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Chlorine and Chloramine as Water Disinfectants

Water disinfectants are used in America and widely throughout areas of the world to protect us all from waterborne pathogens. Americans don’t face the potentially life-threatening consequences that lower-income nations do without access to safe drinking water. This is largely because disinfectants such as chlorine and chloramine protect us from illnesses that include vomiting, diarrhea, and more.

The downside to our use of disinfectants is the resulting cocktail of disinfection byproducts formed after chlorine, chloramine (or ozone) are added to the water supply. Byproducts form as a result of the interaction between disinfectants (e.g. chlorine) and naturally-occurring materials (e.g. organic matter or humic acids) present in the water and surrounding pipes. The Center for Disease Control (CDC) states that disinfection byproducts may act as human carcinogens (cancer-causing agents).

We’ve covered disinfection byproducts and their risks in a previous article—but we’ve yet to take a more focused look at what separates chlorine and chloramine as disinfectants, and how the type of disinfection byproduct that is formed varies with the use of each.

Let’s take a look together at how these two most common American water disinfectants differ.

Chlorine Water Test SimpleLab

Early 1900s: Transition from Chlorine to Chloramine

Today, chlorine still stands as the disinfectant most often used to treat American water. But there is an alternative: chloramine.

So, what’s the difference, and why the shift from chlorine to chloramine in some areas?

Chloramine is a combination of chlorine and ammonia. Like chlorine, it’s actually been used as a disinfectant since the early 1900s, but it has become increasingly popular. Although chloramine is considered to be a somewhat weaker disinfectant than chlorine, government bodies including the Center for Disease Control  now deem it a safer alternative to treat our water supply than chlorine.

Why is it safer? The Vermont Department of Health notes that chloramine is more stable and easily disperses its benefits throughout water systems, allowing it to act as a longer-lasting solution that inhibits bacterial re-growth when your water is going through the distribution system. Perhaps more importantly, the CDC and Environmental Protection Agency (EPA) report that chloramine produces fewer of the aforementioned disinfection byproducts.

Although the CDC and EPA are on-record stating that chloramine causes fewer disinfection byproducts, it isn’t all as simple as it seems. These government agencies are only referring to a certain type of disinfection byproducts, and in fact, chloramine has its own set of drawbacks, despite now being used to treat tens of millions of American homes.

Chlorine, Chloramine, and Resulting Disinfection Byproducts

Put most simply, water treated by chloramine is going to contain different types of disinfection byproducts than water treated by chlorine, not necessarily fewer disinfection byproducts.

This is because when the CDC and EPA report on disinfection byproducts, they are speaking about regulated disinfection byproducts. When they broadly state chloramine creates “fewer disinfection byproducts” in water, they’re not considering other unregulated disinfection byproducts in their estimations and resulting proclamation.

Specifically, the EPA documents that water treated with chloramine does indeed contain fewer regulated disinfection byproducts that are linked to human health issues, and the ones that are present are often present in lower concentrations than what’s observed in chlorine disinfected water. However, the EPA also notes that in contrast to water disinfected by chlorine, water treated by chloramine is more likely to contain both different and higher concentrations of unregulated disinfection byproducts.

The unregulated byproducts resulting from chloramine disinfection include iodo-trihalomethanes, iodo-acids, and nitrosodimethylamine (NDMA), the latter of which is particularly noted for its toxicity and carcinogenicity.

Unknowns Remain, Research Continues

EPA scientists are currently evaluating chloramine-produced, unregulated disinfection byproducts, but their effects in humans as a result of drinking contaminated drinking water isn’t entirely known.

We also aren’t sure at which concentrations they  prove a legitimate human health risk.

Further muddying the waters, so to speak, is the fact that when chloramine is used as a residual disinfectant, it can alter water’s chemical properties in a way that may lead to lead and copper leaching–the terrible results of which are well documented in Flint, Michigan and other American communities.

Thus, while chloramine is a longer lasting disinfectant that results in fewer of the well-understood, regulated disinfection byproducts, it presents a greater risk when it comes to the disinfection byproducts we don’t yet fully understand and regulate, and also increases the risk of lead and copper exposure in homes with older plumbing.

The Ultimate Takeaway?

Both chlorine and chloramine feature their own unique advantages and disadvantages, and no matter which process is used to treat the water in your local system, disinfection byproducts will remain a very real threat.

It's hard to get trustworthy advice when it comes to your drinking water, so we made Tips for Taps to help answer your questions. Order a Tap Score Water Test and receive personalized support from professional engineers and scientists by phone, email and chat.