| Abstrakt: |
To the Editor.—Carbon monoxide (CO), produced by incomplete combustion of carbonaceous material, is a major air pollutant with well-described adverse effects on human health. In a national survey of the range of carboxyhemoglobin (COHb) levels in blood donors representing various segments of the American population conducted in 1970, Stewart et al1 found a mean COHb level for nonsmokers living in Chicago of 2.04% (90% confidence limits, 1.0% to 3.2%), with 74% having a level in excess of the 1.5% limit of the Air Quality Standards of 1971. By 1974-1975, the mean COHb level for Chicago nonsmokers had fallen to 1.53% (90% confidence limits, 0.7% to 2.4% ), a difference that was statistically significant (P<.001).2 The greatest reduction in COHb levels occurred in downtown Chicago, the area of highest automobile density, leading the authors to speculate that reduction in CO in automobile exhaust due to emission control laws |
