china

Shockingly little has been published in the peer-reviewed literature about the air pollution in China, although there has been plenty of press coverage. I talked a little bit about the US Embassy twitter data and how fires polluted the air over Beijing*. The health impacts of the exposure of humans to sustained levels of unhealthy or hazardous air pollution levels is widely expected to increase mortality rates due to cardiorespiratory failure and increased instances of cancer. The question then is raised: What hard evidence exists that proves this hypothesis? Modeling studies seemed like they would have to suffice. Until now.

Researchers from China, Israel, and the USA just published what I would call a very important study that concludes that elevated particle pollution in Northern China compared to Southern China has reduced life expectancy by 5.5 years. They took advantage of a dataset that emerged as a result of a Chinese policy employed from 1950-1980 that provided free coal for heating for everyone living north of the Huai River that runs right through the center of China and shown as the black line in the figure below.

What they found was that particle pollution concentrations were 55% higher in Northern China due to the availability of free coal. This strong and significant difference between the north and south as a result of the Huai River policy (as the researchers call it) set up an experimental control scenario on a large enough scale (population wise) that the statistics were robust. The statistical model combined the particle concentration difference with proximity to the Huai River, detailed mortality statistics from a program in China called the Disease Surveillance Points (DSPs), and a number of other possible factors that may influence mortality to prove with high confidence that their results were robust. The life expectancy of the Chinese citizens north of the Huai River (which includes Beijing, Lanzhou, and Xian) is on average 5.5 years less than those of citizens living south of the Huai River. The decrease in life expectancy, the research shows, was almost entirely attributable to the 55% increase in particle pollution concentrations. The paper is worth reading, especially given the current state of Chinese air quality referred to above.

*I mentioned the effect of smoke from agricultural fires on Beijing particulate matter (PM2.5) concentrations, and there has been a lot of internet discussion of the US Embassy twitter feeds documenting PM2.5 concentrations in now 5 major urban centers of China that are geographically distributed from Shenyang in the Northeast to Beijing and Shanghai in the East, and Chengdu in central China, and finally in the south in the city of Guangzhou which is north of Hong Kong. PM2.5 refers to the mass concentration of particles with diameters less than 2.5 micrometers or 0.0000025 meters and is without a doubt the most devastating form of particulate matter air pollution for the human body. This stems from the simple idea that smaller particles can be inhaled more deeply into the respiratory system. Smaller? Smaller than what? Well, other categories of PM also exist. PM10 refers to mass concentrations of particles with diameters less than 10 micrometers, or 10 millionths of a meter or 0.000010 meters. Still very small. Then there is the less precise category of total suspended particles (TSP) which presumbably includes some fraction of particles greater than 10 micrometers in diameter while also including the mass of the smaller particles. Typically, PM10 and TSP are closely related because particles larger than 10 micrometers tend to fall out of the atmosphere much more quickly. Regardless of the PM (PM2.5, PM10, TSP), they are all bad.

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