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Organophosphate pesticides are being tested on students

Richard Harling, BMJ

The Inveresk research laboratory near Edinburgh has recruited students and unemployed men to take doses of azinphos-methyl, a potent organophosphate pesticide, in order to determine the dose at which side effects are observed. Two other organophosphate pesticides, aldicarb and dichlorvos, have already been tested on students at Inveresk and at Manchester University.

Organophosphates are highly toxic chemicals. Their best recognised effects are due to phosphorylation and inhibition of acetylcholine esterase, which has an impact on cholinergic transmission throughout the nervous system. Symptoms of acute toxicity relate to musculo-skeletal, central, and autonomic effects and include paralysis, confusion, headache, nausea, sweating, and blurred vision.

The long term effects of organophosphates are unpredictable. Being lipophilic, they tend to accumulate in fatty tissue, from which they are gradually released. According to Dr Goranji Jamal, consultant neurologist and senior lecturer at the University of Glasgow, experiments on animals have revealed that organophosphates can inhibit or destroy a whole range of enzymes. Chronic symptoms including memory loss, fatigue, and sensorimotor polyneuropathy have been described. Organophosphates are one of the agents implicated as a cause of the symptoms experienced by those who took part in the Gulf war.

Pesticide regulations in the United States dictate that the safe concentration of a chemical is 10 times lower than the level established by animal testing. This gives chemical companies a huge financial incentive to test pesticides directly on humans to try to establish higher acceptable concentrations, although legislation prevents testing of organophosphates on humans in the United States.

The Environmental Protection Agency, the organisation responsible for licensing pesticides, is concerned that they are being tested on humans in the United Kingdom and has asked to see more details of the experimental protocols involved.

Paul Tyler, chairman of the all party Commons and Lords organophosphate group, is worried that vulnerable people may be induced by financial incentives to take part in the experiments: "Multinational companies are paying substantial sums to students to use them as human guinea pigs for testing dangerous organophosphate pesticides."

He is concerned that the experiments are not regulated by any government department. Individual companies are responsible for ensuring that their research conforms to ethical guidelines. Guidance issued in 1986 by the Royal College of Physicians states: "A risk greater than minimal is not acceptable in a healthy volunteer study." The Inveresk laboratory declined to comment on the organophosphate experiments but emphasised that all trials are reviewed by an ethics committee and are conducted under medical supervision.
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Rapid Responses:

Read all Rapid Responses

Ethical??

Ed Walker
bmj.com, 18 Aug 1998 [Full text]

Organophosphates irrelevant to Gulf War Syndrome

Eric Croddy
bmj.com, 18 Aug 1998 [Full text]

What happened to medical ethics?

Susan Boone
bmj.com, 18 Aug 1998 [Full text]

Aldicarb is not an organophosphate pesticide

Stephen L Werner
bmj.com, 18 Aug 1998 [Full text]

Aldicarb is a carbamate that may be fatal

Mohy K El Masry
bmj.com, 21 Oct 2006 [Full text]