pp 5167–5168
ES&T News
Getting religious about air pollution
Stephen Weber is a research associate in the department of applied climatology at the University of Duisberg-Essen (Germany); he studies the effect large cities have on the local atmosphere. However, a couple of years ago a newspaper article distracted him from his research. The story detailed new findings by scientists in The Netherlands who reported that candles created concentrations of air pollution that are unsafe. But the journalist did not provide any data to back up the claim. Because Weber lived next door to a church, he decided to look into the issue himself.
“I wanted to quantify the pollution levels,” he says.
Weber’s initial interest in the newspaper article blossomed into a study published in this issue of ES&T (pp 5251–5256), in which he finds that candles do not actually create excess indoor pollution. However, he discovered that burning incense during holiday masses does briefly expose worshippers to high levels of unhealthy particulate matter, which is associated with respiratory, pulmonary, and cardiovascular disease. Although the results are not cause for alarm, they do raise concerns for people in poor health.
For the study, Weber placed 2 optical particle counters in the corner of a Catholic church in Mülheim/Ruhr (Germany) and took measurements from December 24, 2004, to January 5, 2005. During a regular service, ~20 candles were burned, but during high mass at Christmas, ~80 candles were lit and incense was kept smoldering.
Weber found that the candles caused a negligible increase in air pollution, whereas incense put a greater volume of microscopic particles into the air. For instance, the concentration of coarse particulate matter <10 µm in diameter (PM10) increased 6.9×, and the concentration of ultrafine particles <1 µm in diameter (PM1) rose 9.1×. This second result is especially troubling, because these tinier pollutants are thought to travel farther into the lungs.
Weber says that particle concentrations rose and peaked within minutes after incense was lit, filling the church with pollutants, which dissipated after 24 h. “During the whole service, you have very high levels,” he says.
The EU and the U.S. EPA standard for PM10 is 50 µg/m3. However, EPA’s 24-h standard is 150 µg/m3, and the agency plans to lower that level to 70 µg/m3. Weber measured PM10 levels of 220 µg/m3. However, parishioners were breathing in the particulate matter for only a couple of hours.
It is hard to say whether these short-term exposures to high levels are actually dangerous, Weber says.
The literature on tobacco smoke finds that even brief contact, on the order of 30 min, can cause problems with vascular flow and the function of cells lining blood vessels, points out Jonathan Samet, chair of the department of epidemiology at the Johns Hopkins School of Public Health. Brief exposures to pollutants emitted by incense may not cause these physiological effects, but older people and those with health problems should take notice when they attend services where large volumes of incense are burned.
“I think some of the literature on asthma and cardiovascular disease does suggest this is reasonable to think about,” he says.
This next Christmas season, Weber says he plans to collect some of the ultrafine particles floating through the church and study them back in the lab. Although researchers know that tiny particles are unhealthy, an examination of their makeup should provide more clues about their danger.
“I want to look more into the chemistry of these particles to see if they are toxic,” Weber says.
