Absorption, of toxicants

Skin functions as both, an important physical barrier to the absorption of toxic substances and simultaneously as a portal of entry of such substances. The stratum comeum of the epidermis is most significant in providing some degree of physical... 

McKee R, Freeman J. 1993. Dermal carcinogenicity studies of petroleum-derived materials. In RGM Wang, JB Knaak, HI Maiback, eds.. Health Risk Assessment Dermal and Inhalation Exposure and Absorption of Toxicants CRC Press, Ann Arbor MI, 263-21 A. 

Although there are several sites of first contact between a foreign compound and a biological system, the absorption phase (and also distribution and excretion) necessarily involves the passage across cell membranes whichever site is involved. Therefore, it is important first to consider membrane structure and transport in order to understand the absorption of toxic compounds. 

Pure ethanol is a clear liquid with a characteristic though faint odor. Like methanol, ethanol has a high latent heat of vaporization which can be demonstrated by dipping a finger in ethanol and letting it dry which causes rapid cooling. In cold weather, frostbite is a concern when handling ethanol because its latent heat can cause exposed skin to freeze. (Skin contact should be avoided with all fuels to prevent absorption of toxic compounds into the body.)... 

Inhalation (into the lungs). This is a more common pathway for the absorption of toxic chemicals these may be in the form of gases, vapours, dusts or mists. All toxic powders, volatile liquids and gases should only be handled in efficient fume cupboards. The practice of sniffing the vapours of unknown compounds for identification purposes should be conducted with caution. 

The skin represents the largest organ in the human body, and one of its primary functions can be seen as a physical barrier to absorption of toxicants. The other major routes of toxicant entry into the body are through the respiratory and gastrointestinal tract, which can be seen to offer less resistance to toxicant absorption than the skin. In general, the respiratory tract offers the most rapid route of entry, and the dermal the least rapid. One reason for this major difference is primarily because membrane thickness, which is really the physical distance between the external environment (skin surface, air in the lung, or lumen of the gut) and the blood capillaries, varies across these portals of entry. The overall entry depends on both the amount present and the saturability of the transport processes involved. 

Reducing further exposure to a toxicant is crucial and may include removal of the patient from a toxic environment and the application of decontamination procedures. Immediate decontamination reduces absorption of toxic compounds and represents a primary essential aspect of the treatment regimen. 

Walsh, C.T. 1990. Anatomical, Physiological, Biochemical Characteristics of the Gastrointestinal Tract. Iln T.R. Gerrity and C.J. Henry, Eds., Principles of Route-to-Route Extrapolation for Risk Assessment, pp 33-50. Elsevier New York, N.Y.Wester, R.C., and H.I. Maibach. 1997. Toxicokinetics Dermal Exposure and Absorption of Toxicants. In I.G. Sipes, C.A. McQueen, and A.J. Gandolfi, Eds., Comprehensive Toxicology Volume General Principles (J. Bond, volume editor), pp. 99-114. Pergamon Press, New York, N.Y. 

An early sign of exposure may be yellow staining of skin and hair. If urine or sderae are stained, absorption of toxic amounts should be assumed. Common early symptoms include headache, profuse sweating, lassitude, malaise and thirst. More serious indications are warm flushed skin, tachycardia, and fever. Apprehension, restlessness and anxiety, manic behavior or unconsciousness indicate... 

Fthenakis, V. M. and V. Zakkay, 1990. A Theoretical Study of Absorption of Toxic Gases by Spraying. Journal of Loss Prevention in the Process Industries, 3 197-206. 

Wu, J.S., Monk, T., Luttmann, D.R., Meininger, T.A., Soper, N.J. (1998). Production and systemic absorption of toxic b q)rod-ucts of tissue combustion during laparoscopic cholecystectomy. J. Gastrointest. Surg. 2 399-405. 

There are many different animal models that have been used to assess the percutaneous absorption of toxic chemicals. There is little question that while in vivo human studies are best for predicting the absorption of percutaneous applied chemical warfare agents, ethics preclude conducting such studies. Rats have been widely used in the study of skin contamination, wounds, and healing and the efficacy of different decontamination modalities (Wester and Maibach, 2000 Shah et al, 1987 Baynes et al., 1997). 

SAFETY PROFILE Poison by intravenous and intraperitoneal routes. Moderately toxic by ingestion. A human skin irritant. This material yields hydrogen sulfide on decomposition. A death has been attributed to the absorption of toxic decomposition products from the use of this material in a hair permanent-waving solution. When heated to decomposition it emits toxic fumes of SOx and Na20. See also SULFIDES and MERCAPTANS. 

Figure 1. A schematic showing how chemicals may enter, be absorbed into, distributed within, and excreted from the body. Adapted in part from C.D. Klaassen, Distribution, Excretion, and Absorption of Toxicants, Chapter 3 of Casarett and Doull s Toxicology (see Recommended Readings).

Chitin is known to be biodegradable, biocompatible, and nontoxic. It is used in dmg delivery and bio medical applications. It also used in the purification of water especially for the absorption of toxic dyes. Chitin has limited solubility in solvents but chitosan is readily soluble in acidic aqueous solutions and has more tendency to be chemically modified. Chitosan can readily be spun into fibers, cast into films, or precipitated in a variety of micromorphologies from acidic solutions. Min and Kim have reported on the adsorption of acid dyes from wastewater using composites of PAN/chitosan [52]. Shin et al. has reported on copolymers composed of PVA and poly dimethyl siloxanes cross-linked with chitosan to prepare semi IPN hydrogels for application as biomedical materials... 

BILBERRY, Myrtilli fructus Bilberry is the fruit of Vaccinium myrtillus, L., family Ericaceae, and contains 5-10% tannins of the catechin-type, anthocyanins, flavone glycosides and organic acids. The tannins in bilberry and in other tannin-containing drugs precipitate proteins in the epithelium of the intestine. In this way the absorption of toxic substances and secretion is diminished. This is the mode of action in the treatment of diarrhoea. 

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