Update, April 2020

NITRATE IN DRINKING WATER
Nitrate is one of the most common contaminants in drinking water.
Nitrate naturally occurs at low levels in ground and surface water.
However, elevated levels of nitrate are associated with contaminationfrom commercial fertilizer, manure or effluent from municipal orindustrial wastewater treatment plants. EWG data for 2015-2017 showthat detectable levels of nitrate are present in the drinking waterserved to 231 million Americans. And drinking water in agriculturalareas frequently has the highest nitrate concentrations.

CURRENT LEGAL LIMITS AND THE NEED FOR A NEW
APPROACH TO PROTECT PUBLIC HEALTH
The federal limit of 10 milligrams per liter, or mg/L, equivalent to parts per million,
for nitrate in drinking water, was set in 1962 and has not been updated. This standard
was developed to prevent acute cases of methemoglobinemia, which causes an infant
to suffer from oxygen deprivation in the blood after ingesting excessive nitrate.
More recent studies, discussed briefly below, have found increased risk forother troubling health outcomes at nitrate levels significantly below 10 mg/L. A
comprehensive scientific review of nitrate drinking water concentrations and related
impacts on human health showed strong evidence of an increased risk of colorectal
cancer, thyroid disease and neural tube defects at nitrate concentations in drinking
water below the current legal limit of 10 mg/L.1
Based on more recent studies showing correlation between serious health impacts
and nitrate levels significantly below 10 mg/L, the Environmental Protection
Agency and the states should reassess legal limits for nitrate in drinking water.
In 2017, the EPA’s Integrated Risk Information System program began a review ofhealth effects from nitrate in drinking water.2 However, the agency later suspended
the review and did not prioritize nitrate reassessment for 2019.3
To ensure safe drinking water, protect public health and wisely use limited publicresources, regulatory and programmatic action to reduce sources of nitratecontamination should be implemented immediately when levels in ground or surface
water are above naturally occurring background levels. It is irresponsible to wait toimplement nitrate source reduction measures until nitrate levels are at or near thecurrent legal limit of 10 mg/L. This delayed approach has failed to protect publichealth and has saddled the individuals and communities least able to afford drinking
water treatment with millions in costs.

NITRATE DRINKING WATER CONCENTRATIONS OF 1 TO 5MG/L AND ABOVE MAY INCREASE CANCER RISKDanish researchers have found an elevated risk of colorectal cancer associatedwith drinking water concentrations of just 1 mg/L – tenfold lower than the U.S. SafeDrinking Water Act limit.4 A study conducted in Spain and Italy found an increase incolorectal cancer risk at 1.7 parts per million, or ppm, of nitrate.5 Moreover, studies
conducted in the U.S. found greater incidence of colorectal, ovarian, thyroid, bladderand kidney cancers among people exposed to nitrate from drinking water at levels
half the federal standard and lower.6, 7, 8, 9, 10 According to a 2019 peer-reviewed
study by EWG, there is a one in 100,000 cancer risk associated with a nitrateconcentration of 1.4 mg/L in drinking water.11

NITRATE DRINKING WATER CONCENTRATIONS ABOVE 1
MG/L MAY HARM THE DEVELOPING FETUS
Epidemiological studies report that nitrate ingestion during pregnancy can harm thedevelopment of the fetus. Adverse outcomes associated with nitrate levels below 10mg/L include spontaneous abortion, fetal deaths, prematurity, low birth weight andcongenital malformations.1, 12A 2013 study found associations between prenatal nitrate exposure from drinking
water and neural tube defects such as spina bifida, oral cleft defects and limb
deficiencies.13 In 2017, researchers from the University of Illinois in Chicago reported
that women who consumed drinking water with nitrate concentrations above 1 mg/L
during pregnancy had an elevated risk of very low birth weight and very pretermbirth. These findings were based on birth data for four Midwestern states (Ohio,Indiana, Iowa and Missouri).14
More recently, the same research group analyzed birth data for the state of Missouri
and found that nitrate concentrations above 1 mg/L during pregnancy wereassociated with a significant increase in birth defects including limb deficiencies.15

NITRATE DRINKING WATER CONCENTRATIONS OF 2.5 MG/L
TO 6.5 MG/L MAY HARM THE THYROID
Research by the National Cancer Institute found that women drinking nitratecontaminated water face a greater risk of thyroid cancer.16 These effects wereobserved at nitrate concentrations above 2.5 mg/L.8 A 2012 publication fromthe same research group reported a link between nitrate intake and subclinicalhypothyroidism in women who consumed nitrate at concentrations above 6.5 mg/L.17

UNLIKE DRINKING WATER AND CURED MEAT, NITRATES INSPINACH ARE NOT LINKED TO INCREASED CANCER RISKAccording to the International Agency for Research on Cancer, once ingested, nitrate
is converted into N-nitroso compounds, such as nitrosamines, by bacteria in ourdigestive systems. Nitrosamines damage DNA and cause cancers in the blood and invarious organs, including the stomach, bladder, colon and esophagus.
Cured meats, which are commonly preserved with nitrates, can be a significant
source of dietary nitrate. Like nitrate in drinking water, nitrate in cured meat is also
linked to an increased risk of cancer. Nitrate also occurs naturally in green leafy
vegetables, such as spinach. However, leafy greens have been shown to fight cancer,
likely because of naturally occurring antioxidants that are also present in those foods.

HUMAN HEALTH IMPACTS AND DRINKING WATERTREATMENT ARE COSTLY
The cost of addressing the human health impacts from nitrate-contaminateddrinking water is significant. Nitrate pollution of U.S. drinking water may be
responsible for up to 12,594 cases of cancer a year, which equates to up to $1.5
billion in additional health care costs, according to an EWG peer-reviewed study.11 Of
these, 10,379 cases and $1.3 billion in costs are estimated for colorectal cancer, andthe remaining cases encompass kidney, bladder, ovarian and thyroid cancers.
The cost of treating drinking water to remove nitrate can be large and often falls
disproportionately on residents of small rural towns and cities.18 Hiawatha, Kansas,
for example, began building a new water treatment plant in 2017 after nitratecontamination of drinking water reached 11 mg/L. The plant will cost the town of
about 3,300 an estimated $3.5 million.19 Moreover, the millions of households thatuse water from their own wells for drinking and other household purposes will bear
the entire cost.
Agricultural sources of nitrate are a massive problem. Taking swift and effective
action to require and help farmers to manage their fertilizers and manures – often
the largest source of nitrate drinking water contamination – is necessary to protect
drinking water and public health and to use limited public resources wisely.

REFERENCES
1. Ward MH, Jones RR, Brender JD, de Kok TM, Weyer PJ, Nolan BT, Villanueva CM, van Breda SG. 2018. Drinking
Water Nitrate and Human Health: An Updated Review. Int J Environ Res Public Health. 15(7). pii: E1557. https://doi.
org/10.3390/ijerph15071557
2. U.S. Environmental Protection Agency, Integrated Risk Information System.
National Center for Environmental Assessment, Office of Research and Development (2017). IRIS Assessment Planfor Nitrate and Nitrite [CASRNs 14797-55-8 and 14797-65-0] (EPA/635/R-17/331). Retrieved from: https://yosemite.
epa.gov/sab/sabproduct.nsf/8AF41B299F1C342C852581980075D17D/$File/Nitrate-Nitrite_IAP_draft_plan+9.8.17.pdf
3. U.S. Environmental Protection Agency, Integrated Risk Information System. IRIS Program Outlook (April 2019).
https://www.epa.gov/sites/production/files/2019-04/documents/iris_program_outlook_apr2019.pdf
4. Schullehner J, Hansen B, Thygesen M, Pedersen CB, Sigsgaard T. 2018. Nitrate in drinking water and colorectal
cancer risk: a nationwide population-based cohort study. Int. J. Cancer, 143 (1): 73-79. https://doi.org/10.1002/ijc.31306
5. Espejo-Herrera, N., Gracia-Lavedan, E., Boldo, E., Aragones, N., Perez-Gomez, B., Pollan, M., Molina, A.J.,
Fernandez, T., Martin, V., La Vecchia, C., et al., 2016. Colorectal cancer risk and nitrate exposure through drinking
water and diet. Int. J. Cancer 139, 334–346.
6. De Roos, A.J., Ward, M.H., Lynch, C.F., Cantor, K.P., 2003. Nitrate in public water supplies and the risk of colon andrectum cancers. Epidemiology 14 (6), 640–649.
7. Inoue-Choi, M., Jones, R.R., Anderson, K.E., Cantor, K.P., Cerhan, J.R., Krasner, S., Robien, K., Weyer, P.J., Ward, M.H.,
2015. Nitrate and nitrite ingestion and risk of ovarian cancer among postmenopausal women in Iowa. Int. J. Cancer
137 (1), 173–182.
8. Ward, M.H., Kilfoy, B.A., Weyer, P.J., Anderson, K.E., Folsom, A.R., Cerhan, J.R., 2010. Nitrate intake and the risk ofthyroid cancer and thyroid disease. Epidemiology 21 (3), 389–395.
9. Jones, R.R., Weyer, P.J., DellaValle, C.T., Inoue-Choi, M., Anderson, K.E., Cantor, K.P., Krasner, S., Robien, K.,Freeman, L.E., Silverman, D.T., Ward, M.H., 2016. Nitrate from drinking water and diet and bladder cancer among
postmenopausal women in Iowa. Environ. Health Perspect. 124 (11), 1751–1758.
10. Ward, M.H., Rusiecki, J.A., Lynch, C.F., Cantor, K.P., 2007. Nitrate in public water supplies and the risk of renal cell
carcinoma. Cancer Causes Control 18, 1141–1151.
11. Temkin A, Evans S, Manidis T, Campbell C, Naidenko OV. 2019. Exposure-based assessment and economic
valuation of adverse birth outcomes and cancer risk due to nitrate in United States drinking water. Environ Res.
176:108442. https://doi.org/10.1016/j.envres.2019.04.009
12. J.D. Brender and P.J. Weyer, Agricultural Compounds in Water and Birth Defects. Current Environmental HealthReports, 2016, 3(2):144-152.
13. Brender, J.D., Weyer, P.J., Romitti, P.A., Mohanty, B.P., Shinde, M.U., Vyong, A.M., Sharkey, J.R., Dwivedi, D., Horel,S.A., Kantamneni, J., et al., 2013. The national birth defects prevention study. Prenatal nitrate intake from drinking
water and selected birth defects in offspring of participants in the national birth defects prevention study. Environ.
Health Perspect. 121 (9), 1083–1089.
14. Stayner LT, Almberg K, Jones R, Graber J, Pedersen M, Turyk M. 2017. Atrazine and nitrate in drinking water andthe risk of preterm delivery and low birth weight in four Midwestern states. Environ Res. 152:294-303. https://doi.
org/10.1016/j.envres.2016.10.022
15. Blaisdell J, Turyk ME, Almberg KS, Jones RM, Stayner LT. 2019. Prenatal exposure to nitrate in drinking water andthe risk of congenital anomalies. Environ Res. 176:108553. https://doi.org/10.1016/j.envres.2019.108553
16. Kilfoy BA, Zhang Y, Park Y, Holford TR, Schatzkin A, Hollenbeck A, Ward MH. 2011. Dietary Nitrate and Nitrite andthe Risk of Thyroid Cancer in the NIH-AARP Diet and Health Study. International Journal of Cancer, 129(1):160-172B.
https://doi.org/10.1002/ijc.25650
17. Aschebrook-Kilfoy B, Heltshe SL, Nuckols JR, Sabra MM, Shuldiner AR, Mitchell BD, Airola M, Holford TR, Zhang
Y, Ward MH. 2012. Modeled Nitrate Levels in Well Water Supplies and Prevalence of Abnormal Thyroid Conditions
Among the Old Order Amish in Pennsylvania. Environmental Health 11:6. https://doi.org/10.1186/1476-069X-11-6
18. Schechinger, A. W. and Cox, C. 2018. America’s Nitrate Habit is Costly and Dangerous. Environmental Working
Group. Washington, DC. https://www.ewg.org/research/nitratecost/
19. Hiawatha World, July 11, 2017. City of Hiawatha Issues High Nitrate Warning. Available at www.
hiawathaworldonline.com/news/city-of-hiawatha-issues-high-nitrate-warning/article_71208a3a-b98e-54a4-bc201c4b9bdd7a10.html