Multiple pesticide applications

Kuehl, D.W., E.N. Leonard, K.J. Welch, and G.D. Veith. 1980. Identification of hazardous organic chemicals in fish from the Ashtabula River, Ohio, and Wabash River, Indiana. Jour. Assoc. Off. Anal. Chem. 63 1238-1244. Kunz, T.H., E.L.P. Anthony, and W.T. Rumage III. 1977. Mortality of little brown bats following multiple pesticide applications. Jour. Wildl. Manage. 41 476-483. 

Since the analytical point of view most of current analytical methods are based on LC-MS/MS, but for some classes of pesticides GC-MS continues being the technique of choice. The use of quadrupole ion trap (QIT) to analyze multiple pesticide residues is limited to several multiclass pesticides in fruit [162], because of the limited number of ions that can be isolated at the same time. For this reason, the use of several time windows is required and this is indeed a strong limitation in practice. The use of hybrid triple quadrupole linear ion trap (QqLlT) mass spectrometer has provided significant contribution to the development of high-sensitive multiresidue analytical methods for pesticide control. An example of application is the method reported by Hernando et al. for the analysis of pesticide residues in olive oil [65]. 

For purposes of screening-level assessments, while multiple applications may exist for a given pesticide, e.g. indoor residential exposures may originate from pesticide applications to ornamental and landscape plantings, typically a worst-case or high-end exposure scenario is selected for the initial assessment. For example, turf grass broadcast application is the use pattern that often serves to provide the worst-case estimates of human contact and exposure for most outdoor uses of a pesticide. 

An individual may have non-dietary exposure from multiple pesticide uses at different times of the year (Figure 8.19). A use may involve one or more chemicals, applicator exposure and post-application exposures on several days. The temporal occurrence of use events, the algorithms for calculating the time-dependent dose given that a use has occurred, and the individual s behavior generate chemical and route-specific dose profiles. These profiles are combined over the different uses to produce the chemical and route-specific dose profiles over time for the non-dietary sources. 

Low-pressure gas chromatography (LPGC) is also used for the fast analysis of multiple pesticide residues, mainly for food applications. The LPGC/ mass spectrometric detection (MSD) technique uses an analytical 0.53 mm internal diameter column and 1 pm thick film coupled to a 0.15 mm inner diameter restriction capillary at the inlet side. While the injection conditions are similar to conventional GC methods, subatmospheric pressures occur through the column because of the MS vacuum source. 

K. S. Narayanan and R. K. Chaudhuri, ia D. G. Chasia and L. E. Bode, eds., Fmulsifiahle Concentrate Formulationsfor Multiple Mctive Ingredients, Pesticide Formulations and Application Systems, Vol. 11 ASTM STP 1112, American Society of Testing and Materials, Philadelphia, Pa., 1990. 

Pesticide residues consist of chemicals that might occur in a commodity as a result of application of a pesticide. Such chemicals typically correspond to compounds for which a regulatory agency has or will set a tolerance, i.e., a maximum residue limit, specific to the commodity. In either a field study or a market basket survey, residues to be determined will be those which result from application of the specific pesticide that the study is intended to support. A market basket survey, however, might be intended to support not just one but several different pesticides of the same or different chemical classes. In addition, a market basket survey might include pesticides not used in the USA but for which import tolerances exist. For example, some uses of the parathion family of pesticides on food products have been abandoned in the USA but remain in other countries that export the products to the USA. A market basket survey offers a means to evaluate actual dietary exposures to residues of such pesticides. In addition, tolerance expressions frequently include multiple compounds, all of which must typically be determined in residue field trials. The sponsor of the market basket survey must decide whether to analyze for all compounds in the applicable tolerance expression or to restrict the program to selected analytes, such as the active ingredient. 

Pentagone is an aqueous-based surface decontamination product developed for the cleanup of pentachlorophenols, creosote, petroleum hydrocarbons, chlorinated hydrocarbons, polynuclear aromatic hydrocarbons, and selected pesticide and herbicide spills. It can be used on concrete, asphalt, or metal and is capable of being applied as a foam, allowing treatment of overhead, vertical, and horizontal surfaces. It has been commercially available since 1993 and has been used in multiple applications. 

Microencapsulation can be used to provide a temporary barrier between a chemical species and its surrounding environment see also Section 14.3). This permits controlled (slow) release of the active agents following application. Depending on the product and the situation, an active ingredient such as a pesticide may need to be released slowly at low concentration, or slowly at high concentrations. Such controlled release can both reduce the number of crop applications that are required and also help prevent over use and subsequent run-off. The barrier can be provided by a polymer film, in the case of suspensions [867], or a liquid membrane, in the case of single or multiple emulsions [865], Microemulsions have also been used [234,865],... 

De Zwart (2005) used a novel method to predict the effects of multiple stressors caused by pesticides based on a GIS map of agricultural land use, comprising 51 crops. Through the application of SSDs for aquatic organisms, in combination with rules for mixture-toxicity calculations, the modeled exposure results were transformed to risk estimates for aquatic species. The majority of the predicted risks were caused by pesticides applied to potato cropland, and approximately 95% of the predicted risk was caused by only 7 of the 261 pesticides currently used in The Netherlands. 

Studies for pesticide risk assessment focus on the situation in a water body near the field edge, with the peak of exposure soon after application due to drift, runoff, or drainage. In most cases, endpoints are related to the initial concentration of the test item (which can encompass multiple applications). In contrast to this, the focus of EQS derivation is mostly on protection against effects of long-term exposure. 

Residential risk assessment to pesticides typically involves more than one sonrce and mnitiple pathways and rontes, e.g. a given active ingredient may be nsed for multiple indoor apphcations, and in some cases, for outdoor applications. In some cases, the applications may overlap with respect to timing (calendar days). The potential co-occurrence of applications and potential exposures requires temporal product use information. Such information is rarely available. 

Measurement of the post-application residential exposure is, in many ways, more complicated than the agricultural re-entry since there may be multiple sources and routes of exposure, varying amounts of time spent in contact with these sources and a much wider age and health range in the exposed population (USEPA, 1991, 1999a). Chemicals such as pesticides that are released into or otherwise enter the residential enviromnent tend to partition into various compartments, either through direct dispersion in indoor air or through adsorption onto surfaces that serve as sinks from which material can subsequently be released into the air (Ross et al., 1990, 1991). A detailed discussion of the measurement of pesticides in the residential enviromnent is presented in Chapter 3. 

There is a correlation between content of carcinogens in various links of biogeochemical food webs and frequency of stomach cancer. The most significant correlation was monitored in agrogenic biogeochemical nitrate province of the Kzyl-Orda administrative region. The multiple increase in the application of different agrochemicals, such as fertilizers, pesticides, and defoliants, induced the development of... 

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