Table 4

Relation between styrene exposure variables and serum prolactin concentration adjusted for gender, age, and smoking using multiple linear regression

Model	B	SE	p value	n
The log (base 10) transformation was used for the concentrations of styrene in air (ppm), styrene in blood (mg/l), and serum prolactin (PRL, ng/ml). For the acute exposure model air or blood styrene concentrations obtained on the same day as the PRL concentration were used. The outcome variable for the acute models was the PRL concentration obtained on the same day as the blood and air styrene concentrations. For the subchronic exposure models, air or blood styrene values were averaged over all the study sessions (2 or 3 sessions, approximately one year apart) for each subject who participated in more than one session. For the chronic exposure models all the air styrene values for the individual were averaged and multiplied times the number of years the subject had worked in that industry or facility. For the subchronic and chronic models the outcome variable was the serum PRL concentration obtained during the last session for that individual (the second or third session). Gender was coded as 0 for men and 1 for women.
n, number of observations included in analysis. For the acute models only the data from session 1 were used. For subchronic and chronic models, only subjects for whom there was data from more than one study session were included.
Acute
Blood styrene	0.314	0.137	0.023	205
Gender	0.0825	0.039	0.035
Age	−0.0012	0.001	0.359
Cigarettes per day	−0.0039	0.001	0.006
Intercept	1.090	0.063	<0.001
Air styrene	0.0548	0.028	0.053	227
Gender	0.0820	0.038	0.030
Age	−0.0011	0.001	0.424
Cigarettes per day	−0.0042	0.001	0.002
Intercept	1.061	0.073	<0.001
Subchronic
Blood styrene	0.279	0.171	0.105	175
Gender	0.0179	0.042	0.669
Age	−0.0031	0.001	0.034
Cigarettes per day	−0.0071	0.002	<0.001
Constant	1.088	0.061	<0.001
Air styrene	0.0563	0.031	0.074	175
Gender	0.0093	0.041	0.823
Age	−0.0030	0.002	0.051
Cigarettes per day	−0.0063	0.002	<0.001
Intercept	1.045	0.077	<0.001
Chronic
Total years in industry * total average air styrene	0.0403	0.021	0.060	175
Gender	0.0128	0.042	0.758
Age	−0.0040	0.001	0.005
Cigarettes per day	−0.0066	0.002	<0.001
Intercept	1.081	0.063	<0.001
Total years in facility * total average air styrene	0.0263	0.023	0.255	175
Gender	0.0120	0.042	0.777
Age	−0.0038	0.001	0.007
Cigarettes per day	−0.0064	0.002	<0.001
Intercept	1.104	0.064	<0.001