The short answer is volume and vulnerability.

A person drinks approximately 2 liters of water per day. During a single hemodialysis treatment, a patient's blood is exposed to 120-150 liters of dialysate, which is made primarily from purified water. This is a direct interface with the patient's bloodstream across the semi-permeable membrane of the dialyzer.

Tap water, while safe for drinking, contains minute levels of contaminants like minerals (calcium, magnesium), chemicals (chloramine, chlorine), and bacteria. In small amounts, our digestive systems can handle these. However, when introduced directly into the bloodstream in large volumes, these same contaminants can cause severe complications, including:

• Hemolysis: Destruction of red blood cells.

• Toxicity: From metals like aluminum or copper.

• Chronic inflammation: From bacterial endotoxins.

• Long-term health issues: Such as bone disease or anemia.

Therefore, the water must be purified to an exceptionally high standard to be safe for hemodialysis.

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