Division of Occupational & Environmental Medicine

You base your MRLs for copper of 0.02 mg/kg/d for acute and intermediate exposures on a study by Pizarro et al. (1999a) who found that gastrointestinal symptoms occurred when adults were exposed to a concentration of copper ≥ 3 mg/L but that there were no increases in symptom incidence at 1 mg/L. This study, however, as were other studies by this group, was designed to address issues of safe water concentrations of copper. Other endpoints may be more valid for determining MRLs for copper, particularly those which are protective of liver disease, a particularly sensitive toxic endpoint. Unless noted within the text of these comments, I determined dose using default values published in the Exposure Factors Handbook (USEPA, 1997) when information on weight or ingested formula (in infants) was missing.