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Biomedical subjects

L Barregård

Publications and source records attributed to L Barregård.

54 records · Page 3Linked to original sources
PubMed1991

Effects of occupational exposure to mercury vapor on lymphocyte micronuclei.

For 26 chloralkali workers exposed to inorganic mercury and 26 age-matched, occupationally unexposed referents, the frequency and size distribution of micronuclei were determined in peripheral lymphocytes stimulated with either phytohemagglutinin or pokeweed mitogen. For the exposed workers the mean concentrations of mercury in urine, plasma, and erythrocytes were 16 nmol/mmol of creatinine, 48 nmol/l, and 78 nmol/l, respectively, and their mean exposure time was 10 years. Neither the frequency nor the size of micronuclei was significantly different in the two groups; nor were there any correlations to current mercury levels. However, in the exposed group, and with phytohemagglutinin as the mitogen, a statistically significant correlation between previous exposure to mercury (cumulative exposure or number of blood mercury peaks) and the frequency of micronuclei was found. This association was also present when the effects of age and smoking were allowed for, and it may indicate an accumulation of cytogenetic effects in T-lymphocytes.

Adult↗
PubMed1991

Polyneuropathy possibly caused by 30 years of low exposure to n-hexane.

A slowly developing, mainly sensory, polyneuropathy was found in a 60-year-old man exposed to n-hexane (10-100 mg/m3) for 30 years in a mountain fuel stockpile. The nerve damage was verified by electromyography and sural nerve biopsy, and it is proposed that also a low-grade, but prolonged, exposure to n-hexane may cause polyneuropathy.

Biopsy↗
PubMed1990

Levels of selenium and antioxidative enzymes following occupational exposure to inorganic mercury.

Levels of selenium and mercury in blood and urine were analysed in 37 male workers exposed to elemental mercury vapour in a chloralkali plant and in 39 unexposed controls of the same age. Mean urinary Hg was 223 nmol l-1 (15 nmol/mmol creatinine) in the exposed group and 26 nmol l-1 (2.0 nmol/mmol creatinine) in the controls. Mean blood and plasma Hg levels were 46 and 36 nmol l-1, respectively, in the exposed group, as compared with 17 and 7 nmol l-1 in the controls. The concentrations of Se in plasma and erythrocytes did not differ between the two groups. Urinary Se levels were, however, slightly but significantly lower in the exposed group (median values 23 vs 29 nmol/mmol creatinine), and there was a negative correlation between urinary Se and plasma Hg in the exposed group. This may be due to a retention of Se in the kidneys. In a subgroup of exposed workers and controls, glutathione peroxidase, superoxide dismutase and catalase were also analysed. No differences were found between the groups with respect to these antioxidative enzymes. The effect on Se status of moderate Hg exposure seems to be of minor clinical importance.

Adult↗
PubMed1990

Mercury in the Swedish chloralkali industry--an evaluation of the exposure and preventive measures over 40 years.

The monitoring of exposure to mercury in the Swedish chloralkali industry started in 1946 and became common in the 1960s. During the 1970s both urinary and blood mercury (U-Hg, B-Hg) concentrations decreased substantially. The mean (geometric) U-Hg was 500-700 nmol l.-1 in the 1960s as compared with 150 nmol l.-1 today. During the 1970s the mean (geometric) B-Hg declined from about 100 to 40 nmol l.-1. Nowadays high values, U-Hg greater than 1500 nmol l.-1 or B-Hg greater than 600 nmol l.-1, are very rare whereas in the 1950s and the 1960s such peak values were found among 30% of the workers. The most effective measures taken were the reduction of the hydrogen discharges from the process and the replacement of graphite anodes by dimensionally stable anodes which require less frequent maintenance. Today efficient cleaning and continuous monitoring make it possible to keep the exposure levels low. The use of respiratory protection equipment is, however, still necessary during certain maintenance operations.

Air Pollutants↗
PubMed1990

Long-term follow up of workers exposed to solvents.

Long term occupational exposure to organic solvents may cause adverse effects to the central nervous system. This collaborative study between six Swedish departments of occupational medicine examines the overall prognosis in terms of working capacity, symptoms, and psychometric test performance for individuals occupationally exposed to organic solvents. After re-analyses of the data from an initial clinical investigation of 111 men, the subjects were divided into two subgroups: one group of 65 with symptoms but no impairment on the tests and one group of 46 with toxic encephalopathy (symptoms and test impairment). At least five years after the initial examination the subjects were asked to attend a re-examination that included a structured medical interview and a psychometric investigation. The results indicate that effects on the central nervous system persist even when exposure has ceased. In the group of 46 more men had stopped working and were receiving sickness or early retirement pensions. This group also had reduced activity levels with regard to everyday life, leisure activities, and education or training and more neuropsychiatric symptoms. There was no support for the view that a solvent induced toxic encephalopathy is a progressive disease comparable with presenile dementia such as Alzheimer's disease or Pick's disease. If a worker was removed from exposure when he presented symptoms without signs of impairment in intellectual function recovery was seen in most cases.

Aged↗
PubMed1990

Normal pituitary hormone response to thyrotrophin and gonadotrophin releasing hormones in subjects exposed to elemental mercury vapour.

Exposure to elemental mercury (Hg) vapour results in an accumulation of Hg in the pituitary, the thyroid, and the testis. In this study, basal serum concentrations of pituitary hormones (thyrotrophin (TSH), prolactin (PRL), follicle stimulating hormone (FSH), and luteinising hormone (LH] or their response after administration of thyrotrophin and gonadotrophin releasing hormones did not differ between 11 male workers (mean urinary Hg (U Hg) concentration 26 nmol/mmol creatinine) and nine male dentists (U Hg concentration 1.3 nmol/mmol creatinine) exposed to elemental Hg vapour when compared with matched referent groups (U Hg concentration 0.6 and 0.4 nmol/mmol creatinine). Thus there was no evidence of an effect of Hg on the pituitary. Neither was there any association between exposure to Hg and serum concentrations of free thyroid hormones (S FT3, S FT4), testosterone, or cortisol. Increased plasma concentrations of selenium (Se) were associated with increased basal serum concentrations of TSH, decreased concentrations of basal serum cortisol, and decreased release of FSH.

Adult↗
PubMed1990

Cerebrospinal fluid proteins in men with chronic encephalopathy after exposure to organic solvents.

Cerebrospinal fluid was examined for 23 patients with chronic toxic encephalopathy after heavy exposure to organic solvents and 23 healthy age-matched referents. No differences were found between the patients and referents with respect to the levels of albumin, immunoglobulin, prealbumin, alpha-1-antitrypsin, beta-2-microglobulin, haptoglobin, or the astroglial cell proteins S100 and glial fibrillary acidic protein in the cerebrospinal fluid. The albumin ratio was normal for both the patients and the referents. The patient group had had heavy exposure to organic solvents, but its members had not been exposed for at least one year before the study. It was concluded that, if exposure to organic solvents affects proteins in cerebrospinal fluid, such effects are probably reversible.

Adult↗
PubMed1990

Mortality and cancer incidence in chloralkali workers exposed to inorganic mercury.

Mortality and cancer incidence were studied in men exposed to inorganic mercury at eight Swedish chloralkali plants where individual biological monitoring data were available. Urinary mercury excretion has declined from about 200 micrograms/l during the 1950s to less than 50 micrograms/l today. These workers had also been exposed to chlorine and static magnetic fields. At some of the plants there had been a low degree of exposure to asbestos. In total, 1190 men had been monitored for at least one year between 1946 and 1984. Their mortality and cancer incidence were compared with those of the general male population. Mortality from all causes was not significantly increased (rate ratio = 1.1). Cardiovascular mortality was slightly increased (rate ratio = 1.3; 95% CI 1.0-1.5) for no known reason. An excess of lung tumours was seen (rate ratio = 2.0; 95% CI 1.0-3.8), possibly caused by previous exposure to asbestos. Mortality from non-malignant diseases of the brain and the kidneys, the main target organs in mercury poisoning, was not increased, nor was the incidence of brain tumours (3 observed v 1.1 expected) or kidney tumours (3 observed v 1.9 expected).

Aged↗
PubMed1988

Enzymuria in workers exposed to inorganic mercury.

Urinary excretion of beta-hexosaminidase (NAG = N-acetyl-beta-glucosaminidase) and albumin was examined in 41 chlor-alkali workers exposed to inorganic mercury and 41 age-matched controls. Either U-HG or B-Hg levels for these workers were available dating from the 1960s to the present. Increased U-NAG was seen in workers with a U-Hg today of more than 4 micrograms/mmol creat (about 50 micrograms/l: 35 ug/g creat). Multiple linear regression analysis showed that U-NAG was correlated to U-Hg and integrated dose but not to the present B-Hg level. No albuminuria (detection limit 12.5 mg/l) was found in any of the subjects. In a longitudinal study, no decrease in U-NAG levels was seen in 15 chlor-alkali workers after their vacation (means = 20d). In five workers followed for ten months after a short exposure period, no definite time trend could be seen. The results show that there is a slight effect on renal tubules even at rather low levels of exposure to mercury vapour. The clinical significance of the enzymuria levels found here is, however, debatable.

Acetylglucosaminidase↗
PubMed1986

Chronic and acute effects of solvents on central nervous system functions in floorlayers.

Floorlayers and age matched carpenters with long (greater than or equal to 20 years) and short (5-10 years) occupational experience were compared with respect to chronic and acute neuropsychiatric, neuropsychological, and general health effects as related to different types of solvent exposure. An increased prevalence of neuropsychiatric illness occurred among floorlayers with long occupational experience, possibly caused by high levels of exposure which were present until the 1970s. The disease appears partly reversible since, at the time of the investigation, all had essentially recovered. Some impairment of performance in psychological tests was seen, however, in this group. Visuoanalytical impairment was associated with indices of exposure to glues based on alcohols whereas contact adhesives appeared more deleterious to perceptual functions. The increased prevalence of neuropsychiatric symptoms among the floorlayers was interpreted to reflect mainly acute effects on the central nervous system.

Acute Disease↗
PubMed1984

Is there an ototraumatic interaction between noise and solvents?

A review of the literature and four case reports are presented. The patients had all been exposed to noise as well as to organic solvents and they demonstrate a much more pronounced sensorineural hearing loss than would be expected from their noise exposure only. In one of the cases a psycho-organic syndrome due to solvent exposure was verified. Audiograms from 32 painters in a shipyard who had been exposed to noise and solvents did not, however, show any clustering of inexplicably pronounced sensorineural hearing losses. With reference to the above cases it is suggested that there might be a possibility of an ototraumatic interaction between solvents and noise. In view of the neurotoxic effects of organic solvents, such an interaction is conceivable.

Aged↗
PubMedDate not supplied

Within-day variability of magnetic fields among electric utility workers: consequences for measurement strategies.

Occupational exposure to 50-Hz magnetic fields was surveyed among electric utility workers to investigate (1) components of exposure variability, (2) patterns of autocorrelation between short-term measurements, and (3) imprecision and misclassification due to short-term measurements. Spot measurements every 10 seconds during 81 working days were analyzed for 42 electric utility workers from 10 occupational subgroups and during 8 working days for 4 office workers from the same company. For the 8-hour time-weighted average (TWA) magnetic fields, the variability was partitioned into its components: within workers, between workers, and between groups. For spot measurements of magnetic fields, the within-day variance component also was examined. Autocorrelation functions were determined and numbers of short-term measurements necessary for reliable estimates of 8-hour TWA magnetic fields were assessed. Spot measurements of magnetic fields, as well as 8-hour TWA magnetic fields, were approximately log normally distributed among workers. The mean exposure to magnetic fields was 0.47 microT (n = 81 days) in electric utility workers and 0.12 microT (n = 8 days) in office workers. A large fraction, 76% of the spot measurements total variance, could be attributed to variability within days. For the 8-hour TWA magnetic fields, between-group variability was small and of the same magnitude as between-worker variability. Significant autocorrelations between short-term averages of 7.5, 15, and 30 minutes were present, when taken within periods of 30 minutes. One-hour averages showed no autocorrelation. Simulations showed that, due to high within-day variability and autocorrelation, a limited number of short-term measurements of magnetic fields in electric utility workers are likely to result in imprecise estimates of 8-hour TWA magnetic fields. Measurement strategies relying on short-term (spot) measurements are therefore likely to result in misclassification of exposure and consequently absent or spurious exposure-response relations.

Electromagnetic Fields↗
PubMedDate not supplied

Kinetics of mercury in blood and urine after brief occupational exposure.

The decrease in mercury (Hg) levels in whole blood (B), plasma (P), erythrocytes (Ery), and urine (U) was investigated in nine men after 3 d of intense (greater than 100 micrograms/m3) exposure to metallic Hg vapor. In a model in which common half-times for all subjects were used, the best fit for B-Hg was obtained with half-times of 3.1 d for a fast phase and 18 d for a slow phase. P-Hg seemed to decay more rapidly than Ery-Hg. Peak U-Hg (morning, creatinine-corrected samples) was not observed until 2-3 wk after exposure. Thereafter, the median half-time was 40 d (assuming individual one-compartment models). In a model for which common half-times were used, the point estimates were 59 d for a one-compartment model and 28 and 141 d for a two-compartment model. The fractions of the fast phases (i.e., two-compartment models with common half-times) were 80% for B-Hg and 84% for U-Hg.

Environmental Monitoring↗
PubMedDate not supplied

Neuropsychological deficits in patients diagnosed with chronic toxic encephalopathy: which tests are most discriminative?

Chronic toxic encephalopathy (CTE), a syndrome affecting the central nervous system, has been associated with long-term occupational exposure to organic solvents. We studied the discriminative power of a series of cognitive tests in separating 20 patients exposed to organic solvents, diagnosed with CTE, from 27 non-CTE patients with similar symptoms and exposure, and 19 healthy referents. All subjects were examined with a test battery assessing various cognitive and psychomotor functions. The groups were comparable with regard to age and level of schooling. Stepwise discriminant analyses indicated that tests assessing perceptual speed and attention were the most sensitive in distinguishing the CTE patients from the other patients as well as from the healthy referents. The CTE patients performed worse than the two other groups not only in tests assessing perceptual speed and attention, visual memory, and visuo-spatial skill but also, contrary to expectation, in a test of verbal ability.

Journal Article↗
PubMedDate not supplied

Within-day variability of magnetic fields among electric utility workers: consequences for measurement strategies.

Occupational exposure to 50-Hz magnetic fields was surveyed among electric utility workers to investigate (1) components of exposure variability, (2) patterns of autocorrelation between short-term measurements, and (3) imprecision and misclassification due to short-term measurements. Spot measurements every 10 seconds during 81 working days were analyzed for 42 electric utility workers from 10 occupational subgroups and during 8 working days for 4 office workers from the same company. For the 8-hour time-weighted average (TWA) magnetic fields, the variability was partitioned into its components: within workers, between workers, and between groups. For spot measurements of magnetic fields, the within-day variance component also was examined. Autocorrelation functions were determined and numbers of short-term measurements necessary for reliable estimates of 8-hour TWA magnetic fields were assessed. Spot measurements of magnetic fields, as well as 8-hour TWA magnetic fields, were approximately lognormally distributed among workers. The mean exposure to magnetic fields was 0.47 microT (n = 81 days) in electric utility workers and 0.12 microT (n = 8 days) in office workers. A large fraction, 76% of the spot measurements total variance, could be attributed to variability within days. For the 8-hour TWA magnetic fields, between-group variability was small and of the same magnitude as between-worker variability. Significant autocorrelations between short-term averages of 7.5, 15, and 30 minutes were present, when taken within periods of 30 minutes. One-hour averages showed no autocorrelation. Simulations showed that, due to high within-day variability and autocorrelation, a limited number of short-term measurements of magnetic fields in electric utility workers are likely to result in imprecise estimates of 8-hour TWA magnetic fields. Measurement strategies relying on short-term (spot) measurements are therefore likely to result in misclassification of exposure and consequently absent or spurious exposure-response relations.

Electromagnetic Fields↗