الفهرس 
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Abstract
Workers are often simul bncously or successively exposed to more than one occupational hazard in the work environment such as physical, chemical and biological factors. The combination of these various environmental factors in the work environment may well exert an effect different from that caused by any single exposure alone; and may be of independent, additive, synergistic, and/or antagonistic nature. The study of combined exposure has received more concern in recent However, epidemiological occupational studies on specific exposu~e years. combinations are limited. One example is the combined exposure to lead and L~2 for which no data are available In literature; although a great body of literature is available describing the effects on health of exposure to either lead or C52’ including effects on nervous, cardiovascular, gastrointestinal, haematopoietic, renal systems; as well as changes in certain biochemical parameters such as serum lipids, proteins, and some enzymes. . The present study was conducted to investigate the types of combined effects induced in workers exposed to lead and C52. The study was conduct ed in two plants: the first manufactures artificial fibers (rayon) and is ’located in Kafr EI-Dawar (Behera Governorate), and the second manufactures lead batteries and is located in Victoria district in Alexandria. Environmental assessments of C52’ H25 and lead were conducted in the atmosphere of the work environments of the studied plants. A workers’ sample comprising 118 rayon spinners, 90 lead welders and 51 control sub jects from the rayon plant, and a sample of 96 lead exposed workers and 43 control subjects from the lead batteries plant were randomly selected for the study. Each worker and control subject was interviewed for his personal, social, occupational and medical histories with reference to smoking habits and drug intake with emphasis on the family history of cardiovascular diseases, past history of neurological, cardiovascular, endemic and infectious diseases. ~his was followed by a thorough clinical examination of the cardiovascular, respiratory, gastrointestinal and ner vous systems and skin and eyes, electrocardiographic investigation, and measurement of pulmonary function including FEVl.O and FVC. samples were obtained from each subject for the determination serum Vein blood cholesterol, serum triglycerides and the assessment of the activity of . monoamine oxidase enzyme, as well as the analysis of lead in red blood cells; urine samples were also collected for the modified iodine azide assessment. In order to compare the effects of combined exposure relative to the effects of single exposure to either lead or C52’ workers of single exposure to either C52 or lead who had levels of urinary iodine azide (af~er shift) or of lead in RBCs within the ranges of the mean levels ~2 standard deviations Df the workers’ groups exposed to both lead and CS2 (combined exposure) were selected for the comparison. Two groups were formed: group A included workers exposed to C52 only (n = 65) and those exposed to C52 and lead (n = 32) selected on basis of the levels of urinary iodine azide test after shift (2.1 - 48.9 mg I2/mg creatinine); group B included workers exposed to lead only (n = 87) and those exposed to lead and C52 (n = 90) selected on basis of the levels of lead in RBCs (11.8 - 168.2 ppm). The mean levels of airborne lead in all locations in the two studied plants were within TLV, while the mean atmospheric levels of C52 and H2S in all studied operations in the rayon plant were much higher than their TLVs. The prevalence of health and neuro-psychological complaints, clinical signs of nervous system, cardiovascular changes, pulmonary function changes, decrease in level of cholesterol and increase in level of triglycerides were the highest in workers exposed to CS2 only or in combination with lead and the lowest in those exposed to lead only. . Flatulence, burning sensation and pain in eyes, and pain in hands or feet were significantly higher complaints among the workers with combined exposure than those exposed to lead only, while none of the complaints were significantly higher among those exposed to CS2 only. However, palpitation, angina pectoris, intermittent claudication, chronic cough, epigastric pain, heart burn, flatulence, contact dermatitis, burn ing sensation and pain in eyes, muscle weakness, spells of loss of body 1 balance, spells of dizziness, spells of nervousness and irritability, . spells of entroversion, lack of concentration, and impotence were higher and significant complaints among workers exposed to CS2 only in comparison \ to those with the crnnbined exposure. In the meantime, angina pectoris, epigastric pain, heart burn, abdominal pain or colic, tender abdomen, contact dermatitis, and night mqres were the onlY3ignificantly higher complaints among workers exposed to lead only in comparison to the workers of combined exposure to lead and CS2’ The significantly higher neurological signs among the workers with the combined exposure in comparison to those exposed to C52 only were the decreased deep reflexes (knee, ankle, triceps and biceps), while, the absence of knee reflex was the only significant deep reflex among the workers of the combined exposure than those exposed to lead only. The increased in heart rate and sinus tachycardia represent the 2nly significantly higher electrocardiographic changes among the workers with combined exposure to lead andC52 than those exposed to lead only, while the mean systolic blood pressure and diastolic blood pressure were significantly higher among the workers exposed to lead only than those with the combined exposure. No signifJcant differences in blood pressure and electrocardiographic findings were found between the workers exposed to C52 only and those with the combined exposure. Most of the pulmonary function measurements were significantly lower among workers exposed to C52 only than those with the combined. e~posure to C52 and lead; while FEVl.O pred. was the only significantly lower parameter among the workers with the combined exposure than those exposed to lead only. The levels of cholesterol were significantly higher among workers exposed to C52 only or lead only than those with the combined exposure; while the levels of triglycerides were insignificantly higher among the workers with the combined exposure than those with the single exposure to either C52 or lead. . , The activity of MAO enzyme significantly decreased among workers exposed to lead only than those with the combined exposure; while it slightly decreased among workers of the combined exposure relative to those of the single exposure to C52. . The role of some risk factors to precipitate ischaemic heart disease was studied, and included: age, smoking habit, shift work, family history of cardiovascular diseases, percent standard body weight, systolic blood pressure, diastolic blood pressure, serum cholesterol, and serum triglycerides. The three workers’ exposure groups showed significantly . higher rates of some of these risk factors, which might partially explain the increase in the prevalence rate of ischaemic heart changes among the exposed workers than among control subjects. However, data presented in the present and previous studies indicate some type of correlation between the occupational exposure to C52 and the precipitation of the ischaemic heart disease. It has been concluded that the combined exposure to C52 and lead has an additive effect on the heart rate, reduction in the level of chol esterol and increase in the level of triglycerides, while it has synergistic effect on prevalence of sinus tachycardia; other investigated signs, symptoms or tests were independent in their response to exposure of C52 and lead.