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.
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Styler partnered with Environment Hamilton on the study, which was 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.
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"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."
