Appendix D - Dossier (PDF) - Tera

date: 20–JUL–2005
5. Toxicity Substance ID: 71–43–2
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Type: other: effects on pregnancy
Method: SUBJECTS
The study population was recruited from female employees
working for the Beijing Yanshan Petrochemical Corporation
(BYPC), Peoples Republic of China. Eligible women were
defined as non–drinking, non–smoking mothers who had a live
single birth at the BYPC staff hospital between June 1995
and June 1997. This resulted in recruitment of 302 reference
(non–exposed) individuals and 240 benzene–exposed subjects
(total: 542). Clinical and personal data were collected by
interviewer–administered questionnaire. In general, pregnant
employees stopped working at 28 weeks of gestation.
Appendix D: Benzene SIDS Dossier
GESTATIONAL AGE
The first date of the last menstrual period recorded at the
first prenatal visit was used to estimate gestational age in
days. The authors considered that prevailing social and
administrative considerations within the Peoples Republic of
China meant that this would be reliably noted by the
participants.
EXPOSURE ASSESSMENT
The authors note that, in general, time–weighted average for
benzene exposure in the
BYPC facility was a range 0.017–0.191 ppm. Maternal
occupational exposure to benzene was assessed qualitatively
according to a woman’s workshop, job title and job activity.
Air sample measurements for benzene, toluene, styrene,
xylene and their derivatives were obtained from major
workshops during the study period. The subjects were then
classified into 3 groups based upon (1) no exposure to
organic solvents; (2) exposure to benzene; and (3) exposure
to other solvents (including styrene, toluene, xylene and
their derivatives but not benzene). Note: only results for
the benzene–exposed and non–benzene–exposed individuals were
presented in this study report.
GENOTYPING
POLYMORPHISM OF CYP1A1
Maternal genomic DNA was subject to 35 rounds of
amplification using the polymerase chain reaction, followed
by digestion of the products with HincII and agarose gel
electrophoresis with ethidium bromide staining and
visualisation under UV light. Homozygous wild–type
individuals for cytochrome P450 1A1 (CYP1A1) show 139– and
32–base pair (BP) fragments (BPF), while heterozygous
subjects show 4 bands at 139, 120, 32 and 19 BP,
respectively. Homozygous rare–allele individuals show only
120–, 32– and 19 BP bands.
POLYMORPHISM OF GSTT1
Wild type homozygous glutathione S–transferase (GSTT1) was
indicated by an amplified 457–BP product after PCR and
agarose gel electrophoresis, while the null genotype was
characterised by the absence of the 457–BP band.
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