As if there already weren't enough good reasons for kicking the cigarette habit, doctors have found yet another: thirdhand smoke. That's the term doctors at MassGeneral Hospital for Children in Boston have given to the invisible particles and gases that linger on clothing, hair, carpet, furniture and other objects long after the smoke has dissipated.

The toxic residue — which includes carcinogens, heavy metals and radioactive materials — particularly poses a hazard to infants and young children because they can get it on their hands and ingest it when they stick their fingers in their mouths. The doctors who carried out the study hope that once smokers are aware of this additional hazard, they will take appropriate steps to reduce the risks that their tobacco habit poses to others.

Movements in Japan to curb smoking in public have made progress in recent years, but still lag far behind those in other nations. Most workplaces have restricted smoking to designated areas, as have all train stations. No-smoking taxis have become fairly commonplace in metropolitan areas and it is usually possible to book a nonsmoking room at hotels. Some wards in Tokyo have even banned smoking on streets.