Trace metals in fruit and vegetable and their effects on human health

Trace metals occur naturally in the earth's crust, but human activities have greatly increased the mobilization and bioavailability of metals and, therefore, the chance of exposure to harmful concentrations. In fact, they along with other pollutants are discharged in the environment through industrial activity, car exhaust, heavy-duty electric power generators, refuse burning and use of pesticides in agriculture etc. Natural baseline levels of trace metals in air, soil, rivers, lakes, and oceans are usually low, but in certain forms, and at sufficiently high concentrations, trace metals can be toxic to organisms. Trace elements play an important role in biological and biochemical reactions in the living cells. They are stable and cannot be metabolized by the organisms, so, through the food, they tend to bio-accumulate. If the accumulation rate is higher than the detoxification rate, they can reach toxic concentration levels. Toxic metals in the human body can "replacing" essential nutrients, especially if deficient; for example Pb can replace Ca, Al can replace Mg, etc.. The substitution allows the enzyme systems to continue its function, but, if the intoxication degree exceed the tolerable limits, serious diseases take over. The major source of trace metals for man is the food, in particular, fruit and vegetables that are essential components of the diet, by contributing protein, vitamins, iron, calcium and other nutrients in short supply. In recent years their consumption is gradually increasing, particularly in the urban community. However, because of the increased environmental pollution, fruit and vegetables can also contain trace metals over a wide range of concentrations. That because the plants take off them from soil as well as from air particulate. In addition the contamination of fruit and vegetable products may be due also through irrigation with contaminated water, the use of fertilizers and metalbased pesticides, industrial emissions, transportation, the harvesting process, storage and/or at the point of sale. To monitor metal contents in these products is very important for crop yield technology, food nutrition and health impact. Many studies show that the trace metals at relatively high concentration may disturb the normal physiology (the normal functions of central nervous system, liver, lungs, heart, kidney and brain, produce hypertension, abdominal pain, skin eruptions, intestinal ulcer) until to produce different types of cancer.