The U.N. agency said every 10th lung cancer death is related to occupational hazards, and about 125 million people worldwide are exposed to asbestos at work, leading to at least 90,000 deaths each year.

Thousands more die of leukemia from workplace exposure to benzene -- an organic compound used in rubbers, dyes, drugs, and pesticides, widely used in chemical and diamond industries -- and those exposed to second-hand smoke at work have twice the risk of lung cancer than those in a smoke-free environment.

"Known and preventable exposures are clearly responsible for hundreds of thousands of excess cancer cases each year," Maria Neira, WHO director of public health and environment, said in a statement released in Geneva.

The WHO urged governments and industry to tighten safety standards to ensure workers are not exposed to carcinogens. Stopping the use of asbestos, using benzene-free organic solvents and banning tobacco in the workplace could help prevent hundreds of thousands of unnecessary deaths, it said.