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Smog more dangerous to some, study finds

It's not just the elderly who are vulnerable to the ill effects of air pollution, new research suggests.
/ Source: Reuters

It's not just the elderly who are vulnerable to the ill effects of air pollution, new research suggests.

In a study of 2.7 million deaths across 48 U.S. cities, researchers found that death rates tended to rise on days when ozone pollution, or smog, increased — with the older adults being most at risk.

However, while age was the strongest risk factor, there was also evidence that older women were more vulnerable to ozone pollution than older men were, and blacks were more vulnerable than other racial groups.

People with atrial fibrillation — a heart rhythm disturbance common in older adults — were also at increased risk of dying on days with poor air quality.

The study, conducted by Mercedes Medina-Ramon and Joel Schwartz of the Harvard School of Public Health, adds to evidence linking daily ozone increases to spikes in death rates.

It also suggests that even moderately elevated levels of ozone may be hazardous for certain vulnerable people.

The difference in pollution-related death rates between the elderly and young, for example, was much greater in cities that typically had relatively low ozone levels than in cities with generally high ozone concentrations.

This suggests that at high levels, ozone has a more uniform effect on death rates, the researchers explain in the journal Epidemiology.

Ground-level ozone forms when sunlight reacts with pollutants from cars, factories and other sources, and is the main component of smog. Ozone levels are typically highest in the summer.

Ozone pollution can cause inflammation in the airways and exacerbate respiratory ills like asthma and emphysema or other chronic diseases like heart disease. Because the elderly are more likely to have pre-existing medical conditions, they are also more vulnerable to the dangers of poor air quality.

In this study, each ozone increase of 10 parts per billion was linked to a 0.65 percent increase in the overall death rate. Among adults older than 65, that figure was 1.1 percent.

The reasons for the disparities between races and sexes are not clear, according to the researchers. They note, however, that one study of young adults found that black volunteers tended to have more breathing problems in response to ozone exposure.

The current findings, according to the researchers, may help lay the groundwork for air quality standards that better protect vulnerable people.