Dust and radon levels on the west coast of Namibia–What did we learn?

Özet

The study investigated the potential for adverse health impacts from exposures to inhalable atmospheric dustand radon in the main towns along Namibia's central-western coast. An ambient air quality monitoring networkwas established at the end of 2016 to measure and track the inhalable dust (specifically PM10) and radonconcentrations. Data collected between November 2016 and the end of December 2018 were assessed and se-lected PM10samples were analysed for mineral and radionuclide content. In addition, emissions from anthro-pogenic sources were quantified and simulated using a regional dispersion model.Episodic dust storms associated with easterly winds are a common phenomenon during the winter months inthe western part of Namibia. During such events, dust is transported over long distances westwards towards andwell into the Atlantic Ocean. In view of the natural and anthropogenic nature of atmospheric dust, the studydifferentiated between sources of natural dust and those arising as a result of man-made processes.It was found that PM10concentrations were, on average, higher at the coastal monitoring stations than at thestations located further inland, often exceeding the daily World Health Organisation (WHO) guideline value.Whilst high atmospheric dust concentrations were mostly associated with easterly wind conditions, sea salt wasfound to be a significant PM10contributor at the coastal stations. Modelled results, which only included emis-sions from man-made sources, indicated that these sources contribute very little to the total PM10concentrationsmeasured at the coastal towns.The radiation exposure doses associated with the inhalation of atmospheric dust and radon were found to bewell-below the world-wide average inhalation doses provided by the United Nations Scientific Committee on theEffects of Atomic Radiation (UNSCEAR).