Howard Fischer
Uppsala, Sweden

“Water, water everywhere/Nor any drop to drink.”
– The Rime of the Ancient Mariner, Samuel Taylor Coleridge (1772–1834)

In the year 2020, 4.5 billion people flew on commercial aircraft. The previous year saw US airlines carry over 900 million passengers, and only 13% of Americans had never flown on a plane.¹

Water is used on aircraft. It may be drunk from cold water taps, used in the preparation of hot beverages like coffee or tea, in the reconstitution of dried food or infant formula, for tooth brushing in the plane’s lavatory, for handwashing in the lavatory or galley, for face washing, for cleaning utensils, and for preparing moist, hot towels for hand and face washing. For potable water to reach a plane’s storage tanks, it must come from an outside source of potable water, either in the US or abroad. It is then transported to the airport, transferred to the aircraft in airport water service vehicles, and finally arrives in the aircraft’s water system.² In some of these steps there is a risk of bacterial contamination of the plane’s drinking water.³

In this brief article we consider only the testing of airplane drinking water for bacterial contamination and not for other qualities, such as pH, chlorine content, chemicals, color, or odor. Because of the short duration of exposure of aircraft passengers to the plane’s drinking water, the most significant risk is exposure to microbes.⁴

There is an eventful history of examining the drinking water of aircraft for bacterial contamination. Taking the summer of 2004 as our starting point, we learn that the Environmental Protection Agency (EPA) tested the water quality in 158 aircraft in seven airports. Twenty aircraft (12.6%) had coliform bacteria in their drinking water. Coliforms are not usually harmful but they indicate “inadequate sanitation practices.” Two aircraft (1.3%) had potentially dangerous E. coli bacteria in their drinking water. Testing was expanded (169 planes at twenty airports) and repeated three months later. Coliforms were found in the drinking water of 17% of the planes.^5,6 The EPA advised passengers with immunologic compromise or other health concerns to avoid drinking water on aircraft in 2004.⁷ Health Canada made the same recommendations in 2006 after studies indicated that water became contaminated after passing through the airport water service vehicles.⁸

In 2011, the US government implemented the Aircraft Drinking Water Rule (ADWR). It charged the EPA, the Federal Aviation Administration, and the Food and Drug Administration with verifying the safety of drinking water on planes.⁹ Airlines are required to take samples from their water tanks to test for the presence of coliforms and E. coli bacteria. They are also required to disinfect and flush the water tanks four times a year.

In reality, the EPA rarely fines airlines for violations of the ADWR. A 2019 study¹⁰ tested airplane drinking water using a “water health scale,” on which zero is the lowest score and five the best possible. Scores of three or above were considered acceptable. Only three of eleven major US airlines and one of twelve regional US airlines passed. This, surprisingly, is an improvement compared to the time before passage of ADWR.

Airlines are required to notify passengers and crew if a water system is found to be contaminated.¹¹ Most cabin personnel on aircraft do not drink hot drinks or use ice cubes made on airplanes because of the frequent contamination of the water. Heating the water will kill many, but not all, pathogens.¹² Water on “long-haul” flights is generally more contaminated than water on “short-haul” flights.¹³

Ice produced on aircraft has not been tested for bacterial contamination, but ice from restaurants and commercial ice providers has. Nearly all had bacterial contamination, most with Pseudomonas species. The addition of whiskey was a more effective bactericidal technique than the addition of vodka.¹⁴ It is reasonable to conclude that contaminated potable water on aircraft will produce contaminated ice.

The recommendations of the author of the 2019 study¹⁵ apply to all aircraft passengers: do not drink water onboard if it does not come from a sealed bottle; do not drink coffee or tea onboard; wash hands with hand sanitizer, not water.

References

1. Allan Jay. “Number of flights worldwide in 2022/2023: Passenger traffic, behavior, and revenue.” FinancesOnline, September 19, 2023. https://financesonline.com/number-of-flights-worldwide/.
2. World Health Organization. Guide to Hygiene and Sanitation in Aviation 3^rd Ed, Geneva, 2009.
3. Harald Handschuh et al. “Bacteria that travel: The quality of aircraft water.” Int J Enviorn Res Public Health, 12(11), 2015.
4. World Health Organization, Guide to Hygiene and Sanitation.
5. Annelies Heidekamp and Ann Lemley. “Water quality in airplanes.” Cornell University Water Bulletin, January 2005. https://www.nycfoodpolicy.org/wp-content/uploads/2019/08/CCEWQ-70-WaterQualityAirplanes.pdf.
6. Handschuh et al, “Bacteria.”
7. Tracy Hampton. “Airline drinking water tainted.” JAMA, 293(8), 2005.
8. Handschuh et al, “Bacteria.”
9. Charles Platkin. “Background airline drinking water rule and other helpful information.” Center for Food as Medicine. https://foodmedcenter.org/background-airline-drinking-water-rule-and-other-helpful-information/.
10. Charles Platkin. “2019 airline water study by CUNY’s Hunter College NYC Food Policy Center.” Eureka Alert, August 29, 2019.
11. Charles Platkin, “Background airline drinking water rule.”
12. James Felton. “Flight attendant explains why you should never drink hot drinks on a plane.” IFLScience, February 5, 2021. https://www.iflscience.com/flight-attendant-explains-why-you-should-never-drink-hot-drinks-on-a-plane-58653.
13. Madeline Diamond. “Why you should never order ice on a plane.” Insider, December 27, 2017. https://www.businessinsider.com/should-i-drink-ice-on-plane-2017-12.
14. Luca Settani et al. “Presence of pathogenic bacteria in ice cubes and evaluation of their survival in different systems,” Ann Microbiol, 67, 2017.
15. Platkin, “2019 airline water study.”