The additional dose due to environmental radioactivity in the undergro
und transport system of Caracas was determined. Measurements employed
the exposure of SSNTD (LR-115) to determine radon concentration and TL
D (for gamma dose). The average radon concentration is 30 Bq/m(3). Cal
culated effective dose for METRO employed personnel is 1.0 mSv/y and f
or a typical passenger is 10 mu Sv/y.