Supplementation of alanine improves biomass accumulation and lipid production of Chlorella pyrenoidosa by increasing the respiratory and metabolic processes

The function of exogenous alanine(Ala)in regulating biomass accumulation,lipid production,photosynthesis,and respiration in Chlorella pyrenoidosa was studied.Result shows that the supplementation of Ala increased C.pyrenoidosa biomass and lipid production in an 8-d batch culture.The concentration of 10 mmol/L of Ala was optimum and increased the microalgal cell biomass and lipid content by 39.3%and 21.4%,respectively,compared with that in the control(0-mmol/L Ala).Ala supplementation reduced photosynthetic activity while boosting respiratory activity and pyruvate levels,indicating that C.pyrenoidosa used exogenous Ala for biomass accumulation through the respiratory metabolic process.The accelerated respiratory metabolism due to Ala supplementation elevated the substrate pool and improved the lipogenic gene expression,promoting lipid production at last.This study provided a novel method for increasing biomass accumulation and lipid production and elucidated the role of Ala in regulating lipid production.

Effects of the prone position on arterial blood gas analysis and respiratory parameters of acute respiratory distress syndrome patients:An observational retrospective study

Objective:To investigate the effect of the first prone position on arterial blood gas analysis and respiratory parameters of acute respiratory distress syndrome(ARDS)patients with and without COVID.Methods:This study was conducted retrospectively with 22 COVID-ARDS and 22 non-COVID ARDS patients,who were placed in a prone position for at least 16 hours on the first day at the intensive care unit admission,and arterial blood gas analysis was taken in the pre-prone,prone and post-prone periods.Results:PaO2 were significantly increased in the pre-prone vs.prone comparison in both groups,but the increase in the PaO2/FiO2 ratio was not significant.In comparing the pre-prone vs.post-prone PaO2/FiO2 ratios,there was a significant difference only in the non-COVID ARDS group.Conclusions:The improved oxygenation provided by prone positioning is more permanent with the“post-prone effect”in non-COVID ARDS patients.This can be attributed to the differences in the pathogenesis of the two ARDS types.

Risk Factors Associated with Non-Compliance with Respiratory Protection Programs among Firefighters

Non-compliance with respiratory protection programs among firefighters may put them at increased risk of injury and illness from occupational exposures during fire extinguishing activities. This research aims to characterize respiratory protection practices among Florida firefighters. This information will allow better understanding of factors that are associated with non-compliance with respiratory protection guidelines. A survey questionnaire was used to characterize Florida fire departments in this cross-sectional study. Four hundred and seventy-seven surveys were administered to Florida firefighters both in person and electronically to collect information regarding firefighter knowledge and participation in their respective respiratory protection programs during the past twelve months. Survey questions were developed from the model set by the National Fire Protection Association (NFPA) which provides standards and regulations regarding firefighter protections. Summary statistics regarding firefighter department size, coverage area, and firefighter employment type were produced. Multinomial logistic regression analysis was performed to evaluate factors that impact respiratory protection programs. The 477 respondents were 91% male with a mean age of 39 years old (range 21 - 65 years). The majority of respondents, 76%, were non-smokers, 21% former smokers, and 3% current smokers. In regard to ethnicity, respondents were 77% Caucasian, 13% Hispanic, 3% African American, and 4% other. Most respondents were career firefighters, 97%, with less than ten years of experience, 44%, working in a fire department with at least 21 firefighters, 98%. Most respondents, 80%, had a written respiratory program in place. The most cited reason for not having implemented a written respiratory protection program was lack of knowledge related to the program. Multinomial logistic regression analysis of departments with response areas of at least 250,000 square miles produced a statistically significant 0.444 (0.219 - 0.901 CI) odds ratio for having a written respiratory program as compared to those with a less than 10,000 square miles response area. Additional resources need to be given to Florida fire departments to ensure that all firefighters receive adequate respiratory protection in accordance with NFPA guidelines. There is an association between fire departments with large response areas and non-compliance with respiratory protection guidelines in regard to: having a written respiratory program, the frequency of respiratory fit testing, and the frequency of medical fitness testing. This suggests that rural fire departments need additional resources to ensure firefighters are adequately protected. Additional research should focus on why these differences exist in the rural fire departments. Respondents stating a lack of knowledge or no requirement for a written respiratory program suggest that future efforts should focus on respiratory protection education and training.

Performance of N95 elastomeric respirators in high humidity and high coal dust concentration environment

High humidity and high dust concentration in deep coal mines may severely challenge the performance of respirators worn by coal miners.This paper aims at quantitatively evaluating the respirators used in deep coal mines and providing scientific guidance for the respiratory protection of miners.Based on the self-designed in-situ PM2.5 collector,controllable PM2.5 generator,human breathing simulator,and respirator simulation testing system,under the simulated deep mine working condition,this study investigated the effects of dust loading,wearing time,and dust concentration on the filtration efficiency,breathing resistance,and quality factor of N95 elastomeric respirators.With the increase of dust loading,the respirator filtration efficiency firstly decreased,then increased(minimum value 97.5%).The breathing resistance increased exponentially from 120 to 180 to 1020-1530 Pa,and the quality factor decreased logarithmically from 0.051 to 0.076 to 0.0058-0.0085 Pa^(-1).As the PM2.5 coal dust concentration increased from 5 to 50 mg/m^(3),the wearing time for the respirator breathing resistance to exceed 300 Pa reduced from 7 h to less than 1 h.One N95 elastomeric respirator is not able to perform an 8-h work shift.To avoid the excessive breathing resistance caused by dust loading,more filter cartridges are needed for coal miners.

Effect of Respirator Resistance on Tolerant Capacity during Graded Load Exercise

Respirator breathing resistance impacts performance of wearers during constant work load. However, it is less clear as to how breathing resistance affects the tolerant capacity of users during graded work load. The present study investigated the tolerant capacity of 8 individuals during incremental work load. The 8 subjects were required to wear two matched respirators （respirators Ⅰ and Ⅱ which were designed to have different breathing resistances and the same dead space） respectively on separate days and then work to end points. Minute ventilation （VE）, breathing frequency （BF）, oxygen consumption （VO2） and heart rate （HR） were recorded during exercise, while tolerant time, response time and breathing discomfort were measured at the end of each test trial. The test variables were com-pared between the two respirators by using matched-pairs t-test. The results showed that the tolerant time was significantly reduced for the respiratorⅠwith higher level of breathing resistance when compared with its counterpart with lower breathing resistance （respirator Ⅱ） （P〈0.05）. The same changes occurred for response time. Results also showed a significant increase in VE and BF for respirator Ⅰwearers when the work load was above 125 W. The O2 consumption was similar under the two breathing resistance conditions. These findings suggested that the respiratory resistance caused by self-contained breathing apparatus （SCBA） has an impact on the tolerant capacity of users.

Protection Performance Evaluationof the Respirators and PersonalExposure Measurement in aBelgian Viscose Rayon Factory

This paper presents the evaluation results of protective performance of the respirators (full face supplied-fresh air respirators and half-mask active charcoal filter) and personal exposure measurement (Infacepiece sampling) in a Belgian viscose rayon factory. With in-facepiece sampling technique and personal sampling method, we measured the CS2 concentrations inside and outside of the different respirators. We found two kinds of the respirators have significant effect on decreasing the CS2 exposure level for the subject, especially for the spinners. Full face supplied-fresh air respirator have good protective effect for the spinners and have limit protection for the high exposure job although the PF value is more than 10. It still need to improve more. In-facepiece sampling for all the subjects exposed to CS2 in the factory found most subjects have exposed to low CS2 concentration, most exposure levels were under the control range, but sulfuror are high exposure, the exposure level is higher than ACGIH TLV value.

Evaluation of Nasal Functions While Wearing N95 Respirator and Surgical Facemask

There is a lack of reported studies on how the long duration wearing of N95 respirators or surgical facemasks will affect the upper airway functions. Considering the frequency of mask wearing especially in hospitals and during an outbreak of influenza, it is essential to have such data documented. Therefore, the current study is to establish the effect of long duration wearing of N95 and surgical facemasks on upper airway functions. 47 staffs of National University Hospital Singapore in 2013 were recruited. Each of the volunteers wore both N95 respirator and surgical facemask for 3 hours on two different days. During the period of mask wearing, relative airflow rates were recorded. Smell function test was carried out before and after mask wearing. The results show that no significant change of smell test score was found after removal of both the two types of masks. With N95 respirator, more air was breathed into the upper airways compared to surgical facemask.

Do increasing respiratory costs explain the decline with age of forest growth rate?

Once forests have achieved a full canopy, their growth rate declines progressively with age. This work used a global data set with estimates from a wide range of forest types, aged 20-795 years, of their annual photosynthetic production(gross primary production, GPP) and subsequent above-plus below-ground biomass production(net primary production, NPP). Both GPP and NPP increased with increasing mean annual temperature and precipitation. GPP was then unrelated to forest age whilst NPP declined progressively with increasing age. These results implied that autotrophic respiration increases with age. It has been proposed that GPP should decline in response to increasing water stress in leaves as water is raised to greater heights as trees grow taller with age. However, trees may make substantial plastic adjustment in mor phology and anatomy of newly developing leaves, xylem and fi ne roots to compensate for this stress and maintain GPP with age. This work reviews the possibilities that NPP declines with age as respiratory costsincrease progressively in, any or all of, the construction and maintenance of more complex tissues, the maintenance of increasing amounts of live tissue within the sapwood of stems and coarse roots, the conversion of sapwood to hear twood, the increasing distance of phloem transport, increased turnover rates of fine roots, cost of supporting very tall trees that are unable to compensate fully for increased water stress in their canopies or maintaining alive competitively unsuccessful small trees.

Respiratory plasticity following spinal cord injury:perspectives from mouse to man

The study of respiratory plasticity in animal models spans decades.At the bench,researchers use an array of techniques aimed at harnessing the power of plasticity within the central nervous system to restore respiration following spinal cord injury.This field of research is highly clinically relevant.People living with cervical spinal cord injury at or above the level of the phrenic motoneuron pool at spinal levels C3-C5 typically have significant impairments in breathing which may require assisted ventilation.Those who are ventilator dependent are at an increased risk of ventilator-associated co-morbidities and have a drastically reduced life expectancy.Pre-clinical research examining respiratory plasticity in animal models has laid the groundwork for clinical trials.Despite how widely researched this injury is in animal models,relatively few treatments have broken through the preclinical barrier.The three goals of this present review are to define plasticity as it pertains to respiratory function post-spinal cord injury,discuss plasticity models of spinal cord injury used in research,and explore the shift from preclinical to clinical research.By investigating current targets of respiratory plasticity research,we hope to illuminate preclinical work that can influence future clinical investigations and the advancement of treatments for spinal cord injury.

Respiratory Response of Dormant Nectarine Vegetative Buds to High Temperature Stress

High temperature stress （HT） is efficient in breaking endo-dormancy of perennial trees. The effects of HT （50°C） on the respiration of dormant nectarine （Prunus persica var. nectariana cv. Shuguang） vegetative buds were evaluated in the research. We found that bud respiration was transiently inhibited by HT and the pentose phosphate pathway （PPP） and the cytochrome C pathway （CYT） were significantly affected. On the substrate level, PPP was activated in the HT-treated buds compared with the control group. However, the activation did mot occur until hours after HT treatment. The tricarboxylic acid cycle （TCA） in both the HT-treated buds and in the control group proceeded at a low level most of the time compared with total respiration. On the electron transfer level, CYT was transiently inhibited by HT but became significantly active in the later stage. CYT operation in the control group exhibited an attenuation process. The alternative pathway （ALT） fluctuated both in the HT-treated samples and in the control. The results suggest that the temporary CYT inhibition and the following PPP activation may be involved in HT-induced bud dormancy release and budburst mechanisms.

Stem radial CO_2 conductance affects stem respiratory CO_2 fluxes in ash and birch trees

The CO_2 released from respiring cells in woody tissues of trees can contribute to one of three fluxes:efflux to the atmosphere(E_A),internal xylem sap transport flux(F_T),and storage flux(DS).Adding those fluxes together provides an estimate of actual stem respiration(R_S).We know that the relative proportion of CO_2 in those fluxes varies greatly among tree species,but we do not yet have a clear understanding of the causes for this variation.One possible explanation is that species differ in stem radial CO_2 conductance(g_c).A high g_c would favor the E_A pathway and a low g_cwould favor the F_Tpathway.However,g_chas only been measured once in situ and only in a single tree species.We measured g_cusing two methods in stems of Fraxinus mandshurica Rupr.(ash)and Betula platyphylla Suk.(birch)trees in situ,along with R_S,E_A,F_T and DS.Stem radial CO_2 conductance was substantially greater in ash trees than in birch trees.Corresponding to that finding,in ash trees over 24 h,E_Aconstituted the entire flux of respired CO_2 ,and F_Twas negative,indicating that additional CO_2 ,probably transported from the root system via the xylem,was also diffusing into the atmosphere.In ash trees,F_T was negative over the entire 24 h,and this study represents the first time that has been reported.The addition of xylem-transported CO_2 to E_A caused E_Ato be 9% higher than the actual R_Sover the diel measurement period.Birch trees,which had lower g_c,also had a more commonly seen pattern,with E_A accounting for about 80% of the CO_2 released from local cell respiration and F_T accounting for the remainder.The inorganic carbon concentration in xylem sap was also lower in ash trees than in birch trees:2.7 versus 5.3 mmol L^(-1),respectively.Our results indicate that stem CO_2 conductance could be a very useful measurement to help explain differences among species in the proportion of respired CO_2 that remains in the xylem or diffuses into the atmosphere.

Acute Toxicity and Cardio-Respiratory Effects of 2-Deoxy-D-Glucose: A Promising Radio Sensitiser

Objective To evaluate the acute toxicity of 2-deoxy-D-glucose （2DG） by oral （p.o.） and intravenous （i.v.） routes, and also the cardio-respiratory effects following high doses of 2DG in animal models. Methods The LD50 of 2DG （in water） was determined in rats and mice by p.o. route and in mice by i.v. route. The effect of 2-DG （250 mg/kg, 500 mg/kg, and 1000 mg/kg, i.v.） was studied on various cardio-respiratory parameters viz., mean arterial blood pressure, heart rate and respiratory rate in anaesthetised rats. The effect of 2DG （500 mg/kg, 1000 mg/kg, and 2000 mg/kg, p.o.） was also studied on various respiratory parameters viz., respiratory rate and tidal volume in conscious rats and mice using a computer program. Results The p.o. LD50 of 2DG was found to be 〉8000 mg/kg in mice and rats, and at this dose no death was observed. The LD50 in mice by i.v. route was found to be 8000 mg/kg. At this dose 2 out of 4 mice died and the death occurred within 6 h. A significant increase in the body weight was observed after p.o. administration of 2DG in rats at 500 mg/kg, 1000 mg/kg, and 2000 mg/kg doses. There was no significant change in the body weight at 4000 mg/kg and 8000 mg/kg by the p.o. route in rats and up to 8000 mg/kg by p.o. as well as i.v. routes in mice. Intravenous administration of 2DG （250 mg/kg, 500 mg/kg, and 1000 mg/kg） in anaesthetised rats showed a time-dependent decrease in the mean arterial blood pressure. There was no change in the heart rate in any of the treatment groups. The tidal volume was not changed significantly by p.o administration in conscious rats, but a significant decrease in the respiratory frequency at 500 mg/kg and 1000 mg/kg doses was observed. In the mice also there was no change in the tidal volume after p.o, administration, but the respiratory frequency decreased significantly at 2000 mg/kg dose. Conclusion 2DG is a safe compound but can cause a fall in the blood pressure and a decrease in respiratory frequency at high doses.

Starvation of the Respiratory Metabolism and Locomotion of Aurelia aurita s.l. Ephyrae

Blooms of the scyphozoan jellyfish Aurelia aurita are greatly regulated by the survival rate of planktonic ephyrae. The ecophysiology of ephyrae is poorly studied compared with polyps and medusae. As extremely strong starvation resistance and recovery capability of A. aurita ephyrae may due to its low metabolic rate as well as starvation may reduce the swimming ability of ephyrae which may lead to the higher predation loss, the effects of temperature and starvation on their respiration and pulsation rates were examined. In this study, ephyrae under different starvation conditions were measured by a fluorescence-based DO meter after 72 h incubation. And the pulsation rates were measured at every 10-d interval in 1-liter plastic bottle by a hand-held counter. The results showed that the mean respiration rates of newly released ephyrae were 0.24, 0.24 and 0.19 μl O2 ephyra-1 d-1 at 15°C, 12°C and 9°C, respectively, and the rates tended to decrease with increasing starvation duration. Carbon weight-specific respiration rates did not change significantly with starvation duration. The dry weight-specific respiration rates of newly released A. aurita ephyrae (i.e., 11.7-14.6 μl O2 mg DW-1 d-1) were nearly one order of magnitude lower than the rates for planktonic larvae of other taxa (e.g., molluscs, crustaceans and fish). The maximum pulsation rate taken by A. aurita ephyrae was 49.2 beats min-1, which represents the maximum swimming velocity to be 8.87 cm·min-1. The pulsation rates were not affected by temperature over the range between 9°C and 15°C. However, they were influenced by starvation duration. Starvation-derived decrease in pulsation together with associated body shrinkage may lead to lower encounter rate of prey and lower escaping ability from predators, which may lead to higher predation loss in the field.

Association between Respirable Dust Exposure and Respiratory Health Concerns among Workers in Apparel Processing Companies in Export Processing Zone (EPZ) in Machakos County, Kenya

Apparel processing is an essential industry in providing clothing needs for the population. The Export Processing Zone (EPZ) in Kenya employs many employees. Garment processing releases respirable dust particles, thus exposing workers to risks to the respiratory system. The study determined the respirable dust health concerns among workers in Apparel Processing Companies (APCs) in EPZ in Machakos County, Kenya. A cross-sectional descriptive design was employed where four companies were studied. Three hundred and sixty-seven participants were selected through systematic random sampling. Data was collected using questionnaires and Interview guides. The study established that workers were exposed to respirable dust PM2.5 ranging from 40.89 ± 24.0 μg·m−3 to 87.49 ± 45.2 μg·m−3 with a mean of 65.61 ± 31.5 μg·m−3. While PM2.5 ranged from 63.59 ± 21.2 μg·m−3 to 313.41 ± 468.0 μg·m−3. With a mean of 104.02 ± 26.0 μg·m−3. Workers complained of different respirable dust-related diseases. The most prevalent conditions were sneezing and coughing (86.4%), chest pains (41.1%), blocked chests (36.8%), and allergic reactions to dust (18.3%). The APC should develop an OSH management system that includes;a dust management policy, dust monitoring, Risk Assessments, Engineering controls installations, medical examination, Training on dust management, PPE provision, and use enforcement.

Commentary: Inhibitors of mitochondrial respiratory chain in the treatment of type 2 diabetes

Prevalence of type 2 diabetes has been increased worldwide following the high incidence of obesity and growing population of aging, which are two conditions for absolute energy excess with accumulation of TAG in the body and relative energy excess due to reduced energy expense, respectively. It appears that type 2 diabetes is a compensatory mechanism of body to energy excess through urine discharge of glucose.

Clinical efficacy and safety of recruitment maneuver in patients with acute respiratory distress syndrome using low tidal volume ventilation： a multicenter randomized controlled clinical trial

Background The recruitment maneuver （RM） has been shown to improve oxygenation in some patients with acute respiratory distress syndrome. But there is a lack of standardization and lack of clinical studies to prove the improvement on clinical outcome. We conducted this study to evaluate the clinical efficacy and safety of the RM in patients with acute respiratory distress syndrome （ARDS） using Iow tidal volume ventilation.Methods We randomly assigned 110 patients with ARDS from 14 Chinese intensive care units （ICUs） at the tertiary teaching hospitals. Patients with PaO2 ≤200 mmHg at FiO2 1.0 and PEEP ≥10 cmH2O were included in the study.Patients were randomized into two groups： control group and RM group. The tidal volume was set to 6-8 mi per kilogram of predicted body weight （PBW） in both groups. RM was performed by continuous positive airway pressure （CPAP） of 40 cmH2O maintained for 40 seconds. RMs was conducted every eight hours for the first five days, or stopped within five days if the patient reached the weaning standard.Results One hundred and ten patients had completed the requirements for the primary study goals, 55 from the RM group and 55 control patients. Baseline characteristics remained similar in the two groups. In the RM group the PaO2/FiO2 was significantly increased compared to baseline at 120 minutes after RM on day one and day two （P=0.007and P=0.001）. There were no significant differences between the RM and control group in hospital mortality （41.8% vs.56.4%, P=0.13）, 28-day mortality （29.1% vs. 43.6%, P=0.11） and ventilator-free days at day 28 （10.8±10.1 vs. 7.4±10.0,P=0.08）. ICU mortality （32.7% vs. 52.7%, P=0.03）, the rate of survival with unassisted breathing for at least 48 consecutive hours at day 28 （58.2% vs. 36.2%, P=0.02）, and nonpulmonary organ failure-free days at day 28 （17.4±11.1vs. 13.0±12.0, P=0.03） favored the RM group. There was no significant difference in mean blood pressure and heart rate before RM and at 30, 60, 120 minutes after RM. There was no incidence of barotraumas.Conclusions RM was safe and useful for improving oxygenation in patients with ARDS who were ventilated with a low tidal volume, with a beneficial impact on their clinical outcome.

Long-term thinning decreases the contribution of heterotrophic respiration to soil respiration in subalpine plantations

Interest in the dynamics of soil respiration(R_(S))in subalpine forest ecosystems is increasing due to their high soil carbon density and potential sensitivity to environmental changes.However,as a principal silvicultural practice,the long-term impacts of thinning on R_(S) and its heterotrophic and autotrophic respiration components(R_(h) and Ra,respectively)in subalpine plantations are poorly understood,espe-cially in winter.A 3-year field observation was carried out with consideration of winter CO_(2) efflux in middle-aged sub-alpine spruce plantations in northwestern China.A trench-ing method was used to explore the long-term impacts of thinning on Rs,Rn and R_(a).Seventeen years after thinning,mean annual Rs,Rn and R_(a) increased,while the contribu-tion of R_(h) to R_(s) decreased with thinning intensity.Thinning significantly decreased winter R,because of the reduction in R_(n) but had no significant effect on Ra.The temperature sensitivity(Q_(10))of R_(h) and R_(a) also increased with thinning intensity,with lower Q_(10) values for R_(h)(2.1-2.6)than for Ra(2.4-2.8).The results revealed the explanatory variables and pathways related to R_(n) and R_(a) dynamics.Thinning increased soil moisture and nitrate nitrogen(NO_(3)^(-)-N),and the enhanced nitrogen and water availability promoted R_(h) and R_(a) by improving fine root biomass and microbial activity.Our results highlight the positive roles of NO_(3)^(-)-N in stimulating R_(s) components following long-term thinning.Therefore,applications of nitrogen fertilizer are not recommended while thinning subalpine spruce plantations from the perspective of reducing soil CO_(2) emissions.The increased Q_(10) values of R_(s) components indicate that a large increase in soil CO_(2) emissions would be expected following thinning because of more pronounced climate warming in alpineregions.

Effects of dust controls on respirable coal mine dust composition and particle sizes:case studies on auxiliary scrubbers and canopy air curtain

Control of dust in underground coal mines is critical for mitigating both safety and health hazards.For decades,the National Institute of Occupational Safety and Health(NIOSH)has led research to evaluate the effectiveness of various dust control technologies in coal mines.Recent studies have included the evaluation of auxiliary scrubbers to reduce respirable dust downstream of active mining and the use of canopy air curtains(CACs)to reduce respirable dust in key operator positions.While detailed dust characterization was not a focus of such studies,this is a growing area of interest.Using preserved filter samples from three previous NIOSH studies,the current work aims to explore the effect of two different scrubbers(one wet and one dry)and a roof bolter CAC on respirable dust composition and particle size distribution.For this,the preserved filter samples were analyzed by thermogravimetric analysis and/or scanning electron microscopy with energy dispersive X-ray.Results indicate that dust composition was not appreciably affected by either scrubber or the CAC.However,the wet scrubber and CAC appeared to decrease the overall particle size distribution.Such an effect of the dry scrubber was not consistently observed,but this is probably related to the particular sampling location downstream of the scrubber which allowed for significant mixing of the scrubber exhaust and other return air.Aside from the insights gained with respect to the three specific dust control case studies revisited here,this work demonstrates the value of preserved dust samples for follow-up investigation more broadly.

Advancing respirable coal mine dust source apportionment:a preliminary laboratory exploration of optical microscopy as a novel monitoring tool

Exposure to respirable coal mine dust(RCMD)can cause chronic and debilitating lung diseases.Real-time monitoring capabilities are sought which can enable a better understanding of dust components and sources.In many underground mines,RCMD includes three primary components which can be loosely associated with three major dust sources:coal dust from the coal seam itself,silicates from the surrounding rock strata,and carbonates from the inert‘rock dust’products that are applied to mitigate explosion hazards.A monitor which can reliably partition RCMD between these three components could thus allow source apportionment.And tracking silicates,specifically,could be valuable since the most serious health risks are typically associated with this component-particularly if abundant in crystalline silica.Envisioning a monitoring concept based on field microscopy,and following up on prior research using polarized light,the aim of the current study was to build and test a model to classify respirable-sized particles as either coal,silicates,or carbonates.For model development,composite dust samples were generated in the laboratory by successively depositing dust from high-purity materials onto a sticky transparent substrate,and imaging after each deposition event such that the identity of each particle was known a priori.Model testing followed a similar approach,except that real geologic materials were used as the source for each dust component.Results showed that the model had an overall accuracy of 86.5%,indicating that a field-microscopy based moni-tor could support RCMD source apportionment and silicates tracking in some coal mines.