How can clams save lives in Poland?

Clams and some other mollusks filter water to remove debris and pollutants. A water station in Poland has a setup wherein eight clams are monitoring the city’s drinking water. When they encounter heavy metals, pesticides or other pollutants, they close their shells. They are hooked up to computers that register whether their shells are open or closed. When 4 out of 8 are closed, the water supply is automatically shut off, potentially saving lives.