The Facts About Diazinon

Why is diazinon dangerous?

December 5, 2000

The Facts About Diazinon: 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.”