The study compared PM2.5 concentrations on July 4 with days preceding and following the holiday. It found PM2.5 concentrations peaked around 9-10 p.m. on July 4 at more than twice their average before dropping back to background levels by around noon on July 5.
At two observing sites co-located at McMillan Reservoir in Washington, D.C., about 3 miles north of the National Mall – the site of a massive fireworks celebration, the average PM2.5 concentration on July 4 was about 40 percent higher than average. Between about 8 and 10 p.m., PM2.5 levels surged by over 400 percent (compared to average) before gradually returning to background levels the next day.
In Ogden, Utah, fireworks’ impact on PM2.5 levels was even stronger, increasing the daily average concentration by 370 percent on July 4 and the peak level at 10 p.m. by over 3700 percent
“The study is … another wake up call for those who may be particularly sensitive to the effects of fine particulate matter,” said Dian Seidel, study lead author.
Health studies show these particles, whose diameter is about 1/30th the size of a human hair, “have shown a significant association between exposure to fine particles and premature death from heart or lung disease”, the Environmental Protection Agency (EPA) said. They are known to aggravate asthma and other respiratory problems.
EPA rules accommodate the July 4 tradition by allowing short-term spikes in PM2.5 if states can demonstrate the source was fireworks.
“Wile the EPA does not regulate fireworks, the agency does recommend that people who are considered sensitive to particle pollution try to limit their exposure by watching fireworks from upwind – or as far away as possible,” a NOAA news summary said. “People with asthma should follow their asthma action plans and be sure to have their quick relief medicine handy.”