Biological effects of inhaled hydraulic fracturing sand dust in rats

The pulmonary inflammatory response to inhalation exposure to fracking sand dust (FSD) was investigated in a rat model. Adult male Sprague-Dawley rats were exposed by whole-body inhalation to air or an aerosol of FSD at concentrations of 10 or 30 mg/m3, 6 hours/day for 4 days. The control and FSD-exposed rats were euthanized at post-exposure time intervals of 1, 7 or 27days and pulmonary inflammatory, cytotoxic and oxidant responses were determined. Deposition of FSD particles was detected in the lungs of all the FSD-exposed rats. Analysis of bronchoalveolar lavage parameters of toxicity, oxidant generation, and inflammation did not reveal any significant persistent pulmonary toxicity in the FSD- exposed rats. Similarly, the lung histology of the FSD-exposed rats showed only minimal changes in influx of macrophages following the exposure. Determination of global gene expression profiles detected significant differential expressions of only six and five genes in the 10 mg/m3, 1 day post-exposure, and the 30 mg/m3, 7-day post-exposure FSD groups, respectively. Taken together, data obtained from the present study demonstrated that FSD inhalation exposure resulted in minimal/no toxicity or gene expression changes in the lungs of the rats. The rats were exposed by inhalation to filtered air or fracking sand dust (10 or 30 mg/m3, 6 hours/day for 4 days). At post exposure time intervals of 1, 7, and 27 days, the air and fracking sand dust exposed rats were euthanized and lung samples (n=5 for the 10 mg/m3 post exposure intervals 1 and 7 days; n=4 for 10 mg/m3 post exposure interval 27 days, and n=6 for the 30 mg/m3 fracking sand dust at all post exposure intervals) were used to determine gene expression profiles by RNA sequencing.