FIG 1.

Geographic distribution of dust samples. A total of 467 samples of dust that had accumulated on outdoor surfaces were collected from 33 countries and 6 continents. The squares denote samples having both bacterial and fungal data, the circles denote samples having only bacterial data, and the triangles denote samples having only fungal data. For each continent, a higher resolution map of the sampling locations in one sample country is shown. See Fig. S1 for all the types of external surfaces.