An official in West Virginia has raised fresh concerns about the impact of a chemical spill that left 300,000 people without tap water for days. On Wednesday, the vice chair of West Virginia’s Environmental Quality Board, Scott Simonton, told a state legislative panel water sampling had detected formaldehyde.

Scott Simonton: “I can guarantee you that the citizens of this valley are, at least in some instances, breathing formaldehyde. If they’re taking a hot shower, this stuff is breaking down the formaldehyde in the shower or in the water system, and they’re inhaling it. The biggest risk from formaldehyde is cancers of the respiratory system.”

West Virginia’s top health official has disputed Simonton’s claims, saying formaldehyde would only be produced by the spilled chemical at very high temperatures.