Table 4.

Models of standardized incidence ratios for bladder cancer by Poisson regression using cumulative estimated o-toluidine exposure prediction with reference population rates^a (10-year lag) in workers from a chemical manufacturing plant (n=1,875)

Parameter		SIR Estimateb	Std Error	Approx. 95% CI (Wald)c	Model deviance or chi square to remove variable
1	CaOut = exp(a0) × expt				-2ln(L) = 1108.680
	a0	0.9476	0.1474	0.66, 1.24
2	CaOut = exp(a0+b1×rac0) × expt				-2ln(L) = 1105.226
	a0	0.887	0.1543	0.58, 1.19
	b1	1.1292	0.5233	0.10, 2.15
3	CaOut = exp(a0+b1×rac0+c1×dur) × expt				-2ln(L) = 1095.015
	a0	0.2923	0.2698	−0.24, 0.82
	b1	1.2373	0.5245	0.21, 2.27
	c1	0.0326	0.0102	0.013, 0.053	10.2
4	CaOut = exp(a0+b1×rac0) × (1+c2×cumOT) × expt				-2ln(L) = 1076.304
	a0	0.2048	0.2612	−0.31, 0.72
	b1	1.2167	0.5236	0.19, 2.24
	c2	0.5879	0.2506	0.097, 1.080	28.9
5	CaOut = exp(a0+b1×rac0+c1×dur) × (1+c2×cumOT) × expt				-2ln(L) = 1075.97
	a0	0.1384	0.2903	−0.43, 0.71
	b1	1.2436	0.5258	0.21, 2.27
	c1	0.00796	0.0133	−0.018, 0.034	0.33
	c2	0.474	0.2592	−0.034, 0.980	19.1
6	CaOut = exp(2a0+b1×rac0) × (exp(c1×dur)+c2×cumOT) × expt				-2ln(L) = 1074.088
	a0	−0.0997	0.357	−0.80, 0.60
	b1	1.2523	0.5242	0.23, 2.28
	c1	0.0233	0.0161	−0.008, 0.05	2.22
	c2	0.7135	0.3522	0.023, 1.40	20.9

Note: CaOut – predicted incident cases cases of bladder cancer, expt – expected cases from reference population,

rac0 – indicator of non-white race (0,1), dur – employment duration, cumOT – cumulative OT exposure, in ppm-years

^aReference rates for six states (Pennsylvania, California, Ohio, Texas, Florida, and New York excluding New York City).

^bc2 is the estimate for the exposure response, or, excess relative rate per ppm-year of exposure

^cWald CI not appropriate for linear relative rate term: c2

Abbreviations: CI, confidence interval; SIR, standardized incidence ratio.