Pulmonary effects of inhaled diesel exhaust and fracking sand particles in rats
The pulmonary response to inhalation exposure to diesel exhaust particles (DEP) and fracking sand particles (FSD) was investigated in a rat model.  Healthy adult male Sprague-Dawley rats were exposed by whole-body inhalation to air (control) or an aerosol containing DEP at a concentration of 1.0 mg/m3 combined with FSD at concentrations of 30 mg/m3, 6 hours/day for 4 days.  The control and DEP/FSD exposed rats were euthanized at post-exposure time intervals of 1, 7, or 27 days and pulmonary inflammatory, cytotoxic, and oxidant responses were determined.  Analysis of bronchoalveolar lavage parameters of toxicity such as lactate dehydrogenase activity, oxidant generation, and inflammation revealed only minimal changes in pulmonary toxicity in the DEP/FSD-exposed rats, compared with the time-matched controls. The lung gene expression profiles showed only minimal changes in the DEP/FSD exposed rats compared with the controls. Specifically, there were a total of 6 genes significantly differentially expressed (fold change >1.5 and FDR p<0.05) only at the one-day post-exposure group. The data obtained from the present study demonstrated that DEP/FSD inhalation exposure, under the conditions employed in the present study, resulted in only minimal changes in lung toxicity and gene expression profile in the rats. Overall design: The rats were exposed by inhalation to filtered air or 30 mg/m3 fracking sand dust and 1.0 mg/m3 of Diesel particles (6 hours/day for 4 days) . At post exposure time intervals of 1, 7, and 27 days, the  rats were euthanized and lung samples (n=8  were used to determine gene expression profiles by RNA sequencing.