Lead in Drinking Water

What is lead?

Lead is a toxic metal that was used for many years in products found in and around homes. Even at low levels, lead may cause a range of health effects including behavioral problems and learning disabilities. Children six years old and under are most at risk because this is when the brain is developing. The primary source of lead exposure for most children is lead-based paint in older homes. Lead in drinking water can add to that exposure.

How does lead get into tap water?

Typically, lead gets into your water after the water leaves your local treatment plant or your well. That is, the source of lead in your home's water is most likely from pipes or solder in your home's own plumbing. Older homes, particularly those constructed before 1955, often contain lead water service lines. Homes constructed prior to the mid to late 1980's may have their plumbing connected with lead base solder. For lengthy periods (over six hours), lead can dissolve into drinking water that is left standing in household piping made with these materials. The most common cause is corrosion, a reaction between the water and the lead pipes or solder. Dissolved oxygen, low pH (acidity) and low mineral content in water are common causes of corrosion. All kinds of water, however, may have high levels of lead.

What are the health effects of lead?

The health effects of lead are most severe for infants, children under six years of age, pregnant women and nursing mothers. For infants and children, exposure to high levels of lead in drinking water can result in delays in physical or mental development. For adults, it can result in kidney problems or high blood pressure. Although the main sources of exposure to lead are ingesting paint chips and inhaling dust, studies have shown that 10 to 20 percent of human exposure to lead may come from lead in drinking water. Infants who consume mostly mixed formula can receive 40 to 60 percent of their exposure to lead from drinking water. Health Canada has established a maximum acceptable concentration for lead in drinking water of 10 ppb (parts per billion) in a free flowing sample of water.

Flowing water samples better reflect the overall quality of household drinking water, and are indicative of normal lead exposure from drinking water. This drinking water guideline has been developed to protect the population most at risk, namely infants and young children.

Some in-home water treatment equipment such as lead removing filters, reverse osmosis systems, and distillation units do remove lead dissolved in water. These systems can be very costly and require regular maintenance to function properly. If not properly maintained, they can promote the growth of bacteria and cause other water quality problems. Bottled water is not necessarily lead-free. Check the label to see if it says whether the water is lead-free. Also, bottled water may cost as much as 100 times more than your tap water.

Information on water quality may be obtained by calling your local municipality. You can also visit Health Canada's web site for more information on lead and human health.