We studied the association of daily mortality with short-term variations in
the ambient concentrations of major gaseous pollutants and PM in the Nethe
rlands. The magnitude of the association in the four major urban areas was
compared with that in the remainder of the country. Daily cause-specific mo
rtality counts, air quality, temperature, relative humidity, and influenza
data were obtained from 1986 to 1994. The relationship between daily mortal
ity and air pollution was modeled using Poisson regression analysis. We adj
usted for potential confounding due to long-term and seasonal trends, influ
enza epidemics, ambient temperature and relative humidity, day of the week,
and holidays, using generalized additive models.
Influenza episodes were associated with increased mortality up to 3 weeks l
ater. Daily mortality was significantly associated with the concentration o
f all air pollutants. An increase in the PM,, concentration by 100 mu g/m(3
) was associated with a relative risk (RR) of 1.02 for total mortality. The
largest RRs were found for pneumonia deaths. Ozone had the most consistent
, independent association with mortality. Particulate air pollution (e.g.,
PM10, black smoke [BS]) was not more consistently associated with mortality
than were the gaseous pollutants SO2 and NO2. Aerosol SO4-2, NO3-, and BS
were more consistently associated with total mortality than was PM10. The R
Rs for all pollutants were substantially larger in the summer months than i
n the winter months. The RR of total mortality for PM10 was 1.10 for the su
mmer and 1.03 for the winter. There was no consistent difference between RR
s in the four major urban areas and the more rural areas.