Hydraulic fracturing fluid biocide, tributyl tetradecyl phosphonium chloride, causes mitochondrial dysfunction that is enhanced by sodium chloride in Chironomus riparius

Abstract

Backgrounds: Tributyl tetradecyl phosphonium chloride (TTPC) is a biocide used in hydraulic fracturing fluid to minimize bacterial contamination. Methods: This study used the larvae of the freshwater insect Chironomus riparius to investigate the toxicity of TTPC, NaCl, and TTPC+NaCl. Results: LC 50 s (mg/L) at 24 hours for TTPC, NaCl, and TTPC+NaCl were 0.57, >10,000, and 0.32, respectively, indicating a synergistic effect for TTPC+NaCl. ATP production was significantly increased in response to TTPC alone as compared to controls, but decreased significantly when TTPC was combined with NaCl, indicating severe damage to mitochondria. Superoxide dismutase (SOD) activity and lipid hydroperoxides (LPO) levels both increased in response to TTPC treatment, however, only LPO activity increased when TTPC was combined with NaCl. Red laser stimulation failed to enhance ATP production in response to increasing concentrations of TTPC and TTPC+NaCl. Conclusion: Taken together, these results indicate that hydraulic fracturing fluids entering freshwater ecosystems may put macroinvertebrates at risk.