| OCR Text |
Show the lungs to the body. Since CO is 220 times more effective than oxygen at attaching to hemoglobin in the blood, scientists can calculate precisely how much CO in the air will be associated with various levels of CO in the blood and what the corresponding health effects will be. The maximum one-hour standard for CO is set at 0.0003 percent in air, or 35 parts-per-million (ppm). The standard for an eight-hour average concentration is 9 ppm. At these levels of CO in the air, the blood will have only 0.5 to 1.7 percent of its hemoglobin tied up by CO. There are no symptoms or adverse health effects from CO at these levels. In fact, symptoms of CO poisoning are not manifest in most healthy people until blood levels exceed 15 percent. The CO air standard provides a large margin of safety for normal individuals and a comfortable level of protection for people which chronic cardiovascular and respiratory disease. The level of protection possible for ozone is much different. Chemically, the ozone molecule is made of three oxygen atoms (O3); normal oxygen is made of two oxygen atoms (O2). Ozone oxidizes, or reacts with things much more readily than normal oxygen. When ozone is inhaled, it attacks the lining of the respiratory system; i.e., the nose, throat, trachea, bronchi and lungs, and it does this at very low concentrations. Studies have documented respiratory effects from ozone in concentrations as low as 0.25 ppmi, or when ozone levels in the air are at 0.000025 percent. Background levels of ozone in unpopulated areas are in the .03-.05 ppm range. The air standard for ozone is currently set at 0.12 ppm. There is virtually no margin of safety between the current standard and where adverse effects have been seen. The threshold toxic level is only 4 to 5 times higher than background levels. In a practical sense, there is a definite limit to how much protection any standard can reasonably be expected to provide from ozone. The ozone standard is presently under review by EPA and is likely to be tightened, though there is very little room to do this without approaching background levels. The air quality standard for PM10 is also under review by EPA. Recommendations to include a standard for particulates in the 2.5 micron and smaller range is expected this summer. The recommendation for a new PM2.5 standard is based on a general consensus that particles made of condensed gases from burning fuels fall into this size range and are biologically more reactive and potent than the larger particles. The review of the standard has also been prompted by studies which have shown an association between pollution, including PM10 pollution, and slight increases in mortality rates in over a dozen cities in the United States and Europe.2 These epidemiological studies are being looked at with concern. Taken at face value, they imply that there is no safe level for PM10. While no one is questioning that PM10 is harmful, there is some controversy over how precise and valid the epidemiological data may be in quantifying risk since the observed associations do not prove a causal relationship between PM10 and premature mortality. Indeed, a number of studies in Utah have failed to show such associations.3,4 Despite these conflicting observations, and even though a feasible mechanism has not been offered for how outdoor PM10 could be affecting at-risk populations in hospitals and care centers, EPA has concluded that the epidemiological studies and anecdotal experience suggest that PM10 concentrations below the current standard may be posing some, though presently unquantified, risk to public health. Conclusions The health risks from air pollution in Utah are diminishing as Utah experiences fewer and fewer exceedances of the national air quality standards. Risks from exposure to lead and to oxides of sulfur and nitrogen are quite negligible, and there is a comfortable margin of safety between the CO standard and adverse health effects. Transitory exceedances of the CO standard, while undesirable, are not an immanent threat to health. The air pollutants that put Utahns at greatest risk are ozone and PM10. There are two counties, Salt Lake and Davis Counties, with a combined population of over 900,000 currently classified as not attaining the standard for ozone, but both counties have reported ozone levels within the standard for the last five, years and Utah has formally requested that EPA redesignate these counties as being in compliance with the standard. Notwithstanding this progress, ozone remains a risk to health because there is virtually no margin of safety between the standard and adverse health effects. It will take aggressive and vigilant efforts to assure that future population growth does not result in unhealthy ozone levels. 22 Health Risk from Air Pollution |
