The concentration-response relation between air pollution and daily deaths.

Area of Science:

• Environmental Epidemiology
• Public Health
• Air Pollution Research

Background:

• Previous studies globally suggest links between airborne particles and daily mortality.
• The presence of thresholds for air pollution effects at low concentrations remains uncertain.
• Sulfur dioxide (SO2) has been associated with mortality, especially in Europe.

Purpose of the Study:

• To investigate the association between daily concentrations of black smoke and SO2 with daily deaths in eight Spanish cities.
• To determine the shape of the concentration-response curves and identify potential thresholds at low pollution levels.
• To compare the strength of association for black smoke versus SO2 on mortality.

Main Methods:

• Utilized nonparametric smoothing to estimate concentration-response curves for black smoke and SO2 in each city.
• Employed a metasmoothing technique, extended with random variance components, to combine city-specific results.
• Conducted analyses using both one- and two-pollutant models, with varied weather and seasonal modeling approaches.

Main Results:

• Black smoke exhibited a nearly linear association with daily deaths, showing no evidence of a threshold.
• A 10 microg/m(3) increase in black smoke correlated with a 0.88% rise in daily deaths (95% CI: 0.56%-1.20%).
• Sulfur dioxide displayed a less consistent association, with deaths increasing at low levels but plateauing or decreasing at higher concentrations.

Conclusions:

• The association between particulate matter (black smoke) and mortality is more robust than that for SO2.
• Evidence suggests no safe threshold for the adverse health effects of black smoke exposure.
• Linear models adequately estimate the impact of low to moderate concentrations of particulate air pollution on mortality.