Experimental exposure to wood smoke: effects on airway inflammation and oxidative stress

BACKGROUND

Particulate air pollution affects cardiovascular and pulmonary disease and mortality. A main hypothesis about the mechanisms involved is that particles induce inflammation in lower airways, systemic inflammation and oxidative stress.

OBJECTIVES

To examine whether short-term exposure to wood smoke in healthy subjects affects markers of pulmonary inflammation and oxidative stress.

METHODS

13 subjects were exposed first to clean air and then to wood smoke in a chamber during 4-hour sessions, 1 week apart. The mass concentrations of fine particles at wood smoke exposure were 240-280 mug/m(3), and number concentrations were 95 000-180 000/cm(3), about half of the particles being ultrafine (<100 nm). Blood and breath samples were taken before and at various intervals after exposure to wood smoke and clean air and examined for exhaled nitric oxide and Clara cell protein in serum and urine, and malondialdehyde in exhaled breath condensate.

RESULTS

Exposure to wood smoke increased alveolar nitric oxide 3 hours post-exposure while malondialdehyde levels in breath condensate were higher both immediately after and 20 hours after exposure. Serum Clara cell protein was increased 20 hours after exposure.

CONCLUSIONS

Wood smoke at levels that can be found in smoky indoor environments caused an inflammatory response and signs of increased oxidative stress in the respiratory tract, especially in the lower airways.

Self-reported symptoms and their effects on cognitive functioning in workers with past exposure to solvent-based glues: an 18-year follow-up

OBJECTIVES

To examine to what extent exposure to organic solvents during the working life affects general well-being in the long term, and to explore the relationship between self-reported symptoms and cognitive functioning in previously solvent-exposed floor layers.

METHODS

The study included 41 solvent-exposed floor layers and 40 unexposed referents participating in a longitudinal follow-up study 18 years after the baseline assessment. Symptom prevalence and level of spare time activities were studied using the same methods as in the initial study. These include a general health examination, the Q16 symptom questionnaire, and a questionnaire for spare time activities. Relationships between symptoms and cognitive functioning were analysed based on recently published data on cognitive functioning of the participants at follow-up.

RESULTS

At follow-up neuropsychiatric symptoms such as need to check things, depressive mood, and abnormal fatigue, were more prevalent among floor layers, particularly the most exposed individuals, than among referents. In addition, the most highly exposed floor layers reported more concentration difficulties and irritability. Fatigue and depressive mood increased over the follow-up time in the most exposed floor layers but not in the referents. Memory difficulties, although more frequent among floor layers than among referents, had decreased in floor layers while increased in referents. Floor layers also reported some negative effects on intimate relations and activity level. Neuropsychiatric symptoms were related to poorer performance chiefly in memory tasks and tests of complex attention and perceptual speed, more seldom in visuospatial tasks.

CONCLUSIONS

Findings of exposure-related, long-lasting, partly deteriorating neuropsychiatric complaints indicate that general well-being later in life has been affected in floor layers with past heavy solvent exposure. We also found frequent associations between symptom prevalence and the cognitive functioning. Together with previous findings of dose-related cognitive decrements, the present results strengthen the evidence that long-term heavy occupational solvent exposure may negatively interact with the normal ageing process.

Influence of solvent exposure and aging on cognitive functioning: an 18 year follow up of formerly exposed floor layers and their controls

OBJECTIVES

To extend our knowledge of how exposure to neurotoxic substances during working life affects cognitive functioning in the long term. Does long term occupational exposure to organic solvents lead to aggravated cognitive impairment later in life?

METHODS

A follow up was conducted of floor layers exposed to solvents and their unexposed referents (carpenters) 18 years after the baseline assessment. The pattern of cognitive changes in the two groups was compared, with the same 10 neuropsychological tests from the test battery for investigating functional disorders (TUFF) that were used at baseline. The study included 41 floor layers and 40 carpenters. A medical examination focused on health at the present and during the past 18 years. An extensive exposure assessment made in the initial study included questionnaires, interviews, and measurements. Additional exposure during the follow up period was minor, as explored in interviews at follow up.

RESULTS

The entire group of floor layers did not deteriorate significantly more over time than did the carpenters. However, among the oldest subjects (>60 years), only floor layers showed decline in visual memory. Moreover, the most highly exposed floor layers deteriorated significantly more than their referents in visual memory and perceptual speed, and they tended to display larger decrements in motor speed. Significant dose effect relations were found; higher cumulative exposure was associated with decrements in visual episodic memory, perceptual speed and attention, and visuospatial skill.

CONCLUSIONS

The hypothesis that floor layers would deteriorate more in cognitive performance than their unexposed referents over a period of 18 years was partly supported by the results of this study. The results are consistent with the view that the negative effects of exposure to solvents may interact with the normal aging process, primarily at heavy exposure.

Heterogeneity in sources of exposure variability among groups of workers exposed to inorganic mercury

Many exposure assessment strategies rely on the occupational group as the unit of analysis in which workers are classified on the basis of job title, location, or on other characteristics related to the workplace or the job. Although statistical methods that combine exposure data collected on workers from different occupational groups are more efficient, the underlying assumption that the degree of variation over time and among workers is the same for all groups has yet to be fully investigated. Given the utility of different modeling approaches when assessing exposures, we investigated assumptions of homogeneity of variance within and between workers using both random- and mixed-effects models. In our study of four groups of workers exposed to inorganic mercury (Hg) at a chloralkali plant, there was no evidence of significant heterogeneity in the levels of variation over time or between workers for air Hg levels. For the biological monitoring data, however, our findings indicate that groups did not share common levels of variability and that it was not appropriate to pool the data and obtain single estimates of the within- and between-worker variance components. Classification of job group as a random or fixed effect had no effect on the results and yielded the same conclusions when the models were compared. To illustrate effects related to the proper specification of a model, the likelihood of exceeding certain levels (which is a function of the parameters of the underlying distribution of the natural log-transformed exposures) was evaluated using the results obtained from the different models. Although the probability that workers' mean exposures exceeded occupational exposure limits for air, urine and blood Hg was generally low (<10%) for all groups except maintenance workers, the estimated values sometimes varied depending upon the particular model that was applied. Given the growing use of random- and mixed-effects models that combine data across occupational groups, additional studies are warranted to evaluate whether it is reasonable to assume common variances and covariances among measurements collected on workers from different groups.

Mortality from cardiovascular diseases and exposure to inorganic mercury

OBJECTIVE

To study the mortality from cardiovascular and other chronic non-neoplastic diseases after long term exposure to inorganic mercury. Limited information is available on the effect of chronic exposure to mercury on the cardiovascular system.

METHODS

The mortality was studied among 6784 male and 265 female workers from four mercury mines and mills in Spain, Slovenia, Italy, and the Ukraine. Workers were employed between 1900 and 1990; the follow up period lasted from the 1950s to the 1990s. The mortality of the workers was compared with national reference rates.

RESULTS

Among men, there was a slight increase in overall mortality (standardised mortality ratio (SMR) 1.08, 95% confidence interval (95% CI) 1.04 to 1.12). An increased mortality was found from hypertension (SMR 1.46, 95% CI 1.08 to 1.93), heart diseases other than ischaemic (SMR 1.36, 95% CI 1.20 to 1.53), pneumoconiosis (SMR 27.1, 95% CI 23.1 to 31.6), and nephritis and nephrosis (SMR 1.55, 95% CI 1.13 to 2.06). The increase in mortality from cardiovascular diseases was not consistent among countries. Mortality from hypertension and other heart diseases increased with estimated cumulative exposure to mercury; mortality from ischaemic heart disease and cerebrovascular diseases increased with duration of employment, but not with estimated exposure to mercury. Results among women were hampered by few deaths.

CONCLUSION

Despite limited quantitative data on exposure, possible confounding, and likely misclassification of disease, the study suggests a possible association between employment in mercury mining and refining and risk in some groups of cardiovascular diseases.

Variability in airborne and biological measures of exposure to mercury in the chloralkali industry: implications for epidemiologic studies

Exposure assessment is a critical component of epidemiologic studies, and more sophisticated approaches require that variation in exposure be considered. We examined the intra- and interindividual sources of variation in exposure to mercury vapor as measured in air, blood, and urine among four groups of workers during 1990-1997 at a Swedish chloralkali plant. Consistent with the underlying kinetics of mercury in the body, the variability of biological measures was dampened considerably relative to the variation in airborne levels. Owing to the effects of intraindividual variation, estimating workers' exposures from a few measurements can attenuate measures of effect. To examine such effects on studies relating long-term exposure to a continuous health outcome, we evaluated the utility of each exposure measure by comparing the necessary sample sizes required for accurate estimation of a slope coefficient obtained from a regression analysis. No single measure outperformed the others for all groups of workers. However, when workers were evaluated together, creatinine-corrected urinary mercury better discriminated workers' exposures than airborne or blood mercury levels. Thus, pilot studies should be conducted to examine variability in both air and biomonitoring data because quantitative information about the relative magnitude of the intra- and interindividual sources of variation feeds directly into our efforts to design an optimal sampling strategy when evaluating health risks associated with occupational or environmental contaminants.

A small dose of ethanol increases the exhalation of mercury in low-level-exposed humans

Inorganic mercury is mainly eliminated by urinary and fecal excretion, but it is also eliminated by exhalation and sweat. There are only a few reports on exhalation of mercury in humans. In volunteers with short-term mercury exposure, an increased exhalation of mercury was found after alcohol intake. The aim of this study was to determine mercury in end-exhaled air and the influence of ethanol on mercury exhalation in subjects with long-term mercury exposure from diet, amalgam fillings, or the work environment. Fourteen subjects, with different grades of mercury exposure, were given 0.2 g ethanol/kg body weight. Measurements of mercury in end-exhaled air were performed before and after alcohol intake. Mercury in end-exhaled air could be detected in all subjects. In 10 individuals without amalgam fillings the mercury concentration was 3 to 12 pg/L. A marked increase, in general about fivefold, in mercury concentrations in end-exhaled air was seen in all subjects 30 min after intake of alcohol, regardless of the level of mercury exposure. Higher ethanol doses resulted in higher mercury levels in end-exhaled air and longer time periods before a return to background levels. An increase was seen even after an ethanol dose of only 0.1 g ethanol/kg body weight (about 0.08 L wine). The decrease in exhaled mercury at higher alcohol doses followed approximately zero-order kinetics and probably reflects the elimination of ethanol in tissues. In conclusion, low levels of mercury can be detected in end-exhaled air also in individuals without amalgam fillings. About a fivefold increase was seen 30 min after alcohol intake, and the relative increase seemed to be independent of the body burden of mercury. Exhalation of mercury represents only a small percentage of the total elimination of mercury.

Cadmium, mercury, and lead in kidney cortex of the general Swedish population: a study of biopsies from living kidney donors

Cadmium, mercury, and lead concentrations were determined in deep-frozen kidney cortex biopsies taken from 36 living, healthy Swedish kidney donors (18 males and 18 females), who were 30-71 (mean 53) years of age. Information about occupation, smoking, the presence of dental amalgam, and fish consumption could be obtained for 27 of the donors. The samples (median dry weight 0.74 mg) were analyzed using inductively coupled plasma mass spectrometry, and the results were transformed to wet-weight concentrations. The median kidney Cd was 17 micrograms/g (95% confidence interval, 14-23 micrograms/g), which was similar in males and females. In 10 active smokers, the median kidney Cd was 24 micrograms/g, and in 12 who never smoked, it was 17 micrograms/g. The median kidney Hg was 0.29 micrograms/g, with higher levels in females (median 0.54 micrograms/g) than in males (median 0.16 micrograms/g). Subjects with amalgam fillings had higher kidney Hg (median 0.47 micrograms/g, n = 20) than those without dental amalgam (median 0.15 micrograms;g/g, n = 6), but kidney Hg was below the detection limit in some samples. Nearly half of the samples had kidney Pb below the detection limit. The median kidney Pb was estimated as 0. 14 micrograms/g. This is the first study of heavy metals in kidney cortex of living, healthy subjects, and the results are relatively similar to those of a few previous autopsy studies, indicating that results from autopsy cases are not seriously biased in relation to kidney metal concentrations in the general population. Cd concentrations in those who never smoked were relatively high, indicating considerable Cd intake from the diet in Sweden. The effect of dental amalgam on kidney Hg was as expected, although the reason for the difference in Hg levels between males and females is unclear.

Cancer occurrence among European mercury miners

OBJECTIVES

To study the carcinogenicity of inorganic mercury in humans.

METHODS

We studied the mortality from cancer among 6784 male and 265 female workers of four mercury mines and mills in Spain, Slovenia, Italy and the Ukraine. Workers were employed between the beginning of the century and 1990; the follow-up period lasted from the 1950s to the 1990s. We compared the mortality of the workers with national reference rates.

RESULTS

Among men, there was no overall excess cancer mortality; an increase was observed in mortality from lung cancer (standardized mortality ratio [SMR] 1.19, 95 percent confidence interval [CI] 1.03-1.38) and liver cancer (SMR 1.64, CI 1.18-2.22). The increase in lung cancer risk was restricted to workers from Slovenia and the Ukraine: no relationship was found with duration of employment or estimated mercu ry exposure. The increase in liver cancer risk was present both among miners and millers and was stronger in workers from Italy and Slovenia: there was a trend with estimated cumulative exposure but not with duration of employment, and the excess was not present in a parallel analysis of cancer incidence among workers from Slovenia. No increase was observed for other types of cancer, including brain and kidney tumours. Among female workers (Ukraine only), three deaths occurred from ovarian cancer, likely representing an excess.

CONCLUSIONS

Exposure to inorganic mercury in mines and mills does not seem strongly associated with cancer risk, with the possible exception of liver cancer; the increase in lung cancer may be explained by co-exposure to crystalline silica and radon.

Tissue levels of mercury determined in a deceased worker after occupational exposure

OBJECTIVES

To examine mercury (Hg) and selenium (Se) levels in autopsy samples from a thermometer worker who had been exposed over a long period to, and monitored for, mercury vapor.

CASE REPORT

Hg and Se levels were determined using radiochemical neutron activation analysis in a worker who had commited suicide 4 weeks after the end of 14 years of exposure and in an unexposed age-matched referent. Histochemical staining of cerebellum was performed according to the method of Danscher and Schroder.

RESULTS

The Hg concentrations (wet weight) were 25 microg/g in the kidney cortex, 1.2 microg/g in the liver, 0.72 microg/g in the lung, 0.025 microg/g in the testis, and 0.014-0.018 microg/g in the cerebellum (gray matter, dentate nucleus, and white matter). The Se level in the kidney cortex was high, 4.6 microg/g, whereas the concentration detected in the other tissue samples was normal. Light microscopy of the cerebellum was normal, and no histochemical staining for mercury was observed. Autopsy samples from the referent showed low Hg and Se levels consistent with other reports.

CONCLUSIONS

The observed kidney-Hg, which was 50-100 times higher than that occurring in the general population, is in agreement with previous sparse data from ongoing occupational exposure. The high Se level detected in the kidney indicates coaccumulation with mercury. The low Hg concentration found in the cerebellum was unexpected, since some reports have shown much higher brain-Hg long after the cessation of exposure.

Cancer occurrence among European mercury miners

OBJECTIVES

To study the carcinogenicity of inorganic mercury in humans.

METHODS

We studied the mortality from cancer among 6784 male and 265 female workers of four mercury mines and mills in Spain, Slovenia, Italy and the Ukraine. Workers were employed between the beginning of the century and 1990; the follow-up period lasted from the 1950s to the 1990s. We compared the mortality of the workers with national reference rates.

RESULTS

Among men, there was no overall excess cancer mortality; an increase was observed in mortality from lung cancer (standardized mortality ratio [SMR] 1.19, 95 percent confidence interval [CI] 1.03-1.38) and liver cancer (SMR 1.64, CI 1.18-2.22). The increase in lung cancer risk was restricted to workers from Slovenia and the Ukraine: no relationship was found with duration of employment or estimated mercu ry exposure. The increase in liver cancer risk was present both among miners and millers and was stronger in workers from Italy and Slovenia: there was a trend with estimated cumulative exposure but not with duration of employment, and the excess was not present in a parallel analysis of cancer incidence among workers from Slovenia. No increase was observed for other types of cancer, including brain and kidney tumours. Among female workers (Ukraine only), three deaths occurred from ovarian cancer, likely representing an excess.

CONCLUSIONS

Exposure to inorganic mercury in mines and mills does not seem strongly associated with cancer risk, with the possible exception of liver cancer; the increase in lung cancer may be explained by co-exposure to crystalline silica and radon.

Urinary excretion of mercury, copper and zinc in subjects exposed to mercury vapour

The excretion of mercury, copper and zinc in urine, and mercury in whole blood and plasma, was determined in 40 chloralkali workers exposed to mercury vapour and 40 age-matched referents. The Hg concentrations in whole blood, plasma and urine were higher in the exposed group (35 nmol l-1, 30 nmol l-1, and 11.5 nmol mmol-1 creatinine, respectively) in comparison with the reference group (15 nmol l-1, 6.3 nmol l-1, and 1.8 nmol mmol-1 creatinine, respectively). The urinary copper excretion was similar in the two groups, while U-Zn excretion was significantly higher (P = 0.04) in the exposed group, median 0.83 mumol mmol-1 creatinine versus 0.76 munmol mmol-1 creatinine in the reference group. In a subgroup of exposed workers with current U-Hg above 11.5 nmol l-1 mmol-1 creatinine (20 micrograms g-1 creatinine) the median U-Zn was 1.1 mumol mmol-1 creatinine. In both groups smokers had high U-Zn levels than non smokers. When both U-Hg and smoking were taken into account in a linear regression model, there was a significant association between U-Hg and U-Zn in the combined group of exposed and referents (P = 0.002). This study indicates that mercury exposure in humans, as in animals, causes increased urinary excretion of zinc. The mechanisms may be induced synthesis of metallothionein in the kidneys, displacement of Zn from preexisting metallothionein by Hg, or a decreased reabsorption of zinc in the kidneys owing to a slight tubular dysfunction.

Exposure to mercury vapor and impact on health in the dental profession in Sweden

Possible adverse effects of mercury exposure in dentistry have been discussed in several studies. The objective of the present study was to carry out detailed measurements of mercury exposure in the dental profession in Sweden, and to search for adverse health effects from such exposure. We examined 22 dentists and 22 dental nurses, working in teams, at six Swedish dental clinics. Measurements of air mercury, performed with personal, active air samplers, showed a median air Hg of 1.8 micrograms/m3 for the dentists, and 2.1 micrograms/m3 for the dental nurses. Spot measurements with a direct reading instrument displayed temporarily elevated air Hg, especially during the preparation and application of amalgam. The average concentration of mercury in whole blood (B-Hg) was 18 nmol/L, in plasma (P-Hg) 5.1 nmol/L, and in urine (U-Hg) 3.0 nmol/mmol creatinine. Possible effects on the central nervous system (CNS) were registered with three questionnaires: Q16, Eysenck Personality Inventory (EPI), and the Profile of Mood Scales (POMS). In the Q16, the number of symptoms was statistically significantly higher in the dentistry group compared with an age- and gender-matched control group (n = 44). The urinary excretion of albumin and urinary activity of the tubular enzyme N-acetyl-beta-glucose-aminidase (NAG) did not differ between the two groups. The results confirm that exposure to mercury in the dental profession in Sweden is low. The air Hg levels were mainly influenced by the method of amalgam preparation and inserting, and by the method of air evacuation during drilling and polishing.

Polychlorinated dibenzo-p-dioxin and dibenzofuran levels and patterns in polyvinylchloride and chloralkali industry workers

The production of chlorine and vinyl chloride (VCM) is associated with the formation of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). The objective of the present study was to determine whether the levels and congener patterns of PCDDs and PCDFs in the blood of workers involved in the production of such substances could be related to their occupational environment. PCDD and PCDF levels in blood plasma from VCM and chloralkali workers and in referents were determined by means of high-resolution gas chromatography/high resolution mass spectrometry (HRGC/HRMS) techniques and the results were evaluated through principal component analysis (PCA). The overall levels of PCDDs and PCDFs were low, but the relative congener distribution detected in the workers differed from that found in the referents. 1,2,3,4,6,7,8-HpCDF, 1,2,3,4,7,8- and 1,2,3,6,7,8-HxCDFs are congeners related to work in VCM and chloralkali industries. Exposure to PCDDs and PCDFs in these industrial environments changes the congener-distribution pattern in the blood of workers as compared with referents. A combination of isomer-specific analysis of PCDDs and PCDFs in blood plasma and PCA is suitable for the differentiation between nonoccupational and occupational exposure and provides a means of assessing workers' exposure situation in different occupational settings.

Blood lead in Uruguayan children and possible sources of exposure

Blood samples and questionnaire background data were collected from 96 children (age 2-14 years) living in urban, suburban, or rural areas with varying traffic intensity and industrial lead pollution in Uruguay. Spot samples of tap water were collected from the homes of 44 children, and samples of top soil were taken from seven areas. Samples of air-borne dust were collected in central and suburban Montevideo. Blood lead concentrations (B-Pb) in children ranged between 47 and 191 (mean 96) micrograms/L and exceeded in 36% of the children 100 micrograms/L, the intervention level adopted by the United States Centers for Disease Control. Lead in tap water ranged from 0.2 to 230 (mean 15) micrograms/L and exceeded in 39% of the samples the maximum level recommended by WHO, 10 micrograms/L. Lead pipes were used in parts of the water supply systems. Lead in air varied between different locations from 0.15 to 1.7 micrograms/m3, highest in the very center of Montevideo. The median soil lead ranged from 6 to 2100 micrograms/g and was highest in industrially polluted areas. At multiple regression analysis, B-Pb was significantly associated only with age (P = 0.032) and traffic intensity at school (P = 0.045). No significant impact on B-Pb of lead in water or soil could be established.

Dose-dependent elimination kinetics for mercury in urine: observations in subjects with brief but high-level exposure

OBJECTIVES

To study the elimination kinetics for mercury in urine (U-Hg) after brief but high-level exposure.

METHODS

U-Hg was examined in 11 workers after 2-10 days of exposure to inorganic Hg and after symptoms and signs of Hg intoxication had appeared. Initial U-Hg excretion varied between 60 and 2360 micrograms/g creatinine. The subjects were followed up for 1-11 months. In each subject, one- and two-compartment models were fitted to the U-Hg values, assuming an exponential decrease, by weighted non-linear least-squares regression (weight = 1/U-Hg).

RESULTS

The data indicated two elimination phases in subjects with initial U-Hg above 600 micrograms/g. In the two-compartment models, there was a fast phase with a half-time of 2-16 days, and a slow phase with a half-time of more than a month. The fast phase contributed 70-90% to the sum of the Y intercepts.

CONCLUSIONS

The kinetics of U-Hg excretion after cessation of exposure seems to be dose-dependent and, at least in certain cases, to have two phases. The explanation for the fast phase may be that the capacity of certain binding sites in the kidney was exceeded.

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.

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.

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.

Respiratory symptoms and asthma among workers exposed to paper dust: a cohort study

The aim of the present cohort study was to investigate whether exposure to paper dust causes increased risk for respiratory symptoms or asthma. The cohort included all workers at a soft paper mill who had worked there for more than 1 year 1960-1986 (n = 1,697). Randomly selected inhabitants of the mill town (n = 781) were used as unexposed referents. Both groups were investigated using a postal questionnaire. From the paper mill cohort, workers with high cumulative exposure (n = 313), with medium cumulative exposure (n = 321), and with low cumulative exposure (n = 338) to paper dust were selected. In the 1960s and 1970s, the dust levels were between 5 and 10 mg/m3. After adjustment for smoking and gender, paper dust exposure resulted in elevated prevalence ratios for chronic cough, chronic phlegm, wheeze, and breathlessness. The prevalence ratios ranged from 1.3 to 2.5. No significantly increased risk of asthma was found among the exposed, incidence rate ratio 1.4 (95% confidence interval 0.93-1.8). Among the exposed, there was an insignificantly increasing incidence rate ratio, 1.0, 1.4, 2.1, with increasing cumulative exposure. In conclusion, an increased risk for respiratory symptoms was observed among workers exposed to paper dust, but the study does not permit any definite conclusions regarding asthma and paper dust exposure.

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.

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.

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.

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.

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.

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.

Mobilized mercury in subjects with varying exposure to elemental mercury vapour

In a mercury mobilization test, 0.3 g of the complexing agent sodium 2,3-dimercaptopropane-1-sulfonate (DMPS) was given orally to 10 workers with moderate occupational exposure to elemental mercury vapour, to 8 dentists with slight exposure, to 18 matched controls, and to 5 referents without amalgam fillings. In the workers, DMPS caused an increase in 24-h urinary mercury excretion by a factor of 10; in the dentists, 5.9; in the controls, 5.3; and in the amalgam-free referents, 3.8. Of the mercury excreted during 24 h, 59% appeared during the first 6 h. Close, albeit non-linear, associations were found between mobilized mercury and the premobilization mercury levels in plasma and urine, but not with the duration of occupational exposure or the rough estimate of the integrated function of blood levels vs time. The present data indicate that mercury mobilized after a single DMPS dose in close connection with exposure is mainly an index of recent exposure and is not significantly affected by slow body pools or long-term exposure.

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.

Mortality from asthma, chronic obstructive pulmonary disease, respiratory system cancer, and stomach cancer among paper mill workers: a case-referent study

In an earlier case-referent study from a soft-paper mill with levels of paper dust exceeding 5 mg/m3, an increased mortality was found (OR = 3.8, p less than 0.05) from asthma and chronic obstructive pulmonary disease (COPD) among the employed. Furthermore, other studies on paper mill workers have also indicated an increased mortality from lung cancer. The main objectives of the present case-referent study were to investigate the mortality from asthma. COPD, and lung cancer in two other Swedish paper mills. In these mills, the levels of paper dust have been below 3 mg/m3. The subjects for the study were all men who died between 1961 and 1985 from asthma and COPD (n = 31), respiratory cancer (n = 27), and stomach cancer (n = 33) selected in three parishes surrounding two paper mills. As referents we randomly selected about six times as many men who had died from nonmalignant nonrespiratory diseases in these parishes (n = 550). On the basis of information found in the personnel records in the mills, the men were classified into different occupational categories or as unexposed. No increased risk of asthma or COPD was found among the workers exposed to paper dust. However, it was found that there was significantly increased mortality (OR = 5.7, p less than 0.05) for asthma and COPD among workers in a previous log sorting department. The study also showed a significantly increased risk of lung cancer (OR = 2.1, p less than 0.05) among maintenance workers. There was no increased risk of stomach cancer in the study.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

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.

Characterization of airborne dust in a soft paper mill

The characteristics of airborne dust in a soft paper production plant have been characterized by scanning and transmission electron microscopy. A combination of X-ray diffraction, electron diffraction and energy-dispersive X-ray flouresence spectroscopy (EDX) was used to determine the structure and composition of the different components. Size distribution determination and phase identification were carried out. Besides the cellulose fibres, fibres of kaolinite, wollastonite, talc and other silicates were also identified. Gravimetric analysis and fibre counting by optical phase contrast microscopy were used to determine total dust and fibre concentrations. Total dust exposure at the plant was generally below 3 mg m-3. The respirable fraction of the total dust concentrations varied from 15 to 70%. The inorganic dust was 36 +/- 15% of the total dust. The ratio of inorganic fibres to total fibre concentration at the plant varied between 10 and 15%.

Lung function and respiratory symptoms among workers in a soft paper mill

The aim of the present cross-sectional study was to investigate whether long-term exposure to soft paper dust causes impairment of lung function. Exposed workers (n = 287) and referents (n = 79) were investigated, using spirometry and questionnaires. Personal samplings of total dust showed that the actual mean concentrations did not exceed 3 mg/m3. The exposed subjects were divided into three categories according to historical and present exposure to paper dust; low exposure, moderate exposure and high exposure. The study did not show any lung function impairment due to exposure to paper dust. However, the exposed subjects had a significantly increased prevalence of symptoms from both the upper and lower airways as well as an increased prevalence of reported asthma. On the basis of our study, we conclude that lung function impairment does not occur among workers exposed to mean levels of soft paper dust below 5 mg/m3.

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.

Pleural mesotheliomas and asbestos exposure in the pulp and paper industries: a new risk group identified by linkage of official registers

Analysis of data obtained by linking the 1960 Swedish Census and the Swedish Cancer Registry has demonstrated an increased risk of pleural mesothelioma among pulp and paper workers. The present study was undertaken with the aim of revealing possible environmental risk factors. The work histories of the 25 cases identified earlier were reviewed. "Certain" or "probable" exposure to asbestos was found among 70% of these workers. The study illustrates how linkage of official registers can be used to identify new risk environments and encourage the establishment of preventive measures.

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.

Cancer morbidity among men exposed to oil mist in the metal industry

The cancer morbidity pattern among 788 men with at least five years' exposure to oil mist was investigated. Based on measurements, interviews of workers and a survey of changes over the years, the average exposure level was estimated to have been 5 mg/m3 or more prior to 1965. Exclusive of cancer of the scrotum, there were 39 observed cases of cancer compared to 52.9 expected. There were four cases of cancer of the scrotum among the turners but none among the grinders. Three cases of lung cancer were found, compared to 5.4 expected. Among the grinders there was a doubled, but not statistically significant, increase in cancer of the stomach. The mortality from all causes showed a so-called "healthy worker effect," that is, 126 deaths compared to 154.3 expected.

Method of the cohort study--a practical example

The method is demonstrated in connection with a study of lung cancer among metal-workers exposed to oil mist. As exposure to oil mist is uncommon and lung cancer is common, the cohort study is the method of choice. Estimation of exposure, problems of selection, calculation of person-years etc is discussed. There was no increased morbidity from lung cancer.