Soot falling across Hamilton contains toxic chemicals linked to burning coal, researchers find

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A team of researchers in Hamilton has answers to questions about the soot falling on neighbourhoods near the city’s industrial sector.

For decades, residents have complained about a grimy, black substance coating their properties. The perennial issue came up again in early July, when residents experienced what some described as the worst fallout in recent memory.

Sarah Styler, an associate professor of environmental chemistry at McMaster University, and Grace Yao, a PhD candidate in Styler’s lab, are part of the study “What’s the Grime?” that seeks to answer the titular question.

Working with volunteers to collect samples throughout the city, the researchers found the soot contains toxic chemicals consistent with coal combustion. They also found amounts of dust and polycyclic aromatic hydrocarbons (PAHs) were higher near the industrial area in northeast Hamilton.

WATCH | Hamiltonians wonder what’s in the soot:

People in several Hamilton neighbourhoods still don’t know why black soot has been falling on their homes

People living in and around Hamilton’s east end say their homes have been covered in black soot this week. Soot is not a new concern for people in the area, but Ward 4 councillor Tammy Hwang says this time is different, with people further away being affected.

Styler partnered with Environment Hamilton on the study, which undertaken with a $15,000 grant that the university awarded her in 2024.

Living in east Hamilton, Styler said, she has first-hand experience with the soot; Yao said that’s the case with her as well, in Corktown.

“It’s been a known issue for a really long time,” Styler said.

She noted that as part of their research, Yao found reference to the soot in news archives going back at least the 1950s.

The study involved using sampling kits to collect soot at the homes of 50 volunteers throughout the city. Scientists took samples from each kit at four-month intervals, then analyzed them.

“Closer to the industrial sector, more dust is falling,” Styler said. “And closer to the industrial area, there are more of this toxic class of compounds.”

An update the team posted to the Environment Hamilton website Monday also noted PAH levels were higher in the winter than in the summer.

The team studied 13 different PAHs, Styler said, but those compounds aren’t the only toxic substances that could be in the grime, which she described as a “gloopy mess.”

Due to resource limitations, the study couldn’t look at everything in the grime, Yao said, meaning it’s possible other sources are contributing to the fallout. Still, “coal combustion is particularly significant in creating the PAHs that we’re talking about.”

Styler’s team can’t make conclusions about which industrial-specific sources are creating the PAHs, she said, but with more monitoring and “analytical firepower,” one could.

Findings likely seem obvious: Styler

These findings aren’t likely to surprise anyone who lives in the neighbourhoods that primarily experience the fallout, Styler said. It seems obvious that the substance affecting people who live near coke plants comes from industrial emissions, she added.

However, locals have been frustrated by a perceived lack of information from official sources, Styler said.

On July 28, Alexandru Cioban, a spokesperson with the Ministry of the Environment, Conservation and Parks, told CBC Hamilton that the ministry was continuing “the necessary testing as we assess operations at industrial facilities in Hamilton’s north end to determine a likely source.”

Cioban said the ministry will publicly share the results of its testing, and added that in 2024, ministry testing indicated particulate at that time was predominantly road dust.

CBC Hamilton followed up with the ministry for this article, asking when it might share its findings and for more information about how it conducts its tests. The ministry did not respond before publication time but will update the story with any response.

An adult holds up a young child whose feet are covered in a black substance. — Hamilton resident Ali Kellner says her son became covered in black grime after playing outdoors in early July. CBC blurred the photo of the boy’s face at his mother’s request to protect his identity. (Submitted by Ali Kellner)

Styler said her team’s research doesn’t support that the soot is mostly road dust.

She said their sampling backs up what the community has been saying “forever, more or less” — that the soot is an industrial byproduct.

The associate professor said it’s important to note that her team’s research doesn’t make people’s lived experience any more real than it was before. “It’s always been real.”

The researchers are hosting a community meeting on Aug. 20 to report their results. They’ve worked on a manuscript they’re submitting for peer review, and say they’ll share more of their findings once that process is complete.

They’re also looking to expand their study from 50 to 200 volunteers, and to examine more compounds within the grime. Styler said another area of interest they’d like to explore is how best to clean it.