Pesticide Exposure and Re-Entry in Agriculture

Abstract

For risk evaluation one needs to know the toxicity of the compound and its uses, since the actual use pattern determines the level of exposure. This is the case for the mixing, loading and application of pesticides, as well as for re-entry exposure, i.e. exposure after application. For the present overview the emphasis is on the various aspects of the exposure of harvesters and other workers in a crop. The level of exposure caused by re-entry is determined by the amount available in the surroundings of the worker, i.e. the amount present in air (still available after application as vapour and/or aerosols, or available by evaporation from crop, soil, objects, or materials present), or brought into the air by the workers activities (e.g. resuspension of deposited residues) and the degree of contact of the worker with contaminated surfaces (mainly the crop itself). The resulting potential exposure, defined as the amount that reaches the worker from the environment by deposition, contact or inhalation, is very important for generic purposes. The potential exposure may be determined by the chemical properties of the pesticide but it is certainly determined by the physical parameters related to the type of crop, physical properties of the pesticide and the nature of the operations of the worker. The major advantage of the concept of potential exposure is given by the fact that the actual clothing of the worker has no influence on the potential exposure. This is, however, also its major disadvantage since for the assessment of systemic uptake of the pesticide through the skin, by inhalation or by swallowing, the actual exposure and the degree of absorption must be known. The actual skin exposure is defined as the amount that reaches the skin and becomes therefore available for absorption through the skin. For inhalation and oral exposure, the potential and actual exposure are (without respiratory protective equipment) generally much more similar than for dermal exposure.