Item #1:
City of Alhambra opens $13.8 million water treatment plant mainly to rid groundwater of nitrates.
Read here: http://www.sgvtribune.com/ci_10625398?source=rss
Item #2:
City of Alhambra Water Quality Report:
Amount of nitrates in groundwater:
5.9 to 36 parts per million
Average: 19 ppm
Source
http://www.cityofalhambra.org/government/city_clerk/downloads/2007CCR.pdf
Item #3:
From the University of California Extension
II NITRATES
Scott Wetzlich
Source: http://extoxnet.orst.edu/newsletters/n111_91.htm
Synopsis:
In summary, nitrates do not pose a great risk to the general public. Nitrates and nitrites can cause some health problems, but only at very high levels. Compared to the amount we receive in our food, the normal levels of nitrates in drinking water should not be a concern. An exception to this is in the case of infants and a few rare susceptible adults who are consuming water with levels above the 45 ppm limit. Infants are highly susceptible to nitrate poisoning due to a number of factors not applicable to older children or most adults. Presently, methemoglobinemia would appear to be the only health problem linked to nitrates and nitrites for humans.
Infants and susceptible adults should not drink water that has nitrate levels greater than 45 mg/l. Instead, they should use bottled water or water from a safe source. Contaminated water can be cleaned by deionization, reverse osmosis, or distillation. Normal water filters will not rid the water of nitrates. Private well owners can drill deeper wells to access uncontaminated water. Spinach should be eaten soon after purchasing, and all leftovers should be discarded.
Full Text:
Nitrates and nitrites in our diets have been a concern for around a hundred years. An 1895 account of cattle deaths from nitrate contaminated corn stocks was one of the earliest recorded accounts of a nitrate poisoning in food or feed. Recently, high nitrate levels in drinking water have become a concern to many Californians, especially those who get their water from wells. Although the health effects from nitrate poisoning are a concern for infants and a small group of susceptible adults, the amount normally encountered does not pose a significant risk to the general public.
The average daily intake of nitrate is around 100 mg and about 12 mg for nitrite. Vegetarians have a much higher daily intake (about 250 mg) because of the high nitrate content of vegetables. Less than 10 percent of the nitrates we ingest come from our drinking water; most are found in our food. Approximately 9 percent of the nitrates we ingest come from processed meats where it is used as a preservative and as a coloring agent. The greatest amount of nitrates we encounter come from vegetables like lettuce and spinach. A little over one-fifth of the nitrites we ingest come from cured meats. The highest levels originate in our own saliva, where bacteria in our mouths change nitrates to nitrites.
Vegetables and cured meats are the main source of nitrates in our diet. Vegetables with high levels of nitrates include lettuce with averages of 850 parts per million (ppm), celery at 2340 ppm, spinach at 1860 ppm, beets at 2760 ppm, and broccoli at 780 ppm. There are many factors which affect the nitrate levels in plants. The species and variety of plant are very important. Nitrate levels also vary with the part of the plant (leaf, stem, root, etc.) and maturity of the plant. Environmental factors include; drought, high temperature, shading, nutrient deficiencies, excessive fertilizers, and plant damage from insects and herbicides. The average American ingests 86 mg of nitrate a day from vegetables alone; 18.9 mg from lettuce, 16 mg from celery, 4.2 mg from spinach, 5.5 mg from beets, and 14.2 mg from potatoes. Although it would appear that vegetables would be a high risk factor in nitrate poisoning, very few cases have ever been documented. This could be because of the ascorbic acid content of most vegetables, which have protective effects against nitrate poisoning.
Cured meats account for 15.5 mg of nitrate in the American daily diet. They also account for about 4 mg of nitrite a day. Nitrates and nitrites are used on cured meats to give it the distinctive pink color, to prevent rancidity, and to prevent the growth of Clostridium botulinum spores. Nitrate and nitrite levels in cured meats have been set by the FDA at 120 ppm. The FDA also recommends 550 ppm ascorbate or sodium erythorbate which have similar effects as ascorbic acid in vegetables.
Fresh spinach contains high levels of nitrates, but very little nitrite. Storage at room temperature greatly increases the levels of nitrites and decreases the levels of nitrates. Since nitrites are more toxic than nitrates, this can be a serious problem. One study found nitrite levels rose from 30 ppm to 3550 ppm after just four days at room temperature. Refrigerating the spinach will delay the process, but not prevent it. Frozen spinach does not undergo this process. This conversion is caused by certain bacteria and by plant enzymes. Factors affecting eventual nitrite levels are the initial nitrate levels in the plants, the activity of plant enzymes, the storage conditions (aerobic, anaerobic, temperature, etc.), and the extent of microbial contamination.
There have been a number of nitrite poisonings in infants from spinach. One of the first recorded incidents was in Germany. Two infants died of methemoglobinemia after being fed spinach puree containing 661 ppm nitrite. In another case, 14 infants suffered methemoglobinemia after eating spinach that was high in nitrates and had been cooked at least a day in advance. The nitrates had become nitrites during storage. Infants can tolerate fairly high levels of nitrate in spinach, but not nitrite. Infants fed spinach containing 680 ppm nitrate at 16-21 mg nitrate per kg body weight per day for a week had no adverse effects.
Although food accounts for the vast majority of the nitrates we are exposed to, nitrates in drinking water are of a greater concern to the public. The levels that are usually found in drinking water should be of little concern, but in the case of severe contamination, care should be taken for a small segment of the population. Infants are at the greatest risk from nitrate poisoning. Drinking water averages about 1.3 ppm nitrate ion. This would give an average total daily dose from water of 2.6 mg per person per day. The Maximum Contaminant Level (MCL) allowed by law is 45 ppm nitrate ion, or 10 ppm when based on the nitrogen content of nitrate (nitrate-nitrogen). According to a 1985 survey, six percent of the rural wells in the U.S. exceeded this standard. The World Health Organization has proposed acceptable daily intake levels (ADI's) of 5 mg nitrate ion per kg body weight and 0.4 mg nitrite ion per kg body weight in addition to naturally occurring levels we ingest everyday.
The main sources of nitrate contamination of drinking water are animal feedlots, agricultural fertilizers, manured fields, and septic systems. Other sources include industrial wastewater, sanitary landfills, and garbage dumps. Ammonia fertilizers readily breakdown in the presence of oxygen to form nitrates. Nitrates are very water soluble, and can easily move through the soil into the groundwater. It is estimated that up to 40 percent of the nitrogen applied to fields as fertilizers is converted into nitrates and enters water sources as run-off and leachate.
Nitrates themselves are not toxic in the amounts we normally encounter. The toxicity of nitrates is a result of their conversion into nitrites within the body. Nitrites easily enter the blood stream and cause a condition called methemoglobinemia. Hemoglobin is the compound in the red blood cells responsible for transporting oxygen throughout the body. The nitrites oxidize the ferrous (+2) iron molecule in the hemoglobin to the ferric (+3) state. Hemoglobin containing a ferric iron molecule is unable to carry oxygen, and is called methemoglobin. Too much methemoglobin in our system causes methemoglobinemia. The condition is characterized by cyanosis (a bluish color to the skin), stupor, and cerebral anoxia (a lack of oxygen to the brain). About one percent of the hemoglobin in adults is normally methemoglobin, and a little less than two percent in children is methemoglobin. Levels between 10 and 20 percent can cause methemoglobinemia, and levels greater than 60 percent can cause death.
Infants under 4 months of age are at greater risk to the toxic effects of nitrites than are older children and adults. The methemoglobinemia caused by nitrites in infants is called blue baby disease. There are many factors to account for the greater susceptibility of infants. Infants consume a greater amount of fluid compared to body weight than adults do. Thus, if the same amount of water is consumed, an infant will have a much higher nitrate to hemoglobin ratio than an adult. The most important factor involved is that infants secrete very little gastric acid into their stomach. The pH in their stomach ranges from 5 to 7, which is favorable for the growth of bacteria that convert nitrates into nitrites. The pH of an adults stomach is around 2 or 3. Infants also have a deficiency in methemoglobin reductase. This is an enzyme that converts the non oxygen carrying methemoglobin back into the oxygen carrying hemoglobin. Finally, 60 to 80 percent of the hemoglobin in a newborn is hemoglobin F (fetal hemoglobin), which has a greater affinity for nitrites than hemoglobin A (adult hemoglobin). Hemoglobin F is rapidly replaced by hemoglobin A after birth, and by the third month of an infants life, only 30 percent of the hemoglobin is hemoglobin F.
The first case of an infant poisoning due to nitrates in drinking water was reported in 1944. Since then, the number of cases has climbed steadily. There were about 2000 cases of methemoglobinemia in infants reported between 1945 and 1970, with approximately 160 being fatal. Infants consuming milk formula made with water containing nitrate levels greater than the 45 ppm allowable limit are at greatest risk.
The majority of methemoglobinemia cases have been caused by drinking water with nitrate levels greater than 100 ppm. A small percentage of adults are at greater risk than most and these include pregnant women with an enzyme deficiency (glucose-phosphate dehydrogenase), and adults with a hereditary deficiency in methemoglobin reductase. Methemoglobinemia can be detected and treated quite easily. Treatment is by injection of methylene blue or by oral administration of ascorbic acid.
Acute poisoning from nitrates has occurred in adults after accidental ingestion. Eight to fifteen grams of sodium or potassium nitrate is fatal. Symptoms include severe abdominal pain, bloody stools and urine, weakness, and collapse. Nitrites are much more lethal, with only 1 g causing death. Symptoms of nitrite poisoning include flushing of the face and extremities, headache, cyanosis, nausea, vomiting, abdominal pain, and collapse. Nitrates are less toxic because of their rapid elimination in the urine.
Another class of compounds associated with nitrates and nitrites are nitrosamines. Nitrosamines are formed when nitrites react with secondary and tertiary amines on food in the stomach. The main sources of amines in our diet are fish, vegetables, and fruit juices. Nitrosamines have been detected in cured meats, but at very low levels of 20 parts per billion (ppb) or less. Seventy-five to eighty percent of the nitrosamines studied have been shown to cause cancer in laboratory animals. These include cancers of the liver, respiratory tract, kidney, urinary bladder, esophagus, stomach, lower gastrointestinal tract, and the pancreas.
Epidemiologic studies have yet to link nitrates and nitrites to cancer in humans. One reason is that nitrosamines occur in the ppb or part per trillion range. Doses in the ppm or parts per thousand were needed to induce the cancers in animals. High consumption of cured meats has been associated with certain cancers, however, high consumption often indicates a lack of fresh food and vegetables which provide protective effects against nitrosamines. The production of nitrosamines is inhibited by vitamins A and E, sulfamate, butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), gallic acid, and various amino acids and proteins.
Finally, a few animal studies have shown very high levels of nitrates to have teratogenic effects. Extrapolation of this data to humans is based on 100 percent conversion of nitrate to nitrite in the human body. However, it is estimated that only about 5 percent is actually converted. If this is taken into account, the estimated human daily dose of nitrite is 1000 times or more below the level needed to cause reproductive effects in animals. With this in mind, there is no conclusive evidence to show that nitrates or nitrites could have a teratogenic effect in humans.
Nitrates and nitrites are also a concern for ranchers and farmers. The effects of nitrates have been extensively studied in ruminants (cattle, sheep, goats, etc.). Ruminants have a very good ability to adapt to nitrates and nitrites and to develop tolerances to them. Sheep have a higher tolerance than cattle because they have higher methemoglobin reductase levels.
Acute symptoms of nitrate poisoning in farm animals include gastrointestinal problems, vomiting, salivation, diarrhea, colicky signs, and frequent urination. Inconsistent signs of chronic poisoning include abortion, decreased milk production, infertility, decreased milk fat, Vitamin A deficiency, and slow weight gain.
Forage and rations containing 2% nitrate or less are considered safe for cattle and sheep. Poisoning is best avoided by acclimating mature animals to the high levels of nitrates in feed or water if present. Sudden changes in nitrate levels can bring on a toxic reaction. Ruminants adapt better to high nitrate levels when urea is added to their feed.
In summary, nitrates do not pose a great risk to the general public. Nitrates and nitrites can cause some health problems, but only at very high levels. Compared to the amount we receive in our food, the normal levels of nitrates in drinking water should not be a concern. An exception to this is in the case of infants and a few rare susceptible adults who are consuming water with levels above the 45 ppm limit. Infants are highly susceptible to nitrate poisoning due to a number of factors not applicable to older children or most adults. Presently, methemoglobinemia would appear to be the only health problem linked to nitrates and nitrites for humans.
Infants and susceptible adults should not drink water that has nitrate levels greater than 45 mg/l. Instead, they should use bottled water or water from a safe source. Contaminated water can be cleaned by deionization, reverse osmosis, or distillation. Normal water filters will not rid the water of nitrates. Private well owners can drill deeper wells to access uncontaminated water. Spinach should be eaten soon after purchasing, and all leftovers should be discarded.
Source: http://extoxnet.orst.edu/newsletters/n111_91.htm
Art Craigmill
Extension Toxicologist
UC Davis
Marylynn Yates
Hydrology/Toxicology Specialist
UC Riverside
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