Variations of outdoor radon concentrations in Hong Kong

The outdoor radon concentrations in Hong Kong were measured using a grab sampling technique and the variations with floor levels, building shapes, building densities and geological compositions were investigated. It was found that the outdoor radon concentrations decreased with higher floor levels and lower building densities. The mean outdoor radon concentration in granitic areas was higher than for other types of geological composition. The mean outdoor radon concentration was found to be about 28 Bq m-3 which was higher than the global population-weighted value of 10 Bq m-3. The higher outdoor radon concentrations may enhance the indoor radon concentrations through air exchanges between the outdoor and indoor environments.