Occupational asphalt is not associated with head and neck cancer

Background: Epidemiologic studies that evaluate the relationship between occupational asphalt exposure and head and neck cancer have had a limited ability to control for known risk factors such as smoking, alcohol and human papillomavirus (HPV). Aims: To better elucidate this relationship by including known risk factors in a large case-control study of head and neck squamous cell carcinoma (HNSCC) from the greater Boston area. Methods: We analysed the relationship between occupational asphalt exposure and HNSCC among men in the Greater Boston area of Massachusetts. Analyses were conducted using unconditional multivariable logistic regression, performed with adjustments for age, race, education, smoking, alcohol consumption and HPV serology. Results: There were 753 cases and 913 controls. No associations between HNSCC and occupational asphalt exposure (neither among ever-exposed nor by occupational duration) were observed for exposures in any occupation or those restricted to the construction industry. We also observed no associations in subgroup analyses of never-smokers and ever-smokers. Adjusting for known risk factors further reduced the estimated effect of asphalt exposure on HNSCC risk. Conclusions: We found no evidence for an association between occupational asphalt exposure and HNSCC. The null findings from this well-controlled analysis could suggest that the risk estimates stemming from occupational cohort studies may be overestimated due to uncontrolled confounding and enhance the literature available for weighing cancer risk from occupational exposure to bitumen.