3.1.2. Evolution of Population and Pollution

However, Changzhou's urbanization had a profound effect on the environment. Figure 3 shows that the pollution index—calculated using the linear weighting method based on the three industrial waste sources, namely, waste gas, wastewater, and waste solids—increased from 0.13 to 0.66, indicating that pollution emissions increased greatly from 1990 to 2015 (Figure 3). The cumulative emissions per unit area also increased. In particular, the cumulative emissions of industrial solid waste per km<sup>2</sup> increased from 1.94 to 60.23 million kg. As industrial waste emissions were new pollutants produced each year, both cumulative pollution emissions and pollution exposure led to increased health risk. Risk to health increased with more pollutants and pollution exposure. Furthermore, population density increased, although there was a small fluctuation before 2008. Thus, the environment was deteriorating while population increased. In other words, more and more people were exposed to an increasingly polluted environment.
