What a day! #NationalCleanAirDay trended at 1 on UK twitter for 5 hours on National Clean Air Day 2017, reaching 38million people! On 15 June, National Clean Air Day caused a buzz across the U.K. Thousands of people got involved in schools, businesses, hospitals and communities - making pledges, going car free and raising awareness of air pollution. With our Thunderclap alone, we reached 3.4 million people with our air quality message. Here are some of our favourite tweets, photos and stories from the day: [View the story "National Clean Air Day" on Storify] Thank you to everyone who helped to make National Clean Air Day such a success!