Replacing fossil diesel by biodiesel fuel: expected impact on health.

Biofuels have become an alternative to fossil fuel, but consequences on human health from changes to emissions compositions are not well understood. By combining information on composition of vehicle exhaust, dispersion models, and relationship between exposure to air contaminants and health, the authors determined expected mortality outcomes in 2 scenarios: a blend of 10% biodiesel and 90% standard diesel (B10) and biodiesel only (B100), for a rural and an urban environment. Vehicle exhaust for both fuel compositions contained lower fine particle mass but higher NO2 levels. Ambient air concentrations in scenario B10 were almost unchanged. In scenario B100, PM2.5 (particulate matter with an aerodynamic diameter <2.5 µm) levels decreased by 4-8% and NO2 levels increased 7-11%. Reduction of PM2.5 is expected to reduce mortality rate by 5 × 10(-6) and 31 × 10(-6) per year, whereas NO2 increase adds 17 × 10(-6) and 30 × 10(-6) to mortality rate for B10 and B100, respectively. Since effects of PM2.5 and NO2 are not independent, a positive net effect is possible.