Alberta Health Services said Tuesday that one of four patients affected by an accidental contamination a few days before had died in hospital.

On Friday, May 29, AHS said the contamination happened during a system cleaning that morning, the wrong valve was opened, and that released a chemical into the water supply used for dialysis at the Royal Alexandra Hospital.

“So the chemicals that were being used to flush the lines were peracetic acid and hydrogen peroxide, and we were doing a routine line flush when the wrong valve was opened,” AHS President and CEO Vicki Kaminski said.

“When we did the research on it, it says it causes a sunburn-like reaction inside the body, and there’s not a lot known about what the levels of exposures are inside, in the body.”

The contamination was discovered during regular monitoring – the water supply was turned off before it was flushed and cleaned. Officials said the water supply has been safely in use since Friday evening.

AHS said measures have been taken to ensure such an incident doesn’t happen again.

“We don’t want this to cause a lack of trust in the health care system, we want people to be reassured that no one is at risk, that we have in fact resolved the issue,” Kaminski said.

Officials said four patients were affected by the incident – one of them died Sunday, but they said it wasn’t clear if the death was connected to the contamination.

According to AHS, one other patient remained in hospital, one has been discharged from acute care to subacute care, and another has been discharged – they’re all being monitored by AHS.

With files from David Ewasuk