Despite the fact that Namibia is a large country with a sparse population where the amount of solid waste generated is relatively low, major environmental challenges in Namibia, just as in Southern Africa in general are related to pollution control and waste management. Pollution can be defined as "the presence in or introduction into the environment of a substance which has harmful or poisonous effects." A similar though more detailed definition of pollution is for example provided by the Solid Waste Management Policy of the City of Windhoek, which defines pollution as any change in the environment caused by - (a) any waste, substance or matter; or (b) noise, odour, dust or heat, emitted from or caused by any activity, including the storage or treatment of any waste, substance or matter, building and construction, and the provision of any service, whether engaged in by any person or an organ of state if that change has an adverse effect on public health or well‑being or on the composition, resilience and productivity of a natural or managed ecosystem (both short term and long term), or on material useful to people, or will have such an adverse effect in the future.