Table 1

Characteristics of the study population, Beijing Yanshan Petrochemical Corporation, China

No exposure
(n=438) mean (SD)
Exposure to benzene
(n=354) mean (SD)
Age (y)27.0  (2.4)26.7  (1.9)
Duration of employment (y)5.7 (3.0)6.3 (2.7)
Weight before pregnancy (kg)57.8 (9.3)58.3 (9.7)
Height before pregnancy (cm)161.5 (5.0)161.0 (4.7)
BMI before pregnancy (kg/m2 )22.2 (3.5)22.5 (3.6)
Birth weight (g)3464 (429)3382 (451)
Gestational age (weeks)40.0 (1.3)39.8 (1.5)
n (%) n (%)
Age (y):
 20–2594 (21.5)70 (19.8)
 26–29276 (63.0)250 (70.6)
 30–4068 (15.5)34 (9.6)
Education:
 Middle school or lower45 (10.3)33 (9.3)
 High school217 (49.5)247 (69.8)
 College or above176 (40.2)74 (20.9)
Passive smoking at home or work239 (55.6)218 (61.8)
Parity (one or more)18 (4.1)14 (4.0)
Female baby215 (49.1)171 (48.7)
Work stress85 (19.4)57 (16.1)
Noise56 (13.0)151 (42.8)
Physical exertion105 (24.0)89 (25.1)
Other hazards22 (5.0)86 (24.3)
Work mainly in a sitting posture250 (57.1)245 (69.2)