Pesticide chemical penetration through

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. 

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. 

The quantity of suspended dust inhaled and the intake of pesticides adsorbed to it may be calculated rather exactly, and the intake of pesticides from deposited dust via oral pathways may at least be roughly estimated. But data supporting the amount of chemicals absorbed through dermal contact of contaminated house dust and through direct contact to contaminated surfaces are still lacking. Semivolatile pesticides like chlorpyrifos will accumulate not only in house dust but also on toys and on sorband surfaces [134]. Data from the NHEXAS of Arizona support the importance of dermal penetration of semivolatile pesticides like chlorpyrifos and diazinon as a route of residential human exposure [116]. 

Recent research has demonstrated that electrospun membranes possessed excellent barrier performance against toxins in aerosol form and maintained high WVT simultaneously. Electrospun nanoflber-coated nonwoven fabrics remarkably blocked liquid pesticide penetration through the materials which make them practically more desirable as compared to the conventional fabrics and porous coatings (Fig. 14.1). The aim of this chapter is then to give a detailed overview of recent advances in the application of breathable and waterproof, chemical and antimicrobial, and radiation protective materials fabricated from electtospinning. 

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. 

In 1971 M T Chemicals (USA) began marketing 1-para-chlorophenylsilatrane as a new rodenticide under the trade mark RS-15030, 3 ). This first organosilicon pesticide had an advantage over other known toxicants. This highly toxic compound is rapidly inactivated in poisoned rodents, so their corpses are not harmful to other animals. Furthermore, RS-150 penetrates very poorly through the skin (its cutaneous toxicity is 3000 mg/kg for rats)31). Finally, rats do not become resistant to l-(4 -chlorophenyl)silatrane as was the case with other 1-arylsilatranes. Practically complete lack of smell is another important advantage of this preparation and other 1-arylsilatranes. 

Worker pesticide exposure which is primarily dermal can be acquired either as a result of accidental spillage or as a result of saturation of the clothing and penetration of the chemical through the fabric. Both laboratory and field data from these studies suggested that significant worker protection against... 

The stratum comeum, composed of keratinized dead cells that are continually being replaced, is the first major barrier to chemical agents. The barrier qualities of the stratum comeum depend on a number of factors, including its location on the body, which affects thickness, and how much hair is present. Thus, hair follicles and sweat glands can either provide charmels through the stratum comeum, and thereby bypass its barrier attributes, or at least provide increased surface area for penetration of compounds, since a number of compounds were shown to penetrate faster in hair follicle-rich areas (lUel et al, 1991). Maibach studied three radiolabeled pesticides -parathion, malathion, and carbaryl - for their permeability at 13 different anatomical sites in humans (Maibach et al, 1971). Variations in percutaneous penetration were observed higher penetration of the pesticides occurred at the abdomen and dorsum of the hand. 

Additional sulfur-containing substances that penetrate the environment include intermediates, byproducts and waste products of the chemical, pulp, coal, and petrol industries, as well as compounds used in dye production such as thiols, thiophenes, sulfides, thiazoles, sulfoxides, sulfones, and sulfonic acids. Agriculture contributes to soil and water pollution through the widespread use of pesticides containing sulfur. Unfortunately, warfare agents are still produced. 

Pesticides are chemicals or biological substances used to kill or control pests. They fall into three major classes insecticides, fungicides, and herbicides. Others classes are rodenticides, nematicides, molluscicides, and acaricides. These chemicals can be natural compounds or synthetic ones. Pesticides may also be divided into contact and systemic pesticides. Pesticides that were earlier produced were of the contact type. They do not appreciably penetrate plant tissue, so they are susceptible to the effects of the weather and moreover new plant growth is not protected. Vice versa, most of the recently developed pesticides are systemically active. They move through the plant vascular system and thus they not only can protect a plant from attack but also inhibit or cure established infections. Systemic pesticides are not affected by weathering and also confer immunity to all new plant growth. In 1993, 57% of all the pesticides used in the United States were herbicides, while 23% and 12% were insecticides and fungicides, respectively [1]. 

Surfactants and solvents are added to commercial pesticides to increase adsorption by targeted species. These chemicals also enhance the adsorption through mammalian skin. In a laboratory animal experiment, dermal penetration of atrazine, alachlor, and trifluralin was significantly lower for the pesticides alone than when contained in commercial versions of aU three. It was also shown that the solvents contained in the commercial trifluralin enhanced the dermal penetration of the other two commercial formulas when the pesticides were mixed together [30]. Pesticides are often applied in mixtures. This study shows that such mixing can have important implications for the health of those who come in contact with such mixtures. 

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