Is nitrate a potential contaminant in your drinking water supply?

If you have a private drinking water well, it is your responsibility to make sure your water is safe for you and your family.

Nitrate (NO3) is the particular form of nitrogen which exists in the soil and which is the result of natural biological processes associated with the decomposition of plant residues and organic matter. Plants can absorb nitrogen in the form of nitrate and ammonium. Nitrates also can come from rainfall, human and animal manure, septic tank/drain field effluent, biosolid (sewage sludge) application to agricultural lands, natural geologic nitrogen, and agricultural/lawn/garden fertilizers containing nitrogen. Of particular concern with nitrates is that it is very mobile and easily moves with water in and out of soil, posing a danger to Michigan’s vast water resources particularly drinking water supplies. It is generally of greatest concern when it contaminates groundwater. However, nitrates also can be a problem in surface water, leading to the excess growth of plants and algae.

Nitrate can be converted in the body to nitrite (NO2). The main intake of nitrates in adults is via food and not water- nitrate levels in the body reach excessive levels when it enters drinking water. Contaminated water is a particular issue where there are shallow-water wells constructed in sandy, unconfined aquifers which do not contain a clay layer with the ability to slow downward nitrate movement into the groundwater supply below.

Groundwater contaminated with nitrates - whether from pet or human waste, decaying plant or animal matter, fertilizer or any other source - poses a health risk to babies, older people and people with compromised immune systems. Such individuals who drink high-nitrate water may develop a potentially lethal condition called “blue baby syndrome” or methemoglobinemia. This is a potentially life-threatening condition caused by ingesting excessive nitrate. This condition reduces the ability of the red blood cells to carry oxygen resulting in a blue discoloration of the skin.

The United States Environmental Protection Agency (EPA) has set the maximum contaminant level (MCL) for nitrate at 10 milligrams per liter and nitrite at 1 milligram per liter. The MDEQ has adopted these standards. Some areas of Michigan have been identified as having unsafe levels of nitrate in drinking water.  Water quality maps for Michigan and certain individual counties showing concentrations of nitrate and other contaminants affecting drinking water are available from MDEQ.

If you suspect you might have nitrate in your drinking water or if you are not sure if it is a problem in your private water supply, contact your local health department or the MDEQ Drinking Water Analysis Laboratory to find out if you should have your water tested. Depending on your results, you will be advised of your options to reduce your nitrate exposure, whether it is developing a plan for an alternate source of drinking water or utilizing a specific type of water treatment system such as reverse osmosis. Note that boiling water does not remove nitrates from water and actually concentrates it. It is also advised that bottled water be used to prepare baby formula.

If you have a private drinking water well, you may also want to read the Michigan State University Extension article on arsenic in drinking water.