Identification and Comparative Mammalian Cell Cytotoxicity of New lodo-Phenolic Disinfection Byproducts in Chloraminated Oil and Gas Wastewaters

Hydraulic fracturing wastewaters discharged to surface water have led to elevated bromide and iodide levels, as well as enhanced formation of brominated trihalomethanes, haloacetic acids, haloacetonitriles, and iodo-trihalomethanes at downstream drinking water treatment plants, in chlorinated effluent from wastewater treatment plants, and in controlled laboratory studies. This enhanced formation of brominated and iodinated disinfection byproducts (DBPs) raises concerns regarding human health, because they are much more toxic than chlorinated DBPs. This study represents the first nontarget, comprehensive analysis of iodinated DBPs formed in chloraminated produced waters associated with hydraulic fracturing of shale and conventional gas formations. Fifty-six iodo-phenolics were identified, comprising three homologous series of mono-, di-, and tri-iodinated phenols, along with two new classes of DBPs: iodomethylphenols and iododimethylphenols. Four iodo-phenolics (2-iodophenol, 4-iodophenol, 2,4,6-triiodophenol, and 4-iodo-2-methylphenol) were investigated for mammalian cell cytotoxicity. All were cytotoxic, especially 2,4,6-triiodophenol, which was more cytotoxic than all trihalomethanes and most haloacetic acids. In addition, geogenic organic compounds present in the oil and gas produced waters, including methylphenol and dimethylphenol, were found to be potential precursors to these iodo-DBPs.