By Timothy S. Donahue

Top Takeaways:

• New assessment: Japan’s health ministry said heated tobacco use indoors increases harmful airborne substances, including carcinogens.
• Evidence gap: Regulators say current research does not establish a direct link between secondhand exposure to heated tobacco and cancer risk.
• Policy implications: The findings could influence future Japanese regulations on indoor heated tobacco use.

Japan’s health ministry is reviewing whether tighter restrictions are needed for heated tobacco (HnB) products after a new government assessment found that indoor use increases airborne harmful substances, though evidence linking passive exposure to cancer remains inconclusive.

The Ministry of Health, Labour and Welfare released findings on May 21 after reviewing academic studies and research on secondhand exposure to heated tobacco products. According to the ministry, harmful substances in indoor air increased when heated tobacco products were used, and some carcinogenic compounds were detected in tests.

However, officials said that current scientific evidence does not allow regulators to determine whether passive exposure to heated tobacco products increases cancer risk. “The link with cancer risk cannot be determined at this stage,” the ministry concluded in its assessment.

Japan currently regulates conventional cigarettes and heated tobacco products differently indoors.

Under current rules, smoking combustible cigarettes is generally prohibited in restaurants and many other public indoor facilities, except in designated smoking rooms. Heated tobacco products, however, may still be used in certain indoor smoking rooms where eating and drinking are permitted because regulators have historically viewed the evidence on secondhand exposure as incomplete.

The ministry’s latest review appears unlikely to immediately close that distinction, but it could shape future regulatory debates.

Officials said some studies suggested possible links between passive exposure to heated tobacco aerosols and respiratory conditions, including asthma. However, the ministry described the current evidence base as limited. “The evidence connecting heated tobacco exposure with respiratory symptoms is somewhat weak,” the ministry said.

A ministry expert panel is expected to continue reviewing the findings and to consider whether Japan’s indoor-use regulations for heated tobacco products should be revised.

The issue has significant implications for the global nicotine industry because Japan remains one of the world’s largest and most important heated tobacco markets.

Philip Morris International, Japan Tobacco International, and British American Tobacco have all heavily invested in heated tobacco products in Japan over the past decade. PMI’s IQOS, in particular, saw early success in Japan after nationwide vaping restrictions and declining cigarette smoking accelerated consumer adoption of heated tobacco alternatives.

The Japanese market has often been viewed by global manufacturers as a testing ground for smoke-free product transition strategies because of unusually high heated tobacco penetration rates compared with many Western markets.

Public health experts and regulators worldwide remain divided on how secondhand emissions from heated tobacco products should be treated relative to those from combustible cigarettes and vaping products.