Asbestos Exposure Assessment Research Articles

P16 INK4A inactivation mechanisms in non-small-cell lung cancer patients occupationally exposed to asbestos

Epidemiological studies have shown that asbestos fibers constitute the major occupational risk factor and that asbestos acts synergistically with tobacco smoking to induce lung cancer. Although some somatic gene alterations in lung cancer have been linked to tobacco smoke, few data are available on the role of asbestos fibers. P16/ CDKN2A is an important tumor suppressor gene that is frequently altered in lung cancer via promoter 5′-CpG island hypermethylation and homozygous deletion, and rarely via point mutation. Many studies suggest that tobacco smoking produces P16/ CDKN2A promoter hypermethylation in lung cancer, but the status of this gene in relation to asbestos exposure has yet to be determined. The purpose of this study was to investigate the mechanism of P16/ CDKN2A alterations in lung cancer in asbestos-exposed patients. P16/ CDKN2A gene status was studied in 75 human non-small-cell lung cancer (NSCLC) cases with well-defined smoking habits, and detailed assessment of asbestos exposure, based on occupational questionnaire and determination of asbestos bodies in lung tissue. The results of this study confirm published data on the effect of tobacco smoke on P16/ CDKN2A gene alterations, characterized by significantly higher P16/ CDKN2A promoter hypermethylation in heavy smokers (more than 40 pack-years (P-Y)) than in smokers of less than 40 P-Y. These results also demonstrate a higher incidence of loss of heterozygosity and homozygous deletion in asbestos-exposed cases, after adjustment for age and cumulative tobacco consumption, than in unexposed cases ( P = 0.0062). This study suggests that P16/ CDKN2A gene inactivation in asbestos-exposed NSCLC cases mainly occurs via deletion, a feature also found in malignant mesothelioma, a tumor independent of tobacco smoking but associated with asbestos exposure, suggesting a possible relationship with an effect of asbestos fibers.

Factors associated with cancer distress in the Asbestos Post‐Exposure Survey (APEXS)

CT-scan screening programs for lung cancer detection have been proposed in high-risk subjects, and more recently in former asbestos-exposed subjects. However, to date no data are available on psychological impact of such programs. The aim of this study is to examine the risk factors of psychological distress at baseline of a CT-scan screening program among asbestos-exposed subjects. The Asbestos Post-Exposure Survey (APEXS) was carried out in France between October 2003 and December 2005 in order to screen asbestos-related diseases by CT-scan. Volunteers underwent self-administered questionnaires including an asbestos exposure assessment and, for a large sub-sample, a validated psychological distress scale. Non-exposed subjects were used as reference group. At baseline, a significant higher level of distress was observed in exposed subjects (n = 3,122) relative to the reference group (n = 486) after adjustment on age, sex, and tobacco status. This distress is associated independently with the self-perception of (i) intensity of asbestos exposure and (ii) the risk of current or future disease related to the asbestos exposure. The perception of the cancer risk related to asbestos seems to play a fundamental role in this psychological distress. In this study, asbestos-exposed subjects experienced a higher significant cancer distress than previously described in literature. These findings may be of potential public health importance. First, the impact of such occupational exposures on quality of life of patients who suffer from cancer related to these exposures has to be appraised. Secondly, the assessment of psychological impact of CT-scan screening programs among asbestos-exposed subjects is also required.

Linking Expert Judgement and Trends in Occupational Exposure into a Job-Exposure Matrix for Historical Exposure to Asbestos in The Netherlands

The aim of this article was to describe the structure and content of a job-exposure matrix (JEM) for historical asbestos exposure in The Netherlands. The JEM contained 309 occupational job title groups in 70 branches of industry during 10 periods of 5 years during 1945-1994, resulting in 3090 evaluations. Dutch sources on asbestos exposure measurements provided quantitative guidance for 69 evaluations (2.2%) in 25 occupational title groups. In addition, three databases from the UK Health and Safety Executive contributed to 222 evaluations (7.2%) and several other sources aided in another 133 evaluations (4.3%). These evaluations resulted in seven categories of exposure levels for all 3090 combinations of occupational title groups and periods. A verification process with five experts was used to adjust the assignments of exposure categories. The trends in exposure patterns over time were described in relation to production activities, operational control measures and the presence of dust control measures. For the majority of asbestos-related diseases in the past decades, reliable information on their historical exposure patterns was lacking. The limited availability of exposure measurements in the past illustrates the need for a structured assessment of historical asbestos exposure through a JEM.

Asbestos Exposures of Mechanics Performing Clutch Service on Motor Vehicles

A study was conducted to assess historical asbestos exposures of mechanics performing clutch service on motor vehicles. For most of the 20th century, friction components used in brakes and manual transmission clutches contained approximately 25–60% chrysotile asbestos. Since the late 1960s, asbestos exposure assessment studies conducted on mechanics performing brake service have frequently reported levels below the current OSHA permissible exposure limit (PEL) of 0.1 fiber/cc (flcc). Although there is a robust asbestos exposure data set for mechanics performing brake service, there are almost no data for mechanics removing and replacing clutches in manual transmission vehicles. Personal and area airborne asbestos samples were collected during the removal of asbestos-containing clutches from 15 manual transmissions obtained from salvage facilities by an experienced mechanic. Clutch plates and debris were analyzed for asbestos using EPA and ISO published analytical methods. More than 100 personal and area air samples were collected and analyzed for asbestos fibers using NIOSH methods 7400 and 7402. A separate study involved a telephone survey of 16 automotive mechanics who began work prior to 1975. The mechanics were asked about the duration, frequency, and methods used to perform clutch service. Wear debris in the bell housing surrounding clutches had an average of 0.1% chrysotile asbestos by weight, a value consistent with similar reports of brake debris. Asbestos air sampling data collected averaged 0.047 flcc. Mechanics participating in the telephone survey indicated that clutch service was performed infrequently, the entire clutch assembly was normally replaced, and there was no need to otherwise handle the asbestos-containing clutch plates. These mechanics also confirmed that wet methods were most frequently used to clean debris from the bell housing. Combining the asbestos exposure that occurred when mechanics performed clutch service, along with the duration and frequency of this task, the incremental contribution of this task to mechanics' 8-hr time-weighted average (TWA) asbestos exposures was 0.0016 flcc. Using the range of data inputs that were obtained, the authors calculated a range of TWA exposures of 3.75 × 10−5 flcc to 0.03 flcc. The mean value of 0.0016 flcc is below background levels of asbestos that have been reported in garages during this time and below the current OSHA PEL of 0.1 flcc.

Directions and Needs in Asbestos Research: New Insights: Conference Summary

The Center for Environmental Health Sciences (CEHS) Conference, entitled “Directions and Needs in Asbestos Research: New Insights,” was held at the University of Montana in Missoula. Researchers, physicians, health care workers, and federal agency representatives from around the country met for a cross-disciplinary exploration of many issues related to asbestos research. Topics included community and psychosocial issues in biomedical research, asbestos exposure assessment, assessment and mechanisms of asbestos related diseases, and new research directions. This meeting report is a summary of the conference presentations, and of the topics identified for future research directions. This conference was a follow-up to one hosted by the CEHS in June 2002, and continued to take advantage of opportunities to work with a unique population in Libby MT, where significant asbestos exposures have occurred due to the mining of asbestos-contaminated vermiculite. The goals of this conference were to bring together experts from diverse fields to identify progress made since the last conference and to develop new research avenues that would allow us to address the research needs in emerging asbestos-exposed populations. Participants indicated that these objectives were met, and expressed enthusiasm for follow-up conferences to maintain the dialog that has been established regarding directions and needs in asbestos research. Selected papers from the conference are presented here.

Assessment of airborne asbestos exposure during the servicing and handling of automobile asbestos-containing gaskets

Five test sessions were conducted to assess asbestos exposure during the removal or installation of asbestos-containing gaskets on vehicles. All testing took place within an operative automotive repair facility involving passenger cars and a pickup truck ranging in vintage from late 1960s through 1970s. A professional mechanic performed all shop work including engine disassembly and reassembly, gasket manipulation and parts cleaning. Bulk sample analysis of removed gaskets through polarized light microscopy (PLM) revealed asbestos fiber concentrations ranging between 0 and 75%. Personal and area air samples were collected and analyzed using National Institute of Occupational Safety Health (NIOSH) methods 7400 [phase contrast microscopy (PCM)] and 7402 [transmission electron microscopy (TEM)]. Among all air samples collected, approximately 21% ( n = 11) contained chrysotile fibers. The mean PCM and phase contrast microscopy equivalent (PCME) 8-h time weighted average (TWA) concentrations for these samples were 0.0031 fibers/cubic centimeters (f/cc) and 0.0017 f/cc, respectively. Based on these findings, automobile mechanics who worked with asbestos-containing gaskets may have been exposed to concentrations of airborne asbestos concentrations approximately 100 times lower than the current Occupational Safety and Health Administration (OSHA) Permissible Exposure Limit (PEL) of 0.1 f/cc.

Conference Summary. Directions and Needs in Asbestos Research: New Insights

The Center for Environmental Health Sciences (CEHS) Conference entitled “Directions and Needs in Asbestos Research: New Insights” was held at the University of Montana in Missoula on July 28 and 29, 2005. Researchers, physicians, health care workers, and federal agency representatives from around the country met for a cross-disciplinary exploration of many issues related to asbestos research. Topics included community and psychosocial issues in biomedical research, asbestos exposure assessment, assessment and mechanisms of asbestos-related diseases, and new research directions. This meeting report is a summary of the conference presentations, and of the topics identified for future research directions. This conference was a follow-up to one hosted by the CEHS in June 2002, and continued to take advantage of opportunities to work with a unique population in Libby, MT, where significant asbestos exposures have occurred due to the mining of asbestos-contaminated vermiculite. The goals of this conference were to bring together experts from diverse fields to identify progress made since the last conference and to develop new research avenues that would allow us to address the research needs in emerging asbestos-exposed populations. Participants indicated that these objectives were met, and expressed enthusiasm for follow-up conferences, tentatively planned for the summer of 2007, to maintain the dialog that has been established regarding directions and needs in asbestos research. Selected papers from the conference are presented in this issue of Inhalation Toxicology.

Asbestos exposure assessment by mineralogical analysis of bronchoalveolar lavage fluid.

Mineralogical analysis of bronchoalveolar lavage fluid (BALF) by electron microscopy can represent the most suitable method for assessing asbestos exposure. However, it has been claimed that no standardized or systematic approach to the subject of mineralogical analysis exists. This study aimed to evaluate BALF mineralogical analysis by transmission electron microscopy as biomarker of asbestos fiber load. BALF was examined in 108 exposed workers and 57 patients who underwent diagnostic fiberoptic bronchoscopy for various clinical purposes. Asbestos bodies in BALF were counted with a phase-contrast microscope. Fibers were counted and analyzed by transmission electron microscopy, which showed a significant difference between the two populations and positive results for all exposed subjects. Only 82.2% of the exposed population tested positive for asbestos bodies. Subjects with long-term exposure had higher concentrations of fibers than did those with more recent exposure, probably because of the higher workplace exposure levels in the past. The results of the study confirm that fiber concentration in BALF can be considered as a reliable biomarker of past asbestos exposure, even many years after the end of exposure.

Information about occupational exposure to asbestos given to cases in an etiological study: ethical aspects.

The aim of the study is to consider some ethical aspects of the provision of information, to the cases or their families, about the assessment of occupational asbestos exposure obtained in a case-control study of malignant mesothelioma of the pleura. An informative letter with the result of the evaluation of their occupational exposure to asbestos was sent to the participating cases (and/or their family). Those whose exposure was classified as certain/probable were also informed of the legislation regarding occupational diseases. Of the 132 cases, 32.6% of subjects and/or their families made telephone calls expressing interest in the content of the informative letter. Among the 63 cases classified as certain/probable exposure, this proportion was 47.6%. Out of 43 cases in which the age at diagnosis was < or = 65 years and the exposure to asbestos was certain/probable, only two (4.6%) were signed off work owing to occupational disease. Only one of the mesothelioma cases was recognized by the Spanish National Institute for Social Security (INSS) as having an occupational disease. The process of communication of the results of an epidemiological research should include the provision of information on the exposure data to each one of the subjects, and/or their families. There is a great disparity between the number of cases of certain/probable exposure to asbestos identified in our study, and the number registered as an occupational disease by the INSS.

Assessment of environmental asbestos exposure in Turkey by bronchoalveolar lavage.

Environmental or domestic exposure to asbestos fibers originating from local soil is responsible for a high incidence of diseases in large rural areas of Turkey. Bronchoalveolar lavage fluids (BALF) were obtained for 65 Turkish subjects originating from these areas and for 42 Turkish controls. Asbestos bodies (ABs) and uncovered fibers (UFs) were quantified by phase contrast light microscopy. Total fiber burden was determined by transmission electron microscopy. The main asbestos types disclosed were tremolite and to a lesser extent chrysotile. AB and fiber concentrations were higher in environmentally exposed subjects (geometric mean [geometric standard deviation]: 5.20 [6.22] AB/ml, 444 [11.6] tremolite fibers/ml) than in control subjects (0.22 [1.45] AB/ml, 12.0 [15.4] tremolite fibers/ml) (p < 0.001). In subjects environmentally exposed in Turkey, AB burdens on tremolite were in the same range as those on commercial amphiboles in subjects occupationally exposed in Belgium. In Turkish subjects, values above either 1 AB/ml, 3 uncovered fiber/ml in light microscopy, or 300 fibers/ml in electron microscopy indicated usually an abnormal alveolar retention reflecting a significant cumulative exposure from environmental or domestic origin. These observations are probably valid for other areas in the world where diseases associated with environmental exposure to soil- derived asbestos fibers occur and for immigrants originating from these areas.

Retrospective assessment of asbestos exposure--I. Case-control analysis in a study of lung cancer: efficiency of job-specific questionnaires and job exposure matrices.

Retrospective assessment of asbestos exposure--I. Case-control analysis in a study of lung cancer: efficiency of job-specific questionnaires and job exposure matrices. International Journal of Epidemiology 1993; 22 (Suppl. 2): S83-S95. In a lung cancer study in Northern Germany the asbestos exposure assessment obtained from detailed supplementary questionnaires (SQ) was compared to the assessment obtained by the application of two job exposure matrices (JEM) to the job history. The study includes 391 incident male cases and the same number of controls from the general population, matched by sex, age, and region. Almost 16% of the subjects are considered as never having been exposed to asbestos and 24% are classified as certainly exposed according to both of the JEM, the corresponding percentages of the SQ-method being 68% and 32%. Sixty percent are considered by the JEM as having an intermediate probability of exposure. In general, the agreement between the different methods is better when the exposure definition is restricted to definite exposures, the corresponding Kappa statistic being 0.67 for the comparison between both JEM and 0.44/0.39 between the JEM and the SQ. The positive agreement between SQ and JEM (reference) increases from 12% and 17% for subjects with low probability of exposure to 61% and 69% for those with definite exposures. A ranking according to cumulative exposure shows some dose-response relationship for each of the three methods with a smoking-adjusted OR in the highest category of 1.85 (95% CI: 1.01-3.38) for the SQ method and 2.47 (95% CI: 1.40-4.37) and 2.94 (95% CI: 1.73-4.99) for the two JEM. The results are discussed with reference to the conceptual differences between the methods and their potential scope in future studies.

Chronological Assessment of Asbestos Exposure on Cell Composition in Murine Lung

To elucidate immune pathogenic mechanisms in asbestosis, lung and spleen lymphoid cell populations were analyzed at defined time intervals (1, 2, 3, 6, and 12 weeks during exposure and 4, 24, and 48 weeks post-exposure) in asbestos-exposed and unexposed (control) mice. Polymorphonuclear leukocytes and macrophages were increased in the lung tissue histologic sections of asbestos-exposed mice compared to controls. No consistent changes were observed in percentages of lung or spleen helper, suppressor, or total lymphocyte populations after asbestos exposure. The numbers of B cells (identified by anti-IgG) in minced lung preparations of asbestos-exposed animals were increased after 12 weeks of exposure. There also was an increase in IgG production in asbestos-exposed mice after 12 weeks exposure and at 4 weeks post-exposure with a return to near baseline levels 24 and 48 weeks after initial exposure. Collectively, these studies demonstrate stimulatory effects of inhaled asbestos fibers on B cells and IgG production after 12 weeks of continuous inhalation of asbestos fibers in a dust generation chamber.

Assessment of Low Level Asbestos Exposure in the Urban Environment

Assessment of Low Level Asbestos Exposure in the Urban Environment

Assessing asbestos exposure potential in nonindustrial settings.

The presence of asbestos containing materials (ACM) in office and commercial buildings is a significant environmental problem. Asbestosis, mesothelioma and lung cancer have been linked with industrial exposure to airborne asbestos. The extensive use of asbestos products in buildings has raised concerns about the widespread exposure of the general public to asbestos in nonoccupational settings. The presence of asbestos in a building does not necessarily mean that significant exposure of the occupants of the building has occurred, but it is important that the asbestos be monitored regularly to ensure that fibers do not become airborne. If ACM are contained within a matrix and not disturbed, exposure is unlikely. However, if the asbestos becomes friable (crumbling) or if building maintenance, repair, renovation or other activities disturb ACM, airborne asbestos fibers may be a source of exposure to the occupants of the building. Currently, asbestos exposure assessment is conducted by a phase contrast light microscope (PCM) technique. Due to its inherent limitation in resolution and the generic counting rules used, analysis by the PCM method underestimates the airborne asbestos fiber concentration as compared to analysis by transmission electron microscopy (TEM). It is important that the air monitoring results analyzed by PCM be interpreted carefully in conjunction with a survey by a professional to judge the physical condition of the ACM in buildings. Exposure levels to airborne asbestos fibers vary from day to day and depend on the physical condition of the material involved and the type of operating and maintenance program in place.(ABSTRACT TRUNCATED AT 250 WORDS)