Air Pollution as a Climate Forcing: A Workshop
Day 4 Presentations
Human Health Effects of Sulfate Aerosols
Nelson Institute of Environmental Medicine, NYU School of Medicine, Tuxedo, NY, U.S.A.
You may download a MS PowerPoint version (7.5 MB) of this presentation.
Sulfate aerosol, in the form of sulfuric acid, was believed by many to be a likely causal factor for the excess mortality and morbidity experienced during and following the December 1952 smog episode in London. The available present-day epidemiological evidence evaluating the potential human health effects of sulfates (SO4) is summarized in this presentation. This includes evidence of associations by sulfates with human mortality and morbidity, from both chronic and acute exposures. In addition, the correlations will be presented to show that SO4 and H+ can correlate both spatially and over time, due to sulfate's acidic nature. Sulfuric acid is the most strongly acidic form, with a pH of less than 1 at 50% RH, and ammonium bisulfate is also very strongly acidic, with a pH of 1-2 at 50% RH, while ammonium sulfate is only weakly acidic, with a pH of 5-6 (vs. a pH of 7.0 for completely neutral conditions). In addition to the epidemiological evidence, recent toxicologic studies also suggest that acidic sulfates can enhance the bio-availability of metals in particles, enhancing their ability to cause oxidative stress. Overall, sulfate containing particles have generally been shown to be associated with a range of significant and biologically plausible adverse human health effects.