The hidden toll of July Fourth fireworks

Using crowdsourced data from home air quality monitors, scientists found that vulnerable people and communities of color are disproportionately exposed to air pollution from firework celebrations.

It’s no secret that fireworks can cause some serious air pollution, in the United States as well as in other countries where holiday displays are common, like China and India. But not everyone is equally at risk from the noxious particles that suffuse the sky during our pyrotechnic light shows. In California, for example, vulnerable populations are more exposed to fireworks pollution on the Fourth of July.

That’s according to a recent study published in the International Journal of Environmental Research and Public Health on air pollution exposure across the state due to Independence Day fireworks. At its peak, the smoke from these events can be comparable to that from wildfires, the study found. The authors also showed that fireworks smoke may be creating an additional—albeit short term—health risk for communities already disproportionately burdened by air pollution: Urban ones with higher rates of asthma, more older residents, and a greater percentage of children under 10. These areas also tended to have more Black and Hispanic residents than those with less Fourth of July air pollution.

The high-risk communities identified in the study have “perpetual exposure to hazardous environmental toxins,” says Aisha Dickerson, an environmental epidemiologist at Johns Hopkins University who wasn’t involved with the paper. “This aggravates an already prevalent and persistent issue.”

Where there’s fire, there’s smoke

Fireworks don’t just produce colorful, crackling light displays: They also create puffs of smoke. What’s less widely known is that the smoke can be dangerous. Fireworks smoke includes particulate matter—an asthma trigger and a leading contributor to respiratory disease—as well as a cocktail of toxic metals like strontium, barium, and lead.

And while the pollution from a single fireworks display tends to dissipate quickly, many fireworks being set off over the Fourth of July can cause regional air pollution levels to spike and remain elevated for several days, posing a potentially serious health risk to vulnerable populations.

“There are very few studies that have looked at the association between fireworks related air pollution and health,” says Pallavi Pant, an air pollution researcher at the nonprofit Health Effects Institute who has studied pollution during festivals. “However, the concentrations can be high enough to trigger health effects, especially for children and older adults and those living with respiratory diseases.” 

Not much is known about who is most exposed. Most research on Independence Day fireworks pollution has relied on sparse, EPA-run air-quality stations that can reveal only trends at a regional scale.

Crowd-sourced data

For the new study, the UC Irvine-based team of researchers took advantage of the recent proliferation of home air-quality monitors to explore how Fourth of July fireworks pollution varies across communities in California. The scientists analyzed publicly crowdsourced data from 751 commercial PurpleAir sensors in private residences across the state during June and July of 2019 and 2020.

In both years, the team looked at county and census district-level patterns in fine, inhalable particles less than 2.5 micrometers across, called PM2.5. To determine whether certain populations are more exposed to this pollution, the researchers compared the 2019 results with state-reported data on racial demographics, socioeconomic status, health indicators, and more.

The researchers found that Fourth of July fireworks pollution, although transient, can be significant. In Orange County, hourly levels of PM2.5 rose up to three times higher than normal on July 4, 2019, while Los Angeles County pollution levels soared up to 10 times higher than average on July 4, 2020. The festivities in the L.A. metro area last year produced as much smoke as a moderate wildfire.

Vulnerable populations appear to be more exposed to this pollution: On average, the authors found that PM2.5 spikes around the Fourth of July were higher in urban census tracts in Southern California, areas that tend to have higher asthma rates, more older individuals and small children, and more Black and Hispanic residents, compared with rural census tracts and those further north. Southern California metropolitan areas also tend to have fewer restrictions on municipal fireworks shows and looser oversight of at-home fireworks use compared with their counterparts in Northern California.

“L.A. has less stringent policies regarding bigger fireworks shows and purchases by residents,” says Jun Wu, a professor of public health at UC Irvine and the senior author on the study.

Dickerson says she’d expect to see a similar pattern of exposure to fireworks-related air pollutants elsewhere around the country.

“A lot of the fireworks displays typically happen in the bigger cities, especially along coastal communities, and lower income [minority] communities typically are closer to those ports,” she says.

Compound threats

The consequences of poor enforcement of fireworks regulations were laid bare last Fourth of July, when the cancellation of municipal fireworks displays due to the coronavirus pandemic prompted many people to purchase online and shoot off illegal fireworks, including bottle rockets and aerial shells at home. (In California, only non-aerial fireworks like sparklers are allowed for at-home use.) As a result, fireworks pollution was elevated across California in 2020 compared with 2019. Considering the established link between air pollution and more severe COVID-19 outcomes, Wu says last year’s pyrotechnics might have worsened the pandemic.

She’s expecting this Fourth of July to also feature higher levels of at-home, illegal fireworks activity, noting that in her neighborhood, she’s been hearing telltale explosions for the last few days. Elsewhere in the state, residents have been complaining to authorities about fireworks noise for weeks, according to the New York Times.

Compounding the risks of fireworks this year, much of the West is currently in the grips of a historic drought, while the Pacific Northwest and parts of Canada are emerging from a record heat wave. These conditions have primed the West for wildfires—and each year, Fourth of July fireworks celebrations are one of the most predictable sources of ignition. Wildfires also produce dangerous smoke, notes Michael Kleinman, an air pollution researcher at UC Irvine who wasn’t involved with the paper.

“While these [wildfire smoke] spikes are not as intense as the fireworks spikes, they now occur nearly year-round,” Kleinman wrote in an email. “These can in turn elicit increased incidences of severe health effects for sensitive or susceptible individuals.”

Given all the risks, Wu suggests it’s time for city and local governments to more aggressively crack down on illegal fireworks—something several California cities are attempting to do this year—and consider shifting to other types of public displays, such as drone light shows. Individuals susceptible to air pollution can limit their exposure on the Fourth of July by wearing masks or watching the show from indoors, Wu says.

Dickerson agrees that masks are a “reasonable and feasible public health measure.”

“Wearing a mask is not this foreign concept anymore,” she says.

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