GSTM1 and anemia: A few other studies that report on water quality and anemia association indicate that children from dwellings with tap water (improved) had, on average, 1.2 g/dL higher Hb than children whose mothers used public wells (unimproved) suggesting a potential effect on anemia.43 A study in the Philippines also found water supply to be a significant independent factor affecting Hb levels.44