According to a recent study, a lifetime of drinking tap water could put you at risk for cancer. The non-profit Environmental Working Group (EWG) recently conducted a study and issued this finding. Specifically, the study predicts 100,000 new cancer cases could occur among people who drink tap water throughout their life.¹ The study looked at the cumulative effect of more than one pollutant such as arsenic and radioactive contaminants. “Contaminants” are things that contaminate, meaning substances that make water unfit for use because of unwanted elements, such as sewage.² These pose the greatest risk for people who live in rural or dry areas.

Clear Water is Not Always Clean

Just because water is clear doesn’t mean it’s safe. In fact, arsenic is a contaminant with no simple “trace.” In other words, you can’t taste it, see it, or smell it.³ In addition to arsenic, the EWG also looked into two types of natural compounds in water: radioactive contaminants and disinfection byproducts. These pollutants include trihalomethanes which form when chlorine reacts with natural organic and inorganic matter. For example, adding common household bleach to water containing decaying plants and algae can produce trihalomethanes.⁴  

In a study published in the journal Heylion, EWG researchers argue that prolonged exposure to multiple contaminants in water increases the chances of becoming ill. EWG researchers examined 22 known, cancer-causing chemicals in United States drinking water. These were detected in the years 2010 to 2017.

Researchers predict that nearly 100,000 cancer cases could result from drinking contaminated water for a lifetime. By comparison, this number represents only a fraction of the total number of cancer cases estimated by the American Cancer Society in 2018, roughly 1.7 million.⁵

However, EWG’s vice president of science investigations, Olga Naidenko explained that water contamination is linked to a higher rate of cancer cases arising from environmental causes, i.e. a person’s surroundings.⁶ Of the 100,000 cancer cases, around 45,000 were linked to disinfection byproducts and 45,000 to arsenic. The remaining 4,500 cases were linked to radioactive contaminants, such as radium and uranium. You can read more about uranium in water here.

The Source of the Problem

Globally, the United States ranks high on water quality standards. For instance, biological contaminants such as the bacterium E. coli are no longer a concern for most communities.⁷ However, cancer-causing contamination continues to be a problem in rural and dry areas.

For example, the EWG study noted that rural communities that receive their water supply from groundwater systems are problem areas due to poor infrastructure and lack of funding.

In addition, the study identified public water systems supplied by surface water in dry areas as being at greater risk of contaminants compared to groundwater sources.⁸ Without enough water to dilute potential contaminants such as cleaning products, they begin to build up in surface water. 

During a drought, pumping groundwater is often necessary in these areas. But local water authorities in dry places such as California’s Central Valley have not found a link between multiple contaminants and the risk of cancer.⁹ For this reason, the study focused on chemicals that are not only monitored but also considered safe at present levels.

Reducing the Cancer Risk: Three Things You Can Do Now

According to the United States Environmental Protection Agency, most public water systems meet public health standards.¹⁰ However, this conclusion is based on evaluations of a single chemical per assessment. In real world conditions, however, a mix of chemicals in a supply is more likely the case.

To protect yourself, you must look for information on local water supplies and possible alternatives, if necessary. Here are three ways you can stay safe: 

1. Keep up to date on local supplies of water.
2. Buy a filter that can eliminate problem chemicals.
3. Consider buying bottled water for a short time in areas with a known risk.

While the EWG does not discourage people from relying on their tap water, communities should stay informed and safe. 

References

1. Evans, Sydney, Chris Campbell, and Olga V. Naidenko. 2019. “Cumulative Risk Analysis of Carcinogenic Contaminants in United States Drinking Water.” Heliyon 5 (9). https://doi.org/10.1016/j.heliyon.2019.e02314.
2. Contaminate. (n.d.) In Merriam-Webster’s online dictionary. Retrieved from https://www.merriam-webster.com/dictionary/contaminate
3. Gamboa-Loira, Brenda, Mariano E. Cebrián, Francisco Franco-Marina, and Lizbeth López-Carrillo. 2017. “Arsenic Metabolism and Cancer Risk: A Meta-Analysis.” Environmental Research 156 (April): 551–58. https://doi.org/10.1016/j.envres.2017.04.016.
4. New Hampshire Department of Environmental Services. 2006. “Trihalomethanes: Health Information Summary.” Environmental Fact Sheet. https://www.des.nh.gov/organization/commissioner/pip/factsheets/ard/documents/ard-ehp-13.pdf
5. American Cancer Society. 2018. “Cancer Facts & Figures 2018.” Atlanta. https://www.cancer.org/content/dam/cancer-org/research/cancer-facts-and-statistics/annual-cancer-facts-and-figures/2018/cancer-facts-and-figures-2018.pdf.
6. Holden, Emily. 2019. “Tap Water Contaminants Linked with 100,000 Cancer Cases, US Study Finds.” The Guardian, 2019. https://www.theguardian.com/environment/2019/sep/19/tap-water-contaminants-linked-with-cancer-cases-study.
7. Roberson, J. Alan. 2019. “Drinking Water: If We Don’t Learn From History, We Are Bound to Repeat It.” Journal – American Water Works Association 111 (3): 18–24. https://doi.org/10.1002/awwa.1249.
8. Kalankesh, Laleh R., Mohammad Ali Zazouli, Heru Susanto, and Esmaeil Babanezhad. 2019. “Variability of TOC and DBPs (THMs and HAA5) in Drinking Water Sources and Distribution System in Drought Season: The North Iran Case Study.” Environmental Technology (United Kingdom). https://doi.org/10.1080/09593330.2019.1621952.
9. Stoiber, Tasha, Alexis Temkin, David Andrews, Chris Campbell, and Olga V. Naidenko. 2019. “Applying a Cumulative Risk Framework to Drinking Water Assessment: A Commentary.” Environmental Health 18 (1): 37. https://doi.org/10.1186/s12940-019-0475-5.
10. United States Environmental Protection Agency, 2019. Enforcement and Compliance History Online. National Drinking Water Activity Dashboard. https://echo.epa.gov/trends/comparative-maps-dashboards/drinking-water-dashboard.

New Findings 

A “first of its kind” study published in June 2019 by the U.S. based non-profit, Environmental Working Group, has analyzed nitrate exposure from drinking water across the United States between 2010 and 2017.1 The study, which was published in the journal Environmental Research, found that over 12,000 annual cases of cancer may be directly caused by exposure to nitrate pollution.2

What is Nitrate Pollution?

While nitrogen is an essential nutrient needed for plant growth, the overabundance of its forms in nitrite, nitrate and ammonium can be found in drinking water sources because of inadequate farming practices and urban wastewater management. 

“Nitrate sources are effectively everywhere – agricultural lands, natural lands, urban areas with leaky sewer lines, septic leach fields, and wastewater percolation basins,” says the University of California- Davis’ report “Addressing Nitrate in California’s Drinking Water.”3 Although these nitrate sources are effectively everywhere, some of the largest causes of nitrate contamination in lakes and streams are manure fertilizer and sewage.4 For example, nitrate can get into water directly as the result of runoff of fertilizers containing nitrate.5  Unsecured manure storage can also result in leaching of excess nitrates into the soil. 

The current US federal standard for nitrate levels is 10 parts per million, or 10 mg/L.6 In more household-friendly terms, 10 mg/L amounts to a little over 7 teaspoons per gallon. Recently, the medical evidence linking nitrate in drinking water with human illness has raised more questions about whether the nitrate limit of 10 mg/L protects the general population against harmful side effects.2

The Dangers of Excess Nitrate in Drinking Water

Some of the health effects of nitrate consumption have been known for a while. One of the most common groundwater contaminants in rural areas, nitrate is regulated in drinking water primarily because excess levels can cause methemoglobinemia, or “blue baby” disease, which is low oxygen levels in the blood causing suffocation. 7 

Formula-fed babies are at a higher risk for the disease as they consume more water in comparison to their body weight than adults do. Formula powder and juices mixed in tap water strain their undeveloped digestive system, which leads to more reduction of nitrate to nitrite.7

In adults, long-term exposure to high nitrate levels in drinking water is also associated with thyroid dysfunction and cancer. Areas that depend on groundwater—those that get their water from wells, for example—can sometimes exceed the national maximum nitrate in drinking water (45 mg nitrate per liter or, equivalently, 10 mg of nitrate-measured-as-nitrogen per liter).”2

It was previously thought that the old standards for nitrate levels in water were safe. But a newly published study published by the Environmental Working Group concluded that nitrate contamination in drinking water across the US could cause up to 12,594 cases of cancer per year.1 The highest percentage of cases related to colorectal cancer, but it also included ovarian, thyroid, kidney and bladder cancer. The researchers also estimated the economic costs of these medical conditions: “For medical expenditures alone, this burden of cancer corresponds to an annual economic cost of 250 million to 1.5 billion U.S. dollars, together with a potential 1.3 to 6.5 billion-dollar impact due to lost productivity.”2

Ways to Reduce Risk of Cancer

In general, the greater the uncertainty about potential health effects, the greater the margin of safety built into the government regulation.7 Hence the federal Safe Drinking Water Act passed in 1974, which set the standard of 10 mg/L nitrate as nitrogen as a maximum.  

Given the new information about potential cancer risks, these standards may no longer be adequate. Recent large-scale epidemiological studies conducted in European countries reported statistically significant increases in colorectal cancer risk associated with nitrate in drinking water at levels of 0.7–2 mg/L.2 Outdated standards of safe drinking water need to reevaluated. 

Beyond getting involved and lobbying for new standards for nitrate levels in water, there are several things you can do at home to safeguard yourself from nitrate contamination:

• Breastfeed for as long as possible or use bottled or distilled water to mix formula.7
• Get your water tested at your regional health departments and laboratories by sending in samples. Check further for other contaminants. 
• If you have one, maintain your septic leach field so that contaminants can be drained effectively.3 More information about leach fields can be found here on the EPA’s website. 

References 

1. Sarah Graddy. June 11, 2019. “EWG: Nitrate Pollution of U.S. Tap Water Could Cause 12,500 Cancer Cases Each Year.” Environmental Working Group. (https://www.ewg.org/release/ewg-nitrate-pollution-us-tap-water-could-cause-12500-cancer-cases-each-year)
2. Alexis Temkin, et. al. June 11, 2019. “Exposure-based assessment and economic valuation of adverse birth outcomes and cancer risk due to nitrate in United States drinking water.” Environmental Research. (https://www.sciencedirect.com/science/article/pii/S001393511930218X) 
3. Thomas Harter and Jay R. Lund. March 2012. “Addressing Nitrate in California’s Drinking Water”. University of California – Davis. (http://groundwaternitrate.ucdavis.edu/)
4. Wu J, et. al. July 2019. “Severe Nitrate Pollution and Health Risks of Coastal Aquifer Simultaneously Influenced by Saltwater Intrusion and Intensive Anthropogenic Activities.” Archives of Environmental Contamination and Toxicology. 77(1):79-87. (https://www.ncbi.nlm.nih.gov/pubmed/31053873)
5. Water Science School. “Nitrogen and Water”. United States Geological Survey. (https://on.doi.gov/2Ieci6i)  
6. Brian Pascus. June 11, 2019. “Study: Nitrate pollution in U.S. drinking water could lead to thousands of cancer cases”. CBS News. (https://cbsn.ws/2RNDivJ ) 
7. Margaret McCasland, et. al. 2012. “Nitrate: Health Effects in Drinking Water”. Cornell University. (http://psep.cce.cornell.edu/facts-slides-self/facts/nit-heef-grw85.aspx)