Seasonal variations of Pb214 and Po210 concentrations in the surface air in São José dos Campos (23.18° S, 45.89° W, 600 m asl) Brazil

Radon (Rn222) and its progeny are the main source of ionization in the low troposphere besides being also the main natural source of equivalent dose to the public especially radon short-lived progeny. By an indirect method of counting alpha particles from cellulose membrane filters of pore-size 0.3 μm through which surface air was pumped, the surface air concentration of Pb214 and Po210 in São José dos Campos (23.18° S, 45.89° W, 600 m asl, Brazil) from July 2005 to August 2006 is determined and assessed. The annual average values of air concentration for them were 20 ± 16 Bq/m3 and 249 ± 209 μBq/m3 (both 1 standard deviation), respectively, with statistically significant highs (95% confidence) occurring in August.