DEQ monitoring finds no evidence of silica dust health risk in Yoder

TORRINGTON — Extensive air quality monitoring conducted by the Wyoming Department of Environmental Quality over the past several years has found no evidence that crystalline silica dust from the Western Proppants facility poses a health concern to Yoder residents, according to state officials.

The findings come as air quality concerns continue to be discussed by community members and were recently raised during a Goshen County School District No. 1 board meeting.

Wyoming DEQ Deputy Director Nancy Vehr said the agency began monitoring air quality in Yoder in response to residents’ concerns shortly after the Western Proppants facility began operations.

Since September 2022, the DEQ’s Air Quality Division has conducted monitoring for particulate matter and crystalline silica using regulatory-grade equipment valued at approximately $150,000.

“We wanted to understand what the actual air quality conditions were,” Vehr said.

The monitoring focused on three primary categories of particulate matter: PM2.5, PM4 and PM10.  PM2.5 consists of extremely small particles commonly associated with smoke and

combustion. PM10 includes larger dust particles, while PM4 monitoring was used to assess the presence of crystalline silica, a concern frequently raised due to frac sand processing activities in the area.

According to DEQ data, PM2.5 levels have remained well within federal health standards.

Between September 2022 and April 2025, the agency collected PM2.5 data over 922 days. During that period, the federal 24-hour standard of 35 micrograms per cubic meter was exceeded only three times. 

DEQ determined all three exceedances were caused by wildfire smoke rather than local industrial activity.

An additional two exceedances were recorded between April and November 2025, according to DEQ monitoring data.

Silica monitoring also showed no indication of a health concern.

Because standard air quality sensors cannot directly measure crystalline silica, DEQ used a PM4 monitor that collected particles on specialized filters. Those filters were then sent to a laboratory for analysis.

Monitoring conducted between November 2024 and March 2025 found silica levels were well below health-based comparison values established by the Texas Commission on Environmental Quality. DEQ used Texas’ guidance because the U.S. Environmental Protection Agency has not established an ambient air quality standard for either PM4 particulate matter or crystalline silica.

“The information that we currently have is that there is not a silica issue,” Vehr said.

While silica and PM2.5 were not identified as concerns, DEQ officials said PM10 remains the pollutant receiving the most attention.

From September 2022 through April 2025, PM10 concentrations exceeded the federal 24-hour standard of 150 micrograms per cubic meter on 19 occasions out of 941 monitored days. One of those exceedances was attributed to wildfire smoke.

Between April and November 2025, two additional PM10 exceedances occurred, one of which was also linked to wildfire smoke.

“We did say on PM10 that we needed to continue to reduce the number of exceedances,” Vehr said.

Because PM10 includes larger dust particles, DEQ officials have continued monitoring those levels while working with the community and facility operators.

Following completion of the intensive monitoring program, DEQ transitioned from regulatory-grade monitors to lower-cost sensor technology.

In August 2025, the agency deployed a QuantAQ Modulair-PM sensor alongside its existing monitoring equipment to compare results. The comparison found the sensor tended to read approximately 1.56 times higher than the regulatory-grade PM10 monitor.

Despite that bias, officials said the sensors provide valuable real-time information and allow broader monitoring coverage at a fraction of the cost.

The PM10 and PM2.5 sensors remain active at Yoder and Southeast Schools.

The sensor at Southeast Schools was installed after school officials contacted DEQ regarding concerns expressed by parents.

“The school contacted us and said there are a lot of parents who are concerned about silica dust,” Vehr said.

The sensors allow residents to view current and historical air quality information through DEQ’s WyVisNet monitoring system.

Vehr said one challenge facing regulators is helping the public understand what air quality numbers actually mean.

To simplify the information, DEQ uses color-coded categories developed by the EPA. As with traffic lights, green indicates good air quality, while yellow, orange and red indicate increasing levels of concern.

“What people really care about is, ‘Is the air healthy and safe for me to breathe?’” Vehr said.

In addition to monitoring activities, DEQ issued Notice of Violation No. 6264- 24 to Western Proppants in 2025. Vehr said the Air Quality Division remains in discussions with the company to resolve the violation.

The agency has also held multiple public meetings in Yoder over the past several years to share monitoring results and answer residents’ questions. Attendance at those meetings has generally ranged from 20 to 40 people.

During a meeting with Yoder officials this week, DEQ representatives reiterated that they are willing to hold additional public meetings, provide tours of monitoring equipment and answer questions from community members.

“We think it’s fantastic that people are asking questions,” Vehr said. “Sometimes people just don’t know where to go to get the information.”

Residents can view current air quality data through the WyVisNet monitoring network and access permits, monitoring records and compliance documents through DEQ’s OpenAir database.

Vehr emphasized that the absence of current concerns does not mean monitoring efforts will stop.

“That doesn’t mean there can never be any concerns,” she said. “It means we keep our eye on things and we take action when it’s warranted.”

DEQ officials encouraged residents with questions about air quality, monitoring results or health concerns to contact the agency directly or review the publicly available information online.

This story was published on June 26, 2026.

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