1 Respiratory Unit, Universiti Kebangsaan Malaysia Medical Centre, Faculty of Medicine, University Kebangsaan, 56000 Cheras, Malaysia; Department of Clinical Oncology, University Technology MARA, 40450 Shah Alam, Malaysia.
2 School of Environmental and Natural Resource Sciences, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, Bangi 43600, Malaysia; Institute for Environment and Development (Lestari), Universiti Kebangsaan Malaysia, Bangi 43600, Malaysia.
3 Respiratory Unit, Universiti Kebangsaan Malaysia Medical Centre, Faculty of Medicine, University Kebangsaan, 56000 Cheras, Malaysia.
4 Respiratory Unit, Universiti Kebangsaan Malaysia Medical Centre, Faculty of Medicine, University Kebangsaan, 56000 Cheras, Malaysia. Electronic address: tidi.maharani.hassan@ppukm.ukm.edu.my.