The Minnesota Pollution Control Agency has released preliminary results of air monitoring in Winona.
The MPCA placed air monitors at the Family YMCA in Downtown Winona in January of 2014, and have been collecting hourly data on fine particles and crystalline silica since.
According to the preliminary results, the period of collection is not yet sufficient for a true comparison to the ambient air quality standards.
But between January 1st, March 31st, the only incidence where the daily fine particle standard was exceded was once. The MPCA says that occurred on March 7th, and was the result of a regional weather pattern that included a strong temperature inversion, light winds, and heavy fog.
Due to the nature of that event, the MPCA does not believe fine particles from silica sand operations caused the standard to be exceded.
Breathable silica samples are being collected in Winona once every six days by a second monitor, but they have not yet been analyzed according to the MPCA.