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

The concentrations of⁴⁰K,²²⁶Ra,²³²Th and¹³⁷Cs were determined in the upper layers of soils in the central coastal region of Venezuela. The activities of¹³⁷Cs are higher in the areas where the forest is well developed, oriented towards the wind and at higher elevations. The origin of the¹³⁷Cs deposition is from water input from the clouds directly in the cloudforest and rainfall from the northeast trade winds. Even though the values of¹³⁷Cs are much higher in these areas, there is little or no significant increase in the health risk. The natural radioactivity is correlated with the geology in the region except in the area of Urama. The values for the natural radiation background are as follows: for potassium between 1–3%, for radium between 1–3 ppm and for thorium the range was 6–39 ppm. The corresponding amounts of absorbed dose rates in air, the exposure rates and the annual 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 equivalents include the contribution of the global average (2.57 mSv/y) of the rest of the natural sources of radiation. Finally, the largest natural radioactivity background, was found near Chichiriviche as a result of the massive granite deposits in this area, but again there is no significant health risk.