The NOAEL of 275 ppm (13.6 or 14.4 mg/kg-day for male and female rats, respectively) is chosen as the basis for the chronic oral RfD. Mice received a higher dose on a weight basis (24 mg/kg) but effects, although equivocal, were observed. Doses between 14.0 and 24.0 mg/kg were not tested in rats. In addition, this NOAEL is supported by NOAELs from other chronic and subchronic rat studies. Therefore the 14.4 mg chlorine/kg in females is selected as the basis of the RfD.