Why might household boiling or activated-carbon filtering fail to remove dangerous contaminants?

Household boiling and activated-carbon filtering are popular, inexpensive methods for water treatment, but they are not comprehensive solutions for all types of contamination.1

Limitations of Boiling

While boiling is highly effective at destroying biological threats like bacteria, viruses, and parasites, it does not remove chemical contaminants. Dangerous substances such as heavy metals (e.g., lead) and pesticides remain in the water after boiling. Furthermore, boiling does not eliminate all dissolved salts or pollutants introduced via surface runoff.2

Limitations of Activated-Carbon Filtering

Activated carbon is primarily used for adsorption—the process of attracting and holding dissolved organic substances that affect the taste, odour, or colour of water. However, these filters may not be sufficient to remove a wide range of inorganic chemicals, radioactive materials, or certain microbial pathogens. If a filter is not properly maintained or becomes saturated with impurities, its effectiveness in removing contaminants is significantly compromised.31

Because these methods often fail to address the full spectrum of inorganic and chemical pollutants, they should not be relied upon as a total solution for water safety.21