GSTM1 and anemia (phenotype): We estimated the concentration of hemoglobin in peripheral blood samples (Hb g/dl) from 299 out of 309 children and compared it with reference data by age range for diagnostic criteria for anemia [23]; we found that 21 out of 299 children had Hb g/dl values that, for their age, were indicative of anemia (6.9 %).