Constituent | Standard | Source or Cause | Significance |
Ammonium/Ammonia (+as N) | 2 mg/L** | Decomposition of animal and plant proteins, agricultural, urban runoff, and effluent from wastewater treatment plants or industrial contamination. | Can cause unwanted algal blooms. Can indicate sewage pollution and consequent possible presence of pathogenic microorganisms. |
Calcium (Ca2+) | --- | Occurs in rocks, bones, shells, etc. Very abundant. | Causes water hardness. Essential for normal growth and health (1 - 2 g daily requirement). |
Lead (Pb2+) | MCL 15 μg/L* 50 μg/L** | Leaching from ores and erosion of natural deposits; effluent discharges; corrosion of household plumbing systems. | A cumulative poison particularly in infants and children; Delays physical and mental development; May cause kidney problems and high blood pressure in adults. |
Magnesium (Mg2+) | 35 mg/L** | Major constituent of geological formations. | A major dietary requirement for humans (0.3 - 0.5 g/day) and the second major constituent of water hardness. |
Potassium (K+) | --- | Geological formations. | No health concerns except at gross levels. |
Sodium (Na+) | 20 mg/L** | Abundant constituent of rocks and soils. | Essential dietary requirement (5 g or more). Causes hypertension if in excess. |