Lead occurs naturally in the earth’s crust in small amounts.
It can be found everywhere in our environment, not only because it occurs naturally, but also because it’s used extensively in modern industry (mining, manufacturing and burning of fossil fuels).
Humans are exposed to lead in both outdoor and indoor environments. It is found in the air, soil, dust, drinking water, food and various consumer products.
Concentrations of lead in the environment increased significantly following the industrial revolution. Over the past 25 years, Health Canada, Environment Canada, and other Canadian regulatory agencies have substantially reduced Canadian’s exposure to lead by legislating and enforcing maximum lead concentrations in gasoline and house paints. Also, the use of lead-soldered food cans has been virtually eliminated through an agreement negotiated with Canadian canneries.
Lead may enter the body through: the mouth (ingestion), the lungs (in halation) or the skin (dermal route). The growing fetus may also be exposed to lead from the mother via the placenta. In Canada, the main exposure routes are ingestion or inhalation. The most common route of entry is ingestion, except in industrial environments, where inhalation of lead fumes may play a larger role.
Absorption of lead through the skin is rare. Children are at greater risk of ingesting lead due to their frequent hand-to-mouth activity and tendency to mouth or chew objects they come into contact with (especially non-food products such as paint chips, furniture or toys).
Regardless of the route of entry, lead is absorbed directly through the blood into tissue.
Lead has no known biological function in the body. Once absorbed, it circulates in the bloodstream and either accumulates in tissues or is excreted as waste. Some of it is absorbed into soft tissue such as the liver, kidneys, pancreas and lungs. A very high proportion of absorbed lead is transferred to bone (hard tissue), where it accumulates over time and remains for long periods. The half-life (time for the body to excrete half the accumulated lead) is about 25 years. High lead concentrations can stay in the body for many years after exposure to lead has stopped.
Some of the more prominent symptoms of lead poisoning include headaches, irritability, abdominal pain, vomiting, anemia (general weakness, paleness), weight loss, poor attention span, noticeable learning difficulty, slowed speech development and hyperactivity.
However, at very low exposure levels, lead may not produce specific symptoms, but still can produce subtle adverse effects on children’s development.
Lead levels in tap water will increase with the length of time water is left standing in pipes. At home, you can let tap water run before drinking it if it has been standing in the pipes for a few hours. Turn on the taps until the water runs cold first thing in the morning or at any other time when the water has been left standing in your home’s plumbing system for a long time.
However, in many cases, normal domestic activities in the morning, such as showering and flushing toilets, should minimize the need to flush taps. To conserve water and avoid the extensive flushing of taps, you can also keep some drinking water in the refrigerator.
You can also minimize lead levels by using only cold water for drinking, cooking and making baby formula. Hot or warm water tends to acquire more lead, especially in those areas that have soft water. Lead contamination is more evident in areas with soft drinking water because this water tends to be acidic (low pH). Such conditions favour the leaching of lead from plumbing.
Paints made before 1950 contained large amounts of lead. In fact, some paint made in the 1940s contained up to 50% lead by dry weight. If your home was built before 1960, it was likely painted with lead-based paint. Since the 1950’s, the use of lead has been more common in exterior paint than interior paint. Subsequently, the use of lead in paints decreased significantly. Currently, under the Hazardous Products Act, lead levels in indoor paint are limited to 0.5 per cent by weight. There are proposed regulatory changes for both interior and exterior consumer paints to limit lead in paints to 0.06 per cent by dry weight. In homes built after 1980, there is little need for concern about lead levels in interior paints. All post-1992 consumer paint produced in Canada or the US for indoor use is virtually lead-free.
- Contact Environmental Health at 519-631-9900
- Health Canada
- Canadian Mortgage and Housing Corporation