Radon in Japan: The Invisible Threat No One Talks About

Why Japan Needs Regulation and a Professional Framework

Radon — a colorless, odorless, radioactive gas — is recognized worldwide as a significant contributor to lung cancer, second only to smoking. Agencies like the World Health Organization (WHO) and the U.S. Environmental Protection Agency (US EPA) have long provided guidelines and enforced regulations to protect people from its harmful effects. Yet, in Japan, despite its geology and seismic activity that can easily create radon-prone areas, radon exposure remains largely unregulated.

As a Certified Industrial Hygienist (CIH®), holder of a PhD in Geo-Environmental Engineering from Hokkaido University, and certified by the US National Radon Proficiency Program (NRPP) in both radon measurement and mitigation, I find this silence deeply concerning — not only as a scientist but also as someone who has actively worked inside some of the most demanding environments, including multiple U.S. military bases across Japan.

The Global Standard vs. Japan's Reality

Globally, radon is taken seriously. Exposure limits, mandatory measurements, and mitigation procedures are established in many countries to reduce risks to occupants of homes, workplaces, and public buildings. Entire sectors — construction, housing, and facility management — integrate radon management into their daily practices.

In contrast, Japan currently has no enforceable regulation from the Ministry of the Environment or any other agency addressing radon exposure. No recommended action levels. No legal obligation to measure. No requirement to mitigate.

This is not just a regulatory gap — it is a missed opportunity to safeguard public health.

The Problem Is Bigger Than Individual Action

While some may argue that voluntary testing and mitigation can address the issue, the reality is different. Without:

• National regulations,
• A recognized exposure limit,
• Consistent building practices,
• And a dedicated professional community,

there is little incentive for property owners, designers, or managers to take action. Leaving radon risk management entirely up to individuals will never be enough.

What Japan Needs — Now

Japan needs to take two urgent steps:

1. Establish radon regulations under the Ministry of the Environment, including mandatory assessment and mitigation protocols.
2. Create a Japan Association of Radon Scientists and Technologists, to foster a professional community, ensure competence, and develop national guidelines adapted to the Japanese context.

These two pillars — regulation and a professional community — are indispensable if Japan wants to align itself with international best practices and, most importantly, protect its people.

We Know This Can Be Done

In our work inside U.S. military facilities across Japan, we consistently comply with U.S. standards for radon assessment and mitigation. This has provided us with extensive, hands-on experience in:

• Measuring radon under controlled and challenging conditions.
• Designing and executing mitigation systems.
• Ensuring compliance with strict health and safety requirements.

It is precisely because we have seen how systematic and effective radon management can be that we advocate for Japan to move forward — not through voluntary guidelines, but through meaningful regulation.