Environmental radioactivity near the central coast of Venezuela and its radiological impact

The concentrations of K-40, Ra-226, Th-232 and Cs-137 were determined in th e upper layers of soils in the central coastal region of Venezuela. The act ivities of Cs-137 are higher in the areas where the forest is well develope d, oriented towards the wind and at higher elevations. The origin of the Cs -137 deposition is from water input from the clouds directly in the cloudfo rest and rainfall from the northeast trade winds. Even though the values of Cs-137 are much higher in these areas, there is little or no significant i ncrease in the health risk. The natural radioactivity is correlated with th e geology in the region except in the area of Urama. The values for the nat ural radiation background are as follows: for potassium between 1-3%, for r adium between 1-3 ppm and for thorium the range was 6-39 ppm. The correspon ding amounts of absorbed dose rates in air, the exposure rates and the annu al effective dose equivalents are in the following ranges respectively: 11- 39 pGy/s, 4-16 uR/h and 0.25-0.86 mSv/y. The annual effective dose equivale nts include the contribution of the global average (2.57 mSv/y) of the rest of the natural sources of radiation. Finally, the largest natural radioact ivity background, was found near Chichiriviche as a result of the massive g ranite deposits in this area, but again there is no significant health risk .