Sarić M, Curin K, Varnai VM.

Institute for Medical Research and Occupational Health, Zagreb, Croatia. marko@imi.hr

Abstract

From the Croatian Cancer Registry (period 1991-1997) 194 malignant pleural mesothelioma patients were collected. According to participation in polio vaccination mass campaign in 1961 that covered the entire Croatian population aged 3 months to 20 years, mesothelioma patients were divided in vaccinated (N=58), and non-vaccinated (N=136) subjects. Significantly higher percentage of those with a history of occupational exposure to asbestos was found in vaccinated (79%) compared to non-vaccinated group (63%). This is the opposite to what would be expected if potential SV40 contamination of polio vaccine used had a causative role in the development of the tumour. On the other hand, shorter latency period reflected by very high percentage of 45-year-old or younger mesothelioma patients in vaccinated group (15 out of 58), with all of them having a history of occupational asbestos exposure, raises a question for a possible enhancing effect of the vaccine used to asbestos exposure, if it was contaminated with SV40.

Glossary

cancer

malignancy; a group of diseases typified by abnormal, generally out-of-control, cell growth.

vaccine

the modified virus of a disease used to bring about resistance to that disease for a period of time, or even permanently. Development of a cancer vaccine is a subject of intense research.

mesothelioma

a tumor derived from mesothelial tissue, such as the peritoneum (lining the abdomen) or pleura (lining the lungs). More on mesothelioma.

Frost G, Harding AH, Darnton A, McElvenny D, Morgan D.

Health & Safety Laboratory, Harpur Hill, Buxton, Derbyshire SK17 9JN, UK. Gillian.Frost@hsl.gov.uk

Abstract

The asbestos industry has shifted from manufacture to stripping/removal work. The aim of this study was to investigate early indications of mortality among removal workers. The study population consisted of 31 302 stripping/removal workers in the Great Britain Asbestos Survey, followed up to December 2005. Relative risks (RR) for causes of death with elevated standardised mortality ratios (SMR) and sufficient deaths were obtained from Poisson regression. Risk factors considered included dust suppression technique, type of respirator used, hours spent stripping, smoking status and exposure length. Deaths were elevated for all causes (SMR 123, 95% CI 119-127, n=985), all cancers including lung cancer, mesothelioma, and circulatory disease. There were no significant differences between suppression techniques and respirator types. Spending more than 40 h per week stripping rather than less than 10, increased mortality risk from all causes (RR 1.4, 95% CI 1.2-1.7), circulatory disease and ischaemic heart disease. Elevated mesothelioma risks were observed for those first exposed at young ages or exposed for more than 30 years. This study is a first step in assessing long-term mortality of asbestos removal workers in relation to working practices and asbestos exposure. Further follow-up will allow the impact of recent regulations to be assessed.

Keywords: asbestos, mortality, Great Britain, occupational exposure, asbestos removal

Glossary

mortality

a measure of the rate of death from a disease within a given population.

cancer

malignancy; a group of diseases typified by abnormal, generally out-of-control, cell growth.

mesothelioma

a tumor derived from mesothelial tissue, such as the peritoneum (lining the abdomen) or pleura (lining the lungs). More on mesothelioma.

Nagao N, Nishikawa K, Kiyomoto Y, Todoroki M, Hoshuyama T, Takahashi K.

Department of Emergency, Kansai Rosai Hospital, Japan.

Abstract

In June 2005 the press reported that many former employees of a company which used asbestos, and individuals who lived near the company’s factory, had been diagnosed with mesothelioma. This finding triggered concern and alarm in Japan. In response, many "asbestos clinics" were formed, and recognized medical institutions began to implement asbestos-related health examinations. We conducted a nationwide questionnaire survey to evaluate the activities in, and the challenges for, these medical institutions. We received 137 valid responses, more than half of which were from clinics and hospital-based "asbestos clinics" instigated after the "Kubota shock." Among the asbestos exposure history interviewing practices, job histories of the interviewee were prioritized, over place of residence, and possible exposure of family members. Standard questionnaires were utilized by over 70% of respondents. The practitioners reported problems with lack of manpower and evaluation of asbestos exposure. Examinees consulted attending physicians on a wide range of matters including asbestos-related diseases, asbestos exposure, and financial compensation. It is predicted that asbestos-related diseases in general, and mesothelioma in particular, will increase in the future. Accordingly, early detection and treatment should be accorded high priority. The organizations we surveyed have important roles to play. Although resources are limited, effective diagnosis and treatment are essential, and a system assisting organizations to make accurate and efficient identification of asbestos exposure hazards is imperative.

Glossary

diagnosis

identifying a disease by its signs or symptoms, and by using imaging procedures and laboratory findings. The earlier a diagnosis of cancer is made, the better the chance for long-term survival.

detection

finding disease. Early detection means that the disease is found at an early stage, before it has grown large or spread to other sites. Note many forms of cancer can reach an advanced stage without causing symptoms. Mammography can help to find breast cancer early, and the PSA blood test is useful in finding prostate cancer.

mesothelioma

a tumor derived from mesothelial tissue, such as the peritoneum (lining the abdomen) or pleura (lining the lungs). More on mesothelioma.

Yang H, Testa JR, Carbone M.

Cancer Research Center of Hawaii, University of Hawaii, Honolulu, HI, 96813, USA.

Abstract

Opinion Statement: The incidence of mesothelioma has gone from almost none to the current 2500-3000 cases per year in the USA. This estimate is an extrapolation based on information available from the Surveillance, Epidemiology and End Results (SEER) Program that collects information on approximately 12% of the US population. Mesothelioma is a cancer that is linked to exposure to carcinogenic mineral fibers. Asbestos and erionite have a proven causative role; the possible role of other mineral fibers in causing mesothelioma is being investigated. Asbestos is considered the main cause of mesothelioma in the US and in the Western world. The capacity of asbestos to induce mesothelioma has been linked to its ability to cause the release of TNF-alpha (that promotes mesothelial cells survival), other cytokines and growth factors, and of mutagenic oxygen radicals from exposed mesothelial cells and nearby macrophages. Some investigators proposed that as a consequence of the regulations to prevent exposure and to forbid and/or limit the use of asbestos, the incidence of mesothelioma in the US (and in some European countries) should have started to decline before or around the year 2000, and sharply decline thereafter. Unfortunately, there are no data available yet to support this optimistic hypothesis. Simian virus 40 (SV40) infection and radiation exposure are additional causes, although their contribution to the overall incidence of mesothelioma is unknown. Recent data from several laboratories indicate that asbestos exposure and SV40 infection are co-carcinogens in causing mesothelioma in rodents and in causing malignant transformation of human mesothelial cells in tissue culture. An exciting new development comes from the discovery that genetic susceptibility to mineral fiber carcinogenesis plays a critical role in the incidence of this cancer in certain families. It is hoped that the identification of this putative mesothelioma gene will lead to novel mechanistically driven preventive and therapeutic approaches.

Glossary

oncology

(on-call-o-jee) the branch of medicine concerned with the diagnosis and treatment of cancer.

growth factors

a naturally occurring protein that causes cells to grow and divide. Too much growth factor production by some cancer cells helps them grow quickly, and new treatments to block these growth factors are being tested in clinical trials. Other growth factors help normal cells recover from side effects of chemotherapy.

gene

a segment of DNA that contains information on hereditary characteristics such as hair color, eye color, and height, as well as susceptibility to certain diseases. Women who have BRCA1 or BRCA2 gene mutations (defects) have an inherited tendency to develop breast cancer.

epidemiology

(ep-uh-deem-ee-AHL-uh-gee) the study of diseases in populations by collecting and analyzing statistical data. In the field of cancer, epidemiologists look at how many people have cancer; who gets specific types of cancer; and what factors (such as environment, job hazards, family patterns, and personal habits, such as smoking and diet) play a part in the development of cancer.

cancer

malignancy; a group of diseases typified by abnormal, generally out-of-control, cell growth.

tissue

a collection of cells, united to perform a particular function.

virus

very small organisms that cause infections. Viruses are too small to be seen with a regular microscope. They reproduce only in living cells.

mesothelioma

a tumor derived from mesothelial tissue, such as the peritoneum (lining the abdomen) or pleura (lining the lungs). More on mesothelioma.

Amin W, Parwani AV, Schmandt L, Mohanty SK, Farhat G, Pople AK, Winters SB, Whelan NB, Schneider AM, Milnes JT, Valdivieso FA, Feldman M, Pass HI, Dhir R, Melamed J, Becich MJ.

Abstract

Background: Advances in translational research have led to the need for well characterized biospecimens for research. The National Mesothelioma Virtual Bank (NMVB) is an initiative which collects annotated datasets relevant to human mesothelioma to develop an enterprise biospecimen resource to fulfill researchers’ need.

Methods: The NMVB architecture is based on three major components: (a) common data elements (based on CAP protocol and NAACCR standards), (b) clinical and epidemiologic data annotation, and (c) data query tools. These tools work interoperably to standardize the entire process of annotation. The NMVB tool is based upon the caTISSUE Clinical Annotation Engine (CAE), developed by the University of Pittsburgh in cooperation with the Cancer Biomedical Informatics GridTM (caBIGTM, see http://cabig.nci.nih.gov). This application provides a web-based system for annotating, importing and searching mesothelioma cases. The underlying information model is constructed utilizing Unified Modeling Language (UML) class diagrams, hierarchical relationships and Enterprise Architect (EA) software. Result: The database provides researchers real-time access to richly annotated specimens and integral information related to mesothelioma. The data disclosed are tightly regulated depending upon users’ authorization and depending on the participating institute that is amenable to the local IRB and regulation committee reviews.

Conclusion: The NMVB currently has over 600 annotated cases available for researchers that include paraffin embedded tissues, tissue microarrays, serum and genomic DNA. The NMVB is a virtual biospecimen registry with robust translational biomedical informatics support to facilitate basic science, clinical, and translational research. Furthermore, it protects patient privacy by disclosing only de-identified datasets to assure that biospecimens can be made accessible to researchers.

Glossary

protocol

(pro-teh-call) a formal outline or plan, such as a description of what treatments a patient will receive and exactly when each should be given.

DNA

(dee-ok-see-ri-bo-new-CLAY-ic) abbreviation for deoxyribonucleic acid. DNA holds genetic information on cell growth, division, and function.

cancer

malignancy; a group of diseases typified by abnormal, generally out-of-control, cell growth.

tissue

a collection of cells, united to perform a particular function.

mesothelioma

a tumor derived from mesothelial tissue, such as the peritoneum (lining the abdomen) or pleura (lining the lungs). More on mesothelioma.

Barbieri PG, Somigliana A, Girelli R, Lombardi S, Festa R, Silvestri S.

Servizio Prevenzione e Sicurezza Ambienti di Lavoro, ASL Brescia. pietro.barbieri@aslbrescia.it

Abstract

Background: Due to poor information collected through patient interviews, a considerable number of malignant mesothelioma (MM) cases still remain classified as "unknown" asbestos exposure in the Italian Mesotelioma Registry (Re.Na.M). At the same time, some occupational asbestos exposures, which were previously unknown, have been demonstrated in certain types of work, i.e., in agriculture and in the textile industry.

Objectives: The aim of this research was to investigate the possible past occupational exposure to asbestos in clothing workers using sewing-machines.

Methods: The MM cases were collected from the Mesothelioma Registry of Brescia. Work histories were obtained via a standardized questionnaire. Investigations were conducted in sewing-machine maintenance workshop in order to collect information regarding the possible use of asbestos parts. In addition, the use of asbestos friction materials and the use of insulated asbestos materials was checked in the clothing divisions by interviewing the management and maintenance workers of two companies where cases of MM were observed.

Results: The Mesothelioma Registry of Brescia identified and collected 10 MM cases with past work in the clothing industry: 6 used sewing-machines and 4 were self-employed tailors. The search for asbestos materials gave positive results as the use of friction materials had been widespread since the 1950’s in all types of sewing-machines; in addition, asbestos materials were used to insulate some parts of the ironing equipment and the steam pipelines.

Conclusion: The results of this investigation suggest assigning at least "possible occupational asbestos exposure" to those cases employed in clothing manufacture since the 1950’s, who used sewing-machines or pressing machines, according to the Re.Na.M guidelines. Other possible occupational exposures to asbestos in this working sector cannot be excluded; when the simple interview of patients does not reveal such exposures further investigations are needed in order to demonstrate all the possible circumstances of exposure.

Glossary

mesothelioma

a tumor derived from mesothelial tissue, such as the peritoneum (lining the abdomen) or pleura (lining the lungs). More on mesothelioma.

Pedra F, Tambellini AT, Pereira Bde B, da Costa AC, de Castro HA.

Center for the Study of Worker Health and Human Ecology, National School of Public Health, Fiocruz, Rio de Janeiro, Brazil. fpedra@ensp.fiocruz.br

Abstract

Although asbestos causes asbestosis, lung cancer, and mesothelioma, it remains widely used in Brazil, mostly in cement-fiber products. We report the Brazilian mesothelioma mortality trend 1980-2003, using records of the national System of Mortality Information of DATASUS, including all deaths with IX International Disease Classification (ICD9) codes 163.n–pleura cancer during the period 1980-1995; and ICD10 codes c45.n–mesotheliomas and c38.4–pleura cancer for the years 1996-2003. Mesothelioma mortality rates increased over the period studied, from 0.56 to 1.10 deaths per 100,000 habitants. The total number of mesothelioma deaths nationwide in the period studied was 2,414; the majority (1,415) were in the Southeast region. Mortality was highest among males and people over age 65. Given the history of asbestos exposure in Brazil, our findings support the need for policies that limit or ban the use of this product.

Glossary

pleura

(pler-uh) the membrane around the lungs and lining of the chest cavity. (Pleural mesothelioma.)

mortality

a measure of the rate of death from a disease within a given population.

cancer

malignancy; a group of diseases typified by abnormal, generally out-of-control, cell growth.

mesothelioma

a tumor derived from mesothelial tissue, such as the peritoneum (lining the abdomen) or pleura (lining the lungs). More on mesothelioma.

Berman DW, Crump KS.

Aeolus, Inc., Albany, California, USA.

Abstract

Quantitative estimates of the risk of lung cancer or mesothelioma in humans from asbestos exposure made by the U.S. Environmental Protection Agency (EPA) make use of estimates of potency factors based on phase-contrast microscopy (PCM) and obtained from cohorts exposed to asbestos in different occupational environments. These potency factors exhibit substantial variability. The most likely reasons for this variability appear to be differences among environments in fiber size and mineralogy not accounted for by PCM.

In this article, the U.S. Environmental Protection Agency (EPA) models for asbestos-related lung cancer and mesothelioma are expanded to allow the potency of fibers to depend upon their mineralogical types and sizes. This is accomplished by positing exposure metrics composed of nonoverlapping fiber categories and assigning each category its own unique potency. These category-specific potencies are estimated in a meta-analysis that fits the expanded models to potencies for lung cancer (K_L’s) or mesothelioma (K_M’s) based on PCM that were calculated for multiple epidemiological studies in our previous paper (Berman and Crump, 2008). Epidemiological study-specific estimates of exposures to fibers in the different fiber size categories of an exposure metric are estimated using distributions for fiber size based on transmission electron microscopy (TEM) obtained from the literature and matched to the individual epidemiological studies. The
fraction of total asbestos exposure in a given environment respectively represented by chrysotile and amphibole asbestos is also estimated from information in the literature for that environment. Adequate information was found to allow K_L’s from 15 epidemiological studies and K_M’s from 11 studies to be included in the meta-analysis.

Since the range of exposure metrics that could be considered was severely restricted by limitations in the published TEM fiber size distributions, it was decided to focus attention on four exposure metrics distinguished by fiber width: “all widths,” widths > 0.2 μ m, widths < 0.4 μ m, and widths < 0.2 μ m, each of which has historical relevance. Each such metric defined by width was composed of four categories of fibers: chrysotile or amphibole asbestos with lengths between 5 μ m and 10 μ m or longer than 10 μ m. Using these metrics three parameters were estimated for lung cancer and, separately, for mesothelioma: K_LA, the potency of longer (length > 10 μ m) amphibole fibers; rpc, the potency of pure chrysotile (uncontaminated by amphibole) relative to amphibole asbestos; and rps, the potency of shorter fibers (5 μ m < length < 10 μ m) relative to longer fibers.

For mesothelioma, the hypothesis that chrysotile and amphibole asbestos are equally potent (rpc = 1) was strongly rejected by every metric and the hypothesis that (pure) chrysotile is nonpotent for mesothelioma was not rejected by any metric. Best estimates for the relative potency of chrysotile ranged from zero to about 1/200th that of amphibole asbestos (depending on metric). For lung cancer, the hypothesis that chrysotile and amphibole asbestos are equally potent (rpc = 1) was rejected (p ≤ .05) by the two metrics based on thin fibers (length < 0.4 μ m and < 0.2 μ m) but not by the metrics based on thicker fibers.

The “all widths” and widths < 0.4 μ m metrics provide the best fits to both the lung cancer and mesothelioma data over the other metrics evaluated, although the improvements are only marginal for lung cancer. That these two metrics provide equivalent (for mesothelioma) and nearly equivalent (for lung cancer) fits to the data suggests that the available data sets may not be sufficiently rich (in variation of exposure characteristics) to fully evaluate the effects of fiber width on potency. Compared to the metric with widths > 0.2 μ m with both rps and rpc fixed at 1 (which is nominally equivalent to the traditional PCM metric), the “all widths” and widths < 0.4 μ m metrics provide substantially better fits for both lung cancer and, especially, mesothelioma.

Although the best estimates of the potency of shorter fibers (5 < length < 10 μ m) is zero for the “all widths” and widths < 0.4 μ m metrics (or a small fraction of that of longer fibers for the widths > 0.2 μ m metric for mesothelioma), the hypothesis that these shorter fibers were nonpotent could not be rejected for any of these metrics. Expansion of these metrics to include a category for fibers with lengths < 5 μ m did not find any consistent evidence for any potency of these shortest fibers for either lung cancer or mesothelioma.

Despite the substantial improvements in fit over that provided by the traditional use of PCM, neither the “all widths” nor the widths < 0.4 μ m metrics (or any of the other metrics evaluated) completely resolve the differences in potency factors estimated in different occupational studies. Unresolved in particular is the discrepancy in potency factors for lung cancer from Quebec chrysotile miners and workers at the Charleston, SC, textile mill, which mainly processed chrysotile from Quebec. A leading hypothesis for this discrepancy is limitations in the fiber size distributions available for this analysis. Dement et al. (2007) recently analyzed by TEM archived air samples from the South Carolina plant to determine a detailed distribution of fiber lengths up to lengths of 40 μ m and greater. If similar data become available for Quebec, perhaps these two size distributions can be used to eliminate the discrepancy between these two studies.

Keywords: Amphibole; asbestos; chrysotile; fiber size; lung cancer; mesothelioma; mineralogy; risk assessment.

Glossary

cancer

malignancy; a group of diseases typified by abnormal, generally out-of-control, cell growth.

mesothelioma

a tumor derived from mesothelial tissue, such as the peritoneum (lining the abdomen) or pleura (lining the lungs). More on mesothelioma.

Dreassi E, Lagazio C, Maule MM, Magnani C, Biggeri A.

Dipartimento di Statistica G. Parenti, Università di Firenze, Firenze, Italy.

Abstract

The relation between disease risk and a point source of pollution is usually investigated using distance from the source as a proxy of exposure. The analysis may be based on case-control data or on aggregated data. The definition of the function relating risk of disease and distance is critical, both in a classical and in a Bayesian framework, because the likelihood is usually very flat, even with large amounts of data. In this paper we investigate how the specification of the function relating risk of disease with distance from the source and of the prior distributions on the parameters of the function affects the results when case-control data and Bayesian methods are used. We consider different popular parametric models for the risk distance function in a Bayesian approach, comparing estimates with those derived by maximum likelihood. As an example we have analyzed the relationship between a putative source of environmental pollution (an asbestos cement plant) and the occurrence of pleural malignant mesothelioma in the area of Casale Monferrato (Italy) in 1987-1993. Risk of pleural malignant mesothelioma turns out to be strongly related to distance from the asbestos cement plant. However, as the models appeared to be sensitive to modeling choices, we suggest that any analysis of disease risk around a putative source should be integrated with a careful sensitivity analysis and possibly with prior knowledge. The choice of prior distribution is extremely important and should be based on epidemiological considerations.

Glossary

mesothelioma

a tumor derived from mesothelial tissue, such as the peritoneum (lining the abdomen) or pleura (lining the lungs). More on mesothelioma.

Berman DW, Crump KS.

Aeolus, Inc., Albany, California, USA.

Abstract

Quantitative estimates of the risk of lung cancer or mesothelioma in humans from asbestos exposure made by the U.S. Environmental Protection Agency (EPA) make use of estimates of potency factors based on phase-contrast microscopy (PCM) and obtained from cohorts exposed to asbestos in different occupational environments. These potency factors exhibit substantial variability. The most likely reasons for this variability appear to be differences among environments in fiber size and mineralogy not accounted for by PCM.

In this article, the U.S. Environmental Protection Agency (EPA) models for asbestos-related lung cancer and mesothelioma are expanded to allow the potency of fibers to depend upon their mineralogical types and sizes. This is accomplished by positing exposure metrics composed of nonoverlapping fiber categories and assigning each category its own unique potency. These category-specific potencies are estimated in a meta-analysis that fits the expanded models to potencies for lung cancer (K_L’s) or mesothelioma (K_M’s) based on PCM that were calculated for multiple epidemiological studies in our previous paper (Berman and Crump, 2008). Epidemiological study-specific estimates of exposures to fibers in the different fiber size categories of an exposure metric are estimated using distributions for fiber size based on transmission electron microscopy (TEM) obtained from the literature and matched to the individual epidemiological studies. The fraction of total asbestos exposure in a given environment respectively represented by chrysotile and amphibole asbestos is also estimated from information in the literature for that environment. Adequate information was found to allow K_L’s from 15 epidemiological studies and K_M’s from 11 studies to be included in the meta-analysis.

Since the range of exposure metrics that could be considered was severely restricted by limitations in the published TEM fiber size distributions, it was decided to focus attention on four exposure metrics distinguished by fiber width: “all widths,” widths > 0.2 μ m, widths < 0.4 μ m, and widths < 0.2 μ m, each of which has historical relevance. Each such metric defined by width was composed of four categories of fibers: chrysotile or amphibole asbestos with lengths between 5 μ m and 10 μ m or longer than 10 μ m. Using these metrics three parameters were estimated for lung cancer and, separately, for mesothelioma: K_LA, the potency of longer (length > 10 μ m) amphibole fibers; rpc, the potency of pure chrysotile (uncontaminated by amphibole) relative to amphibole asbestos; and rps, the potency of shorter fibers (5 μ m < length < 10 μ m) relative to longer fibers.

For mesothelioma, the hypothesis that chrysotile and amphibole asbestos are equally potent (rpc = 1) was strongly rejected by every metric and the hypothesis that (pure) chrysotile is nonpotent for mesothelioma was not rejected by any metric. Best estimates for the relative potency of chrysotile ranged from zero to about 1/200th that of amphibole asbestos (depending on metric). For lung cancer, the hypothesis that chrysotile and amphibole asbestos are equally potent (rpc = 1) was rejected (p ≤ .05) by the two metrics based on thin fibers (length < 0.4 μ m and < 0.2 μ m) but not by the metrics based on thicker fibers.

The “all widths” and widths < 0.4 μ m metrics provide the best fits to both the lung cancer and mesothelioma data over the other metrics evaluated, although the improvements are only marginal for lung cancer. That these two metrics provide equivalent (for mesothelioma) and nearly equivalent (for lung cancer) fits to the data suggests that the available data sets may not be sufficiently rich (in variation of exposure characteristics) to fully evaluate the effects of fiber width on potency. Compared to the metric with widths > 0.2 μ m with both rps and rpc fixed at 1 (which is nominally equivalent to the traditional PCM metric), the “all widths” and widths < 0.4 μ m metrics provide substantially better fits for both lung cancer and, especially, mesothelioma.

Although the best estimates of the potency of shorter fibers (5 < length < 10 μ m) is zero for the “all widths” and widths < 0.4 μ m metrics (or a small fraction of that of longer fibers for the widths > 0.2 μ m metric for mesothelioma), the hypothesis that these shorter fibers were nonpotent could not be rejected for any of these metrics. Expansion of these metrics to include a category for fibers with lengths < 5 μ m did not find any consistent evidence for any potency of these shortest fibers for either lung cancer or mesothelioma.

Despite the substantial improvements in fit over that provided by the traditional use of PCM, neither the “all widths” nor the widths < 0.4 μ m metrics (or any of the other metrics evaluated) completely resolve the differences in potency factors estimated in different occupational studies. Unresolved in particular is the discrepancy in potency factors for lung cancer from Quebec chrysotile miners and workers at the Charleston, SC, textile mill, which mainly processed chrysotile from Quebec. A leading hypothesis for this discrepancy is limitations in the fiber size distributions available for this analysis. Dement et al. (2007) recently analyzed by TEM archived air samples from the South Carolina plant to determine a detailed distribution of fiber lengths up to lengths of 40 μ m and greater. If similar data become available for Quebec, perhaps these two size distributions can be used to eliminate the discrepancy between these two studies.

Keywords: Amphibole; asbestos; chrysotile; fiber size; lung cancer; mesothelioma; mineralogy; risk assessment.

Glossary

cancer

malignancy; a group of diseases typified by abnormal, generally out-of-control, cell growth.

mesothelioma

a tumor derived from mesothelial tissue, such as the peritoneum (lining the abdomen) or pleura (lining the lungs). More on mesothelioma.