Laryngeal cancer and occupational exposure to asbestos

Summary The risk of laryngeal cancer associated with occupational exposure to asbestos was evaluated by a review of published reports. In only two of 13 cohort studies was the standardized mortality ratio (SMR) significantly increased. Smoking (a risk factor for laryngeal cancer) may have been more prevalent among asbestos workers than among the comparison populations. This was not taken into account in any of the studies, and may have caused the SMRs to be overestimated. Two of eight case-control studies reported large odds ratios ( 13) for laryngeal cancer. Subsequent case-control studies did not confirm this higher risk; the odds ratios in these studies were 0.3 to 1.9. The conclusion of the review, based on data from 13 cohort and 8 case-control studies, is that neither case-control nor cohort studies have established an increased risk of laryngeal cancer for asbestos workers.     

Past occupational exposure to asbestos among men in France

OBJECTIVES: This study aimed at reconstructing changes in the frequency and levels of occupational asbestos exposure in France over the past century. METHODS: Work histories were collected during 11 population-based case-referent studies recently carried out in France, and an asbestos-specific job-exposure matrix including 10 625 jobs was used to estimate indices of past occupational asbestos exposure. The results were estimated from a sample of 4287 subjects, bootstrapped 200 times. RESULTS: The distribution of socioeconomic categories within the sample was compared with that of the general population in 1954, 1962, 1968, 1975, and 1982. The proportion of blue-collar workers was similar. The highest proportion of exposed subjects was found between 1950 and 1980. Around 10% of each 10-year age class was exposed to asbestos. For those born in 1930-1939, 15.2% was exposed between the ages of 20 and 29 years. For each age class born in 190-1939, the proportion exposed at least once by 60 years of age ranged from 18.2% to 24.5 % and, of those exposed, the cumulative duration of exposure ranged from 11.3 to 15.4 years by the age of 60 years. A population exposure index showed that the heaviest exposure occurred between 1960 and 1970 and that the age classes born between 1920 and 1929 were the most heavily exposed. Time trends showed that the mean value of this index for the men aged 20-59 years reached a peak in the 1960s and then decreased. CONCLUSIONS: This study presents data of reasonable validity about occupational asbestos exposure in France and its trends over the past century; the data are being used to forecast the development of male mortality from mesothelioma in France.     

200 kV xeroradiography in occupational exposure to silica and asbestos

Some details of the physics of xeroradiography, and the bearing these have on films of the lung obtained by this technique, are discussed. In experiments designed to obtain useful films with a minimum of radiation exposure it was found that an exposure range of 10-30 mas at 200 kV at 1.35 m (4 1/2 ft) without a grid or air gap gave very satisfactory results. The positive model of development was considered to give more information than the negative mode. One hundred and fourteen miners who had been exposed to silica dust, asbestos dusts or both, were examined by this technique. The xeroradiographs were compared with silver halide films taken at 200 kV. The xeroradiographs were considered to be superior in several respects, especially in the delineation of vascular shadows, normal and abnormal linear opacities. Linear opacities in asbestos-exposed subjects were better shown on the xeroradiographs and were occasionally seen on these films when the 200 kV conventional film was entirely normal. Small rounded opacities of silicosis were very poorly shown on the xeroradiographs. Pleural thickening and pleural plaques may be very well demonstrated.     

Screening of autopsy populations for previous occupational exposure to asbestos

A screening procedure to select, in autopsy populations, subjects having a major likelihood of previous occupational exposure to asbestos is described. To test our necropsy population we searched for pleural plaques (PPs); the optical count of both lung asbestos bodies (ABs) and uncoated mineral fibers (UMFs) at least 10 microns in length was recorded. In the adult autopsy population studied in the Turin area, the predictive value given by a positive test for large-size PPs (mostly bilateral) was about 55%. This level of probability did not rise in relation to the AB counts, whereas an increase to over 75% was observed if more than 10,000 UMFs/g dry lung were present. In subjects without PPs or with small-size plaque lesions (mostly unilateral), predictive values of positive tests were 20 to 30% when ABs and UMFs were found to be below 100 and 10,000/g, respectively, and increased to approximately 40% if the AB count exceeded 500/g and to almost 70% for an UMF count above 100,000/g. In subjects without PPs or with small-size plaque lesions, the probability of being nonexposed was greater than 90% if neither ABs nor UMFs were found. This autopsy screening may be a reliable tool in selecting cases most probably related to occupational exposure.     

B cell neoplasms and occupational asbestos exposure

To evaluate the etiologic role of asbestos exposure in B cell neoplasms, we compared the estimated level of occupational exposure to asbestos of cases with chronic lymphocytic leukemia (CLL; N = 429) and multiple myeloma (MM; N = 698) with that of controls (N = 1,683). Cases were identified through four population-based cancer registries in the U.S. and controls were randomly selected from the same geographic areas. Exposure to asbestos was assessed by classifying each job held by a subject into one of four categories, based on the estimated intensity of exposure to asbestos. Evidence was found for a modest increasing risk of CLL with increasing asbestos exposure. Relative to persons with no known occupational exposure to asbestos, the risk for CLL was 1.1 (95% confidence interval (CI) = 0.8-1.6) for low, 1.2 (CI = 0.8-1.8) for medium, and 1.4 (CI = 0.8-2.3) for high peak asbestos exposure (p value for trend = 0.13). The association was strongest in white study subjects and in those individuals exposed 10 to 19 years prior to the interview. No association was observed between MM and occupational exposure to asbestos in the entire study population or within specific subgroups. Given the pattern of immunologic abnormalities that occur with increased frequency in asbestos-exposed persons, our observation of an association between occupational asbestos exposure and CLL deserves attention in subsequent studies.     

A review of environmental and occupational exposure to asbestos in Israel

The case for a total ban on manufacture and use of asbestos products is stated by the history of asbestos use, exposures, and risks in Israel. Manufacture and use of asbestos began in Israel in the 1950s, rising to a peak in the mid-1970s, and dropping gradually thereafter until reaching minimal levels in the 1990s. Following heightened public concern regarding the carcinogenic effects of asbestos products, there were reductions in use, manufacture, and persons exposed. Since the 1960s, asbestos-related diseases have been diagnosed in hundreds patients nationwide, including asbestos workers and users, as well as individuals living proximally to the manufacturing facilities. Exposures to asbestos in place remain, and patients with asbestos-related disease from environmental exposure are expected to appear for at least another 20-30 years. In the 1980s, an advisory committee appointed by the Ministry of Health of Israel outlined a comprehensive approach towards prevention, control, management, and compensation for health risks from asbestos exposures. As certain areas are still contaminated with asbestos waste and as environmental exposure persists, continued and improved medical monitoring and compensation programs are urgently needed in order to reduce the suffering of exposed individuals and their families. The ban on asbestos prevents risks from new exposures, but does not undo the damage from past manufacture, use, disposal, and dumping. In this paper, we review the history of Israel's import and use of asbestos, and the management of occupational and environmental exposures. We also address policy, practice, and the need to protect future victims of asbestos-related disease.     

200 kV xeroradiography in occupational exposure to silica and asbestos.

Some details of the physics of xeroradiography, and the bearing these have on films of the lung obtained by this technique, are discussed. In experiments designed to obtain useful films with a minimum of radiation exposure it was found that an exposure range of 10-30 mas at 200 kV at 1.35 m (4 1/2 ft) without a grid or air gap gave very satisfactory results. The positive model of development was considered to give more information than the negative mode. One hundred and fourteen miners who had been exposed to silica dust, asbestos dusts or both, were examined by this technique. The xeroradiographs were compared with silver halide films taken at 200 kV. The xeroradiographs were considered to be superior in several respects, especially in the delineation of vascular shadows, normal and abnormal linear opacities. Linear opacities in asbestos-exposed subjects were better shown on the xeroradiographs and were occasionally seen on these films when the 200 kV conventional film was entirely normal. Small rounded opacities of silicosis were very poorly shown on the xeroradiographs. Pleural thickening and pleural plaques may be very well demonstrated.     

Effect of respiratory protective equipment on exposure to asbestos fibres during removal of asbestos insulation

Asbestos concentrations were measured within powered respirators used by workers involved in the removal of asbestos-containing insulation. Fibre concentrations within the protective gear appeared to be above the Dutch threshold limit value for crocidolite (0.2 f cm-3). Possible sources of exposure were analysed and measures were taken to improve the situation. After this, the fibre concentrations in the breathing area were reduced and were below the Dutch concentration limit.     

Trends in occupational asbestos exposure and asbestos consumption over recent decades in Korea

In Korea, national statistics for asbestos exposure levels covering various asbestos industries and associated with specific years have never been published. The authors analyzed 2,089 asbestos exposure data sets compiled from 1995 through 2006. Exposure levels were characterized according to type of asbestos industry and year. Asbestos exposure levels have decreased over time, dropping sharply from 0.92 fibers/cc (f/cc) in 1996 to 0.60 f/cc in 1997, to 0.19 f/cc in 1998, and to 0.06 f/cc in 1999, possibly in part because of enforcement of 1997 legislation banning the use of amosite and crocidolite. In particular, a substantial reduction in asbestos exposure levels was most evident among primary industries handling raw asbestos directly. A similar relationship was found between a significant decline in asbestos consumption volume and the timing of regulation enforcement.     

Role of occupational asbestos exposure in Hungarian lung cancer patients

Objective: What is the frequency of occupational asbestos exposure among patients suffering from malignant respiratory tumours and how many of these tumours are associated with asbestos in Hungary? Methods: An internationally established questionnaire with 29 questions, covering the most characteristic activities of asbestos exposure at the workplace was completed for 300 patients with respiratory malignancies, i.e. 297 patients with lung cancer and three with mesothelioma of the pleura. From the questionnaire, the smoking habits were estimated and cumulative asbestos exposure was assessed in fibre-years. Additionally, lung X-rays were classified and the national data on the incidence of malignant pleura mesothelioma were analysed. Results: A cumulative asbestos exposure of 25?fibre-years or more was detected in 11 patients with lung cancer (4%) and in each of the three patients with pleural mesothelioma (100%). In a further 72 patients (24%), cumulative occupational asbestos exposure was assessed as below 25?fibre-years (between 0.01 and 23.9?fibre-years). In this group, car and truck mechanics, and installation and construction workers using asbestos-cement were registered. Among patients with an asbestos exposure of 25?fibre-years or more, six asbestos-cement production workers were observed, among them the three mesothelioma cases. A weak but significant association between positive X-ray findings and exposure estimates could be demonstrated. Additionally, results of the lung tissue fibre counts by scanning transmission electron microscopy were available for 25 of the lung cancer patients. A good correlation was observed between the asbestos fibre counts and the assessment of cumulative asbestos exposure. In Hungary, 84 cases of pleural mesothelioma were registered in 1997 and 73 in 1998. These numbers correspond to an annual incidence of about one new case per 100,000 inhabitants older than 15?years. Conclusions: The annual incidence of lung cancer in Hungary is about 6,000. Since in our series of lung cancer patients about 4% were observed, which could be accepted as representing occupational disease because of a cumulative exposure to 25?fibre-years or more, the annual asbestos related lung tumour incidences may be estimated to be approximately 150 or more. The proportion of nearly two estimated cases of lung cancer per case of pleural mesothelioma corresponds to international experience. Up to now, lung cancer cases only exceptionally have been registered as occupational diseases, i.e. they were seriously under-diagnosed in Hungary. For improving this situation, diagnostic assistance by a self-interview with a questionnaire covering the working history for all newly diagnosed lung cancer patients would be helpful.     

Simulation tests to assess occupational exposure to airborne asbestos from asphalt-based roofing products

This study sought to evaluate exposure from specific products to evaluate potential risk from roof repair activities. Five asbestos-containing fibered roof coatings and plastic cements, representing a broad range of these types of products, were tested in exposure simulations. These products were applied to representative roof substrates. Release of asbestos fibers during application and sanding of the product shortly thereafter (wet sanding) were tested initially. Other roof substrates were cured to simulate a product that had been on a rooftop for several months and then were tested to evaluate release of fibers during hand sanding and hand scraping activities. Additional tests were also conducted to evaluate asbestos release during product removal from tools and clothing. Two personal (n = 84) and background/clearance (n = 49) samples were collected during each 30-min test and analyzed for total fiber concentration [phase-contrast microscopy (PCM)] and for asbestos fiber count [transmission electron microscopy (TEM)]. PCM concentrations ranged from <0.005 to 0.032 fibers per cubic centimeter (f cc(-1)). Chrysotile fibers were detected in 28 of 84 personal samples collected. TEM concentrations ranged from <0.0021 to 0.056 f cc(-1). Calculated 8-h time-weighted averages (TWAs) ranged from 0.0003 to 0.002 f cc(-1) and were comparable to the background TWA concentration of 0.0002 f cc(-1) measured in this study. Based on these results, it is unlikely that roofers were exposed to airborne asbestos concentrations above the current or historical occupational guidelines during scraping and sanding of these products during roof repair.     

Absence of amosite asbestos in airway mucosa of non-smoking long term workers with occupational exposure to asbestos.

There is considerable experimental evidence that asbestos fibres are taken up by epithelial cells, and that uptake of fibres is associated with various deleterious, particularly mutagenic, effects. It is not known, however, if asbestos fibres are taken up by human bronchial epithelial cells in vivo. To investigate this question, the amosite asbestos content of the mucosa of seven different airways and four parenchymal sites supplied by these airways in six necropsy lungs from heavily exposed never-smoking long term shipyard and insulation workers without asbestosis was examined. Amosite asbestos was readily found in moderately high concentration in all parenchymal samples, but 33 of 40 airway samples that could be evaluated showed no amosite fibres. The seven positive airways had fibre concentrations that were always much lower than the parenchymal concentrations, and these very few fibres may have been contaminants from the parenchyma. These data suggest that, at least in non-smokers, amosite asbestos either does not penetrate into or does not accumulate in human airway mucosa. These findings also call into question the idea that asbestos acts as a direct airway carcinogen in humans.     

Urinary hippuric acid concentration after occupational exposure to toluene.

The results of industrial investigations have shown a correlation between the rate of hippuric acid excretion in a single urine sample collected after daily occupational exposure and the amount of toluene absorbed. The rate of hippuric acid excretion and the average concentration of toluene vapour during exposure time were also related. The quantitative range of the test has been limited to amounts exceeding 425 mg of toluene and concentrations exceeding 69 ppm of toluene in the air because of the physiological presence of hippuric acid in urine. The rate of hippuric acid excretion in urine depends on diuresis and is constant for urinary fractions with diuresis of 30 ml/h. The physiological excretion rate was 20 mg/h with a standard deviation +/- 4.3 mg/h, maximal physiological level 33 mg/h.     

Use of a job-exposure matrix for the screening of occupational exposure to asbestos

BACKGROUND: According to a recent French legislation (1995), retired people who have been exposed to an occupational carcinogen can benefit from a specific post-occupational medical follow-up program, supported by the "Caisse Primaire d'Assurance-Maladie" (CPAM), the French health insurance system. However, only very few people presently take access to this social measure. The ESPACES project developed and evaluated a procedure to identify retirees who have been exposed to asbestos during their career, and to inform them about the post-occupational medical follow-up program. METHODS: This pilot study was performed within the health centers ("Centres d'examens de santé" (CES)) of the health insurance system in a random sample of men who have retired from the six main French administrative divisions between 1994 to 1996. A probability of exposure to asbestos was attributed through a job exposure matrix. Subjects were interviewed in the CES to validate their exposure data. Retired subjects with confirmed exposure to asbestos were referred to their CPAM, to apply for the medical follow-up. The whole process was evaluated through a comparison with control CPAMs, and simulations were performed to assess its sensitivity and specificity, as well as the total number of persons in France who could potentially benefit. RESULTS: Among the 737 persons classified as exposed by the matrix who came to the CES, the exposure was confirmed for 53.8%, and 143 benefited from the medical follow-up, 17 times more than in a sample of control CPAMs. Based on an annual number of about 250,000 new retirees, simulations showed that a low detection threshold, taking into account the probability and duration of exposure, would yield approximately 25,000 persons coming to the CES, more 6,000 of them benefiting from the follow-up. CONCLUSION: The proposed detection threshold would allow for a feasible and ethically acceptable generalization, due to the optimization of the false negative and false positive rate.     

Asbestos consumption, asbestos exposure and asbestos-related occupational diseases in Germany

Like in most industrial countries, asbestos is a leading cause of occupational diseases, especially malignant diseases, in Germany. Following the increased consumption of asbestos after World War I, the recognition of asbestos related diseases developed. At the end of the 1930s, Germany was the first country to accept lung cancer in combination with asbestosis as an occupational disease and to initiate the endeavor for reduction of asbestos dust exposure. Nevertheless after World War II the usage of asbestos increased dramatically. The ban of asbestos first came into force in 1993. Until this time several hundreds of thousands of workers had inhaled asbestos and the number of asbestos related diseases increased. In this review the history and current status on asbestos consumption, asbestos exposure and asbestos related occupational diseases in Germany is presented.     

Urinary elimination of acetone in experimental and occupational exposure

Fifteen volunteers were exposed to an acetone vapor concentration of 964-8, 610 mumol/m3 (56-500 mg/m3) for 2-4 h in an exposure chamber. Ten subjects were at rest during the exposure, and five were exposed at alternate rest and light physical exercise. Subsequently 104 workers occupationally exposed to acetone were studied. The relative uptake averaged about 53%, and the ratio of the alveolar concentration to the environmental concentration averaged about 0.28. Both for the experimentally exposed subjects and the occupationally exposed workers the urinary acetone concentration showed a linear relationship to the corresponding environmental time-weighted average concentration. A linear equation also existed between urinary concentrations and the amounts of acetone absorbed. The findings enable a consideration of the urinary concentration of the unaltered acetone as an appropriate exposure indicator and the proposal of a "biological equivalent threshold" to be used in the field of biological monitoring.     

Urinary phenylmercapturic acid as a marker of occupational exposure to benzene

A hand-saving HPLC method to measure urinary phenylmercapturic acid (PMA) was developed which allows about 35 PMA determinations per day. The method involves conversion of pre-PMA to PMA by the addition of sulfuric acid to a urine sample, extraction into an ether-methanol mixture followed by condensation under a nitrogen stream. The condensate was introduced to a ODS-3 column in a HPLC system, and PMA in the column was eluted into a mobile phase of acetonitrile: methanol: perchloric acid: water. The elution of PMA was monitored at 205 nm. One determination will be completed in 40 min. The method was applied to analysis of end-of-shift urine samples from 152 workers exposed up to 210 ppm benzene, 66 workers exposed to a mixture of benzene (up to 116 ppm) and toluene + xylenes (up to 118 ppm), and 131 non-exposed controls of both sexes. A linear regression was established between time-weighted average intensity of exposure to benzene and urinary PMA. From the regression, it was calculated that urinary PMA level will be about 6.4 mg/l after 8-hour exposure to benzene at 100 ppm, and that PMA in urine accounted for about 0.1% of benzene absorbed. No effects of sex, age, and smoking habit of individuals were detected, and the effect of co-exposure to toluene + xylenes at the levels comparable to that of benzene was essentially nil, which indicates an advantage of PMA as a benzene exposure marker over monoto tri-phenolic metabolites or t,t-muconic acid.