Chlorite In Water (What to Know in 2023)

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Chlorite is a disinfection byproduct that’s formed when chlorine dioxide (a chemical disinfectant) reacts with organic matter in the source water and converts to chlorite and chlorate.

Read on to learn everything you need to know about chlorite in drinking water, including how it’s formed, how it might affect your health, and how to find out whether your water contains this contaminant.

๐Ÿ“Œ Key Takeaways:

  • Chlorite is a byproduct of disinfection with chlorine dioxide.
  • This byproduct is formed in drinking water when chlorine dioxide gradually breaks down.
  • Ingesting high levels of chlorite in your tap water could cause your blood’s hemoglobin levels to decrease, leading to dangerous health effects.

โ” What Is Chlorite In Water?

Chlorite is one of the many unwanted byproducts of chemical disinfection.

This particular byproduct is formed when water is disinfected with chlorine dioxide, which is made when sodium chlorate is reduced chemically or electrochemically under acidic conditions.

Chlorite doesn’t affect water quality, but it has several known health effects, including effects on blood chemistry, which is why it’s considered an unwanted contaminant.

We’ve shared more about how chlorite is formed and its potential health risks in the below sections.

Municipal water treatment with chloramine

๐Ÿšฐ How Does Chlorite Get Into Water?

The most common way that chlorite gets into water is through drinking water disinfection.

When water is disinfected with chlorine dioxide, chlorite is produced as a byproduct. The amount of chloride found in the water depends on how much chlorine dioxide is added.

Chlorite is also formed in some manufacturing processes, including when chlorine dioxide is used in food packaging, and when it’s used as a bleaching agent in paper pulp mills and textile facilities. Chlorite could possibly enter water supplies through industrial pollution from these facilities.

๐Ÿงซ How Much Chlorite Does Water Contain?

It’s difficult to give an exact figure of how much chlorite drinking water contains because different water supplies use varying levels of chlorine dioxide for disinfection purposes, and some don’t use chlorine dioxide at all.

A report by the World Health Organization noted that a range of 3.2 to 7.0 mg/L (milligrams per liter) of chlorite was detected in drinking water by one study, but this study is likely now outdated.

It’s highly unlikely that your water supply will contain enough chlorite to cause chlorite poisoning because water utilities only add enough disinfection chemicals to the water to prevent the spread of waterborne disease.

Still, you might not want to drink even trace amounts of this chemical.

chlorite in drinking water

๐Ÿ”Ž How To Know If Your Water Contains Chlorite

Chlorite is an invisible contaminant that doesn’t affect water’s taste, smell, or appearance. So, the only way to know whether or not this byproduct is present in your water is to read your Water Quality Report or conduct a water test.

Read Your Water Quality Report

If you get your water from a municipal supplier, you should receive an annual Water Quality Report (Consumer Confidence Report) that documents all the important information about your drinking water. If you don’t have it on hand, you can also find your most recent Report online.

Your Consumer Confidence Report should mention what type of disinfection chemical is used at the water treatment plant. If chlorine dioxide is listed on your Report, you know that there’s a high likelihood that your water contains chloride.

Most water utilities also list the disinfection byproducts detected in their water supplies, so if chlorite has been detected in the utility’s tests, it should be present in the Report.

Conduct A Water Test

Consumer Confidence Reports are somewhat limited because they don’t account for the increasing levels of chlorite in the water traveling to your home.

The best way to get an accurate reading of the chlorite levels in your faucet is with an at-home water test.

We’ve shared more on how to test your water for chloride later in this guide.

Getting tap water tested with tapscore

๐Ÿšฑ Is Chlorite In Drinking Water Dangerous?

Chlorite in drinking water is considered dangerous because this contaminant has several known human health effects. However, below the maximum concentration allowed by the EPA, low levels of chlorite shouldn’t in theory cause any of these health problems.

The same WHO Report that we mentioned earlier shared findings of some of the studies conducted on the potential health effects of chlorite.

They found that chlorite is rapidly absorbed by the digestive tract and mainly converted to chloride ions, as well as smaller amounts of chlorite and chlorate. Most chlorite is excreted in urine – but the fact that it eventually leaves the body doesn’t make it safe.

Animal studies found that drinking high concentrations of chloride could have the following health effects:

  • Reduced palatability
  • Dehydration
  • Inflammation of the nasal cavity
  • Decreased thyroid hormones
  • Affected sperm function
  • Altered behavior and neurodevelopment

The most well-known potential health effect of chlorite is its ability to affect red blood cells and reduce their ability to carry oxygen, also affecting blood urea nitrogen.

It’s theorized that chlorine dioxide exposure might reduce red blood cell counts and haemoglobin concentrations, but more studies on humans are needed for us to further understand these reports.

๐Ÿ“‰ Is Chlorite In Tap Water Regulated?

Yes, chlorite in tap water is regulated by the Environmental Protection Agency (EPA).

The EPA has set a Maximum Contaminant Level (MCL) of 1,000 PPB (parts per billion) for chlorite in water, based on the knowledge we currently have of the health risks associated with this contaminant.

Under EPA regulations, water treatment plants should minimize their chlorine dioxide use to reduce the production of disinfection by-products, including the chlorite ion.

Since chlorine dioxide and chlorite are intrinsically linked, reducing the amount of chlorine dioxide that’s used to disinfect the water will also reduce the concentration of chlorite produced.

It’s likely that there are other ways that chlorite can be minimized in public water supplies, but chlorite isn’t as heavily researched as other disinfection by-products, so this information isn’t easily available.

Other organizations believe that the EPA’s MCL for this disinfection byproduct is too high. The Environmental Working Group (EWG) proposes a much lower non-enforceable Health Guideline of 50 PPB for chlorite – the level at which it believes this contaminant may pose a significant health risk.

Laboratory water testing

๐Ÿงช How To Test For Chlorite In Tap Water

If you’ve discovered that your water supply contains chlorine dioxide and chlorite, you might want to test your water at home to find out how the chlorite concentrations compare to the information in your Consumer Confidence Report.

Chlorite ions are difficult to detect using a normal at-home water test kit, so you’ll need to upgrade to a more advanced laboratory water test.

Water testing with tap score

There aren’t currently a lot of tests for chlorite, so you might have to shop around to find what you’re looking for.

To test for chlorite with a laboratory test, follow these steps:

  1. Order your preferred test. The cost of a test for chlorite is about $75-$90.
  2. Take a sample of water from your tap. Follow the instructions in the test kit to take a sample (or samples) of your tap water, then seal the package and return it to the laboratory.
  3. Wait for your results to be delivered (typically within 10-14 days).

A good laboratory test will tell you the exact concentration of chlorite in your drinking water. Some lab tests might also tell you the concentration of chlorate ions, since chlorate is often present alongside chlorite as a result of disinfection with chlorine dioxide.

You can use the results to determine whether your water contains elevated levels of this byproduct, and what you can do to reduce chlorite in your water.

๐Ÿ‘ฉ๐Ÿฝโ€โš•๏ธ What To Do If You’re Concerned About Chlorite In Your Water

If you’re concerned about chlorine dioxide and chlorite in your water, there are a few things you can do:

  • If you tested your water for chlorite and discovered high levels of this contaminant, send the lab results to your water utility and ask if they’re doing anything to minimize the chlorine dioxide and chlorite levels in your water.
  • You might want to take matters into your own hands and look at methods of reducing the concentration of chlorite in your water at home.
  • In the meantime, consider switching to bottled water if you’re extremely concerned about the levels of chlorite you might be exposed to in the water from your tap.
  • Also look at how else you might be exposed to chlorite (we’ve shared them below), and how you can reduce this exposure.

Unfortunately, the solution isn’t simply to lobby for your water utility to start using a different disinfection chemical, since all the common disinfectants have their own specific byproducts, many of which have cancer-causing properties.

โš ๏ธ Other Ways You Might Be Exposed To Chlorite

Aside from drinking chlorite in your tap water, there are a few other ways that you might be exposed to this disinfection byproduct at home.

These include:

  • In certain foods – Chlorite may be present in foods that are processed with water treated with chlorine dioxide or foods that have used chlorite as a bleaching agent or in flour processing.
  • In food packaging – You might also ingest chlorite ions in foods that have been contaminated by packaging that uses this byproduct.
  • In farming activities – Certain fungicides and other agricultural products use sodium chlorite, which could increase your risk of inhaling this contaminant.
  • Due to environmental releases – Chlorine dioxide may be released into the environment, contaminating the local atmosphere, soils, or water supplies.

Drinking water remains the most likely cause of chlorite exposure, and communities that drink water treated with chlorine dioxide have a higher exposure to chlorite than other populations.

๐Ÿ“‘ Final Word: Removing Chlorite From Water

Chlorine dioxide and chlorite are closely linked: where one is found, the other is sure to be.

You can reduce chlorite in your water with a few different methods, including:

Getting filtered water from an RO system

Look for a water treatment system that’s sold by a reputable manufacturer and has plenty of positive customer feedback for its contaminant removal abilities.

  • Brian Campbell
    Founder, Water Treatment Specialist

    Brian Campbell is a water treatment specialist and water expert based in Denver, Colorado. He's always been obsessed with water quality, and has spent years testing all kinds of treatment devices from simple pitchers and portable devices to complex whole home systems.

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