Nitrate in Drinking Water Information:

Properties:

Nitrate is composed of one nitrogen atom and three oxygen atoms and has a chemical formula of [NO3]-. Plants and animals require nitrogen to grow and live, and nitrate is an inorganic form of nitrogen provided by soil and fertilizers. Ammonia in fertilizers is oxidised to nitrate—a form of nitrogen that plants can directly use—by bacteria that live in soil. Nitrates are generally water soluble and can enter drinking water supplies from a variety of different sources. Nitrates can be converted to nitrites, which are chemicals that are also implicated in drinking water quality. The reverse reaction also occurs: when nitrites are present in water, they are often oxidised to nitrates.

Sources:

One of the predominant sources of nitrates in drinking water is the use of fertilizers on crop land. If nitrates in the fertilizer are not taken up by plants, they can end up in run-off and contaminate groundwater sources. Shallow groundwater supplies near freely-draining crop land are particularly susceptible to exceedances in nitrate levels.1 In water treatment plants, wastewater is often treated with nitrates to reduce odours associated with septicity or treated with bacteria that have the potential to biologically convert ammonia to nitrate. High levels of nitrates in drinking water may indicate that treated wastewater effluent or human or animal waste products are contaminating raw water sources.2

Regulations:

The limit for nitrate in drinking water is 50 micrograms per litre (µg/L).  

Health/Environmental Concerns:

Infants are extremely susceptible to the negative health impacts caused by nitrates in drinking water. Upon ingestion, nitrates are converted to nitrites which have been shown to cause shortness of breath or blue baby syndrome in children less than 6 months of age.1 Additionally, the International Agency for Research on Cancer determined that there is inadequate evidence to classify nitrates as carcinogenic, but there is some evidence that nitrite, when combined with other compounds, may increase an individual’s risk for cancer.3 If contaminated effluent or human/animal waste reaches raw water sources, bacteria or other chemicals that are harmful to human health may also be present in water.

Action:

When nitrate exceedances do occur, it is important that consumers—especially those caring for infants—are alerted and instructed to use alternate drinking water supplies. Contact your Water Services Authority if you believe your water may be contaminated or require treatment. Costly methods such as ion exchange, reverse osmosis, and electrodialysis can be used to reduce nitrate levels, but contamination should ultimately be mitigated at the source to provide long-term protection.1 If drinking water makes you ill, contact a doctor right away.

1 Guide to the Parameters in the European Communities. What’s in your water?; S. I. No. 278 of 2007; National Federation of Group Water Schemes: Ireland.

2 Guidelines for Drinking Water Quality. Nitrates in Drinking Water; Vol. 2; World Health Organisation: Switzerland, 1996.

3 Toxicological Profile for Nitrates and Nitrites; Agency for Toxic Substances and Disease Registry, U.S. Department of Health and Human Services: Atlanta, GA, 2006.