Copper is an essential nutrient, but some people who drink water containing copper in excess of the action level over a relatively short amount of time could experience gastrointestinal distress.

Chronic exposure can lead to liver or kidney damage.

People with Wilson's Disease should consult their physician regarding potential exposure effects.

The MCL for copper is 1.3 ppm (1.3 grams per million grams of water).

The City of Pocatello sampled for dissolved copper levels in 1994 and results exceeded the action level of 1.3 ppm in nine of the 61 samples collected. If action levels are exceeded in more than 10% of the samples, the Environmental Protection Agency requires water utilities to undergo additional sampling or install a treatment protocol to reduce the copper to acceptable levels, which is what happened in Pocatello. Because there is a potential for sampling error, EPA suggests resampling prior to implementing any type of treatment program.

Because copper enters drinking water mainly from the corrosion of copper pipes and generally occurs after water has left the City of Pocatello's water system, the best place to test for copper is at the kitchen faucet. We have tested for copper at the supply source, and the levels were less than 0.1 ppm, which is well below the action level of 1.3 ppm.

During the initial sampling campaign, it was discovered that the homes in Pocatello which have experienced higher levels of dissolved copper are in areas serviced by underground power or are older homes that have their electrical system grounded to the water pipes. Apparently it is possible to cause copper corrosion due to electrical currents in the water line. The City has installed devices at the water meter to interrupt stray currents in an effort to determine the effect of this phenomenon.