Arsenic in water

Arsenic (As) is a natural element found in the Earth’s crust. Some areas of New Brunswick have a greater potential for elevated arsenic levels in drinking water.

Arsenic is likely to be found in well water throughout New Brunswick. The presence of arsenic in well water depends on the rock and soil type in the area. The most common source of arsenic in groundwater is through erosion and weathering of soils, minerals, and ores. Industrial effluents and pesticide runoff may also contribute arsenic to water in some areas.

In water, arsenic has no taste, smell, or colour. It can only be detected through a chemical test.

The Canadian drinking water quality guideline for arsenic is 0.01milligrams per litre (mg/L).

The guideline limit for arsenic is based on the level that can be achieved by certified treatment units. Make every effort to keep arsenic levels as low as possible in drinking water.

Short-term exposure (over days or weeks) to high levels of arsenic in drinking water can result in nausea, diarrhea, and muscle pain.

Long-term exposure (over years or decades) to low levels of arsenic in drinking water may cause certain types of cancer.

The risk to human health is through ingestion only-drinking, cooking, teeth brushing. Well water with arsenic levels greater than 0.01 mg/L can safely be used for bathing, handwashing, dishwashing, and watering a garden.

It is important to regularly test your well water for a standard suite of chemical parameters, including arsenic.

Find a list of accredited water testing laboratories in Yellow Pages under “laboratories.” Be sure to ask the laboratory if they are accredited for the tests you are requesting by either the Canadian Association for Laboratory Accreditation or the Standards Council of Canada.  It is important to get the special sampling bottles and instructions on proper sampling from the laboratory who will be doing the testing.

In New Brunswick, RPC Analytical Services laboratory is the designated Provincial Analytical Services laboratory. They have offices in Fredericton and Moncton, and maintain SCC accreditation.

The cost of analyzing water samples can vary depending on the lab and the number of parameters being tested.

Homeowners are responsible for monitoring the quality of their well water:

• Test for bacterial quality every 6 months.
• Test for chemical quality every 2 years.
• Test more often if you notice changes in physical qualities – taste, smell, or colour.

Regular testing alerts you to problems with your drinking water.

If arsenic is present in the first test, get a second test to confirm the original results.
If arsenic is confirmed to be present in the well water,

• Find an alternate source of water for drinking, cooking, and teeth brushing, such as bottled water or a dug well that has been tested and found to be safe.

or

• Treat your current source of water to reduce arsenic levels.

Arsenic cannot be removed from water through boiling, chlorination, or pitcher-style filtration units. Boiling water may increase the concentration of arsenic.

Effective treatment methods include

• adsorption
• anion exchange
• distillation
• reverse osmosis

Buy a treatment system that has been certified to meet the current NSF standards for arsenic reduction. NSF International is a not-for-profit, non-governmental organization that sets health and safety standards for manufacturers in 80 countries. See its website at www.nsf.org.

Once installed, re-test your water to ensure the treatment system is working properly. Maintain the system according to the manufacturer’s instructions to ensure a continued supply of safe drinking water.

Drilled wells are more vulnerable to arsenic contamination than dug wells.

Arsenic is a negative ion (anion) in solution. When you use anion exchange treatment, the resin in the unit will remove certain anions more readily than others. If other more preferred anions are present such as uranium or sulphate, the effectiveness of the unit may be reduced. The resin in the anion exchange unit may need to be regenerated more frequently to reduce the concentration of arsenic to a satisfactory level. It is important that a detailed chemical analysis of your water be completed to determine if other substances are present that will affect arsenic treatment.

If the anion exchange unit is not properly maintained, the arsenic contained on the resin bed may rapidly detach, leading to higher levels of arsenic in the treated water than the untreated water. It is important to follow instructions for resin regeneration and replacement.

Arsenic may be in a form that is not readily removed by anion exchange. When this is the case, pre-treatment by oxidation may be required.