Chinese food cooking and lung cancer in women nonsmokers

Interaction between environmental tobacco smoke and arsenic methylation ability on the risk of bladder cancer

OBJECTIVE

Arsenic exposure and environmental tobacco smoke (ETS) have been suspected to be associated with bladder cancer risk. We hypothesize that interaction between ETS and the ability to methylate arsenic, a detoxification pathway, modifies the risk of bladder cancer.

METHODS

From January 1996 to December 1999, we identified 41 newly diagnosed bladder cancer patients and 202 fracture and cataract patients at the National Cheng-Kung University (NCKU) Medical Center. The levels of urinary arsenic species [As(III), As(V), MMA(V), and DMA(V)] were determined in all subjects.

RESULTS

We found significant interaction between ETS and secondary methylation index (SMI) on the risk of bladder cancer (p=0.02). Among non-smokers with a high primary methylation index (PMI), the risk of bladder cancer was lower in subjects exposed to ETS (OR, 0.37; 95% CI, 0.14-0.96) than in subjects without exposure to ETS. Among non-smokers without ETS, the risk of bladder cancer was 4.7 times higher in subjects with a low SMI (95% CI, 1.30-16.81) than in subjects with a high SMI.

CONCLUSIONS

Ability to methylate arsenic plays an important role in reducing the risk of bladder cancer attributable to the continuation of arsenic exposure from drinking water and from ETS exposure.

Mutations of the epidermal growth factor receptor gene in lung cancer: biological and clinical implications

Recently it has been reported that mutations in the tyrosine kinase domain of the epidermal growth factor receptor(EGFR) gene occur in a subset of patients with lung cancer showing a dramatic response to EGFR tyrosine kinase inhibitors. To gain further insights in the role of EGFR in lung carcinogenesis, we sequenced exons 18-21 of the tyrosine kinase domain using total RNA extracted from unselected 277 patients with lung cancer who underwent surgical resection and correlated the results with clinical and pathologic features. EGFR mutations were present in 111 patients (40%). Fifty-two were in-frame deletions around codons 746-750 in exon 19, 54 were point mutations including 49 at codon 858 in exon 21 and 4 at codon 719 in exon 18, and 5 were duplications/insertions mainly in exon 20. They were significantly more frequent in female (P < 0.001), adenocarcinomas (P = 0.0013), and in never-smokers (P < 0.001). Multivariate analysis suggested EGFR mutations were independently associated with adenocarcinoma histology (P = 0.0012) and smoking status (P < 0.001), but not with female gender (P = 0.9917). In adenocarcinomas, EGFR mutations were more frequent in well to moderately differentiated tumors (P < 0.001) but were independent of patient age, disease stages, or patient survival. KRAS and TP53 mutations were present in 13 and 41%, respectively. EGFR mutations never occurred in tumors with KRAS mutations, whereas EGFR mutations were independent of TP53 mutations. EGFR mutations define a distinct subset of pulmonary adenocarcinoma without KRAS mutations, which is not caused by tobacco carcinogens.

NAT2 fast acetylator genotype is associated with an increased risk of lung cancer among never-smoking women in Taiwan

The correlation between cooking oil fumes, containing relatively higher amounts of heterocyclic amines, and female lung cancer has been revealed. The association of genetic polymorphisms of CYP1A2 and NAT2, two major enzymes responsible for the metabolism of heterocyclic amines, with lung cancer has been investigated with inconclusive results. In this study targeted on never-smoking population with 162 lung cancer patients and 208 non-cancer controls, while the distributions of CYP1A2 phenotypes in lung cancer patients were comparable to that in controls, NAT2 fast acetylators had an OR of 2.44 (95% CI 1.40-4.23, P=0.002) and 2.56 (95% CI 1.37-4.80, P=0.003) for lung cancer in overall and female cases, respectively, but not in males. These results suggested never-smoking females with NAT2 fast acetylator were more prone to lung cancer and reflected the possibility that exposure to heterocyclic amines may contribute to the female lung cancer development in Taiwan.

Lung adenocarcinoma and human papillomavirus infection

Over the past three decades, the incidence of lung adenocarcinoma has increased worldwide. Most individuals with lung adenocarcinoma (especially women) are nonsmokers. Reported risk factors for the development of lung adenocarcinoma include cigarette smoking; exposure to cooking fumes, air pollution, second-hand smoke, asbestos, and radon; nutritional status; genetic susceptibility; immunologic dysfunction; tuberculosis infection; and asthma. Human papillomavirus (HPV) infection is a known risk factor for the development of squamous cell carcinoma (SCC), but it has not been thoroughly assessed as a potential risk factor for the development of pulmonary adenocarcinoma. More than 50% of people are infected with HPV during their lifetimes, either via intrauterine or postnatal infection. Recent studies involving Taiwanese patients have demonstrated a possible association between HPV infection and the risk of developing pulmonary adenocarcinoma. HPV transmission pathways have not yet been conclusively identified. The observation of certain types of HPV in association with cervical and oral SCC raises the possibility of sexual transmission of HPV from the cervix to the oral cavity, with subsequent transmission to the larynx and then to the lung. HPV infection and metaplasia in lung tissue may increase an individual's susceptibility to the tumorigenesis of pulmonary adenocarcinoma. Further epidemiologic and pathologic investigations will be necessary to establish a causal relation.

Cancer aggregation and complex segregation analysis of families with female non-smoking lung cancer probands in Taiwan

Previous studies have found that having a first-degree blood relative with lung cancer was a possible predictor of lung cancer risk, but some studies have indicated that the association is non-significant or only significant for a subset of the studied population. To determine the familial aggregation and whether there is any evidence for a gene controlling the susceptibility to developing lung cancer in female non-smokers, multiple logistic regression methods for estimating covariate effects and maximum likelihood segregation analyses were performed using data from 216 female non-smoking lung cancer probands (2328 individuals) in a population-based case-control study. Having a family history of lung cancer was found to be a significant predictor of lung cancer for non-smoking females (Adjusted Odds Ratio (OR)=5.7, 95% Confidence Interval (CI)=1.9-16.9). Having a female relative with lung cancer (adjusted OR=14.4, 95% CI=2.7-75.5) was more strongly associated with the lung cancer risk than was having a male relative with lung cancer. This association was stronger for probands aged less than 60 years at onset (adjusted OR=11.2, 95% CI=2.2-56.9). All of the Mendelian models fitted the data significantly better than the sporadic (no major type) model or the environmental model (P<0.00l). The Mendelian codominant models provided the best fit of the data for the early onset probands and showed a stronger effect for a major susceptibility locus for non-smoking lung cancer probands. The results of this study provide evidence that a rare autosomal codominant gene may influence the risk lung cancer in non-smoker and is responsible for the familial aggregation observed in non-smoking lung cancer patients.

Time trends of female lung cancer in Hong Kong: Age, period and birth cohort analysis

The study was conducted to estimate the effects of age, year of diagnosis (period) and year of birth (cohort) on the time trend of female lung cancer incidence between 1976 and 2000 in Hong Kong. Data were obtained from a population-based cancer registry and the Census and Statistics Department. Using the Hong Kong general population of 1990 as the reference, age-adjusted incidence rates were computed by using direct standardization. We also analyzed secular trends in 2 consecutive periods, 1976-1990 and 1991-2000, using a Poisson regression model to estimate the annual percentage change in incidence rate. Age, period and cohort effects were assessed employing the method proposed by Clayton and Schifflers with 3 Poisson regression models fitted separately for age alone, age and period, and age and cohort. The age-adjusted incidence rate increased steadily up to 1990, when a peak of 40.1 per 100,000 was reached. Thereafter, a downward trend was observed. The overall annual increase was 4.2% during the period 1976-1990 with the fastest increase observed in women aged 80-84 years. An overall decrease of 2.3% was seen in the period 1991-2000, with the greatest reduction occurring in the 35-39 age group. After the adjustment for age, significant period and cohort effects on the time trend of incidence were observed. The age-cohort model provided a better description of the data than the age-period model. The risk of successive 5-year birth cohorts increased from 1896 to 1925 and then decreased. The time trend of lung cancer incidence of Hong Kong female in 1976-2000 had a marked birth cohort effect. Our results imply that major sources of exposure, which carry an increased risk of lung cancer for Hong Kong women, have been becoming less common in recent decades. Domestic air pollution, poor nutrition and tobacco smoking might have played important roles in the change of risks in successive generations and provide guidance for future interventions.

Environmental exposure to cooking oil fumes and cervical intraepithelial neoplasm

The fumes from cooking oil, similar to cigarette smoke, contain numerous carcinogens such as polycyclic aromatic hydrocarbons, aromatic amines, nitro-polycyclic aromatic hydrocarbons, etc. In this study, we examined the association between exposure to cooking oil fumes and the risk of cervical intraepithelial neoplasm. The study population in this nested case-control study consisted of women above the age of 19 years living in Chia-Yi County, located in the southwestern Taiwan, who had received pap smear screening between October, 1999, and December, 2000 (n=32,466). The potential cases were women having lesions greater than cervical intraepithelium neoplasm II (> or =CIN2) reconfirmed by cervical biopsy (n=116). The potential controls (case: control=1:2) were age-matched (+/-2 years) and residence-matched women who had normal pap smears within 6 months of the cases. In total, 100 cases and 197 controls were completely interviewed by public health nurses about cooking methods, ventilation, and other potential risk factors. Women who cooked at home in a kitchen (n=269) without the presence of a fume extractor at least once a week between the ages of 20 and 40 had a 2.29 times higher risk [95% confidence interval (CI)=1.08-4.87] of developing cervical intraepithelial neoplasm than those who did not cook once a week in such a kitchen during the same age span, after adjusting for other potential confounders. This finding was further strengthened by the finding that women who did not use the fume extractors had a 2.47 times higher risk (95% CI=1.15-5.32) of developing cervical intraepithelial neoplasm than women who cooked in kitchens with fume extractors that were always switched on while cooking. We also found a joint protective effect of fume extractor use among women older than 40 years (n=202) if they used the extractors during both age spans of their lives, ages 20-40 and >40 years. Comparing our findings on women more than 40 years old who used fume extractors during both periods, we found a 2.05-fold greater risk (95% CI=0.86-4.86) for those who used exhaust fans during only one of the two age spans and a 3.46-fold greater risk in those who had not used an exhaust fan for either period (95% CI=1.08-11.10) (trend test, P=0.02). While exposure to cooking oil fumes may cause cervical intraepithelial neoplasm, women can be protected from this risk by always cooking in kitchens equipped with fume extractors and by keeping them on while cooking.

Effect of frying-meat emission particulate on 17beta-estradiol 2- and 4-hydroxylation in human lung adenocarcinoma CL5 cells

The effect of airborne frying-meat emission particulate (FMEP) on metabolism of 17beta-estradiol (E(2)) to potentially toxic catechol estrogens 2- and 4-hydroxyestradiol (2- and 4-OH-E(2)) was determined using human lung adenocarcinoma CL5 cells treated with organic extracts of beef FMEP. E(2) was incubated with microsomes prepared from untreated CL5 cells or cells treated with 200 microg/ml FMEP extract for 6 h. E(2) metabolites formed were analyzed by high-performance liquid chromatography (HPLC). The results revealed that treatment with FMEP produced three-and twofold increases of 2- and 4-hydroxylation of E(2), respectively. Monooxygenase activity and immunoblot analyses showed that FMEP markedly induced microsomal 7-ethoxyresorufin O-deethylase (EROD) activity and cytochrome P-450 (CYP) IAI and CYPIBI protein levels. Similar increases in E(2) hydroxylation, EROD activity, and CYP protein levels were observed with HepG2 human hepatoma and MCF-7 human breast cancer cells treated with FMEP or 1 microM dibenz[a,h]anthracene. Cotreatment of CL5 cells with FMEP extract and 2 microM alpha-naphthoflavone, an arylhydrocarbon receptor antagonist, blocked the inductive effects of FMEP on E(2) hydroxylation and EROD activity. Additions of 0.01, 0.1, or 1 microM alpha-naphthoflavone, a CYP inhibitor, to microsomes produced concentration-dependent decreases in E(2) 2-hydroxylation and EROD activity of CL5 cells induced by dibenz[a,h]anthracene. The present finding demonstrates that FMEP can increase formation of 2-OH-E(2) and 4-OH-E(2) by human lung cells, and induction of CYP1A1 and CYP1B1 is a potential mechanism underlying increased E(2) metabolism. The toxicological significance of FMEP and estrogen interaction warrants further investigation.

A mulher e o cancro do pulmão**Textos referentes à mesa-redonda com o mesmo título organizada pela Comissão de Trabalho de «Pneumologia Oncológica». Coimbra, 13 de Abril de 2002

The epidemiology of lung cancer has changed in the last years in several countries all over the world. In the 19th century, the lung cancer was rare but it incidence increase drastically during the 20th century, and the tendency is to continue in the 20th century. Actually the lung cancer's incidence and mortality are higher in the developed countries, especially in Europe and Unites States of America, with a increasing in the women incidence. These geographic differences and gender differences are related with smoking habits. Women begin to smoke earlier and have more difficulty to stop, because of problems related with obesity; they have more sensibility to the carcinogens and the risk of lung cancer is 1.5 times higher than the men with the same habits. Adenocarcinoma is the more frequent histological type in young people, in the total of the women and in non-smokers. Many factors since tobacco, home and professional pollution, nutritional, associated diseases even genetic and hormonal factors have been investigated to define its influence in development in women lung cancer. It specificity in women with lung cancer is the common problem for the medical people to treat this disease (pathology).The literature about this problem is not clear, and is necessary to advance with many studies in this area with the objective to clarify this important question.

Urinary excretion of 8-hydroxy-2-deoxyguanosine and 1-hydroxypyrene in coke-oven workers

Coke-oven workers (COWs) are occupationally exposed to high concentrations of polycyclic aromatic hydrocarbons (PAH). Urinary 8-hydroxy-2-deoxyguanosine (8-OH-dG) and 1-hydroxypyrene (1-OHP) are biological markers of oxidative DNA damage and PAH metabolism, respectively. We investigated the relationship between urinary 8-OH-dG and 1-OHP in 217 Taiwanese COWs, 55 topside-oven, and 162 sideoven workers. For topside-oven workers, mean 8-OH-dG and 1-OHP concentrations (ng/ml +/- SD) were 13.8 +/- 12.0 and 93.5 +/- 104.4, respectively. These levels were significantly higher than those for sideoven workers: 10.2 +/- 7.9 ng/ml (P = 0.04) and 19.8 +/- 28.6 ng/ml (P < 0.001), respectively. Individual urinary 8-OH-dG concentrations were directly correlated with urinary 1-OHP concentrations: the higher the 1-OHP level, the higher the 8-OH-dG level (Spearman correlation coefficients: r = 0.43, P < 0.0001, n = 217). Multiple regression analysis indicated that a 10-fold increase in 1-OHP was associated with a 1.91-fold increase in 8-OH-dG. Compared to no vitamin intake, intake of at least one multiple vitamin pill per week reduced 8-OH-dG excretion (P = 0.02). Our findings suggest that urinary 1-OHP and 8-OH-dG reflect occupational PAH exposure and oxidative DNA damage in COWs. In addition, multiple vitamins may reduce oxidative stress caused by PAH exposure.

Induction of cytochromes P450 1A1 and 1B1 in human lung adenocarcinoma CL5 cells by frying-meat emission particulate

The effect of airborne frying-meat emission particulate (FMEP) on cytochrome P450 (P450)-dependent monooxygenase was determined using human lung adenocarcinoma cell line CL5 treated with organic extract of FMEP prepared from beef, fish or pork. Treatment with fish FMEP extract caused greater increases of intracellular peroxide production and glutathione content than did beef and pork FMEP extracts. Treatment with 200 microg/ml beef, fish or pork FMEP extract for 6 h increased benzo[a]pyrene hydroxylase, 7-ethoxyresorufin and methoxyresorufin O-dealkylases activities in S9. Immunoblot analysis of S9 proteins from control cells and cells treated with FMEP extracts revealed that the airborne particulates increased proteins immunorelated to CYP1A1 and CYP1B1. Northern blot analysis of total cellular RNA from controls and cells treated with FMEP extracts showed that the cooking by-products increased the levels of CYP1A1 and CYP1B1 mRNA. Treatment with 1 microM dibenzo[a,h]anthracene for 6 h increased monooxygenase activities, CYP1A1 and CYP1B1 protein and mRNA levels in CL5 cells. Beef FMEP extract and dibenzo[a,h]anthracene also induced CYP1A1 and CYP1B1 in human lung carcinoma NCI-H322 cells. The present finding demonstrates that airborne particulates generated during the frying of beef, fish and pork can induce carcinogen-metabolizing CYP1A1 and CYP1B1 in the human lung-derived cell line CL5.

Cooking oil fumes and risk of lung cancer in women in rural Gansu, China

Cooking oil fumes have been suggested to increase the risk of lung cancer in Chinese women by exposing them to mutagenic substances. We investigated the association between lung cancer and locally made rapeseed and linseed oils in a population-based case-control study in Gansu Province, China. Two hundred and thirty-three incident, female lung cancer cases diagnosed from 1994-98 were identified. A control group of 459 women was selected from census lists and were frequency matched on age and prefecture. Interviewers obtained information on cooking practices and cooking oil use. The odds ratio (OR) for lung cancer associated with ever-use of rapeseed oil, alone or in combination with linseed oil, was 1.67 (95% CI 1.0-2.5), compared to use of linseed oil alone. ORs for stir-frying with either linseed or rapeseed oil 15-29, 30 and > or =31 times per month were 1.96,1.73, and 2.24, respectively (trend, P=0.03), relative to a lower frequency of stir-frying. Lung cancer risks also increased with total number of years cooking (trend, P<0.09). Women exposed to cooking fumes from rapeseed oil appeared to be at increased risk of lung cancer, and there was some evidence that fumes from linseed oil may have also contributed to the risk.

Diet, reproductive factors and lung cancer risk among Chinese women in Singapore: evidence for a protective effect of soy in nonsmokers

The factors associated with risk of lung cancer among nonsmokers have not been fully elucidated, but dietary factors have consistently been shown to play a role. Chinese women are unique in having a high incidence of lung cancer despite a low smoking prevalence. This population is also known to have a high intake of soy, a dietary source of phytoestrogens. We conducted a hospital-based case-control study among Singapore Chinese women, comprising 303 cases and 765 age-matched controls, of whom 176 cases and 663 controls were lifetime nonsmokers. Data on demographic background, reproductive factors and dietary intake of fruit, vegetables and soy foods were obtained by in-person interview. We observed an inverse association between intake of total, cruciferous and non-cruciferous vegetables and risk of lung cancer among smokers. Although smokers in the highest tertile of fruit intake also had a lower risk, this was not statistically significant. Higher intake of soy foods significantly reduced risk of lung cancer among lifetime nonsmokers, but not among smokers. When soy isoflavonoid intake in mg/week was computed based on frequency and portion size of intake of eight common local soy foods, the adjusted OR among nonsmokers for the highest tertile compared to the lowest was 0.56, 95% CI 0.37-0.85 (p for trend <0.01). Fruit intake was also significantly associated with reduced lung cancer risk among nonsmokers, but the effect was not significant after adjustment for soy intake. On the other hand, soy intake remained an independent predictor of risk after controlling for fruit intake. Reproductive effects were also primarily confined to lifetime nonsmokers, among whom having 3 or more livebirths (adjusted OR 0.65, 0.44-0.96) and a menstrual cycle length of more than 30 days (OR 0.46, 0.25-0.84) accorded a significantly reduced risk of lung cancer. Place of birth was significantly associated with risk among nonsmokers (OR 2.6, 1.7-3.9 for China-born vs. local born) but not among smokers. When analysis was restricted to nonsmokers with adenocarcinomas, the dietary effects were consistent or enhanced. On stepwise regression, soy intake and cycle length emerged as the independent dietary and reproductive predictors of lung cancer risk in nonsmokers. These findings are consistent with other evidence suggesting an involvement of estrogen-related pathways in lung cancer among non-smoking women.

Cooking oil fume-induced cytokine expression and oxidative stress in human lung epithelial cells

Epidemiological studies have shown an association between exposure to indoor air pollution from Chinese-style cooking and risk of lung cancer among Chinese females. Several toxic substances have been identified in cooking oil fumes (COF) collected from heated rapeseed oil. In this study, we examined the biological effects of COF on CL3 human lung epithelial cells. Exposure to 200 microg/ml COF significantly reduced cell growth within 4 days. In addition, we examined the effect of COF on TGFbeta1, TGFbeta2, IL-6, IL-8, and IFN-gamma gene expressions with the RT-PCR method. We found that TGFbeta1 mRNA levels increased after exposure to 200 microg/ml COF for 24 h. Similarly, exposure to 10 microM benzo[a]pyrene or 100 nM 12-O-tetradecanoylphorbol-13-acetate increased TGFbeta1 mRNA levels at 24 h. The mRNA levels of TGFbeta2, IL-6, IL-8, and IFN-gamma did not increase after treatment with COF, benzo[a]pyrene, or 12-O-tetradecanoylphorbol-13-acetate. COF-induced TGFbeta1 production was confirmed by quantification of TGFbeta1 in conditioned medium with enzyme-linked immunosorbent assay. Exposure to 200 microg/ml COF significantly increased TGFbeta1 secretion in a time-dependent and dose-dependent manner. It has been demonstrated that reactive oxygen intermediates induce TGFbeta1 gene expression. When CL3 cells were exposed to 200 microg/ml COF for 15 min, there was an increase in intracellular peroxide formation with the dichlorofluorescein method. Furthermore, treatment with 200 microg/ml COF for 12 h also significantly induced lipid peroxidation in CL3 cells. Our results show that exposure to COF inhibits cell growth, increases TGFbeta1 secretion, and induces oxidative stress in CL3 lung epithelial cells. This suggests that TGFbeta1 and oxidative stress play a role in the biological effects of COF on lung epithelial cells.

Ultrafine particles and nitrogen oxides generated by gas and electric cooking

OBJECTIVES

To measure the concentrations of particles less than 100 nm diameter and of oxides of nitrogen generated by cooking with gas and electricity, to comment on possible hazards to health in poorly ventilated kitchens.

METHODS

Experiments with gas and electric rings, grills, and ovens were used to compare different cooking procedures. Nitrogen oxides (NO(x)) were measured by a chemiluminescent ML9841A NO(x) analyser. A TSI 3934 scanning mobility particle sizer was used to measure average number concentration and size distribution of aerosols in the size range 10-500 nm.

RESULTS

High concentrations of particles are generated by gas combustion, by frying, and by cooking of fatty foods. Electric rings and grills may also generate particles from their surfaces. In experiments where gas burning was the most important source of particles, most particles were in the size range 15-40 nm. When bacon was fried on the gas or electric rings the particles were of larger diameter, in the size range 50-100 nm. The smaller particles generated during experiments grew in size with time because of coagulation. Substantial concentrations of NO(X) were generated during cooking on gas; four rings for 15 minutes produced 5 minute peaks of about 1000 ppb nitrogen dioxide and about 2000 ppb nitric oxide.

CONCLUSIONS

Cooking in a poorly ventilated kitchen may give rise to potentially toxic concentrations of numbers of particles. Very high concentrations of oxides of nitrogen may also be generated by gas cooking, and with no extraction and poor ventilation, may reach concentrations at which adverse health effects may be expected. Although respiratory effects of exposure to NO(x) might be anticipated, recent epidemiology suggests that cardiac effects cannot be excluded, and further investigation of this is desirable.

Lifetime environmental exposure to tobacco smoke and primary lung cancer of non-smoking Taiwanese women

BACKGROUND

For a female population with a high lung cancer mortality rate, such as Taiwanese women, who smoke relatively rarely, but live in an environment with high male smoking prevalence, the risk and population burden of lung cancer due to environmental tobacco smoke (ETS) are relatively important.

METHODS

An age-matched case-control study was designed to investigate the effects of cumulative environmental exposure to tobacco smoke during childhood and adult life on lung cancer risk among non-smoking women in Taiwan. Information on passive smoking from all possible sources and life periods were obtained from interviews with 268 and 445 lifetime non-smoking cases and controls. Conditional logistic regression and synergism 'S' index were applied to the data to assess the independent and joint effects of passive smoking in different life stages while controlling for possible confounding variables.

RESULTS

Risks of contracting lung cancer among women near-distantly exposed to the highest level of ETS in childhood (>20 smoker-years) and in adult life (>40 smoker-years) were 1.8-fold (95% CI: 1.2-2.9) and 2.2-fold (95% CI: 1.4-3.7) higher than that among women being never exposed to ETS, and the two variables accounted for about 37% of tumours in this non-smoking female population. Children were found to be more susceptible to ETS than adults and such early exposure was found to modify the effect of subsequent tobacco smoke exposure in adult life based on an additive interaction model.

CONCLUSIONS

Environmental tobacco smoke exposure occurring in childhood potentiates the effect of high doses of exposure in adult life in determining the development of lung cancer. Smoking prohibition would be expected to protect about 37% of non-smoking Taiwanese women against lung cancer.