Chlorine is a chemical commonly used to treat public water supplies.
Chlorine’s Role in Tap Water
Chlorine is added to public drinking water as a disinfectant. Its main function is to eliminate harmful microorganisms such as bacteria, viruses, and parasites, including Cryptosporidium and Giardia, that can cause waterborne diseases. The use of chlorine for water disinfection dates back over a century and has been highly effective in preventing outbreaks of illnesses.
This chemical acts by oxidizing the cellular components of these pathogens, rendering them inactive and incapable of causing illness. Regulatory bodies, such as the Environmental Protection Agency (EPA) in the United States, set specific limits on the amount of chlorine allowed in tap water to ensure its safety and effectiveness. Chlorine also helps maintain water quality as it travels through the distribution system to consumers’ taps.
Safety of Regulated Tap Water
Public health organizations generally consider tap water treated with regulated levels of chlorine safe for drinking. The benefits of disinfecting water to prevent widespread disease outbreaks significantly outweigh the potential minor risks associated with the low concentrations of chlorine present. For most individuals, consuming chlorinated tap water at these normal, regulated levels does not pose a health concern.
Chlorine levels up to 4 milligrams per liter (mg/L), or 4 parts per million (ppm), are considered safe in drinking water. The World Health Organization (WHO) also established a guideline value of 5 mg/L for chlorine in drinking water, considering it acceptable for lifelong consumption. Some common concerns, such as a noticeable taste or odor, are typically aesthetic and not indicative of a health hazard. While some people may have sensitivities to chlorine, serious health risks are generally not associated with regulated tap water.
When Chlorine Water Becomes Dangerous
Drinking water with high concentrations of chlorine can pose serious health risks. Unlike regulated tap water, other sources contain chlorine at levels not intended for consumption. For example, ingesting water from swimming pools or hot tubs is dangerous because these sources contain significantly higher concentrations of chlorine and other chemicals designed for sanitation, not potability. Consuming pool water can lead to irritation, gastrointestinal distress, or more severe effects depending on the amount ingested.
Household bleach, which is a concentrated solution of sodium hypochlorite, is extremely toxic if consumed. Ingesting even small amounts can cause irritation of the mouth, throat, and gastrointestinal tract, leading to nausea, vomiting, and abdominal pain. Consumption of concentrated bleach products can result in permanent internal damage, severe poisoning, and can be fatal, requiring immediate medical attention. Water from industrial processes that contains high levels of chlorine is also unsafe to drink and can cause severe adverse health effects.
Reducing Chlorine in Tap Water
For individuals who wish to reduce or remove chlorine from their tap water, several practical methods are available. Activated carbon filters are highly effective, working through a process called adsorption where chlorine molecules are trapped by the carbon media as water passes through. These filters are commonly found in pitcher filters, faucet attachments, and whole-house filtration systems, significantly improving taste and odor.
Boiling water for about 15 minutes can also help dissipate chlorine, as chlorine is volatile and evaporates at higher temperatures. This method is more effective for chlorine than for chloramines, which are more stable. Another simple approach involves letting tap water stand uncovered for a few hours; chlorine gas will naturally evaporate into the air over time, though this process is slower and less effective for chloramines. Additionally, vitamin C (ascorbic acid or sodium ascorbate) can chemically neutralize chlorine, often used for larger volumes of water like bathwater or in aquariums, but less commonly for drinking water.