Lung cancer, tobacco, and environmental factors in the African population of the Northern Province, South Africa

Our plain-English summary of Lung cancer, tobacco, and environmental factors in the African population of the Northern Province, South Africa, by O. Mzileni, F. Sitas, K. Steyn, et al (Tobacco Control, 1999).

The study

• Authors: O. Mzileni, F. Sitas, K. Steyn, H. Carrara, P. Bekker
• Journal: Tobacco Control
• Published: 1999;8(4):398-401
• Cited by: 16 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Design: Case-control study among incident African patients with cancer. Questionnaire assessment of exposure to tobacco, occupation, and place of birth.

Setting: Northern Province, South Africa.

Subjects: Between 1993 and 1995, 288 men and 60 women with lung cancer and 183 male and 197 female controls (consisting of patients newly diagnosed with cancers other than those known to be associated with smoking) were interviewed. Unmatched, unconditional logistic regression was used to calculate odds ratios (ORs) and 95% confidence intervals (95% CIs) of developing lung cancer in relation to a number of variables.

Main Outcome Measure: Risk of developing lung cancer related to exposure to tobacco, indoor pollution, dusty work environment, and residential exposure to asbestos.

Results: There was a significant increase in the risk of developing lung cancer through smoking. In men, the ORs were 2.2 (95% CI = 1.0 to 4. 6) in ex-smokers, 9.8 (95% CI = 5.9 to 16.4) in light smokers (0-14 g/day), and 12.0 (95% CI = 6.5 to 22.3) in heavy smokers. In women, the ORs were 5.8 (95% CI = 1.3 to 25.8) in ex-smokers and 5.5 (95% CI = 2.6 to 11.3) in current smokers. Work in a dusty industry showed an elevated risk (OR = 3.2, 95% CI = 1.8 to 5.8) for lung cancer only in men. Male residents of areas where asbestos was shipped for distribution (termed moderately polluted asbestos areas) had a 2.5-fold increase (95% CI = 1.0 to 4.4) in the risk (OR) of developing lung cancer, and residents of areas where asbestos was mined (termed heavily polluted asbestos areas) had a 2.8-fold increase in risk (95% CI = 0.7 to 10.4). Female residents of heavily polluted asbestos areas showed elevated risks of 5.4 (95% CI = 1.3 to 22.5) of developing lung cancer.

Conclusion: The data suggest that tobacco smoking is the most important risk factor for the development of lung cancer in this setting. Risks for lung cancer are reminiscent of those observed in Western countries in the 1960s and 1970s. However, environmental exposure to asbestos, a dusty occupation (in men), and perhaps indoor air pollution may also contribute to the development of lung cancer in this province.

In plain English

This case-control study ran from 1993 to 1995 at Garankuwa hospital in South Africa's Northern Province. It compared 288 men and 60 women with lung cancer with 183 men and 197 women newly diagnosed with cancers believed unrelated to smoking. An interviewer asked about smoking, main occupation, home use of wood or coal, place of birth and current residence. Postal codes were used to classify areas as heavy asbestos (where mining took place), moderate asbestos (towns where raw asbestos was moved for shipping) or none. Smoking was linked to higher odds of lung cancer. The odds ratio was 12.0 (95% CI 6.5 to 22.3) in men who smoked heavily and 5.5 (2.6 to 11.3) in women who currently smoked. Men who had worked in dusty industries had an odds ratio of 3.2 (1.8 to 5.8). Men living in moderately polluted areas had an odds ratio of 2.1 (1.0 to 4.4), and women living in heavily polluted areas 5.4 (1.3 to 22.5). The authors concluded that environmental asbestos exposure, dusty work (in men) and perhaps indoor air pollution may also contribute to lung cancer. They noted that their asbestos categories were crude.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Hospital-based case-control study, with patients who had other cancers as controls; analysed with unconditional unmatched logistic regression
• Who was studied: African patients at the main cancer referral hospital of the Northern Province, South Africa, 1993 to 1995: 288 men and 60 women with newly diagnosed lung cancer (cases), and 183 men and 197 women newly diagnosed with cancers believed unrelated to tobacco, mainly prostate, liver, breast, colorectal and blood cancers (controls)
• Exposure: Smoking, work in potentially dusty industries, home use of wood or coal, and residential asbestos exposure. Asbestos exposure was assigned from the postal codes of place of birth and current residence: heavy (mining areas), moderate (towns where raw asbestos was moved for shipping) or none. Subjects were not asked directly whether they worked with asbestos.
• Main results:
  • Men, compared with never-smokers: odds ratio 2.2 (95% CI 1.0 to 4.6) in ex-smokers, 9.8 (5.9 to 16.4) in light smokers and 12.0 (6.5 to 22.3) in heavy smokers
  • Women, compared with never-smokers: odds ratio 5.8 (95% CI 1.3 to 25.8) in ex-smokers and 5.5 (2.6 to 11.3) in current smokers
  • Work in a dusty industry: odds ratio 3.2 (95% CI 1.8 to 5.8) in men. In women the odds ratio was 0.5 (0.3 to 1.1).
  • Men by current residence: odds ratio 2.1 (95% CI 1.0 to 4.4) in moderately asbestos-polluted areas, which the authors called significant, and 2.8 (0.7 to 10.4) in heavily polluted areas
  • Men by place of birth: odds ratio 2.9 (95% CI 1.2 to 6.7) for those born in moderately polluted asbestos areas and 3.1 (0.4 to 21.4) for those born in heavily polluted areas
  • Women currently living in heavily asbestos-polluted areas: odds ratio 5.4 (95% CI 1.3 to 22.5)
  • Men and women combined, moderate and heavy areas together compared with none: odds ratio 2.1 (95% CI 1.3 to 3.8) for current residents of asbestos-polluted areas and 2.8 (1.5 to 5.4) for people born in such areas
  • The lung cancer risk linked to smoking did not change significantly between people born in asbestos-contaminated areas and people born elsewhere
  • Home use of wood or coal was not statistically significant in men (odds ratio 1.9, 95% CI 0.9 to 3.3) or in women (1.4, 0.6 to 3.2) analysed separately
  • With men and women combined, home use of wood or coal was significantly associated with lung cancer (RR 2.0, 95% CI 1.1 to 3.6)
• The authors' conclusion: The authors concluded that, alongside tobacco smoking, environmental exposure to asbestos, a dusty occupation (in men) and perhaps indoor air pollution may also contribute to lung cancer in the province
• Limitations the authors state:
  • The asbestos exposure categories were crude (for example, sharing a postal code with a mine), and place of birth needs to be classified more accurately
  • Sparse data among women meant that light and heavy smokers, and moderate and heavy asbestos exposure at birth, had to be combined
  • Some participants rounded their age to the nearest decade

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer.

Medical terms in this study, explained in our Lexicon: Lung Cancer, Case-Control Study, Odds Ratio, confidence interval, Environmental Exposure.

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