 STUDY POPULATION The study will be performed in an urban and a rural setting in Tanzania. In the urban setting we aim to include men from different employment categories at larger industries, which potentially have already been identified Twinga cement, ALAF-Aluminum Company, Bakhresa Food Industry, Simba plastics Industry, and Mohamed Enterprise Food Industry, and in addition we will include men from the CollegeUniversity environment in Dar es Salaam Vocational Education Training Dar-es-salaam branch, and Dar-es-salaam Institute of Transport. From the 2002 Census it has been estimated that the population of Dar es Salaam was 2,497,940 