How soil affects health

We rely on soil to provide nutrients for the plants that produce our food. There are 18 elements known to be essential for healthy plant growth. Some of these are required in significant amounts and are referred to as macronutrients, others are only required in much smaller quantities are referred to as micronutrients. In addition the soil contains a range of other elements that are beneficial to plants, animals and man in very small quantities, these are known as trace elements. The soil is a major source of these elements and is able to supply the needs of most plants in natural and semi-natural situations, except in some special cases, (for instance in waterlogged and acidic soils, where availability for plants is affected). Plant communities in the wild are usually adapted to the environment they grow in and naturally select soils with the conditions to suit them.

Animals can have different requirements to plants in terms of nutrients and trace elements. In some cases soils can be well suited to certain plants yet not as suited to the animals that graze on them. Equally, there are several elements in soils that are not essential to plants but are to animals and humans, examples include chromium, iodine and selenium. Each soil type contains macronutrients, micronutrients and trace elements though the quantities of each will vary from soil to soil, and with degree of development of the soil. This is one of the reasons the natural flora and fauna are so variable across the world and that soils can meet such a wide variety of needs. Not all soils have the 'perfect' set and amount of nutrients. This will depend to some extent on the rock or sediment from which the soil has developed, the use to which the soil has been put in the past and in particular and the extent to which the soils have come in contact with pollutants and contaminants. Nutrients are removed from the soil by plants growing. When crops are harvested, this can reduce the nutrients in the soil - which is why farmers add fertilizers back to the soil.

Changes to the soil can lead to changes in the delicate balance of nutrients in the soil. Adding too much fertiliser for instance can cause chemicals like nitrates to enter our drinking water, leading to 'cyanotic' diseases such as 'Blue Baby Syndrome'. Toxic elements can also be added to soil by pollution events and have an impact on health, for instance after the Chernobyl incident (26 April, 1986), radioactive particle contaminants fell back to the earth across a huge area covering many countries. People living near to Chernobyl today have a higher risk of diseases such as Thyroid cancer than they did before. In Britain levels of certain radioactive particles from Chernobyl were recorded after falling in parts of Wales and Cumbria.