Establishing short-term occupational exposure limits (STELs) for sensory irritants using predictive and in silico respiratory rate depression (RD50) models.

Sensory irritation is a health endpoint that serves as the critical effect basis for many occupational exposure limits (OELs). Schaper 1993 described a significant relationship with high correlation between the measured exposure concentration producing a 50% respiratory rate decrease (RD50) in a standard rodent assay and the American Conference of Governmental Industrial Hygienists (ACGIH®) Threshold Limit Values (TLVs®) as time-weighted averages (TWAs) for airborne chemical irritants. The results demonstrated the potential use of the RD50 values for deriving full-shift TWA OELs protective of irritant responses. However, there remains a need to develop a similar predictive model for deriving workplace short-term exposure limits (STELs) for sensory irritants. The aim of our study was to establish a model capable of correlating the relationship between RD50 values and published STELs to prospectively derive short-term exposure OELs for sensory irritants. A National Toxicology Program (NTP) database that included chemicals with both an RD50 and established STELs was used to fit several linear regression models. A strong correlation between RD50s and STELs was identified, with a predictive equation of ln (STEL) (ppm) = 0.86 * ln (RD50) (ppm) - 2.42 and an R2 value of 0.75. This model supports the use of RD50s to derive STELs for chemicals without existing exposure recommendations. Further, for data-poor sensory irritants, predicted RD50 values from in silico quantitative structure activity relationship (QSAR) models can be used to derive STELs. Hence, in silico methods and statistical modeling can present a path forward for establishing reliable OELs and improving worker safety and health.

Visualizing the NIOSH Pocket Guide: Open-source web application for accessing and exploring the NIOSH Pocket Guide to Chemical Hazards.

The NIOSH Pocket Guide to Chemical Hazards is a trusted resource that displays key information for a collection of chemicals commonly encountered in the workplace. Entries contain chemical structures-occupational exposure limit information ranging from limits based on full-shift time-weighted averages to acute limits such as short-term exposure limits and immediately dangerous to life or health values, as well as a variety of other data such as chemical-physical properties and symptoms of exposure. The NIOSH Pocket Guide (NPG) is available as a printed, hardcopy book, a PDF version, an electronic database, and a downloadable application for mobile phones. All formats of the NIOSH Pocket Guide allow users to access the data for each chemical separately, however, the guide does not support data analytics or visualization across chemicals. This project reformatted existing data in the NPG to make it searchable and compatible with exploration and analysis using a web application. The resulting application allows users to investigate the relationships between occupational exposure limits, the range and distribution of occupational exposure limits, and the specialized sorting of chemicals by health endpoint or to summarize information of particular interest. These tasks would have previously required manual extraction of the data and analysis. The usability of this application was evaluated among industrial hygienists and researchers and while the existing application seems most relevant to researchers, the open-source code and data are amenable to modification by users to increase customization.

Does exposure to ammonia concentrations lower than the threshold limit value cause acute pulmonary effects?

One of the major toxic effects of exposure to ammonia is the resulting pulmonary acute and chronic effects. This study investigated the acute pulmonary effects of exposure to ammonia lower than the recommended threshold limit value (TLV). This cross-sectional study was conducted in 2021 in four chemical fertilizer production industries using ammonia as the main raw material. A total of 116 workers who were exposed to ammonia were investigated. The level of exposure to ammonia was measured by NMAM 6016, and the evaluation of pulmonary symptoms and function parameters was done using the American Thoracic Society and European Respiratory Society protocols in four sessions. The paired-sample t-test, repeated measures test, Chi-square, and Fisher's exact test were run to analyze the collected data. The prevalence rates of pulmonary symptoms, including cough, dyspnea, phlegm, and wheezing, were 24.14, 17.24, 14.66, and 16.38%, respectively, after one exposure shift. It was observed that all pulmonary function parameters were reduced after one exposure shift to ammonia. The results revealed that the parameters of vital capacity, forced vital capacity (FVC), forced expiratory volume in the first second (FEV1), the FEV1/FVC ratio, and peak expiratory flow significantly decreased (p < 0.05) across four exposure shifts. The findings indicated that exposure to ammonia at concentrations lower than one-fifth of TLV could bring about acute pulmonary effects and reduce pulmonary function parameters, similar to the pattern observed in obstructive pulmonary diseases.

Approaches for the setting of occupational exposure limits (OELs) for carcinogens.

This article addresses issues of importance for occupational exposure limits (OELs) and chemical carcinogens with a focus on non-threshold carcinogens. It comprises scientific as well as regulatory issues. It is an overview, not a comprehensive review. A central topic is mechanistic research and insights, and its implications for cancer risk assessment. Alongside scientific advancements, the approaches of hazard identification and qualitative and quantitative risk assessment have developed over the years. The key steps in a quantitative risk assessment are outlined, with special attention given to the dose-response assessment and the derivation of an OEL using risk calculations or default assessment factors. The work procedures of several bodies performing cancer hazard identifications and quantitative risk assessments, as well as regulatory procedures to derive OELs for non-threshold carcinogens, are presented. Non-threshold carcinogens for which the European Union (EU) introduced binding OELs in 2017-2019 serve as illustrations together with some currently used strategies in the EU and elsewhere. Available knowledge supports the derivation of health-based OELs (Hb-OELs) for non-threshold carcinogens, and the use of a risk-based approach with low-dose linear extrapolation (linear non-threshold, LNT) as the default for non-threshold carcinogens. However, there is a need to develop methods that allow recent years' advances in cancer research to be used for improving risk estimates. It is recommended that defined risk levels (terminology and numerical values) are harmonised, and that both collective and individual risks are considered and clearly communicated. Socioeconomic aspects should be dealt with transparently and separated from the scientific health risk assessment.

Comparison of ACGIH lifting threshold limit values to validated low back disorder lifting assessment methods outcomes.

BACKGROUND: Work-related low back pain (LBP) increases the workforce disability and healthcare costs. This study evaluated the LBD risk level associated with handling the ACGIH TLVs in lifting tasks corresponding to various horizontal and vertical zones. OBJECTIVE: The aim of this study was to compare the low-risk ACGIH TLV to risk outcomes from various validated lifting assessment methods, including the OSU LBD Risk Model, NIOSH Lifting Equation, and LiFFT. METHODS: Twenty-four subjects were recruited for this study to perform various lifting conditions. The various ergonomic assessment methods were then used to obtain the risk assessment outcomes. RESULTS: The selected assessment methods showed that the ACGIH-defined TLVs are associated with less than high-risk for LBD for all the assessed tasks. The findings showed a moderate agreement (Kendall's W = 0.477) among the various assessment methods risk outcomes. The highest correlation (ρ= 0.886) was observed between the NIOSH Lifting Equation and LiFFT methods risk assessment outcomes. CONCLUSION: The findings showed that ACGIH-defined TLVs possesses less than high-risk for LBD. The outcomes of the selected ergonomic assessment methods moderately agree to each other.

Recommendation for an occupational exposure limit for toluene.

The Lower Olefins and Aromatics (LOA) REACH Consortium, which includes toluene registrants in the EU, established a Working Group (WG) to conduct a review of the occupational exposure limit (OEL) for toluene. The review focussed on CNS and neuro-behavioural toxicity, ototoxicity, effects on colour vision, reproductive and developmental effects, as safety signals for these effects were identified. The WG also examined the need for a skin notation and/or a short-term exposure limit (STEL). The WG critically reviewed and discussed the strengths and weaknesses of the available published information describing the effects of toluene in animals and humans, to assess its adequacy as a potential point of departure for the establishment of an OEL for toluene and to derive an OEL. As a result, the WG recommendation for a toluene OEL is 20 ppm 8-h TWA, with a 15-min STEL of 100 ppm and a skin notation.

Application of physiologically-based pharmacokinetic modeled toluene blood concentration in the assessment of short term exposure limits.

Toluene is a volatile hydrocarbon with solvent applications in several industries. Acute neurological effects in workers exposed to toluene have been reported in various publications. To inform the basis for a toluene Short Term Exposure Limit (STEL), studies of toluene-exposed workers were modeled using customized exposure scenarios within an existing physiologically-based pharmacokinetic (PBPK) model to simulate blood concentrations during individual studies. Maximum simulated blood concentration ranged from 0.3 to 1.7 (mean = 0.74 mg/L, median = 0.73, upper 95th percentile = 1.07) at the studies identified No Observed Adverse Effect Concentration (NOAEC). Maximum simulated blood concentration ranged from 0.7 to 4.1 mg/L (mean = 1.81, median = 1.63, lower 95th percentile = 0.92) at the studies identified Lowest Observed Adverse Effect Concentration (LOAEC). The maximum blood concentration for a 100 ppm STEL-like simulation was 0.4 mg/L, at the lower end of the NOAEC range and below the 95th percentile of the LOAEC. Therefore, it appears that a STEL <100 ppm would be unnecessary to protect workers due to peak occupational exposures to toluene.

Evaluating the threshold limit value of acceptable exposure concentration for exposure to bioaerosols in a wastewater treatment plant: Reverse-quantitative microbial risk assessment and sensitivity analysis.

Agitation operations produce numerous pathogenic bioaerosols in WWTPs1. QMRA2 can determine risks of persons exposed to these bioaerosols. However, QMRA framework cannot help stakeholders in immediately deciding whether a risk is intolerable. Thus, evaluating threshold of acceptable exposure concentration is an urgent issue but is still rarely addressed in WWTPs. This study analyzed TLV3 benchmarks of E. coli and S. aureus bioaerosols emitted from a WWTP by reverse-QMRA. Furthermore, variance of input parameters was clarified by sensitivity analysis. Results showed that, under conservative and optimistic estimates, TLV of technicians was 1.52-2.06 and 1.26-1.68 times as large as those of workers, respectively; wearing mask drive TLV up to 1-2 orders of magnitude; TLV of M4 was at most 1.33 and 1.31 times as large as that of RD5, respectively. For sensitivity analysis, removal fraction by equipping PPE enlarge TLV for effortlessly obtaining an acceptable assessment result; exposure time was dominant when without PPE excepting the scenario of technicians exposed to E. coli bioaerosol. This study helps establish threshold guidelines for bioaerosols in WWTPs and contribute innovative perspectives for stakeholders.

The use of scanning electron microscopy (SEM) and energy dispersiveX-ray analysis (EDXA) as a measurement tool for EMPs tasks, guidelines.

In a variety of European countries SEM/EDXA based methods are widely used for the measurements and judgements relating thereof regarding asbestos analysis. Most of these methods are used also for other fibrous particles, commonly indicated as Elongate Mineral Particles (EMPs). The span of guidelines reflects the broad use of SEM/EDXA as an analytical method. Guidelines regarding air measurements both for ambient and indoor air are well established. These methods are widely used as is shown in a proficiency testing scheme, organized by the British Health and Safety Executive (HSL) with participants from countries all over Europe and some countries from Asia and Africa. For workplaces a similar guideline with a reduced sensitivity is available, allowing measurements in higher dust concentrations. Features of the methods like analytical sensitivity, detection limits and measurement uncertainty are discussed. For material analysis we apply different analytical methods, using SEM/EDXA as a final step. They are different both in sample preparation and sensitivity. Most of the methods are qualitative or "semi-quantitative" and thought for the analysis of commercial asbestos containing products mainly. If quantitative analysis based on EDXA is used for identification other EMPs can be identified as well. An important tool is the morphological impression of the fibers or structures in the SEM in addition. Changes in regulations which may be expected, will modify some of the methods. Especially lowered Threshold Limit Values (TLV's) in occupational air measurements are difficult to achieve.

Telas na infância: postagens de especialistas em grupos de cuidadores no facebook / Screens in childhood: posts of specialists in caretakers' groups in the facebook / Pantallas en la infancia: las publicaciones de expertos en grupos de cuidadores en facebook

Apesar das crescentes investigações sobre uso de telas na infância, essa é uma temática complexa e ainda recente, que traz diversos desafios para pesquisadores e cuidadores. Comunidades virtuais em redes sociais são utilizadas por mães e pais para esclarecer dúvidas e receber conselhos acerca da parentalidade e saúde infantil, podendo, simultaneamente, assumir uma função prescritiva e normativa quanto ao seu modo de agir. Sendo assim, este artigo pretende compreender como o uso de telas na infância vem sendo abordado por especialistas em grupos de mães e pais no Facebook. Foi realizado um estudo qualitativo envolvendo 49 postagens de especialistas, sobretudo psicólogos e educadores, extraídas de cinco grupos públicos de mães e pais nessa rede social. Os textos das publicações foram verificados por meio de análise temática e discutidos com base no referencial teórico psicanalítico. Os resultados mostraram que os especialistas destacam os possíveis prejuízos do uso de telas na infância, além de fornecer orientações aos pais sobre como lidar com sua presença no cotidiano das crianças e de suas famílias. Concluiu-se que apesar dos grupos de cuidadores no Facebook serem uma ferramenta de divulgação de informações acerca do uso de telas na infância, cabe não naturalizar a presença de especialistas nesses espaços virtuais criados por pais e mães, interpondo-se nos saberes e nas trocas horizontalizadas entre os cuidadores.(AU)

Although investigations on the use of screens in childhood are increasing, this is a complex and recent topic, which poses several challenges for researchers and caregivers. Virtual communities in social networks are used by mothers and fathers to clarify doubts and receive advice regarding parenting and child health, at times, simultaneously, assuming a prescriptive and normative role on their way of acting. Therefore, this study aimed to understand how the use of screens in childhood has been approached by experts in groups of mothers and fathers on Facebook. A qualitative study was carried out involving 49 posts from specialists, mainly psychologists and educators, extracted from five public groups of mothers and fathers in this social network. The publications' texts were verified via thematic analysis and discussed based on the psychoanalytical theoretical framework. The results showed that experts highlight the possible damage of the use of screens in childhood, in addition to providing guidance to parents on how to deal with the presence of digital technology in the daily lives of children and families. It was concluded that, although caregivers' groups on Facebook are a tool for disseminating information about the use of screens in childhood, it is important not to naturalize the presence of specialists in these virtual spaces created by fathers and mothers, interposing in the horizontally interchanges that occur between the caregivers.(AU)

A pesar de las crecientes investigaciones sobre el uso de pantallas en la infancia, este es un tema complejo y aún reciente, que plantea varios desafíos para investigadores y cuidadores. Las comunidades virtuales en las redes sociales son utilizadas por madres y padres para aclarar dudas y recibir consejos sobre educación y salud infantil, pudiendo, al mismo tiempo, asumir un rol prescriptivo y normativo sobre su forma de actuar. Por lo tanto, este estudio tuvo como objetivo comprender cómo el uso de las pantallas en la infancia ha sido abordado por especialistas en grupos de madres y padres en Facebook. Se realizó un estudio cualitativo a partir de 49 publicaciones de especialistas, principalmente de psicólogos y educadores, extraídas de cinco grupos públicos de madres y padres en esta red social. Se realizó en los textos de las publicaciones un análisis temático y se utilizó el marco teórico psicoanalítico. Los resultados mostraron que los expertos destacan posibles daños que provoca el uso de pantallas en la infancia, además de orientar a los padres sobre cómo afrontar esta presencia de la tecnología digital en el día a día de los niños y sus familias. Se concluyó que, a pesar de que los grupos de cuidadores en Facebook son una herramienta de difusión de información sobre el uso de pantallas en la infancia, es importante no naturalizar la presencia de especialistas en estos espacios virtuales creados por padres y madres que se interpone entre los saberes e intercambios horizontales de los cuidadores.(AU)

An interdisciplinary framework for derivation of occupational exposure limits.

Protecting the health and safety of workers in industrial operations is a top priority. One of the resources used in industry to ensure worker safety is the occupational exposure limit (OEL). OELs are derived from the assessment and interpretation of empirical data from animal and/or human studies. There are various guidelines for the derivation and implementation of OELs globally, with a range of stakeholders (including regulatory bodies, governmental agencies, expert groups and others). The purpose of this manuscript is to supplement existing guidance with learnings from a multidisciplinary team approach within an industry setting. The framework we present is similar in construct to other risk assessment frameworks and includes: (1) problem formulation, (2) literature review, (3) weight of evidence considerations, (4) point of departure selection/derivation, (5) application of assessment factors, and the final step, (6) derivation of the OEL. Within each step are descriptions and examples to consider when incorporating data from various disciplines such as toxicology, epidemiology, and exposure science. This manuscript describes a technical framework by which available data relevant for occupational exposures is compiled, analyzed, and utilized to inform safety threshold derivation applicable to OELs.

Eficacia clínica de los umbrales de intervención híbridos y dependientes de la edad basados en FRAX en la población ecuatoriana / Clinical efficacy of FRAX-based age-dependent and hybrid intervention thresholds in the Ecuadorian population

Objetivo: Evaluar el impacto clínico de los umbrales de intervención basados en FRAX en mujeres ecuatorianas. Probar una combinación de umbrales de intervención fijo y específico de la edad para optimizar la selección de mujeres elegibles para intervención.Pacientes y métodos: Estudio transversal. Se seleccionaron 2.283 mujeres de 60 a 94 años. Calculamos el riesgo de fracturas osteoporóticas principales y de cuello de fémur con el modelo FRAX ecuatoriano (versión 4.1), y calculamos la proporción de individuos elegibles para tratamiento y evaluación de la densidad mineral ósea aplicando los umbrales específicos de edad de 60 a 94 años y un umbral fijo a partir de 75 años.Resultados: Aplicando los umbrales específicos de la edad, 2% de las mujeres calificaron para tratamiento y 73,7% para evaluación de la densidad mineral ósea. Según la edad, las mujeres elegibles para tratamiento fluctuaron entre 0,7 a 3,8% y las elegibles para evaluación de la densidad mineral ósea entre 58,3 al 80,5%.Con el umbral fijo, 31% de las mujeres calificaron para tratamiento y 76,3% para evaluación de la densidad mineral ósea. Dependiendo de la edad, las mujeres potencialmente elegibles para tratamiento fluctuaron de 3,8 a 76,5%, y las elegibles para evaluación de la densidad mineral ósea entre 65,2 al 85,4%.Conclusiones: La proporción de mujeres potencialmente elegible para el tratamiento, es baja comparada con países con riesgo alto de fracturas. Utilizar un umbral fijo a partir de los 75 años, optimiza la proporción de mujeres elegibles para tratamiento. En los países con riesgo de fractura bajo a moderado, con recursos limitados, un modelo híbrido puede ser más adecuado. (AU)

Carboxyhemoglobinemia as a laboratory finding in an outpatient

Resumen El monóxido de carbono (CO) es un gas producido principalmente por combustión incompleta de hidrocarburos. La intoxicación por exposición ambiental puede presentarse con síntomas inespecíficos y constituye la causa más importante de aumento de carboxihemoglobina (COHb). Su nivel en sangre depende de la duración de la exposición, la ventilación minuto y las concentraciones de CO y oxígeno en el ambiente. La elevada toxicidad radica en la hipoxia tisular que se genera. Se presenta el caso de un paciente masculino, 73 años, en seguimiento en el hospital por neumonía intersticial no específica como patología de base. En un control de laboratorio se encontró 11,9% de COHb, sin exposición a tabaco. No utilizaba calefacción a gas sino un panel cerámico eléctrico, recientemente pintado con esmalte sintético. La suspensión del uso del panel normalizó la COHb. El CO, producto de descomposición térmica del esmalte sintético, explica la causa de la intoxicación.

Abstract Carbon monoxide (CO) is a gas produced mainly by incomplete combustion of hydrocarbons. Poisoning from environmental exposure can present with nonspecific symptoms and is the most important cause of increased carboxyhemoglobin (COHb). Its blood level depends on the duration of exposure, minute ventilation, and the concentrations of CO and oxygen in the environment. The high toxicity lies in the tissue hypoxia that is generated. The case of a male patient, 73 years old, under follow-up in the hospital for non-specific interstitial pneumonia as the underlying pathology was presented. In a laboratory control, COHb 11,9% was found. There was no exposure to tobacco and there was no use of gas heating but of an electric ceramic panel, recently painted with synthetic enamel type paint. The suspension of the use of the panel normalised the COHb. The CO product of thermal decomposition of synthetic enamel explains the cause of poisoning.

Resumo O monóxido de carbono (CO) é um gás produzido principalmente pela combustão incompleta de hidrocarbonetos. A intoxicação por exposição ambiental pode se apresentar com sintomas inespecíficos e é a causa mais importante de aumento da carboxihemoglobina (COHb). Seu nível em sangue depende do tempo de exposição, da ventilação minuto e das concentrações de CO e oxigênio no ambiente. A alta toxicidade está na hipóxia tecidual gerada. Apresentamos o caso de um paciente do sexo masculino, 73 anos, em acompanhamento hospitalar por pneumonia intersticial inespecífica como patologia de bas. Em um controle laboratorial, achou-se 11,9% de COHb, sem exposição ao tabaco. Não utilizava aquecimento a gás e sim um painel elétrico cerâmico, recentemente pintado com esmalte sintético. A suspensão do uso do painel normalizou o COHb. O CO produto da decomposição térmica do esmalte sintético explica a causa da intoxicação.

Assessment of worker chemical exposures in California vape shops.

E-cigarettes are battery-operated devices that heat a liquid mixture to make an aerosol that is inhaled, or vaped, by the user. Vape shops are retail environments designed to fulfill customer demand for diverse e-liquid flavors and hardware options, which create unique worker exposure concerns. To characterize exposures to vape shop workers, especially to flavoring chemicals associated with known respiratory toxicity, this study recruited vape shops from the San Francisco Bay Area. In six shops, we measured air concentrations for volatile organic compounds, formaldehyde, flavoring chemicals, and nicotine in personal and/or area samples; analyzed components of e-liquids vaped during field visits; and assessed metals on surface wipe samples. Interviews and observations were conducted over the course of a workday in the same six shops and interviews were performed in an additional six where sampling was not conducted. Detections of the alpha-diketone butter flavoring chemicals diacetyl and/or 2,3-pentanedione were common: in the headspace of purchased e-liquids (18 of 26 samples), in personal air samples (5 of 16), and in area air samples (2 of 6 shops). Two exceedances of recommended exposure limits for 2,3-pentanedione (a short-term exposure limit and an 8-hr time-weighted average) were measured in personal air samples. Other compounds detected in the area and personal air samples included substitutes for diacetyl and 2,3-pentanedione (acetoin and 2,3-hexanedione) and compounds that may be contaminants or impurities. Furthermore, a large variety (82) of other flavoring chemicals were detected in area air samples. None of the 12 shops interviewed had a health and safety program. Six shops reported no use of any personal protective equipment (PPE) (e.g., gloves, chemical resistant aprons, eye protection) and the others stated occasional use; however, no PPE use was observed during any field investigation day. Recommendations were provided to shops that included making improvements to ventilation, hygiene, use of personal protective equipment, and, if possible, avoidance of products containing the alpha-diketone flavoring chemicals. Future research is needed to evaluate the long-term health risks among workers in the vape shop retail industry and for e-cigarette use generally. Specific areas include further characterizing e-liquid constituents and emissions, evaluating ingredient health risks, evaluating the contributions of different routes of exposure (dermal, inhalation, and ingestion), and determining effective exposure mitigation measures.

Derivation of occupational exposure limits: Differences in methods and protection levels.

Frameworks for deriving occupational exposure limits (OELs) and OEL-analogue values (such as derived-no-effect levels [DNELs]) in various regulatory areas in the EU and at national level in Germany were analysed. Reasons for differences between frameworks and possible means of improving transparency and harmonisation were identified. Differences between assessment factors used for deriving exposure limits proved to be one important reason for diverging numerical values. Distributions for exposure time, interspecies and intraspecies extrapolation were combined by probabilistic methods and compared with default values of assessment factors used in the various OEL frameworks in order to investigate protection levels. In a subchronic inhalation study showing local effects in the respiratory tract, the probability that assessment factors were sufficiently high to protect 99% and 95% of the target population (workers) from adverse effects varied considerably from 9% to 71% and 17% to 87%, respectively, between the frameworks. All steps of the derivation process, including the uncertainty associated with the point of departure (POD), were further analysed with two examples of full probabilistic assessments. It is proposed that benchmark modelling should be the method of choice for deriving PODs and that all OEL frameworks should provide detailed guidance documents and clearly define their protection goals by stating the proportion of the exposed population the OEL aims to cover and the probability with which they intend to provide protection from adverse effects. Harmonisation can be achieved by agreeing on the way to perform the methodological steps for deriving OELs and on common protection goals.

Exploring Localized Muscle Fatigue Responses at Current Upper-Extremity Ergonomics Threshold Limit Values.

OBJECTIVE: The purpose of this study was to evaluate localized muscle fatigue responses at three upper-extremity ergonomics threshold limit value (TLV) duty cycles. BACKGROUND: Recently, a TLV equation was published to help mitigate excessive development of localized muscle fatigue in repetitive upper limb tasks. This equation predicts acceptable levels of maximal voluntary contraction (% MVC) for a given duty cycle (DC). Experimental validation of this TLV curve has not yet been reported, which can help guide utilization by practitioners. METHOD: Eighteen participants performed intermittent isometric elbow flexion efforts, in three separate counter-balanced sessions, at workloads defined by the American Conference of Governmental Industrial Hygenists' (ACGIH) TLV equation: low DC (20% DC, 29.6% MVC), medium DC (40% DC, 19.7% MVC), and high DC (60% DC, 13.9% MVC). Targeted localized muscle fatigue (LMF) of the biceps brachii was tracked across numerous response variables, including decline in strength (MVC), electromyography (EMG) amplitude and mean power frequency (MnPF), and several psychophysical ratings. RESULTS: At task completion, biceps MnPF and MVC (strength) were significantly different between each TLV workload, with the high DC condition eliciting the largest declines in MnPF and MVC. CONCLUSION: Findings demonstrate that working at different DCs along the ACGIH TLV curve may not be equivalent in preventing excessive LMF. Higher DC workloads elicited a greater LMF response across several response variables. APPLICATION: High DC work of the upper extremity should be avoided to mitigate excess LMF development. Current TLVs for repetitive upper-extremity work may overestimate acceptable relative contraction thresholds, particularly at higher duty cycles.

[Methodology to evaluate occupational exposure to chemical contaminants at high altitude]. / Metodología para evaluar la exposición ocupacional a contaminantes químicos en altitud.

This study reviews the current method for assessing exposure to chemical contaminants at high altitude, which is based on the use of Threshold Limit Values (TLV). These TLVs were originally established for work performed at sea level, for 8-hour shifts over a 40-hour work week. Our study analyzes the problem for a specific group of Chilean miners working at altitudes above 3000, and for shifts of up to 12 hours a day. We examined different approaches for the evaluation of exposure to chemical contaminants: adjusting the TLV for work at high altitude and calculating inhaled dose. Since minute ventilation changes at different altitudes, we propose using calculated inhaled dose of the chemical contaminant as the method of choice.

Este artículo examina el actual método para evaluar la exposición a contaminantes químicos en altitud usando los Threshold Limit Value (TLV). Estos valores son establecidos para trabajos a nivel del mar en jornadas de 8 horas diarias y 40 horas semanales. Se analiza este problema aplicándolo a un grupo específico de mineros chilenos que trabaja sobre los 3000 m con jornadas excepcionales de 12 horas diarias. Se comparan dos alternativas para evaluar la exposición a contaminantes químicos: ajustes al TLV en altitud, y el cálculo de la dosis inhalada. Puesto que la ventilación por minuto es el parámetro fisiológico que cambia en altitud se propone y fundamenta como método de evaluación el cálculo de la dosis inhalada del contaminante químico.

Metodología para evaluar el nivel de protección respiratoria de mascarillas y respiradores ante partículas similares a las que transmiten el SARS-CoV-2 / Methodology for evaluating the level of respiratory protection of masks and respirators against particles similar to those that transmit SARS-CoV-2

RESUMEN Objetivo: Desarrollar una metodología para evaluar el nivel de protección respiratoria de respiradores, mascarillas quirúrgicas y mascarillas comunitarias que usa la población peruana, usando partículas de un tamaño similar a las que contienen al virus activo del SARS-CoV-2. Materiales y métodos: Se ha determinado una relación lineal directa entre el logaritmo de la concentración de partículas suspendidas en aire y el tiempo transcurrido; por lo cual es posible comparar la cantidad de partículas internas y externas a la mascarilla o respirador en un mismo periodo y conocer el porcentaje de protección respiratoria de cada muestra evaluada. Resultados: Se ha logrado implementar una metodología para evaluar el nivel de protección respiratoria ante aerosoles menores a 5,0 µm. Asimismo, el empleo de accesorios como ligas o ajustadores detrás de cabeza y nuca, y el uso de clips nasales robustos, incrementan significativamente el nivel de protección respiratoria ante partículas con alta probabilidad de contener al SARS-CoV-2. Conclusiones: Se observa una concordancia entre los valores de protección respiratoria obtenidos y los esperados, considerando el nivel de filtración del material empleado de cada mascarilla quirúrgica o respirador, y su nivel de ajuste. Se observó un incremento significativo en los niveles de protección respiratoria.

ABSTRACT Objective: To develop a methodology for evaluating the level of respiratory protection provided by respirators, surgical masks and community face masks used by the Peruvian population; protection was evaluated against particles of a size similar to those containing active SARS-CoV-2 virus. Materials and methods: A direct linear relationship has been determined between the logarithm of the concentration of airborne particles and the elapsed time; thus, it is possible to compare the quantity of particles inside and outside of the mask or respirator in the same time period, as well as to obtain the percentage of respiratory protection for each evaluated sample. Results: A methodology was established to evaluate the level of respiratory protection against aerosols smaller than 5.0 μm. Also, the use of accessories such as rubber bands or adjusters behind the head and neck, and the use of robust nasal clips, significantly increased the level of respiratory protection against particles with a high probability of containing SARS-CoV-2. Conclusions: We found concordance between the obtained respiratory protection values and those expected, considering the filtration level of the material used for each surgical mask or respirator, as well as the tightness. A significant increase in the levels of respiratory protection was observed.

Characterization of Airborne Particulates and Worker Exposures in Electro-static Powder Coating Operations.

This study was to examine the airborne particulates/dusts and worker exposures in electro-static powder coating operations. Temporal variation and size distribution of dusts were assessed using direct-reading instrument, while the worker task-specific dust exposures (n = 41) were measured in three factories using conventional filter method. Additionally, toxic metal levels in the coating powder (n = 27) were analyzed to assess hazard potentials. Continuous monitoring of airborne respirable dust levels indicated large temporal variation across a normal working day. The particulate levels outside spraying booths were generally low (below 0.10 mg m-3) during normal spraying operation, but short-term level may reach as high as 21.8 mg m-3 (averaged at 4-5 mg m-3) when specific task such as cleaning the pipelines and spraying booth, was performed. Exploratory assessment on particle size distribution at four major working zones, administration, uploading, spraying, and baking, indicated no major difference among the zones, and between factories. The particle count median aerodynamic diameter was 0.88-1.69 µm, while the mean number concentrations were 10.97, 15.17, 18.49, and 27.03 (# cm-3) for zones administration, uploading, spraying, and baking, respectively. The worker task-specific dust exposures were found low during normal spraying, with the mean short-term total and respirable dust concentrations being 0.88 and 0.41 mg m-3, respectively. Both levels increased to 3.48 and 5.19 mg m-3, respectively (P < 0.05), if powder changing and system cleaning were done. Short-term total and respirable dust concentrations were 94.2 and 56.1 mg m-3, respectively, when complete cleaning process was performed inside spraying booth. Both levels exceeded the short-term exposure limits. The mean concentration of metals in the powder samples were 6.78, 9.52, 10 717, 2805, 1020, and 1361 µg g-1 for Pb, Cr (total), Al, Fe, Cu, and Sr, respectively. This study demonstrated that cleaning of spraying booth resulted in high dust exposures well exceeding the exposure limit. Toxic metals, particularly Pb, Cd, and Cr (total), levels measured in the powder samples were found low, and the resulting exposures were below the exposure limits, indicating relative low risks associated with the exposure at current dust levels.

Características operativas de la regla de predicción STePS, para desenlaces graves a corto plazo en pacientes con síncope / Operative characteristics of the STePS prediction rule for short-term serious outcomes in patients with syncope

Resumen Introducción: el síncope es una entidad clínica frecuente en urgencias con un pronóstico variable que depende de su etiología. El estudio STePS identificó cuatro variables que se asociaron independientemente con desenlaces graves a 10 días. El objetivo del estudio fue evaluar su rendimiento en una población de pacientes que acuden al servicio de urgencias por síncope. Metodología: estudio prospectivo observacional de pacientes que consultaron a urgencias del Hospital Universitario Clínica San Rafael con diagnóstico de síncope. Se realizó un análisis descriptivo de las variables demográficas y clínicas de la población, y un análisis comparativo según el ingreso o no a UCI. Se analizaron las variables cualitativas y cuantitativas por medio de prueba de chi cuadrado y t student respectivamente. Las características operativas de la regla STePS fueron evaluadas en una gráfica considerándose como aceptable un área bajo la curva (AUC) mayor a 0.8 y como óptima un AUC mayor a 0.9. Resultados: se incluyeron 98 pacientes. El rendimiento de la regla de predicción STePS fue AUC-ROC 0.64 (IC95%; 0.53-0.75). Sólo el electrocardiograma anormal (OR 13.98, IC 95% 1.29151.9) y trauma concomitante (OR 5.22, IC 95% 1.20-22.67) demostraron ser factores de riesgo para desenlaces graves a 10 días. Se identificaron factores prevalentes en la población con ingreso a UCI: edad >65 años (p=0.02), antecedente de falla cardiaca (p=0.047), enfermedad renal crónica (p=0.002) y cardiopatía (p=0.01). Conclusión: la regla de predicción STePS no tuvo un rendimiento favorable para predicción de desenlaces graves a 10 días del evento sincopal en esta población estudiada.

Abstract Introduction: syncope is a common clinical condition in the emergency room with a variable prognosis depending on its etiology. The STePS study identified four variables which were independently related to serious outcomes within 10 days. The objective of the study was to evaluate its performance in a population of patients seen in the emergency room for syncope. Methods: a prospective observational study of patients seen in the emergency room of the Hospital Universitario Clínica San Rafael with a diagnosis of syncope. A descriptive analysis of the population's demographic and clinical variables was conducted, along with a comparative analysis according to admission or non-admission to the ICU. Qualitative and quantitative variables were analyzed using Chi-square or Student's t test, respectively. The operative characteristics of the STePS rule were evaluated in a graph, with an area under the curve (AUC) greater than 0.8 considered to be acceptable, and greater than 0.9 considered to be optimal. Results: Ninety-eight patients were included. The performance of the STePS prediction rule was AUC-ROC 0.64 (95% CI; 0.53-0.75). Only an abnormal electrocardiogram (OR 13.98, 95% CI 1.29-151.9) and concomitant trauma (OR 5.22, 95% CI 1.20-22.67) proved to be risk factors for serious outcomes within 10 days. Prevalent factors in the population admitted to the ICU were: age >65 years (p=0.02), a history of heart failure (p=0.047), chronic kidney disease (p=0.002) and heart disease (p=0.01). Conclusion: the STePS prediction rule did not perform favorably for predicting serious outcomes within 10 days of the syncopal event in this study population.