PRINCIPLES OF TOXICOLOGY

382 PROPERTIES AND EFFECTS OF ORGANIC SOLVENTS
While PAHs can be acutely toxic, this characteristic generally is relevant only at doses sufficiently
great that they are not of interest in an industrial or environmental setting. At high, acute doses, PAHs
are toxic to many tissues and degenerative changes may ultimately be observed in the kidney and liver,
but the thymus and spleen are particularly sensitive to acute effects. For example, the noncarcinogen
PAH acenaphthene, given in doses as high as 2000 mg/kg, produces only minor changes in the liver
or kidney and is relatively nontoxic when compared to the hematoxicity produced by 100 mg/kg of
dimethylbenzanthracene, a much more potent PAH.
Several of the PAHs with four, five, or more rings (e.g., benzo-a-pyrene, benzo-a-anthracene,
benzo-b,k-fluoranthene) have been classified as possible carcinogens by a number of environmental
regulatory agencies. Occupational guidelines have been established for a chemical category known as
“coal tar pitch volatiles,” which includes some PAHs.
16.6 TOXIC PROPERTIES OF REPRESENTATIVE ALCOHOLS
Alcohol Compounds: R–OH
As a general observation, alcohols are more powerful CNS depressants than their aliphatic analogs. In
sequence of decreasing depressant potential, tertiary alcohols with multiple substituent OH groups are more
potent than secondary alcohols, which, in turn, are more potent than primary alcohols. The alcohols also
exhibit irritant potential and generally are stronger irritants than similar organic structures that lack functional
groups (e.g., alkanes) but are much less irritating than the corresponding amines, aldehydes, or ketones. The
irritant properties of the alcohol class decrease with increasing molecular size. Conversely, the potential for
overall systemic toxicity increases with greater molecular weight, principally because the water solubility
is diminished and the lipophilicity is increased. Alcohols and glycols (dialcohols) rarely represent serious
hazards in the workplace, because their vapor concentrations are usually less than the required irritant levels,
which, in turn, prevents significant CNS effects as well.
Methanol (see Figure 16.5), also known as methyl alcohol or wood alcohol, is the simplest structural
member of the alcohols and is widely employed as an industrial solvent and raw material for
manufacturing processes. It also is used as one of several possible adulterants to “denature” ethyl
alcohol, which then is used for cleaning, paint removal, and other applications. The denaturing process
in theory prevents its ingestion.
Methanol is of toxicological interest and industrial significance because of its unique toxicity to
the eye, and it has received considerable attention from the medical community over the years due to
misuse, as well as accidental or intentional human consumption. It has been estimated that methanol
ingestion may have been responsible for 5–10 percent of all blindness in the U.S. military forces during
World War II. Methanol intoxication typically exhibits one or more of the following features:
• CNS depression, similar to or greater than that produced by ethyl alcohol (ethanol)
• Metabolic acidosis, caused by degradation of methanol to formic acid and other organic acids
• Ototoxicity, expressed as specific toxicity to retinal cells caused by formaldehyde, an
oxidation product of methanol
Figure 16.5 Met hanol.