Sunlight photodegradation is one of the most destructive pathways for pesticides after their release into the environment. Plant surfaces, especially leaf surfaces, are the first reaction environment for a pesticide molecule after application, and spray drift would indirectly present a similar situation. Photolysis on soil surfaces becomes important when a pesticide is directly applied to soil or not significantly intercepted by plants, providing that the leaf cover does not shade the ground from sunlight. Because the foliar interception of pesticides depends on plant species and usually increases with their growth stage (Linders et al. 2000), the importance of soil photolysis is considered to be lessened when plants become mature. Spray drift after pesticide application or washoff from plants by rain is the indirect route by which a pesticide reaches the soil.

https://bilder.buecher.de/zusatz/14/14812/14812358_lese_1.pdf?origin=publication_detail

Photodegradation of Pesticides on Plant and Soil Surfaces

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Pesticide Use and Toxicology in Relation to Wildlife: Organophosphorus and Carbamate , Compounds

Many polynuclear aromatic hydrocarbons (PAH) are known to be carcinogenic to animals and probably to man. This review is concerned with carcinogenic and non-carcinogenic PAH in the water environment, with emphasis on 3,4-benzpyrene (BP) because it is ubiquitous, is one of the most potent of the carcinogenic PAH and has been widely studied. Although PAH are formed in combustion and other high-temperature processes, there is also evidence for their endogenous formation in plants, which may explain their ubiquity therein. Although the solubility of these compounds in pure water is very low, they may be solubilized by such materials as detergents, or they may otherwise occur in aqueous solution associated with or adsorbed on to a variety of colloidal materials or biota, and thereby be transported through the water environment. A notable characteristic of PAH is their sensitivity to light.PAH have been found in industrial and municipal waste effluents, and occur in soils, ground waters and surface waters, and their sediments and biota. With the exception of filtration or sorption by activated carbon, conventional water treatment processes do not efficiently remove them, and they have been found in domestic water supplies. Because of the ubiquity of PAH in the environment, it is impossible to prevent completely man's exposure to them; nevertheless their surveillance should be continued and their concentrations in the environment should be reduced where practicable.

Polynuclear aromatic hydrocarbons in the water environment

Residue contents of DDVP (Dichlorvos) and diazinon applied on cucumbers grown in greenhouses and their reduction by duration of a pre-harvest interval and post-harvest culinary applications

The hazard to fieldworkers from the residues of organophosphate pesticides is a classic occupational health issue. Traditionally, the historical development of such issues has three phases or concerns, viz., recognition, evaluation, and control. In an ideal occupational health program, these three phases are cyclic and repetitive in that occupational health problems are typically first recognized by an unusual pattern of morbidity or mortality within an occupational group; the working environment is then evaluated via such samples and measurements as may be available and appropriate to identify and quantify the levels of exposure; control strategies and technologies are then brought into play to reduce these exposures; and in the ideal case, this process is repeated by follow-up biological and environmental monitoring to ensure that the controls are efficacious and sufficient. In the broad history of occupational diseases, these phases have typically spanned many years and rarely if ever have they progressed in a cohesive sequence or from a well-developed plan (Hunter 1978).

Regulating OP pesticide residues for farmworker protection

Prior to about 1945 it was not realized that spray and dust deposits of most organic insecticidal1 chemicals penetrated, in the field, into subsurface regions of sprayed citrus fruits, even though they were generally nonsystemic in action, as with some of the DN compounds and rotenone. Also, emphasis on “residues” (deposits) prior to this same time was on correlations with pest-control efficacy rather than on safe consumption of the treated commodity, so that initial deposits and aged deposits were most often obtained as weight of insecticide per unit areas of leaf (foliage) tissue2 rather than on and in mature fruits, as with sulfur, lime-sulfur, and lead arsenate, because insect populations were usually evaluated on leaves or twigs rather than on fruits. In connection with the field performance of DDT and other new insecticides against insects and mites in citriculture, however, it was realized shortly after 1940 that the slow disappearance or attenuation from leaves of these (DDT) surface deposits and effective residues from organic pesticides signified at least partial penetration into subsurface tissues (Gunther 1946 and Gunther et al. 1946).

Insecticide residues in California citrus fruits and products.

Chemical carcinogens as a world-wide health problem are receiving increasing attention. On the one hand, the contamination of air and water by a variety of industrial and other chemicals of this type is occurring while, on the other hand, more and more direct food-additive and plant-protection chemicals are in increasingly regulated use. Publicity accorded the fact that certain chemical carcinogens occur in tobacco smoke is a well-known example of the interest in this area.

Occurrence, isolation, and identification of polynuclear hydrocarbons as residues.

Parathion sorbed to dust can persist as dislodgable residues on citrus leaves. Semi-logarithmic plots of parathion dislodgable residue data were initially linear for the 6 soils studied and then a distinct change to lower rates occurred with 5 of the soils. As initial rates and the residue level at the rate change are dependent on the soil, foliar dust is implicated as a causative factor in the non-uniformity of residue dissipation rates.

Worker environment research. IV. The effect of dust derived from several soil types on the dissipation of parathion and paraoxon dislodgable residues on citrus foliage.

The field of pesticide1 residue analyses has seen tremendous advances in recent years. The application of new as well as elsewhere-established analytical techniques and instrumentation to this field of research has been the main contributing factor to these advances. For example, the adaptation in 1961 of gas-liquid chromatography (glc) to the analysis of pesticide residues and their alteration products has given the trained residue chemist a superlative tool for his work, when properly used and interpreted. Other more definitive residue-analytical and confirmatory techniques have exploited infrared, ultraviolet, and fluorescence spectrometry, mass spectroscopy, micropolarography, atomic absorption spectroscopy, carbon skeletonization glc, etc. The importance of colorimetry, thin-layer chromatography (TLC), cholinesterase (ChE) assay, and other separating and determinative techniques should not be overlooked as valuable components of definitive apid credible pesticide residue programs.

Pesticide stability in cold-stored plant parts, soils, and dairy products, and in cold-stored extractives solutions.

In the United States, with probably the most intense and diversified agriculture in the world, there are registered for permitted use more than 900 chemical compounds1 in more than 60,000 pesticidal formulations (Freeman 1965). In this country uses of these materials on more than 2,500 crop items (Kirk 1964) and other foodstuffs are regulated by joint considerations of the U. S. Food and Drug Administration (F.D.A.) and the U.S. Department of Agriculture (U.S.D.A.) (Harris and Cummings 1964), with assignments of tolerances or permitted residue values for amounts of particular chemicals to be legally acceptable on and in particular raw agricultural commodities at time of sale or consumption. These values may range from an actual zero to more than 100 parts per million (p.p.m.), depending in large measure upon the pharmacology and toxicology of the candidate chemical. Until recently and in broadest terms “zero” as interpreted by regulatory agencies could mean either numerical tolerance denied, because of probable hazard to be associated with the projected use, or a number less than unity predicated upon residue analytical capabilities and credulity at the moment. For certain pesticide chemicals which were of widespread application on certain major crops or products, and which were also of pharmacological concern, as residue analytical methodology improved in minimum detectability, and in reliability, some “zero” and other tolerance values have been lowered with certain commodities (e.g., milk) to accommodate a new analytical capability; present tolerances often reflect residues that could remain at harvest. This completely unsatisfactory dynamic tolerance situation has existed particularly with several of those pesticides which contain organically bound halogens, such as dieldrin, endrin, and heptachlor. It has also been involved both legally and morally with numerous chemicals previously registered by the U.S.D.A., and with F.D.A. concurrence, on a “no-residue” basis (Harris and Cummings 1964): at the time the “no-residue” registration was granted finite residues were not demonstrable yet subsequendly analytical detection of persisting residues was made possible by improvements in methodology, usually through exploitation of modern analytical instrumentation, and the original specific registration was revoked.

F. A. Gunther

Papers

Insecticide residues in California citrus fruits and products.

Occurrence, isolation, and identification of polynuclear hydrocarbons as residues.

Worker environment research. IV. The effect of dust derived from several soil types on the dissipation of parathion and paraoxon dislodgable residues on citrus foliage.

Pesticide stability in cold-stored plant parts, soils, and dairy products, and in cold-stored extractives solutions.

Automated pesticide residue analysis and screening.