Environmental behavior, spray

The bulk of this paper will be concerned with the prospects of Ji-nitroso compound formation in the environment, and with environmental behaviors of selected nitroso compounds, as best we can describe or predict them from experimental work completed thus far. Obviously, once in the environment, a compound will to a large extent be subject to the same conditions whether it was formed there or introduced as a pesticide contaminant, and in this manuscript no attempt to differentiate between the two modes of introduction has been made. Such distinctions could, however, influence the location of a compound in the environment—say on a plant or soil surface if sprayed with a pesticide, admixed with soil if transported by leaching, etc., and some of the experiments cited will have been conceived with one or the other of the introduction modes in mind. 

It is important for the public to recognize that there is no fixed distance or buffer zone for a safe distance to provide protection from spray drift. This will be a function of the pesticide being used, its toxicity and environmental behavior such as bioaccumulation, the nature and sensitivity of the downwind sites, and the nature of the application method, meteorological conditions, and so on. 

The interpretation of the effects of such drift, particularly its potential for adverse effects on human health, is dependent on some of the parameters of environmental behavior shown on Table VIII. The dose is given at 2 lbs/acre and translated into a deposit level of 20 mg/square foot, which is more useful in the interpretation of exposure data. The figures given for the deposit amount from spray drift at 100 yards and 1/2 mile are the figures for drift from a coarse spray on flat land for small target areas and are average drift amounts. The figure of 20 mg/kg is the NOEL for 2,4-D. 

The effect of formulation and spray adjuvants on insecticide efficacy has received considerable attention from the pesticide industry. However, few detailed mechanistic studies on the role these additives play in environmental fate processes have appeared in the open literature. Application of laboratory-derived process information to field scenarios is hindered by the fact that most laboratory investigations have used technically pure (unformulated) organophosphorus insecticides. Including the effects of formulation ingredients on such processes as volatilization and sorption to soil solids would allow laboratory studies to better predict the environmental behavior of these compounds. 

Currently, the active ingredients and adjuvants of the products used for crop protection in agriculture are nonrenewable (generally of petrochemical origin) and present industrial and environmental risks [79]. The role of surfactants in modifying pesticide behavior has been reviewed on a number of occasions over the past 25 years [References in Ref. 80]. Many published reports have shown that the incorporation of surfactants into pesticide sprays improved efficacy [80]. Since most surfactants used in pesticide formulations are petroleum based, it is conceivable that the growing propensity toward products that are environmentally friendly will work in favor of PBS as potential replacements. 

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