Bromate is a disinfection byproduct with cancer-causing effects.
In this guide, we’ve shared everything you need to know about bromate in drinking water, including how it’s formed, its health effects, how to know if your water contains bromate, and more.
📌 Key Takeaways:
- Bromate is a carcinogenic chemical often found in disinfected drinking water.
- Bromate gets into water when ozone (a chemical disinfectant) reacts with bromide-containing waters.
- The biggest known health effect of ingesting bromate is cancer, caused by DNA damage.
Table of Contents
- ❔ What Is Bromate In Water?
- 🚰 How Does Bromate Get Into Water?
- 〽️ How Much Bromate Does Water Contain?
- 🔎 How To Know If Your Water Contains Bromate
- 🚱 Is Bromate In Drinking Water Dangerous?
- 📉 Is Bromate In Tap Water Regulated?
- 🧪 How To Test For Bromate In Tap Water
- 👩🏽⚕️ What To Do If You’re Concerned About Bromate In Your Water
- ⚠️ Other Ways You Might Be Exposed To Bromate
- 📑 Final Word: Removing Bromate From Water
❔ What Is Bromate In Water?
Bromate is one of the unwanted byproducts of chemical disinfection.
The reason why bromate is unwanted is that it has several known health effects. The most dangerous known health effect of bromate is cancer of various organs.
We’ve shared more about how bromate gets into water, and the effects of high concentrations of bromate measured in tap water, in the below sections.
🚰 How Does Bromate Get Into Water?
Bromate gets into water when it’s treated with ozone, which reacts with bromide, a compound that occurs naturally in many water sources.
The formation of bromate is also likely if drinking water is treated with calcium hypochlorite or sodium hypochlorite solution, although these disinfectants are not commonly used in the public water treatment process.
Here’s the scientific formula for the reaction between ozone and bromide:
Br− + O3 → BrO−3
To understand how and why bromate gets into water, we need to look at the chemical disinfection process.
Most public water systems use chemicals to disinfect their water supplies. Chemical disinfectants are cheap and easy to come by, and they leave residual disinfectant in the water, meaning that the water supply is protected right up until it reaches your home.
Common chemicals used to disinfect drinking water include chlorine, chloramine, chlorine dioxide, and ozone.
Bromate formation occurs when water is treated with ozone (ozonation), which is made from three molecules of oxygen bonded together.
This chemical has proven effective at bonding to bacteria, viruses, and other microorganisms, causing them to break down and preventing them from making us sick. An adequate concentration of ozone must be used to ensure water is protected from pathogens on its journey to our homes.
If the source water supply contains bromide, the likelihood of a reaction between the ozone and bromide is high, and the disinfected water will probably contain bromate.
But where does bromide come from? It’s naturally occurring, and is found in all water sources in concentrations ranging from 10 to 1,000 μg/L (micrograms per liter), so there’s a good chance that it’s in your local water supply.
〽️ How Much Bromate Does Water Contain?
Different water supplies contain different amounts of bromate. There is no exact amount of bromate that all disinfected drinking water supplies contain, and some water supplies might contain no bromate at all.
The amount of bromate detected in your water depends on a number of factors, including:
- The bromide ion concentration of your source water – The higher the water’s bromide levels, the more likely the bromate formation.
- The amount of ozone used to disinfect the water – Equally, the more ozone use to disinfect the drinking water, the higher the likelihood of bromate formation.
- The water pH – The reaction rate between ozone and bromide increases as water pH increases. If the water pH is 8.8 or higher, the reaction rate will level off. A pH of 6.0 or less reduces bromide formation.
- Contact time – The contact time between the ozone and the water supply will also influence bromate formation. The longer the contact time, the more opportunity for bromate to form.
There is a cutoff point for the amount of bromate you can expect to find in your water. There should never be an opportunity for exceedingly high bromate formation because water utilities take steps to reduce organic matter (including bromide) before water is disinfected, and only low levels of disinfectants are added to water – just enough to eliminate the risk of getting sick from drinking pathogens.
However, if you’ve read about the dangers of bromate in drinking water, you probably don’t want to drink even low levels of this contaminant. Plus, many water supplies contain more than 10 PPB of bromate, which exceeds the Maximum Contaminant Level set by the US EPA.
🔎 How To Know If Your Water Contains Bromate
Bromate in water doesn’t have a taste, smell, or color, so you can’t detect this contaminant by simply looking at your water or tasting it from the tap.
The best way to know whether or not your water contains bromate is to check your Water Quality Report or test your water.
Check Your Water Quality Report
Your most recent Water Quality Report (or Consumer Confidence Report) should tell you all the useful information about your drinking water quality, including which disinfection chemical is used to disinfect your water, and the concentration of bromate detected in the treated water at the plant.
Note that a Consumer Confidence Report does have a few limitations. The bromate levels detected at the treatment plant will likely be lower than the bromate concentrations in your water supply at home, since bromate formation will continue as ozone and bromide react in the water traveling in the distribution system to your home.
However, reading this Report will at least give you knowledge about whether or not your water is treated with ozone. If the answer is yes, and the ozone dose is fairly high, your water has a high bromate formation potential.
You can find your Consumer Confidence Report online – just search for your water utility (or your local authority if you’re not sure) followed by “*year Consumer Confidence Report”.
Test Your Water
The most effective way to determine the bromate concentration of your drinking water is to conduct a water test.
Water testing will tell you exactly how much bromate is present in the water leaving your faucets, giving you the data you need to take action against this contaminant if necessary.
We’ve shared a step-by-step process for testing your water for bromate later in this guide.
🚱 Is Bromate In Drinking Water Dangerous?
Bromate in drinking water is dangerous because this chemical has been linked to numerous serious human health effects.
A World Health Organization (WHO) report on the health effects of bromate in drinking water shared the results of several studies on laboratory animals into the potentially cancer-causing effects of bromate.
One of these studies found that bromate exposure significantly increased the formation of tumors of the thyroid gland, and kidney tumors – some of these cancerous, and some not.
Other non-cancer health effects of bromate exposure include:
- Nausea and vomiting
- Abdominal pain
- Central nervous system depression
- Kidney failure
These health risks are unlikely if relatively low, average concentrations of bromate are consumed in disinfected byproducts.
The biggest danger of bromate is its status as a possible human carcinogen.
📉 Is Bromate In Tap Water Regulated?
Yes, bromate in tap water is regulated.
The Environmental Protection Agency (EPA) has developed a Maximum Contaminant Level of 10 PPB (parts per billion) of mg/L (milligrams per liter) of bromate in water. This MCL is based on research into bromates health effects, and ingesting levels of bromate below 10 mg/L is considered safe in the long term.
So, what does that mean? If your water supply contains more than 10 mg/L of bromate, the EPA believes you’re at an increased risk of cancer from long-term exposure to this chemical.
There are a number of ways that water treatment facilities can reduce bromate formation, including:
- Reducing the ozone dose as much as possible
- Lowering water pH to below 6.0
- More thoroughly removing bromide from the source water
- Choosing an alternative water source that has a lower concentration of naturally occurring bromide
- Pre-treating the water with ammonia
Unfortunately, despite this regulation, many public water supplies contain high concentrations of bromate that exceed the EPA MCL for this contaminant.
🧪 How To Test For Bromate In Tap Water
If you’re concerned about bromate contamination and your local water treatment plant uses ozone disinfection, we recommend testing your water for this byproduct.
There are no at-home test kits that are smart enough to detect disinfection byproducts like the bromate ion.
For that reason, you will need to use a more advanced test conducted by your local accredited laboratory.
To test for bromate with a laboratory test, follow these steps:
- Order your preferred test. A typical bromate and bromide water test costs around $150-$200.
- Take a sample of your drinking water. Follow the laboratory’s instructions to take a sample (or samples) of your tap water in the included vial, then send it to the laboratory.
- Wait for your results. You’ll usually receive your test results within 10-14 days.
Your results will give you the exact measurements of bromate detected in your water. The results should make it clear if elevated levels are detected, and offer solutions on how to reduce bromate in your water.
👩🏽⚕️ What To Do If You’re Concerned About Bromate In Your Water
If you’re concerned about bromate in your water, you probably won’t have control over the bromate formation potential at your local water treatment plants.
And the solution isn’t necessarily to lobby for your water utility to stop using ozone, either, since switching to another chemical disinfectant would simply lead to the presence of another cancer-causing disinfection byproduct (of which there are many).
So, the only thing you can do is to reduce your bromate exposure at home.
Here are the steps we recommend taking if you test your water and discover high levels of bromate:
- If you get your water from a municipal supplier, contact the supplier and provide a copy of your test results for them to review. Ask your supplier what steps they are taking to reduce the bromate formation in the water produced for public use.
- Regardless of your water supplier’s response, you might want to take steps to reduce your water’s bromate level at home. You can do this by installing a suitable water treatment system.
- After installing a suitable filter, test the water treated by the system to confirm that the filter has worked and the concentration of bromate is lower.
⚠️ Other Ways You Might Be Exposed To Bromate
Aside from drinking water containing bromate, there is only one other way that you might be exposed to this disinfection byproduct: through eye contact with ozonated water, such as from washing or showering.
Bromate isn’t present anywhere else in the environment, so your risk of exposure to this disinfection byproduct is solely linked to your water supply.
📑 Final Word: Removing Bromate From Water
Your water supplier doesn’t produce bromate deliberately, but if you think they’re not doing enough to reduce bromate formation, you might want to take matters into your own hands.
There are a few different ways to reduce or remove bromate in your water at home, including:
Choose a filtration system that’s capable of reducing at least 80% of bromate in your water, and make sure to buy a product that has plenty of positive customer feedback.