Washington briefly became the world’s most polluted major city after a massive Independence Day fireworks display promoted by the Trump administration sent thick smoke across the US capital. Air quality monitors recorded hazardous pollution levels that lasted for several hours before heavy rain cleared the smoke. According to Swiss air quality monitoring company IQAir, Washington ranked as the world’s most polluted major city between about 3am and 5am on Sunday, July 5. The pollution spike followed the Freedom 250 fireworks celebration marking America’s 250th anniversary. The city has since returned to normal air quality levels. The White House’s Freedom 250 organisation hired Pennsylvania based fireworks company Pyrotecnico for the event. The company aimed to break the Guinness World Record by launching more than 850,000 fireworks within 40 minutes. The current record stands at about 811,000 fireworks and was set in the Philippines on New Year’s Day in 2016. The celebration took place during a record breaking heat wave that disrupted July 4 festivities across much of the United States. A thunderstorm delayed the main fireworks display by more than an hour. The show eventually started shortly before midnight. Air pollution reached hazardous levels Washington’s pollution monitors began detecting rising pollution around 8pm as smaller neighbourhood fireworks displays started. Air quality worsened sharply after the main show began. Thick smoke drifted across the National Mall and reduced visibility for many spectators. City monitoring data reviewed by AFP showed PM2.5 concentrations climbed above 200 micrograms per cubic metre at one monitoring station. These tiny particles can travel deep into the lungs and bloodstream. The US Environmental Protection Agency recommends that average exposure over 24 hours should not exceed 35 micrograms per cubic metre. The deteriorating air quality triggered “Code Purple” alerts across Washington as well as parts of neighbouring Virginia and Maryland. The warning indicates air quality is very unhealthy for everyone, not only for vulnerable groups. Before the event, health experts warned that such a large fireworks display could create dangerous pollution levels. Internal National Park Service assessments also advised people to reduce outdoor activity and consider wearing high filtration masks if smoke became heavy. EPA defends fireworks as scientists warn of risks Despite the pollution spike, the Trump administration defended the event. Asked for comment, EPA press secretary Brigit Hirsch told AFP: “Fireworks are awesome and we hope everyone enjoyed the incredible shows in and around our nation’s capital to celebrate 250 years of America.” Scientists said weather conditions prevented a more serious pollution event. “We dodged a bullet. It was very bad, but it could have been substantially worse,” Russell Dickerson, an atmospheric scientist at the University of Maryland, told AFP. Heavy rain and shifting winds cleared much of the smoke by around noon on Sunday. Air quality across Washington returned to normal later that day. Guinness record attempt awaits confirmation Pyrotecnico has not yet secured the world record. A Guinness World Records spokesperson confirmed the organisation received an application from the Washington event. Officials still need to review the evidence before making a final decision. “At this stage, we are not able to confirm whether the record has been achieved. We will only be able to do so once the evidence has been submitted and fully reviewed by our Records team.” The event has renewed debate about the environmental and health impact of increasingly large fireworks displays. Scientists say such events can cause short term spikes in dangerous air pollution, especially during hot weather when smoke remains trapped over cities.