As London rethinks backyard fireworks, studies suggest they can be as bad for the air as wildfire smoke

As London rethinks its rules around backyard fireworks, a number of U.S. studies suggest smoke pyrotechnics can be as bad for the air and our health as smoke from the raging wildfires that have burned out of control this summer, blotting out blue skies and triggering hundreds of air quality warnings across North America.

This year is officially the worst wildfire season on record, burning approximately 13.4 million hectares as of August, a charred wasteland equivalent in size to the provinces of Nova Scotia and New Brunswick combined.

At the same time, smoke from those fires has blanketed even larger areas, triggering air quality warnings across eastern Canada and the United States. 

As London mulls a partial, or even a full ban on the sale of backyard fireworks like its neighbour Woodstock, city officials might want to consider how such displays contribute to air pollution, especially after London declared a climate emergency last February.

Pollution heaviest near display fireworks

"It's really just a layering on more and more stuff in the atmosphere," said Dian Seidel, a retired scientist with the National Oceanic and Atmospheric Administration in the United States.

In 2015, she authored the first known study looking at how fireworks affect air quality in terms of pollution of fine particles, or PM2.5, in the 24 hours during and after American Independence Day on July 4th. 

"These are the very fine particles that can get lodged deeply into our lungs and not be expelled when we exhale. So they're dangerous particles and that's why they're monitored," Seidel said. 

To do it, the study looked at 315 long-term air monitoring sites operated by federal and state-level environmental monitoring agencies across the U.S. and found that, on average, the concentration of PM2.5 increased by 5 to 21 μg/m3, an average by 42 per cent within the 24 hours after the July 4th holiday. 

One site directly adjacent to fireworks shows saw PM2.5 levels spike by as much as 370 per cent in the 24 hours after the July 4th display, the equivalent of 500 μg/m3 — a level considered by most jurisdictions to be hazardous to human health.

"That site to me is more indicative of what would happen if you went, for example, to a park or to a beach or someplace where there was going to be a display and plunked yourself down to get the best view.

"You could get a pretty big dose," she said. 

Levels of arsenic, lead rose 'modestly' study finds

Another U.S. study published in 2016 looked at what exactly makes up that "dose."

The study found that in the 24 hours after fireworks go off, PM2.5 levels of barium, chlorine, copper, magnesium, strontium and potassium in the air increased "dramatically," while PM2.5 levels of aluminum, arsenic, antimony, chromium, lead, sulfur, titanium and zinc in the air increased "modestly."

Seidel said where she lives in Washington D.C., smoke from Canadian wildfires forced her hometown to declare its worst air quality day ever in July — the same month July 1st and July 4th celebrations take place. 

"It created a terrible air, air pollution problem and we were told to stay home indoors as probably you guys were as well. So, would it make sense to add to deliberately add more pollution to the air at a day like that?"

"It's a policy question and I'm not a policy maker, so I won't answer it, but common sense would suggest maybe that's not the smartest thing to do."

What's the 'smartest thing to do?'

"The smartest thing to do" may or may not be one of the two options being considered by a city hall committee on Tuesday, when it hears from 30 delegations on two options  — a full or partial ban on the sale of consumer fireworks in the city: 

• Option A: The sale of consumer fireworks would be allowed five days prior to an allowed event, which includes Victoria Day, Canada Day and Diwali, where backyard displays would be allowed between dusk and 11 p.m.

• Option B: No consumer fireworks to be sold in London. No consumer fireworks allowed to be discharged.

Under both proposals, the city would still allow for display fireworks on Victoria Day, Canada Day, Diwali, New Year's Eve and possibly other days based on a permit. 

London Deputy Fire Chief Matt Hepditch, who compiled the report for the committee, told CBC News Friday that the two options are simply a starting point for community conversation and will in no way constrain the options of politicians making the decisions.