Abstracts: ISEE 20th Annual Conference, Pasadena, California, October 12–16, 2008: Contributed Abstracts
In recent decades, the number of heat-waves occurring in the Netherlands increased. Severe heat waves in 2003 and 2006, probably caused tens of thousands excess deaths throughout Europe, and led to a number of publications on the effect of heat on mortality. Some of these suggest a modification of air pollution effects during heat waves. We assessed whether air pollution effects on mortality show an increase during heat waves in the Netherlands. In the Netherlands a heat wave is defined as a period of five or more consecutive days with a maximum temperature of at least 25 °C, of which three or more days show a maximum temperature of at least 30 °C, as measured in the centrally located town of De Bilt.
We present the analysis of covariate adjusted time series of daily mortality, air pollution and temperature in the Netherlands from 1986 up to 2006 using generalized additive models (GAM) with penalized splines to explore the effect of heat waves on the effect of air pollution on mortality. Additional covariates included relative humidity, ambient air pressure, influenza cases, pollen counts, national holidays, and day of the week. Daily air pollution data for particulate matter, ozone, nitrogen dioxide, nitric oxide, and black smoke were measured at the National Air Quality Measurement Network. Daily counts for total non-accidental, cardiovascular, respiratory, COPD, and pneumonia mortality were provided by Statistics Netherlands. Meteorological data were provided by the Royal Netherlands Meteorological Institute. We used the mgcv package in R for GAM modelling applying cubic regression splines.
Results and Discussion:
Our results show increased effect estimates of the associations between air pollution and daily mortality during a heat wave period compared to non heat wave periods, suggesting that a substantial number of daily deaths attributed to high temperatures, could be attributed to the interaction between temperature and air pollution.