Particle-associated pesticides

Camann, D.E., H.J. Harding and R.G. Lewis (1990). Trapping of particle-associated pesticides in indoor air by polyurethane foam and exploration of soil track-in as a pesticide source, in Indoor Air 90, Vol. 2, D.S. WaUdnshaw (Ed.), Canada Mortgage and Housing Corporation, Ottawa, ON, Canada, pp. 621-626. 

A novel device was designed to estimate the dislodgeability of dust-associated pesticide residues by skin contact (Edwards and Lioy, 1999). Called the EL Sampler , the device consists of a spring-loaded assembly that permits the sampling medium to be pressed lightly (12g/cm or 1160 Pa) onto the surface to be monitored. A 10-cm x 15-cm Empore C-18 extraction membrane was used for the sampling medium. The material was chosen after controlled experiments on particle adhesion showed it to pick up the same distribution of test dust particle sizes as the human hand. In studies in which the EL sampler was pressed onto polyethylene surfaces coated with house dust and then sprayed with a solution of pesticides in 2-propanol, the device was found to collect 35%, 31 %, 32% and 18 %, respectively, of chlorpyrifos, diazinon (0,0-diethyl 0-[6-methyl-2-(l-methylethyl)-4-pyrimidinyl] phosphorothioate), malathion and atrazine (6-chloro-A -ethyl-A -isopropyl-l,3,5-triazine-2,4-diamine). Parallel studies with human hand presses (full hand at 6.8 kg = ca. 6900 Pa) yielded collection efficiencies of 42 %, 29 %, 43 % and 21 %, respectively. 

A significant correlation between PCP concentrations in passively deposited particulate matter and in urine was further reported by Meissner and Schweinsberg [137]. On the other hand, no correlation was observed for PCP in household dust and blood by Liebl et al. [119], or for PCP in dust and urine by Rehwagen et al. [94]. Further, no association between concentrations in house dust or inhalable suspended particles in indoor air and of metabolites in urine was found for permethrin, a nonvolatile (particle-bound) pesticide [33,138]. 

Contradictory results for associations between pesticide levels indoors (air, dust) and results form human biomonitoring may be due to different volatilities of the pesticides and may be determined by the magnitude in contamination levels. For semivolatile pesticides it may be easier to detect an association, as indoor air and house dust may serve for exposure in contrast to particle-bound pesticides with house dust as the only exposure path. Furthermore high contamination levels make it easier to detect an association, as with low indoor contamination levels associations may be hidden by the ubiquitous presence of pesticides in indoor environments and by nonindoor exposure pathways like dietary intake. 

The BioTrol soil washing system is a patented, water-based volume reduction process used to treat excavated soil. It separates slightly contaminated, coarse, washed soil particles from heavily contaminated fine soil particles. The process operates on the premise that (1) contaminants tend to be concentrated in the fine size fraction of soil (sUt, clay, and soil organic matter) and (2) contaminants associated with the coarse soil fraction (sand and gravel) are primarily surficial. The BioTrol soil washing system can be used to treat soils contaminated with petroleum hydrocarbons, pesticides, polychlorinated biphenyls (PCBs), various industrial chemicals, and metals. 

Exposure to toxicants from terrestrial sources is very common because of the intimate association between animals and plants that live on the land with soil. Modem agricultural practices call for the application of large quantities of herbicides and other pesticides to plants and soil residues of these substances may readily enter living organisms. Soil is the repository of a variety of air pollutants, especially airborne particles that settle onto soil. Improper disposal of industrial wastes and toxic substances washed from or blown off of hazardous waste sites has contributed to exposure of soil. 

A concrete example relates to the environmental levels of e.g. PCB, dioxin, pesticides or mercury, or air contamination including small particles. These have been associated with impaired perception, intelligence and mobility in children, entailing impaired earning ability and enhanced social inequity. Several case studies have indicated a loss of around 5 IQ points in a population due to hazardous chemicals, which might mean about a 10% loss of income or about the same loss of worker productivity (Trasande et al. 2005, IFCS 2003a). 

There can also be a flammability limit associated with dust clouds. The flammability limits of combustible dusts are reported as the minimum explosion concentrations. The upper explosion limits for dust clouds have not been determined due to experimental difficulties. In the fourteenth edition of the Fire Protection Handbook [National Fire Protection Association (NFPA), Boston, MA, 1975], numerous results from the U.S. Bureau of Mines reports are listed. These results were obtained with dusts 74 fim or smaller. It should be noted that variations in minimum explosive concentrations will occur with change in particle diameter, i.e., the minimum explosive concentration is lowered as the diameter of the particle decreases. Other conditions which affect this limit are sample purity, oxygen concentration, strength of ignition source, turbulence, and uniformity of the dispersion. The NFPA tabulation is most extensive and includes data for dusts from agricultural materials, carbonaceous matter, chemicals, drugs, dyes, metals, pesticides, and various plastic resins and molding compounds. Except for metal... 

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