IARC MONOGRAPHS ON THE EVALUATION OF CARCINOGENIC ...

STYRENE 445
most samples taken from these workers at the end of a shift: < 10 mg/g creatinine for
mandelic acid (5 ng/mL) and < 2 ng/mL for styrene in blood. The maximal concentrations
were 140 mg/g creatinine for mandelic acid and 90 ng/mL for styrene in blood
(Wolff et al., 1978). In a German styrene production, polymerization and processing
plant, samples taken in 1975–76 in various areas of the plant contained none (< 0.01 ppm
[0.04 mg/m 3 ]) to 6.8 ppm [29 mg/m 3 ], most values being below 1 ppm [4.3 mg/m 3 ]. In
a part of the plant where polystyrene was manufactured, area samples in 1975 contained
from none (< 0.01 ppm [0.04 mg/m 3 ]) to 47 ppm [200 mg/m 3 ], most values being below
1 ppm [4.3 mg/m 3 ]. Of 67 employees engaged in either area of the plant, six had urinary
concentrations of mandelic acid above 50 mg/L (Thiess & Friedheim, 1978).
Other substances that may be found in workplace air during the manufacture of
styrene and polystyrene include benzene, toluene, ethylbenzene, other alkylbenzene
compounds and ethylene (Ott et al., 1980; Lewis et al., 1983; National Institute for
Occupational Safety and Health, 1983). Exposure to benzene was previously a primary
concern in these processes. In the plant in the USA described above, the TWA concentration
of benzene in styrene monomer manufacture was 0.3–14.7 ppm [1–47 mg/m 3 ]
between 1953 and 1972. Samples taken in 1942 during a washing operation in the polymerization
plant contained up to 63 ppm [202 mg/m 3 ] benzene (Ott et al., 1980).
(b) Production of styrene–butadiene rubber (SBR) and other styrenebased
polymers
Concentrations of styrene in area samples and breathing-zone air measured in 1965
in various plants of a styrene–butadiene latex manufacturing company in the USA (see
above) were 4–22 ppm [17–94 mg/m3 ]. The initial stages of the process, including
loading, operating and cleaning of polymerization reactors, involved the highest exposure,
and operators in these job categories were exposed to concentrations ranging from
3.6 to 7.3 ppm [15–31 mg/m3 ] in 1973 (Ott et al., 1980).
In two adjacent SBR production plants in the USA, the TWA concentrations of
styrene were 0.94 and 1.99 ppm [4 and 8.5 mg/m3 ], with an overall range of
0.03–12.3 ppm [0.13–52.4 mg/m3 ] (Meinhardt et al., 1982). The mean concentrations in
159 personal air samples taken in 1979 in various departments at another SBR production
plant in the USA were usually below 1 ppm [4.3 mg/m3 ], except for factory
service and tank farm workers, for whom the means were 1.69 and 13.7 ppm [7.2 and
58.2 mg/m3 ], respectively (Checkoway & Williams, 1982). Company data provided by
five of eight SBR plants in the USA for the period 1978–83 gave an average styrene level
in 3649 samples from all plants of 3.53 ppm [15 mg/m3 ], with a standard deviation of
14.3 ppm [61 mg/m3 ] (Matanoski et al., 1993). A study by Macaluso et al. (1996) of the
same facilities as the Matanoski study used industrial hygiene data together with a series
of air dispersion models to estimate how TWA styrene exposure levels in the styrene–
butadiene resin industry may have changed since the 1940s. Their calculations suggest
that TWA exposures declined from an average of 1.8 ppm [7.7 mg/m3 ] during the 1940s
to 0.1 ppm [0.4 mg/m3 ] in the 1990s.