Genotoxic changes after low-level solvent and fuel exposure on aircraft maintenance personnel
Grace Kawas Lemasters
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Gordon K.Livingston
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James E.Lockey
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Donna M.Olsen
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Rakesh Shukla
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George New
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Sherry G.Selevan
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James H.Yiin
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University of Cincinnati
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231 Bethesda Avenue, Cincinnati, OH 45267- 0182
,
USA
'To whom correspondence should be addressed
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Individuals may be exposed to solvent mixtures and fuel
either at work or home, through air, water and food
contamination. Few studies have addressed the genotoxic
effects of mixed, low-level exposure to fuel and solvent.
This was an optimally designed study where each subject
was sampled prior to exposure and after 15 and 30 weeks
while exposed, in a repeated measures design with each
subject serving as his own control. Fifty men aged between
18 and 50, working on aircraft equipment operation and
maintenance at a military installation were included. Eight
unexposed men were concurrently sampled.
Sisterchromatid exchanges (SCE) and micronuclei (MN)
frequency were measured in conjunction with air sampling
and expired breath analysis for jet fuel (JP-4),
1,1,1trichloroethane, methyl ethyl ketone, xylenes, toluene and
methylene chloride. Exposure levels measured by industrial
hygiene were very low (all means <6 p.p.m.), <10% of the
OSHA standard. Expired breath levels were also low, <25
p.p.b. A small but statistically significant increase in the
frequency of SCE occurred after 30 weeks of exposure for
sheet metal workers (P = 0.003) and for painters (P =
0.05). The MN frequency in the sheet metal workers initially
showed a statistically significant increase, but by 30 weeks
had decreased. Cigarette smoking, alcohol and caffeine use
were not associated with changes from baseline for either
MN or SCE. Smokers, however, had significantly higher
values of SCEs at baseline than did nonsmokers. In
summary, these findings suggest that small increases in
SCEs in particular, may serve as a sensitive biologic
indicator of low level hydrocarbon exposure in as much as
statistically significant changes occurred in the highest
exposed groups but not in the low or no exposure groups.
Chance occurrence or exposures to other occupational or
non-occupational agents cannot be eliminated as a cause
of the study findings.
Introduction
Most people are exposed to solvent mixtures and/or fuels
either at work, home or through air, water and food
contamination. 1,1,1-Trichloroethane (TCA), xylene, toluene, methyl
ethyl ketone (MEK) and methylene chloride are found in a
variety of compounds including solvents, paints and gasoline.
The widespread use of mese chemicals to clean or degrease
parts also requires the disposal of large volumes each year.
Fuels and benzene (as a fuel component) also represent an
intermittent, ubiquitous low-level source of exposure for the
general population. The US Environmental Protection Agency
estimates uiat 3.6X108 gallons of gasoline are released as
vapors into the atmosphere. Automobile refueling at retail
service stations is thought to account for ~40% of reported
gasoline vapor emissions (Mehlman, 1992). In the US, ~70%
of gasoline is dispensed from self-service pumps causing vapor
exposure to ~110 million people (Maklan et al, 1987).
Results of population studies of solvent and fuel exposure
and their effect on the frequency of sister chromatid exchange
(SCE) and micronuclei (MN) have been mixed due to the
variety of exposures studied (Van Hummelen et al, 1994;
Yager et al, 1993; Laurent et al, 1993; McDiarmid et al,
1995; Hallier et al, 1993; Hallier et al, 1994; Sardas et al,
1994; Richer et al. 1993; Suruda et al, 1993). For example,
continuous, low-dose benzene exposure increased SCE
frequency (Major et al, 1994), automobile painters with mixed
solvent exposure had significantly higher SCEs (Sardas et al,
1994), and inhabitants of a village in Belgium located at the
edge of an industrial waste dump showed significantly higher
SCE rates than non-residents (Laurent et al, 1993). A
controlled exposure experiment using either single exposures to
xylene and toluene, or the two in combination, however,
showed no significant genotoxic effects (Richer et al, 1993).
In addition, a study of US mortuary science students comparing
MN frequencies prior to their first exposure to embalming
fluid (formaldehyde) and again after 90 days of exposure,
found an increase of MN from 5.0 to 6.4 MN/1000, while
SCEs decreased by 7.5% (Suruda et al, 1993). A study of
plastics workers exposed to styrene, another hydrocarbon,
found that MN in both the exposed and unexposed populations
averaged between 3.3 and 4.8, respectively (Van Hummelen
et al, 1994). Conversely, a study in Germany of styrene and
dichloromethane exposure demonstrated a significant
difference between mean MN frequency in the exposed population
of 35.1 compared to the unexposed mean of 14.3 (Tates
etal, 1994).
Smoking is known to increase the frequency of SCE. A
study conducted by Livingston and Fineman (1983) compared
24 smokers with 24 sex and age matched controls who
had never smo (...truncated)