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Definition

Nitrate is an inorganic compound composed of one atom of nitrogen (N) and three atoms of oxygen (O); the chemical symbol for nitrate is NO₃. Nitrate is not normally dangerous for the health unless it is reduced to nitrite (NO₂).

Description

• Chemical Name: Nitrate

· Regulatory name: Nitrate

• Molecular formula: NO₃^-
• Molecular weight: 62 g/mol
  

Nitrate in drinking water: health effects

Nitrate is one of the most frequent groundwater pollutants in rural areas. It needs to be regulated in drinking water basically because excess levels can cause methaemoglobinaemia, or "blue baby" disease. Although nitrate levels that affect babies are not dangerous for older children and adults, they do indicate the possible presence of other more serious residential or agricultural pollutants, such as bacteria or pesticides.
The origin of nitrate in groundwater is primarily from fertilizers, septic systems, and manure storage or spreading operations. Fertilizer nitrogen not taken up by plants, volatilized, or carried away by surface runoff ends up in the groundwater in the form of nitrate. This makes the nitrogen unavailable to the plants, and can also raise the concentration in groundwater above the admissible levels for drinking water quality. Nitrogen from manure can be similarly lost from fields, barnyards, or storage locations. Septic systems remove only half of the nitrogen in wastewater, leaving the other half to leach to groundwater, this way raising groundwater nitrate concentrations.

Nitrate drinking water standards

Nitrate in drinking water is measured either in terms of the amount of nitrogen present or in terms of both nitrogen and oxygen. The federal standard for nitrate in drinking water is 10 mg/l nitrate-N, or 50 mg/l nitrate-NO3, when the oxygen is measured as well as the nitrogen. Unless otherwise specified, nitrate levels usually refer only to the amount of nitrogen present, and the usual standard, therefore, is 10 mg/l.
Short-term exposure to drinking water with a nitrate level above the health standard is a potential health problem especially for babies. Babies drink large quantities of water considering their body weight, especially if water is used to mix powdered or concentrated recipes or juices. Also, their digestive systems are inmature, and thus more likely to allow the reduction of nitrate to nitrite. The nitrite in the digestive tract of babies can cause methaenoglobinaemia.

How do we consume nitrate?: nitrate in our diet

Nitrate occurs naturally in many vegetables, such as lettuce and spinach, and is produced by microbes in the human gut, with the result that only a small part of the nitrate in the body comes from drinking water.

The intake of nitrate from vegetables is unlikely to cause health problems because very little of this nitrate is converted to nitrite. Meat products account for less than 10 percent of nitrate in the diet, but 60 to 90 percent of the nitrite consumed. This is basically because sodium nitrite is added to foods such as hot dogs, bacon, or ham. Fruits, grains, and dairy products contribute almost no nitrate or nitrite to people's diets.

Nitrate and the World Health Organization (WHO)

In the European standards for drinking water, 2^nd edition, published by the WHO after the meeting in Geneva 1970, we find the following:
Constituents in water which, if present in excessive amounts, may give rise to trouble:

Substance	Nature of trouble which may arise	Approximate level above which trouble may arise
Nitrate (as NO3)	Danger of infantile methaemoglobinaemia if the water is consumed by infants.	- Reccommended: less than 50 mg/l. - Acceptable: 50 to 100 mg/l. - Not reccommended: more than 100 mg/l

Methaemoglobinaemia: a disease caused by nitrate excess

Definition: Clinical condition arising from the excessive conversion of haemoglobin to methaemoglobin, which is incapable of binding and carrying oxygen. Methaemoglobin is formed when iron in the haemoglobin molecule is oxidised from Fe²⁺ to Fe³⁺.


Toxicology: Methaemoglobin occurs when haemoglobin is oxidised at a rate exceeding the normal enzymatic capacity to reduce the haemoglobin. Many agents may be responsible for this oxidation. The most frequently found are:

• Aniline
• Benzocaine
• Chlorates
• Chloroquine
• Dapsone
• Ground or surface water contaminated with nitrates
• Nitrates
• Nitrites
• Nitrophenol
• Phenazopyridine
• Primaquine
• Sodium nitroprusside
• 4-dimethylaminophenol

Methaemoglobinaemia could also be developed due to non-toxic causes, as congenital enzyme deficiencies.

Symptoms:

A typically greyish cyanosis can be observed when the level of methaemoglobin exceeds 1.5 g/dL, which is about 10% of the total haemoglobin in a normal individual. At this level, the patient may not notice any symptoms yet.

The symptoms of methaemoglobinaemia are usually those related to impaired oxygen delivery (headache, weakness, tachycardia and breathlessness) and develop gradually as concentrations of methaemoglobin rise above 20%.Concentrations higher than 50% result in severe hypoxaemia and central nervous system depression.Concentrations higher than 70% may cause death.

For individuals that suffer from anaemia, cardiac failure or pulmonary disease the symptoms of hypoxia may appear at lower percentage levels of methaemoglobin.

How to eliminate nitrates from your water

An easy solution to eliminate the nitrites in the water is to oxidize them to nitrates . This can be done by injecting ozone in the water. Ozone is a very oxidizing chemical that would oxidize all the nitrites into nitrates, thus eliminating the toxicity caused by nitrites.

Nitrite

Definition
Nitrite is the univalent radical NO₂ or a compound containing it, such as a salt or an ester of nitrous acid.

Description

• Chemical Name: Nitrite

· Regulatory name: Nitrite

• Molecular formula: NO₂^-
  
• Molecular weight: 46 g/mol

Biofilm

A biofilm is a thin usually resistant layer of microorganisms (as bacteria) that form on and coat various surfaces (as of catheters or water pipes).

The reason why we talk about biofilms here, is because nitrifiers occur predominantly as surface attached biofilms. This means that Nitrosomas could be coating the inside of your water pipes, and therefore producing nitrites that could be polluting your water.

Health effects
When nitrite enters the bloodstream, it reacts with the hemoglobin and forms a compound called methemoglobin. This compound reduces the blood's capacity to carry oxygen. The oxygen level decrease
s
, and babies show signs of a disease called methemoglobinemia also known as “blue baby disease”.
The most obvious symptom of methemoglobinemia is the appearance of a bluish tone on the skin, particularly around the eyes and mouth. If quickly discovered, this disease can be successfully treated with an injection of methylene blue, which changes methemoglobin back to hemoglobin. The condition is extremely serious if it’s not treated: death takes place when 70 per cent of the body's hemoglobin has been converted to methemoglobin.
It has been shown to be a link between babies deaths from methemoglobinemia and high levels of nitrate in water.


Livestock health problems
The rumen is the first division of the stomach of a ruminant animal, in which most food collects immediately after being swallowed and from which it is later returned to the mouth as cud for thorough chewing. Tha bacteria present in the rumen of ruminant animals such as cattle and sheep convert nitrate to nitrite, causing nitrate poisoning.
Pigs and chickens have no rumen, because they are monogastric animals, so they quickly throw out nitrate in their urine. Young monogastric animals, however, are similar to human babies in that they are highly susceptible to nitrate poisoning until their digestive systems develop.
Amongst all the monogastric animals horses are the most susceptible to nitrate poisoning because they have a large cecum which acts as a rumen, converting nitrate to nitrite.
High nitrate levels can be found in plants due to overfertilization or stress. This can harm livestock much more than if the nitrate is ingested when drinking water with high nitrate concentration.
Some of the symptoms of methemoglobinemia in animals are troubles in coordination, difficulties in breathing, blue coloring of mucous membranes, vomiting and abortions. Reduction in the milk production can be noticed without the cow showing any symptoms. Under suspicion of your animals being poisoned by nitrate, your veterinary can carry a test and, if necessary, inject them some methylene blue, the antidote.
Recently, various other health problems have been linked to high concentrations of nitrate. Some studies suggest that an increase in esophageal and stomachal cancers may be related to N-nitrosamines, organic compounds formed in the mouth or digestive system by the interaction of nitrite (formed from nitrate) with compounds containing organic nitrogen (secondary amines). N-nitrosamines are potent animal carcinogens.

How to eliminate nitrites from your water

An easy solution to eliminate the nitrites in the water is to oxidize them to nitrates (as we said before, nitrates are much less toxic than nitrites). This can be done by injecting ozone in the water. Ozone is a very oxidizing chemical compound that would oxidize all the nitrites into nitrates, thus eliminating the toxicity caused by nitrites.