Lead in Drinking Water

Recent tests on water delivered by some Alaskan community water systems have revealed unsafe levels of lead in the water. Lead concentrations in excess of five parts per billion are considered unsafe, especially for children. Lead poisoning causes weakness, anemia, constipation and paralysis. That sounds depressing enough, but it's not even the whole story; lead poisoning itself causes depression.

Alaska's Department of Environmental Conservation has found excessive lead concentrations in community water systems at the western Alaska villages of St. Michael, Gambell and Shishmaref, and also at the interior village of Birch Creek. The culprit, reports DEC engineer Stan Justine in a recent issue of The Northern Engineer, is lead-containing solder used to join copper pipes in the water distribution systems.

Corrosive chemical action similar to that in a car battery occurs to release lead into the water. The copper pipe acts as a cathode, and droppings of excess lead solder inside the pipe act as sacrificial anodes, thereby becoming released in ionic form into the water.

The problem occurs elsewhere but is more common at high latitude for three reasons. In the North, surface water often is used for water supplies. Being soft, this water promotes corrosion more than hard water. Secondly, water use in the North is often at a low rate, so contaminants such as lead tend to build up. Thirdly, the water in northern distribution systems often is heated to prevent freezing, and this heating promotes corrosion.

Fortunately, as the distribution systems grow older, the excess lead gets eaten away from the pipes. Hence, after a few years, the problem diminishes. Also, users can avoid the highest lead concentrations by running a tap for a few minutes before taking drinking water from it.