highly toxic home use pesticide, chlorpyrifos (Dursban), retailers and their customers are left holding the bag. The government and the main manufacturers of diazinon have concluded that virtually all home and garden use diazinon products on the market today are unsafe, but failed to follow through with meaningful actions to protect the public and the environment from the pesticide.

We feel that consumers will certainly purchase safer products if they are educated about the hazards of diazinon. With that in mind, we respectfully request that you take the following actions:

  1. Demonstrate your environmental and public health leadership by immediately removing products that contain diazinon from your store shelves.
  2. While your existing inventories are being removed, post highly visible signs in your lawn and garden department, advising consumers of the EPA decision.

We look forward to your speedy response to this issue. If you have any questions, please contact me, Sean Gray or Richard Wiles at EWG’s office (202) 667-6982.


Kenneth A. Cook

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