Air quality in the Valley fails to meet the national standard for clean air, and that means we are exposed to unsafe levels of ozone in the air we breathe. Working to improve the air of Maricopa County so customers, residents, and visitors can live, work, and play in a healthy environment.Learn about EPA's efforts to address ozone layer depletion through international treaties and initiatives. Handbook for the International Treaties for the Protection of the Ozone Layer. The Vienna Convention for the Protection of the Ozone Layer (Vienna Convention) was agreed in 1985. The Protocol sets out a mandatory timetable for the phase out of ozone depleting substances.