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PubMed1970

Some derivatives of polyvinylpyridine 1-oxides and their effect on the cytotoxicity of quartz in macrophage cultures.

1. Poly(2-vinylpyridine 1-oxide) counteracts the pathogenic effects normally produced when quartz is injected into or inhaled by animals and the cytotoxic effects when quartz is added to macrophage cultures. The protective action of this polymer has been attributed variously to the formation of an adsorbed layer on the quartz particles, complex formation with monosilicic acid produced by the dissolution of quartz, and strengthening of the membranes or microstructures of the cells.2. Stereoregular forms of poly(2-vinylpyridine 1-oxide), some alkyl derivatives of poly(2-vinylpyridine 1-oxide), poly(3-vinylpyridine 1-oxide) and poly(4-vinylpyridine 1-oxide), a copolymer of 2-vinylpyridine 1-oxide and 2-n-propenylpyridine 1-oxide, some poly(1-methyl-2-vinylpyridinium) quaternary salts, and poly(1-methoxy-2-vinylpyridinium iodide), which had previously been synthesized and studied with respect to their viscosities and interaction with silicic acid, were tested for their ability to counteract the cytotoxic effects of quartz in macrophage cultures. The tests were effected both by pretreating the quartz with polymers, and by pretreating the cells.3. Every polymer proved active in one or other of these conditions, but several were active in one test but inactive in the other. Some polymer quaternary salts, which do not contain the N-oxide group, were found to be active. A remarkable difference in activity was found between the two stereoregular forms of poly(2-vinylpyridine 1-oxide). Pretreatment of the quartz with some of the polymers increased its cytotoxicity significantly.4. Most of the results could be interpreted on the hypothesis that the polymers form an adsorbed layer on the quartz surface, but it is difficult to apply this explanation to two polymers which are inactive when used to pretreat the macrophages but are active when adsorbed on quartz.

Adsorption↗
PubMed1989

Quartz-dust-induced production of reactive oxygen metabolites by human granulocytes.

We studied the effect of quartz on the production of reactive oxygen species by human polymorphonuclear leukocytes (PMN) in vitro by a chemiluminescence (CL) assay. Quartz caused a rapid dose-dependent CL response in the cells. Diamond dust used as an inert control did not stimulate the production of reactive oxygen metabolite by PMN. The quartz-induced activation of oxygen metabolism was also demonstrated by measuring oxygen consumption, nitroblue tetrazolium reduction, and superoxide and hydrogen peroxide production by PMN. Poly-vinyl-pyridine N-oxide (a quartz surface modifying agent) completely abolished the quartz-induced response, but had no effect on opsonized zymosan-induced CL response of PMN. The effect of N-acetylcysteine (a known antioxidant) was inhibitory to the CL formation induced by both quartz and opsonized zymosan. Our results are in agreement with the hypothesis that quartz-induced production of reactive oxygen metabolites is a possible mechanism by which quartz dust produces chronic inflammation and tissue injury of the lung. Agents interfering with the generation of reactive oxygen metabolites may provide a rationale for treatment of mineral-dust-induced pulmonary disease.

Acetylcysteine↗
PubMed2003

Reaction of cysteine and glutathione (GSH) at the freshly fractured quartz surface: a possible role in silica-related diseases?

The reactivity of quartz dusts towards glutathione (GSH) and cysteine (Cys) has been investigated. Cys and GSH react, without being adsorbed (UV-Vis spectroscopy), with commercial quartz dusts in an exposed surface-dependent way, but not with amorphous silica. GSH and Cys have been contacted with freshly ground quartz (agate jar QZg-a and steel jar QZg-s) and quartz heated in air at 500 degrees C (QZs-500) and with a dust generated from a purified quartz (99.9999%) to detect the nature of the reacting surface sites. With both GSH and Cys, the highest reactivity was found on the particles ground in a steel jar, while pure quartz was fully inactive. Detection of the radical GS* (spin trapping) suggests a radical mechanism of oxidation to disulphide onto surface-bound iron traces, more abundant on QZg-s and absent on the pure quartz. Oxidation of thiol groups occurs at surface sites different from those involved in the homolytic rupture of a C-H bond. Both reactions are more pronounced on freshly ground samples, but the C-H rupture takes place at silicon-based surface radicals and Fe2+ centers, while oxidation of GSH and Cys requires Fe3+ centers. As all commercial quartz dusts contain surface iron as an impurity, depletion of extracellular or intracellular GSH may contribute to the oxidative damage caused by particle-derived and cell-derived reactive oxygen species.

Adsorption↗
PubMed2004

Variation of biological responses to different respirable quartz flours determined by a vector model.

BACKGROUND: The hypothesis of widely differing lung damage due to commonly used types of quartz was studied in 16 samples of respirable quartzes (> 99% silica) from sites of the European quartz industry, using an in vitro test, the vector model. Two samples with high and 2 with low biological activities were identified and subsequently examined for their in vivo lung toxicity (inflammation, fibrosis, genotoxicity) and surface characteristics. Alveolar macrophages (AM) are considered the target cells of primary dust effects. The vector model mimics some of the elemental dust cell effects such as cell toxicity, effects on the metabolism and stimulatory effects, e.g., TNF alpha and dust-induced ROS secretion. METHODS: Doses of 15, 30, 60 and 120 microg dust per 10(6) AM were used together with the control dusts (quartz DQ12 and corundum). Testing parameters were LDH, glucuronidase, PMA forced ROS release, TNF alpha and dust induced ROS secretion. The main criterion for the selection of low or high activity samples was the secretion of TNF alpha. RESULTS: (i) Apart from quartz samples with an activity close to that of DQ12, one also finds examples with a very low activity. (ii) In comparison particular parameters are linked with a specific dose response relationship and different dose points for the leveling off of the effects. The levels of TNF alpha represent a conspicuously broad response pattern; some samples induce secretion at the lowest dose and others are not active even at the highest dose investigated at already apparent toxicity. (iii) Regarding various parameters the dust samples led to distinct dose response profiles considered as vectors. The current study indicates that within the particle type "quartz fine dust" varying harmful doses and different elements of damage must be present. (iv) The lung damage of the subchronic animal assay coincides with in vitro tests thus confirming the concept of the vector model. CONCLUSION: Threshold effects in the range of 15 - > or = 120 microg can be demonstrated for the discriminant vector TNF alpha, i.e. over 4 steps of dose doubling. These studies show very toxic quartzes but also quartzes of low biological activity comparable to corundum.

Animals↗
PubMed1994

A comparative study of particle size dependency of IR and XRD methods for quartz analysis.

Quartz (SiO2) is considered a probable carcinogen. In order to enforce health and safety standards, techniques that can accurately determine the quartz content of materials are necessary. Currently, two techniques dominate quartz analysis--the infrared (IR) spectrophotometry method and the X-ray diffraction (XRD) method. Unfortunately, there are problems associated with these techniques, such as sample preparation and particle size effect. This study focuses on particle size effect on quartz determination by both IR and XRD. Seven size groups of pure quartz samples, with mean diameters from 1.5 to 20 microns, were used. A set of samples with different quartz masses was prepared for each size group and subjected to both IR and XRD analysis. Two sets of calibration curves, one each from IR and XRD, were obtained. It was found that both IR and XRD methods are size-dependent but in an opposite way. As particle size increases, IR peak height decreases and XRD peak height increases for the same quartz content (mass). Since both methods are particle size-dependent, it is important that the standard quartz sample and samples of interest have similar particle size distributions. Specifically, when coal dust samples are ashed before analysis, the after-ashing particle size distribution should be used. Particle size distribution will change after ashing and it is the after-ashed particles that directly affect the IR and XRD analysis.

Calibration↗
PubMed2005

Comparison of quartz standards for X-ray diffraction analysis: HSE A9950 (Sikron F600) and NIST SRM 1878.

A further comparison of the Health and Safety Executive (HSE) standard quartz, A9950 (Sikron F600), and the National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) 1878, standard respirable alpha-quartz, has been carried out for the four principal diffraction peaks. In the earlier comparison by Jeyaratnam and Nagar (1993, Ann Occup Hyg; 37: 167-79), the standards were both treated in ways which might change the particle size distribution and therefore the proportion of crystalline quartz. The two standards have now been compared in the most direct way possible with the minimum of sample treatment. There are no significant differences in the diffraction peak positions for the two standards. Nor do the peak area intensities differ significantly. The peak height intensities are consistently and significantly higher for Sikron F600 than for NIST SRM 1878. The particle size broadening of the diffraction peaks is evidently greater for NIST 1878, whose mass median diameter is quoted as 1.6 microm against 2.6 microm for Sikron F600. Taking the certified reference value for SRM 1878 as 95.5 +/- 1.1% crystalline quartz, the HSE standard A9950 (Sikron F600) contains 96.3 +/- 1.4% crystalline quartz based on a comparison of peak area intensities. On the same basis but using peak height intensities, the nominal crystalline quartz content of A9950 (Sikron F600) is 101.2 +/- 1.8%. Results obtained by comparison of quartz standards may not be generally applicable because of the effect of sample treatment on particle size and crystalline quartz content.

Air Pollutants, Occupational↗
PubMed1993

Effect of quartz and alumina dust on generation of superoxide radicals and hydrogen peroxide by alveolar macrophages, granulocytes, and monocytes.

Phagocytosis of quartz particles by rabbit alveolar macrophages and monocytes and human granulocytes and monocytes was accompanied by stimulation of substrate free reduction of nitroblue tetrazolium to formazan. This reflects activation of an oxygen dependent bactericidal system of phagocytes and total (exogenic and endogenic) generation of active oxygen species. Low fibrogenic and cytotoxic alumina dust tended to increase formazan production by comparison with quartz dust. During phagocytosis of quartz dust by alveolar macrophages and monocytes there was no exogenic generation of superoxide radicals and hydrogen peroxide by these cells. By contrast, incubation of human granulocytes with quartz dust caused a significant increase in exogenic generation of superoxide radicals and hydrogen peroxide. Under such conditions, low fibrogenic alumina dust had no effect on hydrogen peroxide generation and substantially decreased the level of superoxide radical generation by human granulocytes. During incubation of rabbit granulocytes with quartz dust, an increase in the level of superoxide radical generation was also detected. It is considered that the differences between alveolar macrophages and granulocytes in their response to quartz dust are important from a physiological point of view. Alveolar macrophages are permanently present in pulmonary alveolae in large quantities; therefore their uncontrolled generation of superoxide radicals and hydrogen peroxide might immediately cause damage to pulmonary parenchyma. At the same time, destruction products from alveolar macrophages that died during phagocytosis of quartz particles contain a factor attracting granulocytes. Presence of a significant number of granulocytes in bronchopulmonary lavage fluid in cases of silicosis indicates development of a pathological process. This agrees well with the data obtained on exogenic generation of superoxide radicals and hydrogen peroxide by granulocytes, and on stimulation of this process due to phagocytosis of the quartz dust.

Aluminum Oxide↗
PubMed1998

Risks of silicosis in coalworkers exposed to unusual concentrations of respirable quartz.

OBJECTIVES: To describe the radiographic changes in coalworkers exposed to unusual concentrations of respirable quartz during the 1970s, and to relate these to exposure measurements. METHODS: Men who had worked at one Scottish colliery during the 1970s were invited to a health survey. Chest radiographs were taken from 547 subjects. Classifications of these films under the International Labour Organisation (ILO) 1980 scheme were related, by logistic regression, to existing data on individual men's exposures to respirable dust and quartz. RESULTS: Taking the median of the three readers' results on profusion of small opacities, 203 men (38%) showed progression of at least one profusion category on the 12 point scale, from the various 1970s surveys to the follow up in 1990-1. A total of 158 men (29%) had a profusion of at least 1/0, and 47 (8.6%) of at least 2/1 at the follow up survey. Large opacities were recorded as present by at least two readers for 14 (2.6%) of the men. Profusion of small opacities was strongly related to exposures experienced in the 1970s, and more strongly for quartz than for the non-quartz fraction of the dust. Estimates of risk are presented over the range of quartz exposures experienced. CONCLUSIONS: The quartz exposures experienced by some men at this colliery have caused considerable progression of radiographic abnormalities since exposure ended. The data accumulated offer opportunities for further more detailed analyses to inform debate on occupational limits for quartz exposures, both in collieries and in other industries where there is exposure to quartz in mixed dust.

Adult↗
PubMed2003

Quantitative relations between exposure to respirable quartz and risk of silicosis.

AIMS: To reanalyse exposure-response data from a Scottish colliery to gain a more detailed knowledge of the relations between exposure to quartz and risks of silicosis in coal miners, and hence inform the debate on an appropriate occupational standard for respirable quartz. METHODS: Detailed data on working times at different quartz concentrations were combined to produce exposure profiles for miners who had provided a full chest radiograph at a follow up survey. Logistic regression methods were used to model profusion of radiographic abnormalities category 2/1+, and a general exposure index was used to compare different quartz exposure measures in these models. RESULTS: Results in 371 men aged 50-74 indicated that cumulative quartz exposure at higher concentrations resulted in proportionally greater risks of abnormalities. One g x h x m(-3) of cumulative exposure at quartz concentrations greater than 2 mg x m(-3) was estimated to have equivalent risks to 3 g x h x m(-3) at lower concentrations. The timing of exposure relative to follow up appeared less important, although the study had limited power to compare different lag periods between exposure and effect. CONCLUSIONS: Quantification of the risks of silicosis should take account of variations in quartz exposure intensity, particularly for exposure to concentrations of greater than 1 or 2 mg.m(-3), even if exposure is for relatively short periods. The risks of silicosis over a working lifetime can rise dramatically with even brief exposure to such high quartz concentrations. Risk estimates are given, to inform choice of control limits.

Aged↗
PubMed2005

The crucial role of particle surface reactivity in respirable quartz-induced reactive oxygen/nitrogen species formation and APE/Ref-1 induction in rat lung.

Persistent inflammation and associated excessive oxidative stress have been crucially implicated in quartz-induced pulmonary diseases, including fibrosis and cancer. We have investigated the significance of the particle surface reactivity of respirable quartz dust in relation to the in vivo generation of reactive oxygen and nitrogen species (ROS/RNS) and the associated induction of oxidative stress responses in the lung. Therefore, rats were intratracheally instilled with 2 mg quartz (DQ12) or quartz whose surface was modified by either polyvinylpyridine-N-oxide (PVNO) or aluminium lactate (AL). Seven days after instillation, the bronchoalveolar lavage fluid (BALF) was analysed for markers of inflammation (total/differential cell counts), levels of pulmonary oxidants (H2O2, nitrite), antioxidant status (trolox equivalent antioxidant capacity), as well as for markers of lung tissue damage, e.g. total protein, lactate dehydrogenase and alkaline phosphatase. Lung homogenates as well as sections were investigated regarding the induction of the oxidative DNA-lesion/oxidative stress marker 8-hydroxy-2'-deoxyguanosine (8-OHdG) using HPLC/ECD analysis and immunohistochemistry, respectively. Homogenates and sections were also investigated for the expression of the bifunctional apurinic/apyrimidinic endonuclease/redox factor-1 (APE/Ref-1) by Western blotting and immunohistochemistry. Significantly increased levels of H2O2 and nitrite were observed in rats treated with non-coated quartz, when compared to rats that were treated with either saline or the surface-modified quartz preparations. In the BALF, there was a strong correlation between the number of macrophages and ROS, as well as total cells and RNS. Although enhanced oxidant generation in non-coated DQ12-treated rats was paralleled with an increased total antioxidant capacity in the BALF, these animals also showed significantly enhanced lung tissue damage. Remarkably however, elevated ROS levels were not associated with an increase in 8-OHdG, whereas the lung tissue expression of APE/Ref-1 protein was clearly up-regulated. The present data provide further in vivo evidence for the crucial role of particle surface properties in quartz dust-induced ROS/RNS generation by recruited inflammatory phagocytes. Our results also demonstrate that quartz dust can fail to show steady-state enhanced oxidative DNA damage in the respiratory tract, in conditions were it elicits a marked and persistent inflammation with associated generation of ROS/RNS, and indicate that this may relate to compensatory induction of APE/Ref-1 mediated base excision repair.

Animals↗
PubMed1995

Particle activity and in vivo pulmonary response to freshly milled and aged alpha-quartz.

This study examined the possibility of freshly fractured alpha-quartz being more toxic and inflammatory in vivo than aged quartz of the same composition and particle size. Fresh quartz was generated by a jet mill, and used immediately, while aged dust was stored for two months before use. Both the production of hydrogen peroxide and hydroxyl radicals and the analysis of surface radicals verified the enhanced surface activity of fresh quartz. Male Fischer 344 rats were exposed to fresh or aged alpha-quartz by inhalation (20 mg center dot m-3, 5 h per day, 5 d per week, for 2 weeks) and their pulmonary responses were determined 1--3 d postexposure. Exposure to aged quartz resulted in an increase in cytotoxic and inflammatory parameters. In comparison, the inhalation of freshly cleaved quartz resulted in dramatically greater increases in all of the pulmonary responses. This finding suggests that exposure to freshly machined quartz may result in a greater risk of pulmonary disease.

Administration, Inhalation↗
PubMed2002

Comparison between ST-cut quartz 25 degrees and -60 degrees NSPUDT propagation directions.

This paper discusses directivity and other propagation properties of natural single phase unidirectional transducer (NSPUDT) propagation directions on ST-cut quartz. The work focuses on the comparison of surface acoustic wave (SAW) directivity and propagation properties between the ST-cut quartz -60 degrees, Euler angles: (0 degrees, 132.75 degrees, -60 degrees), and the ST-cut quartz 25 degrees, Euler angles: (0 degrees, 132.75 degrees, 25 degrees), NSPUDT propagation directions, including predicted and measured directivity responses for both propagation directions. The well-known SAW 25 degrees propagation direction is used for low loss, high performance SAW filter designs for consumer products and communications applications. The ST-cut quartz -60 degrees propagation direction has been predicted to have a reflection coefficient 2.5 times larger than ST-cut quartz 25 degrees. In addition the ST-cut quartz -60 degrees satisfied the NSPUDT 90 degrees reflection coefficient phase condition much more closely, resulting in an improved directivity response. For the delay line structures used in the experiments, the measured directivity is 10.1 dB for the -60 degrees propagation direction. For the same structures, the measured directivity along the 25 degrees propagation direction is about 5.0 dB. The experimental results given in this paper verify that indeed ST-cut quartz -60 degrees has a higher directivity than ST-cut quartz 25 degrees, confirming the theoretical predictions. In addition, this work compares other propagation properties for both directions, namely, phase velocities, electromechanical couplings, temperature coefficients of delay, power flow angles, and metallic strip reflection coefficient amplitudes and phases.

Journal Article↗
PubMed2001

Effects of phospholipid surfactant on apoptosis induction by respirable quartz and kaolin in NR8383 rat pulmonary macrophages.

Apoptosis was measured in rat alveolar macrophage NR8383 cells challenged in vitro with respirable quartz or kaolin dust and with the dusts pretreated with dipalmitoyl phosphatidylcholine (DPPC) to model conditioning of respired dusts by interaction with a primary phospholipid component of pulmonary surfactant. Quartz dust is known to induce apoptosis in vitro and in vivo. For this study, quartz and kaolin were compared as dusts of similar cytotoxicity in some in vitro assays but of differing pathogenic potential: quartz can cause significant pulmonary fibrosis while kaolin generally does not. NR8383 cells exposed to native quartz at concentrations from 50 to 400 microg/ml for 6 h showed a dose-dependent increase in apoptosis measured by the TdT-mediated dUTP-fluorescein nick end labeling (TUNEL), cell death ELISA, and DNA ladder formation assays, while native kaolin induced significant response only at the higher concentrations and only in the TUNEL and ELISA assays. For cell challenge from 6 h to 5 days at 100 microg/ml of dust, quartz was active at all times while kaolin was active only at 5 days. DPPC pre-treatment suppressed quartz activity until 3 days and kaolin activity through 5 days. Cellular release of lactate dehydrogenase, measured in parallel experiments to compare dust apoptotic and necrotic activities, indicated that components of serum as well as surfactant may affect kaolin in vitro expression of those activities.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1993

Presence of serum modulates expression of complement receptor type 1 (CR1) on human granulocytes after quartz exposure.

We have investigated the interaction between granulocytes and quartz with respect to the expression of complement receptor type 1 (CR1) and the presence of normal human serum (NHS). Quartz down-regulates selectively CR1 on activated granulocytes. This down-regulation is abolished in the presence of both NHS and heat-inactivated NHS (NHS56) but not human albumin. When quartz was preincubated with NHS (quartz-NHS) before exposure to activated granulocytes, a down-regulating effect was observed in contrast to preincubation with NHS56, which did not induce a down-regulation. Preincubation with cytochalasin B reduced the down-regulation of quartz-NHS, indicating a cytoskeleton-dependent internalization of the receptor. The serine protease inhibitor PMSF partly reduced this down-regulation. Our results indicate that the presence of NHS in the alveolar space influences the interaction between quartz and recruited granulocytes with respect to CR1 expression. Since CR1 is an important opsonin receptor and soluble CR1 can modulate the inflammatory response, this may be of importance in the inflammation and fibrosing process induced by quartz in the alveolar space and lung interstitium.

Blood Physiological Phenomena↗
PubMed2006

Genotoxic potential of respirable bentonite particles with different quartz contents and chemical modifications in human lung fibroblasts.

Crystalline silica has been classified as a human carcinogen, but there is still considerable controversy regarding its fibrogenic and carcinogenic potential. In the present study, we investigated the genotoxic potential of bentonite particles (diameter < 10 microm) with an a-quartz content of up to 6% and different chemical modifications (alkaline, acidic, organic). Human lung fibroblasts (IMR90) were incubated for 36 h, 48 h, or 72 h with bentonite particles in concentrations ranging from 1 to 15 microg/cm2. Genotoxicity was assessed using the micronucleus (MN) assay and kinetochore analysis. The generation of reactive oxygen species (ROS) caused by bentonite particles via Fenton-like mechanisms was measured acellularly using electron spin resonance (ESR) technique and intracellularly by applying an iron chelator. Our results show that bentonite-induced genotoxic effects in human lung fibroblasts are weak. The formation of micronuclei was only slightly increased after exposure of IMR90 cells to an acidic sample of bentonite dust with a quartz content of 4-5% for 36 h (15 microg/cm2), 48 h (5 microg/cm2), and 72 h (1 microg/cm2), to an alkaline sample with a quartz content of 5% for 48 h and 72 h (15 microg/cm2), and to an acidic bentonite sample with 1% quartz for 72 h (1 microg/cm2). Native (untreated) and organic activated bentonite particles did not show genotoxic effects in most of the experiments. Also, bentonite particles with a quartz content < 1% were negative in the micronucleus assay. Generation of ROS measured by ESR was dependent on the content of transition metals in the sample but not on the quartz content or the chemical modification. Reduction of MN after addition of the iron chelator 2,2'-dipyridyl showed that ROS formation also occurs intracellularly. Altogether, we conclude that the genotoxic potential of bentonite particles is generally low but can be altered by the content of quartz and available transition metals.

Bentonite↗
PubMed2003

Epidemiological adaptation of quartz exposure modeling in Swedish aluminum foundries: nested case-control study on lung cancer.

In a recent cohort study in aluminum foundries and remelting plants an unexpectedly high risk of lung cancer was found in workers in sand foundries. On the basis of present and historical measurement data, we developed a statistical model for exposure to total dust and crystalline quartz for different jobs and time periods. Cumulative dose estimates of total dust and crystalline quartz were calculated and used in a nested case-control study in the cohort. From the cohort of foundry workers (n = 5016), 46 cases of lung cancer were identified. The final analysis was performed on 31 cases and 233 controls with one year or more of employment. Historical measurement data from the 1960s and onward were collected, totaling 203 total dust and 103 crystalline quartz exposure observations. Regression models, using the determinants of job title, time period, type of foundry, and size of production, were developed for assessing historical total dust and crystalline quartz air concentrations. These estimates were used to calculate individual cumulative exposure in the case-control study. In the multiple linear regression analysis, the determinants explained much of the variations in dust level (r(2) = 0.58). The explained variation in crystalline quartz was much lower (r(2) = 0.13). The regression coefficients for the type of foundry, time period, and size of production were statistically significant for total dust. On the basis of the regression analysis, the final models were used to calculate individual cumulative exposures. The calculated cumulative dust and quartz exposures averaged 33 mg/m(3) * year and 0.42 mg/m(3) * year, respectively. The odds ratios (ORs) were not significant, but showed dose-response trends for both dust and crystalline quartz.

Aluminum↗
PubMedDate not supplied

Exposures to quartz, diesel, dust, and welding fumes during heavy and highway construction.

Personal samples for exposure to dust, diesel exhaust, quartz, and welding fume were collected on heavy and highway construction workers. The respirable, thoracic, and inhalable fractions of dust and quartz exposures were estimated from 260 personal impactor samples. Respirable quartz exposures exceeded the National Institute for Occupational Safety and Health (NIOSH) recommended exposure limit (REL) in 7-31% of cases for the trades sampled. More than 50% of the samples in the installation of drop ceilings and wall tiles and concrete finish operations exceeded the NIOSH REL for quartz. Thoracic exposures to quartz and dust exceeded respirable exposures by a factor of 4.5 and 2.8, respectively. Inhalable exposures to quartz and dust exceeded respirable exposures by a factor of 25.6 and 9.3, respectively. These findings are important due to the identification of quartz as a carcinogen by the National Toxicology Program and the International Agency for Research on Cancer. Fourteen percent of the personal samples for EC (n = 261), collected as a marker for diesel exhaust, exceeded the American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit value (TLV) for diesel exhaust. Seventeen of the 22 (77%) samples taken during a partially enclosed welding operation reached or exceeded the ACGIH TLV of 5 mg/m3 for welding fume.

Boston↗
PubMed2001

Can enantiomorphic crystals like quartz play a role in the origin of homochirality on earth?

This communication reviews the possible actions of enantiomorphic crystals on the surface of Earth as sources of homochirality of organic compounds. The discovery of asymmetric adsorption and asymmetric catalysis involving optically active quartz crystals has led some authors to conclude that this source of asymmetry played an important role as a source of homochirality in nature, a concept that later proved erroneous. Moreover, data regarding the preponderance in nature of l-quartz crystals have been used to confirm calculations of the parity violation energy difference (PVED) for l-quartz and, hence, to explain the prevalence of L-amino acids and D-sugars in living matter. As discussed here, quartz and other enantiomorphs such as sodium chlorate can produce chiral intermediates active in autocatalytical processes. Our most recent compilation of the literature, however, reveals that the distribution of d- and l-quartz crystals at the surface of the Earth when all possible locations are included is quite random. Although quartz can serve as an effective asymmetric inductor in autocatalytic processes, it cannot be the source of homochirality of living matter because of the random occurrence of the two types of enantiomorphs. The calculations of PVED values for quartz therefore lack a sound physical basis.

Crystallization↗