environment

4. These are U.S. federal regulations that set minimum average miles-per-gallon (mpg) targets for a manufacturer’s fleet of passenger cars and light trucks
6. are a group of highly reactive gases
7. sedimentary rock composed primarily of calcium carbonate
9. fundamental reaction that drives the natural degradation of organic matter
11. a substance that pollutes something
12. any form of water—liquid or solid—that falls from the atmosphere to the Earth's surface

1. sulfur dioxide (SO2) and nitrogen oxides (NOX) are emitted into the atmosphere and transported by wind and air currents
2. authorizes the EPA to regulate air emissions from stationary and mobile sources to protect public health and the environment.
3. a colorless, pungent, and toxic gas primarily generated by burning fossil fuels
5. the transfer of acidic sulfur and nitrogen pollutants from the atmosphere to the Earth's surface
8. the process of reducing the pH of natural environments
10. industrial air pollution control device that removes harmful particles and gases from exhaust streams