A case of oral foreign-body granuloma due to diatoms.

Diatoms are photosynthetic algae with a siliceous exoskeleton. Diatoms are utilized by a wide array of industries for applications such as filtration and pest control. Unsubstantiated claims have also propelled their societal reach to trendy oral and topical uses. This case highlights a rare case of an oral granuloma secondary to diatoms. An 80-year-old woman presented with a mobile, firm, asymptomatic submucosal mass on her lower left mandibular vestibular mucosa. Histopathology showed a non-caseating granulomatous reaction to diatoms. Her only verified contact with a diatomaceous earth product was a dental impression using alginate after upper front teeth trauma 5 months before. Although there have been several cases of allergic contact dermatitis attributed to diatoms, there are no reported cases of diatom-induced granuloma formation found in the literature. There are, however, ample data on granulomas initiated by silica. Given the silica-based composition of diatoms, and the broad use of diatoms in industry and alternative medicine, it is unclear why diatom-induced granulomas are not more widely described. This report may alert clinicians to the existence of diatom granulomas and incline them to tailor their history to cover questions about possible exposure when evaluating patients presenting with a localized oral lesion.

It's elemental! Siliceous diatom frustules producing sarcoid-like granulomas in the subcutis.

Silica granulomas have been described on the skin and are rare; however, this is the first report of a sarcoid-like granulomatous reaction because of siliceous diatom frustules in the subcutis, making this an unprecedented case. A 41-year-old female presented with a subcutaneous nodule on the right forearm clinically suggestive of cyst, foreign body, or lipoma. Excisional biopsy revealed subcutis with a sarcoid-like granulomatous reaction in a background of fibrosis, containing abundant semitransparent, exquisitely geometric particles, mildly refringent under polarized light, highlighted by phase contrast microscopy; special stains were negative for microorganisms. Definitive characterization of the peculiar fragments was accomplished by confocal laser microscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy, revealing them as diatom frustules made of silicon dioxide (SiO2 ) or silica. Diatoms are unicellular algae, their skeletons (frustules) made of silica have collected on the bottom of rivers, lakes, and oceans for thousands or millions of years and form what we know as diatomite or diatomaceous earth, which is widely used in different industries and easily available in the market. The mechanism whereby diatom frustules gained access to the patient's subcutis is enigmatic.

Severe silicosis due to diatomaceous earth in dental alginate: a necropsy study.

BACKGROUND: Severe silicosis from occupational exposure to calcined diatomaceous earth has been observed in the past, due to the high-temperature transformation of amorphous silica in crystalline phases, mainly cristobalite. In dental alginate production and use a silica exposure may be underestimated. OBJECTIVES: To describe the clinical picture, the scenario and pattern of occupational exposure to silica and the corresponding necroscopic findings of a case of silicosis in a worker engaged in the production of alginates for dental use. METHODS: A commercial sample of calcinated diatomaceous earth and necroscopic lung samples were analysed by scanning electron microscopy (SEM-EDS) and X-ray diffraction (XRD) for the quali-quantitative determination of crystalline silica. Material safety data sheets (MSDSs) of diatomaceous earth produced in 2002 and 2018 were examined to assess the information content on silicosis risk. Clinical findings and post-mortem examinations of the worker are evaluated. RESULTS: A cristobalite concentration of 36% (wt/wt) was determined in the diatomaceous earth sample and a large amount of diatom fragments were observed in lung samples. The DRX spectra indicated the presence of cristobalite either in the bulk sample or in the lung tissues. The MSDS dated 2002 reported the presence of SLC up to 63% with cristobalite concentrations minor of 60%, and the resulting risk of silicosis, while the MSDS dated 2018 and referred to a commercial product currently on the market indicated a concentration of cristobalite minor of 1% and no risk of silicosis. The worker was suffering from a severe silicosis, histologically confirmed by necropsy. CONCLUSION: The present case-study revealed that the risk of silicosis from calcined diatomaceous earths used to produce dental alginates has been ignored. The lack of engineering controls and personal protection measures led to a high cristobalite lung burden, consistent with the development of a severe silicosis that were a contributing factor of death. A MSDS of a commercial product currently on the market does not report this serious hazard.

Extended follow-up of lung cancer and non-malignant respiratory disease mortality among California diatomaceous earth workers.

OBJECTIVES: Millions of workers worldwide are employed in occupations involving potentiality hazardous exposure to crystalline silica. The diatomaceous earth industry can have particularly high exposures, but there is a lower likelihood of simultaneously occurring confounding exposures. We extended follow-up for diatomaceous earth industry workers previously studied for mortality. METHODS: The cohort included 2342 white men who were employed for at least 1 year at a diatomaceous earth plant in Lompoc, California beginning in 1942. Workers' vital status was updated using the National Death Index through 2011, an extension of 19 years from earlier studies. Detailed work history and quantitative air monitoring measurements estimated exposure intensity. Cox proportional hazards modelling estimated HRs and 95% CIs. SMRs were calculated. RESULTS: Elevated mortality was observed by quartile of cumulative crystalline silica exposure for lung cancer (HR=2.03, 95% CI 1.07 to 3.85, highest quartile, unlagged) and non-malignant respiratory disease (NMRD) (HR=3.59, 95% CI 1.94 to 6.67, highest quartile, unlagged), although trends were not statistically significant. Associations were attenuated when adjusted for smoking and asbestos exposure. Mortality from NMRD was significantly increased over the entire follow-up compared to the general population (SMR=1.37, 95% CI 1.17 to 1.60). An increase for lung cancer was confined to the earlier follow-up (SMR=1.29, 95% CI 1.01 to 1.61). CONCLUSIONS: The risk of lung cancer and NMRD mortality remained elevated, although generally non-significant, and exposure-response trends with cumulative crystalline silica persisted on extended follow-up of this cohort. The findings support a generally consistently observed aetiological relation between crystalline silica and lung cancer.

Rare pneumoconiosis induced by long-term amorphous silica exposure: the histological characteristics and expression of cyclooxygenase-2 as an antifibrogenic mediator in macrophages.

Pneumoconiosis induced by non-crystalline silica is considered rare, although silicosis resulting from contact with crystalline silica is a well-known hazard associated with progressive pulmonary fibrosis. Here we describe a patient with pneumoconiosis induced by diatomaceous earth composed of amorphous silica detected by two-dimensional imaging of chemical elements. The histology revealed that the disease was characterized by a granulomatous reaction in the lung. A large number of macrophages laden with yellow and black pigments accumulated in alveolar spaces and were incorporated into the interstitial sites. Bronchiolar walls were destroyed by palisade macrophages, suggesting airflow obstruction. Packed macrophages adhering to and covering the denuded interstitium indicated that macrophages might be incorporated into pulmonary interstitium in this fashion. Immunohistochemistry showed that cyclooxygenase-2, an antifibrogenic mediator, was intensely expressed in the macrophages compared with macrophages in control lungs. No birefringent material was found in the tissues. When two-dimensional analysis of chemical elements was performed using an electron probe microanalyzer with a wavelength-dispersive spectrometer, the resultant fine mapping of silicon and oxygen on the tissue indicated that the pigments phagocytosed by macrophages corresponded to amorphous silica. In conclusion, two-dimensional analysis of elements is very useful for pathologists in correlating the presence of chemical elements with histological changes.

Radiographic and spirometric findings in diatomaceous earth workers.

Diatomaceous earth is a noncrystalline form of silica; in processing, calcining leads to formation of cristobalite, a form of crystalline silica. Four hundred ninety-two currently employed diatomaceous earth workers in a large mine and processing facility had chest radiographs performed and interpreted by the International Labour Office (ILO) system. Two hundred sixty-seven subjects underwent spirometry testing. Exposure indices for total dust (largely diatomaceous earth) and cristobalite were reconstructed for each individual based upon personnel records. Analysis demonstrated the following prevalences of radiographic findings: 5% had ILO scores > or = 1/0, and 25% had scores of 0/1 or higher. Regression analyses showed that there was a relationship between both total cristobalite exposure and total dust (largely diatomaceous earth) exposure and the ILO score. Radiographic patterns are not typical of those of classic silicosis. Linear regression analyses for forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), and FEV1/FVC ratio did not demonstrate a relationship between cumulative exposure and lung function. Such analyses were performed using all subjects and stratified by smoking status. There were differences in spirometric data according to radiographic ILO category, but the results were inconsistent and did not permit determining if physiologic changes are associated with radiographic change or if this is due to confounding. Overall, the study suggests that diatomaceous earth pneumoconiosis (radiographically defined) is an entity distinct from silicosis. Recent exposure levels may produce radiographic abnormalities but do not lead to demonstrable physiologic effect. The prevalence of the disorder has diminished markedly in response to modern dust control measures. Ongoing medical surveillance is recommended in workers with potential exposure to significant quantity of material.

Lung cancer incidence among an Icelandic cohort exposed to diatomaceous earth and cristobalite.

OBJECTIVES: The objective of this study was to determine the cancer incidence of a cohort exposed to diatomaceous earth and cristobalite with special focus on lung cancer. METHODS: The cohort was from a diatomaceous plant in northern Iceland and comprised 919 men and 423 women. Diatomite, when heated, is transformed from amorphous to crystalline silica with a high cristobalite content and traces of quartz. With the use of the identification number of all persons, a link was made with the Cancer Registry. The expected number of malignancies was calculated on the basis of person-years of observation for 5-year age categories during the respective calendar period of the study multiplied by the specific incidence of cancer site for men and women in Iceland. RESULTS: There was no increased overall incidence of cancer in the study population; 5 cases of lung cancer were observed versus 4.4 expected, the standardized incidence ratio (SIR) was 1.14 [95% confidence interval (95% CI) 0.37-2.65]. When the men in the cohort were divided according to their length of employment, there was an excess of lung cancer (3 observed versus 1.28 expected, SIR 2.34, 95% CI 0.48-6.85), nonmelanoma skin cancer (2 observed versus 0.19 expected, SIR 10.53, 95% CI 1.27-38.02), and brain cancer (3 observed versus 0.30 expected, SIR 10.00, 95% CI 2.06-29.23) for those who had worked 5 years or longer. A special investigation of smoking habits among the cohort revealed a smoking pattern similar to that of the general population. CONCLUSION: The results concerning lung cancer showed an excess risk for workers exposed to diatomaceous earth and cristobalite; the result was not, however, statistically significant. There was a trend towards a higher incidence of lung cancer with longer exposure to crystalline silica, and, in agreement with the results of a previous study from this industry, the findings indicate a causal relation.

[Amorphous silica. Types, health effects of exposure, NDS]. / Krzemionki bezpostaciowe. Rodzaje, skutki zdrowotne ekspozycji, NDS.

Maximum allowable concentration (MAC) values for amorphous silica dust have not been identified in the Polish legal regulations up-to-date. In this work the authors review values of allowable (recommended) amorphous silica dust concentrations in other countries. Data on other types of amorphous silica (natural and synthetic) used in industry as well as data on health effects of exposure to these types of dust are presented. The work encompasses 42 entries in the references and one Table which includes the following proposed MAC values: Non-calcinate diatomaceous earth (diatomite) and synthetic silica: Total dust--10 mg/m3 Respirable dust--2 mg/m3 Calcinate diatomaceous earth (diatomite) and fused silica (vitreous silica): Total dust--2 mg/m3 Respirable dust--1 mg/m3.

Silica-associated limited systemic sclerosis after occupational exposure to calcined diatomaceous earth.

Silica-associated systemic sclerosis can occur in persons using calcined diatomaceous earth for filtration purpose. A limited systemic sclerosis was diagnosed in a 52-year-old male winegrower who had a combination of Raynaud's phenomenon, oesophageal dysfunction, sclerodactyly and telangectasia. The anti-centromere antibodies titre was 1/5000. The patient was frequently exposed to high atmospheric concentrations of calcined diatomaceous earth when performing the filtration of wines. Calcined diatomaceous earth is almost pure crystalline silica under the cristobalite form. The diagnosis of silica-associated limited systemic sclerosis after exposure to calcined diatomaceous earth was made. The patient's disease met the medical, administrative and occupational criteria given in the occupational diseases list 22 bis of the agriculture Social Security scheme and thence was presumed to be occupational in origin, without need to be proved. The diagnosis of occupational disease had been recognized by the compensation system of the agricultural health insurance.

Silicosis in diatomaceous earth factory workers in Sweden.

Kieselguhr is a greyish-white powder which is made by heating lake ooze containing diatom skeletons to a temperature of about 1000 degrees C. It contains quartz, cristobalite and tridymite. Working with kieselguhr can induce silicosis. In Sweden six cases of silicosis caused by exposure to kieselguhr have been reported to the Worker's Protection Board. The time of exposure was relatively short. New cases have not appeared in the last 20 years. It seems, nevertheless, important to document this unusual form of silicosis, as diatomaceous earth is readily available and the manufacturing process is simple. Demand for kieselguhr has increased and new factories are to be established which may result in new cases of silicosis.

Respiratory effects and serum type III procollagen in potato sorters exposed to diatomaceous earth.

Exposure to diatomaceous earth with low crystalline silica content (< 1%) is rarely reported to cause pneumoconiotic disease, whereas airway obstruction and bronchitis are more frequently reported. We investigated the occurrence of pneumoconiosis and airflow limitation in 172 male workers from 5 potato sorting plants (55 controls, 29 salesmen, 72 currently exposed, and 16 retired exposed) exposed to inorganic dust from former sea terraces (7.7-15.4 mg/m3), high in diatomaceous earth. The presence of fibrosis was evaluated by chest radiographs (exposed only) and serum levels of type III procollagen (P-III-P) were measured as an estimate of fibrogenetic activity. Lung function was assessed by flow volume curves and impedance measurements. A validated questionnaire was used to record respiratory symptoms. No pneumoconiotic abnormalities were demonstrated by chest radiographs. In line with this finding, serum P-III-P levels were not elevated in exposed workers as compared to controls, suggesting no differences in fibrogenetic activity. In fact, serum P-III-P levels decreased significantly (P < 0.03) with increasing cumulative exposure. Flow volume parameters indicated airflow obstruction, dose-related to (cumulative) dust exposure; the annual decline in forced expiratory flow volume (FEV1) was estimated at 10.5 ml/year (P < 0.05). Airway obstruction was confirmed by impedance analysis: In the retired group impedance changes were compatible with airway obstruction extending into the peripheral airways. We conclude that this exposure to quartz during potato sorting does not result in an increased risk for pneumoconiosis, but that (prolonged) surveillance in this group is desirable in order to detect early indications of airflow obstruction.

Reanalysis of mortality from lung cancer among diatomaceous earth industry workers, with consideration of potential confounding by asbestos exposure.

OBJECTIVE: To evaluate the potential for confounding from asbestos exposure, primarily chrysotile, on the relation between crystalline silica and mortality from lung cancer among diatomaceous earth (diatomite) workers. METHODS: A reanalysis of a cohort mortality study of diatomite workers was performed to take into account quantitative estimates of asbestos exposure. The reanalysis was limited to a subset of the original cohort, comprising 2266 white men for whom asbestos exposure could be reconstructed with greatest confidence. Comparisons between mortality from lung cancer (standardised mortality ratios (SMR)) were made between rates for 1942-87 for United States white men, and workers cross classified according to cumulative exposures to crystalline silica and asbestos. Comparisons of internal rates, involving Poisson regression modeling, were conducted for exposure to crystalline silica, with and without adjustment for asbestos exposure. Exposures were lagged by 15 years to take into account disease latency. RESULTS: There was an overall excess of lung cancer (SMR 1.41; 52 observed). The SMRs for four categories of increasing crystalline silica among the workers not exposed to asbestos were 1.13, 0.87, 2.14, 2.00. An SMR of 8.31 (three observed) was found for workers with the highest cumulative exposure to both dusts. Internal analysis, after adjustment for asbestos exposure, yielded rate ratios for categories of exposure to crystalline silica: 1.00 (reference), 1.37, 1.80, and 1.79. CONCLUSIONS: Asbestos exposure was not an important confounder of the association between crystalline silica and mortality from lung cancer in this cohort. Although based on a small number of deaths from lung cancer, the data suggest possible synergy between these exposures. An extended follow up of this cohort is in progress and should enable better assessments of independent and combined effects on risk of lung cancer.

A phase I study of chemically synthesized verotoxin (Shiga-like toxin) Pk-trisaccharide receptors attached to chromosorb for preventing hemolytic-uremic syndrome.

A double-blind, placebo-controlled study was conducted to document possible side effects associated with oral consumption of synthetic verotoxin (VT, shiga-like toxin) Pk-trisaccharide receptor sequences attached to Chromosorb (Synsorb-Pk) by healthy adult volunteers. Synsorb-Pk reclaimed from volunteer stool samples was also analyzed to determine if its VT-binding activity was affected by exposure to the pH extremes and digestive processes of the human gastrointestinal tract. No participant reported any Synsorb-Pk-related adverse reactions, and no clinically important trends in laboratory data were evident. Synsorb-Pk recovered from stools retained its ability to absorb VT in polymyxin extracts of VT-producing Escherichia coli and also neutralized VT when mixed in vitro with VT-positive stools from children with hemorrhagic colitis or hemolytic-uremic syndrome (HUS). These results suggest a potential use for Synsorb-Pk in preventing HUS in patients infected with VT-producing E. coli.

Crystalline silica exposure and lung cancer mortality in diatomaceous earth industry workers: a quantitative risk assessment.

OBJECTIVE: To use various exposure-response models to estimate the risk of mortality from lung cancer due to occupational exposure to respirable crystalline silica dust. METHODS: Data from a cohort mortality study of 2342 white male California diatomaceous earth mining and processing workers exposed to crystalline silica dust (mainly cristobalite) were reanalyzed with Poisson regression and Cox's proportional hazards models. Internal and external adjustments were used to control for potential confounding from the effects of time since first observation, calendar time, age, and Hispanic ethnicity. Cubic smoothing spline models were used to assess the fit of the models. Exposures were lagged by 10 years. Evaluations of the fit of the models were performed by comparing their deviances. Lifetime risks of lung cancer were estimated up to age 85 with an actuarial approach that accounted for competing causes of death. RESULTS: Exposure to respirable crystalline silica dust was a significant predictor (p<0.05) in nearly all of the models evaluated and the linear relative rate model with a 10 year exposure lag seemed to give the best fit in the Poisson regression analysis. For those who died of lung cancer the linear relative rate model predicted rate ratios for mortality from lung cancer of about 1.6 for the mean cumulative exposure to respirable silica compared with no exposure. The excess lifetime risk (to age 85) of mortality from lung cancer for white men exposed for 45 years and with a 10 year lag period at the current Occupational Safety and Health Administration (OSHA) standard of about 0.05 mg/m(3) for respirable cristobalite dust is 19/1000 (95% confidence interval (95% CI) 5/1000 to 46/1000). CONCLUSIONS: There was a significant risk of mortality from lung cancer that increased with cumulative exposure to respirable crystalline silica dust. The predicted number of deaths from lung cancer suggests that current occupational health standards may not be adequately protecting workers from the risk of lung cancer.

A 26-year radiographic follow-up of workers in a diatomite mine and mill.

Chest roentgenograms of 473 employees of a California diatomite plant were reviewed as part of periodic reevaluation of the efficacy of the dust control program. The plant's processing of diatomite included flux-calcination, which provided opportunities for exposure to cristobalite. The films examined were those of workers with at least five years of service. Only 11 films were interpreted as showing changes consistent with pneumoconiosis, i.e., small opacities of profusion categorized as 1/1 or greater. Only six were classified as 1/2 or more. All who developed categories 1/1 or higher during their employment had more than 25 years of service. No large opacities were reported. The low prevalence of abnormalities and the absence of definite pneumoconiosis in employees with fewer than 25 years of service was in striking contrast with findings in 1953. At that time more than 25% of those with five or more years of employment had roentgenographic evidence of pneumoconiosis and over 10% had confluent changes producing large opacities.

Pooled exposure-response analyses and risk assessment for lung cancer in 10 cohorts of silica-exposed workers: an IARC multicentre study.

OBJECTIVES: Silica is one of the most common occupational exposures worldwide. In 1997 the International Agency for Research on Cancer (IARC) classified inhaled crystalline silica as a human carcinogen (group 1), but acknowledged limitations in the epidemiologic data, including inconsistencies across studies and the lack of extensive exposure-response data. We have conducted a pooled exposure-response analysis of 10 silica-exposed cohorts to investigate lung cancer. METHODS: The pooled cohort included 65,980 workers (44,160 miners, 21,820 nominees), and 1,072 lung cancer deaths (663 miners, 409 nonminers). Follow-up has been extended for five of these cohorts beyond published data. Quantitative exposure estimates by job and calendar time were adopted, modified, or developed to permit common analyses by respirable silica (mg/m3) across cohorts. RESULTS: The log of cumulative exposure, with a 15-year lag, was a strong predictor of lung cancer (p = 0.0001), with consistency across studies (test for heterogeneity, p = 0.34). Results for the log of cumulative exposure were consistent between underground mines and other facilities. Categorical analyses by quintile of cumulative exposure resulted in a monotonic trend with odds ratios of 1.0. 1.0, 1.3, 1.5, 1.6. Analyses using a spline curve also showed a monotonic increase in risk with increasing exposure. The estimated excess lifetime risk (through age 75) of lung cancer for a worker exposed from age 20 to 65 at 0.1 mg/m3 respirable crystalline silica (the permissible level in many countries) was 1.1-1.7%, above background risks of 3-6%. CONCLUSIONS: Our results support the decision by the IARC to classify inhaled silica in occupational settings as a carcinogen, and suggest that the current exposure limits in many countries may be inadequate. These data represent the first quantitative exposure-response analysis and risk assessment for silica using data from multiple studies.