What size of filter is effective against Giardia cysts?

• A. 5 microns
• B. 3 microns
• C. 1 micron
• D. 10 microns

Answer: (C)

Giardia cysts are single-celled organisms that can be found in contaminated water and can cause gastrointestinal illness in humans. To effectively remove these cysts from water, the size of the filter used is crucial. Giardia cysts typically range in size from approximately 8 to 14 microns. Therefore, a filter with a pore size of 1 micron is highly effective in capturing Giardia cysts, ensuring that they do not pass through and contaminate the water supply.

A 1-micron filter can effectively trap objects larger than itself, including Giardia cysts, making it a preferred choice for water treatment in areas where contamination is a concern. This level of filtration provides an extra margin of safety, as it not only addresses Giardia but can also trap other potential pathogens and contaminants.

Filters with larger pore sizes, such as 5 microns, 3 microns, or 10 microns, may allow Giardia cysts to pass through, which could lead to potential health risks if the water is consumed. Therefore, for effective removal of Giardia cysts from water, a filter size of 1 micron is the most reliable choice.