Environmental policy of the United States Environmental Protection Agency, were people with a history of opposition to the agency they were named to head. Since the environmental movement of the 1970s, the nature of environmental issues has changed. While the initial emphasis was on conventional air and water pollutants, which were the most obvious and easily measurable problems, newer issues are long-term problems that are not easily discernible and can be surrounded by controversy. Acid deposition, in the form of acid rain and dry deposition, is the result of sulfur and nitrogen dioxide being emitted into the air, traveling and landing in a different place, and
Barbara J. Finlayson-Pitts from the reactions that occur within each layer. In the atmosphere, emitted gases and particles may react further to form new chemical species. Some compounds may not react within the troposphere, but will break down and participate in further transformations in the higher stratosphere. The inorganic chemistry of oxides of nitrogen and sulfur in the gas phase are better understood than the interactions of nitrogen and sulfur oxides with organic compounds. Finlayson-Pitts and her colleagues have done important work on understanding the chemistry of the troposphere, in particular, the conversion of nitric oxide (NO) to nitrogen dioxide (NO2) in air