Point-of-use water filters can effectively remove disinfection by-products and toxicity from chlorinated and chloraminated tap water

Abstract

Epidemiological risk estimates point toward potential health risks posed by disinfection by-products (DBPs) in chlorinated drinking water. Point-of-use filters can effectively remove regulated DBPs from tap water but the removal of unknown DBPs and toxicity has not yet been assessed. We evaluated 11 tap water filters for their efficacy to abate fluoride, bacteria, and adsorbable organic halogens (AOX) as the sum parameter of known and unknown halogenated DBPs. Biological effects were quantified in water samples enriched with solid phase extraction by use of the Microtox assay for bacterial cytotoxicity, the AREc32 assay for oxidative stress response, and the umuC assay for genotoxicity. Six out of 11 filters effectively removed chlorinated and brominated organic halogens by >60%. Reverse osmosis and one activated carbon based gravity filter were most effective (>94% AOX removal). Four out of five non-membrane pressure filters were less effective for AOX abatement than four out of five activated carbon based gravity filters. Renewal of the filter cartridges significantly improved AOX removal efficacies. Fluoride was removed by >83% only by reverse osmosis and two filters specifically designed for fluoride removal by use of activated alumina. Bacterial counts increased after filtration with most filters, indicating biofilm growth on the filter matrix. Cartridge renewal decreased bacterial counts. Seven out of 11 filters reduced cytotoxicity, oxidative stress response, and genotoxicity by >60%. Activated carbon based tap water filters could provide an important short-term public health benefit through removal of halogenated DBPs, but regular filter cartridge exchange is critical to maintain a good filter efficacy.