XI. Fill in each blank with a word from the box. controlled deaths negative matter pollutants emit Air pollution is the addition of gases, chemicals, and particle (1) pollutants into the atmosphere. Air pollution primarily comes from burning fossil fuels such as natural gas, petroleum, and coal. A study has listed air pollution as the cause of four percent of the (2) deaths in the United States. Humans are the main cause of air pollution. Industry, including (3) give and power plants, burn large quantities of fuel. (4) coal and petroleum releases sulfur oxides and nitrogen oxide into the air. Airplanes, boats, and cars burn petroleum, releasing carbon monoxide and carbon dioxide. The waste in landfills releases methane. Sulfur oxides, carbon monoxide and carbon dioxide, and methane all have a very (5) effect on air quality. These (6) can also contribute to the greenhouse effect. burning factories carbon Some air pollution is not directly caused by humans: for example, animals (7) dioxide when they breathe, and volcanoes release sulfur oxide. However, most air pollution is linked directly