Testing for Nitrate & Nitrite in Water Samples: 7 Things Your Lab Wants You to Know

What are Nitrate & Nitrite? 

Nitrate and nitrite are nitrogen-oxygen based chemicals which occur naturally in water, soil, air, plants, and the human body. There are also man-made sources of nitrate and nitrite, and these include fertilizers, food preservatives, pharmaceutical drugs, and explosives. 

 

Nitrate and nitrite can be found in both groundwater and surface water, and are commonly detected during routine well water testing. Nitrate and nitrite become a concern in drinking water when levels exceed the limits (MCLs) set by the EPA. 

 

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The U.S. Environmental Protection Agency (EPA) has established the maximum contaminant levels (MCLs) for Nitrate & Nitrite in Drinking Water as follows:
10 mg/L for nitrate
1.0 mg/L for nitrite

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Where are High Levels of Nitrate & Nitrite Commonly Found?

 

Nitrate and/or nitrite contamination can be caused by fertilizer runoff, septic tank waste/leaks, manure / animal waste, as well as erosion of natural deposits. Communities with large numbers of aging septic tanks and/or working farms are particularly vulnerable to high levels of nitrate/nitrite in soil, groundwater and drinking water. 

 

Public water systems routinely test nitrate/nitrite levels, but private well owners must perform their own testing for these and other common contaminants in order to be sure that their tap water is safe to drink. As with many contaminants, you cannot see, smell, or taste nitrate/nitrite in drinking water. 

 

 

image source: usgs.gov circa 2015

 

Health Risks of Nitrate and Nitrite

 

Exposure to nitrate and nitrite mainly occurs through consuming food and water that contain these chemicals, however most people are not exposed to concerning levels. According to the World Health Organization, consumption of nitrates in drinking water is not considered a significant health risk to otherwise healthy adults in industrialized countries. Nitrate and nitrite have not been classified as carcinogenic by the EPA.

 

The real concern over nitrate in drinking water and subsequent established EPA water standards stem from a 1945 case study  and subsequent investigations which showed that infants who consumed baby formula mixed with nitrate-contaminated water were at risk of developing methemoglobinemia, also known as "blue-baby syndrome.”

 

 

 

This condition is caused when the body converts nitrates into nitrites, which then bind to hemoglobin, forming methemoglobin.  Methemoglobin is unable to carry oxygen. The low levels of oxygen in the baby’s bloodstream cause the baby’s skin and nail beds to develop a blueish tint, which is often the first indicator, hence the name “blue-baby syndrome.”

 

In addition to blue skin and nail beds, babies with methemoglobinemia (blue baby syndrome) may also develop:

• fever
• difficulty breathing
• vomiting
• diarrhea
• lethargy
• increased salivation
• loss of consciousness
• seizures
• coma 
• death (severe cases)

 

According to American Scientist, only two cases of "well-water methemoglobinemia" have been reported in the US since the mid-1960s, and zero since 2000. Improved water quality standards, public awareness, and an increase in breastfeeding may all be contributing to this decline. 

How to Test for Nitrate and Nitrite 

Environmental laboratories use Ion chromatography (IC) to test for nitrate and nitrite. IC is a form of liquid chromatography, capable of separating and measuring ionic species based on type, size, and resin interactions. 

 

As the instrument runs, the sample passes through a chromatographic column, where the ions present in the sample are adsorbed by the constituents in the column. As an eluent liquid flows through the column, the adsorbed ions elute from the column, based on their affinity to the column material.

 

The different separation times of each ion is called the retention time. As the individual ions elute from the column, their concentrations can then be quantified. The results will be indicated on your environmental laboratory report. 

 

 

7 Things Your Lab Wants You to Know About Nitrate and Nitrite Analysis:

• Nitrate and Nitrite can each be reported separately on your lab report, or as a combined result (Total Nitrate). 

 

• Your project needs will dictate your reporting preference, and must be noted on the Chain of Custody Form, as many aspects of the project will be affected depending on whether you choose ‘separate’ or ‘total’ (glassware, holding times, reporting limits).

 

• When you communicate your testing needs to the lab, they will provide you with the correct glassware (preserved or unpreserved bottles).

 

• FOR SEPERATE Nitrate / Nitrite results

-holding time: 48 hours

-DO NOT preserve your sample(s) with sulfuric acid.

 

• FOR A COMBINED Nitrate / Nitrite result (Total Nitrate) 

-holding time: 28 days 

-Sample(s) MUST be preserved with sulfuric acid.

 

• Samples preserved with sulfuric acid require a dilution due to the interference caused by the acid, so the reporting limit is much higher. 

 

The EPA released this update in November 2020, stating that if a sample exceeds 5 mg/L with a total nitrate and nitrite analysis, subsequent analysis should be conducted using nitrate specific methods.* 

 

Conclusion

Sources & Resources:  

• US Environmental Protection Agency, EPA Chemical Contaminant Rule: Phase II/V Rules:  https://www.epa.gov/dwreginfo/chemical-contaminant-rule-phase-iiv-rules-code-federal-regulations-0

 

• Agency for Toxic Substances & Disease Registry, Nitrate Nitrite Health Effects: https://www.atsdr.cdc.gov/csem/nitrate-nitrite/health_effects.html

 

• National Library of Medicine, "Blue Babies and Nitrate Contaminated Well Water: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1638204/

 

• NH Department of Environmental Services, Interpret Your Water Report: https://www4.des.state.nh.us/DWITool/

 

• USGS Maps for Nitrate Levels & Other Contaminants: https://waterwatch.usgs.gov/wqwatch/?pcode=00630