Levels of the airborne pollutant ozone in the capital exceeded Italian air quality standards four times in the last week of June, according the Agenzia Regionale per la Protezione Ambientale del Lazio (ARPA). Italian law fixes the maximum acceptable level of the airborne pollutant at 180 micrograms per cubic metre (mcg/m3). Levels registered by ARPA reached 208 mcg/m3 on 23 June, 183 mcg/m3 on 24 June, 187 mcg/mc3 on 25 June, 202 mcg/mc3 on 28 June and 183 mcg/mc3 183 29 June. While there is currently no data for the first week of July, slightly lower temperatures and greater cloud cover are expected to keep ozone levels with regular limit. In the meantime, city officials are recommending that children, the elderly and, in particular, people suffering from respiratory dysfunction remain indoors between 12.00 and 18.00 and drink plenty of water.

Ozone (O3) is created when other airborne pollutants like car exhaust come in contact with high volumes of ultraviolet rays. While forming an important protective layer of the stratosphere, ozone at lower altitudes is considered a pollutant by the World Health Organisation and poses serious health risks in quantities above legal norms.