APPLETON — People living near industrial silica sand facilities can breathe easier knowing a new, authoritative, peer-reviewed scientific study monitoring air quality at four frac sand facilities in northwestern Wisconsin has found these facilities have minimal impact on air quality in surrounding areas and do not pose a threat to nearby residents’ health.
As the number of industrial sand mines grew from just a handful in 2009 to 63 active mines in the span of a few short years, nearby residents, local and state officials, and state regulators expressed concerns about the potential for these mines to generate hazardous levels of silica particles small enough to make their way into the deep tissue of lungs.
These particles, known as respirable crystalline silica (RCS), measure four micrometers in diameter and are also referred to as PM4. If present in high enough concentrations for a long enough period, RCS can cause silicosis, a very serious but preventable lung disease that occurs in professions such as sandblasting, construction and mining.
Though RCS is an occupational hazard, the study, which took more than 2,100, 24-hour samples over three years, concluded these facilities are not a threat to public health because concentrations of RCS monitored at the fence lines of these facilities are far below levels considered harmful by the California Office of Environmental Health Hazards Assessment (OEHHA) and the Minnesota Pollution Control Agency (MPCA).
Average RCS concentrations were less than 10 percent of the chronic reference exposure limit of 3 micrograms per cubic meter (µg/m3) adopted by OEHHA and MPCA. RCS concentrations were so low they could not even be detected on 88 percent of the 2,128 samples taken. These results are similar to the findings of studies by MPCA, which were unable to detect RCS in more than 94 percent of the sample dates, demonstrating industrial sand facilities are not a source of dangerous concentrations of air pollutants.
Another important aspect of the study is the upwind-downwind analysis. By having monitors placed upwind and downwind of the facilities in the directions of the prevailing winds, the researchers were able to establish a baseline for RCS concentrations in the air and determine how much RCS was already present in the air from sources such as farm fields, unpaved roads and construction sites, as well as how much was due to the operation of the industrial silica sand facility.
Results from the upwind-downwind analysis showed no difference on a vast majority of sample dates. In fact, there was no detectable difference between the upwind and downwind concentrations on 78 percent of the days during which the winds moved in a consistent and identifiable upwind-to-downwind direction, meaning these facilities contribute very little, if anything, to RCS concentrations in Wisconsin.
Finally, the study found RCS concentrations near frac sand facilities are similar to background concentrations of RCS taken throughout the Upper Midwest. The authors of the study conclude, “These data indicate the exposure to respirable crystalline silica near frac sand producing facilities is the same as exposures in areas throughout this region.”
Though additional sampling evaluating RCS concentrations at the fence lines of other industrial, agricultural and community sources will be helpful in determining ambient crystalline silica sources, this study is good news for those living near silica sand facilities because it means they are not at risk from the exceedingly low concentrations of respirable crystalline silica found at the facilities studied.