What Is Secondhand Smoke in Japan? (2026) The Legal Definition and the Basic Rules
Table of contents
The definition, and why the wording matters
Secondhand smoke is an everyday phrase, but in Japan it is also a defined legal term. Article 28 of the Health Promotion Act describes it as exposure to smoke generated from tobacco through another person's smoking (source: https://laws.e-gov.go.jp/law/414AC0000000103). The test is not whether you smoked, and not whether the exposure was intentional — only whether you were exposed to smoke produced by someone else. Where that exposure is actually regulated is set out separately, facility type by facility type.
Tobacco smoke is also named according to how it is produced. Smoke drawn in by the person smoking is mainstream smoke; smoke rising from the lit tip is sidestream smoke; smoke breathed back out is exhaled smoke. What reaches bystanders is mostly the latter two. Japan's Ministry of Health, Labour and Welfare refers to the combination as "environmental tobacco smoke" — sidestream smoke mixed with the exhaled smoke of the person smoking (source: MHLW e-Health Net https://kennet.mhlw.go.jp/information/information/tobacco/t-03-002.html). This article does not give figures comparing the constituents of mainstream and sidestream smoke, because we could not confirm such figures in a primary public source at the time of writing.
What the public health sources say about health effects
On health effects this article quotes rather than evaluates. MHLW e-Health Net states that non-smokers exposed to tobacco smoke face increased risk of ischaemic heart disease and stroke by the same mechanisms as smokers, and that there is sufficient evidence to infer a causal relationship between secondhand smoke and those conditions (source: https://kennet.mhlw.go.jp/information/information/tobacco/t-03-002.html). For cancer, the same source states that a causal relationship with lung cancer has been confirmed, and that Japanese research reports roughly a 1.3-fold increase in lung cancer risk where secondhand smoke exposure is present (source: https://kennet.mhlw.go.jp/information/information/tobacco/t-03-001.html). For anything concerning your own health, please consult a medical professional.
The indoor rules in five lines
- Schools, hospitals, childcare facilities, government offices, and passenger vehicles and aircraft are smoke-free across the whole premises, with no indoor smoking room permitted
- Facilities used by many people, passenger ships and trains, and restaurants are non-smoking indoors by default
- Premises-wide smoke-free facilities may still place an outdoor smoking spot, but only where the required measures have been taken
- Nobody under 20 may enter a smoking area at all, even if they are not there to smoke
- Facilities with smoking equipment must display the prescribed signage — so the sign at the door is how you tell
In statutory language the first group are "Type 1 facilities" — defined in Article 28 as facilities used mainly by people at high risk of harm from secondhand smoke, plus national and local government office buildings — and the second are "Type 2 facilities", meaning facilities used by many people other than Type 1 and smoking-purpose facilities (source: https://laws.e-gov.go.jp/law/414AC0000000103). Where smoking indoors is permitted at all, it happens inside one of four kinds of compliant room, and every one of them is off-limits to under-20s (source: MHLW https://jyudokitsuen.mhlw.go.jp/smoking_room/).
Outdoors: consideration, not measurements
Article 27 asks anyone smoking outside a designated no-smoking place to have regard to their surroundings so as not to cause unwanted secondhand smoke, and asks facility managers who set up a smoking place to choose a location that will not cause it. It does not specify a distance. Local governments add their own street-smoking ordinances on top, and the zones and penalties differ from one municipality to the next — check the local official site before you travel. Our breakdown by municipality is in the guide to street smoking penalties, and the wider picture is in our overview of smoking areas and etiquette in Japan. Because the outdoor rule is about judgement rather than metres, knowing where the designated smoking spots actually are is useful in both directions: it lets people who want to avoid smoke keep their distance, and it lets people who smoke do so where they are supposed to. You can check locations on the MottoSuitai smoking area map. How far outdoor smoke is said to travel is covered in our article on how far tobacco smoke reaches.
Scope of this article
This is a third-party summary based on e-Gov, MHLW and MHLW e-Health Net sources as of August 2026. Statements about health effects are quotations from public bodies, not independent medical assessment, and nothing here is a judgement about any particular venue. Outdoor rules vary by municipality, so please check official local information before you go. This article does not encourage smoking, and it is not written to criticise people who smoke within the rules.
Frequently Asked Questions
Q.How does Japanese law define secondhand smoke?
A.Article 28 of the Health Promotion Act defines it as a person being exposed to smoke generated from tobacco through another person's smoking (source: https://laws.e-gov.go.jp/law/414AC0000000103). The test is exposure to someone else's smoke — not intent, and not whether you are indoors or outdoors.
Q.What is the difference between mainstream and sidestream smoke?
A.Mainstream smoke is drawn in by the person smoking, sidestream smoke rises from the lit tip, and exhaled smoke is breathed back out. Bystanders are mostly exposed to the latter two, which MHLW e-Health Net together calls "environmental tobacco smoke" (source: https://kennet.mhlw.go.jp/information/information/tobacco/t-03-002.html). We do not quote figures comparing their constituents, as we could not confirm them in a primary public source.
Q.Can I smoke outdoors in Japan?
A.Outdoors and on private property are generally outside the Health Promotion Act's smoking ban, except in designated no-smoking zones. Article 27 still requires consideration for the people around you. Separately, many municipalities restrict street smoking by ordinance, with zones and penalties that differ locally — check the official site for the area you are visiting.
Q.How do I tell whether a restaurant allows smoking?
A.Facilities with smoking equipment must display prescribed signage at the entrance, and where there is a smoking room, at that room's entrance too (source: MHLW https://jyudokitsuen.mhlw.go.jp/point/, Chiba Prefecture https://www.pref.chiba.lg.jp/kenzu/tabako/jyudoukitsuen.html). A restaurant with no such sign is non-smoking indoors. Individual venues can change their policy, so check the sign at the door and the venue's own information.