The area around the Pribram lead smelter has been recognized to be heavily contaminated by lead (Pb). In the early 1970s, several episodes of livestock lead intoxication were reported in this area; thereafter, several epidemiological and ecological studies focused on exposure of children. In contrast to earlier studies, the recent investigation (1992-1994) revealed significantly lower exposure to lead. From 1986-1990, recorded average blood lead levels were about 37.2 micrograms lead (Pb)/100 ml in an elementary school population living in a neighborhood close to the smelter (within 3 km of the plant). The present study, however, has found mean blood lead levels of 11.35 micrograms/100 ml (95% CI = 9.32; 13.82) among a comparable group of children. In addition to blood lead, tooth lead was used to assess exposure among children. Statistically significant differences (p < 0.05) were observed between the geometric mean tooth lead level of 6.44 micrograms Pb/g (n = 13; 95% CI = 3.95; 10.50) in the most contaminated zone and 1.43 micrograms Pb/g (n = 35; 95% CI = 1.11; 1.84) in zones farther away from the point source. Both biomarkers, blood and tooth lead levels, reflect a similar pattern of lead exposure in children. This study has attempted a quantitative assessment of risk factors associated with elevated lead exposure in the Czech Republic. Content of lead in soil, residential distance from the smelter, consumption of locally grown vegetables or fruits, drinking water from local wells, the mother's educational level, cigarette consumption among family members, and the number of children in the family were factors positively related (p < 0.05) to blood lead levels. The resulting blood lead level was found to be inversely proportional to the child's age.ImagesFigure 1.
Rats were experimentally exposed to the chemical factor, inorganic manganese (Mn), and the physical factor, simulated radiation of mobile phone to detect possible interactions, resulting in changes of brain Mn level or other changes. In acute test, significant increase in brain Mn level was observed in rats exposed to both factors as compared to Mn only. Within subchronic 3-months' test such interaction did not appear, but in vivo observation of exposed rats at the end of the test have demonstrated signficant behavioral changes as compared to unexposed rats.
Manganese retention was observed in brains and in several other tissues of female Wistar rats after the intratracheal instillation of an inorganic manganese compound: manganese dioxide. Two categories of rats, younger (180 to 200g) and older (330 to 350g), were divided into a control group, in which animals received vehicle only (0.5 mL physiological saline), and an experimental group, in which rats received a dose of 0.48 mg of Mn/kg body weight (in 0.5 mL saline), twice a week for 3 months, for a total dosage of 11.80 mg of Mn/kg body weight. At the end of the exposure period, manganese retention in selected rat organs, brain, liver, kidney, and lung, was analyzed using atomic absorption spectrophotometry. At the end of the 6-wk or 12-wk manganese dioxide exposure period, analysis of variance of the manganese retention results revealed significant differences between Mn-exposed and unexposed rats in brain, kidney, and lung tissues (p<0.01) for both experimental age categories. Moreover, at the end of the 12-wk exposure period, significant results (p<0.05) between younger and older rats were obtained for both brain and kidneys. In both types of tissue, the manganese retention in the younger group was higher than that in older animals.
Some implications of cooperative potential of metal ions and electromagnetic fields' radiation (EMF) in carcinogenic processes are discussed. It is known that these factors, chemical and physical individually have connections with processes of oxidative stress. Special attention was paid to possible manifestation within the brain. Therefore, the entry of a few potentially neurotoxic metals into the brain is discussed.
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