Variation of Indoor Radon Levels in Some Cavesof Parque Estadual Turistico do Alto Ribeira(PETAR), SP, Brazil with Ventilation and Rain

摘要

In order to assess the radon exposure for the tour guide workers, radon levels in severalgalleries of the most visited caves of PETAR (High Ribeira River Turistic State Park), weredetermined by using Makrofol E tracks detectors. A two-years surveillance, from 2003 to 2005,showed radon average levels varying from 153 ± 44 Bq.m~(-3)to 6358 ± 1619 Bq.m~(-3). Those resultsshowed that the wide variation between the minimum and maximum concentrations values arestrongly related with cave ventilation. In order to establish other factors contributing to thisvariation, beside the well known temperature effect, rain data over the entire period were alsoconsidered, showing that, apparently, radon concentrations inside the caves rise with drought.