Several hazardous chemical spills were reported in late 2009. In Wellesley, Mass., four employees of the Boston Sports Club were hospitalized when a pool worker accidentally added muriatic acid to a large quantity of chlorine, creating a toxic cloud that required hazmat crews to correct. All injured parties were treated and released.

Mount Vernon (Ind.) Junior High School’s pool was closed in December after its water tested positive for high amounts of chlorine. The testing took place after parents of swim team members reported their children were suffering from hair loss and rashes. Kirn Middle School in Council Bluffs, Iowa, discovered a chlorine leak in its pool area shortly before winter break. Firefighters responded while students were evacuated, and the leak was remedied in time for them to return to classes later in the day.

Additionally, nine people, including three children, suffered the effects of a chlorine leak at a Triadelphia, W. Va., hotel pool. None were seriously hurt, though they did experience burning eyes, sore throats and vomiting.