Are Water Purifying Tablets Safe (Idoine, Chlorine, Chlorine Dioxide)?

I was buying some water purifying tablets for an upcoming hike the other day and started wondering — are they actually safe? What chemicals are in these tablets, and how much can I actually consume? I quickly did some research.

Are water purifying tablets safe? Water purifying tablets typically contain iodine, chlorine or chlorine dioxide. Taking into account the average water consumption for an average adult, these tablets are safe for people with no underlying medical conditions.

However, water purifying tablets may not be suitable for people who are pregnant or have medical conditions such as thyroid conditions or allergies.

It is also critical to note that water purifying tablets may also not be the most effective water purification method as it is not fully effective at killing viruses.

How Do They Work?

The active ingredient in water purification tablets is typically chlorine, chlorine dioxide or iodine. water purification tablets typically contain various forms of chemicals that dissolve in water to release these ingredients. When dissolved, these chemicals are released to kill bacteria, viruses, and parasitic protozoa. They do so by destroying the cell membrane of these microorganisms, allowing the chemical to enter and deactivate them.

How Safe Are These Chemicals?

Chlorine

Don’t worry, this is not the same form of chlorine used to disinfect swimming pools. Chlorine is a widely used water disinfectant and most tap water which are deemed safe to drink is most likely to have been treated by chlorine.

Chlorine Dioxide

Chlorine dioxide can be seen as an improved version of chlorine. Chlorine 2.0 if you like. For the same amount, chlorine dioxide can disinfect a larger quantity of water as compared to chlorine. It is also able to work over a wider range of pH levels.

Iodine

Iodine is a nutrient that your body needs (this is why you have iodized salt). However, too much iodine is bad for your body as it oxidizes proteins. But you are unlikely to overdose on iodine from water purifying tablets.

A typical concentration used for purifying drinking water is about 3 mg/liter. According to CDC, the lethal dose of iodine is about 2-3g of consumption. This means you would need to drink 1,000 liters (264 gallons) of water. Not forgetting that your body is also able to breakdown to remove iodine naturally, it is near impossible to reach anywhere near the lethal dose.

However, iodine may cause health risks for:

• Women who are pregnant: excessive iodine may affect maternal thyroid health
• People with thyroid conditions: depending on whether the person has hyperthyroidism or hypothyroidism, iodine may cause the thyroid to produce too much or too little hormones
• People with iodine allergies

Some common side effects may include nausea or headaches.

But it is interesting to note that using iodine as a water purifier is banned in the EU. Though iodine is still sold for other purposes (like in salt), it is not packaged for water purification purposes.

Effectiveness Of Water Purifying Tablets Against Bateria and Viruses

The most common source of contamination in water in the wilderness is bacteria, viruses or protozoa from human and animal fecal waste. Some of these can cause disease, illness or death. Cryptosporidium and Giardia are among the most common harmful microorganisms encountered during wilderness activities.

1. Bacteria (for example, Campylobacter, Salmonella, Shigella, E. coli)
   • Potential health effects from drinking water contaminated with bacteria are gastrointestinal illness such as diarrhea, vomiting, and cramps
   • Sources of bacteria in drinking water are human and animal fecal waste

1. Viruses (for example, Enterovirus, Hepatitis A, Norovirus, Rotavirus)
   • Potential health effects from drinking water contaminated with bacteria are gastrointestinal illness such as diarrhea, vomiting, and cramps
   • Sources of bacteria in drinking water are human and animal fecal waste
2. Cryptosporidium
   • Potential health effects from drinking water contaminated with bacteria are gastrointestinal illness such as diarrhea, vomiting, and cramps
   • Sources of bacteria in drinking water are human and animal fecal waste
3. Giardia
   • Potential health effects from drinking water contaminated with bacteria are gastrointestinal illness such as diarrhea, vomiting, and cramps
   • Sources of bacteria in drinking water are human and animal fecal waste

It is important to note that water purification tablets do not remove sediments or chemical pollutants. Filter any sediments out of the water before adding the tablets.

How To Use The Water Purifying Tablets?

The typical procedure for using water purifying tablets:

1. Filter any sediment out of the water with a paper filter or a thin cloth.
2. Add chlorine tab(s) into the water (make sure you use the correct number of tablets required for the quantity of water you are purifying).
3. Wait about 30 minutes to completely kill off contamination (check the waiting time on the packaging, it might be longer in some temperatures and conditions, and it is usually longer for iodine tablets).
4. Add flavoring or neutralizers to remove the taste of the chlorine or iodine from the water if you like.  The chlorine taste can also be removed by allowing the treated water to sit uncovered so the chlorine can evaporate.

All water purifying tablets will not be completely effective if they are not used properly. Check the usage instructions on the packaging and follow them precisely to ensure effectiveness.

What Happens If You Accidentally Ingest Water Purification Tablets?

You should not consume the tablets without first dissolving them in water. If any tablets are eaten or swallowed, seek medical advice immediately. Check if there are any instructions on the packaging on accidental ingestion.

What Are Some Well-known Brands Of Water Purifying Tablets?

These are some of the common water purifying tablets used by climbers and hikers:

• Aquatabs (chlorine tablets)
• Katadyn  (chlorine dioxide tablets)
• Potable Aqua (chlorine dioxide and iodine tablets)

How Much Do Water Purification Tablets Cost?

Water purification tablets are usually the most affordable form of disinfecting water. Some examples of their costs:

• Aquatabs (chlorine tablets): about USD 8 for 100 tablets
• Katadyn  (chlorine dioxide tablets): about USD 12 for 20 tablet
• Potable aqua (chlorine dioxide tablets): about USD 12 for 20 tablets
• Potable aqua (iodine tablets): about USD $10 for 50 tablets (comes with taste neutralizing tablets)

How Long Can The Water Purifying Tablets Last?

If stored properly, water purifying tablets can last for years.

Factors such as sunlight, high temperature or moisture may cause the degradation process to speed up, so your tablets are usually packaged in foil or dark bottles. Store them in dark, cool and dry places.

The effectiveness of the water purifying tablets might be affected by its expiry date. Do not use any tablets beyond their expiry as their effectiveness might be reduced. You do not want to take your chances on this.

Where To Collect Drinking Water?

Don’t just rely on the water purifying tablets. Avoid collecting from water sources near these areas as the risks to your health can increase significantly:

• Factories dealing with chemical pollutants, metals or other man-made waste
• Poultry farms
• Stagnant pools of water

Generally, water collected from natural sources in the wilderness is safe for drinking and actually does not require further purification and disinfection. In the US for example, a survey of 69 backcountry sites showed that the concentrations of Giardia cysts found in every site were much too low to make anyone sick.

Related Questions

What are some other methods of purifying and disinfecting water? Besides water purifying tablets, there are various other forms of purifying and disinfecting water. Each has pros and cons in terms of taste, effectivness, convenience, and costs.

• Bleach
• Boiling
• Distillation
• Filter Systems
• Sunlight Pasteurization
• UV Light

Is it safe to eat snow or ice? It is generally safe to eat snow or ice in the wilderness. Look for freshly fallen snow or ice that is white. Also avoid areas close to poultry farms, places producing chemical wastes and stagnant pools of water.