Research lags on residential exposure to dust from sand, gravel mines
At a township meeting in a small Northern Michigan community, Bay Shore residents raise health concerns about the resumption of gravel mining near their homes.
In addition to worries about traffic, noise, groundwater contamination, there’s another common concern:
“Silica dust is actually equivalent to asbestos.” “Silica dust is fatal if it's inhaled in in the sustained quantities.” “...silica, is that the cause of my asthma?”
The company in charge of mining, Rieth-Riley, heard those concerns. And this was their response at a March township meeting:
“I know there's issues about silica dust," said Jim Pemberton, a local project manager for Rieth-Riley. "That seems to be the big clamor, but the bottom line is natural sand and gravels are not a source of silica dust."
He said crushing gravel will happen off-site, and the company will use dust suppression methods at the mine – like spraying the pit with water and tarping trucks.
These are standard practices in aggregate mining to prevent what’s called fugitive dust.
Pemberton said if natural silica was an issue, "with Sleeping Bear Sand Dunes, we'd have the biggest problem in the state of Michigan, yet that’s one of our gems in Northern Michigan."
Mike Wilczynski, a retired state geologist who consults residents fighting aggregate mines, said that’s misleading.
He said while it’s true the sand in Sleeping Bear Dunes has silica - it’s a type of quartz - mining can break up those natural, large, and generally harmless crystals into microscopic, sharp-edged dust.
Exposure to silica dust can result in silicosis, a severe, uncurable lung disease. It's a concern for workers in fields like construction, mining, and manufacturing, and state standards are meant to limit workplace exposure.
Wilczynski said the issue is the data gap in assessing community exposure, like what residents may face living next to mines.
“We really don't know that much about the non-occupational exposure to the material," Wilcyznski said. "We know what levels are safe, but how much are people breathing in from these operations [in their homes]?”
Sandy McCoy is a Grass Lake resident in Jackson County.
“I saw grown men begging the township not to renew this mine’s permit, for the safety and health of their families,” McCoy said.
After her township renewed a permit for a gravel mine on Bohne Road despite years of residential health concerns, she first went to the state’s air quality division.
“I had gone into a couple of the homes over there to see the dirt and dust," McCoy said. "And Mike [Wilczynski] was of the opinion that it was consistent with silica dust. We asked EGLE to analyze it, and they said they wouldn't.”
This prompted McCoy to write a letter to the state health department, requesting an exposure assessment.
She wrote how Grass Lake residents living near the mine aren’t able to open their windows or spend time outside due to high levels of visible dust.
“I heard back right away, actually," McCoy said. "I was very excited, I thought, finally, there's someone that will listen and try and do something about it.”
McCoy said her excitement soured when she learned air sampling would only last a few weeks.
“My biggest fear was that they might take that week of sampling and try to form conclusions from it, and I just- you can't do that,” she said.
The state health department sampled for two weeks in August and September and a week in October. The report is still undergoing review, but Joost vant’Erve, a toxicologist who worked on the study, said air monitors placed near residents’ homes did not pick up any silica in the air.
“We didn't find anything really alarming. It's very difficult with these testings, but definitely no silica..." van't Erve said. "We did find regular dust might have exceeded some health standards, so we went back the next year...”
van't Erve said the goal of sampling was to assess if there were huge day-to-day changes in air quality. Since there weren’t, he said the two rounds of monitoring supplied enough data to estimate a yearly average, biasing the results toward windier and drier conditions.
The study was modeled around an assessment from Illinois that looked at silica exposure near a sand mine over 8-weeks and lined up with a prior year-long assessment conducted by the Environmental Protection Agency.
van't Erve said the results from Grass Lake were similar, but he’s careful not to generalize the findings.
“It's definitely encouraging that those studies find that there's no breathable silica there," van't Erve said. "If conditions around the mine are the same, it would be more general. But there could be some site-specific things that are preventing it from being applied everywhere.”
The science on residential air pollution from mining is still dusty. There’s only a limited body of literature that attempts to answer this question.
The Michigan Aggregates Association could not be reached in time for publication of this story. Industry representatives have said resident concerns on dust are false and used to justify baseless opposition to mining operations.
Residents say they don't want dust to be a problem, they’d just like to see more evidence guaranteeing their safety - and be able to comfortably open their windows.