Occupational exposure to UV light and mortality from multiple sclerosis.

BACKGROUND: The etiology of multiple sclerosis (MS) is largely unknown; low exposure to ultraviolet (UV) light has been a suggested risk factor. The aim of this study was to investigate whether occupational exposure to UV light reduces the risk of death from MS. METHODS: The cohort was based on all individuals in the Swedish census in 1980. All MS-related deaths were identified in the national registry of causes of death. A job-exposure matrix was developed to classify the occupational exposure to UV light. RESULTS: MS was recorded as a cause of the death for 839 individuals. The risk of MS-related death decreased with increasing occupational exposure to UV light. The relative risk adjusted for age, sex, and socioeconomic status was 0.48 (95% CI 0.28-0.80) in the high-exposure group and 0.88 (95% CI 0.73-1.06) in the intermediate-exposure group. CONCLUSIONS: Occupational exposure to UV light was associated with a reduced risk of MS. Our findings are corroborated by previous observations that UV light has a preventive role in the development of MS, although the possibility of reversed causality cannot be completely ruled out.

Mortality, morbidity and occupational exposure to airway-irritating agents among men with a respiratory diagnosis in adolescence.

OBJECTIVES: To examine the influence of an airway diagnosis in adolescence on future health and occupation in Swedish men. METHODS: Data were collected from the linkage of four Swedish national registers: the Military Service Conscription Register, the Population and Housing Censuses, the Inpatient Care Register and the National Cause of Death Register. A job-exposure matrix for airway-irritating substances was developed for application on the conscription cohort. The cohort included 49 321 Swedish men born 1949-51. Three groups-(1) healthy, (2) asthmatics (mild and severe asthma) and (3) subjects with allergic rhinitis without concurrent asthma-were identified at conscription and analysed for mortality, in-patient care and strategies for choice of occupation with emphasis on airway-irritating job exposure. Analyses were adjusted for smoking and childhood socioeconomic position. RESULTS: The prevalence of total asthma was 1.8%, severe asthma 0.45% and allergic rhinitis 2.7%. Mortality for all causes was significantly higher in total asthma, hazard ratio (HR) 1.49 (95% CI 1.00 to 2.23), and lower in allergic rhinitis, HR 0.52 (95% CI 0.30 to 0.91). Asthma was a risk factor for inpatient care while allergic rhinitis was associated with less in-patient care (odds ratio (OR) for total asthma 1.16 (95% CI 1.00 to 1.34), severe asthma 1.38 (95% CI 1.04 to 1.85), allergic rhinitis 0.92 (95% CI 0.82 to 1.03)). Those with asthma tended to avoid jobs with a high probability for airway-irritating exposure (OR 0.88, 95% CI 0.71 to 1.09), but not to the same extent as subjects with allergic rhinitis (OR 0.58, 95% CI 0.47 to 0.70) (ORs from 1990). CONCLUSION: Subjects with asthma did not change their exposure situation to the same extent as subjects with allergic rhinitis. Further, asthmatics had an increased risk for morbidity and mortality compared to healthy subjects and subjects with allergic rhinitis.

Parkinson's disease and other basal ganglia or movement disorders in a large nationwide cohort of Swedish welders.

INTRODUCTION: Although it has been hypothesised that metal welding and flame cutting are associated with an increased risk for Parkinson's disease due to manganese released in the welding fume, few rigorous cohort studies have evaluated this risk. METHODS: The authors examined the relation between employment as a welder and all basal ganglia and movement disorders (ICD-10, G20-26) in Sweden using nationwide and population based registers. All men recorded as welders or flame cutters (n = 49,488) in the 1960 or 1970 Swedish National Census were identified and their rates of specific basal ganglia and movement disorders between 1964 and 2003 were compared with those in an age and geographical area matched general population comparison cohort of gainfully employed men (n = 489,572). RESULTS: The overall rate for basal ganglia and movement disorders combined was similar for the welders and flame cutters compared with the general population (adjusted rate ratio (aRR) = 0.91 (95% CI 0.81 to 1.01). Similarly, the rate ratio for PD was 0.89 (95% CI 0.79 to 0.99). Adjusted rate ratios for other individual basal ganglia and movement disorders were also not significantly increased or decreased. Further analyses of Parkinson's disease by attained age, time period of follow up, geographical area of residency, and educational level revealed no significant differences between the welders and the general population. Rates for Parkinson's disease among welders in shipyards, where exposures to welding fumes are higher, were also similar to the general population (aRR = 0.95; 95% CI 0.70 to 1.28). CONCLUSION: This nationwide record linkage study offers no support for a relation between welding and Parkinson's disease or any other specific basal ganglia and movement disorders.

Paternal occupational exposures and childhood cancer.

The objective of the study described here was to test the hypothesis that paternal occupational exposure near conception increases the risk of cancer in the offspring. We conducted a cohort study based on a population of 235,635 children born shortly after two different censuses in Sweden. The children were followed from birth to 14 years, and cases of cancer were identified in the Swedish Cancer Registry. Occupational hygienists assessed the probability of exposure to different agents in each combination of the father's industry and occupation as reported in the censuses. We also analyzed individual job titles. We compared the cancer incidence among children of exposed fathers to that among children of unexposed fathers using Cox proportional hazards modeling. The main findings were an increased risk of nervous system tumors related to paternal occupational exposure to pesticides [relative risk (RR) = 2.36; 95% confidence interval (CI), 1.27-4.39] and work as a painter (RR = 3.65; 95% CI, 1.71-7.80), and an increased risk of leukemia related to wood work by fathers (RR = 2.18; 95% CI, 1.26-3.78). We found no associations between childhood leukemia and paternal exposure to pesticides or paint. Our results support previous findings of an increased risk of childhood brain tumors and leukemia associated with certain paternal occupational exposures. Some findings in previous studies were not confirmed in this study.

Further studies on the erythrocyte uptake of lead in vitro in amyotrophic lateral sclerosis (ALS) patients and controls. Abnormal erythrocyte fragility in ALS.

Following our earlier observations on increased plasma concentrations of lead in amyotrophic lateral sclerosis (ALS), the erythrocyte uptake of lead from plasma has been studied in vitro. Whole-blood from ALS patients and controls was incubated after the addition of lead (0.6 mumol/l whole-blood) and plasma lead concentrations were repeatedly determined. Incubation was continued until haemolysis developed. Fairly stable plasma lead concentrations were established at, on the average, 0.5-0.6 mumol/l after 10-30 min and persisted throughout the incubation with no significant difference between ALS- and control samples. Unexpectedly, it was also observed that haemolysis occurred significantly earlier in the ALS- than in the control samples. Plateau levels in plasma lead concentration of the same order as in the present experiments have been observed both in ALS- and control samples in previous experiments with the same technique, where the lead dose added was twice as high, and these plateau levels were about 10 times higher than those observed in vivo in ALS patients and controls. It is therefore suggested that the final plasma lead concentrations in vivo is established by factors other than the erythrocyte uptake and it is improbable that the differences between ALS patients and controls in plasma lead concentration are associated with differences in the degree of lead uptake by the red cells. The increased plasma lead concentrations in ALS patients may instead be caused by increased fragility of the erythrocytes, as manifested by the earlier occurrence of haemolysis in the present experiments. The observation of increased red cell fragility is, however, also of interest as a possible manifestation of a generalized membrane defect.

Abnormal distribution of lead in amyotrophic lateral sclerosis--reestimation of lead in the cerebrospinal fluid.

The lead concentration in CSF was determined by flameless atomic absorption spectrophotometry in 16 ALS patients and 22 control cases. The mean values were 0.69 +/- 0.55 (ALS) and 0.41 +/- 0.37 (controls), P < 0.01. This confirms our earlier findings of raised CSF lead levels in ALS but the present values are lower than previously reported for both ALS patients and controls.

Blood lead determination by flameless atomic absorption spectroscopy.

A simple procedure for flameless atomic absorption analysis of lead in blood is described. It is based on the use of a temperature-controlled heating unit, which, with a photodiode, measures and, by electronic feedback, controls the temperature of the carbon rod. Examination of the influence of various heating has been made. Blood samples with heparin were diluted with Triton X-100, HNO3 added, and 2 microliter of the mixture analysed. Automatic background correction was used. Signals were evaluated by an electronic facility which gives integrated as well as peak height values. The method appears to be accurate and reproducible. The C.V. was, on average, 4%.

Occupational magnetic field exposure among women in Stockholm County, Sweden.

BACKGROUND: Most epidemiological studies on adverse health effects among women in relation to occupational magnetic field exposure have been based on information about men's exposure. AIMS: To create a job-exposure matrix for occupational exposure to extremely low frequency magnetic fields among women. METHODS AND RESULTS: Measurements were performed using personal magnetic field meters (Emdex Lite) carried by the subjects for 24 hours on a normal workday. Subjects were volunteer women working in the occupations identified as common among women in Stockholm County based on the 1980 census. A total of 471 measurements were made in 49 different occupations, with a minimum of 5 and a maximum of 24 measurements in each occupation. The included occupations cover about 85% of the female population gainfully employed in 1980. Parameters representing average and peak magnetic field exposures, temporal change in the exposure, and proportion of time spent above certain exposure levels were calculated both for the workday and for the total 24 hour period grouped by occupational titles. The occupations with higher than average exposure were cashiers, working proprietors in retail trade, air stewardesses, dental nurses, cooks, post-office clerks and kitchen maids. CONCLUSIONS: This new job-exposure matrix substantially increases the knowledge about magnetic field exposure among women and can be used for exposure assessment in future studies.

Cytogenetic effects in rotogravure printers exposed to toluene (and benzene).

Comparing 21 rotogravure printers exposed to toluene (medians: time-weighted air level 150 mg/m3, blood toluene 1.6 mumole/l) and 21 unexposed controls (median blood toluene less than or equal to 0.01 mumole/l) there was a significant increase in the frequency of micronuclei (MN) in pokeweed mitogen (PWM)-stimulated peripheral blood lymphocytes in the printers, as compared to the controls (2.8% vs. 1.5%; p = 0.03; all p adjusted for age and smoking). The frequency of small MN (size ratio MN/main nucleus less than or equal to 0.03) in PWM-stimulated lymphocytes was associated with the exposure (1% vs. 0.3%; p = 0.05). Furthermore, among the exposed subjects there was an association between blood toluene and small MN (0.17% per mumole/l; p = 0.0005). Small MN in phytohemagglutinin (PHA) cultures displayed no association with any exposure parameter. However, in the printers, an estimated cumulative exposure index was weakly correlated with the frequency of total MN in PHA-stimulated cells (0.00003% per mg/m3 x year; p = 0.07). Among the printers, chromosomal breaks in PHA-stimulated cells were associated with the duration of earlier benzene exposure (0.03% per year; p = 0.01). The results of this study strongly indicate that toluene causes a clastogenic effect on the B-cells even at low exposure levels. Further, earlier benzene exposure seems to have caused chromosomal breaks in T-cells.

Direct determination of chromium in urine by electrothermal atomic absorption spectrometry.

A simple, direct method for the determination of chromium levels in urine is described, electrothermal atomic absorption spectrometry having been used after the urine samples had been acidified. The optimal conditions at the ashing and atomization stages was determined. The detection limit of this method is 5 nmol/1, and the coefficient of variation (within day) is about 3% in the concentration range 20--400 nmol/1. Use of a low temperature asher with electrically excited oxygen before analysis gave results similar to those of the direct procedure. Good correlation was obtained from two other laboratories using different instruments and pretreatments.

Neuropsychiatric function of housepainters with previous long-term heavy exposure to organic solvents.

Neuropsychiatric effects were examined among 206 men, of whom 135 had been house painters and 71 had been house carpenters, affiliated with their respective trade unions for at least 10 years before 1970. Their lifetime organic solvent exposure was evaluated through the aid of an interview. Relevant potential confounding factors were accounted for in the statistical analysis. Neuropsychiatric symptoms compatible with chronic toxic encephalopathy were more common among the painters than among the carpenters, and these symptoms became increasingly prevalent with increasing cumulative solvent exposure. On only one of 12 psychometric tests, block design, did the painters perform worse than the carpenters, and in this test the painters' performance deteriorated with increasing cumulative exposure. For the majority of the psychometric tests, and for the coordination tests, there were no differences between the painters and carpenters, but the painters with "low" exposure tended to show better, and "heavily" exposed painters worse, results than the carpenters. The 52 painters with the heaviest cumulative exposures and 45 carpenters were examined for psychiatric diagnosis according to DSM-III, with electroencephalography and auditory evoked potential, P-300. Three painters and two carpenters had diagnoses compatible with an organic mental disorder. There were no overall differences between the painters and carpenters, either for the visually examined electroencephalograms or the P-300 latencies. The excess of neuropsychiatric symptoms among the painters was probably causally linked to solvent exposure. However, these symptoms seemed only rarely, if ever, serious enough to entail a psychiatric diagnosis. Concerning other outcomes, the investigation may not lead to a determination of whether the exposure-response relationship among the painters, with no difference between the entire group of painters and carpenters, is caused by solvent exposure or by selection factors within the group of painters.

Urinary excretion of o-cresol and hippuric acid after toluene exposure in rotogravure printing.

In 62 male rotogravure printers, the time-weighted average (TWA) toluene exposure during one workweek ranged from 8 to 496 mg/m3 (median 96). Post-shift urinary excretion of hippuric acid showed a poor correlation with the air toluene concentration. Level of o-cresol excretion ranged from 0.08 to 2.37 mmol/mol creatinine and was associated with the exposure (rS = 0.57, P less than 0.0001), although the variation was considerable. However, this metabolite was significantly influenced by smoking habits, both in the workers (0.34 vs 0.10 mmol/mol creatinine after adjustment to zero exposure for the smokers and non-smokers, respectively; P = 0.03) and in 21 unexposed controls (0.18 vs 0.06 mmol/mol creatinine; P = 0.002). The excretion of these metabolites was followed during vacation, when the workers were unexposed. The shared one-compartment half-time was 44 h (+/- SE 30, 82). After 2-4 weeks of vacation, the concentration of o-cresol was significantly higher for the smokers than the non-smokers (0.14 vs 0.06 mmol/mol creatinine; P = 0.02). No smoking-associated difference was found for the urinary hippuric acid concentration. However, there was an association between alcohol consumption and hippuric acid excretion (P = 0.03); no such difference was shown for o-cresol. These results demonstrate that hippuric acid excretion is unsuitable for biological monitoring of toluene exposure when the exposure level is below 200 mg/m3. Also, in spite of the favourable excretion kinetics, the impact of smoking and the large interindividual variation warrant the same conclusion for o-cresol as a means of monitoring low level exposure in an individual worker.

Toluene in venous blood during and after work in rotogravure printing.

Toluene exposure was studied in 62 male rotogravure printers, employed in three plants. The exposure level as measured by personal sampling during a week ranged from 8 to 1080 mg/m3 (median 96). The concentration of toluene in venous blood sampled directly after work correlated significantly with the time-weighted average (TWA) for toluene in air during the preceding workshift (n = 57, Spearman's r = 0.84, P less than 0.00001). The post-shift toluene level in venous blood is usable for biological monitoring of exposure. An air level of 100 mg/m3 corresponds to an average blood toluene level of 2.9 mumol/l; an air level of 300 mg/m3 to 8.2 mumol/l. The elimination of toluene is slow. Thus, toluene was detected in most Monday pre-shift blood samples and the levels increased statistically significantly during the work week (median 0.21 versus 0.42 mumol/l, P less than 0.0001). The toluene level in venous blood sampled directly before work on Thursday/Friday was found to be a function of the estimated mean exposure during the work week. In a multiple linear regression analysis, the mean exposure during the week was a good predictor for the concentration of toluene in venous blood before work at the end of the week (n = 52, r = 0.71). Thus, pre-shift blood values at the end of the week can be used as a biological index for the weekly exposure, when the variation of the ambient toluene concentration is known. The slow decrease of toluene in venous blood was followed in six workers for two weeks after cessation of exposure.(ABSTRACT TRUNCATED AT 250 WORDS)

Neurasthenic complaints and psychometric function of toluene-exposed rotogravure printers.

In 1985, 30 rotogravure printers exposed to toluene for 4-43 years (median 29) were examined by means of interviews and psychometric testing. They were 33-61 years of age (mean 50). Comparisons were made with a reference group of 72 men aged 27-69 (mean 47). The referents had never been exposed to solvents and were all in good health. The printers were employed by two Swedish companies. The mean exposure levels were 43 and 157 mg/m3 of toluene, respectively, at the two printing shops. Before 1980 the exposure levels had exceeded 300 mg/m3. On Monday mornings, before psychometric testing at the department of occupational medicine, toluene was measured in venous blood samples from most of the exposed subjects. A high proportion of the printers reported fatigue (60%), recent short-term memory problems (60%), concentration difficulties (40%), mood lability (27%), and other neurasthenic symptoms. In the psychometric tests their performance was poorer than the reference group's in most of the tests applied. Even performance on the synonyms test, usually considered resistant to mild brain affliction, was worse in the group of printers. Adjusting for this difference in the group comparisons reduced the group differences substantially. Alcohol consumption above 200 g/week was found to reduce the subjects' psychometric function more than toluene exposure. The printers' sum of neurasthenic complaints correlated negatively with their score in several tests. Exposure variables showed only weak associations with test results. Blood toluene levels were positively correlated with scores in spatial tests. The direction of the correlations suggests that the influence of acute pharmacologic effects is undetectable on Monday mornings before work. In conclusion, we found that exposure to toluene at levels below 157 mg/m3 following long-term exposure did induce neurasthenic problems and might reduce psychometric test performance.

Urinary proteins in occupational exposure to chemicals and in diseases.

Isoelectric focusing in thin-layer polyacrylamide gel is a method with high resolving power, e.g. for urinary proteins. Therefore more information can be obtained with this method than with ordinary electrophoresis. The present version of the method has a high capacity and allows study of up to 25 samples in parallel on each gel. Only a little more than one hour is required for separation. A sensitive staining procedure is used which allows detection of as little as 0.1 mug of protein in each zone. When effects on the kidney are present more than 20 different protein zones can sometimes be separated. Evaluation is made by densitometry as well as by comparison and classification of patterns. Urine samples have been studied from workers with varying exposure to cadmium lead and various chlorinated hydrocarbons, and patients with glomerulonephritis, pyelonephritis, nephrosis and mixed tubular and glomerular diseases. Typical tubular patterns, i.e. as developed in association with cadmium exposure were characterized by elevated excretion of beta1-microglobulin. Other types of kidney malfunction showed different features.

Elimination of toluene from venous blood and adipose tissue after occupational exposure.

In a group of 37 rotogravure printers a close correlation (rs = 0.78) was found between the time weighted toluene exposure during a five day working week (range 8-416 mg/m3, median 75) and the concentration of toluene in subcutaneous adipose tissue (range 1.1-20.7 mg/kg, median 3.8). After exposure ceased, the elimination of toluene was followed up in 11 subjects. The toluene concentration in venous blood decreased non-linearly and the elimination curves contained at least three exponential components. The first two had median estimated half times of nine minutes and two hours respectively. The third component, with a median half time of 90 hours, reflected the decline in adipose tissue, which had a median half time of 79 hours (range 44-178). The study showed protracted endogenous toluene exposure from adipose tissue depots long after the end of exogenous exposure. The observations also suggest that the blood toluene concentrations on Monday mornings might be used as an index of the exposure in the previous week.

Glioma and occupational exposure in Sweden, a case-control study.

OBJECTIVES: The aim of the study was to analyse whether any job titles, industrial codes, and certain occupational exposures were associated with an increased risk of glioma. METHODS: A population based case-control study of incident primary brain tumours in adults was carried out in Uppsala, Sweden in the period 1987-90. The study included 192 cases of glioma and 192 matched controls. It also included cases with other tumours of the central nervous system with matched controls. Information from all 343 controls was used in this study. Information was collected by means of a questionnaire that was sent to all subjects. An occupational hygienist reviewed the questionnaires for self reported exposures to substances and assessed whether these reported exposures were plausible or not in the corresponding occupation. RESULTS: The kappa coefficient for those classified by the two methods ranged between 0.46 and 0.88, and they were almost the same for cases and controls. For men exposed to solvents a relative risk (RR) of 2.6 (95% CI 1.3 to 5.2) was found. For men exposed to pesticides the RR was 1.8 (95% CI 0.6 to 5.1), and for plastic materials the RR was 3.6 (95% CI 1.0 to 12.4). For men employed in forestry and logging the RR was 2.2 (95% CI 0.9 to 5.3) and in basic metal industries 2.0 (95% CI 1.0 to 4.0). CONCLUSION: An increased risk of glioma was associated with use of solvents, pesticides, and plastic materials but this should be interpreted with some caution.

Diagnoses of alcohol abuse and other neuropsychiatric disorders among house painters compared with house carpenters.

The incidence of alcoholism and the incidence of other neuropsychiatric diagnoses were compared between the 767 house painters and the 1212 house carpenters, born in 1925 or later, who were members of the Stockholm branches of their respective trade unions in 1965 and who had been members for at least 10 years before 1970. Four different outcome registers were used: (1) the alcohol crime register, which contained all persons who had broken any law regulating the handling and consumption of alcohol (follow up period 1972-6). (2) The register of diagnoses at early retirement (follow up period 1971-84). (3) The register of diagnoses at discharge from inpatient psychiatric care (follow up period 1968-83). (4) The register of causes of death (follow up period 1965-86). Exposures to solvents and consumption of alcohol were evaluated by interviews with samples of the cohorts. A high average cumulative exposure to solvents was found among the painters. The mean consumption of alcohol was similar in the two cohorts. The incidence of diagnoses of neuropsychiatric disorders was higher in painters than in carpenters in all registers. Alcoholism was the most common neuropsychiatric disorder diagnosed and showed the highest relative risk. The excess of alcoholism among the painters was, however, due singularly to painters who had several registrations in the alcohol crime register or diagnoses of alcoholism in multiple registers. Thus the study implies that excessive alcohol consumption or severe damage due to alcohol, or both, but not less severe problems, were more common in painters than in carpenters. This suggests an interaction between exposure to solvents and intake of alcohol causing an increase in diagnosis of alcoholism among painters.