Table 4.

Associations between BCC and As according to urine iAs metabolite levels among participants with sum of iAs metabolites ≥ 2.5 μg/L (n = 856).

Arsenic exposure index	< Mediana [ORb (95% CI)]	≥ Mediana [ORb (95% CI)]	p-Valuec
Lifetime average concentration
DMA%		1.21 (1.10, 1.35)		1.03 (0.92, 1.15)		0.017
MA%		1.04 (0.94, 1.17)		1.21 (1.09, 1.35)		0.032
Peak daily As dose rate
DMA%		1.14 (1.06, 1.23)		1.05 (0.96, 1.15)		0.098
MA%		1.05 (0.97, 1.15)		1.15 (1.06, 1.23)		0.095
Cumulative As dose
DMA%		1.11 (1.01, 1.22)		0.99 (0.88, 1.12)		0.119
MA%		1.02 (0.91, 1.14)		1.10 (1.00, 1.22)		0.222
Relative risks of BCC were estimated as ORs for unit changes in exposure: a 10 μg/L increase in lifetime average iAs concentration, a 10-μg/day increase in peak iAs daily dose rate, or an increase in cumulative iAs dose derived from 50 years of drinking 1.5 L water/day containing 10 μg/L iAs. aMedian DMA%, 76.6%; median MA%, 15.8%. bThese ORs are stratum specific because they estimate effect of iAs on cancer as a linear effect, separately by level of metabolite, for both DMA% and MA%, and controlled for potential confounders county, age, sex, education, skin response to 1-hr midday sun, and skin complexion. cp-Values for multiplicative interaction terms between dichotomous variables for DMA% or MA% and continuous variables for iAs exposure indexes (Wald test).