Naturally occuring radioactive materials (NORM) are present in the environment and can be concentrated by technical activities, particularly those involving natural resources. These NORM deposits are highly stable and very insoluble under environmental conditions at the earth's surface. However, reducing or oxidant conditions or pH changes may enable a fraction of naturally occurring radionuclides to eventually be released to the environment. In this paper the leachability of210Pb and210Po was determined in three samples coming from a refractories production plant (dust, sludge, finished product), in one dust sample from a steelwork and in one ash sample coming from an electric power station. A sequential extraction method consisting of five operationally-defined fractions was used. The average leaching potential observed in the samples from the refractory industry is very low (mean values: 5.8% for210Pb and 1.7% for210Po). The210Pb and210Po leachability increases for the ash sample coming from an electric power plant using carbon (17.8% for210Pb and 10.0% for210Po); for the dust sample coming from a steelwork, the percent soluble fraction is 41.1% for210Pb and 8.5% for210Po. For all samples the results obtained show that210Pb is slightly more soluble than210Po.