Mesothelioma in Mongolia: case report

Abstract

Background:

More than 80% of cases of mesothelioma worldwide have a history of asbestos exposure. In Mongolia, workers in coal burning thermal power plants (TPP) have widely utilized asbestos as an insulation material.

Methods:

We describe the case of a 47-year-old woman diagnosed with a malignant pleural mesothelioma. She worked in a TPP in Ulaanbaatar, Mongolia for 28 years.

Results:

A computer tomography (CT) scan showed a circumferential ring around her left lung, and tissues’ samples had a biphasic variant of mesothelioma with epithelioid and sarcomatoid components.

Discussion:

This is the first reported case of mesothelioma in Mongolia. We expect additional cases of mesothelioma, as well as other asbestos related diseases, will be identified in the future. In order to properly track asbestos related diseases in the country, we recommend the creation of an asbestos related disease registry.     

Compensation of malignant mesothelioma as an occupational disease in Lower Normandy, from 1995 to 2002

BackgroundDespite the close relation between occupational exposure to asbestos and malignant mesothelioma, the compensation of this disease is still far from being the rule. The objective of this study is to assess the compensation process of all the cases of occupational mesothelioma recorded by the regional mesothelioma registry between September 1995 and August 2002, and to make suggestions for improvement of the compensation of future cases.MethodsLifetime exposure to asbestos was assessed for each of the 141 mesothelioma cases observed in Lower Normandy during this time period, and 105 cases could be related to a possible, probable, or very probable occupational exposure to this mineral. Data about notification and compensation of these occupational diseases were gathered with the help of all health insurance organisms concerned.ResultsExcept for five cases in which insurance conditions did not allow any compensation, compensation of occupational mesothelioma occurred in 85% of the cases. This high rate was probably the result of the existence of an early asbestos industry in this region, and of the particular awareness of the Norman population about asbestos-related diseases, as well as of the epidemiological follow-up of mesothelioma in Lower Normandy. When notified for compensation, all cases but one were actually compensated, and the lag-time between notification and compensation proved to decrease since 1995, with an average delay reaching 91,1 days in 2002. Patients who did not report their disease were older than those who did, and the lack of knowledge of medical practitioners about compensation procedures seems to be an important matter in this issue.ConclusionIn order to improve the rate of compensation of occupational malignant mesothelioma cases, information about the usual occupational origin of the disease should be delivered systematically to the general practitioner of each patient. This could be done by pathologists, when they diagnose malignant mesothelioma, and/or by medical examiners when sickness benefits are sought, or even by the epidemiological center of death causes (INSERM, CépiDc), for the beneficiaries of patients who died from malignant mesothelioma.     

Spatio-seasonal variation of airborne asbestos concentration in urban areas of Shiraz,Iran

Background: Asbestos fiber is mainly released from friction product in brakes and clutch linings and from reinforcing agent in the asbestos-cement industry. It leads to serious health problem such as mesothelioma and lung cancer. The objectives of this study were to monitor the levels of asbestos fibers in ambient air of Shiraz, Iran during 2014, and to draw its GIS distribution map for the city.

Methods: Samples were collected by mixed cellulose ester filters mounted on an open-faced filter holder using a SKC sampling pump. Fiber counting was conducted using both phase contrast microscopy (PCM) method to determine total fibers, and scanning electron microscopy (SEM) method to identify non-asbestos from asbestos fibers.

Results: The average concentrations of asbestos fibers in ambient air of the city were 1.11 ± 0.25 PCM f/l and 12.21 ± 2.52 SEM f/l. The highest concentration of asbestos fibers was measured in Valiasr square amounting 1.96 ± 0.34 PCM f/l and 16.87 ± 2.14 SEM f/l.

Conclusions: The average of asbestos fibers in all sampling points was higher than the WHO guideline (0.05 PCM f/l, 2.2 SEM f/l). This may be attributed to the frequently occurrence of heavy traffic, the existence of relevant industries in and around the city, and the topographic characteristics of the city. Thus, product substitution, traffic smoothing and industrial sites relocating are suggested to eliminate the asbestos fibers emission.     

Preface

Abstract

Background: Out of 143 countries that consumed asbestos between 2003 and 2007, only 44 have banned asbestos. This study tried to explain why some countries have banned asbestos while others have not, based on a synthesis that asbestos ban policy of a country will rely on a process of cognition of threats and exploration of safer alternatives.

Method: As we hypothesized that increased social cost of mesothelioma, capacity of health-related infrastructures, and policy diffusion from adjacent countries were related to asbestos ban adoption, published databases of asbestos ban years, mesothelioma mortality, country rankings in health care and human rights standings, and distribution of banning countries over 14 regions were analyzed accordingly.

Results: The average mesothelioma death rate was significantly higher for countries with asbestos bans than in those with no ban (4·59 versus 1·83/million). No-ban countries had less well-developed health-related infrastructures. Among European countries, there was a tendency toward geographical diffusion of asbestos ban policy from Nordic to Western and then other European countries over the years. Even though aberrant cases were also noted where bans were instituted even without mesothelioma database, these were rather exceptions than rules.

Conclusion: Risk cognition is a complex process, but the presence of well-functioning health infrastructures, as well as the increased social cost of mesothelioma, that can make the plight of asbestos victims visible to the eyes of public and policy makers, may have contributed to this process. Asbestos ban policy from adjacent countries might have facilitated the adoption of alternative solutions.     

A baseline profile of asbestos in the US-affiliated Pacific islands

Abstract

Asbestos is a recognized occupational and environmental hazard in the Asia-Pacific region, yet information regarding asbestos consumption, exposure, and asbestos-related diseases in the US-affiliated Pacific Islands (USAPIs) is scarce, and the situation regarding asbestos in these islands, particularly with regard to disease burden, surveillance, and health care capacity, is not well understood. Searching through scientific and “gray” literature and interviews with local cancer registry personnel and health professionals yielded no published data, only sufficient, indirect evidence of past and ongoing asbestos exposure, documented cases of mesothelioma and asbestosis, and minimal capacity for preventing and recognizing asbestos-related illnesses. Capacity and resource limitations within the USAPIs can impede regional progress in asbestos prevention and highlight the need for an integrated regional approach to address these data and capacity gaps. A regional mechanism to share expertise and resources and facilitate technical assistance to the USAPIs is urgently needed.     

Mercury and neuromotor function among children in a rural town in Chile

Background: Mercury (Hg) exposure from artisanal gold mining has adverse effects on the neuromotor function in adults. However, few studies have examined this relationship in children.

Objectives: To investigate the impact of Hg exposure on children’s neuromotor function.

Methods: Cross-sectional data on Hg risk factors and demographics were collected from n = 288 children (response = 68.9%). Based on complete cases (CCs) (n = 130) and multiple imputations (n = 288), associations between fingernail Hg and four different neuromotor function components were calculated using multiple logistic regression adjusted for confounders.

Results: Of the children, 11.1, 14.9, 63.9, and 10.4% had pathologic pure motor skills, adaptive fine motor skills, adaptive gross motor skills, and static balance, respectively. No significant association between fingernail Hg and any neuromotor component was found. However, Hg burning in the household was significantly associated with children’s pathologic pure motor skills (OR 3.07 95% CI 1.03–9.18).

Conclusion: Elemental Hg exposure in the household might have adverse long-term effects on children’s pure motor skills.     

Mesothelioma in Mongolia: case report

Background:

More than 80% of cases of mesothelioma worldwide have a history of asbestos exposure. In Mongolia, workers in coal burning thermal power plants (TPP) have widely utilized asbestos as an insulation material.

Methods:

We describe the case of a 47-year-old woman diagnosed with a malignant pleural mesothelioma. She worked in a TPP in Ulaanbaatar, Mongolia for 28 years.

Results:

A computer tomography (CT) scan showed a circumferential ring around her left lung, and tissues’ samples had a biphasic variant of mesothelioma with epithelioid and sarcomatoid components.

Discussion:

This is the first reported case of mesothelioma in Mongolia. We expect additional cases of mesothelioma, as well as other asbestos related diseases, will be identified in the future. In order to properly track asbestos related diseases in the country, we recommend the creation of an asbestos related disease registry.     

La ricostruzione dell’esposizione ad amianto in un’azienda tessile di produzione filati cucirini attraverso l’utilizzo di un’insolita fonte informativa

«Reconstruction of the asbestos exposure in a textile company producing sewing threads through the use of an unusual information source».Background:The Tuscan Regional Operating Center (ROC) of Malignant Mesotheliomas has identified a cluster of 11 cases of malignant mesothelioma occurred in a textile plant manufacturing sewing thread. Using the common research method, the ROC had not previously been able to identify the specific sources of asbestos exposure causing such a large cluster.Objectives:The ROC’s objective was to review all cases of the cluster and to better identify their occupational asbestos exposures.Methods:The cases’ occupational histories of asbestos exposure have been reviewed, using information deriving from the annual reports sent to the Tuscany Region since 1988 by all the asbestos removal companies according to the Law no. 257/1992, article 9, and from interviews to former employees of the plant.Results:The work cycle has been reconstructed and enriched with the new information about the asbestos presence and its uses in the plant. The eleven cases were all reclassified as “certainly occupational exposed” given that the new collected information depicted a widespread asbestos pollution of the workplace during the period of employment of all cases.Conclusions:Using different sources of information, in addition to those traditionally collected through questionnaires, to reconstruct past asbestos exposuresallowed us to clarify the existence of the cluster of mesothelioma cases and the highest level of occupational asbestos exposure was attributed to all cases with consequent activation of the medico-legal procedure.Key words: Asbestos, malignant mesothelioma, occupational exposure, textile, sewing threads     

Occupational and leisure-time physical activity and workload among construction workers – a randomized control study

Background: There is a lack of quantification of occupational physical activity (OPA) and leisure time physical activity (LTPA) among construction workers.

Objectives: To describe physical activity energy expenditure (PAEE), physical workload, and the effect of a PA-intervention among construction workers.

Methods: Sixty-seven Construction workers self-reported their physical activity (PA), had PA assessed directly (PAEE), and observed OPA using the tool “Posture, Activity, Tools and Handling.” The PA-intervention (Intervention; n = 29, Controls; n = 24) included 3x20-min training/week for 12 weeks.

Results: Baseline median OPA was 5036 MET-min/week and LTPA 2842 MET-min/week, p < 0.01. OPA directly recorded was (mean ± SE): 56.6 ± 3.2 J/kg/min and LTPA was: 35.7 ± 2.2 J/kg/min (p < 0.001). Manual material handling was performed for ≥ 25% of working time by more than 50% of the participants. Post-intervention, the training group reduced overall PAEE compared to the control group but not specifically during work.

Conclusions: OPA was within the maximum recommended level of 1/3 proposed in consensus guidelines but did not decrease with PA-intervention.     

Epidemiology of mesothelioma of the pericardium and tunica vaginalis testis

PurposeMalignant mesothelioma most commonly arises in the pleura and peritoneum but also occurs rarely at other anatomical sites with mesothelial tissue, namely, the pericardium and tunica vaginalis testis (TVT). This review provides a better understanding of the epidemiology of mesothelioma of these extrapleural sites.MethodsWe conducted a systematic review of the epidemiologic and clinical literature on pericardial mesothelioma and mesothelioma of the TVT. We also analyzed U.S. Surveillance, Epidemiology, and End Results cancer registry data to describe incidence patterns of these malignancies.ResultsAn etiologic role of asbestos exposure has been hypothesized for pericardial and TVT mesotheliomas, but no analytical case-control epidemiologic studies exist to test this relationship. A substantial proportion of cases with these malignancies report no known asbestos exposure. In large occupational cohorts with heavy asbestos exposures, no cases of pericardial or TVT mesothelioma have been reported. Trends in the incidence of these malignancies do not match those of pleural mesothelioma, which correspond to historical trends of commercial asbestos use. A male preponderance of pericardial mesothelioma is not evident.ConclusionsIn the absence of analytic epidemiologic studies, the etiologic role of environmental risk factors for mesothelioma of the pericardium and TVT remains elusive.     

Association between asbestos exposure and pericardial and tunica vaginalis testis malignant mesothelioma: a case–control study and epidemiological remarks

Objectives:The purposes of this study are to describe the epidemiology of pericardial and tunica vaginalis testis mesothelioma and assess the role of asbestos exposure for these rare diseases.Methods:Based on incident pericardial and tunica vaginalis testis mesothelioma cases collected from the Italian national mesothelioma registry (ReNaM) in the period 1993–2015, incidence rates, survival median period and prognostic factors have been evaluated. A case–control study has been performed to analyze the association with asbestos exposure (occupational and non-occupational) for these diseases.Results:Between 1993 and 2015, 58 pericardial (20 women and 38 men) and 80 tunica vaginalis testis mesothelioma cases have been registered with a mean annual standardized (world standard population as reference) incidence rates of 0.049 (per million) in men and 0.023 in women for the pericardial site, and 0.095 for tunica vaginalis testis mesothelioma. Occupational exposure to asbestos was significantly associated with the risk of the diseases [odds ratio (OR) 3.68, 95% confidence interval (CI) 1.85–7.31 and OR 3.42, 95% CI 1.93–6.04 in pericardial and tunica vaginalis testis mesothelioma, respectively]. The median survival was 2.5 months for pericardial and 33.0 months for tunica vaginalis testis mesotheliomas. Age was the main predictive factor for survival for both anatomical sites.Conclusions:For the first time in an analytical study, asbestos exposure was associated with pericardial and tunica vaginalis testis mesothelioma risk, supporting the causal role of asbestos for all anatomical sites. The extreme rarity of the diseases, the poor survival and the prognostic role of age have been confirmed based on population and nationwide mesothelioma registry data.     

Asbestos exposure and malignant lymphoma: a multicenter case–control study in Germany and Italy

Aims

To analyze the relationship between asbestos exposure and malignant lymphoma in a multicenter case–control study conducted in Germany and Italy according to a common core protocol.

Methods

Male and female patients with malignant lymphoma (n = 1,034) between 18 and 80 years of age were prospectively recruited in six study areas in Germany (Ludwigshafen/Upper Palatinate, Heidelberg/Rhine-Neckar-County, Würzburg/Lower Frankonia, Hamburg, Bielefeld/East Westphalia, and Munich) and in two study areas in Sardinia, Italy (Cagliari and Nuoro provinces). A total of 1,173 population control subjects were drawn from population registers. In a structured personal interview, we elicited a complete occupational history, including every occupational period that lasted at least 1 year. On the basis of job task-specific supplementary questionnaires, trained experts assessed the exposure to asbestos. As a measure of cumulative asbestos exposure on a time by intensity scale, fiber-years were calculated. 12 cases (1.2%) and 12 control subjects (1.0%) had a cumulative asbestos exposure of more than 2.6 fiber-years (highest exposure category according to the 90th percentile of exposed control subjects). Odds ratios (OR) and 95% confidence intervals (CI) were calculated using unconditional logistic regression analysis adjusted for age, sex and study region. Patients with specific lymphoma sub-entities were additionally compared with the entire control group.

Results

We observed no statistically significant association between cumulative asbestos exposure and the risk of any lymphoma subtype. An elevated risk was found for the association between exposure to more than 2.6 fiber-years and multiple myeloma (OR = 6.0; 95% CI 1.4–25.1); however, numbers were small (n = 3 cases, all of them from Italy; n = 12 control subjects).

Conclusions

Our study does not support an association between asbestos exposure and risk of malignant lymphoma.     

Tuscany mesothelioma registry (1988-2000): evaluation of asbestos exposure

BACKGROUND: The Tuscany Mesothelioma Register (ARTMM) records pleural malignant mesothelioma cases of Tuscany residents, diagnosed by histological, cytological, or clinical (radiography or computerized tomography) examinations. The ARTMM began in 1988 and estimates mesothelioma incidence in Tuscany and collects information on past asbestos exposure of mesothelioma cases. OBJECTIVES: The aim of this paper was to describe the incidence of pleural mesothelioma cases in Tuscany and to analyse their possible past asbestos exposures. METHODS: We considered pleural mesothelioma cases recorded in ARTMM in the period 1988-2000 and interviews collected for these cases. In order to identify past asbestos exposure in the occupational and non-occupational history of patients, interviews were carried out using a standardised questionnaire. RESULTS: In the period 1988-2000, 494 pleural malignant mesothelioma cases were recorded in the ARTMM; 82% were males. In the periods 1988-1993, 1994-1997, 1998-2000 the incidence rates, standardised on the Italian population (per 100,000), were respectively 1.15, 1.57, 2.58 among males; 0.29; 0.27; 0.29 among females. Information on occupational history was collected for 418 mesothelioma patients (85% of recorded cases): 173 mesothelioma cases were directly interviewed; for 245 cases relatives or work colleagues were interviewed. Occupational asbestos exposure was ranked as certain, probable or possible in 72% of the interviewed cases (80% of males; 20% of females). Environmental and non-occupational asbestos exposure was identified in 1% of males, and 3% of females. In 24% of the interviewed cases (15% of males; 74% of females) no known asbestos exposure was identified. Occupational asbestos exposure occurred in maritime activities (shipyards, dock work, merchant and regular Navy), the building industry, railway carriage construction and maintenance, rail transport, textile industries (mainly rag sorting), electricity production, asbestos cement manufacture, chemical, iron and steel industries and in glass manufacturing. In Tuscany two areas are distinguished for their well-documented and massive use of asbestos: the coastal areas (Livorno and Massa Carrara) for maritime activities, and the areas of Pistoia and Arezzo for railway carriage construction and repair. Mesothelioma incidence rates in these areas are the highest in the whole region. CONCLUSIONS: Further investigation is needed in order to identify unknown asbestos uses and consequent exposure, in particular for females. Uncertainty as regards occurrence of asbestos exposure persists in the textile industries where the mesothelioma epidemics have not yet declined. Research hypotheses are addressed on the re-use of jute bags previously containing asbestos, therefore collection of further information on periods and methods of this recycling activity is essential.     

Asbestos and Peritoneal Mesothelioma among College-educated Men

Abstract

The proportion of peritoneal mesotheliomas among all mesotheliomas has been decreasing, leading some to suggest that peritoneal mesothelioma occurs only after high levels of exposure to asbestos. To investigate the relationship between asbestos exposure and the development of peritoneal mesothelioma, a case–control study examined 40 cases of primary peritoneal mesothelioma from a single institution. This series differed from previous reports in that 75% of the cases and controls had attended college. Results show an odds ratio of 6.6 for asbestos exposure among this group of primary peritoneal mesothelioma cases with relatively slight asbestos exposures.     

Penicillin dust exposure and penicillin resistance among pharmaceutical workers in Tehran,Iran

Background: Antimicrobial resistance (AMR) adversely impacts the prevention and treatment of a wide range of infections and is considered as a serious threat to global public health. Occupational-related AMR is a neglected area of research.

Objective: To assess exposure to penicillin dust, penicillin active materials, and to report the frequency of penicillin resistance among pharmaceutical workers in Tehran, Iran.

Methods: A quasi-experimental study was conducted among workers on a penicillin production line in a pharmaceutical company (n = 60) and workers in a food producing company (n = 60). Data were collected via survey, air sampling, and throat swab.

Results: The mean overall concentrations of penicillin dust and penicillin active material were 6.6 and 4.3 mg/m³, respectively, in the pharmaceutical industry. Streptococcus pneumoniae (S. pneumoniae) was detected in 45% (27) individuals in the exposed group, 92.6% of which showed penicillin resistance. Resistance was significantly higher among workers in penicillin production line (p = 0.014).

Conclusions: High level of AMR among workers in penicillin production line is a health risk for the workers as well as society as a whole through the spread of drug resistant micro-organisms.     

Cancer in ex‐asbestos cement workers in Israel, 1953–1992

A cohort of 3,057 male workers employed in an asbestos‐cement plant using 90% chrysotile‐10% crocidolite, located in Northern Israel, was followed from 1953–1992 for incidence and mortality from cancer. In the years 1978–1992, the cohort had an elevated risk for all malignant neoplasms combined (n > 153, SIR > 117, ns), lung cancer (n > 28, SIR > 135, ns), mesothelioma (n > 21; SIR >5000, p > .0001), unspecified pleural cancer (n > 5; SIR > 278 , P > .0001), and liver cancer (n > 7, SIR 290, ns). Risks for colo‐rectal (n > 19; SIR > 79, ns), bladder (n = 12, SIR 69) and renal cancers (n > 5, SIR 104) were less than expected. Risk for mesothelioma showed a sharp risk gradient with duration of exposure, increasing from 1 per 625 for those employed less than 2 years to 1 per 4.5 workers employed over 30 years. The ratio of mesothelioma to excess lung cancer cases was 2.9 to 1, or 3.6 to 1, if pleural cases of unspecified origin were included; the pleura to peritoneum ratio of verified mesothelioma cases was 20 to 1. This atypically high ratio of mesothelioma to excess lung cancer cases is suggested to be the combined result of high past asbestos exposures in the workers and their low prior risk for lung cancer, and possibly, relatively early smoking cessation in relation to asbestos exposure. Am. J. Ind. Med. 35:1–8, 1999. © 1999 Wiley‐Liss, Inc.     

Mesothelioma associated with use of drywall joint compound: a case series and review of literature

Abstract

Background: Drywall joint compound contained asbestos fibers, primarily chrysotile, in the 1950s through the 1970s. Workers in a variety of construction trades and homeowners were exposed to respirable asbestos from the use of these products, including during handling, mixing, sanding, and sweeping. Disturbance of in-place asbesto-containing joint compound continues to be a potential source of exposure during demolition or repair of wallboard. Studies from the 1970s and 1980s report air fiber measurements above current and historic regulatory limits during intended usage, and typical asbestos-related disease in drywall construction workers.

Objectives: We present three cases of mesothelioma in which the only known exposure to asbestos was from joint compound and review the literature on exposure circumstances, dose and fiber types.

Conclusions: Physicians treating mesothelioma patients should obtain a history of exposure to these products during work or home remodeling.     

Changes of mesothelin and osteopontin levels over time in formerly asbestos-exposed power industry workers

Purpose

In patients developing malignant pleural mesothelioma (MPM) or lung cancer, using effective tumour markers is the quickest way to ensure early diagnosis and improve survival time. The aim of our study was to assess the influence of age and asbestos exposure on the blood levels of the proposed tumour markers, mesothelin and osteopontin, and to determine the change of these markers over time.

Methods

We analysed 3,329 blood samples of 2,262 participants including 1,894 formerly asbestos-exposed power industry workers, a mixed group of 266 participants with an unknown history of asbestos exposure and a group of 102 non-asbestos-exposed controls. Marker concentrations were determined using commercial ELISA kits.

Results

While age had a strong influence on marker levels, there was no association between exposure duration or benign asbestos-related disease and marker levels. In order to assess the maximum increase that can be expected to occur in asbestos-exposed workers those with an at least 10 % increase were selected (n = 290 for mesothelin and n = 81 for osteopontin). The 95th percentile of the annual change was 0.402 nmol/l for mesothelin and 334 ng/ml for osteopontin. In two patients with MPM and five with lung cancer, we could obtain more than one marker result before the diagnosis was made. Both MPM patients showed a steep increase of mesothelin levels.

Conclusions

Fixed cut-off values for deciding between intensive clinical work-up and continued surveillance appeared inadequate for the evaluated markers. While general conclusions cannot be drawn, we can say that the results of the two patients would be consistent with a mesothelin increase between 6 and 18 months before clinical symptoms developed.     

Asbestos related diseases from environmental exposure to crocidolite in Da-yao,China. I. Review of exposure and epidemiological data

Background: Scattered patches of crocidolite, one form of asbestos, were found in the surface soil in the rural county of Da-yao in southwestern China. In 1983, researchers from the West China University of Medical Sciences (WCUMS) discovered that residents of two villages in Da-yao had hyperendemic pleural plaques and excessive numbers of pleural mesotheliomas.

Aims: To review and summarise epidemiological studies, along with other relevant data, and to discuss the potential contribution to environmental risk assessment.

Methods: This report is based on a review of several clinical/epidemiological studies conducted by WCUMS researchers since 1984, which included one cross sectional medical examination survey, one clinical/pathological analysis of 46 cases of mesothelioma, and three retrospective cohort mortality studies. Additional information acquired from reviewing original data first hand during a personal visit along with an interview of medical specialists from Da-yao County Hospital was also incorporated.

Results: The prevalence of pleural plaque was 20% among peasants in Da-yao over 40 years of age in the cross sectional survey. The average number of mesothelioma cases was 6.6 per year in the 1984–95 period and 22 per year in the 1996–99 period, in a population of 68 000. For those mesothelioma cases that were histology confirmed, there were 3.8 cases/year in the first period and 9 cases/year in the second. Of the 2175 peasants in this survey, 16 had asbestosis. Lung cancer deaths were significantly increased in all three cohort studies. The annual mortality rate for mesothelioma was 85 per million, 178 per million, and 365 per million for the three cohort studies, respectively. The higher exposed peasants had a fivefold increased mesothelioma mortality compared to their lower exposed counterparts. There were no cases of mesothelioma in the comparison groups where no crocidolite was known to exist in the environment. In the third cohort study, almost one of five cancer deaths (22%) was from mesothelioma. The ratio of lung cancer to mesothelioma deaths was low for all three studies (1.3, 3.0, and 1.2, respectively).

Conclusions: The observation of numerous mesothelioma cases at Da-yao was a unique finding, due mainly to their lifetime exposure to crocidolite asbestos. The finding of cases dying at a younger age and the relatively high ratio of mesothelioma cases to lung cancer could also be another unique result of lifetime environmental exposure to crocidolite asbestos. Although the commercial use of crocidolite has been officially banned since 1984, the incidence of mesothelioma has continued to show a steady increase, particularly among peasants. Since the latency of mesothelioma is approximately 30–40 years, the ban had little effect in the 1990s. The increased awareness and changes in diagnosis over time may also contribute to the increase. Furthermore, exposure to asbestos stoves and walls continued. The government implemented reduction of these exposures. However, from a public health standpoint, the most important issue is the complete avoidance of further exposure to asbestos.