Soil elements affecting health

There are a number of elements that are linked with human and animal health, including aluminium, arsenic, cadmium, chromium, copper, fluorine, iodine, lead, selenium, thallium and zinc. The list below gives some examples of the links between some of these and animal and human health:

Aluminium, which becomes soluble in soils below pH 5.5. Acidification of soils to a pH below this level leads to increased solubility of aluminium in the soil as a result of which it can be leached out of the soil into streams and other water supplies. This is often a side-effect of acid rain. Long term uptake of aluminium in humans has been linked with neurological problems and Alzheimers disease in humans. Aluminium in water is extremely toxic to fish also.

Cadmium in high amounts in the soil can be related to development from certain parent rocks but more commonly is due to the activities of mankind such as mining, burning of fossil fuels, disposal of waste such as cadmium-containing batteries, use of phosphatic fertilisers. Cadmium can accumulate in food plants, and food is the main pathway by which cadmium enters the body. Cadmium has been associated with damage to kidney functions.

Selenium occurs naturally in all soils but the amounts vary greatly. In the USA and New Zealand animals have suffered from there being very low amounts in some soils. Virtually all the selenium in the body comes in via food. In animals a deficiency in dietary selenium leads to degeneration of heart and skeletal muscles. In humans it has also been linked with degeneration of the heart muscles. In parts of China, toxic levels of selenium have been reported in soils leading to severe disease of the muscles.

Lead has been known for a long time to be at toxic levels in some soils. The high levels can be inherited from the parent rock, but they are often associated with the extensive period of lead mining over several centuries. High levels in the soil passing via food into the body have been associated with a several serious forms of illness affecting both young and old people. In Roman times and even the Middle Ages, many women used to use powdered white lead oxide as a face cosmetic - giving their faces a white appearance. This was very popular at the time - but is now recognised as a significant source of contamination!

Exploring the links between soils and human and animal health is a new and exciting challenge for soil scientists who have a role to play alongside geochemists, medical scientists and food and farming experts in understanding how the variations in soil composition and the influence of pollutants and contaminants can affect humans and animals.