Air-Quality Standards

To the Editor.— In discussing "Health Effects of Urban Air Pollution," Mitchell et al (242:1163, 1979) seem to take the view that current national ambient air quality standards, as adopted by the Environmental Protection Agency, for carbon monoxide (CO) are justified for sea level, but that an eight-hour CO standard of 6 ppm should be substituted in high-altitude areas. Adjustment of the basic CO standard to accommodate for high-altitude effects is reasonable, but, for sea level areas, the present 9 ppm, eight-hour CO standard, which may be exceeded only once a year, is already more stringent than can be justified by cost-benefit analysis. The difference between using a 15 ppm, eight-hour CO standard and a 9 ppm, eight-hour CO standard is an increase of 1% in COHb concentration. Can one truly argue that this makes any real difference to a person's health if it happens five to ten times a year