Background: In the last decade several studies have found out an association between air pollution and mortality in levels below the standards allowed by regulations. Castellón is a small city (134,000 inhabitants) with low air pollution levels. This work aims to identify if there is a short term relation between these both variables in this city.
Methods: We used mortality data and air pollution data (black smoke and sulphur dioxide), from 1.991 to 1.995, doing an ecological study using a time series analysis with the day as unit of the analysis. Poisson regression allow us to get the relative risk adjusted by others variables (meteorological, trend, influenza, day of the week, season) in autoregresive models.
Results: Black smoke and SO2 daily means were respectively 34.6 and 15.7 micrograms/m3. Results showed a 3.6% (IC95 0.3-7.0) of SO2 and 3.5% (IC95% 0.5-6.5) increment of cardiovascular mortality for an increment of 10 micrograms/m3 of SO2 and black smoke respectively. Sulphur dioxide was positively associated with all four groups of mortality causes but only in cold season.
Conclusion: Even in a small city with low air pollution levels, we found an association between air pollution and immediate mortality. In some cases, the analysis by periods (warm and cold) show an strong effect modification.