Occupational exposure to wood, formaldehyde, and solvents and risk of nasopharyngeal carcinoma

Our objective was to evaluate the link between occupational exposures to wo od dust, formaldehyde, and solvents and the development of nasopharyngeal c arcinoma (NPC). A case-control study was conducted among 375 newly diagnose d cases of NPC in Taipei, Taiwan, and 325 community controls matched to cas es on sex, age, and geographical residence (99 and 87% response rates, resp ectively). Most cases (> 90%) were diagnosed with WHO Types 2 or 3 (nonkera tinizing and undifferentiated carcinomas), whereas the remaining cases were diagnosed with WHO Type I (squamous cell carcinomas). A complete occupatio nal history was obtained via a personal interview and blindly assessed by a n industrial hygienist for intensity and probability of exposure to wood du st, formaldehyde, and solvents. Information on socio-demographic characteri stics, cigarette smoking, dietary consumption of nitrosamines, and other po tential confounding factors was obtained via a personal interview. Blood sp ecimens were tested for human leukocyte antigen class I/II genotypes, polym orphisms in cytochrome P450 2E1 genotype, and various anti-EBV antibodies k nown to be associated with NPC. Analysis was performed using logistic regre ssion; relative risk (RR) estimates and 95% confidence intervals (CI) were calculated. Individuals exposed to wood dust had an adjusted RR of 1.7 (95% Cl = 1.0-3.0). Those exposed to wood dust for > 10 years had an adjusted R R of 2.4 (95% CI = 1-1-5-0; p(trend) = 0.02). Risk was strongest for those first exposed before the age of 25 years and those seropositive to EBV. Ind ividuals exposed to formaldehyde were at a more modest and nonsignificant i ncreased risk of NPC (RR = 1.4; 95% CI = 0.93-2.2). Those exposed to formal dehyde for > 10 years had an adjusted RR of 1.6 (95% Cl = 0.91-2.9). The as sociation between formaldehyde and NPC was stronger in analyses restricted to EBV seropositive individuals (RR = 2.7; 95% CI = 1.2-5.9). However, no d ose response was observed with increasing duration or cumulative use. No as sociation was observed between solvent exposure and NPC (RR = 1.2; 95% CI = 0.86-1.7). Occupational exposure to wood dust is likely to be involved in the development of NPC, a finding that is consistent with the known link be tween wood exposure and nasal adenocarcinomas. Formaldehyde exposure is les s clearly linked to NPC, whereas exposure to solvents is unlikely to be inv olved in NPC pathogenesis.