For the past decade, exposure to chemicals that keep swimming pool waters clear and germ-free has sent an average of 4,535 people a year to the emergency room for treatment.

According to newly released data from the Centers for Disease Control and Prevention, more than half (56 percent) of the injuries are occurring at a home pool, and more than a third of the injured (36 percent) are children and teens. Poisoning is the most common injury, attributed to breathing in chemical fumes, vapors or gases, usually while opening containers.

According to the National Swimming Pool Foundation, a nonprofit group, injuries also occur when pool chemicals are not secured out of children’s reach and when people enter a pool too soon after chemicals have been added.

To ensure safety, people tasked with adding chemicals to pools should wear goggles, gloves and any other safety equipment recommended on the product labels. They should carefully follow other directions on the labels, too. The CDC says to never mix pool chemicals, adding that it is “particularly dangerous to mix chlorine and acid.”

This is the right time of year to be careful about using pool chemicals: About two-thirds of the injuries related to pool chemicals occur annually from Memorial Day through Labor Day, the CDC says.