Applications field, monitoring exposure

Issue The mineral processing industry and the end-users of their products need to agree on (1) realistic exposure scenario(s) (2) valid emission models (3) field monitoring methods for the application, use and disposal of biocidal products. 

Virtually all the research on herbicides In forest streams shows that the residue levels reach a maximum shortly after application and then decline rapidly. Although the Instantaneous maximum concentration may be 0.037 mg/liter, the concentration 1 hour later may be 0.010 mg/liter, 0.002 mg/liter at 24 hours, and below the detectable level after 48 hours. The problem Is to evaluate this type of dynamic exposure in terms of the type of Information that Is available from traditional testing (2). The approach often taken Is to assume that the maximum concentration defined In field monitoring was present for a full 48 or 96 hours, and to estimate toxic effects based on 48- or 96-hour toxicity tests. The consequence in almost... 

One essentially unexplored area for hair analysis is its application to the investigation of environmental toxin exposure. We received a research grant during 1979 from the National Institute of Occupational Safety and Health to explore the possibility of using hair analysis for monitoring exposure to polychlorinated biphenyl compounds (PCBs). Although the analytical chemical problems of this project were successfully solved, we were unable to mount successful field studies with human subjects. 

Table I. Pesticides Used in 102 Different Applications to Farm Fields in California During Which Exposure of Workers Involved in the Applications Were Monitored...

When a tracer is considered, it is important to evaluate its performance with respect to these criteria, especially stability during exposure and storage/analysis. Normal practice involves conducting weathering tests where field collectors are treated with known amounts of the tracer and an assessment is made of weathering, extraction and storage stability under conditions pertaining to the intended use. The characteristics of the tracer allow it to be applied uniformly over the application area. Typically, application monitors are used to verify both the application rate and the uniformity of the application. 

Bystanders. The bystander had the lowest exposure to carbaryl of all the workers monitored. In keeping the bystander within 100 feet and downwind of the ground applicator, the bystander often had to walk into the field while it was being treated. This practice resulted in exposure when the hands of the bystander touched the crop foliage. Thus, with peas, there was no exposure because the plants were too small at the time of spraying for any inadvertent contact, but with relatively mature potatoes, measurable residues were deposited on the bystander. For example, when 80S was applied to this crop, the bystander had a total HDE of 0.5 mg/h... 

Occupational pesticide exposure holds a peculiar status within the field of occupational health and safety, both from a scientific and regulatory perspective. Methods for personal monitoring of dermal exposure first arose in the context of pesticide applications in agriculture, pioneered by scientists in the USA Public Health Service (Batchelor and Walker, 1954 Durham and Wolfe, 1962). These methods gained worldwide recognition in the early 1960s, and remain a component of exposure assessment practice today. This work pre-dated most personal monitoring methods that were developed for industrial workplaces. 

For risk-assessment purposes, the best choice is a field study which is carried out for the specific purpose of obtaining exposure values under representative conditions for the use scenario and active substance that are being considered. In view of the possible range of exposure due to the large number of potential variables, it is absolutely required that the study include between about 10 and 30 replicates spread over a reasonable time period accounting for variation in climatic conditions and the relevant application technique. The number of replicates per person should be as small as reasonably possible. Workers should be monitored during whole work shifts while using the relevant and/or required personal protection... 

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