At the same time the colonial powers became aware of the problems that urbanization brought with it. The rural-urban migration pulled labour away from the countryside where the important export products were made. The Africans usually lived in small spaces and under poor sanitary conditions. They were therefore prone to illnesses like malaria. One of the colonial governments' response was to separate Europeans, Asians and Africans from each other and establish influx control laws. In South Africa this resulted in the official policy of apartheid from 1950. This was also a policy that was especially common in settler cities like Harare, Lusaka and Nairobi.