Indianapolis' large downtown fireworks display might have been canceled this year, but in many Indy neighborhoods and other local cities, the show went on — and the fireworks went off.
The sky over places such as Carmel, Lebanon, Noblesville, Cicero and Moorseville filled with colorful bursts of light. And also, in some cases, smoke, which can make it harder to breathe, especially for individuals with asthma and other respiratory conditions.
Particle pollution, or particulate matter, comes in two main sizes: PM10, short for particulate matter with a diameter of 10 micrometers, is the size of some types of pollen or mold. And PM2.5, particles with a diameter as less than 2.5 micrometers, are as fine as 3% the diameter of a human hair.
The source of those finer air pollutants is mostly related to human activities, such as driving cars, house heating, factory emissions, and occasionally, fireworks.
As they illuminated the sky on July 4, levels of PM2.5 increased as well.
Most cities did not exceed the EPA’s National Ambient Air Quality Standards limit for fine particulate matter during the 24 hours when fireworks were launched for Independence Day. Still, the national average concentration was 42% higher than the days before and after the holiday, according to a 2015 analysis of 315 cities across the country.
Display fireworks organized by cities and counties might be expected to be responsible for most of this air pollution, but money suggests otherwise. According to the American Pyrotechnic Association, consumer fireworks that can be bought at grocery stores, generated $1 billion in revenue in 2019. That is well above the $375 million that came from display fireworks, the association said.
According to daily data from the Indiana Department of Natural Resources, particulate matter concentration exceeded the 24-hour limit of 35 micrograms per cubic meter on July 4 this year in downtown Indianapolis and remained very close to the limit the next day — unlike last year where levels both days remained under the limit.
The mix of warm and humid air this year are also responsible for the increased levels of particulate matter seen during the holiday.
“The main peak occurs around 10 at night on July 4, and then continues on as particulates slowly get scrubbed out of the air," said Gabriel Filippelli, director of the Center for Urban Health at Indiana University-Purdue University Indianapolis. "Last year that peak was more obvious because the air quality was better. This year air quality, starting probably at the beginning of July, has been getting a little bit worse, because the heat has increased and that's made some of the particulate matter a little bit worse.”
In most cases, temperature decreases with altitude, meaning air gets colder in the upper parts of the atmosphere. Sometimes the opposite happens: Cold air remains closer to the ground than warm air. The cooler air, along with air pollutants like fine particulate matter, gets trapped by the lid of warmer air above. This is known as temperature inversion.
“Humid days also tend to be indicative of an inversion layer," explained Filippelli, "which just effectively traps these fine particulate particles near the ground level.”
Similar situations have been reported in Los Angeles and Denver. According to the LA Times, “this year, the PM2.5 pollution appeared to be more concentrated and linger for longer even compared with past holidays.” Since fires are also sources of these fine contaminants, they could also be driving this increase on the West Coast.
In addition to EPA and DNR monitors, Filippelli uses data from a network of 32 sensors he has set up on people’s homes on the east side of Indianapolis. These sensors came from a partnership with Keep Indianapolis Beautiful that used funds from the Indiana University's Grand Challenge. People become a network of citizen scientists and learn something about the air around their neighborhoods, while scientists “learn for the first time what the micro fabric of air pollution in Indianapolis is,” he said.
These microfabric estimates allowed Filippelli to see minute-by-minute changes in particulate matter concentration in the days leading up to the July holiday.
“Pretty much the biggest sustained peak for the last week was the night of the Fourth of July," he said. "It went up to unsafe levels. From the morning of the Fourth to the evening, it increased by about five times in terms of particulate matter.”
The minute particles that stick around in the air after the lights go off are the result of a combustion process from fireworks burning. The inner workings of these devices depend on three basic components: oxidizer, fuel, and mineral pellets, responsible for the colors.
One might think that given their weaker explosive power, consumer fireworks are less harmful. But the burning of metal and mineral salts found in firecrackers, artillery shells, or poppers are bad both for the environment and lungs.
Researchers from the Department of Environmental Medicine at New York University burned 12 types of fireworks in a steel chamber, and collected the particulate matter that usually remain in the air. They exposed human lung and bronchial cells grown on an artificial medium as well as mice to the debris they collected.
They wanted to see if this seemingly inoffensive dust was capable of swelling cells — or creating a negative and inflammatory response. They found that the amount and effects of particulate matter on cells vary depending on the type of firework. The most harmful fireworks contained high amounts of copper and lead, the research showed, which caused the greatest swelling response in mice.
The finding of lead in the Black Cuckoo and one type of Saturn Missiles fireworks was surprising to Terry Gordon, professor at the Department of Environmental Medicine at NYU and last author of the publication.
Lead is prohibited in the fabrication of fireworks according to the American Pyrotechnic Association standard and by the American Fireworks Standard Laboratory.
When it comes to choosing fireworks, Gordon recommend sticking to simple lights and staying upwind. “If I had a family (and) were outside," he said, "sparklers don't raise the concern with me because they usually burn magnesium.”
Lorena Villanueva-Almanza is the 2020 AAAS Mass Media Fellow at the Indianapolis Star. She earned her PhD from the University of California Riverside in 2019 where she studied the taxonomy and ecology of Washingtonia, a group of palms found in southern California and Baja California, Mexico. She’s on Twitter as @lorevial.
IndyStar's environmental reporting project is made possible through the generous support of the nonprofit Nina Mason Pulliam Charitable Trust.
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