Mini-review on chromium in agricultural plants and consequences for human nutrition

Abstract

Chromium is found in the air, water and ground in the form of Cr(III) and Cr(VI), and is produced by both natural processes and human activity. Most airborne chromium is deposited in water or in the ground and sticks strongly to soil particles or to the sediment present in water, where it is sequestered. Only a fraction of the chromium remains dissolved in water. Chromium, like other trace minerals, is present in many foods (meat, seafood (e.g shellfish), eggs, wholegrain cereals, dried fruit and certain fruit and vegetables). It is essential for our metabolism in its trivalent form Cr(III), whereas its hexavalent form Cr(VI) is toxic. In humans, trivalent chromium is a necessary mineral for the correct metabolism of sugars. Like iron, it also has the task of transporting proteins in the bloodstream, and by binding to RNA molecules it is involved in their synthesis. A lack of chromium causes glucose intolerance and high levels of triglycerides and cholesterol. Hexavalent chromium is toxic and a skin and lung irritant. If swallowed, it can cause problems to the stomach, intestine, liver and kidneys. Pesticides and fertilisers containing chromium are often used in agriculture. However, many studies claim that hexavalent chromium does not penetrate the tissues of cultivated plants for food purposes and for feed production, thanks to protection systems developed by the plants themselves during their evolution. Plants tend to absorb only trivalent chromium in amounts that rarely prove to be dangerous for human nutrition and for livestock feeding.