This paper examines the health consequences of these extraordinary
pollution levels by exploiting a seemingly arbitrary
Chinese policy that produced dramatic differences in air quality
within China. During the 1950–1980 period of central planning,
the Chinese government established free winter heating of homes
and offices via the provision of free coal for fuel boilers as a basic
right. The combustion of coal in boilers is associated with the release
of air pollutants, and in particular emission of particulate
matter that can be extremely harmful to human health (4, 5). Due
to budgetary limitations, however, this right was only extended to
areas located in North China, which is defined by the line formed
by the Huai River and Qinling Mountain range (Fig. 1). Even
today, the long-lived heating systems continue to make indoor
heating much more common in the north.