Elevated nitrate concentrations in groundwater - causes and health implications

  • joeturner
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Re: Ground water pollution from leach pit toilets (question from India)

As I said, the simple relationship is disputed

The exposure assessment was based on levels of nitrate in drinking water greater than the WHO guideline value of 50 mg/L. No exposure–response relationship, however, could be identified that related drinking-water nitrate level to methemoglobinemia. Indeed, although it has previously been accepted that consumption of drinking water high in nitrates causes methemoglobinemia in infants, it appears now that nitrate may be one of a number of co-factors that play a sometimes complex role in causing the disease. I conclude that, given the apparently low incidence of possible water-related methemoglobinemia, the complex nature of the role of nitrates, and that of individual behavior, it is currently inappropriate to attempt to link illness rates with drinking-water nitrate levels.

Drinking-Water Nitrate, Methemoglobinemia, and Global Burden of Disease: A Discussion by Lorna Fewtrell

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  • joeturner
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Re: Elevated nitrate concentrations in groundwater - causes and health implications

This review article also discusses some of the uncertainties about the health effects of nitrates in water:


When does Nitrate become a Risk for Humans? by Powlson et al.

The "blue baby" studies were conducted in the 1940s - even if there is a link between nitrates in water and methaemoglobinaemia, there have been a tiny number of total cases.
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  • muench
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Re: Elevated nitrate concentrations in groundwater - causes and health implications

(FYI, the previous thread has now been split in two, in order to focus on the nitrate aspect; the thread where this one was split off from is this one:
forum.susana.org/forum/categories/193-gr...-question-from-india )

Thanks Mughal for the detailed description of the WHO position and thanks to Joe for pointing out publications showing doubts aboue the simple cause and effect links.

I am wondering if the WHO publications are on the more conservative side, i.e. rather erring on the side of caution until more research has been conducted?

Interesting that the article by Lorna Fewtrell from 2004 which Joe cited starts with:

On behalf of the World Health Organization (WHO), I have undertaken a series of literature-based investigations examining the global burden of disease related to a number of environmental risk factors associated with drinking water.

I also checked what the Working Group 11 factsheets are saying about nitrate:

The recent check list ( www.susana.org/en/resources/library/details/2155 ) says:

Nitrate pollution, for example, is frequent and even though the relative public health risk is lower than microbial contamination, high nitrate levels should be checked for and avoided.

The working group factsheet from 2012 ( www.susana.org/en/resources/library/details/98 ) says:

When aerobic conditions prevail, nitrate may be the final
product, which, at elevated concentrations (>50 mg/l), can
be harmful to humans, especially babies. Worldwide, in
developed and developing countries alike, many water
supply wells show increased levels of nitrate above the
WHO guideline value of 50 mg/l. This can be due to fertiliser
application or mismanagement of human and animal
excreta, but also due to natural conditions.

Nitrate is in itself relatively non-toxic, however, upon
ingestion, it is partially converted by bacteria in the mouth to
nitrite. The formation of nitrite is especially important as it
reacts with haemoglobin, the oxygen carrying constituent of
red blood cells, to produce methaemoglobin which cannot
transport oxygen (ARGOSS, 2002). Methaemoglobinaemia
(also known as “blue baby” syndrome) occurs mostly with
children under three months of age. This was reported in
only 2000 cases between 1945 and 1972, most of which
were not fatal (Cave and Kolsky, 1999).
In the period 1986
to 1996 however, 3,000 babies and young children from
Romania’s rural areas were hospitalised with acute infantile
methaemoglobinaemia. 3.5% of these cases were lethal
(EEA and WHO, 2002).

However the above mentioned number of deaths is still low
in contrast to those caused by diarrhoea and associated
diseases (Cave and Kolsky, 1999). The actual problem with
nitrate in groundwater used as drinking water is its
persistence under aerobic conditions; it takes advanced,
high cost treatment processes to remove nitrate from
contaminated drinking water. Thus long term accumulation
should be prevented.


I look forward to understanding this better so that finally, we can make sure that we have also the right information on Wikipedia where it currently says:


Nitrate in drinking water [edit source | edit]

A sort of "blue baby syndrome" can also be caused by methemoglobinemia.[2][3] It is widely believed to be caused by nitrate contamination in groundwater resulting in decreased oxygen carrying capacity of hemoglobin in babies leading to death. The groundwater can be contaminated by leaching of nitrate generated from fertilizer used in agricultural lands, waste dumps or pit latrines.[4] Cases of blue baby syndrome have for example been reported in villages in Romania and Bulgaria where the groundwater has been polluted with nitrate leaching from pit latrines.[5] However, the linkages between nitrates in drinking water and blue baby syndrome have been disputed in other studies.[6][7] The syndrome outbreaks might be due to other factors than elevated nitrate concentrations in drinking water.[8]

and also here:


Nitrate [edit source | edit]
In addition to the issue of pathogens, there is also the issue of nitrate pollution in groundwater from pit latrines, which has led to numerous cases of "blue baby syndrome" in children, notably in rural countries such as Romania and Bulgaria.[3] Nitrate levels above 10 mg/L (10 ppm) in groundwater can cause "blue baby syndrome" (acquired methemoglobinemia).[4]

Nitrate can also enter the groundwater via excessive use of fertilizers, including manure. This is because only a fraction of the nitrogen-based fertilizers is converted to produce and other plant matter. The remainder accumulates in the soil or lost as run-off.[5] High application rates of nitrogen-containing fertilizers combined with the high water-solubility of nitrate leads to increased runoff into surface water as well as leaching into groundwater, thereby causing groundwater pollution.[6][7][8] The excessive use of nitrogen-containing fertilizers (be they synthetic or natural) is particularly damaging, as much of the nitrogen that is not taken up by plants is transformed into nitrate which is easily leached.[9]

The nutrients, especially nitrates, in fertilizers can cause problems for natural habitats and for human health if they are washed off soil into watercourses or leached through soil into groundwater.

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  • margriets
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Re: Elevated nitrate concentrations in groundwater - causes and health implications

I fully agree with the statement that nitrate in drinking water is a minor health concern in comparison with microorganisms/pathogens. Nevertheless, in regions with nitrate polluted drinking water is nitrate a health concern for babies.

WECF experienced in rural Romania, Moldova and Ukraine extreme high nitrate concentrations (up to 900 mg/l) in individual and public wells and which water is used untreated by villagers. The groundwater level varied from 5 m up to 25 m. Yearly cases of methemoglobinemia (Blue baby disease) were reported (period 2002-2010). Even breast fed babies were concerned because extra liquid (tee) was given to the babies during periods with high temperatures.
Mostly the people were not aware of the risks of unsafe water and the quality of the well waters not known. In general the hygienic conditions and awareness on safe food preparation and water usage was low , which may contribute to the cases of Methemoglobinemia.

In many countries the incidence of methaemoglobinemia may not be registered on national level and hence underestimated.

In the publication “Incidence Particularities of Methemoglobinemia Cases in Bacău County During 2000 – 2005 period”, is stated, between 2000-2005, in 8 counties from Eastern Romania, there have been registered 844 cases of acute methemoglobinemy, with an annual incidence average rate on Moldavia of 2.68% with Incidence particularities of methemoglobinemia cases in Bacău county 213 territorial variations from 0.58‰ (Suceava county) to 5‰ (Botosani county), and annual from 1.76 in 2004, to 3.45‰ in 2000. See pesd.ro/articole/nr.2/18.%20Popescu_PESD_2008.pdf

Remarkable in this study is that in Bacau county 23 % and in Moldavia county 13.5% of the cases occurred where well water indicated a nitrate concentration of <50mg/l; Furthermore a considerable percentage (>10%) of the cases concerned babies in the age of 4-6 month and even older than 6 month. In contrary literature is mostly mentioning up to a age of 3 or 4 month. In 30% of the cases there was an association with an acute Diarrheic disease.

Nitrate is well soluble in water and depending on several factors such as depth of groundwater, permeability of the soil layer, weather events and human activities nitrate concentration in groundwater can fluctuate.

In our water safety planning projects for example in rural regions of Eastern Europe or Caucasus, a part of the activities is a seasonal monitoring of the nitrate concentration in drinking water (well water) and assessing to potential sources of the nitrate pollution. Observed was that the concentration of nitrate can fluctuate during the year from less than 50mg/l up to more than 250 mg/l. Observed decreased nitrate levels were caused e.g. by the seasonal slaughtering of pigs kept in households backyard, resulting in less manure infiltration in soil (groundwater), decrease of fertilisation of the fields in autumn and winter

Increase of nitrate levels was often observed in regions with unsafe management of human excreta (pit latrines) and animal manure, after starting agricultural /gardening activities in springtime and after heavy rain events, See:

In any case Blue baby disease can and should be prevented:
- by raising awareness of the population and local doctors on the risks of nitrate for babies
- by regular testing drinking water with simple nitrate test sticks (at least water used by families with pregnant and young mothers.

Best regards

Margriet Samwel, WECF
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  • joeturner
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Re: Elevated nitrate concentrations in groundwater - causes and health implications

Thanks margriets, that is an interesting report.

I find this table in particular fascinating

This tells us that more than 50% of all cases have not been found with wells at the highest nitrate concentrations. In fact, given that one of the categories is much bigger than all the others (100-500 mg/l compared to <50 and 50-100), it is not possible to say that whether there is a link between the concentration and the incidence of "blue baby syndrome".

Whilst it is clear that Bacau has a high percentage of the total cases measured in the period, and it is also clear that a high number of wells have high levels of nitrate, this table does not tell us whether there is a link between the one and the other.

We also know that methemoglobinemia is caused by a range of public health issues.
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  • mmadrid
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Re: Elevated nitrate concentrations in groundwater - causes and health implications

Hi folks,

Well, looks like we agree that nitrate might be less critical than pathogenic organisms when it comes to disease burden, and assuming that sanitation facilities are the only sources. However, I should say that both its long stability/persistence and the difficulty for nitrate to be removed, give it some importance.

In highly populated areas having a high latrine density, a well-drained soil, a vulnerable unconfined aquifer, and low rainfall recharge, sure, nitrate may be an issue. If not (seasonally) monitored, long term accumulation may occur. High concentrations will not decrease rapidly even if the load is reduced or removed. This constitutes even a major problem near coastal waters having limited riparian zone (i.e. limited organic-rich sediments and therefore limited potential for denitrification) due to the risk of eutrophication. More case studies in these settings are needed.

I would also like to thank Jan for sharing the IISc Bangalore study on the use of the BES-PRB layer for denitrification. I think that sanitation system design is a good alternative to reduce the passage of nitrate into the groundwater. We should keep working in the design of cost-effective (and socially-acceptable) sanitation systems. Solutions can range from the placement of semipermeable seals at the bottom of the pits to reduce nitrate leaching and promote denitrification, to the installation of reactive layers such as the one being developed by IISc Bangalore. Robertson et al. (2008) at the University of Waterloo (Canada) also conducted some studies using a sawdust-mixture-PRB layer to remove nitrate:

Another interesting study being conducted at Waterloo included the use of basic oxygen furnace slag (BOFS) reactive media to treat pathogens (Stimson et al., 2010):

In combination with other passive technologies, such as the use of vetiver grass (constructed wetlands), they can result in affordable treatment technologies.

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  • margriets
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Re: Elevated nitrate concentrations in groundwater - causes and health implications

Dear Joe
Indeed we have to conclude the table presented in the Moldovian study does not present all the information needed for a clear interpretation of the incidence of Blue Baby Syndrome. The rate of wells with the respectively nitrate concentrations used for preparing baby food and drinks and the distribution of the cases of Methemoglobinemia is not presented. The study shows in the investigated target regions blue baby disease is still an issue and can occur even if the nitrate concentration is less than 50mg/l.

As you indicated, methemoglobinemia is caused by a range of public health issues. In particular unhygienic conditions, intestinal weaknesses of the baby may contribute to the occurrence of nitrate reducing microorganisms in baby´s stomach.
Interesting is a study on infant methemoglobinenemia carried out by Hillel I. Shuval and Nachman Gruener in 1977 (very old….). Never the less, one of their conclusions was that the phenomenon of methemoglobenemia is not universal and may be local nutritional practices as well genetic factors may bear a major influence on the prevalence of the disease.
( books.google.nl/books?id=1WQhBQAAQBAJ&pg...20%20Nitrate&f=false )

I like to thank you Miguel, for the link on the removal of nitrate by wood particles. A very interesting and low-cost method!
Prevention of nitrate infiltration by badly designed sanitation systems into groundwater should have a high priority. Putting barriers for the pits could be a first step, although in many regions the final disposal of the still unsafe sludge is an issue.
To overcome that problem WECF introduced in many countries urine diverting dry toilets. The UDDT are in particular well accepted in regions with high groundwater tables.

Best greetings
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  • mmadrid
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Re: Elevated nitrate concentrations in groundwater - causes and health implications

Hi everyone,

I just came across this document by the US ATSDR (December 2013):

“… there have been cases of infantile acquired methemoglobinemia through ingestion of baby formula prepared using nitrate contaminated well water. Ingestion of nitrate-containing water is a common cause of methemoglobinemia in infants, especially those living in rural areas. EPA suggests maintenance testing of private well water annually (to include nitrates, coliform bacteria, total dissolved solids and pH)…”

This documents cites these two references from the early 90’s:

“Continuing importance of nitrate contamination of groundwater and wells in rural areas”
(Jonson & Kross, 1990)

“Methemoglobinemia: nitrate toxicity in rural America”
(Kross et al., 1992)

Tracking some more recent references I also found this one by Richard et al. (2014):

“Reexamining the Risks of Drinking-Water Nitrates on Public Health”

“Early epidemiological studies demonstrated significant associations between high groundwater nitrate levels and elevated methemoglobin levels in infants fed drinking water–diluted formulas. However, more recent epidemiological investigations suggest other sources of nitrogenous substance exposures in infants, including protein-based formulas and foods and the production of nitrate precursors (nitric acid) by bacterial action in the infant gut in response to inflammation and infection”.

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