a nested case - control study was designed to evaluate whether a nearly twofold excess of kidney cancer among workers at a refinery / petrochemical plant was associated with cumulative exposure to c2-c5 saturated , c2-c5 unsaturated , c6-c10 aliphatic saturated , c6-c10 aliphatic unsaturated , and c6-c10 aromatic process streams . 
 nonoccupational risk factors were body mass index ( bmi ) , blood pressure ( both measured at about age 28 ) , and smoking . 
 there was no significant association with cumulative exposure or tenure as estimated by conditional logistic regression and adjusted for nonoccupational risk factors . 
 categorical analysis showed increased odds ratios only in the second ( low ) and fourth ( high ) quartiles compared to the first quartile reference group of lowest exposed workers , and a three - quarter - fold increased odds ratio for > 32 years ' tenure compared to the < 25-year reference group . 
 the number of cases was small with wide confidence intervals around estimate of risk , so the possibility of an exposure - response trend can not be ruled out . 
 multivariate analysis identified overweight ( high bmi ; p < 0.01 ) as the most important risk factor in this data set , followed by tenure and increased blood pressure . 
 there was a weak association with current smoking , but not with pack - years smoked . 
 the risk of kidney cancer for a nonsmoker with normal blood pressure but 25% overweight was increased about 2.6-fold ( 95% ci = 1.2 - 5.4 ) . 
 the risk of kidney cancer for a nonsmoker of normal weight with high blood pressure ( e.g. , 150/110 ) , was increased about 4.5 ( 95% ci , 0.8 - 26).imagesfigure 1.figure 2.figure 3 .