Penetration pesticides

Skin is also important as an occupational exposure route. Lipid-soluble solvents often penetrate the skin, especially as a liquid. Not only solvents, but also many pesticides are, in fact, preferentially absorbed into the body through the skin. The ease of penetration depends on the molecular size of the compound, and the characteristics of the skin, in addition to the lipid solubility and polarity of the compounds. Absorption of chemicals is especially effective in such areas of the skin as the face and scrotum. Even though solid materials do not usually readily penetrate the skin, there are exceptions (e.g., benzo(Lt)pyrene and chlorophenols) to this rule. 

Dihexyl sulfosuccinate is used to improve the wetting and spreading characteristics of water-soluble pesticide sprays. In liquid fertilizers, insecticides, and fungicides, dioctyl sulfosuccinate will increase their penetrating ability. 

Leonas KK, Easter EP, Dejonge JO. 1989. Effect of fabric characteristics on pesticide penetration through selected apparel fabrics. Bull Environ Contam Toxicol 43 231-238. 

Archibald BA, Solomon KR, Stephenson GR. 1994a. Ruorescent tracer and pesticide penetration through selected protective clothing. Bull Environ Contam Toxicol 53(4) 479-485. 

For most chemicals, inhalation is the main route of entry into the body. However, certain chemicals (e.g. phenol, aniline, certain pesticides) can penetrate intact skin and so become absorbed into the body. This may occur through local contamination, e.g. from a liquid splash, or through exposure to high vapour concentrations. Special precautions to avoid skin contact are required with these chemicals and potential exposure via skin absorption has to be taken into account when assessing the adequacy of control measures. Chemicals able to penetrate intact skin are listed in Table 4.2. 

SFE of fruits and vegetables and meat products has been reported, but the sample preparation techniques necessary to obtain reproducible results are extremely time consuming. Solid absorbents such as Hydromatrix, Extrelut " anhydrous magnesium sulfate or absorbent polymers are required to control the level of water in the sample for the extraction of the nonpolar pesticides. Without the addition of Hydromatrix, nonpolar pesticides cannot penetrate the water barrier between the sample particles and the supercritical CO2. The sample is normally frozen and the addition of dry-ice may be required to reduce losses due to degradation and/or evaporation. Thorough reviews of the advantages and limitations of SFE in pesticide residues... 

Penetrating through the respiratory and intestinal tracts, and the integument, pesticides undergo a dual transformation [6] both chemical transformations (oxidation, reduction, hydrolysis), and the formation of complex compounds with biochemical components in the body. 

Crowse, J.L., Dejonge, J.O., and Calogero, F. (1990) Pesticide barrier performance of selected nonwoven fabrics in laboratory capillary and pressure penetration testing, Textile Research., 60 137-142. 

Freed, V.H., Davies, J.E., Peters, L.J., and Parveen, F. (1980) Minimizing occupational exposure to pesticides repellency and penetrability of treated textiles to pesticide sprays, Res. Rev., 75 159-167. 

Nigg, H.N., Stamper, J.H., Easter, E.P., and Dejonge, J.O. (1992) Field evaluation of coverall fabrics heat stress and pesticide penetration, Arch. Environ. Contam. Toxicol., 23 281-288. 

Colorless to white hygroscopic crystals that are odorless. Pesticide grade is often dyed blue. This material is hazardous through inhalation, skin absorption, penetration through broken skin, and ingestion, and produces local skin/eye impacts. 

Grissom, R.E., Jr. C. Brownie, and F.E. Guthrie. 1987. In vivo and in vitro dermal penetration of lipophilic and hydrophilic pesticides in mice. Bull. Environ. Contam. Toxicol. 38 917-924. 

When a droplet falling at a certain velocity impacts on an object, it will wet and spread through the surface if the contact angle is less than 90°. If the object is very thin, the droplet may all soak into it and the liquid may reach the other side that can be seen if the droplet contains a tracer dye. In a thick and porous Kromekote card,l507] a droplet spreads to form a circular stain with simultaneous absorption and penetration into the card. Kromekote cards have been used in forestry spray trials to collect pesticide droplets for... 

A possible source of groundwater contamination, which has up to now almost been neglected, is associated with the introduction of surfactants into soils as pesticide additives (Table 6.7.3). Non-ionic surfactants composed of alcohols and fatty acids are most widely recommended as adjuvants to facilitate and enhance the absorbing, emulsifying, dispersing, wetting and penetrating properties of pesticides. Other pesticide adjuvants are silicone-based surfactants,... 

Shah PV, Fisher HL, Sumler MR, et al. 1987. Comparison of the penetration of 14 pesticides through the skin of young and adult rats. J Toxicol Environ Health 21(3) 353-366. 

Weil CS, Condra NJ, Carpenter CP. 1971. Correlation of four hour vs. 24 hour contact ski penetration toxicity in the rat and rabbit and use of the former for prediction of relative hazard of pesticide formulations. Toxicol Appl Pharmacol 18 734-742. 

Fig. 12.18A shows the results of an experiment using " C-labeled paraquat adsorbed on a clay mineral (Li-montmorillonite) suspension through a soil column. When the suspension medium was distilled water, 50% of the pesticides penetrated beyond 12 cm. Under these conditions, clay remains dispersed and pestieide is readily transported through the soil. However, for a suspension medium with an electrolyte concentration of 1 mM CaCl, paraquat remains in the upper 1 cm layer. The high calcium concentration results in rapid immobilization of the clay in the soil through flocculation, and consequently little pesticide transport occurs. 

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