Exposure to PCB180 levels in plasma and carpet dust and NHL risk, stratified by genotype. Exposure and NHL risk was stratified by genotype for 3 single nucleotide polymorphisms: IL16 3′-UTR, Ex22+871A>G (A), IL8 T−251A (B), and IL10 A−1082G (C). One asterisk (*) denotes significant association (P < .05) between exposure and NHL risk for that genotype. Two asterisks (**) denote highly significant association (P < .01) between exposure and NHL risk for that genotype. P value accompanies x-axis label if there was a significant interaction (P for interaction < .05) between genotype and exposure; y-axis is β coefficient from logistic regression.