Background: The main study objective was to determine the associations between mean daily concentrations of criteria air pollutants and the risks of respiratory and cardiovascular mortality at hospitals in Malaysia’s Klang Valley.
Methods: The study period was 1-31 August 2005. Two areas in the valley, Port Klang and Kuala Lumpur, and two areas in northwestern Malaysia, Penang and Langkawi, were selected. The study sample was all respiratory (ICD-10 J00-J99) and cardiovascular (ICD10 I10-I99) disease cases who were discharged as deceased from (for mortality data), the study hospitals during the study period. Air quality data on respirable particulate, nitrogen dioxide, sulphur dioxide, carbon monoxide, and ozone were obtained from continuous air quality monitoring stations located nearest to the hospitals in these four areas. Data on maximum temperature and rainfall were obtained from the four closest meteorological stations. Spearman correlation was then used to model the relationships between daily variations in the five air pollutants with variations in in-patient mortality statistics.
Results: Of the five criteria air pollutants, PM₁₀ was the pollutant that exceeded the 24-hour average Malaysian Ambient Air Quality Guidelines (MAAQG) for PM₁₀ of 150 μg/m³ 6-12 August in both Klang and Kuala Lumpur, and on 13 August in Penang and Langkawi. In Kuala Lumpur, the 24-hour mean temperature (r = 0.586, p<0.005) was directly correlated with PM₁₀ concentration.
Conclusions: The variability of respiratory and cardiovascular case mortality in the four areas was not attributed to the change in the concentration of PM₁₀ in ambient air over time. This outcome may be due to several factors such as the limitation in the area of influence of the 2005 haze episode in Malaysia, relatively lower concentrations of PM₁₀ in ambient air, etc.