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The Future Role of Pesticides in US Agriculture
taller than the applicator. Gardeners and nursery workers are likely to be exposured in enclosed environments. Exposures from broadcast or rotomisting can be relatively low or very high depending on the wind direction and strength in relation to the path taken by the applicator (Ecobichon 1996).
The exposure scenarios are only part of the assessment of the likely risk posed by pesticides. It is also important to know the extent to which specific pesticides are absorbed into the body and to know the quantitative and qualitative toxicity of the absorbed doses. The major routes of absorption of pesticides are inhalation, ingestion, and dermal absorption. For the applicator, all three routes can be important. The characteristics of the pesticide are also important. Most pesticides are readily absorbed when inhaled or ingested, and are also absorbed through intact skin. The rate of dermal absorption is influenced by molecular weight and by lipid solubility (Feldman and Maibach 1974, Moody et al. 1990). The problem is made more complex by the variance in permeability of the skin in different regions of the body. It is possible to absorb lethal doses of some organophosphate insecticides while walking through a freshly sprayed field, so intervals after spraying during which reentry into the field is not permitted have been established.
In many cases, incidents of acute poisoning are due to failures to observe safety regulations. In one conspicuous case, in California in 1989, workers harvesting cauliflower in a field sprayed 20 hours earlier with two organophosphate insecticides and one carbamate insecticide became ill after about 1 hour of exposure; at the time, state laws specified a 72-hour safety reentry interval (Ferrer and Cabral 1995). However, occupational exposures can occur even when safety regulations are enforced. In a review of pesticide poisonings of lawn-care and tree-service applicators reported to the New York State Pesticide Poisoning Registry in a 32-month period in 1990–1993, Gadon (1996) identified 28 unambiguous cases; 22 of the 27 people on whom information was available had been using protective equipment when the exposure occurred.
Residues in packaging materials can also be a source of substantial exposure and toxicity. One notable example involved a sack that had contained parathion. The sack was used to build a swing, and the percutaneous absorption was sufficient to kill two of five children using the swing (Hayes 1963).
Trends in Worker Safety Risk
The reporting of cases of poisoning due to pesticides is inconsistent by region, by circumstance, and over time. Nevertheless, trends begin to emerge at coarser scales of observation, especially when one concentrates