For several decades now, pollution has become an increasing problem and a topic of major political debate. As global industry grows, pollution only increases. Pollution is defined simply as contaminants being introduced into an environment. Most instances of pollution fall under one of the following categories: Air pollution: Chemicals and harmful particulates released into the atmosphere. Cause of photochemical ozone as well as smog. Water pollution: Waste products and contaminants released into drainage systems. Soil contamination: Spills or underground leakage sometimes result in chemicals being released into the soil. Radioactive contamination: Nuclear power generation, nuclear weapons research, and other activities that harness nuclear energy release extremely dangerous radioactivity into the atmosphere, especially if not properly maintained or when accidents occur. Light pollution: Excessive light created by humans can have a negative impact on the natural environment and potentially damage human health. Nose pollution: Noise from roadways, aircrafts, and several industrial practices can have a significant negative impact on human activity. Visual pollution: An environment not in its natural state, usually damaged or tarnished by human activity. Some examples include excessive power lines, facilities used to store trash or solid waste, and heavy amounts of billboards or other forms of advertising. Thermal pollution: Changing in the natural temperature of a body of water, such as water used as a coolant for a power plant. For more information about the causes and effects of pollution, please see the links below.