GSTM1andCYP1A1Polymorphisms, Tobacco, Air Pollution, and Lung Cancer: A Study in Rural Thailand

Abstract

Objectives: The Lampang Province is situated in the northern region of Thailand. Incidence rates of lung cancer are high for Asian standards, particularly in women. This study was conducted to quantify the risk of lung cancer associated with exposures prevalent in the area and to investigate possible interactions with genetic susceptibility. The presence of several large open-cast coal mines from 1955 close to electricity-generating plants was a particular focus of concern. Methods: Two-hundred and eleven cases of primary lung cancers diagnosed in 1993 to 1995 and residents in the province were recruited at the Lampang Provincial Hospital (main referral center for treatment of the disease). Two sets of controls, frequency-matched to the cases by sex and age, were recruited (a) from the resident population (202 interviewed) and (b) from patients admitted to the hospital for diseases predominantly unrelated to tobacco smoking (211 interviewed). Sociodemographic information, complete residential history, and characteristics of the household (place of cooking, cooking fuel, and heating fuels), occupational history, and history of tobacco smoking were obtained by interview. Cases and controls (f50% of the populationbased series) provided a blood sample. A point source air pollution exposure index was calculated for each village/ township reported in residential histories based on the linear distance from the Mae Moh Center (the area of the electricity-generating plants), the year-specific gaseous (SO 2 and NO 2 ) or total suspended particulate emissions from the Mae Moh Power Plant, and the percentage of wind from the center. Odds ratios (OR) for the disease associated with categorical variables were estimated within unconditional logistic regression. Extraction of genomic DNA and genotyping of variants in CYP1A1 and GSTM1 were conducted to assess the extent of modification of risk by these genes that are involved in the metabolism of polycyclic aromatic hydrocarbons, a common component of the exposures. Results: Overall, there was no evidence of relevant differences in the socioeconomic level of the three groups. The two control sets were similar with respect to lifelong tobacco habit and were subsequently pooled in analyses. Neversmokers were 7% of men and 33% of women. Smoking of local traditional products unfiltered and high in tar content is a common habit in the rural female population. ORs associated with smoking increased with duration of the habit and average daily amount, being 4.9 [95% confidence interval (95% CI), 2.5-9.7] for smokers of z7 cigarettes/d and 3.3 (95% CI, 1.7-6.2) for duration of 41 years or longer compared with nonsmokers. Smoking of local products was associated with an independent OR of 3.1 (95% CI, 1.7-5.6) adjusted for lifelong cumulative amount of tobacco smoked. Although most smokers had the habit for at least 16 years, the daily consumption was low compared with Western standards. Other potential sources of exposure to lung carcinogens (emission from the power-generating pla...

GST genotypes and lung cancer susceptibility in Asian populations with indoor air pollution exposures: A meta-analysis

“…The papers were then reviewed to identify casecontrol studies in Asian populations. A total of 11 case-control studies [36][37][38][39][40][41][42][43][44][45][46] were found. Five studies [36][37][38][39][40] were excluded because there was no exposure assessment and no evidence provided in the study that indoor air pollution from any source made an important contribution to lung cancer.…”

“…Five studies [36][37][38][39][40] were excluded because there was no exposure assessment and no evidence provided in the study that indoor air pollution from any source made an important contribution to lung cancer. The remaining 6 studies [41][42][43][44][45][46] satisfied all inclusion criteria, and data related to study design, geographic location, population setting, case selection, control selection, genotyping method, Hardy-Weinberg equilibrium, type of exposure, exposure assessment, smoking, and number of genotyped cases and controls were extracted.…”

“…Overall, one study utilized a quantitative exposure assessment [41], one a qualitative exposure assessment [42], and the presence of indoor air pollution was determined for four studies [43][44][45][46]. Lan et al's [41] study was in Xuan Wei, where more than 95% of the population was exposed to coal and a substantial portion of lung cancer has been attributed to indoor coal use [14;47].…”

“…Although formal risk estimates have not been published for coal use and lung cancer in these two studies, it is highly likely that this exposure is associated with risk of lung cancer [17]. Furthermore, the primary source of fuel for household use in Thailand up to 1-year before Pisani et al's [42] study began was wood and charcoal [52]. Finally, the primary fuel sources in Hong Kong up until recently were kerosene and liquid petroleum gas [53].…”

“…Since combustion from these fuel sources is not known to be associated with lung cancer, while an excess of lung cancer risk has been attributed to cooking oil fume exposure in Chan-Yeung et al's [44] and other study populations in Hong Kong [54;55], the primary exposure for Chan-Yeung et al's [44] Hong Kong study population was classified as cooking oil fumes. In conclusion, the four studies [41;43;45;46] carried out in mainland China were classified as having primarily coal exposure, the study in Thailand [42] was classified as wood and charcoal exposure, and the study in Hong Kong [44] was classified as cooking oil fume exposure.…”