by Professor J.J. McLean
Risk is defined as the probability that a particular adverse event may occur during a specified period of time. In this discussion the adverse event is a deleterious effect on the health of consumers and the time period is a lifetime of consumption of treated produce.
Regulatory authorities take very seriously the matter of risk associated with consumption of agriculture produce since consumers usually do not have control over the intake of chemicals in food because they do not know what compounds are present or their concentration. Therefore consumers cannot weigh risk against benefit.
It is an interesting exercise to examine the public perception of risk. The results of a survey by Upton (1982) who examined the perception of risk associated with activities causing death. It shows that two groups, the League of Women Voters and college students perceived that pesticides were ranked in the top ten causes of death and the business and professional club members also believed pesticides were of significant risk at number 15. Actual rating of pesticides was 28 in the top 30 events causing death. Actual death rate is zero.
Pesticides are often claimed to be associated with birth defects and other adverse effects on pregnancy. While it is acknowledged that there may be unexplained clusters of birth defect in certain geographic localities, the medical and other health care professionals are generally unaware of the true incidence of adverse pregnancy outcomes in humans.
Pesticides are often viewed as unfavorable agents by the general public. This situation is made worse when allegations of risk or hazards associated with pesticide use are published, while efforts to refute such allegations are largely ignored.
The situation is further exacerbated by statements such as “the chronic symptoms of organophosphate poisoning are sore throat, runny nose, tremor, aches and pains in the limbs and stomach upsets” (Bartle 1991). This list of general symptoms is similar to those frequently associated with a number or natural infections in humans and require the qualification that adequate laboratory identification of the pesticide in body fluids is required. Modern analytical techniques are now capable of positively identifying minute traces of pesticides.
The normal diet contains a large number of naturally occurring pesticides that are produced by plants to defend themselves against attach by insects, fungi and predators, including humans. When plants are damaged, they may respond by increasing the levels of pesticides in their tissues. It has been estimated that the intake of man made pesticides is only 0.1 mg/day, while the levels of naturally occurring pesticides are 15,000 times higher at 1500 mg/day. Fifty two of these naturally occurring pesticides have been tested for carcinogenicity in at least one rodent species and 52% were positive. When the mold toxins were tested at high doses in rodents, 11/16 were carcinogenic (Ames and Gold 1990). Humans have been consuming these plant pesticides for centuries and fortunately have adapted to dealing with low doses without ill effects.
The preceding paper was written by Professor J.J. McLean, Faculty of Applied Science, Swinburne University of Technology. It examines the assessment of agricultural chemicals and whether residues are associated with any risk to consumers of agricultural products.
Reprint permission given by AgAir Update, P.O. Box 850, Perry, GA 31069 - an international agricultural aviation publication.
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