The chemical water quality in roof-harvested water cisterns in Bermuda

The chemical quality of water stored in roof-harvested rainwater cisterns and used for domestic consumption in Bermuda was assessed by analyzing a suite of metal and metalloid elements, major ions, pH and conductivity in water and sediment from 112 and 36 private residences, respectively. The chemical quality of water was good, with a low incidence of health-based primary drinking water standards being exceeded:<1% for Pb and Se and < 3% for nitrate. In nearly all cases these could be accounted for by unapproved use of unregistered groundwater wells to supplement the water supply. Sediment which accumulates in the water cisterns was found to have elevated concentrations of some elements, similar to local soil. In particular, the concentration of arsenic (As) in cistern sediment exceeded the U.S. EPA generic soil screening limits (SSL) for human ingestion of soil at all 36 locations sampled. Additionally, Pb and Hg exceeded the SSL at 4 (11%) and 1 (3%) sites, respectively. However, there are no standards or guidelines in existence with which to fully assess the sediment data. Further research needs are identified which will allow a human health-based risk assessment to be conducted to enable such standards to be developed.