A groundbreaking analysis from the National Institute for Occupational Health (NIOH), affiliated with the University of the Witwatersrand (Wits), has shed light on unexpected links between everyday jobs and elevated lung cancer mortality in South Africa. Published as the inaugural piece in the Public Health Bulletin of South Africa (PHBSA)'s Cancer and Occupation series, the study draws on national mortality data to pinpoint occupations where workers face higher odds of succumbing to this deadly disease.

Lung cancer remains the leading cause of cancer deaths in South Africa, claiming thousands of lives annually. While smoking is the dominant risk factor, contributing to roughly twice as many deaths as non-smoking, this research highlights how workplace exposures compound the danger, even in seemingly low-risk office environments. By adjusting for confounders like age, province, education, and smoking status, the findings reveal a broader spectrum of vulnerability across professions.

🔬 The Lung Cancer Burden in South Africa

South Africa grapples with a heavy toll from lung cancer, which accounted for 17,112 deaths between 2011 and 2015 alone—1.11% of all recorded deaths during that period. Men comprised 71% of victims, with the peak incidence in the 60-64 age group. Provinces like the Western Cape and Northern Cape reported disproportionately high numbers, potentially tied to historical industrial activities and demographics.

Projections from earlier studies suggested a gradual decline in age-adjusted mortality rates among men from 17.1 to 14.1 per 100,000 by 2025, thanks to tobacco control efforts, while rates for women hovered around 7.2. However, occupational factors persist as underrecognized contributors, especially in a nation with extensive mining and construction sectors.

Beyond smoking, environmental and workplace carcinogens play a role. South Africa's gold mines, for instance, expose workers to silica dust, radon progeny, diesel exhaust, and historically asbestos—all known lung carcinogens. Construction sites add silica from cutting materials and diesel fumes, while even administrative roles may involve legacy exposures or lifestyle correlations.

Study Methodology: Unpacking National Data

Led by epidemiologist Dr. Kerry Wilson from NIOH and Wits School of Public Health, the study analyzed Statistics South Africa (Stats SA) vital registry data for 2011-2015. Focusing on working-age adults (15-69 years), researchers used International Classification of Diseases (ICD-10) codes C33-C34 for lung malignancies. Occupations were coded per the South African Standard Classification of Occupations (SASCO).

Proportional Mortality Ratios (PMRs) provided initial signals, followed by adjusted Mortality Odds Ratios (MORs) via logistic regression. Controls included age, sex, province, death year, education, personal smoking (available for 57%), and next-of-kin smoking status. This rigorous approach isolates occupational signals amid confounders.

Limitations acknowledged: smoking data gaps (52.5% missing), reliance on death certificate occupations (main lifetime job), and PMRs indicating association, not causation. Yet, the scale—17,112 cases—offers robust national insights.

High-Risk Occupations for Men

Men in managerial and professional roles topped the list with unexpectedly high MORs. Administrative and commercial managers showed a 2.32-fold increased odds, customer services clerks 2.49, and science/engineering professionals 1.80. Trades like metal/machinery workers (1.51), building trades (1.42), and stationary plant operators (often miners, 1.39) also elevated risks.

• Administrative & commercial managers: MOR 2.32
• Customer services clerks: MOR 2.49
• Science & engineering professionals: MOR 1.80
• Metal, machinery & related trades: MOR 1.51
• Stationary plant & machine operators: MOR 1.39
• Subsistence farmers: MOR 1.44

These findings challenge assumptions, suggesting diesel exhaust in engineering sites or unventilated smoking in offices as culprits.

Surprising Risks for Women in the Workforce

Women exhibited even steeper odds in some categories: administrative managers (5.54), production managers (5.19), science/engineering professionals (3.62), and business associate professionals (3.70). Clerks (general/keyboard: 2.42) and operators (2.04) followed, with metal trades at 1.93.

• Administrative & commercial managers: MOR 5.54
• Production & specialised services managers: MOR 5.19
• Science & engineering professionals: MOR 3.62
• Business & administration associate professionals: MOR 3.70
• Stationary plant & machine operators: MOR 2.04

Higher female MORs may stem from sex-specific exposures or lower baseline smoking rates amplifying occupational effects.

Potential Carcinogens at Play

South Africa's occupational landscape brims with lung hazards. Mining exposes workers to respirable crystalline silica (silicosis precursor), radon daughters in gold mines, diesel particulate matter, and residual asbestos from past use. Construction generates silica dust and welding fumes; manufacturing adds metals and solvents.

Even white-collar surprises: older buildings with asbestos insulation, secondhand smoke pre-bans, or commuting via polluted routes. Stress and shift work may indirectly heighten vulnerability via immune suppression or smoking propensity.

NIOH's longstanding research on miners underscores these risks, with historical asbestos in South African mines linked to excess lung cancers.

Smoking's Overarching Shadow

Smokers faced double the lung cancer mortality of non-smokers, yet data incompleteness tempers precision. South Africa's Tobacco Products Control Amendment Act (1999) and Occupational Health and Safety Act (1993) mandate smoke-free workplaces, but enforcement lags in some sectors.

Prevalence hovers at 23%, fueling the epidemic. The study adjusted where possible, isolating occupational signals, but urges better death certificate documentation.

Regional Hotspots and Demographics

Western Cape bore 37% of cases, Northern Cape elevated per capita—likely mining legacies. Urban-industrial Gauteng and KwaZulu-Natal followed. Black South Africans in mining face compounded risks; women in emerging managerial roles show rising trends.

Policy Implications and Calls for Action

Dr. Wilson stresses: "Occupational cancer needs prevention and compensation." Target inspections in high-MOR jobs, update compensable diseases list, bolster OHS Act enforcement.

Integrate findings into labor policies, expand surveillance. For workers: report exposures, use PPE, quit smoking via health career resources.

Prevention: Empowering Workers and Employers

• Implement ventilation, dust suppression in trades/mining.
• Regular health screenings for high-risk groups (age 50+, smokers, exposures).
• Tobacco cessation programs workplace-wide.
• Training on carcinogen recognition per OHS Act.

Low-dose CT screening pilots for occupations like mining show promise globally; adapt for SA.

Access the full PHBSA study for data tables.

University Research Driving Change

Wits University's School of Public Health, partnering with NIOH, exemplifies higher education's role in safeguarding workers. Dr. Wilson's work builds on decades of miner health surveillance, informing global standards. Aspiring researchers can pursue research positions to advance occupational epidemiology.

Future Outlook: Towards Safer Workplaces

With series expansions on bladder and oesophageal cancers, PHBSA charts a path for proactive intervention. Enhanced data, AI-driven surveillance, and policy reforms promise reductions. Workers: prioritize health checks; employers: invest in safety; academics: continue vital research. Explore professor insights or higher ed careers in public health at AcademicJobs.com.