Types of contaminants
Surface water and wells are more exposed to polluting sources, whereas deep well water is more liable to contain naturally occurring metals or minerals. Drinking water can therefore be contaminated by such elements as microorganisms and chemicals.
Measures to prevent water contamination (immovable not served by municipal water services)
Measures can be taken to prevent water contamination in cases where the immovable is not serviced by a municipal water supply. They include:
- Locating the well as far as possible from:
- Septic tanks
- Manure storage sites
- Areas where fertilizer is applied
- Silos
- Preventing the presence of animals near the well
- Ensuring that the location and design of the well and its surroundings keep runoff and water drainage at a distance
- Capping and sealing the well (with the cap at least 30 cm above ground level) and protecting the well’s location
Contaminants and health risks
Escherichia coli (e. Coli), fecal coliforms or enterococci
The presence of Escherichia coli (E. coli), fecal coliforms or enterococci in water indicates that it has been contaminated by stool. Contaminated water can contain microbes (bacteria, viruses or parasites) that cause health problems. To be safe for drinking, water must not contain any of these microorganisms.
Health risks
Among other problems, water contaminated with microorganisms can cause gastroenteritis (stomach flu).
Uranium
Uranium is a radioactive element that occurs naturally in the soil. It can dissolve in groundwater and seep into wells, especially deep wells. In Québec, the concentration standard not to be exceeded for uranium in drinking water is 0.02 mg/L.
Health risks
Drinking water with high levels of uranium can cause minor kidney damage. These effects gradually disappear when the person stops drinking contaminated water.
Barium
Barium is a chemical element that occurs naturally in the soil, often in low concentrations. It can dissolve in and contaminate groundwater. In Québec, the concentration standard not to be exceeded for barium in drinking water is 1 mg/L.
Health risks
Exposure to high levels of barium in water may:
- increase blood pressure
- cause cardiovascular problems
Arsenic
Arsenic is a chemical element that occurs naturally in the soil. It can dissolve in and contaminate groundwater. In Québec, the concentration standard not to be exceeded for arsenic in drinking water is 0.010 mg/L. Since arsenic can have significant health impacts, its concentration in drinking water should always be kept as low as possible.
Health risks
A person exposed to arsenic for several years has a greater risk of suffering from:
- blood circulation problems
- skin cancer
- lung cancer
- bladder cancer
Nitrates/nitrites
The presence of nitrates/nitrites in water can result from:
- the use of chemical fertilizers and manures
- defective septic systems
- decomposing plant and animal matter
In Québec, the concentration standard not to be exceeded for nitrates/nitrites in drinking water is 10 mg/L.
Health risks
Babies under the age of six months exposed to nitrates/nitrites may develop breathing problems due to a slowing of oxygen transport between the lungs and the tissues. High nitrate/nitrite contamination causes bluish discolouration of the skin and lips in infants. Based on current knowledge, regular consumption of drinking water contaminated with nitrates/nitrites for several decades can lead to a cancer risk.
Iron
Iron is a chemical element that occurs naturally in the soil. It can dissolve in groundwater. In Québec, there is no standard for the maximum quantity of iron allowed in drinking water.
However, when its concentration in water exceeds 0.3 mg/L, iron can:
- alter the taste and colour of water
- stain washed clothes and household appliances
Health risks
Iron concentrations in water are generally not harmful to health.
Fluorides
Fluorides are mineral salts that can occur naturally in the soil and dissolve in groundwater. A small amount of fluorides in drinking water has a beneficial effect. By contributing to tooth mineralization, fluorides protect against tooth decay.
In Québec, the maximum acceptable concentration for fluoride in drinking water is 1.5 mg/L.
Health risks
Prolonged consumption of water containing a fluoride concentration in excess of 1.5 mg/L can cause dental fluorosis in children under the age of nine. Dental fluorosis is characterized by the appearance of permanent white or brown stains on the teeth. Drinking water with a fluoride level above 4 mg/L can cause bone fluorosis in people who drink it for many years. Bone fluorosis makes bones more brittle and can cause joint pain and stiffness.
Manganese
Manganese is a chemical element that occurs naturally in the soil. It can dissolve in and contaminate groundwater. A small amount of manganese is needed by all living organisms. Drinking water can sometimes contain manganese, but it is mainly found in food.
In Québec, there is currently no standard for maximum concentration of manganese in drinking water.
When its concentration in water exceeds 0.05 mg/L, manganese can:
- alter the taste, smell and colour of water
- stain washed clothes and household appliances
Health risks
Some studies suggest that manganese may have an adverse effect on the neurological development of children. However, these studies would involve children exposed to a manganese concentration in water much higher than 0.05 mg/L.
Blue-green algae (cyanobacteria)
Blue-green algae, also called “cyanobacteria,” are bacteria that are naturally present in Québec’s water bodies. They multiply mainly in summer. When they become very abundant, blue-green algae form what are called “blooms,” which can spread over all or part of a body of water. The water turns green and its texture becomes similar to that of paint. Scum (foam) can also appear on the surface of water contaminated with blue-green algae. It is normally when scum begins to appear that blue-green algae can become harmful to health.
Health risks
Some types of blue-green algae produce toxic substances. A person may develop flu-like symptoms or skin or throat irritation after drinking or coming into contact with water contaminated with blue-green algae.
