MONDAY, Dec. 29, 2014 (HealthDay News) -- Air pollution in Mecca rises sharply each year when millions of Muslims make the annual holy pilgrimage (hajj) to the Saudi Arabian city, a new study shows.
"Hajj is like nothing else on the planet. You have 3 to 4 million people -- a whole good-sized city -- coming into an already existing city," Isobel Simpson, a research chemist in the atmospheric chemistry laboratory at the University of California, Irvine, said in a university news release.
"The problem is that this intensifies the pollution that already exists. We measured among the highest concentrations our group has ever measured in urban areas -- and we've studied 75 cities around the world in the past two decades," she added.
The researchers took air samples in various locations in Mecca during the 2102 and 2013 hajjes in October. The results showed high levels of various air pollutants, many of which can cause serious health problems.
"There's carbon monoxide [CO] that increases the risk of heart failure. There's benzene that causes narcosis and leukemia. But the other way to look at it is that people are not just breathing in benzene or CO, they're breathing in hundreds of components of smog and soot," Simpson said.
Air pollution was worst inside the Al-Masjid Al-Haram tunnel, where pedestrians, hotel workers and security personnel are exposed to fumes from idling vehicles, often for hours, the researchers said.
The tunnel was where researchers recorded the highest level of carbon monoxide -- 57,000 parts per billion. That reading during the 2012 hajj is more than 300 times the normal background levels of carbon monoxide in the region, according to the news release.
Saudi officials are taking steps to improve the situation, the researchers said.
The study was presented recently at a meeting of the American Geophysical Union in San Francisco and published in the journal Environmental Science & Technology.
"Air pollution is the cause of one in eight deaths and has now become the single biggest environmental health risk globally," study co-author Haider Khwaja, of the University at Albany in New York, said in the news release.
"There were 4.3 million deaths in 2012 due to indoor air pollution and 3.7 million deaths because of outdoor air pollution, according to [the World Health Organization]. And more than 90 percent of those deaths and lost life years occur in developing countries," he said.
The U.S. Environmental Protection Agency has more about the health effects of air pollution.