Mortality and air pollution in metropolitan Helsinki, 1988--1996

The daily respiratory, cardiovascular, and total mortality of the population in the subarctic climate of the Helsinki metropolitan area was analyzed for associations with daily variations in concentrations of common ambient-air pollutants.

The associations between daily mortality and the ambient-air concentrations of ozone (O3), nitrogen dioxide (NO2), carbon monoxide (CO), sulfur dioxide (SO2), total suspended particulate matter (TSP), and particulate matter with an aerodynamic diameter of <10 microm (PM10) in 1988--1996 were analyzed with Poisson regression in a generalized linear model. Specifically, the differences for combustion and noncombustion particulate matter were determined using the blackness of the TSP filters as a surrogate for mostly traffic-derived combustion particles. Total mortality was analyzed according to three age groups (15-64, 65-74, > or =75 years) of the population.

Significant associations consistent across lag times and age groups were found between spring and summer O3 levels and respiratory (4.30% increase per 10 microg/m3 of the 4-day mean O3 level) and total (2.42% increase per 10 microg/m3 of the 4-day mean O3 level) mortality. PM10 was consistently associated with respiratory mortality across the lag times and age groups (3.96% increase per 10 microg/m3 of PM10 at lag-time 1). When adjusted for TSP concentration, the blackness of the TSP was significantly associated with total mortality (2.06% per 10(-5) units, 95% confidence interval 0.09-4.06) at lag time 1, but not at the other lag times.

These results provide additional evidence of an association between summertime O3 concentrations and mortality. They also support the findings of previous studies indicating that coarse mineral particles are not as strongly associated with mortality as fine, combustion-derived particles are.