Lead

Lead was known and mined in the ancient times, and its ease of use promoted its wide application. Lead was used for water-supply systems, first in ancient Greece, later in the Roman Empire. Wealthy Romans used lead wine cups, kitchen utensils, decorations, and other paraphernalia, and it is suggested that this might have led to chronic poisoning (Gilfillan, 1965). Although the toxic properties of lead had already been known in ancient Greece, Egypt, and Rome, where lead poisoning was known as 'saturnism', the metal was not identified as a toxic component of food until the 11th Century (Landrigan, 1990; Mahaffey, 1990). Despite this knowledge, in England in the 19th Century, candies were colored with lead chromate and white lead, and the use of lead for water pipes has survived up to the present time. Tea was also regenerated using lead chromate, and minium (Pb3O4) was applied to cheese to make the rind red.

At present, lead is used for production of accumulators, petrol, crystal glass, matches, paints, pesticides, and printing types, hunting ammunition (with arsenic), and anti-corrosive coatings. It is also used in the chemical, rubber, textile, and ceramic industries, and in many other branches of human economic activity.

To date there is no proof for the inevitability of lead for plant and animal organisms (including humans), whereas its toxic activity is widely known. More reported poisonings involved lead than any other elements (Philip and Gearson, 1994a,b). As early as in 1774, Lind noted that lemon juice stored in lead-enameled containers may cause poisoning. A special royal commission was appointed to study the problem four years later.

Food contamination may result from transmission of lead from glaze, enamel, or tinning on kitchen dishes, or from the lead on surfaces of containers or pipes used for storage, processing and transportation of food products. The occurrence of lead in food can also result from environmental contamination, as plants and animals may assimilate lead during growth and incorporate it into their tissues. The level of lead found in plant tissues is proportional to its concentration in the environment, and in cases of animals, the feed and water supplies also play important roles (Vreman et al., 1988; McLaughlin et al., 1999; Sedki et al., 2003).

Symptoms of lead poisoning occur after a daily dose of 2 to 4 mg is ingested for a period of a few months, while daily doses of 8 to 10 mg will cause poisoning after only three to four weeks.

At the onset of poisoning, symptoms include chronic headaches, hyper-activity, muscle tremor, lead colic, and lead line (1 to 2 mm) on gums. Hyperactivity and intelligence-quotient decrease are observed in cases of chronic poisoning in children. Lead poisonings result in anemia due to hemoglobin synthesis disorders. Neurological, encephalopathic, enzymatic, and mutagenic changes, as well as liver, kidney, spinal medulla, and brain damage, are also observed. Lead may be transmitted from the blood of pregnant women to their fetuses, which may result in congenital defects (teratogenic effect). Lead compounds may also exert carcinogenic effects (Philip and Gerson, 1994b; Johnson, 1998; Silbergeld, 2003).

All food products contain some lead. They usually do not exceed the level of 0.1 to 0.2 mg per g, although venison may contain up to several mg per g due to its contamination via ammunition. In order to lower lead intake in Poland, the highest allowed concentrations have been established for various food products, within a range from 0.2 mg per g (for milk) to 2 mg per g (dried fungi). For most products, the values are set between 0.1 and 0.3 mg per g (Dz. U., 2003). The Joint FAO/WHO Expert Committee calculated that lead PTWI should not exceed 25 mg per g of body weight (WHO, 1993). It is particularly important that infants and children should be protected against the possibility of lead uptake.

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