Abstract. Measurements of the composition of aerosol partitioned into two size fractions, fine (particle aerodynamic equivalent diameter, dp _< 2.5 jim) and coarse (2.5 < dp <_ 10 jim) were made at a high-altitude site over equatorial eastern Africa on Mount Kenya to study long-range transport of aerosol and to determine the extent of interhemispheric transport at the equator. The two size fractions allow long-range transport aerosol to be distinguished from those more locally derived.
Exposures to various components of the natural background radiation in Kenya were estimated using measured activity concentrations of natural radionuclides and conversion factors. Contributions to the total effective dose include: 0.1 to 2.0 mSv.y -1 from terrestrial gamma radiation; 0.2 to 0.7 mSv.y -1 and a per capita of 0.4 mSv.y -1 from cosmic radiation; and 0.4 to 6.0 mSv.y -1 from inhalation of radon ( 222 Rn). Radon concentrations also range from 5 to 1200 Bq.m -3 in indoor air and from 1 to 410 Bq.1 -1 in drinking water. Considering the population distribution in relation to living habits of the people and to the relief and the geology in Kenya, it is concluded that the average annual effective dose in Kenya is higher than the global average. Ingestion of volcanic ash by some people, particularly pregnant women, was also identified as an additional (unusual) internal exposure pathway.
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