Handbook of Solvents - George Wypych - ChemTech - Ventech!

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ogy and occupational medicine, as well as environmental and industrial health. Dermal absorption
of benzene in workers who use either toluene containing benzene or other solvents
containing benzene, is a significant factor in calculating dosimetry and absorption of benzene
and can be calculated utilizing standard accepted methodology. A recent study by Dr.
Brenner et al. 6 described chronic myelogenous leukemia due to skin absorption of benzene
as a contaminant of other solvents. The investigators in that study 6 concluded that the total
benzene absorbed dose via skin and inhalation was equivalent to an accumulated vapor exposure
of 196.4 + 42 ppm-years. Dermal exposure accounted for 97% of the total absorbed
dose of benzene. Inhalation of benzene from occupational, smoking and ambient non-occupational
sources accounted for only 3% of the benzene dose. The authors presented the reports
of dermal absorption of benzene in the following table.
Table 20.5.1. Summary of benzene dose expressed as equivalent ppm-years.
[Adapted, by permission, from D. Brenner, Eur. J. Oncol., 3(4), 399-405, 1998.]
Case Solvent Dermal Occupational
inhalation
Cigarette
smoke
Ambient
inhalation
Total
1997 Toluene, MEK, Acetone 170.4 19.2 0.05* 0.29 189.9
1998 Case 1 Mineral spirits 41.1 17.8 0.1* 0.23 59.3
1998 Case 2 Refinery process streams 19.0 4.6 1.4 0.4 196.4
*Second hand cigarette smoke
Therefore, workers who are exposed to solvents containing benzene should be evaluated
for skin absorption dosimetry, in addition to other sources such as inhalation, to address
the range of levels of exposure.
Dose, ppm years
200
150
100
50
cummulative inhalation dose
cummulative dermal dose
0
63-66 67-72 73-78 79-83 84-91 92-93
Time period
Figure 20.5.1. Cumulative Dose of benzene over 30
years. [Adapted, by permission, from D. Brenner, Eur. J.
Oncol., 3(4), 399-405, 1998.]
Therefore, dermal absorption of benzene,
especially in connection with benzene
as a byproduct in other solvents, is of extreme
importance in dosimetry analysis.
Once benzene reaches the blood, it is
metabolized mainly in the liver. The metabolic
products are excreted in the urine
within 48 hours from absorption. Several
metabolites have been found in the urine after
benzene exposure, among those are phenol,
quinone, hydroquinone, and muconic
acid. 7 The liver utilizes the cytochrome
P450 and oxidization system for the metabolism
of benzene. 8,9
Specific cellular toxic effects from
benzene have been described and those include,
among others, the central nervous
system (doses of over 100 ppm), liver, kidney,
skin, immunological, and carcinogenic.
The various toxicological effects of
benzene will not be discussed in this chapter