Allergy and occupational exposure to hydroquinone and to methionine

Respiratory manifestations have been reported after exposure to hydroquinone and to methionine. One hundred and three men in the same chemical plant were divided into three groups according to their exposure and compared by questionnaire, respiratory functional tests with methacholine then salbutamol challenges, and measurements of serum immunoglobulins G and E. Group H included 33 workers exposed to hydroquinone, trimethyl-hydroquinone, and retinene-hydroquinone. Group M included 15 workers exposed to methionine. Group C was a control group of 55 workers. The prevalence of respiratory symptoms was higher in the two exposed groups. Before challenges, pulmonary function values were significantly lower in groups H and M than those in group C. The challenges induced significant variations in the three groups but these variations were less pronounced in group M than in the other groups. The level of immunoglobulin G in group H (m +/- SD = 12.5 gram/liter +/- 2.6) was significantly higher than in group C (10.6 gram/liter +/- 2.4; p less than 0.002). The level of immunoglobulin E in group H (m = 140 IU/l) was also higher in group C (109 IU/l) but this difference was not significant. These findings suggest that exposure to methionine and to hydroquinone and its derivatives induce ventilatory impairment, perhaps by an immunological mechanism.     

Occupational exposure to hairdressing chemicals and immunoglobulin E synthesis

OBJECTIVE: This study assessed the effect of exposure to hairdressing chemicals on total and allergen-specific serum immunoglobulin E (IgE) in hairdressers. METHODS: The study was based on a questionnaire sent to 100 hairdressers (91% responding) and a reference group of 95 office workers (84% responding). The questionnaire sought information on allergy, respiratory symptoms during the past year, work conditions (exposure), and smoking habits. The hairdressers were divided into two groups, one of high exposure and another of low exposure. Total serum IgE and allergen-specific IgE towards the most prevalent airborne allergens were analyzed. RESULTS: The serum levels of total IgE were significantly higher among the highly exposed hairdressers than among the office workers. The prevalence of asthma-like respiratory symptoms during the past year was significantly higher among the highly exposed hairdressers than among the office workers. The total serum IgE level was significantly higher among the hairdressers than among the office workers (101 versus 51 IU/ml blood), but this difference disappeared after adjustment for age, atopy, and smoking. A total of 5.5% of the hairdressers versus none of the office workers had specific serum IgE antibodies towards latex. There were no differences in general allergy (Phadiatop) among the hairdressers and office workers. CONCLUSIONS: Serum levels of total IgE were significantly higher among highly exposed hairdressers than among office workers. The relationship could not be completely explained by such covariables as age, smoking, or sensitization to latex allergens.     

六价铬男性生殖毒性的初步探讨

目的 探讨六价铬的男性生殖毒性,方法 采用职业流行病学调查与相关实验室检查相结合的方法观察铬作业男工精液,精子形态,测定精浆锌,血铬,精浆铬,黄体生成激素（ＬＨ）和促卵泡成熟激素（ＦＳＨ）的改变。结果 铬作业（ＣｒＯ３Ｘ＝０．０１９５ｍｇ／ｍ＾３）男工组精子数（５２．２１±４５．５１）×１０＾９／Ｌ,显低于对照组（８８．９６±７４．８２）×１０＾９／Ｌ,精浆锌（４８１１．８５±１４０１．８８）μ     

Change in the iso-enzyme profiles of urinary N-acetyl-beta-D-glucosoaminidase in workers exposed to mercury

The iso-enzyme profiles of urinary N-acetyl-beta-D-glucosoaminidase (NAG) were studied in the workers from a chloro-alkaline electrolysis plant that had been continuously exposed to elemental mercury. The same workers then had a work break of four months and were later re-exposed to mercury for another five months. The activities of urinary NAG in workers exposed to mercury before and after the work break and in the control group were 2.09 +/- 1.03 IU/L; 0.90 +/- 0.52 IU/L and 1.13 +/- 0.35 IU/L, respectively. The fraction of the dominant A form activity in the total activity, in the workers exposed to mercury after a work break (85.31 +/- 5.32%), was almost equal to the fraction of A in the control group (84.64 +/- 2.75%). The percent fraction of A forms (A and A2) during continuous exposure was almost equal to the sum of the fractions A and A2 in the control group and for exposure after the work break. The fraction of the B form activity in the total activity during exposure to elemental mercury for five months after the work break (7.41 +/- 3.45%) was lower (P < 0.1) than the fraction of the B form in the control group (8.62 +/- 2.19%). The decrease in the fraction of the B form compared with the control group was more significant (P < 0.001) in the case of continuously exposed workers (5.25 +/- 2.55%). Beside the major A and B iso-enzymes of NAG, the A2 form was also isolated, and its fraction in the control group (6.73 +/- 2.15%) was not negligible. For workers exposed to mercury for five months, it was 7.28 +/- 3.52%. It is concluded that mercury affected the increased exocytosis of iso-enzyme A and the inhibition of B iso-enzyme of NAG. The increase in activity of urinary NAG in subjects exposed to mercury was a consequence of the increased excretion of A form. It was established also that the four months work break was sufficient for the repair of renal damages that occurred during continuous exposure, and which were monitored by the activity of NAG. Thus, the effects of mercury seem to have been reversible.     

Lipid peroxidation and antioxidative enzyme activity in erythrocytes of workers occupationally exposed to aluminium

Current research indicates that lipid peroxidation could have a role in aluminium toxicity. The aim of this study was to asses lipid peroxidation and antioxidative enzyme activity in erythrocytes of workers occupationally exposed to aluminium. We investigated a group of 59 workers (Al group) exposed to aluminium fumes (contamination factor F=8.07 to 13.47, national maximal allowed concentration value is 2 mg m-3). The control group (C group) consisted of 75 subjects employed in lime production who had not been occupationally exposed to aluminium or any known toxic substance.Erythrocyte aluminium concentrations were significantly higher in the exposed group than controls [Al group (8.41+/-3.66) microg L-1, C group (5.60+/-0.86) microg L-1, p<0.001]. In the Al group, erythrocyte malondialdehyde concentration was also significantly higher [Al group (189.59+/-81.27) micromol L-1, C group (105.21+/-49.62) micromol L-1, p<0.001] and antioxidative enzyme activity reduced for glucoso-6-phosphate-dehydrogenase [Al group (5.05+/-1.70) IU g-1 Hb, C group (12.53+/-4.12) IU g-1 Hb, p<0.001], glutathione reductase [Al group (1.41+/-0.56) IU g-1 Hb, C group (1.89+/-0.57) IU g-1 Hb, p<0.001], glutathione peroxidase [Al group (12.37+/-5.76) IU g-1 Hb, C group (15.54+/-4.85) IU g-1 Hb, p<0.001], catalase [Al group (116.76+/-26.60) IU g-1 Hb, C group (158.81+/-71.85) IU g-1 Hb, p<0.001] and superoxide dismutase [Al group (1175.8+/-149.9) IU mg-1 Hb, C group (1377.9+/-207.5) IU mg-1 Hb, p<0.001].     

接触二硫化碳男工血清性激素水平及尿代谢物含量分析

为探讨长期接触二硫化碳（ＣＳ２）的粘胶纺丝男工血清性激素及尿２－硫代－噻唑啶－４－羧酸（ＴＴＣＡ）水平,应用放射免疫法测定接触工人血清性激素水平及用高效液相色谱法测定工人班末尿中ＴＴＣＡ含量。以多功能气体红外监测仪定点连续监测车间ＣＳ２浓度为（１４．４０±４．６２）ｍｇ／ｍ３（６．０１～２５．３０ｍｇ／ｍ３）,平均接触工龄为１０．４年。结果显示（１）接触组血清促卵泡激素〔ＦＳＨ：（１０．９４±７．３５）ＩＵ／Ｌ）〕明显高于对照组〔（７．５０±５．０７）ＩＵ／Ｌ〕;催乳素〔ＰＲＬ（５．７２±４．１８）ｎｇ／Ｌ〕则显著低于对照组〔（６．８９±４．６２）ｎｇ／Ｌ〕;血清促黄体激素（ＬＨ）、睾丸酮（Ｔ）等两组间均无统计学显著差异。但随着暴露工龄延长,ＨＬ含量明显下降。班的轮换不影响性激素水平。（２）在该接触浓度下工人班末尿ＴＴＣＡ为（１．０７２±１．０１３）ｍｇ／ｇ肌酐,随尿ＴＴＣＡ排出量增加,血清ＦＳＨ含量明显下降,存在接触－反应关系。本研究表明,现有接触水平对男工内分泌系统功能已造成一定损害。     

Respiratory health effects from occupational exposure to wood dust in sawmills

Spirometric lung functions were recorded for 109 workers (mean age 26.4 +/- 8.2 yr) occupationally exposed (mean exposure 8.9 +/- 7.7 yr) to soft wood dust in local sawmills along with 88 unexposed controls (mean age 28.7 +/- 9.9 yr) belonging to the same socioeconomic status to assess the prevalence of respiratory impairment in the exposed population. The results of the study showed a significantly higher prevalence of overall respiratory impairment in the exposed group even after standardizing for smoking habits (p less than 0.001). The adjusted rate for respiratory impairment in the exposed group was 29.4% as compared to 2.2% observed in the unexposed controls. The pattern of respiratory abnormality observed in the sawmill workers was predominantly the restrictive type (28.4%), indicating lower levels of forced vital capacity (FVC) in the exposed group; while in the control group, there were none with lung restriction The prevalence of airflow limitation, however, was similar in the exposed workers (1.8%) and controls (2.2%), thereby, indicating that bronchial obstruction was independent of wood dust exposure. It is concluded that the dust exposure in sawmills is associated mainly with restrictive type of pulmonary impairment in the exposed workers.     

Asthma in tunnel workers exposed to synthetic resins.

OBJECTIVES: The prevalence of asthma among tunnel workers exposed to synthetic resins was studied by determining airway symptoms, methacholine responsiveness, and lung function. METHODS: Nineteen injection workers were compared with a group of 104 other tunnel workers with similar exposure, except for that to synthetic resins. A questionnaire on respiratory symptoms, smoking habits, use of respiratory protection, and work tasks was used. Lung function was studied using a bellows spirometer. Bronchial reactivity was tested with methacholine. Allergy screening with Phadiatop and radioallergosorbent tests for toluene-diisocyanate-HSA, diphenylmethane-4.4-diisocyanate-HSA, and formaldehyde-HSA (HSA = human serum albumin) were carried out. Methylene diphenyl diisocyanate (MDI) and MDI prepolymer exposure was estimated by filter sampling, and the filters were analyzed by high-performance liquid chromatography. The most common work situations were simulated for an estimation of exposure to isocyanates. RESULTS: The injection workers reported more respiratory symptoms than the reference group, and they had higher prevalences of bronchial hyperresponsiveness (37% versus 14%), asthma (26% versus 1%), and airflow limitation (37% versus 4%). Toluene-diisocyanate-HSA-specific immunoglobulin E antibodies were found in 2 of the 19 injection workers, but in none of the other tunnel workers. By simulation at a worksite, the average exposure to polymerized MDI was estimated to be 5.5-300 microg/m3 during injection work and 18-4300 microg/m3 during short-term exposure, the highest exposure occurring when cured polyurethane was ground. CONCLUSIONS: Exposure to partly decomposed MDI in tunnel work enhances the risk for respiratory symptoms, methacholine hyperresponsiveness, asthma, and airflow limitation.     

Fluoride in workplace air and in urine of workers concentrating fluorspar

The urinary fluoride concentrations of workers exposed to calcium fluoride (CaF2) during fluorspar processing were measured. Personal dust measurement showed that the mean occupational exposure to fluoride for 12 workers in the most dusty environment was 24.3 mg/m3, which is 9.7 times the threshold limit value (TLV) of 2.5 mg/m3. Exposure was below the TLV for the remaining 23 workers. Urinary fluoride concentrations were measured pre- and postshift. The heavily exposed workers had a mean preshift concentration of 3.3 mg/liter (range 1.4-8.5 mg/liter), only slightly higher than the mean of 2.8 mg/liter (range 1.3-4.2 mg/liter) in the workers with fluoride exposure below the TLV. Four of the preshift concentrations exceeded the recommended upper limit of 4 mg/liter. The mean postshift concentration for workers exposed above the TLV was 4.4 mg/liter (range 2.4-7.1 mg/liter) and the difference between pre- and postshift concentrations was significant (p less than 0.05). Only one urinary concentration exceeded the recommended upper limit of 7 mg/liter. There was poor correlation between intensity of environmental exposure to fluorspar and postshift fluoride concentration in the urine. Eighteen workers provided a urine sample 7-14 hr after the end of a shift. The mean fluoride concentration was 4.7 mg/liter (range 2.4-11.7 mg/liter), which exceeded their postshift concentration by 0.2 mg/liter. These results indicate that the low aqueous solubility of fluorspar reduced the biologic availability of the fluoride ion but that this did not prevent excessive fluoride absorption in some workers.     

甲醛对作业工人免疫系统的损伤作用

[目的]探讨甲醛对作业工人免疫系统的影响。[方法]调查分析昆山市存在甲醛职业危害的企业,选择65名甲醛作业工人和非甲醛暴露工人70名为研究对象,采集工人静脉血,经仪器自动分析,测定作业工人血清补体C3、C4及血清免疫球蛋白IgA、IgG、IgM。[结果]18家企业甲醛最高浓度达3.11mg/m3,超标作业点达29.09%。暴露组作业工人血清补体C3（0.99±0.31）、IgM（1.16±0.51）;≥5年组作业工人血清补体C（30.85±0.15）、C4（0.20±0.05）及血清IgA（1.28±0.57）、IgM（0.90±0.35）明显降低,与对照组比较差异有统计学意义（P〈0.01）。[结论]接触甲醛导致作业工人免疫功能抑制。     

Epidemiologic investigation of respiratory effects related to environmental exposure to asbestos inside insulated buildings

The respiratory effects of environmental pollution by asbestos inside university buildings were studied by comparing radiographic, clinical, and functional parameters among three groups of workers with different levels of exposure. Eight hundred and twenty-eight (828) people who worked for at least 15 yr in asbestos-insulated buildings and who were without known occupational exposure to asbestos (environmentally exposed group [EE]) were compared to a group of 252 workers with occupational exposure (occupationally exposed group [OE]), used as positive control; and to a group of 350 people with no known exposure to asbestos (nonexposed group [NE]), within the same university. After adjustment for confounding variables, no differences could be seen between groups EE and NE. Group OE exhibited a higher prevalence of pleural changes and lower lung functions than groups EE and NE.     

Serum immunoglobulin and complement C3 levels in workers exposed to lead.

Serum immunoglobulin and complement C3 levels were measured in workers exposed to lead at a secondary lead refinery and a solder factory. In the first survey, significant correlations were found between blood lead and IgA with a correlation coefficient of 0.296, and between blood lead and IgE with a correlation coefficient of 0.314. No other significant correlations were found among the indicators of lead exposure and humoral immunity. In the second survey, no significant correlations were found between blood lead and IgG and IgA. A significantly higher number of subjects with IgE of more than 400 IU/ml was found in the group with blood lead of more than 60 micrograms/100 g.     

Spirometric function in non-smoking workers exposed to aluminum

BACKGROUND: Exposure to aluminum (Al) causes the onset of respiratory disorders. This study is aimed at providing further information on how occupational exposure to Al affects the respiratory apparatus in healthy non-smokers, with particular attention to respiratory function. METHODS: A group of 50 male shipyard workers who were exposed to Al underwent medical examination, standard chest X-rays and spirometry in accordance with the C.E.C.A. protocol. The data were compared with those of a homogeneous group of controls, all with blood aluminum (AlB) levels below 7.5 ng/ml. Statistical analysis was performed on the following spirometric parameters: vital capacity (VC), forced vital capacity (FVC), maximum forced expiratory volume in 1 s (FEV1), and mean forced expiratory flow during mid-half of FVC (FEF(25-75%)). Environmental Al levels were also measured at the various workstations. RESULTS: Fifty male workers with an average age 31.82 +/- 5.05 years, occupational exposure of 11.81 +/- 3.71 years, presented with average AlB levels of 32.64 +/- 8.69 ng/ml. Environmental monitoring displayed Al levels higher than TLV TWA for all the workstations studied. None of the sample displayed significant pathological conditions. Statistical comparison of the spirometric parameters showed a decrease in the examined values in exposed workers. This decrease was found to be directly proportional to the AlB level. CONCLUSION: The authors conclude that Al affects respiratory function and that limit values should be reassessed.     

Effect of Cr(VI) exposure on sperm quality: human and animal studies

The semen status of male workers occupationally exposed to hexavalent chromium(VI) was investigated. Sperm counts from exposed workers were 47.05+/-2.13 x 10(6)/ml and those from control group 88.96+/-3.40 x 10(6)/ml. Sperm motility decreased from 81.92+/-0.41% for the control group to 69.71+/-0.93% for the exposed workers. The levels of zinc, lactate dehydrogenase (LDH), and lactate dehydrogenase C4 isoenzyme (LDH-x) in seminal plasma for the exposed workers were 1.48+/-0.07 micromol/ml, 1.05+/-0.02 x 10(3) U, and 0.47+/-0.01 x 10(3) U, respectively, which were significantly lower than those of 5.72+/-0.15 micromol/ml, 1.49+/-0.02 x 10(3) U, and 0.78+/-0.15 x 10(3) U for the control group, respectively. Follicle stimulating hormone (FSH) (7.34+/-0.34 x 10(-3) IU/ml) in serum from the exposed workers was significantly higher than that (2.41+/-0.08 x 10(-3) IU/ml) from the control group. On the other hand, there were no significant differences in semen volume, semen liquefaction time, luteinizing hormone (LH) level in serum, and Cr concentration in both serum and seminal plasma between the exposed workers and the control group. Feeding Cr(VI) to rats significantly reduced the epididymal sperm counts from 87.40+/-3.85 x 10(6)/g epididymis in control group to 21.40+/-1.20 x 10(6)/g epididymis at a CrO(3) dose of 10 mg/kg body weight and to 17.48+/-1.04 x 10(6)/g epididymis at a CrO(3) dose of 20 mg/kg body weight. Exposure of rats to Cr(VI) also significantly increased the sperm abnormality from 2.75+/-0.06% in the control group to 6.68+/-0.32% in the exposed group at a CrO(3) dose of 10 mg/kg body and to 7.6+/-0.15% at a CrO(3) dose of 20 mg/kg body weight. In exposed rats, there was visible disruption in germ cell arrangement near the walls of the seminiferous tubules. The diameters of seminiferous tubules in exposed rats were smaller. These results suggest that occupational exposure to chromium(VI) leads to alteration of semen status and may affect the reproductive success of exposed workers.     

Respiratory symptoms and dust exposure among male workers in small-scale wood industries in Tanzania

Few studies have assessed respiratory symptoms and dust exposure levels in small-scale wood industry workers in Africa. We interviewed 546 workers exposed to wood dust and 565 control subjects using a respiratory health questionnaire. Inhalable dust measurements were collected for 106 workers. The dust exposure was high, and job title-based geometric mean exposure levels ranged from 2.9 to 22.8 mg/m3. Prevalence of respiratory symptoms in the previous 12 months was significantly higher in the exposed group compared with the nonexposed office workers. Allergy and sensitivity symptoms were reported regularly in the exposed group with Odds ratios and 95% confidence intervals (CIs) varying from 2.4 (95% CI = 1.8-3.1) for low- and 2.7 (1.8-4.0) for high-exposure groups compared with controls. We conclude that working in the small-scale wood industry in Tanzania is associated with an increased prevalence of respiratory symptoms.     

低浓度混苯暴露与精液质量下降及早早孕丢失的关系

目的：研究低浓度混苯暴露对职业人群精液质量和早早孕丢的伯影响。方法：选择混苯作业工人１２６人、无混苯作业对照６０人,进行生产环境监测和生物学监测;按混苯接地情况,选择暴露组男工７０人,内对照组男工９０人,外对照组男工１３２人,进行精液质量分析;选择暴露组女工４２人,内对照组女工４９人,外对照组女工１１８人,进行尿液人绒毛膜促性腺激素的检测。结果 石化企业混苯暴露以低浓度苯（０．７￣２７．０ｍｇ／     

Prevalence of respiratory disorders among aluminium potroom workers in relation to exposure to fluoride.

In a survey of 370 aluminium potroom workers in western Norway, bronchial responsiveness, lung function, and respiratory symptoms were studied in relation to occupational exposure to air contaminants in the potroom. Increased prevalences of respiratory symptoms, work related asthmatic symptoms, and abnormal lung function were found in subjects exposed to total fluorides above 0.5 mg/m3 when compared with workers exposed to total fluorides at concentrations of less than 0.5 mg/m3. No significant association between bronchial responsiveness and exposure to fluoride was found and the prevalence of respiratory symptoms was independent of the degree of dust exposure. These findings indicate that work related asthmatic symptoms in potroom workers may be related to exposure to fluorides.     

Prevalence of respiratory disorders among aluminium potroom workers in relation to exposure to fluoride.

In a survey of 370 aluminium potroom workers in western Norway, bronchial responsiveness, lung function, and respiratory symptoms were studied in relation to occupational exposure to air contaminants in the potroom. Increased prevalences of respiratory symptoms, work related asthmatic symptoms, and abnormal lung function were found in subjects exposed to total fluorides above 0.5 mg/m3 when compared with workers exposed to total fluorides at concentrations of less than 0.5 mg/m3. No significant association between bronchial responsiveness and exposure to fluoride was found and the prevalence of respiratory symptoms was independent of the degree of dust exposure. These findings indicate that work related asthmatic symptoms in potroom workers may be related to exposure to fluorides.     

Assessment of the permissible exposure level to manganese in workers exposed to manganese dioxide dust.

The prevalence of neuropsychological and respiratory symptoms, lung ventilatory parameters, neurofunctional performances (visual reaction time, eye-hand coordination, hand steadiness, audioverbal short term memory), and several biological parameters (calcium, iron, luteinising hormone (LH), follicle stimulating hormone (FSH), and prolactin concentrations in serum, blood counts, manganese (Mn) concentration in blood and in urine) were examined in a group of workers (n = 92) exposed to MnO2 dust in a dry alkaline battery factory and a matched control group (n = 101). In the battery plant, the current exposure of the workers to airborne Mn was measured with personal samplers and amounted on average (geometric mean) to 215 and 948 micrograms Mn/m3 for respirable and total dust respectively. For each worker, the lifetime integrated exposure to respirable and total airborne Mn dust was also assessed. The geometric means of the Mn concentrations in blood (MnB) and in urine (MnU) were significantly higher in the Mn exposed group than in the control group (MnB 0.81 v 0.68 microgram/100 ml; MnU 0.84 v 0.09 microgram/g creatinine). On an individual basis, MnU and MnB were not related to various external exposure parameters (duration of exposure, current exposure, or lifetime integrated exposure to airborne Mn). On a group basis, a statistically significant association was found between MnU and current Mn concentrations in air. No appreciable difference between the exposed and the control workers was found with regard to the other biological measurements (calcium, LH, FSH, and prolactin in serum). Although the erythropoietic parameters and serum iron concentration were in the normal range for both groups, there was a statistically significant trend towards lower values in the Mn exposed workers. The prevalences of reported neuropsychological and respiratory symptoms, the lung function parameters, and the audioverbal short term memory scores did not differ between the control and exposed groups. The Mn workers, however, performed the other neurofunctional tests (visual reaction time, eye-hand coordination, hand steadiness) less satisfactorily than the control workers. For these tests, the prevalences of abnormal results were related to the lifetime integrated exposure to total and respirable Mn dust. On the basis of logistic regression analysis it may be inferred that an increased risk of peripheral tremor exists when the lifetime integrated exposure to Mn dust exceeds 3575 or 730 micrograms Mn/m3 x year for total and respirable dust respectively. The results clearly support a previous proposal by the authors to decrease the current time weighted average exposure to Mn dust.     

Assessment of the permissible exposure level to manganese in workers exposed to manganese dioxide dust.

The prevalence of neuropsychological and respiratory symptoms, lung ventilatory parameters, neurofunctional performances (visual reaction time, eye-hand coordination, hand steadiness, audioverbal short term memory), and several biological parameters (calcium, iron, luteinising hormone (LH), follicle stimulating hormone (FSH), and prolactin concentrations in serum, blood counts, manganese (Mn) concentration in blood and in urine) were examined in a group of workers (n = 92) exposed to MnO2 dust in a dry alkaline battery factory and a matched control group (n = 101). In the battery plant, the current exposure of the workers to airborne Mn was measured with personal samplers and amounted on average (geometric mean) to 215 and 948 micrograms Mn/m3 for respirable and total dust respectively. For each worker, the lifetime integrated exposure to respirable and total airborne Mn dust was also assessed. The geometric means of the Mn concentrations in blood (MnB) and in urine (MnU) were significantly higher in the Mn exposed group than in the control group (MnB 0.81 v 0.68 microgram/100 ml; MnU 0.84 v 0.09 microgram/g creatinine). On an individual basis, MnU and MnB were not related to various external exposure parameters (duration of exposure, current exposure, or lifetime integrated exposure to airborne Mn). On a group basis, a statistically significant association was found between MnU and current Mn concentrations in air. No appreciable difference between the exposed and the control workers was found with regard to the other biological measurements (calcium, LH, FSH, and prolactin in serum). Although the erythropoietic parameters and serum iron concentration were in the normal range for both groups, there was a statistically significant trend towards lower values in the Mn exposed workers. The prevalences of reported neuropsychological and respiratory symptoms, the lung function parameters, and the audioverbal short term memory scores did not differ between the control and exposed groups. The Mn workers, however, performed the other neurofunctional tests (visual reaction time, eye-hand coordination, hand steadiness) less satisfactorily than the control workers. For these tests, the prevalences of abnormal results were related to the lifetime integrated exposure to total and respirable Mn dust. On the basis of logistic regression analysis it may be inferred that an increased risk of peripheral tremor exists when the lifetime integrated exposure to Mn dust exceeds 3575 or 730 micrograms Mn/m3 x year for total and respirable dust respectively. The results clearly support a previous proposal by the authors to decrease the current time weighted average exposure to Mn dust.