The main pollution effects concern human health and cover all aspects of the physical environment - air, water and land, including the effects of climate change. Human activities which are sources of pollution arise from domestic, commercial, industrial and military sectors and their effects are influenced by various issues, trends and public sector programmes, such as safe water and food, management of waste, increasing use of chemicals in agriculture, and urbanization. Types of pollutants which are negatively impacting health include litter, toxic chemicals, nuclear waste, lead, spoil from mining, food and water contaminants; and the polluting effects of over-population.