Exposure to asbestos-containing vermiculite ore and respiratory symptoms among individuals who were children while the mine was active in Libby, Montana

Measurement of asbestos emissions associated with demolition of abandoned residential dwellings

Many cities are revitalizing their urban cores through the demolition of abandoned residential dwellings (ARDs). However, data regarding the emissions of asbestos during such an operation are sparse. We measured airborne asbestos emissions from emergency demolitions (demolitions on structures deemed too dangerous to enter and remove asbestos) of ARDs in Detroit. High-flow air sampling was conducted during ARD demolitions. Air samples were analyzed using Phased Contrast Microscopy (PCM), and a subset using Transmission Electron Microscopy (TEM). One hundred and one air samples were collected on 25 emergency demolitions. Fifty-four of the 101 PCM samples (53%) exceeded the limit of detection (LOD). However, only 2 of 46 TEM samples (4%) exceeded the LOD for asbestos; these latter samples were from two different demolitions and each contained a single chrysotile asbestos fiber. Using conservative exposure assumptions and commonly-accepted risk estimation formulae, we estimated the lifetime risk of mesothelioma and lung cancer combined to be less than one case per one million people. Emissions of airborne asbestos during emergency (unabated) ARD demolition operations appear to be negligible. As a result, the associated health risk for asbestos-related disease is also negligible. Reconsideration of current regulatory mandates for asbestos abatement in ARDs may be warranted.

Follow-Up of the Libby, Montana Screening Cohort: A 17-Year Mortality Study

OBJECTIVE

To evaluate mortality patterns among participants in a community-based screening program for asbestos-related disease.

METHODS

We calculated standardized mortality ratios (SMRs) and stratified results by exposure group (three occupational exposure groups, household contacts and residents without occupational asbestos exposure) and by radiographic abnormality presence.

RESULTS

All-cause mortality (15.8%; 1,429/8,043) was statistically lower than expected. Asbestosis was statistically elevated in all exposure groups. Lung cancer was moderately associated with vermiculite miner/miller employment. Mesothelioma was elevated in that same exposure group and among residents. Systemic autoimmune disease mortality was also elevated. Radiographic parenchymal abnormalities were associated with lung cancer mortality.

CONCLUSION

In addition to asbestos-related mortality in occupational exposure groups, this initial follow-up of this cohort also shows elevated mortality for some asbestos-related causes in non-occupational exposure groups.

Cancer incidence and mortality associated with non-occupational and low dose exposure to Libby vermiculite in Minnesota

BACKGROUND

A vermiculite processing plant in a Minneapolis, Minnesota neighborhood utilized asbestos-containing ore from Libby, Montana from the late 1930's until 1989. Multiple pathways of exposure to Libby asbestos were characterized in a cohort of over 6000 plant workers and residents living near the plant.

OBJECTIVE

We conducted a cohort linkage study to assess the impact of cumulative low dose exposure and the role of occupational history on asbestos-related mortality and cancer morbidity among cohort members residing near a vermiculite plant.

METHODS

Cohort members alive in 1988 (n = 5848) were linked to the Minnesota Cancer Surveillance System to identify incident cases of mesothelioma, lung cancer, and all-cancer diagnosed from 1988 to 2010. Proportional incidence ratios (PIRs) were calculated for mesothelioma and lung cancer. Vital status and cause of death were ascertained from Minnesota vital records and the National Death Index (1988-2011). Mortality rates of the cohort (2001-2011) for asbestos-related outcomes were compared to the Minnesota population to estimate standardized mortality ratios (SMRs) and stratified by gender, exposure, and occupational history categories.

RESULTS

We identified seven cases of mesothelioma, with elevated incidence only in females (PIR = 11.76, 95% CI: 3.17, 30.12). Lung cancer was elevated in both genders: PIR = 1.54 (95% CI: 1.19, 2.0) in males and 1.62 (95% CI: 1.21, 2.12) in females. We found elevated mortality from COPD, lung cancer, and mesothelioma among females (SMR for mesothelioma in females = 18.97, CI: 3.91, 55.45), among the 546 deaths identified. All four deaths from mesothelioma occurred in the >75th percentile of exposure (>0.0156 fiber/cc x months). The SMR for lung cancer and all respiratory cancer was elevated even after controlling for occupation.

CONCLUSIONS

Community exposure to Libby amphibole asbestos from a vermiculite processing plant is associated with increased risk of COPD, lung cancer and mesothelioma incidence and mortality, most notably among females, and is likely to remain a public health issue for years to come.

Childhood exposure to Libby amphibole asbestos and respiratory health in young adults

OBJECTIVES

Vermiculite ore containing Libby amphibole asbestos (LAA) was mined in Libby, MT, from the 1920s-1990. Recreational and residential areas in Libby were contaminated with LAA. This objective of this study was to characterize childhood exposure to LAA and investigate its association with respiratory health during young adulthood.

METHODS

Young adults who resided in Libby prior to age 18 completed a health and activity questionnaire, pulmonary function testing, chest x-ray and HRCT scan. LAA exposure was estimated based on participant report of engaging in activities with potential LAA exposure. Quantitative LAA estimates for activities were derived from sampling data and literature reports.

RESULTS

A total of 312 participants (mean age 25.1 years) were enrolled and reported respiratory symptoms in the past 12 months including pleuritic chest pain (23%), regular cough (17%), shortness of breath (18%), and wheezing or whistling in the chest (18%). Cumulative LAA exposure was significantly associated with shortness of breath (aOR = 1.12, 95% CI 1.01-1.25 per doubling of exposure). Engaging in recreational activities near Rainy Creek Road (near the former mine site) and the number of instances heating vermiculite ore to make it expand or pop were also significantly associated with respiratory symptoms. LAA exposure was not associated with pulmonary function or pleural or interstitial changes on either chest x-ray or HRCT.

CONCLUSIONS

Pleural or interstitial changes on x-ray or HRCT were not observed among this cohort of young adults. However, childhood exposure to LAA was significantly associated with respiratory symptoms during young adulthood. Pleuritic chest pain, in particular, has been identified as an early symptom associated with LAA exposure and therefore warrants continued follow-up given findings of progressive disease in other LAA exposed populations.

Pulmonary abnormalities as a result of exposure to Libby amphibole during childhood and adolescence-The Pre-Adult Latency Study (PALS)

BACKGROUND

The purpose of Pre-Adult Latency Study was to evaluate lung findings among adults who had been environmentally exposed to Libby Amphibole only during childhood and adolescence.

METHODS

Recruitment was restricted to volunteers who attended primary and/or secondary school, lived in Libby, MT, prior to age 23 years for males and 21 years for females and subsequently left the area. Subjects completed exposure and respiratory questionnaires, underwent pulmonary function tests (PFTs), and chest CT scans. A Pleural Score was calculated for degree and extent of pleural thickening. Logistic regression and multivariate linear regression were used.

RESULTS

Of the 219 who met inclusion criteria, 198 participated. Pleural thickening was found in 96 (48%) of 198 participants. In almost half of these, it was of the lamellar type, not generally seen in exposure to other asbestos. Environmental Libby amphibole exposure was associated with pleural thickening, and the likelihood of pleural thickening increased with the number of years lived in the area. An inverse association between Pleural Score and PFT was found, which remained significant for FVC and DLco after additional sensitivity analyses.

CONCLUSIONS

Cumulative environmental exposure was associated with risk of pleural thickening. Among this cohort, quantitative measures of pleural thickening were associated with decreased PFT. Am. J. Ind. Med. 60:20-34, 2017. © 2016 Wiley Periodicals, Inc.

Principal components analysis to identify influences on research communication and engagement during an environmental disaster

OBJECTIVES

To discern community attitudes towards research engagement in Libby, Montana, the only Superfund site for which a public health emergency has been declared.

STUDY DESIGN

Survey study of convenience samples of residents near the Libby, Montana Superfund site.

PARTICIPANTS

Residents of the Libby, Montana area were recruited from a local retail establishment (N=120, survey 1) or a community event (N=127, survey 2).

MEASURES

Two surveys were developed in consultation with a Community Advisory Panel.

RESULTS

Principal components of survey 1 showed four dimensions of community members' attitudes towards research engagement: (1) researcher communication and contributions to the community, (2) identity and affiliation of the researchers requesting participation, (3) potential personal barriers, including data confidentiality, painful or invasive procedures and effects on health insurance and (4) research benefits for the community, oneself or family. The score on the first factor was positively related to desire to participate in research (r=0.31, p=0.01). Scores on factors 2 and 3 were higher for those with diagnosis of asbestos-related disease (ARD) in the family (Cohen's d=0.41, 0.57). Survey 2 also found more positive attitudes towards research when a family member had ARD (Cohen's d=0.48).

CONCLUSIONS

Principal components analysis shows different dimensions of attitudes towards research engagement. The different dimensions are related to community members' desire to be invited to participate in research, awareness of past research in the community and having been screened or diagnosed with a health condition related to the Superfund contaminant.

My Winding Road: From Microbiology to Toxicology and Environmental Health

I would certainly never have predicted that I would become the director of the National Institute of Environmental Health Sciences (NIEHS) and the National Toxicology Program (NTP) when I was a Jewish girl growing up in Teaneck, New Jersey. My family stressed the importance of education. Yet for a girl there were many not-so-subtle suggestions that the appropriate careers were in teaching or nursing, and the most important thing was to be a wife and mother. Well, I can't disagree with the latter, although I would have to add grandmother to that list of achievements. My parents were both college graduates, but my mom only taught high school English for one year before leaving the field to start our family. My dad returned from World War II and joined his brother in accounting. After my first sister was born, my father joined my mother's family jewelry business and helped to open a second retail store. My mother helped my dad out during the busy times—Christmas and wedding season—but otherwise focused on our growing family of three girls and one boy. This became increasingly challenging when it became clear that my little brother was severely retarded and would require extra care.

Current Research and Opportunities to Address Environmental Asbestos Exposures

Asbestos-related diseases continue to result in approximately 120,000 deaths every year in the United States and worldwide. Although extensive research has been conducted on health effects of occupational exposures to asbestos, many issues related to environmental asbestos exposures remain unresolved. For example, environmental asbestos exposures associated with a former mine in Libby, Montana, have resulted in high rates of nonoccupational asbestos-related disease. Additionally, other areas with naturally occurring asbestos deposits near communities in the United States and overseas are undergoing investigations to assess exposures and potential health risks. Some of the latest public health, epidemiological, and basic research findings were presented at a workshop on asbestos at the 2014 annual meeting of the Society of Toxicology in Phoenix, Arizona. The following focus areas were discussed: a) mechanisms resulting in fibrosis and/or tumor development; b) relative toxicity of different forms of asbestos and other hazardous elongated mineral particles (EMPs); c) proper dose metrics (e.g., mass, fiber number, or surface area of fibers) when interpreting asbestos toxicity; d) asbestos exposure to susceptible populations; and e) using toxicological findings for risk assessment and remediation efforts. The workshop also featured asbestos research supported by the National Institute of Environmental Health Sciences, the Agency for Toxic Substances and Disease Registry, and the U.S. Environmental Protection Agency. Better protection of individuals from asbestos-related health effects will require stimulation of new multidisciplinary research to further our understanding of what constitutes hazardous exposures and risk factors associated with toxicity of asbestos and other hazardous EMPs (e.g., nanomaterials).

Childhood exposure to Libby amphibole during outdoor activities

Residents of Libby, MT were exposed to amphibole asbestos through multiple environmental pathways. Previous exposure characterization has primarily relied on qualitative report of these exposure activities. The objectives of this study were to describe available data from the US EPA preremediation actions for Libby amphibole (LA) exposure in Libby, MT and develop an approach to characterize outdoor residential exposure to LA among children. Homes in Libby, MT included in the US EPA preremediation Contaminant Screening Survey (CSS) were categorized by the presence of interior and/or exterior visible vermiculite and concentrations of LA were measured in samples of dust and soil. Airborne exposure to LA while digging/gardening, raking, and mowing were estimated using US EPA activity-based sampling (ABS) results. Residential histories and frequency/duration of childhood activities were combined with ABS to demonstrate the approach for estimating potential exposure. A total of 3154 residential properties participated in the CSS and 44% of these had visible exterior vermiculite. Airborne concentrations of LA where there was visible vermiculite outdoors were 3-15 times higher during digging/gardening, raking, and mowing activities compared with homes without visible outdoor vermiculite. Digging and gardening activities represented the greatest contribution to estimated exposures and 73% of the participants reported this activity before the age of 6 years. This methodology demonstrated the use of historical preremediation data to estimate residential exposures of children for specific activities. Children younger than age 6 years may have been exposed to LA while digging/gardening, especially at homes where there is visible outdoor vermiculite. This approach may be extended to other activities and applied to the entire cohort to examine health outcomes.

Use of direct versus indirect preparation data for assessing risk associated with airborne exposures at asbestos-contaminated sites

At asbestos-contaminated sites, exposure assessment requires measurement of airborne asbestos concentrations; however, the choice of preparation steps employed in the analysis has been debated vigorously among members of the asbestos exposure and risk assessment communities for many years. This study finds that the choice of preparation technique used in estimating airborne amphibole asbestos exposures for risk assessment is generally not a significant source of uncertainty. Conventionally, the indirect preparation method has been less preferred by some because it is purported to result in false elevations in airborne asbestos concentrations, when compared to direct analysis of air filters. However, airborne asbestos sampling in non-occupational settings is challenging because non-asbestos particles can interfere with the asbestos measurements, sometimes necessitating analysis via indirect preparation. To evaluate whether exposure concentrations derived from direct versus indirect preparation techniques differed significantly, paired measurements of airborne Libby-type amphibole, prepared using both techniques, were compared. For the evaluation, 31 paired direct and indirect preparations originating from the same air filters were analyzed for Libby-type amphibole using transmission electron microscopy. On average, the total Libby-type amphibole airborne exposure concentration was 3.3 times higher for indirect preparation analysis than for its paired direct preparation analysis (standard deviation = 4.1), a difference which is not statistically significant (p = 0.12, two-tailed, Wilcoxon signed rank test). The results suggest that the magnitude of the difference may be larger for shorter particles. Overall, neither preparation technique (direct or indirect) preferentially generates more precise and unbiased data for airborne Libby-type amphibole concentration estimates. The indirect preparation method is reasonable for estimating Libby-type amphibole exposure and may be necessary given the challenges of sampling in environmental settings. Relative to the larger context of uncertainties inherent in the risk assessment process, uncertainties associated with the use of airborne Libby-type amphibole exposure measurements derived from indirect preparation analysis are low. Use of exposure measurements generated by either direct or indirect preparation analyses is reasonable to estimate Libby-type Amphibole exposures in a risk assessment.

Mesothelioma incidence in 50 states and the District of Columbia, United States, 2003-2008

BACKGROUND

The decline in asbestos use in the United States may impact mesothelioma incidence.

OBJECTIVE

This report provides national and state-specific estimates of mesothelioma incidence in the United States using cancer surveillance data for the entire US population.

METHODS

Data from the National Program for Cancer Registries and the Surveillance, Epidemiology, and End Results program were used to calculate incidence rates and annual percent change.

RESULTS

During 2003-2008, an average of 1.05 mesothelioma cases per 100 000 persons were diagnosed annually in the United States; the number of cases diagnosed each year remained level, whereas rates decreased among men and were stable among women.

CONCLUSION

US population-based cancer registry data can be used to determine the burden of mesothelioma and track its decline. Even 30 years after peak asbestos use in the United States, 3200 mesothelioma cases are diagnosed annually, showing that the US population is still at risk.

All-cause mortality and cancer incidence among adults exposed to blue asbestos during childhood

BACKGROUND

There are few data on the long-term health outcomes of exposure to asbestos in childhood. This study investigated cancer and mortality of adults exposed to blue asbestos as children.

METHODS

Data linkage to relevant health registries was used to identify cancers and mortality in a cohort of adults (n = 2,460) that had lived in an asbestos mining town during their childhood (<15 years).

RESULTS

There were 217 (93 female) incident cancers and 218 (70 female) deaths among the cohort. Compared with the Western Australian population females had elevated mesothelioma, ovarian and brain cancers, and increased "all cause" and "all cancer" mortality. Males had elevated mesothelioma, leukemia, prostate, brain, and colorectal cancers, and excess mortality from "all causes," "all cancers," circulatory disease, diseases of the nervous system, and accidents.

CONCLUSION

Exposure to blue asbestos in childhood is associated with an increased risk of cancer and mortality in adults.

Sumas Mountain chrysotile induces greater lung fibrosis in Fischer344 rats than Libby amphibole, El Dorado tremolite, and Ontario ferroactinolite

The physical properties of different types of asbestos may strongly affect health outcomes in exposed individuals. This study was designed to provide understanding of the comparative toxicity of naturally occurring asbestos (NOA) fibers including Libby amphibole (LA), Sumas Mountain chrysotile (SM), El Dorado tremolite (ED), and Ontario ferroactinolite (ON) cleavage fragments. Rat-respirable fractions (PM₂.₅) were prepared by water elutriation. Surface area was greater for SM (64.1 m²/g) than all other samples (range: 14.1-16.2 m²/g), whereas mean lengths and aspect ratios (ARs) for LA and SM were comparable and greater than ED and ON. Samples were delivered via a single intratracheal (IT) instillation at doses of 0.5 and 1.5mg/rat. One day post-IT instillation, low-dose NOA exposure resulted in a 3- to 4-fold increase in bronchoalveolar lavage fluid (BALF) cellularity compared with dispersion media (DM) controls, whereas high-dose exposure had a more severe effect on lung inflammation which varied by source. Although inducing less neutrophilic inflammation than ON and ED, exposure to either LA or SM resulted in a greater degree of acute lung injury. Three months post-IT instillation, most BALF parameters had returned to control levels, whereas the development of fibrosis persisted and was greatest in SM-exposed rats (SM > LA > ON > ED). These data demonstrate that fiber length and higher AR are directly correlated with the severity of fibrosis and that, in the rat, exposure to SM is more fibrogenic than LA which suggests that there may be cause for concern for people at risk of being exposed to NOA from the Sumas Mountain landslide.

Association between cumulative fiber exposure and respiratory outcomes among Libby vermiculite workers

OBJECTIVE

To examine the association between cumulative fiber exposure and health outcomes in workers (n = 336) with Libby amphibole exposure.

METHODS

Exposure-response relationships were explored by the use of logistic regression, with cumulative fiber exposure modeled in categories and as a continuous variable.

RESULTS

The use of spline functions with lifetime cumulative fiber exposure as a continuous variable showed that the odds of localized pleural thickening were significantly elevated at less than 1 f/cc-y. Odds of parenchymal abnormalities, restrictive spirometry, and chronic bronchitis were also significantly elevated at 108, 166, and 24 f/cc-y, respectively.

CONCLUSIONS

The odds of several pulmonary health outcomes are correlated with cumulative exposure to Libby amphibole. That relatively low-lifetime cumulative exposures are associated with localized pleural thickening has implications for the non-cancer-risk assessment for Libby amphibole.

Libby vermiculite exposure and risk of developing asbestos-related lung and pleural diseases

PURPOSE OF REVIEW

The vermiculite ore formerly mined in Libby, Montana, contains asbestiform amphibole fibers of winchite, richterite, and tremolite asbestos. Because of the public health impact of widespread occupational and nonoccupational exposure to amphiboles in Libby vermiculite, numerous related studies have been published in recent years. Here we review current research related to this issue.

RECENT FINDINGS

Excess morbidity and mortality classically associated with asbestos exposure have been well documented among persons exposed to Libby vermiculite. Excess morbidity and mortality have likewise been documented among persons with only nonoccupational exposure. A strong exposure-response relationship exists for many malignant and nonmalignant outcomes and the most common outcome, pleural plaques, may occur at low lifetime cumulative exposures.

SUMMARY

The public health situation related to Libby, Montana, has led to huge investments in public health actions and research. The resulting studies have added much to the body of knowledge concerning health effects of exposures to Libby amphibole fibers specifically and asbestos exposure in general.

Amphibole asbestos in tree bark--a review of findings for this inhalational exposure source in Libby, Montana

In June 2009, the U.S. Environmental Protection Agency (EPA) designated the town of Libby, Montana, a public health emergency--the first and only time the EPA has made such a determination under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA). From about 1920 until 1990, the leading source of vermiculite ore for the United States and the world was from a mine near Libby. This vermiculite ore was contaminated with fibrous and asbestiform amphibole in veins throughout the deposit. Today, areas surrounding the abandoned vermiculite processing/mining facilities and much of the town of Libby are contaminated with these asbestos fibers, contributing to an outbreak of asbestos-related diseases in the Libby population. Trees in Libby and in forested areas surrounding the abandoned mine have accumulated amphibole asbestos fibers on their bark surface, providing for inhalational exposures. Several studies have been conducted to further understand this exposure pathway. To address exposures to the public, Libby amphibole (LA) was measured in personal breathing zone and Tyvek surface wipe samples collected during firewood harvesting simulations, as well as in the ash and emissions of woodstoves when amphibole-contaminated firewood was combusted. Occupational studies simulating wildland firefighting and routine U.S. Department of Agriculture (USDA) Forest Service activities have also been conducted in the forested areas surrounding the abandoned mine, demonstrating the potential for inhalational exposures during common regional workplace activities. We present a review of the findings of this emerging environmental health concern impacting not only the residents of Libby but applicable to other populations living near asbestos-contaminated areas.

The role of iron in Libby amphibole-induced acute lung injury and inflammation

Complexation of host iron (Fe) on the surface of inhaled asbestos fibers has been postulated to cause oxidative stress contributing to in vivo pulmonary injury and inflammation. We examined the role of Fe in Libby amphibole (LA; mean length 4.99 µm ± 4.53 and width 0.28 µm ± 0.19) asbestos-induced inflammogenic effects in vitro and in vivo. LA contained acid-leachable Fe and silicon. In a cell-free media containing FeCl(3), LA bound #17 µg of Fe/mg of fiber and increased reactive oxygen species generation #3.5 fold, which was reduced by deferoxamine (DEF) treatment. In BEAS-2B cells exposure to LA, LA loaded with Fe (FeLA), or LA with DEF did not increase HO-1 or ferritin mRNA expression. LA increased IL-8 expression, which was reduced by Fe loading but increased by DEF. To determine the role of Fe in LA-induced lung injury in vivo, spontaneously hypertensive rats were exposed intratracheally to either saline (300 µL), DEF (1 mg), FeCl(3) (21 µg), LA (0.5 mg), FeLA (0.5 mg), or LA + DEF (0.5 mg). LA caused BALF neutrophils to increase 24 h post-exposure. Loading of Fe on LA but not chelation slightly decreased neutrophilic influx (LA + DEF > LA > FeLA). At 4 h post-exposure, LA-induced lung expression of MIP-2 was reduced in rats exposed to FeLA but increased by LA + DEF (LA + DEF > LA > FeLA). Ferritin mRNA was elevated in rats exposed to FeLA compared to LA. In conclusion, the acute inflammatory response to respirable fibers and particles may be inhibited in the presence of surface-complexed or cellular bioavailable Fe. Cell and tissue Fe-overload conditions may influence the pulmonary injury and inflammation caused by fibers.

Modeling community asbestos exposure near a vermiculite processing facility: Impact of human activities on cumulative exposure

Contaminated vermiculite ore from Libby, Montana was processed in northeast Minneapolis from 1936 to 1989 in a densely populated urban residential neighborhood, resulting in non-occupational exposure scenarios from plant stack and fugitive emissions as well as from activity-based scenarios associated with use of the waste rock in the surrounding community. The objective of this analysis was to estimate potential cumulative asbestos exposure for all non-occupationally exposed members of this community. Questionnaire data from a neighborhood-exposure assessment ascertained frequency of potential contact with vermiculite processing waste. Monte Carlo simulation was used to develop exposure estimates based on activity-based concentration estimates and contact durations for four scenarios: S1, moved asbestos-contaminated waste; S2, used waste at home, on lawn or garden; S3, installed/removed vermiculite insulation; S4, played in or around waste piles at the plant. The simulation outputs were combined with air-dispersion model results to provide total cumulative asbestos exposure estimates for the cohort. Fiber emissions from the plant were the largest source of exposure for the majority of the cohort, with geometric mean cumulative exposures of 0.02 fibers/cc × month. The addition of S1, S2 and S3 did not significantly increase total cumulative exposure above background exposure estimates obtained from dispersion modeling. Activity-based exposures were a substantial contributor to the upper end of the exposure distribution: 90th percentile S4 exposure estimates are ∼10 times higher than exposures from plant emissions. Pile playing is the strongest source of asbestos exposure in this cohort, with other activity scenarios contributing less than from plant emissions.

Erionite exposure in North Dakota and Turkish villages with mesothelioma

Exposure to erionite, an asbestos-like mineral, causes unprecedented rates of malignant mesothelioma (MM) mortality in some Turkish villages. Erionite deposits are present in at least 12 US states. We investigated whether increased urban development has led to erionite exposure in the United States and after preliminary exploration, focused our studies on Dunn County, North Dakota (ND). In Dunn County, ND, we discovered that over the past three decades, more than 300 miles of roads were surfaced with erionite-containing gravel. To determine potential health implications, we compared erionite from the Turkish villages to that from ND. Our study evaluated airborne point exposure concentrations, examined the physical and chemical properties of erionite, and examined the hallmarks of mesothelial cell transformation in vitro and in vivo. Airborne erionite concentrations measured in ND along roadsides, indoors, and inside vehicles, including school buses, equaled or exceeded concentrations in Boyali, where 6.25% of all deaths are caused by MM. With the exception of outdoor samples along roadsides, ND concentrations were lower than those measured in Turkish villages with MM mortality ranging from 20 to 50%. The physical and chemical properties of erionite from Turkey and ND are very similar and they showed identical biological activities. Considering the known 30- to 60-y latency for MM development, there is reason for concern for increased risk in ND in the future. Our findings indicate that implementation of novel preventive and early detection programs in ND and other erionite-rich areas of the United States, similar to efforts currently being undertaken in Turkey, is warranted.

Applying definitions of "asbestos" to environmental and "low-dose" exposure levels and health effects, particularly malignant mesothelioma

Although asbestos research has been ongoing for decades, this increased knowledge has not led to consensus in many areas of the field. Two such areas of controversy include the specific definitions of asbestos, and limitations in understanding exposure-response relationships for various asbestos types and exposure levels and disease. This document reviews the current regulatory and mineralogical definitions and how variability in these definitions has led to difficulties in the discussion and comparison of both experimental laboratory and human epidemiological studies for asbestos. This review also examines the issues of exposure measurement in both animal and human studies, and discusses the impact of these issues on determination of cause for asbestos-related diseases. Limitations include the lack of detailed characterization and limited quantification of the fibers in most studies. Associated data gaps and research needs are also enumerated in this review.

The case for a global ban on asbestos

BACKGROUND

All forms of asbestos are now banned in 52 countries. Safer products have replaced many materials that once were made with it. Nonetheless, many countries still use, import, and export asbestos and asbestos-containing products, and in those that have banned other forms of asbestos, the so-called "controlled use" of chrysotile asbestos is often exempted from the ban. In fact, chrysotile has accounted for > 95% of all the asbestos used globally.

OBJECTIVE

We examined and evaluated the literature used to support the exemption of chrysotile asbestos from the ban and how its exemption reflects the political and economic influence of the asbestos mining and manufacturing industry.

DISCUSSION

All forms of asbestos, including chrysotile, are proven human carcinogens. All forms cause malignant mesothelioma and lung and laryngeal cancers, and may cause ovarian, gastrointestinal, and other cancers. No exposure to asbestos is without risk. Illnesses and deaths from asbestos exposure are entirely preventable.

CONCLUSIONS

All countries of the world have an obligation to their citizens to join in the international endeavor to ban the mining, manufacture, and use of all forms of asbestos. An international ban is urgently needed. There is no medical or scientific basis to exempt chrysotile from the worldwide ban of asbestos.