Chlorine is a chemical disinfectant used globally to ensure drinking water is safe from harmful microorganisms. For bottled water, the presence of chlorine depends on the water’s source and the processing methods used. While bottlers often use treatments designed to remove chlorine, trace amounts or related chemical byproducts can still be present. The final concentration, if any, is typically far lower than what is found in municipal tap water.
How Bottled Water is Regulated
Bottled water in the United States is regulated by the Food and Drug Administration (FDA) as a packaged food product. This contrasts with municipal tap water, which is regulated by the Environmental Protection Agency (EPA) under the Safe Drinking Water Act. Federal law mandates that the FDA’s standards for bottled water must be at least as stringent as the EPA’s standards for public drinking water systems.
The FDA establishes quality standards for bottled water, including maximum allowable levels for disinfectants like chlorine and their byproducts. The maximum residual disinfectant level (MRDL) for chlorine is set at 4.0 milligrams per liter (mg/L), aligning with the EPA’s limit for tap water. Bottlers must monitor their finished product for residual disinfectants and disinfection byproducts (DBPs), such as total trihalomethanes (TTHM), at least once a year. This framework ensures that any chlorine or its remnants present are within legally safe limits that mirror the standards applied to the public water supply.
Pathways for Chlorine Presence
Chlorine, or its chemical remnants, can enter bottled water through two main routes related to the source and the bottling process. The first pathway is residual chlorine if the source water is taken from a municipal supply. Many bottlers use treated city water as their starting point; although it is subsequently purified, faint traces of the original chlorine or its stable byproducts may remain before final processing.
The second pathway involves the intentional use of chlorine-based chemicals as a disinfectant during manufacturing. Although less common than alternatives like ozonation, some bottlers use chlorine or chlorine dioxide to ensure the water is free of pathogens before sealing. If used, this added chlorine is typically removed, but a small residual amount may remain to maintain sanitary conditions during bottling and storage. Chlorine use can lead to the formation of Disinfection Byproducts (DBPs) when it reacts with organic matter in the water.
Differences in Water Types and Purification
The likelihood of finding chlorine is influenced by the type of bottled water and the purification methods employed. Purified Water often begins as municipal tap water and undergoes intensive treatment designed to strip away impurities, including chlorine. Processes like reverse osmosis, distillation, and activated carbon filtration are highly effective at removing chlorine and other chemical contaminants. Reverse osmosis systems can remove up to 98% of chlorine, while activated carbon filters work by adsorption to remove chlorine molecules, improving taste and odor.
Conversely, Spring Water or Mineral Water must meet specific FDA definitions related to their underground source and mineral content, and they undergo minimal processing. These types of water are less likely to have chlorine added, as they are often disinfected using non-chemical methods like ozonation or ultraviolet (UV) light. Ozonation is a preferred method because the ozone gas disinfects effectively without leaving a chemical taste or a long-lasting residual.
Understanding Chlorine Safety
The presence of residual chlorine, even in trace amounts, is considered safe and is a historical public health measure against waterborne disease. The maximum level allowed in both tap and bottled water is 4.0 mg/L, a concentration deemed safe for consumption by public health agencies. The primary concern related to chlorine is not the chlorine itself, but the formation of Disinfection Byproducts (DBPs), such as trihalomethanes (TTHMs), which occur when chlorine reacts with organic compounds in the source water.
The FDA, mirroring EPA regulations, sets strict limits on these DBPs to mitigate potential long-term health risks. Because bottled water is treated aggressively or sourced from protected supplies, it contains significantly lower levels of chlorine and DBPs compared to tap water. Purification processes are effective at reducing these byproducts to levels far below the regulatory thresholds, ensuring the final product is safe for drinking.