Trucks Hauling Frac Sand Not a Source of Lung-Disease Dust, Data Shows

Just-released state data is just the starting point for understanding the risks posed to the region's air by the growing silica sand industry.

A frac sand mine run by Superior Silica Sands in Wisconsin, the nation's largest frac sand producer. Neighboring Minnesota is the fourth-largest producer of silica sand. The town of Winona has the highest density of frac sand facilities in that state and has become a hotbed of activism. Credit: Jim Tittle/

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Trucks hauling mounds of sand into the southern Minnesota town of Winona for delivery to drilling sites across the nation’s shale regions are not spewing dangerous dust emissions into the air, preliminary data shows.

This data was released early this month, from a monitor for crystalline silica dust, or frac sand, a known trigger of lung disease. The instrument was placed along Winona’s busy truck route at the start of the year in response to local concern.

Dust reached detectable levels only two out of the 38 days measured during the last seven months, according to air regulators at the Minnesota Pollution Control Agency (MPCA).

Even when the dust was detected, once in June and another time in August, the levels were very low, according to Jeff Hedman, an MPCA engineer involved in the study. “We’re happy to see it,” he said.

Many Winonans, including planning commissioner Ken Fritz, are relieved by the data. “I certainly think there is enough evidence out there that [shows] silica sand can create health problems in certain environments…in this case, basic information doesn’t indicate any problems,” he said.

The silica monitor sits atop a two-story YMCA building downtown and was set up to capture emissions from frac trucks. But Winona’s potential dust emissions can come from more than just trucks hauling sand, there are also mining and processing facilities in town. Some citizens who live near those facilities have asked, “How do you know that you are meeting the [air] standard in my backyard?” said MPCA air monitoring unit supervisor Rick Strassman.

According to the MPCA, this data is just the starting point for understanding the risks posed to the region’s air by the growing silica sand industry.

Minnesota is the nation’s fourth leading producer of pure silica sand, according to the U.S. Geological Survey. The nation’s top producer, Wisconsin, is just next door. Both states host vast silica reserves and have expanded their developing of the sand in recent years to keep up with growing demand from energy companies.

Active silica sand facilities between the two states have ballooned from less than 20 in 2010 to over 100 today.

Winona is ground zero for Minnesota’s frac sand boom. It has at least six active sand mining, processing and transport facilities, the highest density in the state. About 100 trucks arrive daily from in and out of state. All that sand is then shipped by train or barge to frack sites across the country. Operators blast the hard, round sand down wells to break and hold open cracks in the bedrock to extract oil and gas reserves. It can take up to 10,000 tons of sand to frack a single well during its lifetime.

Scientific studies have detailed the effects of silica dust—particles that are small enough to enter lung tissue and the blood stream and trigger the lung disease silicosis—on workers handling the material, but not on neighboring communities. Winona’s government-funded monitor, the first in the state not paid for by industry, was added to chip away at that scientific gap.

The data recently released comes from a monitor targeting concentrations of particulate matter up to 4 micrometers in diameter, called PM 4. These specks of dust are 20 times smaller than beach sand. The dust accumulates in the monitor’s filter. Samples are collected over a 24-hour period every six days and then sent to a New York lab for what’s called “speciation” analysis to calculate how much of the collected material is frac sand. Afterward, the processed data is sent to back to Minnesota, where it is checked by state regulators and published online.

So far, over seven months of data have been processed. Most observed days, levels were below the detectable amount. When dust was detected, it was less than 0.5 micrograms per cubic meter. The chronic health benchmark used by the MPCA is six times higher—3 micrograms per cubic meter. 

The monitor will continue collecting data through the year’s end.

A second Winona monitor atop the YMCA measures even smaller particles in the air from all sources in town, not just frac sand. The data it collects requires minimal processing and has been available for months.

“The silica data is really good news,” said Crispin Pierce, a University of Wisconsin-Eau Claire professor of environmental public health. He has studied silica emissions across Wisconsin and Minnesota.

Still, Pierce said, it’s important not to jump to conclusions and “to measure the whole year through to see any trends.”

For some residents, including Jane Cowgill, the monitor’s results are promising but don’t provide the full picture for Winona. Cowgill, co-founder of the local grassroots activist group Citizens Against Silica Mining, points out that there are a handful of frac sand mine and processing sites on the outskirts of town.

“If you are living at the [air monitor] building, you are probably OK,” she said. But if you are near these other sites, she noted, there is anecdotal evidence of a problem—”cars covered with dust, furnaces all clogged up, and reports of respiratory problems.”

The only way to fully understand Winona’s frac sand air risk is to set up monitors at the edges, or fences, of these other facilities, she said. She calls the strategy “fenceline monitoring” and is part of a group lobbying the City Council to approve more monitoring.

Ken Fritz is one of the city officials who voted down a proposal this summer to approve additional monitors. He wanted to see the current monitors’ data before making the decision. Now that the data is available, he’s still convinced no further monitors are needed.

Minnesota regulators said the active monitors aren’t sufficient to capture the entire town’s silica sand air risk. Additional “monitoring is still warranted, but that’s really the city’s call,” said MPCA’s Strassman.