# Indoor Air Pollution Increases the Risk of Lung Cancer
## 4 Discussion
analyzed fumes generated from cooking oils in Taiwan and identified the PAHs dibenz[a,h]anthracene, benz[a]anthracene, and benzo[a]pyrene [22]. [PERSON] et al. compared the incidence of lung cancer between Chinese food chefs and non-Chinese food chefs and concluded that Chinese food chefs, particularly female chefs, had an increased risk of lung cancer [28]. [PERSON] et al. conducted an engineering intervention study to reduce cooking oil fumes in Chinese restaurants in Taiwan. After the installation of a dividing curtain, the oxidative stress biomarkers urinary 8-hydroxy-2'-deoxyguanosine and malondialdehydedehyde decreased in cooks [29]. In Singapore, [PERSON] et al. conducted a study to quantify carcinogen and toxicant biomarkers in Chinese women who reported regularly doing home cooking compared with women randomly selected from the Singapore Chinese Health Study as controls. The results showed increased exposure to the volatile acrolein, crotonaldehyde, and benzene in Chinese women who regularly cook [30]. We recommend further research into the role of volatile compounds produced during high-temperature cooking of oils as the cause of lung cancer. To prevent hazards from Chinese cooking habits, we suggest that Chinese families improve ventilation while cooking. Indoor incense burning is a tradition in Chinese culture that shows respect to ancestors. Incense burning is a daily practice. In the morning and afternoon, incense sticks are burned in an incense burner for approximately half an hour. An incense stick is composed of 21% (by weight) herbal and wood powder, 35% fragrance material, 11% adhesive powder, and 33% bamboo stick. Incense smoke (fumes) contains PM, gas byproducts, and many organic compounds. On average, incense burning produces particulates at concentrations higher than 45 mg/g compared to 10 mg/g for cigarettes. The gas products from burning incense include CO, CO\({}_{2}\), NO\({}_{2}\), SO\({}_{2}\), benzene, toluene, xylenes, aldehydes, and PAHs [6]. [PERSON] et al. measured the total PAHs from incense smoke, and the concentration of PAHs was 147 (\(\pm\)20.6) ng/m\({}^{3}\)[31]. The current study showed that incense burning increased the risk of lung adenocarcinoma. However, our results are different from the findings among Chinese females in Singapore. [PERSON] et al. conducted a case-control study in Singapore in Chinese females with primary lung cancer and controls. The results showed that the OR of smokers with daily incense or mosquito coil exposure versus nonsmokers without daily exposure was 4.61 (95% CI, 3.41-6.24). However, daily exposure to incense or mosquito coils was not associated with lung cancer among nonsmokers (OR = 0.91; 95% CI, 0.72-1.16), suggesting that smoking played an important role [32]. Another study using the same population-based cohort from Singapore reported that the relative risk of squamous cell carcinomas in the entire respiratory tract among long-term incense users was 1.8 (95% CI, 1.2-2.6; \(p\) = 0.004) [33]. Even after excluding the effects of cigarette smoking, our study showed that indoor incense burning increased the risk of lung adenocarcinoma. Burning incense produces numerous organic compounds and metals [34; 35; 36; 37]. A recent study found that simultaneous exposure to PAHs and metals had a synergistic effect that increased oxidative damage in coke oven workers [38]. Oxidative stress plays an essential role in the pathogenesis of lung cancer, as it increases the generation of reactive oxygen species (ROS) that cause DNA damage and thus promote lung cancer [39]. We suggest further research to analyze PAHs and heavy metals in Chinese women with lung cancer to clarify the interaction effect. The occupational hazards of burning incense have been observed in temple workers due to high concentrations and long exposure time. In Thailand, [PERSON] et al.