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Beijing’s Murky Pollution Numbers

August 8, 2008, 9:55 am – The Wall Street Journal

Beijing’s Air Pollution Index, also called API, is being closely watched this week as the Olympics begin. It’s being reported daily in dispatches about air quality and visibility in the city, and is included on the Online Journal’s Olympics page. But several factors make the index a questionable gauge of the air quality experienced by Olympians. And China’s translation of the index into “blue sky days” tends to understate the level of pollution, as journalists on the ground have noticed.

China considers any index number at 100 or lower to be acceptable. This is in line with developing nations, but would be considered inacceptable in developed countries, according to Kenneth A. Rahn, professor emeritus of oceanography at the University of Rhode Island. If the U.S. used a scale similar to Beijing’s, east coast cities typically would have index levels around 10 or 20; Beijing’s index has hovered near 100 in recent days. “In U.S. terms, that’s a ridiculously high concentration,” Prof. Rahn said.

For that reason, calling sub-100 days blue-sky days, as China does, is an arbitrary choice, Prof. Rahn said. “When you have a fixed point like 100, that you should not exceed, that creates an artificial duality. This is a legalistic argument. It has nothing to do with what’s going on in the atmosphere.”

The problems extend to what is measured, and how. Beijing’s index covers just three types of pollutants, according to Bill Scotti, who works with international companies on environmental issues in China as director of risk and compliance for Meradia Group. That contrasts with six in Hong Kong. Beijing doesn’t measure carbon monoxide, ozone or respirable suspended particulates — all of which are included in Hong Kong’s index. “Air pollution is measured differently in different regions of the world, and even differently within China itself,” Mr. Scotti told me.

As a practical matter, Beijing’s index really is based only on a single indicator: the concentration in the air of particulate matter with diameter less than 10 micrometers (or millionths of a meter). That’s because like some other indexes — including the U.S. air quality index — the Beijing index is equal to the highest index for any single pollutant. And in Beijing, particularly in the summer, the highest index value is usually the one for particulate matter, according to Prof. Rahn.

That’s an unfortunate choice for the index, Prof. Rahn told me, because environmentalists prefer to measure only particles with diameter less than 2.5 micrometers (the U.S. Environmental Protection Agency changed its standards in 2006). The larger particles are “not considered particularly dangerous to one’s health,” Prof. Rahn said. Including them clouds the pollution number further.

Including them doesn’t make the China index more stringent; the scales are raised to account for the inclusion of the broader group of particles. It just leaves the index a few years behind current standards in pollution reporting, and clouds the issue further.

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