Radon in the workplace: implications of studies of post-remediation monitoring.

Radon gas has been shown to cause an increased incidence of lung cancer. In affected areas, levels in the overground workplace can be sufficiently high to be a health risk and remediation is required. In the UK, the workplace Action Level is 400 Bq m(-3). The variation of radon levels in the workplace was studied both before and after remediation. In most rooms, remediation resulted in a greater reduction at night than during the working day. The dose reduction, and therefore the health benefit, to workers is less than that predicted by the drop in radon averaged over 24 h. In order to obtain a health benefit to 75% of workers in our series, the 24 h average radon level in each room must be reduced to <225 Bq m(-3). It is recommended that UK Regulatory Agencies adopt a post-remediation workplace Action Level of 225 Bq m(-3).