Characterizing mortality effects of particulate matter size fractions in the two capital cities of the Canary Islands.

Most of the studies differentiating the effect of size-classified particulate matter (PM) exposure have been carried out in cities where the average levels of fine particles (PM(2.5)) were higher than those of coarse particles (PM(10-2.5)). These studies have suggested that PM(2.5) is associated with daily mortality, but there is only limited evidence that PM(10-2.5) is independently associated with mortality. The citizens of the Canary Islands are exposed to PM which is highly influenced by mineral dust because of the islands' proximity to the Western Coast of Morocco. This offers an excellent opportunity to analyze in detail the short-term association between PM size fractions and total, respiratory and heart disease mortality. A time-series study from 2001 to 2004 was carried out. For each PM size fraction and mortality outcome, Generalized Additive Poisson Model was performed controlling for potential confounding. Different lag structures, unconstrained distributed lag models and two-pollutant models were examined. After assessing the linearity in the relationship, a piecewise linear analysis for exploring the existence of different slopes for different ranges of PM was carried out. The 10 µg/m(3) increase in PM(2.5) and PM(10-2.5) levels was associated with a 7.5% (95% confidence interval=0.4-15.0) and a 7.4 (95% CI=1.5-13.7) increase in heart and respiratory disease mortality, respectively. Spline curves were quite linear over the PM concentrations seen on most days (dominated by combustion sources) in these cities, meanwhile on days with higher particulate levels (natural sources) a risk increase above certain PM levels was found, suggesting a curvilinear association and that, at least in some locations, PM(10-2.5) can play an important role in PM-related toxicity. The overall findings suggest that the establishment of new air quality standards for the short-term effect of PM(2.5) and PM(10-2.5) and further limiting levels of PM(10) in European Union is advisable.

Air pollution and mortality in the Canary Islands: a time-series analysis.

BACKGROUND: The island factor of the cities of Las Palmas de Gran Canaria and Santa Cruz de Tenerife, along with their proximity to Africa and their meteorology, create a particular setting that influences the air quality of these cities and provides researchers an opportunity to analyze the acute effects of air-pollutants on daily mortality. METHODS: From 2000 to 2004, the relationship between daily changes in PM10, PM2.5, SO2, NO2, CO, and ozone levels and daily total mortality and mortality due to respiratory and heart diseases were assessed using Generalized Additive Poisson models controlled for potential confounders. The lag effect (up to five days) as well as the concurrent and previous day averages and distributed lag models were all estimated. Single and two pollutant models were also constructed. RESULTS: Daily levels of PM10, PM2.5, NO2, and SO2 were found to be associated with an increase in respiratory mortality in Santa Cruz de Tenerife and with increased heart disease mortality in Las Palmas de Gran Canaria, thus indicating an association between daily ozone levels and mortality from heart diseases. The effects spread over five successive days. SO2 was the only air pollutant significantly related with total mortality (lag 0). CONCLUSIONS: There is a short-term association between current exposure levels to air pollution and mortality (total as well as that due specifically to heart and respiratory diseases) in both cities. Risk coefficients were higher for respiratory and cardiovascular mortality, showing a delayed effect over several days.