الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
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Abstract
Prolonged exposure to low concentrations of chemical substances is by far the most common risk to which workers are exposed today. In developing countries like Egypt, a great proportion of the working population is involved in small and medium size industries. Therefore, it has been a grea t need for identifying some biochemical changes accompanying such exposures which can be useful for the biomonitoring of the early effects on worker’s health. The present work has been carried out in a trial to find the relationship between exposure to some pollutants as styrene, aniline, benzidine, perchloroethylene and diesel exhausts and the specific biochemical parameters related to the early precancer investigations. These pollutants are electrophilic chemical compounds except perchloroethylene. Electrophilic compounds include most mutagenic and carcinogenic substances and can cause severe tissue damage. - . The metabolites of styrene, benzidine and diesel engine exhaust are known to bind to protein macromolecule wcalently giving rise to chemical lesions. The assay of thiocompounds in urine allows a useful biological monitoring tool for the assessment of exposure to electrophilic compounds. concerning cancer monitoring, the activity of urinary esterases was recommended as a screening test for some types of cancer. Moreover J ribonuclease enzyme is capable of degrading nucleic acids) This enzYme has become of increased interest as a biochemical marker because of its alteration in the cancer and pre cancer state in a variety of species. The present study comprises a total number of workers (n= 255), occupationally exposed to five different pollutants in small and medium size industries. These pollutants are styrene . 70 workers from Plastics and . Battery Egyptian Company; aniline: 60 workers, benzidine: 25 workers from Kafr El-Dawar Chemical and Dyeing Company; diesel engine exhaust 70 workers from Smoha bus garage and perchloroethylene 30, workers from dry cleaning indus try. Comparison groups were also included in the present study. They were selected from the administrative departments of the some factories. Their total number is 226. Laboratory investigations included: Determination of indices of exposure as mandelic acid, Met Hb, benzidine in urine, Co Hb and Trichlorocompounds in urine for workers exposed to styrene, aniline, benzidine, diesel exhaust and perchloroethylene respectively. Determination of thioether levels, non specific D< extrases, ribonuclease for all groups of pollutants. The determination of the indices of exposure revealed that workers exposed to styrene had higher values of mandelic acid in urine, workers exposed to benzidine had detectable amounts of benzidine in urine and workers exposed to aniline had higher levels of Met Hb. However, the levels of CoHb among workers exposed to co in diesel exhausts did not show positive results. Concerning to exposure to PCE the present study did not find positive results in the levels of trichloro compounds in urine, probably due to limited metabolism of PCE. Styrene, aniline, benzidine and diesel engine exhausts are considered as electrophilic compounds as they are metabolized via the formation of electrophilic intermediate They are usually inactivated by reacting with glutathione or other SH-bearing molecules as a detoxification mechanism. The conjugate appear in urine in the form of thioether products. The determination of thioether in urine revealed that workers are actually exposed to electrophilic chemical compounds except for workers in perchloroethylene which is not electrophilic. In the present study, the activity of RNase enzYme was found to be enhanced among workers exposed to . styrene, and diesel engine exhaust but not among workers exposed to perchloroethylene and aniline. The pqsitive resul ts might be due to the fact that the metabolites of ~tyrene, benzidine and diesel exhausts are known to bind to protein macromolecules giving rise to chemical lesions with the .production of excess RNA particles. Therefore, enhanced RNase activity is expected. It was also noted that the .present study failed to detect any significant variation in the mean levels of esterases activity among the different groups of exposed workers. This excludes the possibility of using this enzyme in the early detection of carcinogenici ty. The following might be recommended * Determination and strict application of TLV in medium and small size industries. ’/I During the periodic medical examination especially importance must be given to the biochemical tests. ’/I In case of exposure to electrophilic chemicals, thioether levels must be determined as a detector of the severity of exposure.^leng