A proposed class-action lawsuit has been launched against two chemical companies that make pesticides widely blamed for massive bee deaths, a growing concern in Europe and North America.

The widespread use of a common weed killer has led to runoff. Atrazine can end up in lakes, streams and sometimes in drinking water.

Scientists say more research into the chemical atrazine is needed, but some studies show it's associated with birth defects, breast cancer and poor semen quality.