Nitrates and Human Health

  • January 30, 2018

Nitrate Contamination and Human Health

 

 

The claim that nitrate in drinking water above EPA limits is an urgent health problem provides the basis for lawyers and activists to attack family dairy farms. This article shows how wrong they are on several counts.

 

Are the concerns about nitrate in drinking water justified?
Is it correct to blame dairy farmers?

Nitrate in drinking water is the fundamental issue. The activists claim that dairy farms are contributing massive amounts of nitrate to groundwater through manure storage lagoons and application of manure to fields. They claim dairy contamination poses a very significant risk to human health. This is wrong.

The EPA established a maximum of 10 parts per million of nitrate in drinking water. This was based on a 1940s study that related some cases of infant methemoglobinemia (IM) – also called “blue baby syndrome” to newborn infants fed formula using well water high in nitrate. That study has since been fully discredited by numerous more recent studies as we will show. It has even been discredited by EPA scientists who researched the assumed link. One of the most recent studies by eminent medical researchers concludes that given a much improved understanding of the causes, “perhaps the current MCL for nitrate in drinking water of 10 mg/L (or 10 ppm) should be revisited.”

We challenge these activists to produce science studies that refute the conclusion of all recent studies we have seen that show the causal link between nitrate in groundwater and blue baby syndrome is wrong. Since we have been publicly presenting this documentation for nearly three years, we believe activists such as Puget Soundkeeper Alliance, Western Environmental Law Center and RE Sources are choosing to ignore current science as it interferes with their fundamental claim against farmers.

In this document we will first show that nitrate levels are actually declining in areas of intensive dairy farming. This brings into question the effort of activists to end dairy farming because of the claim that these farmers are “killing our country.” Second, we show that nitrate levels above the EPA level are widespread in wells across the nation where farming has occurred for generations. In Eastern Washington, there is significant nitrate levels in groundwater where there are no dairy farms.

The Department of Ecology monitors nitrate in wells in Whatcom County. This shows the decline of nitrate levels since 2005. From an October 2016 Ecology report.

 

There are about 90 dairy farms located in a relatively small area in Whatcom County. Ecology’s well testing shows improvement in water quality with declining nitrate levels in areas where a number of dairy farms are located.

 

This map, available at the link under point 2, shows that nitrate above EPA limit exists in 24% of wells where previous farming activity combined with rain or heavy irrigation existed. This includes areas in Eastern Washington where no dairies exist.

 

In addition to demonstrating that recent science shows the basis for the EPA limit is false, we also provide detailed information on the health benefits of nitrates in diets. The DASH diet, promoted by the National Institutes of Health, is beneficial for cardiac performance because it is high in vegetables that contain about 2500 times the nitrate allowed in drinking water. We simply note the vast difference in position of these two federal agencies to point out that the claims about urgent health risks activists claim are caused by dairy pollution are not credible. Farmers fully recognize that as long as the EPA holds to the current limit, it is their obligation to do all they can to limit or eliminate nitrate contamination. The information provided above about protective measures and farmer stewardship show that while the EPA standard stands farmers will do all they can to limit or eliminate contamination.

1. Nitrate levels in areas of intensive dairy farming are declining.

Claims of a water quality crisis by anti-farm activists lose credibility when confronted by the facts of improving water quality. Whatcom County, with about 90 dairy farms, is a favored target of these activists who go so far as to claim the aquifer shared with Canada is “closed” presumably to public consumption. Nothing could be further from the truth as the Department of Ecology has shown.

2. Nitrate levels above EPA limit are widespread in farm country –– even without dairy farms

There is intense focus on dairy farms as the alleged cause of nitrate contamination, including in a discredited EPA 2012 science report on causes of nitrate contamination in the Yakima Valley. These actions ignore the level of nitrate in groundwater in almost all areas of intensive farming across the nation.

This federal government website provides information on the location of wells likely to have nitrate in groundwater above the EPA limit:

https://water.usgs.gov/nawqa/nutrients/pubs/wcp_v39_no12/

It shows that 24% of wells have nitrate above the EPA limit. The accompanying map shows that vulnerability is based on nitrogen input combined with soil conditions. The map of Southeast
Washington demonstrates that high nitrate in this area is common in farming areas regardless of the presence of dairy farms.

3. The link between nitrate in well water and “blue baby syndrome” shown to be based on a mistaken 1947 science report

Statements about the public health risk by activists are often extreme such as made by Puget Soundkeeper Alliance and the Western Environmental Law Center. These were published on the What’s Upstream website which states nitrates are: “acute contaminants that produce immediate (within hours or days) health effects upon exposure.” This is clearly intended to frighten the uninformed but when the facts about health risks are known, these statements seriously diminish the credibility of those making those claims.

A major concern raised is the supposed link between nitrate levels in groundwater and infant methemoglobinemia or “blue baby syndrome” The suggestion was that this risk was considerable even at or near the EPA level of 10 parts per million. Farmers understand that the EPA Maximum Contamination Level or MCL on nitrate continues in effect. But there is clear and compelling evidence that the current limit, set by a now discredited science study of 1945, is not supported by the preponderance of more current studies.

Federal agencies, with the exception being the EPA, are making it clear that science studies relating to the role of nitrate in human health are pointing away from the outdated reports. The Public Health statement of the Agency for Toxic Substances and Disease Registry (ATSDR) states:

EPA relied on a 1940s study to establish the limit of nitrate in groundwater. Since then, that study has been shown to be mistaken and the most recent science studies show that blue baby syndrome is caused by genetic factors and bacteria.

“Most people are not exposed to levels of nitrate and/or nitrite that would cause adverse health effects. Young infants (<6 months of age) appeared to be particularly sensitive to the effects of nitrite on hemoglobin after consuming formula prepared with drinking water that contained nitrate at levels higher than recommended limits; some of these infants died. The cause of methemoglobinemia (a change to hemoglobin that decreases the ability to transport oxygen to tissues) in many of these infants may have been gastroenteritis from bacteria or viruses in the drinking water or from other sources not related to nitrate.” [Emphasis added]

In 2013 Dr. Bruce Macler from EPA Region 9 presented a summary of studies of health risks from nitrate in drinking water. After noting the EPA limit was set based on the 1940s study, Dr. Macler stated: “Clinical studies of nitrate exposure alone showed little or no methemoglobinemia.” Perhaps most interesting is Dr. Macler’s review of a study of methemoglobinemia in California completed in 2000. He notes that 42 cases in California over 13 years were studied. “None specifically associated with nitrates.” “Only four of the 42 cases were in areas where there were wells.”

The error made by the original study in 1945 by Hunter Comly that linked methemoglobinemia to nitrate in drinking water is now quite well understood and is widely reported in the literature. The researcher only considered the high levels of nitrate in the drinking water which was also contaminated by bacteria. Subsequent studies compounded the error by failing to consider the role of bacteria, genetics and other factors. Numerous studies since then have pointed out that error, which is succinctly summarized here:

“Methaemoglobinaemia is a side-effect of gastroenteritis and is not caused by nitrate but by nitric oxide, which is produced in a defensive reaction stimulated by gastroenteritis. The latter may be caused by a bacterium or a virus. The association of methaemoglobinaemia with nitrate may have arisen because early cases of the condition were often associated with wells polluted with bacteria, and the same pollution increased the nitrate concentration.”

An article from Environmental Health Perspectives by Mary H. Ward, et al., from 2005 and published on the NIH website provides evidence that factors other than nitrate contribute to methemoglobinemia.

“Methemoglobinemia in infants fed formula made with well water with high nitrate levels was first reported in 1945 by Comly (1945). The regulatory level for nitrate in drinking-water supplies was determined after a survey of infant methemoglobinemia case reports in the United States indicated that no cases were observed at drinking-water nitrate levels < 10 mg/L nitrate-N (Walton 1951). Because an estimated 22% of domestic wells in agricultural regions of the United States exceed the nitrate MCL (U.S. Geological Survey, unpublished data), it is likely that significant numbers of infants are given water containing > 10 mg/L nitrate-N. Nevertheless, few cases of methemoglobinemia have been reported since the MCL was promulgated.”

The authors point out that numerous recent studies show that exposure to nitrate alone does not result in the infant disease: “Recently, the role of nitrate exposure alone in causing methemoglobinemia has been questioned (Avery 1999; Fewtrell 2004; Hanukoglu and Danon 1996).” They concluded:

 

 

The DASH diet developed by the National Institutes of Health recommends vegetables high in nitrate for heart health. Some of these vegetables have nitrate levels 2500 times that limit set on nitrate in drinking water by the EPA. Wouldn’t it be great if federal officials would talk to each other and get this sorted out?

“Clearly, we need to better understand the interaction of factors that lead to methemoglobinemia to assess the relative importance of each factor and to identify the conditions under which exposure to nitrate in drinking water poses a risk of methemoglobinemia.

The need to better understand the factors contributing to methemoglobinemia was answered by a 2014 medical report published on the National Institutes of Health Website called Reexamining the Risks of Drinking-Water Nitrates on Public Health authored by Alyce M. Richard, MD, James H. Diaz, MD, DrPH, and Alan David Kaye, MD, PhD. Dr. Richard is now with Harvard Medical School. The report examines in-depth the medical issues surrounding this disease and concludes:

Because research refutes exogenous nitrate-to-nitrite sources as causes of IM [infantile methemoglobinemia] and supports endogenous nitrite production secondary to genetic abnormalities or nitric oxide generation in an inflamed infant gut as causative mechanisms for IM, perhaps the current MCL for nitrate in drinking water of 10 mg/L (or 10 ppm) should be revisited.

Those promoting the link between nitrate in drinking water and blue baby syndrome frequently refer to Eastern European countries that have had much higher levels of incidence of this disease than Western European nations or the US. The paper referred to above by Ward et. al., states “in Romania, 20% of 2,000 wells had nitrate levels > 23 mg/L as nitrate-N (Jedrychowski et al. 1997). Studies from other countries, including China, Botswana, Turkey, Senegal, and Mexico, report private well water levels that exceed the WHO guideline, in some instances at levels > 68 mg/L nitrate-N (WHO 2004a).”

Another researcher from the UK, Lorna Fewtrell reported: “In 1985, WHO reported that > 1,300 cases of methemoglobinemia (with 21 fatalities) occurred in Hungary over a 5-year period. Indeed, up until the late 1980s methemoglobinemia was a serious problem in Hungary (Hill 1999). Although there are reports of high nitrate concentrations in drinking water (i.e., > 50 mg/L nitrate) from around the world (Hoering and Chapman 2004), these are rarely paralleled by reports of methemoglobinemia. Where illness has been reported, many of the cases predate the early 1990s, and Hanukoglu and Danon (1996) have proposed that the apparent decline in the incidence of methemoglobinemia is suggestive of an infectious etiology.”

4. EPA: nitrate in groundwater does not cause cancer

A Washington state government official reported in a public meeting that even very low levels of nitrate in drinking water cause cancer. This accusation has also been made frequently by some activists. They reference the Iowa study published in the 2001 issue of Epidemiology which concludes that low levels of nitrate in drinking water are associated with increased incidence of some forms of cancer. This study generated the expected news headlines and has been used extensively by activists to ramp up concerns about nitrate and cancer. The study was done on the basis of a survey mailed to Iowa residents. The authors note: “There are several important limitations to our exposure assessment that require comment.” Those limitations provide adequate reason why the study results are inconsistent with and not supported by a number of other studies that show no link to low levels of nitrate in drinking water and cancer. Dr. Macler, the EPA Region 9 scientist referenced above, also noted in his presentation that since 2002 the EPA has determined that nitrate was not a carcinogen. This was after the Iowa study was published. Dr. Macler’s 2013 presentation offered this conclusion: “Net effect = zero.” This was because of the admitted weakness of the study and the numerous other studies that show no link.

Family dairy farming in Washington state is under severe attack by Puget Soundkeeper Alliance, Western Environmental Law Center and the lawyers they hire. But the accusations about dairy pollution are wrong. So are their accusations about the health risks of nitrate in groundwater.

Save Family Farming, organized by farmers across the state, is working to set the record straight and stop the harmful legal and public attacks on farmers.

One of the most comprehensive analyses of the health impact of nitrate in drinking water was published by the University of Nebraska-Lincoln in 2008:

“About 50 epidemiological studies have been made since 1973 testing the link between nitrate and stomach cancer incidence and mortality in humans, including Forman et al. (1985) and National Academy of Sciences (1981). The Chief Medical Officer in Britain (Acheson, 1985), the Scientific Committee for Food in Europe (European Union, 1995), and the Subcommittee on Nitrate and Nitrite in Drinking Water in the USA (NRC,1995) all concluded that no convincing link between nitrate and stomach cancer incidence and mortality had been established…Based on the above findings showing no clear association between nitrate in drinking water and the two main health issues with which it has been linked [stomach cancer and methemoglobinemia–ed note], some scientists suggest that there is now sufficient evidence for increasing the permitted concentration of nitrate in drinking water without increasing risks to human health (L’hirondel et al., 2006; Addiscott, 2005).”

This comports with the statement by the ATSDR: “The International Agency for Research on Cancer (IARC) determined that there is inadequate evidence for the carcinogenicity of nitrate in food or drinking water and limited evidence for the carcinogenicity of nitrite in food (based on association with increased incidence of stomach cancer).” In a concluding slide looking at various studies that purported to link nitrate to cancer, Dr. Macler concluded: “No smoking gun.”

5. Instead of representing a serious health risks, most now agree that nitrate is beneficial.

At a very minimum the health risks previously associated with nitrate in drinking water, particularly at the very low levels set by the EPA, are being seriously questioned if not moving toward a strong consensus of little to no risk. But there is another side to the story: the positive benefits of nitrate in the diet.

In the University of Nebraska-Lincoln study mentioned above, the authors make note of the potential positive benefits: “On one hand there is evidence that shows there is no clear association between nitrate in drinking water and the two main health issues with which it has been linked, and there is even evidence emerging of a possible benefit of nitrate in cardiovascular health.”

The DASH diet, based on research from the National Institutes of Health, is a good example as it promotes eating vegetables known to be high in nitrate such as beets, spinach and celery. For example, one serving of spinach contains about 2500 times the 10 parts per million in water that the EPA set as the MCL. The DASH diet website states:

“The healthy DASH (Dietary Approaches to Stop Hypertension) diet plan was developed to lower blood pressure without medication in research sponsored by the US National Institutes of Health. The first DASH diet research showed that it could lower blood pressure as well as the first line blood pressure medications, even with a sodium intake of 3300 mg/day! Since then, numerous studies have shown that the DASH diet reduces the risk of many diseases, including some kinds of cancer, stroke, heart disease, heart failure, kidney stones, and diabetes. It has been proven to be an effective way to lose weight and become healthier at the same time. It is full of fabulous, delicious, real foods. All of these benefits led to the #1 diet ranking by US News & World Report in 2011, 2012, 2013, and 2014.”

Scientific evidence for the health benefits of nitrate in the diet have been established for some time as this 2009 article in the American Journal of Clinical Nutrition, shows: “As such, the dietary provision of nitrates and nitrites from vegetables and fruit may contribute to the blood pressure–lowering effects of the Dietary Approaches to Stop Hypertension (DASH) diet.”

This website does a good job of explaining how the science on nitrate and human health is changing and why nitrate in our diets is beneficial:

Nitrates are beneficial. Where did I get it wrong?

 

Government officials on the one hand communicate publicly that nitrate represents a very serious health risk but then others recommend that we eat salads or vegetables because of high nitrate. This conflict needs to be resolved. The review of available science will lead to the conclusion that EPA’s limit on nitrate in drinking water dating back to the 1960s deserves a re-evaluation.

Save Family Farming Asks Government Agencies and Their Representatives to Tell the Truth About Nitrate Sources and Health Risks.

In January 2018 a public presentation by a government official prompted farmers to challenge the story being told by this representative and the agency. A letter was sent to the official and agency leaders. However, this official and agency are not the only ones to misinterpret or inaccurately communicate the current science around nitrate and drinking water. We present this information to help set the record straight.

Nitrates in Drinking Water and Public Health

The health risk of nitrates in well water is a foundational issue for environmental activists calling for major changes in farming regulations. As presented by the Western Environmental Law Center and the website they co-sponsor, whatsupstream.com, the risks are extreme and the need for change is very urgent.

In addition to calling nitrates “acute contaminants that produce immediate (within hours or days) health effects upon exposure,” other health risks have been repeated in media reports where the environmental law group spokesperson on this issue has been quoted.

Along with the very frightening claims about the extreme dangers, the farm opponent activists claim that farms are primarily responsible for the nitrates in drinking water. This paper will examine both of these claims in more detail, focusing on the known health risks of nitrates. In short, what we will show is that the current prevailing view of nitrates is that they provide an important health benefit and that the health risks, particularly of blue baby syndrome, previously linked to nitrates in drinking water have largely been revisited. The initial research, dating back nearly 60 years, has been found to be faulty and recent reports, including by the EPA, show that the association of blue baby syndrome or methemoglobinemia is inaccurate.

We will also show that concerns raised by farm opponents related to manure lagoons and nitrate contamination are faulty and that if nitrates were indeed the health risk activists believe them to be, a more appropriate target for change would be home septic systems. Specifically, they should focus on the growing conversion of farmland to hobby farms, a semi-urban development in farmland with heavy use of residential septic systems.

 

 

What are nitrates?

Nitrates start with nitrogen. Nitrogen makes up about 78% of our atmosphere. While nitrates can occur naturally in the ground, the nitrates we are talking about mostly come from fertilizer. Nitrogen is essential for plants to grow. So nitrogen is a key component of both organic fertilizer (manure) and commercial fertilizer. Nitrogen in the atmosphere and in fertilizer takes on a number of chemical forms including ammonium, nitrite, nitrate, nitrous oxide, nitric oxide and others. This conversion into other forms is called the nitrogen cycle which is well explained here. Microbes or bacteria are mostly involved in converting nitrogen and that includes conversion in the soil into nitrates.
Nitrates are very soluble so if there is too much in the soil it can filter down and enter groundwater.

What does the government say about nitrates in groundwater?

Almost any government agency will repeat the same basic message that is provided by the EPA:
EPA has established a MCL for nitrate in drinking water of 10 mg/L under the Safe Drinking Water Act (SDWA). EPA regulates nitrate in public drinking water systems because nitrate concentrations greater than the MCL may cause health problems. Exposure to excess nitrate can result in methemoglobinemia (blue-baby syndrome) in infants and susceptible individuals, which can lead to death in extreme cases (Ward 2005). Some studies have shown a positive association between long-term exposure to nitrate in drinking water and risk of cancer and certain reproductive outcomes, while other studies have shown no association (Ward 2005).”

It is expected that any lower level government agency would simply repeat this statement. The problem we have is that while the EPA statement is carefully constructed (“exposure…can result in…” and “positive association between…” it does not accurately reflect current science. When these cautious statements are twisted by environmental activists to attack farmers, this lack of clarity becomes a much greater problem.

 

Celery is one of many leafy vegetables touted for their health benefit because they are high in nitrates.

Are nitrates good for you or bad for you?

One major problem with the EPA statement is that it ignores clear and compelling evidence that in most cases nitrates are good for you. In fact, many who have studied the issue suggest nitrates should be considered a nutrient rather than a contaminant. We suggest you do your own online search for health benefits and risks of nitrates. But one website, authoritynutrition.com says:
If nitrite loses an oxygen atom, it turns into Nitric Oxide, an important molecule. Nitric Oxide (NO) is a short-lived gas, which has various functions in the body. Most importantly, it is a signalling molecule. It travels through the artery wall and sends signals to the tiny muscle cells around the arteries, telling them to relax. When these cells relax, our blood vessels dilate and blood pressure goes down. This is actually how the well known drug nitroglycerin works. It is a source of nitrate, which quickly turns into nitric oxide and dilates the blood vessels. This can prevent or reverse angina, chest pain that occurs when the heart muscle doesn’t get enough oxygen due to reduced blood flow.
Dietary nitrates and nitrites can also turn into Nitric Oxide, dilate the blood vessels and lower blood pressure. Studies have shown that nitrate supplements, such as beet roots or beet root juice, can reduce blood pressure by up to 4-10 mm/Hg over a period of a few hours. The effect may be weaker in women. Elevated blood pressure is one of the strongest risk factors for heart disease and stroke (the world’s biggest killers), so the importance of this can not be overstated.
This report in the American Journal of Clinical Nutrition agrees:
“The strength of the evidence linking the consumption of nitrate- and nitrite-containing plant foods to beneficial health effects supports the consideration of these compounds as nutrients.”
The well-know DASH diet, or Dietary Approaches to Stop Hypertension, recommends foods high in nitrates. This academic report showed the current World Health Organization’s limits cannot be supported by the evidence:
The hypothetical high-nitrate DASH diet pattern exceeds the World Health Organization’s Acceptable Daily Intake for nitrate by 550% for a 60-kg adult. These data call into question the rationale for recommendations to limit nitrate and nitrite consumption from plant foods.”
Another article raises in this prestigious journal raises similar questions:
Nitrate from fertilizer accumulates in vegetables and fruit, and large-scale livestock production yields huge amounts of manure rich in nitrate that seeps into groundwater. Therefore, keeping nitrate concentrations below legal limits is a struggle for farmers. In this issue of the Journal, Hord et al (1) challenge these limits. Other authors have already pointed out that the evidence for adverse effects of nitrate is inconsistent and that nitrate may actually be beneficial (2, 3). Hord et al (1) go one step further: they claim that nitrate and nitrite should be considered as nutrients.”

The abstract in this article neatly summarizes the current state of science on nitrates:
Thus, evidence for adverse effects of dietary nitrate and nitrite is weak, and intakes above the legal limit might well be harmless. This is not unusual in regulatory toxicology. Many chemicals and contaminants might well be safe at intakes above their legal limit. Authorities willingly accept that possibility; erring on the safe side with many chemicals is justified if it keeps just one true carcinogen out of the food supply. But the trade-off changes when excessive caution deprives us of beneficial substances, as claimed by Hord et al for nitrate. In that case, the evidence for harm needs to be weighed against the potential benefit.

Nearly all dairy farms in Washington are family farms owned and operated by often third and fourth generation farmers. They operate under rigorous manure nutrient regulations which specify zero discharge and which require safe application of manure nutrients to minimize excess nitrates.

Conclusions

Save Family Farming does not specifically represent farmers and is not controlled by farmers. Farmers understandably are reluctant to call into question standards set by the US government, particularly if they are being accused of the ones causing the contamination. There is a risk that others will see it as an effort to avoid blame and avoid having to make expensive changes to protect water. Dairy regulations mandate application and management of manure specifically to protect water from nitrates. Every farmer we know is very serious about not only following the law but being responsible stewards of the water and the environment including protecting against nitrate contamination.

But those interested in the facts, the truth and the science behind some very strong, even outrageous claims about the extreme dangers of nitrates, will want to further investigate this important issue.
Farmers do apply nitrogen to their crops. Nitrogen is used by plants which convert it to nitrates and nitrites. For an increasing number of nutrition experts, this is a very good thing. A primary benefit of nitrates in the diet is strengthening the cardiovascular system. We have not seen any studies of persons routinely drinking well water high in nitrates to see if the incidence of heart problems are reduced, but there is reason to believe that this is likely.

While the general scientific consensus about nitrates and blue baby syndrome appears to be that there is little if any connection between nitrates in drinking water and this illness. Most recent science focuses on the genetic disposition toward this disease combined with exposure to bacteria, either bacteria in water or food they ingest or “endogenous” bacteria from their own diarrhea. Since high nitrates in drinking water can also signal bacteria contamination, we believe it is important that parents of infants under six months old have their well water tested regularly for nitrates and bacteria. An abundance of caution would lead parents of infants under six months to use bottled water to mix infant formula.
What we have a hard time justifying is the lack of willingness on the part of the EPA to acknowledge more publicly that the association between nitrate contamination in drinking water and blue baby syndrome is not what they thought it was many years ago. They should make it clear that no scientific evidence supports the possibility of nitrates as a carcinogen. To use high nitrates in drinking water to force dairy farmers out of business or to require billions of dollars in water treatment seems harder and harder to justify. We believe it more than reasonable to ask that they make it clear to those behind whatsupstream.com and the Western Environmental Law Center that the claims they make about “acute contaminants” are not based on science and not based on best information available to the EPA.

 

Why did the EPA set the limit for nitrates in drinking water at 10 parts per million?

When the EPA in 1963 established that limit, they had best available science guiding them. Numerous studies and reports make clear that the basis for this limit was research conducted by the American Public Health Association in the late 1940s or early 1950s. They studied a small number of blue baby syndrome cases, saw that there was a link between infants drinking water with high nitrates and concluded that nitrates in drinking water caused the illness. Since there were no identified cases of nitrates below 10 parts per million, the EPA established that as the “safe” level.

This association between high nitrates in drinking water and methemoglobinemia has been questioned in numerous studies. This report provides a summary of many more recent findings and an historical perspective on the EPA limits:

The federal MCL for nitrates was established in 1963 and is based on data from a mere five blue baby cases identified in a survey conducted in 1949 by the American Public Health Association (APHA). During the 1940s, a number of blue baby cases connected to water contaminated with high nitrate levels was reported in medical journals. It was known that nitrites were toxic and caused methemoglobinemia in humans of all ages. On the theory that gut bacteria can convert nitrate (NO3) into toxic nitrite (NO2), the APHA concluded the evidence warranted limiting infant exposure to nitrates. (At the time, many infants were fed powdered infant formula reconstituted with well or tap water, exposing them to nitrates in drinking water.)
In an effort to determine a safe level of nitrates, the APHA surveyed state health departments asking for information on blue baby cases “definitely associated with nitrate-contaminated water.” All but one state responded to the survey. Seventeen states submitted data on a total of 214 blue baby cases. Most cases occurred at nitrate levels greater than 40 ppm, while five were reported at nitrate levels between 11 and 20 ppm. Since no blue baby cases were reported at levels below 10 ppm, this became the federal MCL.
No one knows if the information gathered by the APHA in 1949 is accurate. Many of the survey’s blue baby cases were never formally diagnosed. Moreover, the survey is badly flawed because nitrate concentration data were often collected months after the blue baby event; nitrate levels in drinking water can vary dramatically over relatively short periods of time.
Finally, APHA never considered the fact that blue baby syndrome can be caused by internal (endogenous) factors, without any exposure to external nitrates or nitrites. APHA simply assumed that in blue baby cases where nitrates were present, the nitrates were the cause.
The most common cause of endogenous blue baby syndrome appears to be gastrointestinal maladies, such as gastroenteritis and diarrhea. Symptoms of gastrointestinal disorders, such as diarrhea and vomiting, are present in a majority of blue baby cases linked to nitrate-contaminated water.
Moreover, doctors in the 1940s were unable to cause blue baby syndrome in hospitalized infants by exposing them to formula with 100 ppm nitrate alone. Blue baby syndrome occurred only when the infants were exposed to 100 ppm nitrate nitrogen and pathogenic bacteria. Even then, the effects weren’t dramatic. Thus, the relatively low nitrate levels in the five blue baby cases from the APHA survey were likely unrelated to the blue baby occurrences.”

A very balanced scientific assessment by a group of respected scientists clarifies the error:

The link between nitrate and the occurrence of methaemoglobinaemia was based on studies conducted in the 1940s in the midwest of the USA. In part, these studies related the incidence of methaemoglobinaemia in babies to nitrate concentrations in rural well water used for making up formula milk replacement. Comly (1945), who first investigated what he called “well-water methaemoglobinaemia,” found that the wells that provided water for bottle feeding infants contained bacteria as well as nitrate. He also noted that ‘In every one of the instances in which cyanosis (the clinical symptom of methaemoglobinaemia) developed in infants, the wells were situated near barnyards and pit privies.’ There was an absence of methaemoglobinaemia when formula milk replacements were made with tap water. Re-evaluation of these original studies indicate that cases of methaemoglobinaemia always occurred when wells were contaminated with human or animal excrement and that the well water contained appreciable numbers of bacteria and high concentrations of nitrate (Avery, 1999). This strongly suggests that methaemoglobinaemia, induced by well water, resulted from the presence of bacteria in the water rather than nitrate per se. A recent interpretation of these early studies is that gastroenteritis resulting from bacteria in the well water stimulated nitric oxide production in the gut and that this reacted with oxyhaemoglobin in blood, converting it into methaemoglobin (Addiscott, 2005).”

While numerous more current studies point to the link between bacteria and blue baby syndrome, even studies dating back to the original flawed one showed that pointing at nitrates was an error. This, from the American Journal of Clinical Nutrition, states:

The nitrate in the offending wells [in the original study] came from fecal contamination. It is now thought that methemoglobinemia was not caused by nitrate but by fecal bacteria that infected the infants and produced nitric oxide in their gut. Nitric oxide can convert hemoglobin to methemoglobin. The key role of intestinal infection rather than nitrate was confirmed by an experiment in 1948, in which infants who were fed 100 mg nitrate · kg−1 · d−1 did not develop methemoglobinemia. When they were fed bacteria from contaminated wells, however, methemoglobinemia did develop (3). This suggests that the nitrate concentrations commonly encountered in foods and water are unlikely to cause methemoglobinemia.”

The Leopold Institute for Sustainable Agriculture, associated with Iowa State University argues that there is not sufficient scientific evidence for the EPA to change the limit. Yet, they offer compelling proof that such evidence does exist:

Because nitrate reduces to nitrite, there has been a longstanding concern about potential sources of nitrate, particularly in tap and well water used for infant formula. However, blue baby syndrome has been rarely diagnosed in the United States in recent years.
In the July 1999 issue of the journal Environmental Health Perspectives, Alex Avery of the Hudson Institute argues that evidence from clinical evaluation of 40 years of blue baby syndrome cases indicates that environmental sources of nitrate (particularly drinking water) may have little to do with development of the condition (Avery 1999a). He contends that gastrointestinal infection and related production of nitric oxide (which metabolizes to nitrite) may be the primary cause of many cases of blue baby syndrome. Avery concludes that the U.S. Environmental Protection Agency’s 10 parts per million (ppm) limit for nitrate in drinking water is too stringent, and that the standard should be relaxed (see sidebar story that follows).
Avery takes his argument one step further in a June 24, 1999, Des Moines Register essay, and states that there is no proof that nitrate in drinking water poses a real threat for adults (Avery 1999b). He also questions the cost-benefit of nitrate removal processes in municipal drinking water treatment.”

Soil scientists have long studied nitrates in the soil and groundwater and published their findings in publications such as Soil Use and Management. Authors T. M. Addiscott and N. Benjamin state:

Methaemoglobinaemia is a side-effect of gastroenteritis and is not caused by nitrate but by nitric oxide, which is produced in a defensive reaction stimulated by gastroenteritis. The latter may be caused by a bacterium or a virus. The association of methaemoglobinaemia with nitrate may have arisen because early cases of the condition were often associated with wells polluted with bacteria, and the same pollution increased the nitrate concentration.”

By far the strongest evidence of the disappearing direct link between nitrates in drinking water and blue baby syndrome comes from the EPA itself. In a presentation dated June 19, 2013 (available on this page below), Dr. Bruce Macler of Region 9 of the USEPA, reviewed the health effects of nitrates. He begins by reviewing the EPA’s view of nitrates and health including the position that “nitrate and nitrite effects are related to oral ingestion can lead to methemoglobinemia in infants.” He says this was first established in 1945 and this is the basis for the limits in drinking water. He also states clearly that EPA’s position as of 2002 is that nitrates are not a human carcinogen. The presentation then goes through an explanation of blue baby syndrome and its causes. The presentation includes this statement:

“Clinical studies of nitrate exposure alone showed little or no methemoglobinemia.”

Perhaps most interesting is Dr. Macler’s review of a study of methemoglobinemia in California completed in 2000. He notes that 42 cases in California over 13 years were studied. “None specifically associated with nitrates.” “Only four of the 42 cases were in areas where there were wells.” Macler goes on to note that the EPA reconsiders its Maximum Contamination Levels every six years but so far “found no new health information to indicate a need to revise MCLs.” We wonder if those doing the review have seen Dr. Macler’s and the many other scientific studies relating to nitrates as a beneficial nutrient versus nitrates as a health risk.

Is their current state of scientific consensus around the issue of nitrates and blue baby syndrome? Wikipedia has proven a reliable information source because it is edited by so many including those most knowledgeable. We’ll leave this issue with their summary:

Humans are subject to nitrate toxicity, with infants being especially vulnerable to methemoglobinemia due to nitrate metabolizing triglycerides present at higher concentrations than at other stages of development. Methemoglobinemia in infants is known as blue baby syndrome. Although nitrates in drinking water were once thought to be a contributing factor, there are now significant scientific doubts as to whether there is a causal link.[17][18] Blue baby syndrome is now thought to be the product of a number of factors, which can include any factor that causes gastric upset, such as diarrhoeal infection, protein intolerance, heavy metal toxicity etc., with nitrates playing a minor role. Nitrates, if a factor in a specific case, would most often be ingested by infants in high nitrate drinking water. However, nitrate exposure may also occur if eating, for instance, vegetables containing high levels of nitrate.”


Aren’t there other health risks associated with nitrates that cause concern?

Some government documents and websites including the EPA’s make reference to other possible health risks including stomach cancer. It seems clear that the studies that once linked nitrates to some cancers have been contradicted. Some government websites do make it clear that nitrates do not cause cancer: this from the Florida health department:
Nitrates are not known to cause cancer.

Scientists Addiscott and Benjamin referenced earlier state:
Four epidemiological studies sought a link between stomach cancer and nitrate but did not find one. The incidence of this cancer has also declined during the last 30 years, while nitrate concentrations in water have increased. Nitrate preserves, rather than threatens, health.”
The professional journal Epidemiology in a January 2011 article stated flatly:

Overall, nitrate and nitrite ingestion were not associated with stomach cancer risk.”
Dr. Macler, the EPA Region 9 scientist reference above is definitive on this important subject. In his presentation he asks the question: Is Nitrate a Human Carcinogen? And answers it unequivocally:
“USEPA does not currently believe so, based on lack of supporting data and substantial negative data”

To substantiate this he refers to a large epidemiological study in Iowa involving 21,000 women. This study, he says, found some positive correlations and some negative ones. Bottom line he concludes: “No smoking gun.”

​We must ask, if this is the EPA’s position, why does it continue to place warnings about “possible cancer risks” on its website, knowing that such statements can be and will be taken by groups such as the Western Environmental Law Center and made into something they are not?

Agency for Toxic Substances and Disease Registry reports on nitrate. References blue baby syndrome, noting that this may be from bacteria. Also no solid link of nitrate in groundwater to cancer or birth defects.