Workplace radon, done properly

What radon is

Radon-222 is a colourless, odourless, radioactive noble gas formed in the uranium-238 decay chain. It seeps from uranium-bearing bedrock and permeable soils into the lowest levels of buildings, where it can accumulate. ^[3] As it decays it releases alpha particles; breathe the gas in and those particles deposit their energy directly in the lining of the lung. That is the whole health problem - and it's why nothing about radon is visible or smellable. ^[4]

Why it matters for health

Radon has been classified by the IARC as a Group 1 human carcinogen since 1988. ^[3] After smoking, it is the leading cause of lung cancer, and the leading cause among people who have never smoked. ^{[1] , [2]} The landmark pooled analysis of 13 European case-control studies - over 7,000 lung-cancer cases - found risk rising measurably with exposure, with no threshold below which it disappears, and a clear effect even under 200 Bq/m³. ^[9] WHO summarises the long-term relationship as roughly a 16% rise in risk per 100 Bq/m³. ^[1] An estimated 3–14% of a country's lung cancers are attributable to radon, depending on radon levels and smoking prevalence. ^[1]

The numbers: reference levels

The WHO recommends a national reference level of 100 Bq/m³, and that it should not exceed 300 Bq/m³ where 100 is not achievable. ^{[1] , [4]} Finland sets the workplace reference level at 300 Bq/m³ as an annual average for regular work (over 600 working hours per year). ^[5]

The Finnish legal mandate

• The official measurement season runs from 1 September to 31 May, with detectors in place for a minimum of two months. ^[5]
• The annual average is obtained by applying a seasonal correction factor of 0.9 to the measured result. ^[5]
• Workplace inspections routinely find deficiencies, concentrated among small businesses in rented premises that assume the landlord is responsible. ^[7]

Who must measure

1. 1

   Underground workspaces

   Any workspace wholly or partly below ground level - anywhere in Finland.

2. 2

   Permeable soil and eskers

   Ground-floor workspaces on air-permeable soil, gravel, or esker ridges - anywhere in Finland.

3. 3

   STUK-designated obligation areas

   Ground-floor workspaces in municipalities or postal codes where over 10% of past measurements exceeded the limit.

The definitive obligation is set by STUK's official register of measurement-obligation municipalities and postal codes. ^[5] We confirm your exact status against it before any work begins.

The working-hour nuance

Many workplaces run ventilation only during the day, so a passive detector that integrates over nights and weekends can overstate the exposure workers actually receive. STUK therefore allows a continuous working-hour measurement (at least one week) and a defined formula to compute the annual working-hour average. ^[6] In about half of failing workplaces with timed ventilation, the working-hour concentration turns out below the reference level - no remediation required. ^[6]

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