GSTM1 and anemia (phenotype): Anemia levels are classified as mild (Hb 10.0–12.9 g/dL for men;10.0–11.9 g/dL for women), moderate (Hb 7.0–9.9 g/dL) and severe (Hb < 7.0 g/dL) according to World Health Organisation (27).