Table 6 Multivariable weighted stepwise linear regression models of subject‐specific means of log transformed styrene and SO levels in blood (weights are the frequencies of subject‐specific repeated measurements of styrene and SO in blood, respectively).

Response variable	Overall r2	Predictor variables	Parameter estimates	Δr2	95% CI
ln(Styrene in blood, mg/l, n = 292)	0.72	Intercept	−5.27		−5.52 to −5.02
		ln(Styrene in air, ppm)	0.994	0.68	0.899 to 1.09
		Truck manufacture	0.807	0.02	0.525 to 1.09
		Current alcohol use	0.358	0.01	0.135 to 0.581
		Pipe and tank production	0.535	0.01	0.204 to 0.866
		RV production	0.540	0.01	0.168 to 0.912
ln(SO in blood, μg/l, n = 211)	0.34	Intercept	−3.09		−3.26 to −2.92
		RV production	0.750	0.30	0.517 to 0.982
		ln(Styrene in air, ppm)	0.140	0.04	0.065 to 0.214