Historical clue formulations

• Ozone no-no, for short — 2026-01-04
• Banned refrigerant, for short — 2021-05-07
• Freon initials — 2019-10-14
• Banned aerosol propellant, for short — 2019-07-07
• Banned pollutant, for short — 2018-04-06
• Freon letters — 2015-07-10
• Refrigerant inits. — 2013-08-15
• Freon initials — 2010-11-13
• Ozone hazard, for short — 2010-05-22
• Ozone depleter, for short — 2006-06-12
• Environmental hazard, for short — 2000-06-04