Pleural plaques and exposure to asbestos: a mathematical model.

The objective of this study was to find a model to describe the relationship between the occurrence of pleural plaques and exposure to asbestos. A simple model based on the cumulative exposure was postulated and empirically tested on shipyard workers occupationally exposed to asbestos. Exposure time was used to approximate the cumulative dose. It was found that the incidence of pleural plaques could be described as K(t-w)a where 't' is time since onset of exposure; 'K' is a constant that would depend on the level of asbestos exposure; 'w' is a latency period and was around 13 years; 'a' is a constant that was 0.4. In subgroups of the workers, i.e. plumbers, fitters and platers, 'a' was 0.4, 0.6 and 0.2 respectively.     

Pleural mesothelioma and environmental exposure to mineral fibres: the case of a rural area in the Basilicata region, Italy

The main aspects of the sites characterized by environmental exposure to mineral asbestiform fibres are described. Several adverse health effects including high incidence of pleural mesothelioma are reported. The average concentration of airborne fibres is generally low but it rises significantly in association with mechanical disturb of materials with fibres. Multiple sources of exposure have been identified, fibres can be found in the soil and in many materials locally used, mainly in buildings. Three mesothelioma cases were observed in a small rural area of the Basilicata region (Italy). Two of them had a possible occupational exposure to asbestos, the third had a proved environmental exposure to tremolite. This fibre, found in the area, is the same observed in two of the three biological samples analysed.     

Occurrence of pleural plaques in workers with exposure to mineral wool

The objective of this study was to investigate whether occurrence of pleural plaques is associated with exposure to mineral wool. The occurrence of pleural plaques on routine chest radiographs of 933 persons employed in the mineral wool manufacturing industry and 865 referents was compared. Twelve men from the mineral wool industry had pleural plaques, as against three of the referents (P > 0.05). The occurrence of pleural plaques among men in the mineral wool industry was not associated with an increased exposure to mineral wool or with length of time between start of employment and time of chest radiograph. The results do not support the notion that inhalation of man-made mineral fibers causes pleural plaques. It must, however, be conceded-keeping in mind the limits imposed by the study size-that nor do they provide grounds for refutation of such a hypothesis.     

Ferruginous body counts in sputum as an index of past exposure to mineral fibres.

Previous work by our group among vermiculite miners exposed to fibrous tremolite demonstrated that asbestos body counts in sputum closely reflected intensity and duration of past exposure. In the present project sputum samples from nearly 600 volunteers from 11 cohorts of workers exposed to asbestos and other mineral fibres were found to contain much lower numbers of asbestos bodies than had been observed in vermiculite workers and these counts did not reliably reflect past levels of exposure. No evidence was found that occupational exposure to man-made mineral fibres led to any ferruginous body formation. Asbestos body counts appeared to differentiate between mesothelioma cases and controls and between levels of radiological asbestosis, but in both comparisons, based on small numbers, the power of discrimination was low. Substantial variation was found both in asbestos body and in macrophage counts in daily sampling of vermiculite workers but it was not sufficient to invalidate comparison between groups for epidemiological study. In individual subjects, however, little reliance can be put on results from a single sputum sample, particularly if negative.     

Pleural abnormalities and exposure to elongate mineral particles in Minnesota iron ore (taconite) workers

Background

Iron ore (taconite) mining and processing are an important industry in northern Minnesota and western Michigan. Concerns around exposures have centered largely on exposure to non‐asbestiform amphibole elongate mineral particles (EMPs) found in the eastern portion of the Minnesota iron range.

Methods

A cross sectional survey was undertaken of current and former taconite workers and spouses along with a detailed exposure assessment. Participants provided an occupational history and had a chest radiograph performed.

Results

A total of 1188 workers participated. Potential exposures to non‐amphibole EMPs were evident across multiple jobs in all active mines. Pleural abnormalities were found in 16.8% of workers. There was an association of pleural abnormalities with cumulative EMP exposure that was not specific to the eastern portion of the range.

Conclusion

There was evidence of a mild to moderate increase in pleural abnormalities in this population of miners, associated with geographically non‐specific cumulative EMP exposure.

     

Diachronic study of pleural plaques in rural population with environmental exposure to asbestos

BACKGROUND: The progress of pleural plaques in persons exposed to environmental asbestos in Almopia, Greece were studied prospectively. METHODS: During a 15-year period, 198 individuals, in whom pleural plaques had been observed during the period 1988-1990 were followed. Respiratory function was initially evaluated in 23. All were inhabitants of seven villages of Northern Greece, where rocks with high concentration in asbestos fibers were used for whitewashing until 1935. RESULTS: Out of this population, 126 survived and underwent chest X-ray in 2003 while respiratory function was retested in 18. New radiological findings were compared to previous ones using digital technology. Furthermore, the cause of death of the remaining 72 was recorded. Deterioration of X-ray findings was observed in all survivors. Not only did the surface area of previous plaques increase (8.66 +/- 12.6 cm2, mean value +/- SD) but new ones also appeared. Total lung capacity decreased from 95.6 +/- 14.8 in 1998 to 76.5 +/- 9.3% predicted in 2003. It was found that out of 72 deaths, 11 people died of malignant lung neoplasm, and 4 of mesothelioma. CONCLUSIONS: Radiological appearance of pleural plaques and respiratory function of people previously exposed to asbestos environmental pollution worsens over the years. Prevalence of mesothelioma was found to be higher than expected.     

Binding of environmental carcinogens to asbestos and mineral fibres.

A rapid method has been developed for measuring the binding capacity of asbestos and other mineral fibres for environmental carcinogens. Benzo(alpha)pyrene (B(alpha)P), nitrosonornicotine (NNN), and N-acetyl-2-aminofluorene (NAAF) were assayed in the presence of Canadian grade 4T30 chrysotile, chrysotile A, amosite, crocidolite, glass microfibres, glasswool, attapulgite, and titanium dioxide. Chrysotile binds significantly more carcinogens than the other mineral fibres. This binding assay is reproducible with coefficients of variation of less than 8% and 6% respectively for inter and intra assay. The influence of pH was also studied, and there is good correlation between the carcinogen binding and the charge of the tested mineral fibres. The in vitro cytotoxicity on macrophage like cell line P388D1 and the haemolytic activity of various mineral fibres were also measured; a good correlation was found between the binding capacity and the cytotoxicity of tested mineral fibres on P388D1 cells. These results give some explanations for the reported synergism between exposure to asbestos and the smoking habits of workers.     

Biomarkers of manganese exposure in a population living close to a mine and mineral processing plant in Mexico

Manganese (Mn) is considered an essential metal; nevertheless, excessive Mn exposure in humans is known to affect central nervous system. Mn access to its toxic target, the brain, is a complex phenomenon subject to physiological and physiopathological processes; in which, among others, the route of exposure plays an important role. Mn airborne exposure has gained interest both in occupational and environmental studies in order to understand the effects of low-level, long-term exposure. The objective of the present study was to describe the relationship between blood Mn and prolactin as marker of effect exposure, as well as other variables from subjects dwelling in a mining district in central Mexico environmentally exposed to the metal. This study was conducted on 230 volunteers; blood samples were obtained from cubital vein and hemoglobin, prolactin, lead (Pb), and Mn levels were measured. Non-parametrical Spearman's correlation showed statistical associations between blood and Mn levels and prolactin (rho=0.197), hemoglobin (rho= -0.213), age (rho= -0.186), and blood lead (rho= -0.167). Multiple regression analysis showed that blood Mn levels as an important factor to determine serum prolactin levels (beta=0.111, p=0.029) in a model corrected by gender and age. Results suggest that assessment of Mn exposure by biomarkers on general population is complex due to the variability and characteristics of the metal; however, specific subpopulations such as iron-deficient individuals are suspected to accumulate Mn in blood and thus they may be susceptible to the neurotoxic effects of Mn.     

Correlates of exposure to second-hand smoke in an urban Mediterranean population

Background  

To describe the socio-demographic factors associated with exposure to second-hand smoke (SHS) in different settings (home, leisure, and workplace).     

Influence of environmental lead on membrane ion transport in a French urban male population.

Red cell cation transports (Na(+)-K+ pump, Na(+)-K+ cotransport system, Na(+)-Li+ countertransport, and Na+ and K+ passive permeabilities) and blood and hair lead levels were measured in 129 healthy adult Caucasians not occupationally exposed to lead. In agreement with previously reported in vitro results showing a lead-induced Na(+)-K+ ATPase inhibition, Na(+)-K+ pump activity was inversely correlated with hair lead (r = -0.18, P less than 0.05); it was not significantly correlated with blood lead. Na(+)-K+ cotransport activity was inversely correlated with blood lead contents (r = -0.23, P less than 0.05) but not with hair lead. No significant correlation was found between the remaining cation transport pathways and lead levels. It is hypothesized that environmental, long-term exposure to lead may result in pump inhibition, while a recent exposition to lead may result in inhibition of the Na(+)-K+ cotransport system. Further research is required in order to determine if red cell Na(+)-K+ pump and Na(+)-K+ cotransport activities are sensitive indicators of chronic and recent exposures to lead, respectively.     

Cadmium exposure pathways in the Czech urban population

The article describes the exposure pathways of cadmium in the Czech urban population. The data on Cd concentrations originated from the Environmental Health Monitoring System, which has been realized in 30 cities since 1994. The data on cadmium content in particular exposure pathways - diet, drinking water, ambient air and soil -were processed for the period 1994-2003. The estimate of the daily dietary intake for an average adult population amounted to 11-19 microg/d, i.e. 0.17-0.30 microg/kg bw/d, which represents 17%-30% of the PTWI (provisional tolerable weekly intake). The contribution from drinking water to the oral exposure is low; on average 0.5 microg/d. Potential exposure to airborne Cd was estimated at about 0.02 microg/d. The additional Cd intake from urban soil ingestion probable in small children was found to be insignificant based on Cd concentrations in the soil of kindergarten playgrounds. Biomonitoring outputs characterize the recent and life-long cadmium burden of the Czech population from general environment In 1994-2003, the median blood Cd levels ranged in the interval 0.9-0.4 microg/l blood, in smokers being more than double that in non-smokers. Blood Cd levels detected indicate slightly decreasing trend as well as urine Cd levels (range of median values 0.44-0.28 microg/g creatinine). Since 1996 the levels in children have been found in more than 50% cases below the detection limit of the methods used. The estimated total cadmium intake in the Czech urban population does not signalize any increased risk of health impairment considering non-carcinogenic effects.     

Irritative symptoms and exposure to mineral wool.

In a cross-sectional study undertaken in 1981 using a postal questionnaire, the prevalence of irritative symptoms was investigated among 2,654 Danish construction workers working with mineral wool. An evaluation was undertaken in a multivariate logit analysis of the relationship between exposure level (measured by hours of exposure to mineral wool per month) and prevalence of symptoms. The analysis controlled for the confounders of age, smoking habits, and exposure to organic solvents. With greater exposure to mineral wool, there was a statistically significant increase in the frequency of irritative symptoms from the eyes, the skin, and the upper respiratory tract. Among construction workers working with mineral wool 160-180 hours per month, two-thirds had these symptoms once a week or oftener. The occurrence was 2-3 times higher compared with the construction workers not working with mineral wool. The relationship between exposure to mineral wool and skin and mucous membrane symptoms may be explained by the irritative action of the fibers that are given off during insulation work.     

Value of mortality data and necropsy records in monitoring morbidity in a population.

STUDY OBJECTIVE--The aim was to compare the value of four sources of data in assessing morbidity in a population: (1) data from a screening programme including follow up records, (2) death certifications by attending physicians, (3) death certifications by doctor-coroners, and (4) necropsy reports. DESIGN--The study was a cohort analysis of health and mortality in a sample of agricultural workers first examined in 1964-66 when they were aged 60 years or older. Follow up examinations enabled morbidity assessment to be made and ICD diagnostic categories to be compared with data available on persons in the cohort who had died. SETTING--Hajdúszoboszló, a small town in eastern Hungary. PARTICIPANTS--1412 persons (96.1% of those aged greater than or equal to 60 years) were examined in 1964-6. Those still alive and available in 1989 were examined again. Necropsy records were available for 144 persons from the cohort in 1989 and were extensively reviewed in comparison with data available from other sources. MEASUREMENTS AND MAIN RESULTS--Comparison of causes of death established at necropsy showed marked differences from those registered by attending physicians and doctor-coroners, deviations ranging from -91.6% to +74.8%; 19.4% of underlying causes of death occurred exclusively in the necropsy group. Major divergencies in diagnostic classification occurred in the three data sources, particularly for diseases of the circulatory system, where hypertensive renal disease, old myocardial infarction, acute cerebrovascular disease, and venous thrombosis were rarely documented by physicians/coroners. When necropsy data were used the number of diagnostic categories increased strikingly over the other sources of information. Necropsy records revealed quantitatively similar information on morbidity to follow up examination though there were qualitative differences, necropsy being less likely to document diagnoses of endocrine disorders, mental and neurological diseases, digestive disorders, and musculosketal disorders. CONCLUSIONS--Necropsy records contain much valuable material not available from other sources, exceeding by ninefold the amount of information reported at present. A way should be found to make use of this large data pool.     

Silica exposure, silicosis, and lung cancer: a necropsy study.

Recent studies of the association between lung cancer and silicosis and silica dust have been inconclusive; some showing positive association and some showing none. The present study matched 231 cases of lung cancer with 318 controls by year of birth. Subjects were selected from the necropsy records of the National Centre for Occupational Health. Data on intensity and duration of exposure to silica dust were obtained from personnel records. Presence or absence of lung cancer and the presence and severity of silicosis of the parenchyma, pleura, and hilar glands were documented from necropsy reports. Smoking data were abstracted from records of routine examinations. No case-control differences were noted for any of the exposure indicators including cumulative dust exposure, total dusty shifts, weighted average intensity of exposure, total underground shifts, and shifts in high dust. Similarly, no association was found between lung cancer and the presence or severity of silicosis and any site. Stratified analyses showed neither significant nor suggestive trends when case-control comparisons for silicosis were examined by level of dust exposure or smoking. Reasons for disparity between these results and those of some other studies may include concomitant exposures to radon daughters, asbestos, diesel emissions, and cigarette smoking; idiosyncracies of the compensation process; and the possibility of a threshold in the relation(s).