(Ecns.cn) – Beijing was embarrassed last week as its residents swarmed to shops to buy face masks and air purifiers due to concerns about a thick cloud of smog that had enveloped the city. Matters were worsened by discrepancies between official air quality data and that from the U.S. Embassy, spurring a renewed call for a wider range of checks, particularly on PM2.5 pollution, which experts warn is increasing in the capital's air.
On Dec. 7, Ma Xuekuan, chief weather forecaster for the National Meteorological Center (NMC), said in a program called Half-Hour Economy on China Central Television (CCTV) that on Dec. 4 in Beijing the air pollution index had surged to above 400, achieving a rare rating of 5 – or "heavily polluted."
The program also quoted remarks made by Wang Yuesi, a researcher with the Institute of Atmospheric Physics at the Chinese Academy of Sciences, who said their data indicates that PM2.5 pollution has been on a worsening trend in Beijing since 1998, although he also claimed that measures to curb PM10 pollution had made preliminary achievements.
With the public more vehemently demanding the government to factor in PM2.5 in its official (and public) air quality data, the Ministry of Environmental Protection says it is already making final preparations to amend the national air quality standard.
Smog and PM2.5
In October and November, hazy skies frequently drove away the sky-blue color overhead in Beijing. According to the city's environmental protection bureau, Beijing has recorded three fewer "blue sky days" in the past 11 months of the year compared to the same period last year. (Although much of the debate is over how exactly Beijing decides how blue a "blue sky day" really is.)
Though many say factors such as weaker winds and a rise in humidity are the main causes of the smog, experts say the fundamental cause is in fact PM2.5, or airborne particulate matter smaller than 2.5 micrometers.
On Dec. 2, the first snow of the year fell in Beijing. Two days later, a gust of choking air floated down into the city on a terrible scale, causing the NMC to announce that the air was "heavily polluted" that day.
According to Ma Xuekuan, it is a normal phenomenon to see heavy fog shrouding the North China Plain in late autumn and winter. Usually such weather conditions result from weaker winds because there is an inversion layer in the lower atmosphere which traps the pollutants inside, he said.
However, Wang Siyue analyzed that it was not ordinary fog, but heavy smog that had engulfed the city, which resulted from the heavy density of PM10, PM2.5 and PM1, and that PM2.5 was the chief culprit. He said smog is not simply a weather condition, but a type of air pollution containing soot particles from smoke, sulfur dioxide, vehicular emissions, industrial fumes and other components. Such pollution is rich in secondary pollutants that are formed after reacting in the atmosphere with sunlight.
Wang added that when the particles are bigger they don't go too deep into the lungs and respiratory system, but that the tiny ones do, making PM2.5 the more hazardous to public health.
Threats to health
In recent weeks, patients with respiratory and cardiovascular problems have flooded hospitals in Beijing. The number of such patients increased dramatically at Beijing Shijitan Hospital after the smog blanketed the city on Dec. 4 when compared to last week.
Yu Hailing, deputy director of the Beijing Emergency Medical Center, said the number of dispatches of ambulances reached 1,694 in the 48 hours between Dec. 4 and Dec. 6, increasing by 74. Hospital statistics from Dec. 5 to Dec. 6 show that the number of cases related to respiratory and cardiovascular illness increased by 11.93%, while the cases resulting from car accidents rose 17.31% compared to the same period in the previous week.
Research shows that the growing density of PM2.5 is positively correlated with the number of patients with circulatory system, respiratory and cardiovascular problems, said Pan Xiaochuan, professor at the Peking University Health Science Center.
Pan revealed that he has been monitoring PM2.5 density and collecting data from nearby hospitals since 2004, and found that PM2.5 pollution threatens human health much more than PM10. But Pan also noted that the harm caused by PM2.5 is far less than that caused by second-hand cigarette smoke.
In 2003, the U.S. Environmental Protection Agency estimated that if PM2.5 pollution was controlled within the national standard, tens of thousands of people would be saved from early death every year.
Importance of taking PM2.5 into the national standard
Though Beijing has been monitoring the air quality with various scales such as PM10, PM2.5 and PM1, it has long used the PM10 scale to measure its air pollution levels, which makes particles measuring less than 10 micrometers in diameter the main focus of the monitoring effort.
Under this system, "hazardous" results can be ranked as relatively mild and similar to any other unusually foggy day, which has led to discrepancies between official data on the city's air quality and measurements taken according to other standards such as the U.S. Embassy's.
The hazy skies last week have sparked a more intense debate on the issue, and the Ministry of Environmental Protection has begun soliciting citizen comments since Nov. 16 concerning the amendment of the national air quality standard.
Wang Yuesi told reporters from CCTV that he has been conducting research on the monitoring data of both PM2.5 and PM10 since 1998, and had found that the average intensity of PM10 in Beijing is decreasing at a speed of between 2% and 3% every year, but that of PM2.5 is increasing by 3% to 4% on an annual basis.
Wang said that if a standard that includes both PM10 and PM2.5 was used, the number of blue sky days would be cut by 20% to 30% compared to the current figures. Even though the control of PM10 has achieved a certain level of progress, Wang also suggested that PM2.5 be taken into the new national air quality standard.
