PRINCIPLES OF TOXICOLOGY - Biology East Borneo

384 PROPERTIES AND EFFECTS OF ORGANIC SOLVENTSFigure 16.7 Ethylene glycol.nose, and throat irritation; vertigo; headache; drowsiness; contact dermatitis; and corneal inflammation.No systemic effects from n-butanol typically occur at exposures less than 100 ppm. Skin irritationis common from allyl alcohol and absorption through the skin can lead to deep pain. It may causesevere burns of the eye and other ocular symptoms include lacrimation, photophobia, and blurringvision. Allyl alcohol is metabolized by the liver to allyl aldehyde, a potent hepatotoxin.The alcohols may interact in industrial circumstances with chlorinated solvents to enhance toxicitythat would occur from either group (potentiation and synergism).GlycolsThe larger alkyl-chain glycols (e.g., some of the dihydroxy alcohols) typically exhibit a lower degreeof acute oral toxicity in comparison to the monohydroxy alcohols. They are not significantly irritatingto eyes or skin, and have vapor pressures that are sufficiently low so that toxic air concentrations arenot usually observed at ambient temperature (e.g., 60–80 °F). Ethylene glycol (see Figure 16.7) is acommon example that may be used to represent the glycol family. A single oral dose on the order of100 mL is lethal in humans, because of its metabolism to oxalate (or oxalic acid) which is toxic tothe kidneys and may cause obstructive renal failure from formation of oxalate crystals. As in the caseof methanol, ethanol can be used as a competitive inhibitor of ethylene glycol toxicity by blockingthe aldehyde dehydrogenase-mediated metabolism.16.7 TOXIC PROPERTIES OF REPRESENTATIVE PHENOLSThe aromatic alcohols (also termed phenols), in which the hydroxyl group is attached to a benzenering, have the ability to denature and to precipitate proteins in a manner similar to their that of aliphaticcounterparts. This property makes phenol useful as a bacteriostatic agent at concentrations exceeding0.2 percent and an effective bactericide at concentrations in excess of 1.0 percent. However, it alsorenders these compounds quite corrosive and severe burns may result from direct contact. Fatalitieshave resulted in individuals inadvertently splashed with liquid phenol. Phenolic compounds alsoexhibit limited local anesthetic properties (hence their use in over the counter throat lozenges) and,in general, are CNS depressants at high concentrations.Dihydroxy aromatics act like simple phenols but their effects are largely limited to local irritation. Thetrihydroxy compounds may reduce the oxygen content of blood at sufficient exposure levels. Methyl phenols(or cresols), while widely used in industrial applications, typically do not pose a significant inhalation hazarddue to their relatively low vapor pressure and objectionable odor. Their physiological effects are similar tothose of phenol, and dermal exposure, if prolonged, may result in significant absorption, even to the extentthat fatalities have been reported from such exposures. Chlorinated phenols are strong irritants and exhibitsignificant oral toxicity because of their direct inhibition of cellular respiration. They also may producemuscle tremors, weakness, and, in overdose, convulsions, coma, and death.Phenol (see Figure 16.8) can be cytotoxic to cells and tissues on sufficient exposure, given theability to complex with and denature proteins. Because it is easily absorbed and it forms a loosecomplex with proteins, phenol may quickly penetrate the skin and underlying tissue, causing deepburns and tissue necrosis. This penetrating capacity, coupled with its nonspecific toxicity, renders it aserious handling hazard and all routes of exposure should be controlled carefully. If splashed on the