Household air pollution (HAP) attributed to wood use is a potential environmental risk factor for lung cancer, to which ~2.5 billion people worldwide (including >15 million in the US) are exposed. Known lung cancer risk factors (i.e., environmental tobacco smoke (ETS), outdoor air pollution (OAP), family history) do not fully account for the disease burden. To reach robust conclusions about biomass's pulmonary carcinogenicity and the lung cancer deaths attributed to HAP while accounting for confounding exposures, prospective studies of individuals experiencing a variety of exposure levels of HAP, ETS, and other suspected lung carcinogens are needed. We will leverage our global consortium of prospective studies (HAPCO: Household Air Pollution Cohorts), which is a pooled resource of >550,000 subjects, to for the first time accurately quantify the relative risk of lung cancer mortality associated with wood use. Further, we will estimate time-dependent population-attributable fraction (PAF) function for lung cancer mortality, which will measure the potential reduction in lung cancer mortality if HAP is eliminated or reduced while adjusting for known and suspected lung carcinogens (i.e., ETS, OAP). Our robust harmonization of HAP data will also provide the unique opportunity to determine the relative and absolute risks associated with HAP exposures for cancers other than lung cancer, which was recently highlighted by an expert panel convened by multiple US Federal Agencies.