Evaluating the effect of daily PM₁₀ variation on mortality

Many epidemiological studies have shown the association between daily mortality and daily average of PM₁₀ level. Daily average of PM ₁₀ has been used for regression type time-series analysis. This article suggests that daily mean mortality is not only a function of daily mean but also a function of daily standard deviation of PM₁₀. We used generalized additive Poisson regression model with overdispersion parameter to investigate this hypothesis using the data from Seoul, Korea, from 1997 to 2001. One interquartile range (IQR = 42.11 μg/m³) increase of daily mean level of PM₁₀ was found to be associated with 2.1% increase of additional daily mortality (RR = 1.021, 95% CI = 1.009-1.035) after controlling for other confounders. Similarly, we also found that one IQR (11.93 μg/m ³) increase in daily standard deviation of PM₁₀ is associated with 2.5% increase of additional risk of death (RR = 1.025, 95% CI = 1.000-1.028) when other covariates remained the same. These findings may provide new insight into the possible explanation of health effect of PM10 and support the hypothesis that PM₁₀ deviation is also an important risk factor after controlling for daily mean PM₁₀ level.