human
I've heard that there's a big problem with pollution in the United States. What are the main causes of pollution?
assistant
The main cause of pollution is the burning of fossil fuels, which releases carbon dioxide and other pollutants into the atmosphere. Other sources of pollution include industrial processes such as smelting, chemical manufacturing, and mining; agricultural activities like fertilizer use and animal waste disposal; and transportation, including cars, trucks, ships, planes, and trains.