In addition, we identified 6 systematic reviews on active smoking: one on asthma in women [24], one on gene-environment interaction with Glutathione-S-Transferase genes [17], one on marijuana smoking [25], one on the effects of smoke-free legislation [26], one evidence-based guideline on occupational asthma [27], and one on risk and protective factors [5]. This evidence concerns the gene HPGDS and asthma.