The long-term health consequences of ETS exposure have been established over the past two decades. Consistent epidemiologic evidence links ETS exposure with serious chronic health effects, including lung cancer and cardiovascular disease [1, 48, 49]. In this article, the evidence suggests a causal relationship between ETS exposure and new-onset asthma and asthma exacerbation among adults. Despite the growing knowledge of ETS-related health effects, smoking is still permitted in many public locations and workplaces [50, 51]. Because asthma is a visible condition among the general public, the evidence that links ETS exposure with adverse asthma health outcomes should provide policymakers with additional impetus for regulating public smoking and creating smoke-free public environments.