A hot spring is a natural emergence of geothermally heated groundwater from the Earth’s crust. The image of this water, often steaming and seemingly pristine, suggests a pure source of hydration. However, the answer to whether this water is safe to drink is a definitive no. The geological forces that create the warmth also introduce unseen biological and chemical contaminants. Untreated hot spring water, while beautiful for bathing, is unsuitable for consumption directly from the source.
Why Untreated Hot Spring Water Is Dangerous
The warm temperatures of hot springs create an ideal breeding ground for thermotolerant microorganisms, posing a biological risk. One infamous example is Naegleria fowleri, the brain-eating amoeba, which thrives in warm fresh water up to 113°F (45°C). While this amoeba typically causes a fatal infection only if forced up the nasal passages, other pathogens are a direct threat through ingestion.
Surface runoff introduces various disease-causing bacteria, including Escherichia coli and Legionella pneumophila, which survive and multiply in the warm environment. Unlike a cold mountain stream, the heat does not sterilize the water against all microbes. Parasites like Giardia may also be present, causing severe gastrointestinal illness.
Beyond biological threats, the water’s deep underground journey causes it to dissolve and concentrate toxic chemicals from the surrounding rock. Geothermal waters often contain contaminants like arsenic, mercury, and radon gas. Arsenic concentration in volcanic areas can be alarmingly high, sometimes reaching levels 10 to 1,000 times greater than the EPA’s drinking water standard.
The distinctive rotten-egg smell of some springs is caused by hydrogen sulfide gas. While toxic when inhaled, the quantities dissolved in the water are usually not a concern for immediate poisoning. These dissolved toxic minerals and gases are a direct byproduct of the geothermal process, making the water chemically unsafe to consume.
Physical Risks and Mineral Overload
The primary physical danger is the high temperature, which can easily cause severe burns. Water temperatures exceeding 120°F (49°C) cause scalding with prolonged exposure, while 140°F (60°C) can cause a serious burn in three seconds. The source water itself is often dangerously hot.
Less apparent is the risk associated with the high concentration of otherwise harmless minerals. Hot springs are naturally high in Total Dissolved Solids (TDS), including sodium, calcium, magnesium, and iron. While the human body requires these elements, the concentration in untreated spring water often exceeds healthy dietary limits.
Consuming water with an excessive mineral load can strain the kidneys, which must work harder to filter out the high levels of salts. Some geothermal brines contain TDS levels up to 4,680 parts per million, far exceeding the typical range for drinking water. This mineral overload can lead to digestive distress and worsen pre-existing health conditions.
Geothermal Water Sources Designated for Consumption
The consumption of geothermal water is not universally prohibited, but safety depends entirely on regulation, testing, and treatment. The exception is regulated products like commercially bottled mineral water, which often originates from a geologically protected underground source. To be labeled “mineral water,” the water must contain a minimum of 250 parts per million of Total Dissolved Solids and cannot have minerals added.
These commercial sources are subject to stringent regulations from bodies like the Food and Drug Administration (FDA), which requires the water to be naturally potable at the source before bottling. Other bottled waters, even if spring-sourced, undergo treatment processes like filtration or reverse osmosis to remove contaminants and ensure safety.
Historical and modern “drinking springs” or spas offer water for public consumption using established infrastructure and continuous monitoring. These facilities test the water frequently for biological and chemical hazards, or they treat the water to meet safety standards. The average person should never drink from an unregulated, wild hot spring, as safety is a function of human intervention and oversight, not its natural state.