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Biomedical subjects

L Barregård

Publications and source records attributed to L Barregård.

At least 19 recordsLinked to original sources
PubMed1996

Estimated exposure to static magnetic fields for the staffs of NMR-units.

Exposure of the staffs to static magnetic fields of NMR-units, was investigated at two departments for chemical analysis (static field strength of the systems 11.7 and 4.7 Tesla) and two for clinical imaging (0.5 and 0.02 Tesla). The exposure time was estimated by personal interviews. The magnetic flux density was highly dependent on distance to the magnet, and the magnetic fields in normal work with the NMR-units were, during most working time, lower than 1 milliTesla (mT), which is far below the whole-body limit recommended by the American Conference of Governmental and Industrial Hygienists (60 mT), the British National Radiation Protection Board (200 mT), or the international Commission on Non-Ionizing Radiation Protection (200 mT). During short periods, when changing samples or assisting anxious patients, the fields may be strong (100-150 mT). The recommended ceiling values (2-5 Tesla) are, however, not exceeded.

Electromagnetic Fields↗
PubMed1996

Long-term use of nicotine chewing gum and mercury exposure from dental amalgam fillings.

In experimental studies, chewing gum has been shown to increase the release rate of mercury vapor from dental amalgam fillings. The aim of the present study was to investigate the influence of long-term frequent chewing on mercury levels in plasma and urine. Mercury levels in plasma (P-Hg) and urine (U-Hg), and urinary cotinine were examined in 18 subjects who regularly used nicotine chewing gum, and in 19 referents. Age and number of amalgam surfaces were similar in the two groups. Total mercury concentrations in plasma and urine were determined by means of cold vapor atomic absorption spectrometry. Urinary cotinine was determined by gas chromatography-mass spectrometry. The chewers had been using 10 (median) pieces of gum per day for the past 27 (median) months. P-Hg and U-Hg levels were significantly higher in the chewers (27 nmol/L and 6.5 nmol/mmol creatinine) than in the referents (4.9 nmol/L and 1.2 nmol/mmol creatinine). In both groups, significant correlations were found between P-Hg or U-Hg on the one hand and the number of amalgam surfaces on the other. In the chewers, no correlations were found between P-Hg or U-Hg and chewing time per day or cotinine in urine. Cotinine in urine increased with the number of pieces of chewing gum used. The impact of excessive chewing on mercury levels was considerable.

Adult↗
PubMed1995

In vivo XRF analysis of mercury: the relation between concentrations in the kidney and the urine.

The objective of this study was to determine the concentrations of mercury in organs of occupationally exposed workers using in vivo x-ray fluorescence analysis. Twenty mercury exposed workers and twelve occupationally unexposed referents participated in the study. Their mercury levels in kidney, liver and thyroid were measured using a technique based on excitation with partly plane polarized photons. The mercury levels in blood and urine were determined using atomic absorption spectrophotometry. The detection limit for mercury in the kidney was exceeded in nine of the exposed workers, but in none of the referents. The mean kidney mercury concentration (including estimates below the detection limits) was 24 micrograms g-1 in the exposed workers, and 1 microgram g-1 in the referents. The association between mercury in the kidney and in urine was statistically significant, but it was unclear whether the relation was linear. The measurements on liver (n = 10) and thyroid (n = 8) in the exposed workers showed mercury levels below the detection limit. The study shows that it is now possible to measure the mercury concentrations in kidneys of occupationally exposed persons, using in vivo x-ray fluorescence. The estimated concentrations are in reasonable agreement with the limited human autopsy data, and the results of animal studies.

Adult↗
PubMed1995

People with high mercury uptake from their own dental amalgam fillings.

OBJECTIVES: To describe people with high mercury (Hg) uptake from their amalgam fillings, and to estimate the possible fraction of the occupationally unexposed Swedish population with high excretion of urinary Hg. METHODS: Three case reports are presented. The distribution of excretion of urinary Hg in the general population was examined in pooled data from several sources. RESULTS: The three cases excreted 23-60 micrograms of Hg/day (25-54 micrograms/g creatinine), indicating daily uptake of Hg as high as 100 micrograms. Blood Hg was 12-23 micrograms/l, which is five to 10 times the average in the general population. No other sources of exposure were found, and removal of the amalgam fillings resulted in normal Hg concentrations. Chewing gum and bruxism were the probable reasons for the increased Hg uptake. Extrapolations from data on urinary Hg in the general population indicate that the number of people with urinary excretion of > or = 50 micrograms/g creatinine could in fact be larger than the number of workers with equivalent exposure from occupational sources. CONCLUSION: Although the average daily Hg uptake from dental amalgam fillings is low, there is a considerable variation between people; certain people have a high mercury uptake from their amalgam fillings.

Adult↗
PubMed1994

Mercury and proteins in cerebrospinal fluid in subjects exposed to mercury vapor.

Mercury (Hg) and protein levels in cerebrospinal fluid (CSF), and mercury in plasma (P), erythrocytes (Ery), and urine (U), were determined in 10 workers exposed to mercury vapor for 2-28 (median 13) years and in 16 occupationally unexposed referents. CSF-Hg was analyzed using radiochemical neutron activation analysis and P-Hg, Ery-Hg, and U-Hg were analyzed using cold-vapor atomic absorption spectrometry. P-Hg and U-Hg were significantly higher, but Ery-Hg was similar in the exposed workers (37 nmole/liter, 16 nmole/mmole creatinine, and 56 nmole/liter, respectively) compared with the referents (7.1 nmole/liter, 1.9 nmole/mmole creatinine, and 52 nmole/liter, respectively). CSF-Hg was correlated to P-Hg, and in workers with current high exposure (P-Hg > 50 nmole/liter), the CSF-Hg was significantly higher than in the reference group (1.08 versus 0.35 nmole/liter; P = 0.002). In two individuals, studied after ceased occupational exposure, a decrease of CSF-Hg was seen. There were no indications of changes in the CSF protein pattern in the exposed workers.

Adult↗
PubMed1994

No indication of in vivo methylation of inorganic mercury in chloralkali workers.

It has been shown in vitro that human oral and intestinal bacteria are able to methylate inorganic mercury (Hg) to methylmercury (MeHg). In vivo methylation has been reported for guinea pigs, and several studies have found higher levels of organic Hg in blood of workers exposed to inorganic Hg. In search for indications of in vivo methylation of Hg, we determined total Hg in urine (U), plasma (P), and erythrocytes (Ery), and MeHg in erythrocytes, in 22 chloralkali workers exposed to inorganic Hg, and in 22 age-matched referents. The subjects in both groups ate fish not more than once a week. MeHg was determined using ion exchange separation and cold vapor atomic absorption spectrometry. The mean concentrations of total mercury in chloralkali workers and referents were 26 vs 2.3 micrograms/g creatinine (U-Hg), 9.7 vs 1.8 ng/g (P-Hg), and 11.4 vs 5.6 ng/g (Ery-Hg). The mean Ery-MeHg concentrations were 3.0 vs 3.7 ng/g, and there were no correlations between Ery-MeHg on the one hand and U-Hg or P-Hg on the other. Our results indicate no significant in vivo methylation of inorganic Hg in man. Contradictory results from previous studies may be due either to bias owing to fish consumption or to analytical shortcomings.

Alkalies↗
PubMed1994

Hand eczema in car mechanics.

To estimate the prevalence of hand eczema, a questionnaire was distributed to 901 male car mechanics. Of the 801 persons who responded, 15% reported hand eczema on some occasion in the previous 12 months, and 57% admitted dry skin on the hands. In a 2nd part of the study, those who reported hand eczema were examined and patch tested with a standard series and a special "car mechanics' series". The most common diagnosis was irritant contact dermatitis, 55%, and 2nd was allergic contact dermatitis, 19%. 35/105 (33%) had a total of 51 positive patch test reactions, all to substances in the standard series, except for 2 persons who reacted to oxidized d-limonene. The most frequent reactions were to thimerosal (9%), nickel (8%) and colophony (5%). One plausible explanation for the high prevalence of nickel allergy was the common use of nickel-plated tools. 5 individuals had a history of contact urticaria, but scratch tests were negative. It was concluded that car mechanics are at high risk for contact dermatitis on the hands, irritant as well as allergic.

Adolescent↗
PubMed1994

Clearance half life of mercury in urine after the cessation of long term occupational exposure: influence of a chelating agent (DMPS) on excretion of mercury in urine.

The elimination of mercury (Hg) in urine was investigated in 12 former chloro-alkali workers exposed to metallic Hg vapour for two to 18 (median five) years. Morning urine samples were taken on several (median 9) occasions after change of employment or retirement. The median follow up time was 28 months. The decrease in concentration of Hg in urine (U-Hg) was well characterised by a one compartment model. Three different regression methods were used; non-linear least squares regression (NLSR), weighted non-linear least squares regression (WNLSR), and linear least squares regression (LLSR) after log transformation of the U-Hg data. The median half life from the WNLSR method was 55 days. There were no large differences in the half life estimates given by the WNLSR or the NLSR methods, but for five subjects the LLSR method gave poor fits. There was a non-significant tendency towards longer half lives with higher initial U-Hg. About three years after the cessation of occupational exposure a mobilisation test with 2,3-dimercaptopropane-1-sulphonate (DMPS) was performed on seven subjects. Excretion of Hg, copper (Cu), and zinc (Zn) in urine was estimated before and after the ingestion of 300 mg of DMPS. Treatment with DMPS increased 24 hour urinary excretion by a factor of 7.6 for Hg, 12 for Cu, and 1.5 for Zn. The relative increase in U-Hg was not significantly higher than that obtained in a previous study of an occupationally unexposed group. A major proportion (62%) of Hg excreted during 24 hours after DMPS appeared in the first six hours.

Adult↗
PubMed1994

Endocrine function in mercury exposed chloralkali workers.

OBJECTIVE: The aim was to study whether functional impairment of the pituitary, thyroid, testes, and adrenal glands of humans occupationally exposed to mercury (Hg) vapour can be shown as a result of accumulation of Hg in these glands. METHODS: Basal concentrations of thyrotrophin (TSH), prolactin, free thyroxine (free T4), free 3,5,3'-triiodothyronine (free T3), antibodies against thyroperoxidase, and testosterone in serum, as well as cortisol in morning urine were measured in 41 chloralkali workers exposed (10 years on average) to Hg vapour, and in 41 age matched occupationally unexposed referents. The chloralkali workers had a mean urinary Hg concentration (U-Hg) of 15 nmol/mmol (27 micrograms/g) creatinine, and a mean blood Hg concentration (B-Hg) of 46 nmol/l. For the reference group U-Hg and B-Hg were 1.9 nmol/mmol (3.3 micrograms/g) creatinine and 17 nmol/l respectively. RESULTS: The serum free T4 concentration and the ratio free T4/free T3 were slightly, but significantly, higher in the subgroups with the highest exposure, and the serum free T3 was inversely associated with cumulative Hg exposure. This indicates a possible inhibitory effect of mercury on 5'-deiodinases, which are responsible for the conversion of T4 to the active hormone T3. Serum total testosterone, but not free testosterone, was positively correlated with cumulative Hg exposure. Prolactin, TSH and urinary cortisol concentrations were not significantly associated to exposure. CONCLUSION: Apart from inhibition of the deiodination of T4 to T3, the endocrine functions studied seem not to be affected by exposure to Hg vapour at the exposure levels of the present study. Growth hormone secretion was not studied.

Adrenal Glands↗
PubMed1993

Assessment of renal dysfunction in workers previously exposed to mercury vapour at a chloralkali plant.

Urinary albumin concentration (U-alb) and N-acetyl-beta-D-glucosaminidase (U-NAG) and glomerular basement membrane antibodies (a-GBMs) in serum samples were measured in 77 chloralkali workers previously exposed to mercury (Hg) vapour and 53 age matched referents. The exposure ceased on average 12.3 (range 1-35) years before the study. The mean exposure time was 7.9 (range 1.1-36.2) years. The mean yearly urinary Hg concentration (U-Hg) was 531 nmol/l. The concentrations of the urinary isoenzymes NAG A (U-NAG A) and NAG B (U-NAG B) were determined in 30 highly exposed subjects and 30 referents. No differences in U-alb or U-NAG, U-NAG A, or U-NAG B were found between the groups. Higher concentrations of a-GBMs were found among subjects who stopped exposure a short time before the study, but there was no association between a-GBMs and U-alb. The U-NAG and U-NAG A were negatively correlated with storage time. The results may suggest that microalbuminuria and enzymuria reported in subjects with ongoing exposure to Hg vapour are reversible in most instances.

Acetylglucosaminidase↗
PubMed1993

Biological monitoring of exposure to mercury vapor.

Biological monitoring of mercury in whole blood (B-Hg) or urine (U-Hg) can be used to assess exposure to mercury vapor if the kinetics and other sources of variation are taken into account. Its rapid rise postexposure makes B-Hg a good indicator of recent exposure peaks, while U-Hg (corrected for urinary flow rate) reflects average long-term exposure. However, high intraindividual variation sometimes requires the average of several U-Hg determinations. In the general population, methylmercury from fish and mercury from dental amalgam influence B-Hg and U-Hg, respectively, and must be considered if other exposures are being monitored. The quantitative relations between mercury in biological fluids and critical organs are poorly understood. Monitoring U-Hg is useful for assessing the risk of adverse effects and the need for preventive measures. At average U-Hg levels of about 50 micrograms.g creatinine-1 (28 nmol.mmol creatinine-1) the prevalence of symptoms and slight objective changes in the central nervous system and the excretion of certain urinary proteins are increased.

Air Pollutants↗
PubMed1993

Decrease in mercury concentration in blood after long term exposure: a kinetic study of chloralkali workers.

The elimination of mercury (Hg) in blood was investigated in 14 chloralkali workers exposed to metallic Hg vapour for 1-24 (median 10) years. Blood and urine samples were collected on several (median eight) occasions during a period of 17-26 days. The initial Hg concentrations were about 80 nmol/l in whole blood (B-Hg) and 17 nmol/mmol creatinine in urine (U-Hg). The decrease in Hg in whole blood, plasma (P) and erythrocytes (Ery) was best characterised by a two compartment model. In a model with a common half life for all subjects, the best fit for B-Hg was obtained with half lives of 3.8 days for a fast phase and 45 days for a slow phase. The half life of the fast phase was shorter for P-Hg than for Ery-Hg, whereas the opposite was the case for the slow phase. The half lives of the slow phases in whole blood and plasma were longer, and the relative fractions of the slow phases were higher (about 50%) after long term exposure than those (about 20%) reported after brief exposure. Slower elimination indicates higher accumulation of Hg in organs with long half lives, and possibly the presence of at least one additional, even slower compartment. The U-Hg fluctuated substantially during the sampling period, and average concentrations decreased only slightly.

Adult↗
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↗