GSTM1 and anemia (phenotype): Figure S5 show a graphical comparison of normal [Hb] ranges as bars: ranges indicated by black and light gray bars were based on the sea-level thresholds for anemia and polycythemia suggested by the WHO,12 dark gray bars were based on the upper and the lower limits of 95% RI for samples collected at altitudes below 500 m (Suppl.