The roots of the acid rain problem can be traced back to human activities. People need to produce and consume energy in order to meet their basic needs. If that energy is provided in the form of uncontrolled combustion of fossil fuels, then contamination of the atmosphere occurs through the release of a variety of chemical species. In this paper, the focus is on those species that lead to acid deposition: sulfur dioxide (SO₂) and nitrogen oxides (NO_x). Clearly, the more people there are, the more energy is needed, and the greater the atmospheric pollution.
 

Northeast Asia is one of the most densely populated regions of the world. In 1990, the populations of the countries of the region were as follows: Japan (124 million), South Korea (43 million), and North Korea (22 million). The total population of China was about 1.17 billion, though the breakout for Northeast China is not readily available. Large populations, high population density, and high population growth rates are all well-known characteristics of the Asian situation. In broad terms, it is projected that the population of Asia will continue to grow at a fast pace, but gradually decelerate after the turn of the century. The RAINS-Asia study assumes annual average population growth rates over the entire continent of 1.66% (1990-2000), 1.47% (2000-2010), and 1.33% (2010-2020). By 2020, the population of Asia is projected to reach 4.6 billion, an increase of 55% over 1990 levels.