Discerning Erionite from Other Zeolite Minerals During Analysis

Abstract

Erionite, a naturally occurring fibrous mineral that belongs to the zeolite group has been designated by the International Agency for Research on Cancer (IARC) as a Group 1 Carcinogen on the basis of mesothelioma, a disease also resulting from the inhalation of asbestos fibers. Significant outcrops of fibrous erionite have been reported in California, North Dakota, Nevada, Oregon, and other states. For geologists and industrial hygienists dealing with mining, construction, or various aspects of community protection, it is vital to understand the basics of detecting and handling erionite, since it is similar to asbestos and can cause similar disease. There are many fibrous zeolites, and discerning erionite from these other minerals requires modifications to current asbestos analysis methods. Without these modifications, identification and quantification are questionable and could increase the likelihood of both false negatives and false positives. There is currently no published method specific to erionite analysis; without guidance standards, each laboratory has approached erionite analysis independently. With a few small but significant changes to asbestos analysis methodologies, we developed a reproducible analytical procedure for rapid identification of erionite fibers in air, bulk, and soil samples by transmission electron microscopy (TEM). Using specialized preparation techniques, energy dispersive Spectrometry (EDS) calibrations, and a liquid nitrogen cryo-holder (cold stage), we were able to overcome the difficulties associated with erionite analysis. By incorporating these changes, commercial analytical laboratories can contribute reliable data to air-exposure studies and characterization guidelines, which may help in determining regulations and further understanding the health risks of erionite.

Reanalysis of historic elemental speciation filters to investigate the presence of fibrous mineral particles using microscopy techniques

“…In addition, larger, coarse mode particles and fibres can block and intercept X-rays producing shadow areas (Moreno et al, 2003). Finally, the high voltage electron beam can penetrate through the particle resulting in partial analysis of underlying particles or filter substrate, whilst potentially damaging the investigated fibre (Ray, 2020). Figure 6 shows an example of fibrous materials on a filter collected in Henderson.…”

Global geological occurrence and character of the carcinogenic zeolite mineral, erionite: A review

“…Pleural MM (cancer of the tissue that lines the lungs) is the most common cancer of the three and is caused by the inhalation of fibrous material such as asbestos or erionite (Bariş et al, 1979;Robinson et al, 2005). In addition, there are also noncancerous health issues known to be caused by inhaling erionite, such as pleural fibrosis and promoting the production of autoantibodies (Fach et al, 2003;Zebedeo et al, 2014;Ray, 2020).…”

“…Therefore, delineating the chemistry as well as the surface characterization of the involved particle is important (Giordani et al, 2022). However, since erionite was first discovered, a multitude of studies have been conducted globally that involve classifying erionite, yet the precise identification of erionite has been somewhat hampered by its physico-chemical similarities to other fibrous zeolites such as offretite (Passaglia et al, 1998;Ray, 2020). Erionite has not been mined for commercial use since the late 1980s (Ray, 2020), and so many commercial laboratories focusing on asbestos in bulk building…”

“…For example, rock and soil material must be reduced to a fine powder for analysis by optical microscopy (OM), and based on the preparation of erionite samples from Pine Valley, Nevada, Ray (2020) reported that erionite is fragile and extremely susceptible to over grinding. Indeed, samples were milled to two nominal sizes, 250 μm and 75 μm, and once overmilled, bundles and fibers were destroyed and broken into nonfibrous particles (Ray, 2020). Thus, such fragments would no longer be countable by an analyst during a microscopic examination, which could misrepresent the potential toxicity of in situ erionite material.…”

“…Energy Dispersive Spectroscopy (EDS) is a technique used in conjunction with electron microscopy (SEM or TEM). When the beam of electrons hits a sample, it generates X-rays, which are characteristic of each element (Ray, 2020). The EDS detects the X-ray energy and measures the rate at which the X-ray is emitted, producing an EDS spectrum of X-ray energy vs. counts.…”