PRINCIPLES OF TOXICOLOGY - Biology East Borneo

16.8 TOXIC PROPERTIES OF REPRESENTATIVE ALDEHYDES 385Figure 16.8 Phenol.skin, it produces redness and irritation with dermal injury ranging from eczema or discoloration andinflammation to frank necrosis or gangrene, depending on the degree and duration of the exposure.Following ingestion in concentrated solution, the extensive local necrosis produced by phenolin the mucous membranes of the throat, esophagus, and stomach can cause severe pain, vomiting,and tissue corrosion, which may lead rapidly to shock and death. If inhaled at sufficientconcentrations, phenol may cause chemical pneumonitis. Like many other solvents, phenol maycause tissue damage and necrosis in the liver and kidneys following absorption and systemicdistribution. It is more potent in this respect than most organics, and phenol may producedegenerative or necrotic changes in the urinary tract and the heart as well. A rapid fall in bloodpressure may result from the CNS-depressant properties of phenol on vasomotor control, andbecause it exerts direct effects on the myocardium and small blood vessels. If acute poisoningoccurs, death is usually the result of respiratory depression. However, a brief period of CNSstimulation and convulsions may be initially observed.Estimated lethal oral doses of phenol have been reported as low as 1–2 g in some individuals. On a ppmbasis, the TLV of phenol is equivalent to that established for vinyl chloride (i.e., 5 ppm). Phenol’s dermalhazard is underscored by anecdotal reports involving individuals on whom phenol accidentally was splashed.In one case, accidentally spraying over the thighs was fatal within 10 min of exposure (illustrating its rapiddermal absorption) despite attempts to remove the clothing and to rinse the phenol off with water.Other Phenolic CompoundsSubstituted phenolics include catechol (ortho-dihydroxybenzene), resorcinol (meta-dihydroxybenzene),hydroquinone (para-dihydroxybenzene), and the cresols (or methylphenols), all of which have toxicologicalproperties that are qualitatively similar to phenol. The alkyl substitutions tend to increase the toxicity andall of the substituted phenols may be considered to be more toxic than the parent phenol. Catechol mayinduce methemoglobinemia in addition to those toxic effects previously described for phenol.16.8 TOXIC PROPERTIES OF REPRESENTATIVE ALDEHYDESThe aldehydes (see Figure 16.9) may cause primary irritation of the skin, eyes, and mucosa of therespiratory tract. These phenomena are most evident in aldehydes with lower molecular weightsand those with unsaturated aliphatic chains. Although a number of the aldehydes can producenarcosis, this effect rarely is observed because the irritation that accompanies exposure generallyserves as a sufficient warning property. Some of the aldehydes, such as fluoroacetaldehyde, canbe converted to the corresponding fluorinated acids, giving them an extraordinarily high degreeof systemic toxicity. The irritant properties of the dialdehydes have not been intensively studied.However, in some instances, concentrated solutions can be severe ocular and dermal irritants. Theacetals and the aromatic aldehydes generally exhibit a greatly reduced potential for directirritation.An endpoint of toxicity that is common to aldehydes, but is not common to most other organicsolvent constituents, is sensitization. Formaldehyde is the most common agent among thealdehydes with respect to this problem, and sensitization reactions have been reported in persons