As the world population grows so does the amount of waste we produce. It is then necessary to find some way of disposing of this waste. The soil has in recent years been selected as a medium in which to dispose of waste. The consequences have been serious in terms of soil pollution, damage to land, pollution of water courses and in some cases damage to the health of plants, animals and humans. Dispersal of waste from its source can be through the atmosphere, via the water bodies or directly into the soil itself. Once in the soil, not only can it enter the food chain thereby affecting plants, animals and humans but in some cases also alters the composition of the soil and its ability to perform its many functions. For example, there is evidence that some forms of pollution can diminish the populations of soil organisms such as earthworms and microbes, which decreases the biotic capabilities of the soil. Furthermore, once in the soil the pollutants can often be transported from there to the water bodies where they contribute to further damage to the environment. Soil pollution is now much more under the spotlight of government though there are many countries that still ignore the effects of soil pollution
There are both inorganic and organic pollutants. Some of the main toxic substances in waste are inorganic constituents such as heavy metals, including cadmium, chromium, lead, mercury, nickel, zinc, amongst others. The two main culprits responsible for the transfer of heavy metals to land are smelting and mining activities and the spreading of sewage sludge on land. In most countries there is a history of mining and smelting and certainly in the earlier years there was either ignorance about the damage that could be caused by the spoil material on land or a 'couldn't care less' attitude. Either way, the mining and smelting industries have left a legacy of undesirable heavy metal contents on significant parts of our landscape. In more recent years it has been the spreading of sewage sludge on the land that has led to the pollution of soils.
Organic based pollutants, such as PCBs (polychlorobiphenols), PAHs (polyaromatic hydrocarbons), pesticides, pathogens, are mainly associated with various industrial outputs and the chemicals used by the industries. There are many thousand synthetic chemicals used in industry and these can reach the soil by direct or indirect means. Pesticide manufacture relies on many of these chemicals and the widespread use of pesticides in intensive farming has meant that soils in many parts of the world have received significant quantities of them. It is now appreciated that some of the early insecticides such as DDT, aldrin and dieldrin had considerable damaging impact to the environment. The organic based pollutants have the potential to disrupt hormonal systems and modify the natural growth of humans and animals and to alter significantly the content and diversity of organisms in the soil.