These gases include oxidizers such as ozone and various oxides of nitrogen. Corona causes degradation of electrical insulation and emission of ozone and nitrogen oxide. It also has an important role in eliminating some greenhouse gases like methane and ozone. Low level ozone (or tropospheric ozone) is an atmospheric pollutant. The EPA also researched the implications of stratospheric ozone depletion. These limits were attempts to reduce ozone pollution. Increased surface UV leads to increased tropospheric ozone. Ventilation with outdoor air containing elevated ozone concentrations may complicate remediation attempts. Energy changes in UV irradiance involved in production and loss of ozone have atmospheric effects. A strong smell of ozone and nitrogen oxides will occur in the area. VOCs contribute to the formation of Tropospheric ozone and smog. Halothane also contributes to ozone depletion. NOAA data is also relevant to the issues of global warming and ozone depletion. It was replaced with R-134a refrigerant, which has no ozone depletion potential. This cancer connection is one reason for concern about ozone depletion and the ozone hole.