Human Toxicity - The Toxicology of Methanol - page 53

In a study of volunteers exposed to 800 ppm of methanol for up to 8
hours (0.5, 1, 2, and 8 hours), methanol was measured in blood, urine, and
breath. Methanol levels were approximately linerly related to exposure
concentration, but showed a large interindividual variation. The blood
methanol level after 8 hours was 31mg/l (Batterman et al., 1998).
In a study of volunteers exposed to 400 ppm of methanol for 8 hours,
methanol and formate were measured in urine. Methanol levels were not
proportional to duration of exposure because of metabolism and other
elimination processes. Formate in the urine was not judged to be a
useful indicator of air borne methanol exposure because it was poorly
related to airborne methanol exposure levels (Franzblau et al., 1997).
3.3.3.3 Urinary Formic Acid Urinary levels of methanol accurately
reflect concentrations in the blood over a wide range of concentrations,
but urinary excretion of formic acid was too variable to be of value in
exposure assessment (Ferry et al., 1980).
3.3.3.4 Breath—Methanol Levels Methanol was measured in the
blood and the breath in a study of volunteers exposed to inhalation
concentrations of methanol up to 800 ppm for 8 hours with or without
exercise. Eight individuals were also exposed dermally by placing the
hand in a large beaker of methanol for 16 minutes. Methanol was
measured in the blood and the breath before exposure and after 6 and 8
hours of exposure. Significant increase in blood and breath were seen
after 6 and 8 hours after exposure to 400 ppm methanol. Breath
methanol levels peaked 15 minutes after dermal exposure. On the basis
of blood methanol levels, 8 minutes of dermal exposure (one hand in a
beaker of methanol) was equal to the blood methanol level seen by
inhalation at the TLV (200 ppm) (Franzblau et al., 1995). In a follow-up
study, the methanol dermal absorption rates averaged 8.1 þ / 3.7
mg/cm 2 /h in individuals, who had exposed their hand in a large beaker
of methanol for 16 minutes. Methanol blood levels peaked 0.5 hour after
exposure (Batterman and Franzblau, 1997).
The controlled human studies discussed above indicate that the
workplace standard of 200 ppm is adequate to prevent clinical symp-
toms and significant elevation of methanol and its metabolite in the