Variability of PM level with gaseous pollutants and meteorological parameters during episodic haze event in Malaysia: Domestic or solely transboundary factor?

Haze has become a seasonal phenomenon affecting Southeast Asia, including Malaysia, and has occurred almost every year within the last few decades. Air pollutants, specifically particulate matter, have drawn a lot of attention due to their adverse impact on human health. In this study, the spatial and temporal variability of the PM concentration at Kelang, Melaka, Pasir Gudang, and Petaling Jaya during historic haze events were analysed. An hourly dataset consisting of PM, gaseous pollutants and weather parameters were obtained from Department of Environment Malaysia. The mean PM concentrations exceeded the stipulated Recommended Malaysia Ambient Air Quality Guideline for the yearly average of 150 μg/m except for Pasir Gudang in 1997 and 2005, and Petaling Jaya in 2013. The PM concentrations exhibit greater variability in the southwest monsoon and inter-monsoon periods at the studied year. The air masses are found to be originating from the region of Sumatra during the haze episodes. Strong to moderate correlation of PM concentrations was found between CO during the years that recorded episodic haze, meanwhile, the relationship of PM level with SO was found to be significant in 2013 with significant negatively correlated relative humidity. Weak correlation of PM-NOx was measured in all study areas probably due to less contribution of domestic anthropogenic sources towards haze events in Malaysia.