In this study, an occupancy factor model was developed and used to calculate the average time
spent for outdoor and indoor activities along the coastline of the Erongo region of Namibia. A
closed ended questionnaire was developed and administered to 800 respondents who visited the
coastline for leisure, occupational and other activities. The mean time allocated for leisure activities
ranges from 13.00 to 1.00 h, occupational mean time between 10.18 to 9.06 h and the values of
other activities range from 16.66 to 11.00 h. The average computed time spent outdoor was found
to be 11.46 h and indoor calculated to be 12.54 h. This shows an outdoor factor of 0.48 and indoor
factor of 0.52 respectively. From the results obtained, the value of the absorbed dose rate ranged
from 93.27 to 105.95 nGy∙h−1 and the annual effective dose rate ranged from 121.01 to 176.61
µSv∙y−1 (UNSCEAR factor) and 292.60 to 413.63 µSv∙y−1 (present factor). The values obtained for
annual effective dose are higher than the acceptable limit. However, from this study, we can conclude
that the use of the UNSCEAR outdoor factor in the coastline will lead to underestimation of
effective dose by 24% based on the present factor.