The Invisible Poison

      Colorless and odorless, carbon monoxide can infiltrate the body's blood, sapping it of life-sustaining oxygen.
      Even short-term exposure to large amounts -- such as unknowingly sleeping in a house with a faulty furnace -- can trigger headaches, nausea and confusion. Those symptoms are warning signs that insufficient oxygen is reaching the brain and other vital organs.
      But researchers know less about the situation faced by residents in Las Vegas and other urban cities, where motor vehicle exhaust produces much lower, but more constant, levels of the poisonous gas.
      Polluted indoor air can be identified and eliminated with the assistance of a carbon monoxide detector, said Dr. Robert Morris, an environmental epidemiologist and associate professor at Tufts University.
      "With outdoor air, it's more difficult for an individual to address that problem," he said.
      Carbon monoxide -- a byproduct of combustion -- differs from ozone and dust pollution in that it primarily affects the heart, rather than the lungs. Some researchers also question how the gas may affect infants or even unborn children; research has been limited to animal studies.
      "Carbon monoxide binds to a component in the bloodstream that's responsible for delivering oxygen to the tissues," said Dr. Marc Bayer, a physician toxicologist at the University of Connecticut Health Center. "The organs that are most dependent on a high oxygen content are the brain and the heart."
      In Clark County, officials are braced for Environmental Protection Agency action to boost the area's air quality designation from "moderate" to "serious," based on continued difficulties in complying with federal standards. Last year, the EPA standards were exceeded three days.
      But healthy adults don't appear vulnerable, even when carbon monoxide levels violate federal standards, Morris said. However, people with heart problems may be at risk, he said. The epidemiologist was the lead author of a 1995 American Journal of Public Health study, which showed a correlation between carbon monoxide and hospital admissions for heart failure.
      "With outdoor air, what you are concerned with is people with pre-existing disease, who are very susceptible to any kind of environmental insult," said Morris, whose study tracked admissions in seven U.S. cities. "It appears that increases in carbon monoxide may be just enough to put people over the edge and put them in the hospital."
      The three days of unhealthful levels that exceeded EPA standards were recorded at two monitoring stations, both located near East Charleston Boulevard and Eastern Avenue. County estimates on the number of nearby residents who may be adversely affected have ranged from 10,000 to 100,000, said William Cates, principal planner in the Clark County Department of Comprehensive Planning.
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