Secondhand smoke induces the cancerous mutation of genes that are different from those affected among active smokers, increasing the risk of lung cancer among nonsmokers, according to a recent study by the National Cancer Center Japan.

Researchers say the study has shown how passive smoking causes genetic mutations, providing further evidence of the harmful effects of secondhand smoke. They also call for stricter domestic laws to ban smoking in all indoor spaces in line with international standards.

Currently, restaurants and bars in Japan are allowed to have smoking areas under certain conditions, which could cause patrons to inhale tobacco smoke involuntarily.