[en] Phosphogypsum (PG) is a waste product of the phosphoric acid production process and contains, generally, high activity concentrations of uranium series radionuclides. It is stored in piles formed over the last 40 years close to the town of Huelva (Southwest of Spain). The very broad expanse of the PG piles (about 1200 ha) produces a local, but unambiguous radioactive impact to their surroundings. In 1992, the regional government of Andalucia restored an area of 400 ha by covering it with a 25-cm thick layer of natural soil and, currently, there is an additional zone of 400 ha in course of restoration (un-restored) and the same area of active PG stacks. Most studies have concluded that populations living close to PG stacks are not subjected to a significant health risk. However, it is still not clear whether employees who spend numerous hours on active PG stacks are subjected to a significant health risk. The activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K have been measured by high detection efficiency gamma ray spectrometry from inactive PG stacks, restored and un-restored zones. The average activity concentrations of ²²⁶Ra (Bq kg^-1) in the active PG stacks, un-restored and restored zone were 647, 573 and 83 respectively. The corresponding values for ²³²Th and ⁴⁰K (Bq kg^-1) were 8, 10 and 25 and 33, 47 and 225 respectively. As a measure of radiation hazard to the occupational workers and public, the Ra equivalent activities, the representative level index and dose rates due to natural radionuclides at 1 m above the ground surface were estimated. The average of absorbed dose rates due to ²²⁶Ra, ²³²Th and ⁴⁰K (nGy/h) from inactive PG stacks, un-restored and restored zones are 284, 255 and 55.The calculated external γ-radiation average dose (mSv/y) received by the workers of the phosphogypsum piles are estimated to be 0.293, 0.263 and 0.057 respectively which is far below the international agreed dose limit of 20 mSv/y for workers. Also, we can conclude that the radiation dose to a member of the public resulting from the use of phosphogypsum piles is negligible compared to the average annual effective dose from natural sources (2.4 mSv/y), even under a worst case scenario assuming the complete accumulation of radionuclides in soil over may years. (author)