Death rates up due to dust

Thursday, June 29, 2000 | 11:21 a.m.

Airborne dust such as the kind that blankets the Las Vegas Valley contributes to higher death rates and medical problems to those who are exposed, a study released Wednesday found.

The study of the 90 largest American cities by Boston-based Health Effects Institute isolated "particulate matter" under 10 microns in diameter, called PM10, as the cause for higher mortality rates.

The report says that the information, compiled from primary data sources nationwide, provides "new and strong evidence linking particulate air pollution to adverse health effects."

The dust, much smaller in diameter than a human hair, clouds the air in the valley, especially during windy days. The federal Environmental Protection Agency has classified the pollutant as a significant threat to human health.

That threat is particularly acute in the Las Vegas Valley, where the dust is kicked up by human activity and wind in the desert. Regional government agencies, including the Clark County Health District and Clark County Comprehensive Planning Department, are struggling to win EPA approval for a plan to control dust pollution, or face federal sanctions.

The health district board last week passed sweeping rules designed to cut the amount of dust in the air.

"We've known that pollution has had an impact for anyone with respiratory difficulties," said Michael Sword, assistant director of the health district's Air Pollution Control Division. He said that local statistics on emergency room admissions and deaths rise when pollution exceeds federal standards.

The study, prepared by researchers with Johns Hopkins University and the Harvard School of Public Health, backs up earlier, smaller-scale studies that also found a correlation between the dust pollution and mortality.

The study found that some of the most dramatic effects on the death rate occurred in the Northeast states. Investigators speculated that the higher mortality rate could be because of combination with other types of pollution, such as smog.

Another possibility is that the type of fine dust in those areas is simply more toxic. The study does not compare the dust from tailpipe emissions, which makes up most of the problem in the Northeast, to dust from ground sources, which makes up most of the problem in the Las Vegas area.

Robert O'Keefe, vice president of the Health Effects Institute, said the emphasis of the study was to look at the issue broadly, and not on one particular area of the country.

"What's important here is the overall weight of the evidence," said Dr. Jonathan Samet, principal investigator for the study.

A relatively small increase in the amount of dust in the air can lead to significant increases in death, particularly among the elderly or among people with lung diseases.

Each 20 micrograms of dust, per cubic meter over a 24-hour period, adds 1 percent to the death rate, O'Keefe said. Among the elderly, hospital admissions for cardiovascular problems increased 1 percent for each 10-microgram increase and cardiopulmonary admissions rose 2 percent.

While 1 percent might seem like a small number, over a regional or national scale that could total many deaths, he said.

The study did not project an actual number of deaths. Observers, however, said the study suggests that repeated exposure to the dust could result in thousands of premature deaths and health complications.

While most of the 17 reporting stations for the dust in Clark County are in the "good" range most of the time, stations in the heart of the valley have reported dust concentrations of over 151 micrograms per cubic meter a handful of times in the last year. That level is considered "unhealthy" by the EPA.

But the health effects of dust could be felt well below that threshold, the report said.

"Daily rates of morbidity and mortality from respiratory and cardiovascular diseases increase with levels of particulate air pollution even at levels well below the current" federal standards, the report said.

While the effects of dust are most acutely felt by the elderly and people with existing lung diseases, Samet said it isn't yet clear how much time in a life is lost because of exposure.

"Are these people who were about to die anyway? Are they losing a substantial amount of life?" Samet said. "We can't fully answer that question in the data in our report."

Local health professionals believe that air pollution, including dust, contributes to the higher-than-average number of breathing related problems in the Las Vegas Valley. Children in the valley have a 10 percent chance of acquiring asthma, higher than the national average of 7 percent.

Samet, who is chairman of the National Research Council's Committee of Research Priorities for Airborne Particulate Matter, said the dust, its effects and the synergistic effect with other pollution needs to be studied further. He said there are now a number of research projects under way.

The Health Effects Institute receives half of its funding from automobile manufacturers, the other half from the EPA, which is publishing the study.

According to the Associated Press, the Ford Motor Co., an institute funder, issued a statement calling for more research on the issue.