Trihalomethane comparative toxicity: Acute renal and hepatic toxicity of chloroform and bromodichloromethane following aqueous gavage

Abstract

Bromodichloromethane (BDCM) and chloroform (CHCl3) are by-products of drinking water chlorination and are the two most prevalent trihalomethanes (THMs) in finished drinking water. To date, no comprehensive comparison of the acute renal and hepatic effects of BDCM and CHCl3 following oral gavage in an aqueous dosing vehicle has been conducted. To characterize BDCM- and CHCl3-induced nephro- and hepatotoxicity following aqueous gavage and compare directly the responses between these THMs, 95-day-old male F-344 rats were given single oral doses of 0.0, 0.75, 1.0, 1.5, 2.0, or 3.0 mmol BDCM or CHCl3/kg body wt in an aqueous 10% Emulphor solution. Compound-related hepatic and renal damage was evaluated by quantitating clinical toxicity markers in the serum and urine, respectively. Both THMs appear to be equally hepatotoxic after 24 h, but BDCM caused significantly greater elevations in serum hepatotoxicity markers than CHCl3, at 48 h following exposure to 2.0 and 3.0 mmol/kg. In addition to causing more persistent liver toxicity than CHCl3, BDCM also appears to be slightly more toxic to the kidney at lower doses. Potency differences between the two THMs may be due to pharmacokinetic dissimilarities such as greater metabolism of BDCM to reactive metabolites or more extensive partitioning of BDCM into kidneys and fat depots, resulting in prolonged target tissue exposure.