Cluster Analysis Evaluating PM2.5, Occupation Risk and Mode of Transportation as Surrogates for Air-pollution and the Impact on Lung Cancer Diagnosis and 1-Year Mortality

Document Type : Research Articles


1 Respiratory Unit, Universiti Kebangsaan Malaysia Medical Centre, Faculty of Medicine, University Kebangsaan, Cheras, Malaysia.

2 Department of Clinical Oncology, University Technology MARA, 40450 Shah Alam, Malaysia.

3 School of Environmental and Natural Resource Sciences, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, Bangi, Malaysia.

4 Institute for Environment and Development (Lestari), Universiti Kebangsaan Malaysia, Bangi, Malaysia.


Objective: Epidemiological studies have reported the close relationship between risk for lung cancers and air pollution
in particular, for non-smoking related lung cancers. However, most studies used residential address as proxies which may
not estimate accurately an individual’s air pollution exposure. Therefore, the aim of this study was to identify risk factors
such as occupation and mode of transportation associated with lung cancer diagnosis and death. Methods: Subjects
with lung cancer (n=514) were evaluated both by chart reviews for clinical data and interviews to determine residential
address for ten years, main occupation and main mode of transportation. Annual particulate matter with diameter size
less than 2.5 micrometre (PM2.5) concentration were calculated based on particulate matter with diameter size less than
10 micrometre (PM10) data recorded by Malaysian Department of Environment. Logistic regression analysis, cluster
analysis and the Cox regression analysis were performed to the studied variables. Results: This study concurred with
previous studies that lung adenocarcinoma were diagnosed in predominantly younger, female non-smokers compared
to the other types of lung cancers. Lung adenocarcinoma subjects had annual PM2.5 that was almost twice higher than
squamous cell carcinoma, small cell carcinoma and other histological subtypes (p=0.024). Independent of smoking,
the κ -means cluster analysis revealed two clusters in which the high risk cluster involves occupation risk with air
pollution of more than four hours per day, main transportation involving motorcycle and trucks and mean annual PM2.5
concentration of more than 30 based on residential address for more than ten years. The increased risk for the high-risk
cluster was more than five times for the diagnosis of lung adenocarcinoma (OR=5.69, 95% CI=3.14-7.21, p<0.001).
The hazard ratio for the high-risk cluster was 3.89 (95% CI=2.12-4.56, p=0.02) for lung adenocarcinoma mortality at
1 year. Conclusion: High-risk cluster including PM2.5, occupation risk and mode of transportation as surrogates for
air-pollution exposure was identified and highly associated with lung adenocarcinoma diagnosis and 1-year mortality.


Volume 20, Issue 7
July 2019
Pages 1959-1965
  • Receive Date: 28 August 2017
  • Revise Date: 18 February 2018
  • Accept Date: 16 July 2019
  • First Publish Date: 16 July 2019