Does Boiling Water More Than Once Cause Cancer?

Question: Does Boiling Water More Than Once Cause Cancer?

I've heard from many aunts and uncles and other older relatives that you should not re-boil your drinking water once it's already been boiled. I've been told that it's extremely bad and may cause cancer. Is this true? And if so, why? I have yet to find a medical article stating that you should not re-boil water to drink or use in cooking.

Ellen - About.com User

Answer: Re-boiling clean uncontaminated drinking will water not cause cancer or any other health problems. However, boiling water contaminated with chemicals such as nitrates or toxic elements such as arsenic is a bad idea, so there may be circumstances when re-boiling water is a problem, but only if your water is bad to begin with, and it would only occur in a few rural areas where water quality isn't monitored.

Ground water may contain nitrates, which are chemicals often found in fertilizer, and arsenic that may occur naturally or from farm or industrial waste. Nitrates, along with nitrites, are also found in processed meats.

Consuming water contaminated with nitrates can cause a blood disorder called methemoglobinemia and some research shows that nitrates in drinking water may be associated with some types of cancer. Exposure to arsenic may result in arsenic poisoning and increased risks of several types of cancer.

Nitrates and arsenic are not like bacteria, so boiling your water doesn't remove them. In fact, boiling water will actually increase the concentration. The more the water is boiled, the higher the concentration of these substances will be.

The levels of both nitrates and arsenic are regulated and water supplies must be monitored in towns and cities, so if your tap water comes from a city water source, it is safe. People who live in rural areas and have private wells must have their well water tested for nitrates and arsenic. If you have a private well and the levels of these contaminants are too high, you must install a water filtration system for your home.

_Sources:

_{Centers for Disease Control. "Nitrate and Drinking Water From Private Wells." Accessed May 12, 2009. http://www.cdc.gov/ncidod/dpd/healthywater/factsheets/nitrate.htm.}

_{Centers for Disease Control. "Arsenic and Drinking Water." Accessed May 12, 2009http://www.cdc.gov/ncidod/dpd/healthywater/factsheets/arsenic.htm."}

_{Chiu HF, Tsai SS, Yang CY. "Nitrate in drinking water and risk of death from bladder cancer: an ecological case-control study in Taiwan." J Toxicol Environ Health A. 2007 Jun;70(12):1000-4.}

_{De Roos AJ, Ward MH, Lynch CF, Cantor KP. "Nitrate in public water supplies and the risk of colon and rectum cancers." Epidemiology. 2003 Nov;14(6):640-9.}

_{United States Environmental Protection Agency. "Consumer Factsheet on: Nitrates/Nitrites." Accessed May 12, 2009. http://www.epa.gov/safewater/contaminants/dw_contamfs/nitrates.html.}

_{Ward MH, Cross AJ, Divan H, Kulldorff M, Nowell-Kadlubar S, Kadlubar FF, Sinha R. "Processed meat intake, CYP2A6 activity and risk of colorectal adenoma." Carcinogenesis. 2007 Jun;28(6):1210-6.}

_{World Health Organization. "Arsenic in Drinking Water. "Accessed May 12, 2009. http://www.who.int/water_sanitation_health/dwq/arsenic/en/."}

_{Yang CY, Cheng MF, Tsai SS, Hsieh YL. "Calcium, magnesium, and nitrate in drinking water and gastric cancer mortality." Jpn J Cancer Res. 1998 Feb;89(2):124-30.}