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For decades, U.S. and foreign pesticide manufacturers have been feeding their products to rats, rabbits, mice, and guinea pigs in thousands of controlled laboratory studies, all designed to satisfy government regulatory requirements for chemicals that kill weeds, insects, rodents and other pests.
Studies on lab animals are still routinely conducted for pesticides today. But in recent years, in a growing number of experiments that are raising ethical, legal and scientific questions inside and outside government, the test animals are people.
And for reasons neither U.S. nor British environmental officials can explain, most of the recent human pesticide experiments are being performed in England and Scotland.
In three related studies conducted just last year for Amvac Chemical Corporation, headquartered in City of Commerce, California, for example, researchers at the Medeval Laboratories in Manchester, England dissolved a neurotoxic insecticide, dichlorvos, in corn oil and paid a small number of adult men to eat it in a test of the chemical’s acute effects. Dichlorvos is used to kill flies, caterpillars, and other bugs on fruit and vegetable crops, and has long been used in pet collars and pest strips under such trade names as “Fly-Die” and “No- Pest.” The volunteers in the experiment consumed an insecticide that, outside the United States, has been marketed as “Doom.”
In another study with human volunteers, commissioned by French chemical giant Rhone-Poulenc and conducted in 1992 on 38 men and 9 women at the Inveresk Clinical Laboratory in Scotland, “subjects were given a light breakfast on the day of the study, including a drink of orange juice” containing a placebo or various doses of aldicarb, an extremely toxic insecticide. According to U.S. government documents, one man experienced “diffuse and profuse” sweating that continued for four hours. Another subject became light-headed, and three reported headaches.
In both the Medeval and Inveresk studies, researchers did observe the biological effect of regulatory concern: varying degrees of depressed levels of an enzyme, cholinesterase, in the people who ate the insecticides. Cholinesterase plays a crucial role in the transfer of signals across nerve cells in insect and human nervous systems. It is this effect that the U.S. Environmental Protection Agency measures in setting the safe levels to which humans can be exposed to aldicarb, dichlorvos and other neurotoxic pesticides in food, bug sprays, or other sources. According to EPA, a 1981 dichlorvos feeding trial on humans, using much higher doses of the chemical, had to be terminated prematurely when some subjects’ cholinesterase levels dropped by 80 percent (see Sidebar: A 1981 Dichlorvos Study on Humans).
The EPA documents indicate that, according to the industry submissions, any pain or discomfort experienced during the recent studies by the people who participated was temporary. In one of the Amvac studies, the EPA review noted that “one study subject reported some drowsiness, and one reported a slight headache, none of which were attributed to administration of the chemical, though no reasons were given to support these judgments.”
However, the EPA’s summaries do not provide the basis for determining whether ethical guidelines were, in fact, complied with. For example, they do not provide detail about what the research subjects were told about the experiments and how much they were paid to participate.
Above and beyond the particulars of these three studies, ethical questions arise for multiple reasons. First, EPA does not routinely require companies who conduct human experiments to support pesticide applications to follow any ethical protocol. Second, while medical researchers, officials, and bioethicists have spent many years grappling with the ethical problems posed where humans are subjected to hazardous substances in hopes of potential future medical benefits, there has been much less consideration of ethical problems where humans are subjected to toxic insecticides without prospect of future medical benefit, but in a presumption of general social benefit. Third, recent government reviews have shown that even in the United States — where government-sponsored human experimentation has been subject to regulation for many years — serious deficiencies remain in the administration of ethical requirements
Thus, even where, as in the case of the three Amvac studies, ethical rules are said to have been followed, there can be no assurance that this was the case absent some auditing process. No such process is in place at EPA.
Neither the EPA nor pesticide regulators in the United Kingdom require human experiments as part of pesticide assessments. But the EPA has accepted a number of them from chemical companies and used them for regulatory purposes, particularly studies that measure effects that are short-term and reversible. In fact, EPA has developed no formal policy on the use of humans in scientific experiments, including pesticide feeding studies on humans. The agency is in the process of developing guidelines on how such studies should be conducted to protect human subjects.
In the meantime, EPA pesticide regulators say that, if they are asked beforehand, they informally discourage companies on ethical and scientific grounds from conducting human experiments like the ones performed for aldicarb and dichlorvos. In particular, the agency refuses to review in advance any protocols for human experiments out of concern that the mere act of reviewing might actually encourage more such studies.
Nevertheless, several pesticide companies have already benefited tangibly in the U.S. regulatory process from being able to operate in the absence of agency rules.
View and download the full report here: English Patient
