الفهرس 
AcknowledgmentOnly 14 pages are availabe for public view
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Abstract
During the last decades a great number of chemical substances have been introduced into the .environment due to rapid industrial development. Most of these substances are potentially toxic and many of them have genotoxic effects. There is a growing concern about the possible mutagenic and carcinogenic effect of mutagenic agents in human population exposed occupationally, accidentally or by life style. Some occupations may have influence on the somatic andgenninal cells of persons involved in such jobs. Occupational and environmental pollution have become a major concern of community, specially the potential for exposure of genotoxic substances. The problem arises because some of these pollutants are carcmogens and mutagens with the capacity to affect the structural integrity of DNA. Genetic monitoring of genotoxins is in a rapid phase of development. Currently, there is increasing interest in the use of molecular markers such as DNA single strand breaks and sister chromatid exchanges for human monitoring. However, both SCEs nd DNASSB induction in peripheral blood lymphocytes are two genotoxic markers of early biological effect that have been used for monitor human population exposed to low concentration of environmental and occupational pollutants. The introduction of genetic monitoring in the field of occupational health have been employed to assess the risk of human population to genetic damage caused by several occupational and environmental agents. Genetic monitoring involves periodic examination of cells, usually in blood or urine from employees to assess chromosomal and other genetic damage due to exposure in the work-place. The results can be used for early identification. The results can be used for early identification of genetic exposures in population. Special emphasis is given to the role of heavy metals as mutagens or carcinogens as they are wide spread and persist in the environment. A large number of metals as mercury, lead and chromium has been reported to be carcinogenic and/or mutagenic to experimental animals as well as human populations. Their action on genetic material is not restricted to the direct mutagenic and carcinogenic effect, but their complex interaction with other mutagens, carcinogens, develops their co- or antimutagenic effects. Smoking represents one of the most wide spread activities, that can result in exposure to high level of carcinogens from which humans are at risk. Moreover, it can modify the effect of occupational chemical exposures The present study aimed to identify the possible effect of occupational exposure to lead, mercury and chromium on DNA single strand breaks and sister chromatid exchanges, and to deduce a possible relationship between DNA single strand breaks, sister chromatid exchanges, smoking and occupational exposure to some heavy metals. This study includes a total number of 150 workers, showing the same demographic characteristic like, age, educational status, socioeconomic status, ... etc. This represents 3 groups of the following exposures: a) Workers exposed to lead in storage battery plant (n = 50) selected randomly from the” Egyptian Plastics and Electricity Company in Alexandria. b) Workers exposed to mercury in a fluorescent lamp manufacturing unit (n = 50) selected randomly from EI-Nasr Company for Electronics Devices (Phillips) in Alexandria city. c) Workers exposed to chromium in tanneries units (n = 50) selected randomly from EI-Nasr Tanneries Company in Alexandria. Also, a matched comparison group of Cl 00) subjects was selected from Edfina Company for Food Preservation. They had no history of occupational to these pollutants, and showing the same exposure demographic characteristics as the exposed workers. The following tests have been carried out: . Detennination of the indices of exposure (B-Pb,B-Hg and P-Cr). . Somatic cell mutation and genotoxicity analysis (SCEs and DNASSB). Exposed workers and control subjects have been classified into smokers and non-smokers. Descriptive and non-parametric statistics of data have been carried out. Results were presented as follows: a) Effect of occupational exposure to Pb, fIg, and Cr on DNASSB, SCEs. b) Effect of smoking. The determination of indices of exposure in the present study revealed that B-Pb, B-Hg and P-Cr levels were significantly increased among exposed workers when they were compared with that of control subjects. Somatic cell genotoxicity results revealed that occupational exposure to Pb, Hg and Cr resulted in somatic mutations and genotoxic effect among exposed workers. The levels of SCEs and DNASSB frequencies were found to be higher among exposed workers than control subjects. Some positive significant correlations have been deduced: SCEs and DNASSB frequencies were fOlmd to correlate significantly with each of: age, duration of exposure, smoking index and the biological indices of exposure, i.e., B-Pb, B-Hg and P-Cr among exposed workers as well as among control subjects. Also SCEs were found to correlate significantly and positively with DNASSB among exposed workers as well as control subjects. When smokers have been compared to non-smokers, those exposed to Pb, Hg and Cr did not show significant variations concerning the SCEs and DNASSB. However, among control subjects, significantly higher levels of SCEs and DNASSB were found among smokers controls subjects. Although, the value of smoking index did not differ significantly between workers exposed to mercury, lead and chromium and their control subjects, it correlates positively and significantly with SCEs and DNASSB, among exposed workers and control subjects respectively. These results are going with other research studies. However, the importance of the present study lies in the fact that it proved an effect of occupational exposure to heavy metals as lead, mercury and chromium on somatic cell genotoxicity parameters. Also, the confounding effect of smoking is very pronounced here. Therefore, the iDtroduction of one or more somatic cell genotoxicity tests during preliminary and periodic medical examination is recommended as a preventiye measures.^leng