Public Health Advisory for Naturally Occurring Lead in Bedrock

In 2006, Public Health Services issued a Public Health Advisory to all rural Hamilton residents located above the Niagara Escarpment, who use a drilled water well as their main source of drinking water. There is potential for high lead levels above the Ontario Drinking Water Standard in some wells due to naturally occurring lead in the bedrock. The Medical Officer of Health advises rural City of Hamilton residents who use a drilled water well located above the Niagara Escarpment to have their water tested for total and dissolved lead.  

Lead occurs in bedrock in Southern Ontario in varying amounts and in spotty, unpredictable patterns. The lead was deposited when the bedrock was formed in ancient times. The bedrock under northwestern Hamilton is part of a large rock formation running from north of Hamilton into the Niagara Region. As a result, it is not possible to predict which drilled wells may be affected.

Testing for lead in drilled water wells

Public Health Services tested lead levels in 45 drilled water wells in the northwestern rural area of Hamilton across approximately 12.5 square kilometres. Thirteen of the 45 wells had lead levels above the Ontario Drinking Water Standard for lead. The pattern of lead levels means that lead in the water is most likely lead that occurs naturally in the bedrock.

You should test water from your well in late fall after leaves have fallen from the trees or early spring. Do not test your water for lead in the summer.  The presence and/or levels of lead varies throughout the year, with summer being when lead levels are likely to be lowest or not detectable.  It is best to test the water when lead is most likely to be present.

Check labs in Ontario that are licensed by the Ministry of the Environment to test water for lead. Call the lab to confirm price and instructions for taking a water sample. You should test your water before treating water.

You do not need to have your drinking water tested for total and dissolved lead if your:

  • Drinking water comes from the municipal water supply and you live in the urban area of Hamilton. The municipal water supply is regularly tested for lead.
  • Drinking water comes from the municipal water supply in Carlisle, Freelton, Greensville or Lynden. These supplies are regularly tested for lead.
  • Drinking water comes from a cistern in rural Hamilton, as this system does not use water sourced in the underlying bedrock. 

The Maximum Allowable Concentration, or MAC, for lead in regulated drinking water in Ontario is 10 micrograms per litre. This level is based on average concentrations of lead in water consumed over a long time and long-term effects of lead. Groups with a higher sustceptibility to increased effects from exposure to lead sources include children six years of age and under, pregnant women and women planning a pregnancy.

What to do if you have lead in your water

Water is safe for bathing, showering, brushing teeth, washing dishes and clothes even if it contains lead.

If you have lead in your water, stop drinking the water and using it for making coffee, tea, baby formula, baby food, juice or food. You need to determine what you will do for drinking water. If the source of lead is the groundwater, flushing the lines will not get rid of lead. Contact a water treatment company or research your options to reduce lead levels. Your options include:

  1. Using bottled water
  2. Bringing in water from a known safe supplier
  3. Using a reverse osmosis treatment system
  4. Using distillation units
  5. Using water filters approved for lead removal by the National Sanitation Foundation with “NSF/ANSI-53 for lead removal” on the label and the NSF logo.Check for filters that meet the NSF-53 Standard by calling 1-800-673-6275.

It is important to follow the filter manufacturer's instructions. When using a filter be sure that:

  • The water is free of bacteria; this is certain to be the case when using City of Hamilton water
  • You flush the water before using it for at least 30 seconds if the filter is on the tap
  • You change the filter when recommended by the manufacturer

Boiling your tap water does not remove lead. Do not use water from the hot water tap for cooking or drinking.

Test your water again after you have installed lead removal equipment, to determine if lead levels are acceptable.