Lead in Water
In late April 2007, the Ministry of the Environment determined that drinking water samples taken from some consumers’ taps in the City of London contained levels of lead above the drinking-water standard set out in O. Reg. 169/03 under the Safe Drinking Water Act, 2002 (SDWA). The standard is 0.01 milligrams per litre (mg/L). It was determined that these elevated levels occurred even after the lines had been flushed. This was a very unusual result because lead levels in the water from the drinking-water systems were found to be below the standard before water distribution to individual taps through the plumbing system.
Following this, all municipalities in the province were asked to conduct tests to make sure that they were not experiencing high levels of lead in tap samples after flushing. On May 24, 2007 a formal order was issued to some municipalities including Cornwall and Alexandria to do a sampling and testing program. The tests were to be performed on at least one large or small municipal residential drinking-water system that:
a) was known to have or likely to have lead service pipes, or
b) served buildings with lead water service pipes as defined in the Building Code (O. Reg. 350/06 made under the Building Code Act, 1992) by May 31, 2007.
The Eastern Ontario Health Unit, in its commitment to inform the public, has put together the following information to answer questions on lead and its related health risks.
In general, the amount of lead in natural water supplies is very low: this was confirmed by reviewing Historical lead data from Drinking Water Information Systems (DWIS) from April 2003 to April 2007. DWIS captures water quality information from the distribution system, not from water that has been standing in residential plumbing. Therefore, it is safe to assume that DWIS samples have been collected after flushing a tap for approximately five minutes (Ministry of Environment).
According to the Drinking Water Surveillance Program (DWSP) data collected between 1986 and 1995, in most situations, simply running the tap for five minutes greatly reduces lead in drinking-water, usually to a value well below the Ontario Drinking Water Quality Standard of 10 ug/L.
Lead is more likely to be found in soft or very acidic water and in very old or very new homes. Homes built before 1950 often have leaded distribution lines and service connections. In newer homes, lead may leach from solder for several years until the pipes form a protective oxide layer.
Flushing for a period of five minutes or more takes water that has been in contact with lead pipes and solder in plumbing for a period of time and replaces it with water from the drinking-water system that has only been briefly in contact with the lead pipes. Therefore, one would not typically expect to find elevated levels of lead in tap water after flushing. References:
U.S. Environmental Protection Agency: Lead in Drinking Water
 Lead FAQs
Lead Health Effects
Health Canada: Lead Information Package
Lead in the tap water of some homes on the island of Montreal
U.S. Environmental Protection Agency: Lead in Drinking Water
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