File photo: Buildings are shrouded in fog near the Guomao Bridge in Beijing, capital of China, January 23, 2013. Photo: Xinhua



Beijing's polluted air contains excessive amounts of heavy metals, which can damage the nervous system and cause cardiovascular disease and cancer, according to a report released Tuesday that tested the capital's air over a 15-day period during December and January.



The concentration of arsenic, one of the heavy metals in PM2.5 airborne pollutants, was almost four times greater than the recommended level for 12 of the 15 days that were studied, according to researchers from Greenpeace and scholars with Peking University.



The average daily concentration of arsenic was 23.08 nanograms per cubic meter or 3.85 times greater than the limit set by the Ministry of Environmental Protection. Cadmium concentrations were above the recommended level four of the 15 days, while lead was above standards on two days.



The World Health Organization labels arsenic a carcinogenic and it is listed as the No.1 hazardous substance for human health by a US federal public health agency.



"The concentration of arsenic dropped a little compared to previous studies, but it's still much higher than many foreign cities," said Pan Xiaochuan, a professor with Peking University's School of Public Health.



Arsenic concentration increased during heavily polluted days, Pan said, adding that most arsenic in the atmosphere comes from coal burning and industrial metallurgy. He said children, seniors and pregnant women are especially vulnerable to arsenic poisoning. His nationwide research shows that a higher concentration of arsenic will negatively impact the human respiratory system.



Researchers collected part of the data by having nine volunteers, between 5 and 40 years old, wear a device that measured PM2.5 for 20 hours while they worked and played both indoors and outdoors.



One of the volunteers, Zhong Yu, wore a device while running a marathon in Beijing last year, and the PM2.5 she was exposed to reached 152.73 micrograms per cubic meter, twice the national limit.



She told the Global Times she is always in a quandary over whether "to run, or not to run," in Beijing.



"Many people hire a coach or buy expensive equipment for their workout, but they rarely consider if the air is good enough," Zhong said.