Rodney V. Metcalf

The Presence of Asbestos in the Natural Environment is Likely Related to Mesothelioma in Young Individuals and Women from Southern Nevada

Background: Inhalation of asbestos and other mineral fibers is known causes of malignant mesothelioma (MM) and lung cancers. In a setting of occupational exposure to asbestos, MM occurs four to eight times more frequently in men than in women, at the median age of 74 years, whereas an environmental exposure to asbestos causes the same number of MMs in men and women, at younger ages. Methods: We studied the geology of Nevada to identify mineral fibers in the environment. We compared MM mortality in different Nevada counties, per sex and age group, for the 1999 to 2010 period. Results: We identified the presence of carcinogenic minerals in Nevada, including actinolite asbestos, erionite, winchite, magnesioriebeckite, and richterite. We discovered that, compared with the United States and other Nevada counties, Clark and Nye counties, in southern Nevada, had a significantly higher proportion of MM that occurred in young individuals (<55 years) and in women. Conclusions: The elevated percentage of women and individuals younger than 55 years old, combined with a sex ratio of 1:1 in this age group and the presence of naturally occurring asbestos, suggests that environmental exposure to mineral fibers in southern Nevada may be contributing to some of these mesotheliomas. Further research to assess environmental exposures should allow the development of strategies to minimize exposure, as the development of rural areas continues in Nevada, and to prevent MM and other asbestos-related diseases.

Volcanic–plutonic links, plutons as magma chambers and crust–mantle interaction: a lithospheric scale view of magma systems

The northern Colorado River extensional corridor (NCREC, USA) provides an excellent record of coeval volcanic and mid- to upper-crustal ( Contemporaneous Miocene plutons span a similar compositional range (gabbro, diorite, quartz monzonite and granite) and were emplaced during a 4·5-million-year interval from 17 to 12·5 Ma. Geochemical and isotopic compositions and compositional trends allow direct correlation between plutonic and volcanic suites across the entire compositional range. Petrogenetic models demonstrate that intermediate magmas formed by a combination of magma mixing and fractional crystallisation involving mantle-derived mafic with crustal-derived felsic end-member magmas. Plutons exhibit a variety of features which suggest magma chamber processes, including (1) mafic cumulate sequences, (2) felsic cumulate sequences, and (3) magma mingling and advanced stages of magma mixing. Thus, the NCREC plutonic-volcanic record provides a link between magmatic processes recorded in pluton magma chambers and magmatic products in the form of extrusive igneous rocks. The NCREC plutons represent upper crustal magma chambers which connected volcanic eruptive centres to deeper-level magma chambers, and ultimately, to zones of mantle and crustal mel

Genesis and health risk implications of an unusual occurrence of fibrous NaFe3+-amphibole

Fibrous NaFe3+-amphiboles (winchite, richterite, and magnesioriebeckite) form primarily by alkali metasomatism from magmatic fluids expelled from carbonatite or peralkaline silicate magmas, and have been implicated in high rates of death and disease at Libby, Montana (USA). Fibrous NaFe3+-amphiboles, principally winchite and magnesioriebeckite, are found as fracture-fill veins and as replacement of magmatic hornblende in faulted margins of the dominantly subalkaline, metaluminous Miocene Wilson Ridge pluton, Mohave County, Arizona (USA). Here, the fibrous NaFe3+-amphiboles formed from hypersodic, high-![Graphic][1] hydrothermal fluids, which circulated through active faults as the pluton cooled through subsolidus temperatures. Halite deposits in adjacent Miocene sedimentary basins are the likely source of Na in the hydrothermal fluid. Amphibole fibers are <1 µm in diameter (typically <0.5 µm), vary from tens to hundreds of microns in length with length-to-width aspect ratios of 20:1 to over 100:1, are capable of dust transport and human inhalation, and should be considered hazardous. Transport and deposition of sediment eroded from primary pluton sources significantly increase the areal distribution of the fibrous amphiboles. Mitigation strategies require an understanding of the geologic settings where hazardous geologic materials are found. Our results suggest that fibrous NaFe3+-amphibole may be present in areas not previously considered at risk for naturally occurring asbestos. [1]: /embed/inline-graphic-1.gif

Geochemical evolution of the Precambrian Old Rag Granite, Virginia, U.S.A.: testing a UTh exploration model

Abstract The Old Rag Granite is one of several recognized units within the Virginia Blue Ridge Complex generally composed of Grenville-age gneisses and granitoid intrusive rocks. Chemical variation in the Old Rag Granite indicates simple orthomagmatic crystallization from the borders to the core of the pluton. Fractional crystallization of plagioclase, oxides, apatite and zircon accounts for much of the variation. Some trace elements, however, show anomalous behavior in the central part of the pluton. Y and Sr (and possibly Ba and Nb) are enriched whereas Rb and total REE are depleted in the central part of the pluton. Late crystallization of monazite could contribute to the observed REE patterns. It could not, however, account for Rb depletion and Sr enrichment, and no clear relationship between REE data and Th/U ratios are observed. The geochemical patterns indicate overall orthomagmatic crystallization overlain by a late-stage hydrothermal event. An exploration model for uraniferous granites, based upon the uranium deposits at Rossing and Bokan Mountain, included the Precambrian basement of central and northern Virginia in a list of proposed target areas. Geological, mineralogical and whole-rock chemical characteristics show a close association between the Old Rag Granite and the Rossing-type deposits. The uranium (mean 6.9 ppm, range 0.1–19.8 ppm) and thorium (mean 43 ppm, range 3.5–114 ppm) values are anomalous. Th/U ratios average 7.5 and are widely variable, indicating a decoupling of uranium from thorium. Neither U nor Th are lognormally distributed within the Old Rag Granite, requiring an explanation beyond simple removal of U by weathering. Rayleigh fractionation modeling shows that both U and Th, although probably distributed originally by closed-system fractionation, have been subsequently mobilized. Uranium can be lost in an oxidized form by secondary processes such as weathering or hydrothermal alteration. Thorium, however, will be affected only by hydrothermal processes. It is concluded that although primary fractionation was orthomagmatic, the Old Rag Granite was affected by late hydrothermal alteration whereby U was lost from the body and Th was redistributed. Three primary avenues for U migration are possible: (1) the rocks of the Saddleback Mountain Intrusive Suite which may have been contemporaneous with the Old Rag Granite; (2) Paleozoic fault zones that cut the Old Rag pluton; and (3) quartz veins, pegmatites, cupolas and roof pendants of the country-rock Nellysford gneiss that have been lost to erosion. The last option is preferred on geological and geochemical grounds. It is possible that the sedimentary uranium deposits of the adjacent Triassic Culpepper Basin were derived from eroded upper levels of the Old Rag Granite and like intrusives of the Virginia Blue Ridge Complex.

The emerging field of medical geology in brief: some examples

Emerging medical problems present medical practitioners with many difficult challenges. Emergent disciplines may offer the medical community new opportunities to address a range of these diseases. One such emerging discipline is medical geology, a science that is dealing with the influence of natural environmental factors on the geographical distribution of health in humans and animals. It involves the study of the processes and causes of diseases and also the use research findings to present solutions to health problems.

Reply to “No Increased Risk for Mesothelioma in Relation to Natural-Occurring Asbestos in Southern Nevada”

We appreciate the interest and review of our paper1 by Pinheiro and Jin2, as they provide us an opportunity to re-open a dialogue with the Department of Health and Human Services, Nevada, with whom Dr. Pinheiro is associated. Environmental epidemiology is a relatively recent science and, because it deals with small numbers and exposures that cannot be assessed on individuals, it uses specific methods that are different from classical cancer epidemiology3. Pinheiro and Jin: “the proper indicator of risk in a population or a subpopulation is the incidence rate”. While this is often true, it would be incorrect for this situation because most mesotheliomas are due to occupational exposure to asbestos4, therefore, the incidence (or mortality) rates reflect the process and/or use of asbestos in the studied area. Incidence rates cannot distinguish between occupational and environmentally-caused mesotheliomas. Occupational exposure leads to a mesothelioma Male:Female (M:F) sex-ratio of 4–8:1, with a mean age of diagnosis of 74 years-old, because of the 30–50 years latency between initial exposure and mesothelioma development. In places where people were only environmentally exposed to carcinogenic fibers, the M:F sex-ratio is about 1:1 and the mean age of diagnosis is 50–605–7. In places where both types of exposure exist, the M:F sex ratio decreases and the proportion of young (<55 years old) cases increases, compared to places with occupational exposure only. Consequently, we used the significant decrease of mesothelioma M:F sex-ratio and the increase of young cases as indicators of possible environmental exposure to carcinogenic fibers. Pinheiro and Jin: “there is no scientific consensus on the use of the sex ratio and the proportion under 55 as indicators of environmental (non-occupational) exposure to asbestos or NOA”. The epidemiology of mesothelioma from mixed environmental and occupational exposures to carcinogenic fibers has never specifically been studied. However, the studies of populations exposed to carcinogenic fibers from their natural environment, without occupational exposure to asbestos, showed a mesothelioma M:F sex-ratio of about 1:1 and a higher proportion of young cases5–7. There are no published studies contradicting or questioning the methodology we used. The first International Conference On Mesothelioma In Populations Exposed To Naturally Occurring Asbestiform Fibers sponsored by the NCI, NIEHS and IASLC, will be held in Honolulu Nov 9–10; methodology will be one of the topics discussed. We would welcome Drs. Pinheiro and Jin. Pinheiro and Jin: “a male to female sex ratio can be elevated just by virtue of a low number of male cases rather than an actual increased absolute number among females”. Although this statement appears incorrect –M:F would be elevated by an increase in males and /or a decrease in females- , we think we understand what they mean. However, a lower mesothelioma incidence/mortality in male and in old age groups simply reflects a lower occupational exposure to asbestos. In the absence of environmental exposure, a low level of occupational exposure leads to a lower mesothelioma incidence in both males and females, and in both old and young age groups, with a M:F sex-ratio still around 4–8:1, and less than 10% of mesothelioma cases in young individuals. If there is environmental exposure in a region where a low level of occupational exposure exists, the environmental exposure causes additional mesothelioma cases in both males and females, leading to a decreased sex ratio and increased proportion of young mesothelioma cases –as observed in Southern Nevada, while the total incidence in male and in old age groups may still be low compared to regions with higher occupational exposure. Pinheiro and Jin question why the study periods are different in the incidence data that we used to compare mesothelioma incidence by state, and the mortality data that we analyzed by gender, age group and county. The answer is simple: the incidence data that we used are public, available by state only, and 2006–2010 was the longest available period of time, while the Center for Disease Control (CDC) mesothelioma mortality data that we obtained to carry out our analysis by county were available for 1999–2010. Additionally, we merely cited the US states which presented the lowest and highest mesothelioma incidence in the US, the lowest and highest sex ratio, and the lowest and highest proportion of young adults. We did not make any statistical comparison using these numbers, which were given as examples; we did not give any p-value comparing Nevada and any of the seven states cited in Table 21. We thank Pinheiro and Jin for highlighting the erroneous total number of mesotheliomas in Table 21. Curiously, they also made a mistake: 31,408 + 133 = 31,541 instead of 31,545 as they stated. Pinheiro and Jin: “For the immediately younger (0–49) and older age groups (0–59) the risk in Nevada is fundamentally the same as in the US”, suggesting that only the 0–54 years-old group would be different. But their own Table 1 shows higher risk in Nevada for the 0–59 years old group, and higher risk in the 0–49 years old group for Southern Nevada, compared with the US. In addition, because of the small numbers, their 95% confidence intervals are large and do not allow for any significant comparison. Consequently, incidence/mortality rates clearly cannot be used to measure environmental exposures. Pinheiro and Jin graciously comment “We praise Baumann for producing a body of literature on mesothelioma and exposure to natural-occurring asbestos (NOA). The recent discovery of NOA in Southern Nevada has raised our interest in the surveillance of mesothelioma in the region”. So it appears we all agree that our findings identifying environmental exposure to asbestos in Southern Nevada are important and require follow up because asbestos causes mesothelioma. Therefore, we are puzzled by the title of their letter, a title that cannot be supported by data, and that in fact contradicts published evidence that exposure to asbestos increases the risk of mesothelioma and that such exposure is occurring in Southern Nevada8–10. Risk is defined as the product of hazard and vulnerability (or exposure)11. Southern Nevadans are indeed being exposed to the hazard of asbestos fibers and therefore are at increased risk for mesothelioma and other asbestos-related diseases1,12. For example, ambient air measured for Phase I of the Boulder City Bypass showed the presence of airborne asbestos fibers10. Moreover, some individuals may be exposed to significantly higher concentrations through recreational activities, such as off-road vehicle recreation, horseback riding, mountain bicycle riding, hiking, and other activities that are popular in the desert areas where asbestos fibers occur1,8–10,14. Environmental epidemiology is about identifying areas in which environmental risk exists and work with local experts and authorities to eliminate or at least mitigate the risk. We hope that we will be allowed to further investigate the areas in Southern Nevada where exposure occurs and where there is an apparent increase of mesothelioma among young adults. We would welcome the opportunity to work together with Nevada epidemiologists and the Nevada health authorities to help identify measures to reduce environmental exposure to asbestos and to other carcinogenic fibers and the consequent risk of mesothelioma, as we have done in other parts of the US and of the world6,14,15.

Comparative health effects in mice of Libby amphibole asbestos and a fibrous amphibole from Arizona

&NA; This project developed from studies demonstrating that Libby Amphibole Asbestos (LAA) causes a non‐typical set of health outcomes not generally reported for asbestos, including systemic autoimmunity and an unusual and devastating lamellar pleural thickening that progresses to severe pulmonary dysfunction and death. Further, mineral fiber mixtures with some similarities to LAA have recently been discovered in southern Nevada and northwestern Arizona, where the material exists in extensive recreational areas and is present in yards, roads, parking lots and school yards. The objective was to compare the health outcomes in mice exposed to either LAA or the fibrous amphiboles collected in Arizona at the Lake Mead National Recreational Area at very low doses to represent environmental exposures. In this study, the fibrous amphibole asbestos sample from Arizona (AzA) is composed of winchite (69%), actinolite (22%), and non‐amphibole minerals (9%) and has a mean aspect ratio of 16.7 ± 0.9. Fibrous amphibole asbestos from Libby (LAA) is composed of winchite (70%), richterite (9%), tremolite (5%), and non‐amphibole minerals (16%) with a mean aspect ratio of 8.4 ± 0.7. C57BL/6 mice were exposed by oropharyngeal aspiration to fiber suspensions at a very low dose of 3 &mgr;g/mouse. After seven months, both LAA‐ and AzA‐exposed mice had indices of chronic immune dysfunction related to a TH17 cytokine profile, with B cell activation, autoantibody production and proteinuria, suggesting kidney involvement. In addition, both exposures led to significant lung and pleural fibrosis. These data suggest that there is risk of pulmonary disease and autoimmune outcomes with environmental exposure to amphibole asbestos, and that this is not limited to Libby, Montana. HighlightsHealth effects of Arizona versus Libby amphibole asbestos were comparable in mice.Both fibers led to immune changes consistent with autoimmune dysfunction.Both fibers caused significant increases in interstitial and pleural fibrosis.Novel sources of asbestos could pose health risks even at low exposure levels.