Common Contaminants Found in Groundwater Across Canada

Microbial quality is one of the primary indicators for the safety of a drinking water supply. Of all contaminants in drinking water, human and/or animal feces present the greatest danger to public health. Pathogenic or disease-causing microorganisms may be found in untreated water supplies.

The presence of waterborne disease-causing microorganisms in drinking water may result in gastrointestinal illness or diarrhea. Infants, the elderly and immuno-suppressed individuals are at greater risk of serious infection when exposed to these organisms.

Nitrate is a chemical compound and the most common form of nitrogen found in water. Other forms of nitrogen include nitrite and ammonia. Nitrate occurs naturally and is widespread in the environment.

Nitrate is more often found in groundwater than in surface water. Nitrate is commonly found in shallow wells that are located in agricultural areas. Nitrate levels in ground water may change over time, especially after a heavy rainfall.

Consuming too much nitrate can affect how blood carries oxygen and can cause methemoglobinemia (also known as blue baby syndrome). Bottle-fed babies under six months old are at the highest risk of getting methemoglobinemia.

Arsenic is a natural component of the earth’s crust and is widely distributed throughout the environment in the air, water and land. It is highly toxic in its inorganic form.

People are exposed to elevated levels of inorganic arsenic through drinking contaminated water, using contaminated water in food preparation and irrigation of food crops, industrial processes, eating contaminated food and smoking tobacco.

Health Canada and the International Agency for Research on Cancer consider arsenic a human cancer-causing agent.

Lead is a naturally occurring metal found in rock and soil and also has many industrial applications. Due to both its natural occurrence and long history of global use, lead is ubiquitous in the environment and can be present in drinking water.

According to Health Canada, lead is not typically found in natural water sources. In most cases, lead seeps into the municipal water supply through aging infrastructure. Lead pipes, old wells, plumbing parts, even fittings, soldering, faucets and valves can all leach into drinking water.

In Canada, lead was a commonly used material for water pipes until 1975, when the metal was banned under a revised National Plumbing Code of Canada. Older homes may still contain lead materials.

Sodium is the sixth most abundant element in the earth's crust.

An estimated 25 to 50 percent of salt used on roads for snow and ice control enters the ground water and can elevate levels of sodium in public water supplies.

Although there is no health related objective for sodium, persons on strict sodium reduced diets applying to all sources, levels in drinking water should be below 20 mg/L .

Iron in rural groundwater supplies is a common problem. The iron occurs naturally in the aquifer but levels in groundwater can be increased by dissolution of ferrous borehole and handpump components.

The aesthetic objective for iron, set by appearance effects, in drinking water is 0.3 mg/L. Excessive levels of iron in drinking water supplies may impart a brownish colour to laundered goods, plumbing fixtures and the water itself.

The precipitation of iron can also promote the growth of iron bacteria in water mains and service pipes.

Similar to iron, manganese is a mineral that is found naturally in the environment and is one of the most abundant metals on the earth’s surface, in air, water, and soil.

Manganese is used in various industries, including the manufacture of iron and steel alloys, batteries, glass, fireworks, various cleaning supplies, fertilizers, varnish, fungicides, cosmetics, and livestock feeding supplements.

The colour related aesthetic objective for manganese in drinking water is 0.05 mg/L. Like iron, manganese is objectionable in water supplies because it stains laundry and fixtures black

Hardness is caused by dissolved calcium and magnesium

The operational guideline for hardness in drinking water is set at between 80 and 100 mg/L.

On heating, hard water has a tendency to form scale deposits and can form excessive scum with regular soaps. Conversely, soft water may result in accelerated corrosion of water pipes. Hardness levels between 80 and 100 mg/L are considered to provide an acceptable balance between corrosion and incrustation.

Water supplies with a hardness greater than 200 mg/L are considered poor but tolerable. Hardness in excess of 500 mg/L in drinking water is unacceptable for most domestic purposes.

The operational guideline for organic nitrogen in drinking water is 0.15 mg/L. High levels may be caused by septic tank or sewage effluent contamination. This form of contamination is often associated with some types of chlorine-worsened taste problems.

Organic nitrogen compounds have the potential to react with chlorine and severely reduce its disinfectant power.

Taste and odour problems are also common with organic nitrogen levels greater than 0.15 mg/L

pH is a parameter that indicates the acidity of a water sample. The operational guideline recommended in drinking water is to maintain a pH between 6.5 and 8.5.

The principal objective in controlling pH is to produce a water that is neither corrosive nor produces incrustation. At pH levels above 8.5, mineral incrustations and bitter tastes can occur. Corrosion is commonly associated with pH levels below 6.5 and elevated levels of certain undesirable chemical parameters may result from corrosion of specific types of pipe.

The aesthetic objectives for iron and manganese, set by appearance effects, in drinking water are 0.3 and 0.05 mg/L, respectively. Excessive levels of these parameters in drinking water supplies may result in a brownish colour to the water and produce a bitter, astringent taste in water and beverages.

Chloride is a naturally occurring element that is common in groundwater.

The aesthetic objective for chloride levels of 250 mg/L, based on the potential for undesirable tastes at concentrations above this level and a potential increased risk of corrosion of pipes.

The presence of chloride in groundwater can result from a number of sources including the weathering of soils, salt-bearing geological formations, deposition of salt spray, salt used for road de-icing, contributions from wastewaters and in coastal areas, intrusion of salty ocean water into fresh groundwater sources.

Sulfates are naturally occurring substances that are found in minerals, soil, and rocks. They are present in ambient air, groundwater, plants, and food. The principal commercial use of sulfate is in the chemical industry. Sulfates are discharged into water in industrial wastes and through atmospheric deposition

When sulphate levels exceed 500 mg/L, water may have a laxative effect on some people

Fluoride is found naturally in soil, water, and foods. It is also produced synthetically for use in drinking water, toothpaste, mouthwashes and various chemical products. Water authorities add fluoride to the municipal water supply, because studies have shown that adding it in areas where fluoride levels in the water are low can reduce the prevalence of tooth decay in the local population.

Tooth decay is one of the most common health problems affecting children.

Researchers from around the world have conducted hundreds of studies that look at the safety of adding low concentrations of fluoride to drinking water. There’s no evidence that fluoride added to local water supplies causes any health problems, aside from the occasional mild case of dental fluorosis.