Regional differences in hair zinc concentrations: a possible effect of water hardness.

Hair Zn, Cu, and Mn concentrations were determined by neutron activation procedures in two groups of healthy, Caucasian children aged 4.5 to 5.5 yr from Halifax, Nova Scotia and Guelph, Ontario and consuming soft water (hardness - 33 ppm) and very hard tap water (hardness = 330 ppm), respectively. Median hair Zn level for the Halifax children (26 males and 26 females) was 140 microgram/g, significantly higher (p less than 0.001) than the Guelph children (median = 82 microgram/g; 25 males and 26 females). No significant differences existed between the two groups for median hair Cu and Mn levels (Halifax hair Cu 12.1 microgram/g. Guelph hair Cu 11.0 microgram/g. Halifax hair Mn 0.17 microgram/g. Guelph hair Mn 0.18 microgram/g). The Halifax children were significantly heavier (p less than 0.001) and slightly taller (p = 0.09) than their Guelph counterparts, although mean daily intakes of energy, protein, Zn, Cu, Mn, and dietary fiber, calculated from 3-day food records were not significantly different in the two groups. The large differences in the hair zinc levels may be due to the high concentration of calcium in the Guelph hard water, which may decrease the absorption of zinc.