What are the major classifications of air pollutants?
Most air pollutant gases are invisible to the naked eye, with the exception of nitrogen dioxide, which has a brownish color. Even air that appears to be clean and clear contains a multitude of small solid particles. One cubic foot of air can contain millions of air pollution particles! Scientists have observed that cities can have hundreds to thousands of times more particles than rural regions.
There are two basic types of pollutants: gases and aerosols. Aerosols consist of either solid materials or liquid droplets such as sulfuric acid. Most air pollutant gases are invisible to the naked eye, with the exception of nitrogen dioxide, which has a brownish color. Even air that appears to be clean and clear contains a multitude of small solid particles. One cubic foot of air can contain millions of air pollution particles! Scientists have observed that cities can have hundreds to thousands of times more particles than rural regions.
