Drinking warm tap water during summer heatwaves in France does not pose a risk of contracting Legionnaires' disease, according to physician Dr. Jean-Marc Sene.
Successive heatwaves across France have raised water temperatures in household pipes at a time when residents are frequently filling water bottles to stay hydrated. Speaking on the French television morning program Bonjour ! La Matinale TF1, Sene addressed public concerns regarding tap water safety during hot weather.
Many consumers fear that warm tap water could harbour Legionella bacteria, which causes Legionnaires' disease, a severe pulmonary infection. Sene explained that Legionella bacteria do indeed multiply inside water pipes when temperatures rise slightly. However, he emphasized that Legionnaires' disease cannot be contracted by swallowing water.
Legionnaires' disease transmission
Sene clarified that Legionnaires' disease is contracted exclusively through inhalation rather than ingestion. The medical risk arises when fine water droplets containing the bacteria are breathed into the lungs.
According to Sene, dangerous exposure typically occurs through airborne mist, such as during very hot showers in spas or near outdoor misting devices. Drinking tap water, even when warm, does not create an inhalation hazard.
Legionnaires' disease is a serious lung infection caused by Legionella bacteria, which naturally inhabit water environments and can proliferate in complex plumbing systems when water stagnates at elevated temperatures.
Removing chlorine taste from tap water
Addressing complaints about tap water having an unpleasant chlorinated taste during summer, Sene offered practical advice for households. He recommended letting the initial lukewarm water run from the tap for a short period before filling a glass or bottle.
To avoid wasting water, Sene suggested collecting the initial lukewarm flow and using it to water household plants. Water authorities frequently add chlorine to municipal supplies as a chemical disinfectant to kill pathogens during transit through distribution networks.
Sene noted that placing tap water in a refrigerator for a short time allows chlorine to dissipate, eliminating the taste and providing cool, refreshing drinking water.
Health risks of drinking river water
While tap water remains safe to drink, Sene issued a strong warning against drinking untreated water from rivers and streams while outdoors. He warned that hikers often hold a false sense of security when using portable water filters.
Sene acknowledged that portable filters successfully trap large bacteria, but pointed out that tiny viruses easily pass through filter membranes and can cause serious infections. He added that stagnant natural water presents additional hazards from algae, which produce harmful toxins capable of triggering illness.
Because natural water sources carry unfiltered viral and toxic risks, Sene advised anyone walking or hiking in nature to always carry their own supply of safe drinking water.
