Exposure Limits Research Articles

Recommendations for the Safe Application of Temporal Interference Stimulation in the Human Brain Part II: Biophysics, Dosimetry, and Safety Recommendations.

Temporal interference stimulation (TIS) is a new form of transcranial electrical stimulation (tES) that has been proposed as a method for targeted, noninvasive stimulation of deep brain structures. While TIS holds promise for a variety of clinical and nonclinical applications, little data is yet available regarding its effects in humans and its mechanisms of action. To inform the design and safe conduct of experiments involving TIS, researchers require quantitative guidance regarding safe exposure limits and other safety considerations. To this end, we undertook a two-part effort to determine frequency-dependent thresholds for applied currents below which TIS is unlikely to pose risk to humans in terms of heating or unwanted stimulation. In Part II of this effort, described here, we draw on a previously compiled list (see Part I) of adverse effects (AEs) reported for transcranial direct/alternating current stimulation (tDCS/ACS), deep brain stimulation (DBS), and TIS to determine biophysics-informed exposure metrics for assessing safety. Using an in silico approach, we conduct multiphysics simulations of various tACS, DBS, and TIS exposure scenarios in an anatomically detailed head and brain model. By matching the stimulation in terms of the identified exposure metrics, we infer frequency-dependent TIS parameters that produce exposure conditions equivalent to those known to be safe for tACS and DBS. Based on the results of our simulations and existing knowledge regarding tES and DBS safety, we propose frequency-dependent thresholds below which TIS voltages and currents are unlikely to pose a risk to humans. Safety-related data from ongoing and future human studies are required to verify and refine the thresholds proposed here.

Recommended Occupational Exposure Limits for GMA Using Benchmark Dose and Bayesian Model Averaging.

Glycidyl methacrylate (GMA) is a widely used industrial polymerization material. Current occupational exposure limits (OELs) for GMA in China show significant disparities compared to those established by international regulatory bodies, including the United States, the European Union, and Japan. A comprehensive revision of GMA exposure limits is crucial for ensuring optimal worker protection. This investigation analyzed data from a 104-week inhalation carcinogenicity study of GMA in mice conducted in Japan. This study identified statistically significant pathological endpoints and employed benchmark dose (BMD) analysis to evaluate meaningful endpoints, focusing on those with the lowest benchmark dose lower bound values. The final recommendations were optimized using Bayesian model averaging (BMA) methodology to establish appropriate OELs. Our analysis recommends a time-weighted average allowable concentration of 0.01 ppm for GMA, which aligns with international standards established by the European Chemicals Agency (0.016 ppm), Japan Society for Occupational Health (0.012 ppm), and American Conference of Governmental Industrial Hygienists (0.01 ppm). The combined application of BMD and BMA methodologies represents a scientifically robust approach for deriving points of departure in risk assessment. These evidence-based OELs are essential for effective occupational hazard management and worker health protection.

Collaborative Learning Strategy for Better Reading Comprehension in EFL University Courses

This study investigates the impact of collaborative learning strategy on the reading comprehension of non-English department students at the university level. An effective reading comprehension not only talk about the ability to understanding the text, but also the capacity to interpret meaning and synthesize information from different text genre. Moreover, for the non-English department students who generally have different language competence with English department students, they often encounter a difficult situation in reading activity because of their limitation in language exposure. Using a mixed-method approach, this study combines quantitative data from reading tests with qualitative insights from student interviews and classroom observations. Over one semester, students from various non-English department participated in collaborative activities, such as collaborative strategic reading and group discussions, designed to improve critical thinking and collaborative problem-solving. The quantitative results demonstrate significant improvements in reading comprehension, particularly in identifying main ideas, making inferences, and understanding vocabulary in context. Qualitative findings reveal that students found the collaborative learning environment is enjoyable and motivating, with many reporting that collaborative learning reduced their anxiety and enhanced their willingness to participate actively. This study highlights the effectiveness of collaborative learning strategy in improving reading comprehension among non-English department students and offers practical recommendations for integrating these strategies into diverse academic disciplines.Keywords: Collaborative Learning, Reading Comprehension, EFL, Non-English Department Student

A Content Analysis of Web-Based Heat Stress Materials Published by Occupational Health and Safety Ministries, Associations, and Agencies in Canada.

An ever-increasing number of workplaces are becoming heat-exposed due to rising temperature extremes. However, a comprehensive review of Canadian safety materials available to support workplaces in managing this critical hazard has not previously been conducted. We undertook a review and a content analysis of heat stress materials on safety-based ministry, association, and agency websites in Canada (n = 155) to identify content related to heat stress (n = 595). Each document was qualitatively analyzed using NVivo. The most dominant components identified were heat stress control measures (n = 492, 83%), training and education (n = 414, 70%), workplaces and workers at risk (n = 361, 61%), exposure limits and monitoring practices (n = 344, 58%), and emergency response and reporting (n = 249, 42%). However, the content within these programming components was highly variable. While we found that organizations across Canada provide heat stress content, there was evidence of inconsistencies and considerable gaps in the availability of material and the strategies presented to control the critical risk posed by heat.

Enhancing Amperometric Ozone Gas Sensing with Room-Temperature Ionic Liquids and Platinum-Based Electrodes.

Ozone (O3) poses serious health risks, prompting numerous countries to implement regulations that establish exposure limits and emission controls, for example, the air quality index (AQI) for O3 ranging from 50 to 150 parts per billion (ppb), with natural levels at around 30 ppb. Electrochemical sensors are favored for detecting pollutant gases due to their high sensitivity, low cost, portability, energy efficiency, and capability for selective detection. In this study, we developed an O3 sensor employing carbon-supported Pt-based binary and ternary nanorods (NRs) combined with room-temperature ionic liquids (RTILs) as electrolytes, aiming at highly sensitive and selective detection of O3 at ppb levels. Initial screening of the O3 sensing performance across different electrolytes identified H2SO4 and [C4mpyrr][NTf2] (BMP) as the most sensitive options. BMP outperformed H2SO4 in terms of linearity, selectivity, reproducibility, and response/recovery times, despite a relatively lower sensitivity. Electrochemical testing of Pt, PtAu, PtAg, and PtAuAg NR electrodes in BMP revealed that the addition of Au enhanced the linear response, while Ag improved sensitivity. Consequently, the ternary PtAuAg NR electrode exhibited the highest sensitivity (10.5 nA/ppm (parts per million)) and a broad detection range, fulfilling the AQI requirements for O3. The current response from the PtAuAg NR electrode closely aligned with results from an ultraviolet (UV) photometric analyzer, confirming its accuracy. Notably, this electrode contains only 20 wt % noble metals, which reduces the overall cost to just 11% of that of a traditional pure Au electrode.

Evaluating sublethal anticoagulant rodenticide exposure in deceased predatory birds of South-East Queensland, Australia

The use of anticoagulant rodenticides (ARs) to manage rodent populations can result in unintentional lethal or sublethal poisoning of non-target wildlife, particularly predatory birds. In south-east Queensland, Australia, rodent infestations fluctuate due to favourable environmental conditions, leading to increased AR use and incidences of secondary poisoning. Globally, lethal and sublethal AR exposure has been documented in predatory birds. However, in Australian predatory birds, both the lethal exposure limits and the impacts of sublethal exposure are poorly understood. This study examines AR exposure in 23 raptors and 1 nightjar. Postmortem liver samples were analysed using liquid chromatography mass spectrometry (LC–MS). Traumatic injuries were observed in 15 birds, and rodent remains were found in the gizzards of 9 individuals. LC–MS revealed that 13 birds had sublethal exposure to ARs, with warfarin, a first-generation AR (n = 11) being the most common, followed by second-generation ARs brodifacoum (n = 3), difethialone (n = 1), and flocoumafen (n = 1). Only six of the thirteen AR-positive birds had rodent remains in their gastrointestinal tracts, highlighting the potential of AR bioaccumulation and associated impacts over time. The contribution of sublethal AR exposure to the death of these predatory birds remains unproven and underscores the need for ongoing research into AR exposure in native predatory birds, especially in areas where threatened avifauna inhabit human-dominated landscapes.

Sensitive and Discriminative Fluorescent Detection of Volatile Primary Aliphatic Diamine Vapors from Monoamines.

The discriminative detection of volatile primary aliphatic diamines (VPADs) is a relevant and timely issue. This paper explores the distinctive optical features of H-type and J-type aggregates on paper-based (PB) films, namely H-PB and J-PB films, respectively, of a Lewis acidic Zn(salen)-type complex upon chemisorption of vapors of ditopic VPADs versus those of monotopic volatile amines. While volatile monotopic Lewis bases upon chemisorption give rise to mono-adducts accompanied by enhancement of the fluorescence, in contrast, VPADs act as ditopic bases forming di-adducts with distinct optical properties, leading to fluorescence quenching. This behavior enables the sensitive and discriminative detection of VPAD vapors from those of volatile monoamines. For example, for ethylenediamine (EDA), using J-PB films, sensitive detection is achieved with a LOD down to 6.6 ppm, lower than the OSHA permissible exposure limit of 10 ppm for EDA, and a linear dynamic range up to 100 ppm. Instead, H-PB films enable the detection of EDA vapors at higher ppm concentrations (up to 3000 ppm) with a linearity of up to 1000 ppm. Thus, the combination of both H-PB and J-PB films of the Zn(salen)-type complex represents a unique example of the sensitive and discriminative detection of EDA vapors in such a wide concentration range.

Assessment of the Influence of Safety Training on the Technicians Safety Culture in the Pharmaceutical Manufacturing Industries in Kenya

<i>Introduction:</i> Technicians in pharmaceutical manufacturing industries work in a high risk occupational setting. They are routinely exposed to chemical hazards due to the nature of their work. In order for them to perform, safety is paramount. This research intended to assess the influence of safety culture of technicians in pharmaceutical manufacturing industries. <i>Methods:</i> In order to achieve the objective, descriptive survey research design was used. Purposive sampling was used to select ten pharmaceutical Manufacturing industries which formed the research sample. Data was collected through questionnaires. The collected data was subjected to quantitative and qualitative analysis by use of SPSS. The<i> results</i> showed that the safety maturity level of 85% of the PMI’s were continually improving safety maturity level and only 15% in the involving safety maturity level. This was based on an analysis of the safety culture in four key dimensions. The study also established that majority of the respondents at 75.4% had their first encounter with OSH training at work environment commonly referred to as On the Job Training and only 23.3% were trained during their academic/professional education. The findings show that the majority of the respondents; 89.0 % and 80.8% of the respondents had been trained on the requirements of OSH Act 2007 and Evacuation procedures respectively. Notably, the training area with the least awareness was Exposure Limits of hazardous chemicals and substances at 29.1% across all PMI’s. The p values for OSH Training and Safe work documentation are p<0.001 and 0.421 respectively, indicating that OSH training is a statistically significant predictor of safety Culture. <i>Conclusion:</i> The hypothesis, there is statistically significant influence of training on safety culture of technicians among pharmaceutical manufacturing industries in Kenya, was accepted. Therefore we can conclude that OSH training has a significant positive influence on safety culture in pharmaceutical manufacturing industries in Nairobi, Kenya. The study therefore recommends that there is need to incorporate an OSH competency in the professional training of potential employees in the PMI’s in Kenya. This will enhance awareness of hazards and shape attitudes towards safety, well in advance hence enhance the safety culture maturity levels. The government thought the Ministry Of Labour And Social protection should ensure frameworks are able to enforce the implementation of OSHA (2007) training requirements to fill the gap in the training topic on handling of hazardous chemicals for workers in the PMI’s.

Occupational exposure to respirable crystalline silica at an underground copper mine in Zambia.

Overexposure to respirable crystalline silica (RCS) can lead to the development of silicosis and other respiratory diseases. The mine under study was reported to have the highest number of certified cases of pneumoconiosis in Zambia in 2015, and in 2008, a study revealed that 56% of the RCS samples exceeded 0.05mg/m3. This study aims to assess occupational exposure to RCS at this underground copper mine. In this cross-sectional study, personal exposure monitoring was conducted using National Institute for Occupational Safety and Health's methods 0600 and 7602 (KBr pellet), and 114 samples were collected. Gravimetric analysis of respirable dust (RD) samples and quantification of RCS were performed at an ISO 17025:2005 accredited analytical laboratory. BOHS-NVvA 2022 standard was used for determining activity areas' overexposure. The median, 95th percentile (P95), and maximum (Max) RD concentrations were 0.279, 1.650, and 3.7mg/m3, respectively. For the RCS exposure, the median, P95, and Max RCS exposure concentrations were 0.02, 0.179, and 0.548mg/m3, respectively. Thirteen (11.7%) of the 111 samples had exposure exceeding the Republic of South Africa (RSA) TWA-OEL of 0.1mg/m3, and 11 out of 18 activity areas were statistically overexposed to RCS when applying the BOHS-NVvA 2022 standard. The number of RCS samples exceeding 0.05mg/m3 reduced from the 67% recorded in 2008 to 32.4% in this study. One factor that could have led to this reduction is the mine not working at full capacity during the sampling period. However, the lack of adherence to the occupational health and safety (OHS) guidelines by the miners still leads to personal exposure above the limits set by various countries. Exposure to RCS in more than half of the activity areas was not under control. Routine RCS monitoring in Zambian mines should be mandatory, as this is not an isolated case, though it is more of a challenge at this mine because of the high percentage of RCS in RD samples (18.5%). Miners should be continuously trained on the importance of adhering to the OHS guidelines. Furthermore, Zambia should consider adopting the RSA occupational exposure limit for RCS and the BOHS-NVvA 2022 standard for exposure level compliance testing.

Respiratory quaternary ammonium and volatile organic compound exposures experienced by home care aides during residential bathroom cleaning using conventional and green products.

US home care (HC) aide visits to clients' homes typically involve cleaning and disinfecting (C&D) environmental surfaces, particularly in bathrooms. Some ingredients in C&D products are associated with respiratory illness: sodium hypochlorite (bleach), quaternary ammonium compounds (QACs), and volatile organic compounds (VOCs). This study assessed and compared aides' respiratory exposures to specific VOCs and QACs while using 2 conventional and 1 "green" household C&D spray products during bathroom cleaning. Measured exposures were compared to ingredients listed on publicly available sources. Three C&D products were selected with principal active disinfecting ingredients: 1% to 5% sodium hypochlorite by weight ("bleach-based"); 0.1% to 1% QACs ("QACs-based"); and 0.05% thymol ("green"). Twenty-two aides were recruited to perform C&D tasks in a simulated residential bathroom constructed in an environmental monitoring laboratory. A balanced experimental study design involved each aide visiting the lab 4 times to perform typical cleaning tasks with the 3 products and distilled water (as a control), randomly assigned across the 4 visits. Aides wore air sampling equipment for breathing zone samples: canisters to collect whole air for VOC analyses and filter cassettes for QACs analyses. Aides performed 84 cleaning visits contributing approximately 20 air samples each for VOCs and QACs, for each of the 3 products and distilled water. In total, 38 unique VOCs were identified in the canister whole air samples: 20 in the QACs-based product samples, 15 in the bleach-based, and 10 in the green. Most VOCs were not listed in publicly available sources of cleaning product ingredients. Toxicity information was limited. Few VOCs had occupational exposure limits. The QACs-based product generated QACs aerosol: benzalkonium chloride (BAC)12 (geometric mean (GM) = 6.98 µg/m3), BAC14 (GM=2.97 µg/m3), BAC16 (GM=0.78 µg/m3); and the 3 QACs summed (GM=10.86 µg/m3). The use of C&D spray products for residential cleaning can generate respiratory exposures to complex mixtures of volatile and nonvolatile compounds. Notably, we measured aerosols containing QACs during the use of the QACs-based product. Dermal is usually considered the main route of exposure because QACs are nonvolatile salts. This study provides evidence that QACs inhalation exposure should be recognized and minimized in addition to the well-accepted dermal exposure routes. The green product generated the fewest VOCs. However, more toxicity information is needed on the health impacts of green C&D products. Spraying of C&D products, conventional and green, should be avoided. Aides' respiratory health should be protected from chemical exposures while performing C&D in home care.

Improving Monitoring of Indoor RF-EMF Exposure Using IoT-Embedded Sensors and Kriging Techniques.

Distributed wireless sensor networks (WSNs) are widely used to enhance the quality and safety of various applications. These networks consist of numerous sensor nodes, often deployed in challenging terrains where maintenance is difficult. Efficient monitoring approaches are essential to maximize the functionality and lifespan of each sensor node, thereby improving the overall performance of the WSN. In this study, we propose a method to efficiently monitor radiofrequency electromagnetic fields (RF-EMF) exposure using WSNs. Our approach leverages sensor nodes to provide real-time measurements, ensuring accurate and timely data collection. With the increasing prevalence of wireless communication systems, assessing RF-EMF exposure has become crucial due to public health concerns. Since individuals spend over 70% of their time indoors, it is vital to evaluate indoor RF-EMF exposure. However, this task is complicated by the complex indoor environments, furniture arrangements, temporal variability of exposure, numerous obstructions with unknown dielectric properties, and uncontrolled factors such as people's movements and the random positioning of furniture and doors. To address these challenges, we employ a sensor network to monitor RF-EMF exposure limits using embedded sensors. By integrating Internet of Things-embedded sensors with advanced modeling techniques, such as kriging, we characterize and model indoor RF-EMF downlink (DL) exposure effectively. Measurements taken in several buildings within a few hundred meters of base stations equipped with multiple cellular antennas (2G, 3G, 4G, and 5G) demonstrate that the kriging technique using the spherical model provides superior RF-EMF prediction compared with the exponential model. Using the spherical model, we constructed a high-resolution coverage map for the entire corridor, showcasing the effectiveness of our approach.

Transoral Robotic Posterior Glottic Scar Lysis and Partial Arytenoidectomy: Report of a Novel Application of TORS for Benign Glottic Surgery.

Transoral robotic surgery (TORS) for benign glottic conditions is scarcely represented in the literature. We aimed in this study to report on the technical feasibility of an explicitly transoral robotic approach for a patient with posterior glottic stenosis, and to highlight extant limitations in exposure and robotic instrumentation of the glottis. Retrospective chart review of a single patient undergoing a TORS approach to maximize the posterior glottic aperture. A 42-year-old female patient with posterior glottic stenosis and a tracheotomy was consented for a robotic posterior glottic scar lysis, KTP-laser assisted partial arytenoidectomy, balloon dilation, and steroid injection. The da Vinci Intuitive Surgical single-port robotic platform was used with 2 robotic arms (needle driver and scissors), and an FK-WO transoral retractor with a straight tongue blade was deployed to facilitate endolaryngeal exposure. KTP laser fiber was passed through a robotic, semi-flexible drop-in guide, and manipulated with the needle driver. Case duration was 40 minutes. There were no perioperative or immediate post-operative complications noted on short-term follow-up. We demonstrate technical feasibility and equipoise between an explicitly robotic approach and a standard endoscopic approach to posterior glottic stenosis, a common glottic condition. Further technological development and adaptation of surgical technique are necessary to advance benign robotic laryngeal surgery.

Recent trends in respirable crystalline silica and elemental carbon exposure in the Ontario, Canada mining industry.

Mining is a high-hazard industry with significant occupational disease risks. Despite this there is limited data describing current exposure conditions. The aim of this short communication is to share recent exposure data from underground mines in Ontario, Canada. Data from underground mines were accessed through a freedom of information request. Data were cleaned and standardized. Data contained measurements of several hazards from 2013 to 2018; analysis focused on personal samples for respirable crystalline silica (RCS) and elemental carbon (EC) from 2014 to 2018. Descriptive statistics were calculated overall and by sampling year; comparisons were made to current occupational exposure limits. Linear regression models were constructed to examine time trends. EC exposures decreased significantly, ~10% per year over the measurement period (2014 to 2018). Overall 14% of EC measurements were above the current mining exposure limit (0.12mg/m3 EC) in Ontario, Canada. Results for silica did not show a statistically significant trend but did suggest a reduction of ~1.8% per year. Almost one-third of the RCS measurements were above the American Conference of Governmental Industrial Hygienists (ACGIH) recommended threshold (0.025mg/m3). Current exposure data is needed to understand workers' exposure and support occupational disease prevention. Recent data from the Ontario mining industry suggests that exposure to elemental carbon decreased significantly from 2014 to 2018, but the annual reduction for silica exposure was not nearly as substantial. Mining workers continue to be exposed to levels of EC and RCS that are hazardous to health.

Wavelength-Dependent DNA Damage Induced by Single Wavelengths of UVC Light (215 to 255 nm) in a Human Cornea Model.

Scientific bodies overseeing UV radiation protection recommend safety limits for exposure to ultraviolet light in the workplace based on published peer-reviewed data. To support this goal, a 3D model of the human cornea was used to assess the wavelength dependence of corneal damage induced by UVC light. In the first set of experiments the models were exposed with or without simulated tears; at each wavelength (215-255 nm) cells with DNA dimers and their distribution within the epithelium were measured. Simulated tears reduced the fraction of damaged cells to an extent dependent on the wavelength and tissue layer. Another set of models were exposed without tears; yields of DNA-damaged cells and their distribution within the corneal epithelium were evaluated at each wavelength, together with other markers of cell and tissue integrity. Unlike relatively longer wavelengths, the range commonly referred to as far-UVC (215-235 nm) only induced dimers in the uppermost layers of the epithelium and did not result in lasting damage or halt proliferation of the germinative cells. These results provide evidence for the recommended exposure limits for far-UVC wavelengths, which have been proposed as a practical technology to reduce the risk of transmission of airborne diseases in occupied locations.

Estimation of Radon activity in the nuclear security laboratory at the basement level of a building

Abstract Among all radiation exposure, the second leading cause of lung cancer is Radon while smoking is the primary contributor. The identification of the source and extent of Radon contamination is paramount for the formulation and implementation of measures aimed at reducing Radon levels in indoor spaces. Given the serious health implications, numerous countries and regions have implemented stringent Radon exposure limits and regulations to safeguard public health. The present work is to study the activity of 222Rn within a nuclear education laboratory. For the detection of gamma rays, a High-purity Germanium detector, with 34% relative efficiency and 0.6 mm carbon window was used. However, for the adsorption of Radon activity, 70 g charcoal in metal tin was employed. The spectrum was obtained using PROSPECT software and was calibrated using a 152Eu standard source. The analysis of the spectrum was done using CANDLE. The radionuclides 214Pb, 214Bi, and 40K which have gamma rays of 351keV, 609 keV, and 1460 keV, respectively are investigated. The measured activity of 222Rn radionuclide was found to be ranging between 9.77±0.73 Bq/Kg to14.00±1.00 Bq/Kg.

Establishment of a threshold of toxicological concern for pharmaceutical intermediates based on historical repeat-dose data and its application in setting health based exposure limits.

Availability of toxicological data for pharmaceutical intermediates (IMs) used in the manufacture of small molecules is often limited. Scarcity of data - in particular, repeat-dose toxicity (RDT) - renders the calculation of health-based exposure limits (HBELs) problematic. Establishment of HBELs, including occupational exposure limits (OELs) and permitted daily exposures (PDEs) facilitating worker and patient safety respectively, is however essential. Historic 28-day oral rodent toxicity data was analysed for 103 GSK isolated IMs. No-observed (adverse) effect levels (NO(A)ELs) and critical effects were extracted. The 5th percentile (p05) of the NO(A)EL distribution was 15mg/kg/day. Substance specific HBELs were calculated, selecting the NO(A)EL as the Point of Departure (PoD); 99% of IMs (n=102) were assigned an oral PDE ≥1000μg/day and OEL ≥100μg/m3. A default oral PDE of 1000μg/day and OEL of 100μg/m3 is thus proposed for IMs. Evaluation of an additional PoD - benchmark dose lower confidence limit (BMDL) - further supported the default HBELs. The default oral PDE can also serve as a threshold of toxicological concern (TTC) for IMs. Default limits can aid in setting HBELs for novel data-poor IMs, as well as supporting waiving of RDT in the future through read-across.

Associations between bioaerosols, lung function work-shift changes and inflammatory markers: A study of recycling workers.

We investigated associations between bioaerosol exposures and work-shift changes in lung function and inflammatory markers among recycling workers. Inhalable dust was measured with personal samplers and analyzed for endotoxin, bacteria, and fungi (incubated at 25 °C and 37 °C) levels. Lung function (FEV1, FVC) was measured before and after work-shifts and serum concentrations of inflammatory markers (CRP, SAA, CC16, IL1B, IL2, IL4, IL5, IL6, IL8, IL10, IL13, and TNF) after the shift. Associations were explored by linear mixed-effects models. We included 170 measurements from 88 production workers exposed to inhalable dust, endotoxin, bacteria, and fungi (25 °C and 37 °C) at geometric mean levels of 0.6 mg/m3, 10.7 EU/m3, 1.6×104 CFU/m3, 4.4×104 CFU/m3, and 103 CFU/m3, respectively, and 14 administrative workers exposed at 7-fold lower levels. No associations were observed between bioaerosol exposures and work-shift change in lung function. IL2, IL6, IL10, and TNF concentrations were positively associated with inhalable dust levels, SAA and IL6 with bacteria, CRP, SAA, IL8, and TNF with fungi (25 °C or 37 °C), with the latter being the only statistically significant finding (exp(β) 1.40, 95% confidence interval 1.01-1.96). This study of recycling workers exposed to bioaerosol levels generally below those of farmers and compost workers and above background levels did not indicate any acute effect on lung function. Several inflammatory markers tended to increase with exposure, suggesting a systemic effect. Future research should combine data from bioaerosol-exposed workers to uncover health risks that may form the basis for health-based occupational exposure limits.

Exposure assessment to fine and ultrafine particulate matter during welding activity in the maintenance shop of a steelmaking factory

Welding fumes are a main source of occupational exposure to particulate matter (PM), besides gases and ultraviolet radiations, that involves millions of operators worldwide and is related to several health effects, including lung cancer. Our study aims to evaluate the exposure to fine and ultrafine airborne particulate in welding operators working in a steel making factory.In October 2019, air monitoring was performed for four days in five different welding scenarios and in the external area of a steelmaking factory to assess the exposure to airborne particles, ultrafine (UFP) particulate and inhalable fraction, during welding activities. The airborne particles distribution as particle number and mass concentration were measured using a low-pressure electric impactor, model ELPI™ (range of sampling 0.006 μm and 10 μm), whereas the airborne inhalable fraction was collected by filtration, using the IOM Sampler selector.The particle concentration, i.e. the number of particles per cm3 (part/cm3) showed significantly higher exposure figures for nanoscale particles, especially for the fractions included in the last 4 stages sampled by ELPI (from 0.010 μm to 0.071 μm), the figure representing between 85 % and 91 % of the total, whereas for the last 7 stages (0.010 μm–0.314 μm), they represented from 98 % to 99 % of the total. The average figure was approximately 5.01 × 104 part/cm3, while the maximum average was 1.95 × 105 part/cm3 on TIG welding, with a peak of 1.52 × 107 parts/cm3. In terms of mass concentration, the levels of PM inhalable fraction ranged between 0.1 mg/m3 and 1.08 mg/m3.The results of the present study substantially confirm previous studies regarding the distributions in terms of number and mass of welding fumes for SMAW and TIG techniques on steel, the mass concentration levels resulting within the permissible exposure limits (PEL) indicated by OSHA regulations. The results highlighted the importance of the efficiency of localized aspiration systems and the need to apply prevention and protection measures despite the low levels of exposure measured in terms of mass. ConclusionOverall, The particle number concentrations showed an important contribution in the emission of UFP compared to background levels. The PM inhalable fraction was substantially contained within the PEL. Further studies are needed to better understand the chemical characterization of the particulate also considering further variables of the working process that could influence the levels of exposure to welding fumes.

Solar Ultraviolet Radiation Exposure Among Opencast Miners in Namibia with the Use of Electronic Dosimeters: A Feasibility Study.

Importance: The lack of information on exposure of opencast mineworkers to solar ultraviolet radiation, a group I carcinogen, was addressed. The feasibility of using electronic dosimeters in the determination of exposure to solar ultraviolet radiation was investigated. Objective: The objective of the study was to determine the feasibility of measuring the occupational exposure of opencast mineworkers to solar ultraviolet radiation using electronic dosimeters. Design: The study followed a cross‑sectional design. Setting: Measurements were carried out at two opencast diamond mining operations hereafter referred to as site A and B, located in the Karas region of Namibia. Participants: Workers from all four outdoor occupations (bedrock, engineering, metallurgy and security) were recruited to participate in the study. Measurements: The study was conducted over four days at each site during winter (site A: 28 June to 4 July 2018 and site B: 6-11 July 2018) in the Karas region of Namibia with 28 consenting workers taking part. The AlGaN photodiode‑based electronic dosimeters were worn above clothing on the dorsal wrists (one) and two placed on the horizontal, unshaded area from 08:00 to 16:00 for the measurement of personal and ambient solar ultraviolet radiation, respectively. Historical meteorological data for the measurement period were obtained from Solcast and Ozone Monitoring Instrument (OMI) NASA. Results: Overall, clear skies and surface reflectivity of 0.19 were observed for both study sites. The mean ultraviolet indices were 2.43 (0.06-4.51) and 2.24 (0.09-4.88) for site A and B, respectively. Findings of valid measurements from nine participants showed the mean total daily personal solar ultraviolet radiation exposure of 1.9 ± 1.0 (1.01-1.57) standard erythemal dose (SED) for site A and 3.4 ± 2.6 (3.39-7.28) SED for site B. Conclusions and Relevance: Personal solar ultraviolet radiation exposure above the occupational exposure limit (OEL) demonstrated the need to include the winter season in planning for protective measures for skin and eyes, since workers are at risk of excessive exposure to solar ultraviolet radiation.

Dosimetry as a Lagging Indicator of Occupational Exposure to Nitrous Oxide in Pediatric Sedation: A Collaborative Process Improvement Project With Industrial Hygiene.

Nitrous oxide (N2O) is commonly used in pediatric procedural sedation. It is an attractive option to facilitate intravenous line placement, as it does not extend sedation recovery from subsequently administered agents. Although debate exists regarding health consequences of occupational exposure now that scavenging of exhaled gases is common, cooperation of pediatric patients to maximize engineering controls is not guaranteed and can contribute to repeated exposure over the course of a clinician's career. There is no global consensus on personal exposure limits, but the National Institute for Occupational Safety and Health published U.S. guidelines. A dosimetry survey of our sedation team during a short N2O procedure for intravenous line placement exceeded the National Institute for Occupational Safety and Health Recommended Exposure Limit (REL) of 25 parts per million. We designed a process improvement initiative to reduce occupational exposure below the Recommended Exposure Limit on serial surveys. A continuous flow, titratable, full-face mask N2O delivery system with scavenging by a central vacuum connection was used. A retrospective chart review of N2O procedures performed before the initial dosimetry survey revealed practice trends in provider behavior during N2O administration. Initiation of N2O gas flow and maintenance of face mask seal on an uncooperative patient were identified as two sources of variability. Two-handed face-masking technique, initiation of N2O gas flow only after masking, and continued masking for 2 min of exhaled scavenging were standardized and socialized as best practices. Subsequent dosimetry surveys of the sedation team were coordinated by Industrial Hygiene. Pre- and post-intervention phases were 17 months each and included 92 and 201 N2O patients, respectively. Six dosimetry surveys occurred in the post phase. Intravenous line placement was the typical procedure surveyed. Dosimetry results for all team members during surveys 1-4 were below the REL, with 14 of 16 samples falling below the level of quantitation. Elevated dosimetry results in survey 5 prompted reevaluation of work practices and equipment. A loose component on the delivery system was discovered, corrected, and incorporated as a pre-procedure check. With no further changes to work practices, dosimetry results were below the REL for survey 6. We layered work practice changes atop engineering controls to reduce occupational exposure levels for medical team members. We utilized dosimetry as a lagging indicator, prompting frequent reassessments of our equipment and processes that we might not otherwise have performed. Pediatric sedation programs are encouraged to consider whether Industrial Hygiene resources might provide synergy to process improvement efforts with inhalational sedation agents.