Last data update: Apr 29, 2024. (Total: 46658 publications since 2009)
Records 1-30 (of 37 Records) |
Query Trace: Lee EG [original query] |
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Lung toxicity, deposition, and clearance of thermal spray coating particles with different metal profiles after inhalation in rats
Antonini JM , Kodali V , Meighan TG , McKinney W , Cumpston JL , Leonard HD , Cumpston JB , Friend S , Leonard SS , Andrews R , Zeidler-Erdely PC , Erdely A , Lee EG , Afshari AA . Nanotoxicology 2023 1-18 Thermal spray coating is a process in which molten metal is sprayed onto a surface. Little is known about the health effects associated with these aerosols. Sprague-Dawley rats were exposed to aerosols (25 mg/m(3) × 4 hr/d × 4 d) generated during thermal spray coating using different consumables [i.e. stainless-steel wire (PMET731), Ni-based wire (PMET885), Zn-based wire (PMET540)]. Control animals received air. Bronchoalveolar lavage was performed at 4 and 30 d post-exposure to assess lung toxicity. The particles were chain-like agglomerates and similar in size (310-378 nm). Inhalation of PMET885 aerosol caused a significant increase in lung injury and inflammation at both time points. Inhalation of PMET540 aerosol caused a slight but significant increase in lung toxicity at 4 but not 30 d. Exposure to PMET731 aerosol had no effect on lung toxicity. Overall, the lung responses were in the order: PMET885≫PMET540 >PMT731. Following a shorter exposure (25 mg/m(3) × 4 h/d × 1d), lung burdens of metals from the different aerosols were determined by ICP-AES at 0, 1, 4 and 30 d post-exposure. Zn was cleared from the lungs at the fastest rate with complete clearance by 4 d post-exposure. Ni, Cr, and Mn had similar rates of clearance as nearly half of the deposited metal was cleared by 4 d. A small but significant percentage of each of these metals persisted in the lungs at 30 d. The pulmonary clearance of Fe was difficult to assess because of inherently high levels of Fe in control lungs. |
Evaluation of Stoffenmanager and ART for estimating occupational inhalation exposures to volatile liquids
Lee EG . Ann Work Expo Health 2023 67 (3) 402-413 In practice, workers often handle the same chemical(s) of interest under different control measures (e.g. local ventilation, enclosed system) during a full shift. Stoffenmanager® allows users to predict either task-based or full-shift exposures. However, most previous studies evaluated the tool by comparing task-based exposures with measured exposures. Also, limited evaluation studies of the Advanced REACH Tool (ART) with the Bayesian approach (ART+B) are available, requiring additional evaluation studies. The performance of Stoffenmanager® and ART with and without the Bayesian approach was evaluated with measured full-shift exposures to volatile liquids in terms of accuracy, precision, and conservatism. Forty-two exposure situation scenarios (including 251 exposures), developed based on job tasks and chemicals handled during tasks from workplaces, were used to generate full-shift estimates. The estimates were then compared with measured exposures using various comparison methods. Overall, Stoffenmanager® appeared to be the most accurate among the testing tools, while ART+B was the most precise. The percentage of measured exposures exceeding the tools' 90th percentile estimates (%M>T) demonstrated that Stoffenmanager® (16%M>T) and ART+B (13%M>T) were more conservative than ART (41%M>T). When the 90% upper confidence limit of the 90th percentile estimate was considered, the level of conservatism changed from low (41%M>T) to medium (17%M>T) for ART and from medium (13%M>T) to high (0.8%M>T) for ART+B. The findings of this study indicate that no single tool would work for all ESs. Thus, it is recommended that users select a tool based on the performance results of three components (i.e. accuracy, precision, and conservatism), not depending on one or two components. The strength of this study is that the required tools' input parameters were obtained during the sample collection to minimize assumptions for many input parameters. In addition, unlike other previous studies, multiple subtasks, which happen often in workplaces, were incorporated in this study. Nevertheless, the present study did not cover all activities listed in the tools and was limited to volatile liquids, suggesting further studies cover other exposure categories (e.g. solid, metal) and diverse activities. |
In vivo and in vitro toxicity of a stainless-steel aerosol generated during thermal spray coating
Kodali V , Afshari A , Meighan T , McKinney W , Mazumder MHH , Majumder N , Cumpston JL , Leonard HD , Cumpston JB , Friend S , Leonard SS , Erdely A , Zeidler-Erdely PC , Hussain S , Lee EG , Antonini JM . Arch Toxicol 2022 96 (12) 3201-3217 Thermal spray coating is an industrial process in which molten metal is sprayed at high velocity onto a surface as a protective coating. An automated electric arc wire thermal spray coating aerosol generator and inhalation exposure system was developed to simulate an occupational exposure and, using this system, male Sprague-Dawley rats were exposed to stainless steel PMET720 aerosols at 25 mg/m(3) × 4 h/day × 9 day. Lung injury, inflammation, and cytokine alteration were determined. Resolution was assessed by evaluating these parameters at 1, 7, 14 and 28 d after exposure. The aerosols generated were also collected and characterized. Macrophages were exposed in vitro over a wide dose range (0-200 µg/ml) to determine cytotoxicity and to screen for known mechanisms of toxicity. Welding fumes were used as comparative particulate controls. In vivo lung damage, inflammation and alteration in cytokines were observed 1 day post exposure and this response resolved by day 7. Alveolar macrophages retained the particulates even after 28 day post-exposure. In line with the pulmonary toxicity findings, in vitro cytotoxicity and membrane damage in macrophages were observed only at the higher doses. Electron paramagnetic resonance showed in an acellular environment the particulate generated free radicals and a dose-dependent increase in intracellular oxidative stress and NF-kB/AP-1 activity was observed. PMET720 particles were internalized via clathrin and caveolar mediated endocytosis as well as actin-dependent pinocytosis/phagocytosis. The results suggest that compared to stainless steel welding fumes, the PMET 720 aerosols were not as overtly toxic, and the animals recovered from the acute pulmonary injury by 7 days. |
Development of a thermal spray coating aerosol generator and inhalation exposure system
Afshari AA , McKinney W , Cumpston JL , Leonard HD , Cumpston JB , Meighan TG , Jackson M , Friend S , Kodali V , Lee EG , Antonini JM . Toxicol Rep 2022 9 126-135 Thermal spray coating involves spraying a product (oftentimes metal) that is melted by extremely high temperatures and then applied under pressure onto a surface. Large amounts of a complex metal aerosol (e.g., Fe, Cr, Ni, Zn) are formed during the process, presenting a potentially serious risk to the operator. Information about the health effects associated with exposure to these aerosols is lacking. Even less is known about the chemical and physical properties of these aerosols. The goal was to develop and test an automated thermal spray coating aerosol generator and inhalation exposure system that would simulate workplace exposures. An electric arc wire-thermal spray coating aerosol generator and exposure system was designed and separated into two areas: (1) an enclosed room where the spray coating occurs; (2) an exposure chamber with different measurement devices and controllers. The physicochemical properties of aerosols generated during electric arc wire-thermal spray coating using five different consumable wires were examined. The metal composition of each was determined by inductively coupled plasma-atomic emission spectroscopy (ICP-AES), including two stainless-steel wires [PMET720 (82 % Fe, 13 % Cr); PMET731(66 % Fe, 26 % Cr)], two Ni-based wires [PMET876 (55 % Ni, 17 % Cr); PMET885 (97 % Ni)], and one Zn-based wire [PMET540 (99 % Zn)]. The particles generated regardless of composition were poorly soluble, complex metal oxides and mostly arranged as chain-like agglomerates and similar in size distribution as determined by micro-orifice uniform deposit impactor (MOUDI) and electrical low-pressure impactor (ELPI). To allow for continuous, sequential spray coating during a 4-hr exposure period, a motor rotated the metal pipe to be coated in a circular and up-and-down direction. In a pilot animal study, male Sprague-Dawley rats were exposed to aerosols (25mg/m(3) 4h/d 9 d) generated from electric arc wire- thermal spray coating using the stainless-steel PMET720 consumable wire. The targeted exposure chamber concentration was achieved and maintained during a 4-hr period. At 1 d after exposure, lung injury and inflammation were significantly elevated in the group exposed to the thermal spray coating aerosol compared to the air control group. The system was designed and constructed for future animal exposure studies to generate continuous metal spray coating aerosols at a targeted concentration for extended periods of time without interruption. |
Investigation of particle transfer to sampler covers during the transportation of samples
Erekaife G , Park HD , Kashon ML , Chisholm WP , Lee EG . J Occup Environ Hyg 2021 18 (7) 1-10 This study investigated the effects of particle transfer to the covers of aerosol samplers during transportation of wood dust and welding fume samples. Wood dust samples were collected in a sanding chamber using four sampler types: closed-face cassettes (CFC), CFC with Accu-CAP inserts, disposable inhalable samplers (DIS), and Institute of Occupational Medicine (IOM). Welding fumes were collected in a walk-in chamber using the same samplers, with Solu-Sert replacing Accu-CAP. The samples were divided into two groups, with one group transported by air and the other by land. They were returned in the same manner and analyzed gravimetrically for wood dust and chemically for welding fumes. For wood dust, IOM showed a significantly higher percentage of particles transferred to the covers compared with the other samplers regardless of the transportation mode (p < 0.0001; 64% by air and 15% by land), while other samplers showed less than or close to 10% (3.5-12%). When the percentages of particle transfer to the covers were compared between the air and land transportation, both IOM and CFC samples showed differences between modes of transportation, while others did not. For welding fumes, most samples (61% of samples for copper [Cu] and 76% of samples for manganese [Mn]) showed nondetectable amounts of the analyte on the covers. For all samplers, the particle transfer to the covers for both transportation modes ranged from 0.2-33% for Cu and less than 4.5% for Mn. Overall, this study confirms that particle transfer to sampler covers during transport highly depends upon the transportation mode and sampler type for wood dust, whereas particle transfer seems minimal for welding fumes. The findings of this study are based on two materials and limited sample sizes. Further investigation considering different industry types and tasks, particle size ranges, and materials might be necessary. Nevertheless, occupational professionals should account for this transfer when handling and analyzing samples in practice. |
Perchloroethylene and dry cleaning: It's time to move the industry to safer alternatives
Ceballos DM , Fellows KM , Evans AE , Janulewicz PA , Lee EG , Whittaker SG . Front Public Health 2021 9 638082 Perchloroethylene (PERC) is the most common solvent used for dry cleaning in the United States. PERC is a reproductive toxicant, neurotoxicant, potential human carcinogen, and a persistent environmental pollutant. The Environmental Protection Agency is evaluating PERC under the Frank R. Lautenberg Chemical Safety for the 21st Century Act, which amended the Toxic Substances Control Act (amended TSCA), and has mandated that PERC dry cleaning machines be removed from residential buildings. Some local and state programs are also requiring or facilitating transitions to alternative cleaning technologies. However, the potential for these alternatives to harm human health and the environment is not well-understood. This review describes the issues surrounding the use of PERC and alternative solvents for dry cleaning while highlighting the lessons learned from a local government program that transitioned PERC dry cleaners to the safest current alternative: professional wet cleaning. Implications for future public health research and policy are discussed: (1) we must move away from PERC, (2) any transition must account for the economic instability and cultural aspects of the people who work in the industry, (3) legacy contamination must be addressed even after safer alternatives are adopted, and (4) evaluations of PERC alternatives are needed to determine their implications for the long-term health and sustainability of the people who work in the industry. |
Review of the physicochemical properties and associated health effects of aerosols generated during thermal spray coating processes
Antonini JM , McKinney WG , Lee EG , Afshari AA . Toxicol Ind Health 2020 37 (1) 47-58 Thermal spray coating is a process that applies a molten metal product under pressure onto a surface. Although thermal spray processes have been used for decades, exposure to aerosols formed during thermal spray coating is an emerging risk. Reports indicate that high concentrations of aerosols composed of toxic metals (e.g. chromium) are generated in the workplace. A knowledge gap exists related to the physicochemical properties of thermal spray coating aerosols as well as any potential associated health effects. The objective of this manuscript was to review thermal spray coating and previous studies that have examined the aerosols produced from this process. A thermal spray coating generator and exposure system is also described that has recently been developed to further evaluate the physical and chemical properties of aerosols formed during thermal spray coating as well as to assess the possible health effects of this process in an effort to mitigate potential occupational health hazards related to the industry. |
Characterization of aerosolized particles from nanoclay-enabled composites during manipulation processes
Lee EG , Cena L , Kwon J , Afshari A , Park H , Casuccio G , Bunker K , Lersch T , Gall A , Pham H , Wagner A , Agarwal S , Dinu CZ , Gupta R , Friend SA , Stueckle TA . Environ Sci Nano 2020 7 (5) 1539-1553 Manufacturing, processing, use, and disposal of nanoclay-enabled composites potentially lead to the release of nanoclay particles from the polymer matrix in which they are embedded; however, exposures to airborne particles are poorly understood. The present study was conducted to characterize airborne particles released during sanding of nanoclay-enabled thermoplastic composites. Two types of nanoclay, Cloisite® 25A and Cloisite® 93A, were dispersed in polypropylene at 0%, 1%, and 4% loading by weight. Zirconium aluminum oxide (P100/P180 grits) and silicon carbide (P120/P320 grits) sandpapers were used to abrade composites in controlled experiments followed by real-time and offline particle analyses. Overall, sanding the virgin polypropylene with zirconium aluminum oxide sandpaper released more particles compared to silicon carbide sandpaper, with the later exhibiting similar or lower concentrations than that of polypropylene. Thus, a further investigation was performed for the samples collected using the zirconium aluminum oxide sandpaper. The 1% 25A, 1% 93A, and 4% 93A composites generated substantially higher particle number concentrations (1.3-2.6 times) and respirable mass concentrations (1.2-2.3 times) relative to the virgin polypropylene, while the 4% 25A composite produced comparable results, regardless of sandpaper type. It was observed that the majority of the inhalable particles were originated from composite materials with a significant number of protrusions of nanoclay (18-59%). These findings indicate that the percent loading and dispersion of nanoclay in the polypropylene modified the mechanical properties and thus, along with sandpaper type, affected the number of particles released during sanding, implicating the cause of potential adverse health effects. |
Surgical team exposure to cautery smoke and its mitigation during tonsillectomy
O'Brien DC , Lee EG , Soo JC , Friend S , Callaham S , Carr MM . Otolaryngol Head Neck Surg 2020 163 (3) 194599820917394 OBJECTIVES: To assess the exposure of surgical personnel to known carcinogens during pediatric tonsillectomy and adenoidectomy (T&A) and compare the efficacy of surgical smoke evacuation systems during T&A. STUDY DESIGN: Prospective, case series. SETTING: Tertiary children's hospital. SUBJECTS AND METHODS: The present study assessed operating room workers' exposure to chemical compounds and aerosolized particulates generated during T&A. We also investigated the effect of 3 different smoke-controlling methods: smoke-evacuator pencil cautery (SE), cautery with suction held by an assistant (SA), and cautery without suction (NS). RESULTS: Thirty cases were included: 12 in the SE group, 9 in SA, and 9 in NS. The chemical exposure levels were lower than or similar to baseline background concentrations, with the exception of methylene chloride and acetaldehyde. Within the surgical plume, none of the chemical compounds exceeded the corresponding occupational exposure limit (OEL). The mean particulate number concentration in the breathing zone during tonsillectomy was 508 particles/cm(3) for SE compared to 1661 particles/cm(3) for SA and 8208 particles/cm(3) for NS cases. NS was significantly different compared to the other two methods (P = .0009). CONCLUSIONS: Although the exposure levels to chemicals were considerably lower than the OELs, continuous exposures to these chemicals could cause adverse health effects to surgical personnel. These findings suggest that the use of a smoke-evacuator pencil cautery or an attentive assistant with handheld suction would reduce exposure levels to the aerosolized particles during routine T&A, compared to the use of cautery without suction. |
Effect of electrocautery settings on particulate concentrations in surgical plume during tonsillectomy
Carr MM , Patel VA , Soo JC , Friend S , Lee EG . Otolaryngol Head Neck Surg 2020 162 (6) 194599820914275 OBJECTIVES: To describe the effect of monopolar electrocautery (EC) settings on surgical plume particulate concentration during pediatric tonsillectomy. STUDY DESIGN: Cross-sectional study. SETTING: Tertiary medical center. SUBJECTS AND METHODS: During total tonsillectomy exclusively performed with EC, air was sampled with a surgeon-worn portable particle counter. The airborne mean and maximum particle concentrations were compared for tonsillectomy performed with EC at 12 W vs 20 W, with smoke evacuation system (SES) and no smoke evacuation (NS). RESULTS: A total of 36 children were included in this analysis: 9 cases with EC at 12 W and SES (12SES), 9 cases with EC at 20 W and SES (20SES), 9 cases with EC at 12 W without SES (12NS), and 9 cases with EC at 20 W without SES (20NS). Mean particle number concentration in the breathing zone during tonsillectomy was 1661 particles/cm(3) for 12SES, 5515 particles/cm(3) for 20SES, 8208 particles/cm(3) for 12NS, and 78,506 particles/cm(3) for 20NS. There was a statistically significant difference in the particle number concentrations among the 4 groups. The correlation between the particle number concentration and EC time was either moderate (for 12SES) or negative (for remaining groups). CONCLUSION: Airborne particle concentrations during tonsillectomy are over 9.5 times higher when EC is set at 20 W vs 12 W with NS, which is mitigated to 3.3 times with SES. Applying lower EC settings with SES during pediatric tonsillectomy significantly reduces surgical plume exposure for patients, surgeons, and operating room personnel, which is a well-known occupational health hazard. |
Adoption of exposure assessment tools to assist in providing respiratory protection recommendations
Lee EG , Ceballos DM . Ann Work Expo Health 2020 64 (5) 547-557 Selecting a proper respirator requires determining the ratio of an employee's maximum use concentration (MUC) divided by the occupational exposure limit of a chemical. Current industrial hygiene practice often is to obtain a percentile estimate (e.g. 95th) of the measured exposure distribution to apply as the MUC. However, practitioners who are not yet familiar with statistical or mathematical approaches may choose the highest exposure data point as the MUC, a method that is still considered appropriate by the Occupational Safety and Health Administration. Nonetheless, choosing a respirator using the highest exposure data point when only limited data are available may result in not always providing the most adequate respirator. Because some practitioners are not familiar with exposure assessment tools, our primary goal in this study was to demonstrate the best process when selecting respiratory protection by using a combination of exposure data and assessment tools. Three user-friendly tools, IHDataAnalyst, Advanced REACH Tool, and IHSTAT, were selected to demonstrate how to use different types of tool outputs when choosing a respirator. A decision logic was developed to help users navigate the combining of different data inputs. Personal full-shift exposure data collected in four different workplaces were used to describe four different outcomes generated when the maximum exposure data point and the tool's output are compared with the exposure limit of the chemical. Outcomes varied, from determinations of 'high confidence' (or final decision) to 'low confidence' (or indicating more data are needed) in the selection of a respirator recommendation. In conclusion, systematically adopting the combination of exposure data and assessment tools could increase practitioners' confidence in decision-making when choosing respirators from a limited exposure data set. These suggested guidelines will lead practitioners toward good industrial hygiene practices. |
TREXMO plus: an advanced self-learning model for occupational exposure assessment
Savic N , Lee EG , Gasic B , Vernez D . J Expo Sci Environ Epidemiol 2020 30 (3) 554-566 In Europe, several occupational exposure models have been developed and are recommended for regulatory exposure assessment. Only some information on the substance of interest (e.g., vapor pressure) and the workplace conditions (e.g., ventilation rate) is required in these models to predict an exposure value that will be later used to characterize the risk. However, it has been shown that models may differ in their predictions and that usually, one of the models best fits a given set of exposure conditions. Unfortunately, there are no clear rules on how to select the best model. In this study, we developed a new modeling approach that together uses the three most popular models, Advanced REACH Tool, Stoffenmanger, and ECETOC TRAv3, to obtain a unique exposure prediction. This approach is an extension of the TREXMO tool, and is called TREXMO+. TREXMO+ applies a machine-learning technique on a set of exposure data with the measured values to split them into smaller subsets, corresponding to exposure conditions sharing similar characteristics. For each subset, TREXMO+ then establishes a regression model with the three REACH tools used as the exposure predictors. The performance of the new model was tested and a comparison was made between the results obtained by TREXMO+ and those obtained by conventional tools. TREXMO+ model was found to be less biased and more accurate than the REACH models. Its prediction differs generally from measurements by a factor of 2-3 from measurements, whereas conventional models were found to differ by a factor 2-14. However, as the available test dataset is limited, its results will need to be confirmed by larger-scale tests. |
Evaluation of sorbent sampling and analysis procedures for acetone in workplace air: Variations of concentration and relative humidity
Soo JC , Lebouf RF , Chisholm WP , Nelson J , Roberts J , Kashon ML , Lee EG , Harper M . Ann Work Expo Health 2019 64 (1) 96-105 This study experimentally evaluates the performance of different sorbent tubes for sampling acetone vapor in workplace air. A dynamic atmosphere system produced an acetone alone and a mixture with other analytes containing ~73, 483, and 1898 microg acetone mass loading at 25, 50, and 75% relative humidity (RH) at 25 degrees C. Sorbent samples were analyzed in accordance with OSHA Method 69 (Carbosieve S-III) and NMAM 1501, modified to use Anasorb 747 sorbent. Both methods were modified to include the additional analytes. Additional extraction procedures with and without 1% dimethylformamide and anhydrous magnesium sulfate were included in the modified NMAM 1501 using Anasorb 747. Silica gel sorbent tubes analyzed according to NMAM 2027 were included. There were significant reductions in the recovery of acetone from both Anasorb 747 and Carbosieve S-III collected from air at 75% RH, relative to collection at 25 or 50% RH at very low loading compared with that of samples collected at mid to high loading. Silica gel provided a consistent recovery of acetone at all RHs and in the presence of other chemical interferences at 75% RH. The likely cause of mass dependence may arise from the humidity effect on acetone adsorption onto both beaded active carbon and carbon molecular sieve either in sampling or in analysis. The present study confirms not only previous observations but also adds to the literature showing carbonaceous sorbents are not well suited for sampling ketones at high humidity and low concentration. |
Inter-assessor agreement for TREXMO and its models outside the translation framework
Savic N , Lee EG , Gasic B , Vernez D . Ann Work Expo Health 2019 63 (7) 814-820 Within the framework of Registration, Evaluation, Authorization, and restriction of CHemicals (REACH), occupational exposure models are often used to predict the levels of exposure at a workplace. Poor inter-assessor agreement with their use poses a concern that may lead to different and dangerous risk conclusions. TREXMO (v1, 2016), a web tool providing parameter translations between six exposure models under REACH, is expected to improve the inter-assessor agreement. In this study, 18 assessors performed exposure assessment for six exposure situations within and outside the framework of this translation tool. In more than half of the evaluated cases, the results showed better agreement between assessors selecting the exposure parameters within the framework of TREXMO than when manually coding. The most affected were the parameters related to activity (such as "handling types" of Stoffenmanager) and exposure control (such as local controls). Furthermore, the agreement between the estimates calculated by different assessors was also improved when performing the translations between the models. For Stoffenmanager, for example, the relative standard deviation of 70-121%, obtained for vapors without applying the translation system, was 29-94% with the translations from ART. These findings showed a potential of TREXMO to impact the inter-assessor agreement. Because the study was limited to 18 assessors and only six exposure situations were assessed, further investigations are suggested. |
Performance evaluation of disposable inhalable aerosol sampler at a copper electrorefinery
Lee EG , Grimson PJ , Chisholm WP , Kashon ML , He X , L'Orange C , Volckens J . J Occup Environ Hyg 2019 16 (3) 1-10 This study evaluates the performance of the disposable inhalable aerosol sampler (DIAS), a new sampler developed to be more cost-effective than the traditional inhalable particle samplers and comparable to the inhalable particle sampling convention. Forty-eight pairs of the DIAS prototype and the IOM sampler were utilized to collect copper exposure measurements (23 personal and 25 area) at an electrorefinery facility. The geometric mean (GM) value of ratios of exposure data (DIAS/IOM) was 1.1, while the GM of ratios (DIAS/IOM) was 1.6 for the area exposure data, revealing 84%of the ratios were greater than one. For both personal and area exposure data, the concordance correlation coefficient tests revealed significant disagreements between the two types of samplers and suggested precision as the source of the disagreement. The estimated mean concentration was higher for the DIAS compared that for the IOM for the area exposure data (p < 0.05), while the results were comparable for the personal exposure data (p = 0.49). Overall, the DIAS generated higher exposure results compared to the IOM sampler for the area exposures. For the personal exposures, the findings were inconclusive due to inconsistent results of factors aforementioned. This study is limited to one metal component (copper) of the dust at a worksite. To date, this is the first field evaluation using personal exposure data to test the performance of the DIAS and the second evaluation using area exposure data. Thus, it will be necessary to conduct additional field evaluations with various elements to further evaluate the performance of the DIAS. In addition, particle migration to the internal walls of the cap was observed during the transportation of collected samples to a laboratory for both sampler types (6.4% for the DIAS and 7.4% for the IOM). Occupational health and safety professionals should be aware of potential errors caused from transferring samples from a field to a laboratory and should be careful not to exclude particles collected on the caps. |
Assessment of two personal breathing recording devices in a simulated healthcare environment
Zhu J , He X , Guffey S , Bergman MS , Lee EG , Zhuang Z . J Int Soc Respir Prot 2018 35 (2) 98-111 Background: In the field of respiratory protecting for healthcare workers (HCWs), no respiratory data are available recorded when HCWs are performing their work activities. The objective of this study was to assess the performance of two wearable breathing recording devices in a simulated healthcare environment. Methods: Breathing recording devices from two different manufactures "A" and "B" were assessed using 15 subjects while performing a series of simulated healthcare work activities (Patient assessment; Vitals; IV treatment; Changing linen; Carrying weight while walking; Normal breathing while standing). The minute volume (MV, L/min), mean inhalation flow (MIF, L/min), peak inhalation flow (PIF, L/min), breathing frequency (f, breaths/min), and tidal volume (TV, L/min) measured by each device were analyzed. Bland-Altman method was applied to explore the variability of devices A and B. Duncan's multiple range test was used to investigate the differences among exercise-specific inspiratory flow rates. Results: The average MV, MIF and PIF reported by device A were 23, 54, and 82 L/min with 95% upper confidence intervals (CIs) of 25, 60 and 92 L/min; the mean differences of MV, MIF and PIF presented by the two units of device A were 0.9, 1.3, and 2.8 L/min, respectively. The average values and mean differences of MV, MIF and PIF found with device B were significantly higher than device A (P<0.05), showing a high variability. During non-speech activities, the PIF/MV and MIF/MV ratios were >3.14 and >2, while with speech, the ratios increased to >6 and >3. The f during speech (15 breaths/min) was significantly lower than non-speech activities (20-25 breaths/min). Among different simulated work activities, the PIF of "patient assessment" was the highest. Conclusions: This study demonstrated a novel approach to characterize respiratory flow for healthcare workers using an innovative wearable flow recording device. Data from this investigation could be useful in the development of future respirator test standards. |
Evaluation of exposure assessment tools under REACH: Part I-Tier 1 Tools
Lee EG , Lamb J , Savic N , Basinas I , Gasic B , Jung C , Kashon ML , Kim J , Tischer M , van Tongeren M , Vernez D , Harper M . Ann Work Expo Health 2018 63 (2) 218-229 Tier 1 occupational exposure assessment tools recommended for use under the Registration, Evaluation, Authorization, and restriction of CHemicals (REACH) were evaluated using newly collected measurement data. Evaluated tools included the ECETOC TRAv2 and TRAv3, MEASEv1.02.01, and EMKG-EXPO-TOOL. Fifty-three exposure situations (ESs) based on tasks/chemicals were developed from National Institute for Occupational Safety and Health field surveys. During the field surveys, high quality contextual information required for evaluating the tools was also collected. For each ES, applicable tools were then used to generate exposure estimates using a consensus approach. Among 53 ESs, only those related to an exposure category of liquids with vapor pressure (VP) > 10 Pa had sufficient numbers of exposure measurements (42 ESs with n = 251 for TRAv2 and TRAv3 and 40 ESs with n = 243 for EMKG-EXPO-TOOL) to be considered in detail. The results for other exposure categories (aqueous solutions, liquids with VP </= 10 Pa, metal processing, powders, and solid objects) had insufficient measurement to allow detailed analyses (results listed in the Supplementary File). Overall, EMKG-EXPO-TOOL generated more conservative results than TRAv2 and TRAv3 for liquids with high VP. This finding is at least partly due to the fact that the EMKG-EXPO-TOOL only considers pure substances and not mixtures of chemical agents. For 34 out of 40 ESs available for chemicals with VP > 10 Pa, the liquid was a mixture rather than a pure substance. TRAv3 was less conservative than TRAv2, probably due to additional refinement of some input parameters. The percentages of exposure measurement results exceeding the corresponding tool estimates for liquids with VP > 10 Pa by process category and by input parameters were always higher for TRAv3 compared to those for TRAv2. Although the conclusions of this study are limited to liquids with VP > 10 Pa and few process categories, this study utilized the most transparent contextual information compared to previous studies, reducing uncertainty from assumptions for unknown input parameters. A further validation is recommended by collecting sufficient exposure data covering other exposure categories and all process categories under REACH. |
Evaluation of exposure assessment tools under REACH: Part II-Higher Tier Tools
Lee EG , Lamb J , Savic N , Basinas I , Gasic B , Jung C , Kashon ML , Kim J , Tischer M , van Tongeren M , Vernez D , Harper M . Ann Work Expo Health 2018 63 (2) 230-241 Stoffenmanager(R)v4.5 and Advanced REACH Tool (ART) v1.5, two higher tier exposure assessment tools for use under REACH, were evaluated by determining accuracy and robustness. A total of 282 exposure measurements from 51 exposure situations (ESs) were collected and categorized by exposure category. In this study, only the results of liquids with vapor pressure (VP) > 10 Pa category having a sufficient number of exposure measurements (n = 251 with 42 ESs) were utilized. In addition, the results were presented by handling/activity description and input parameters for the same exposure category. It should be noted that the performance results of Stoffenmanager and ART in this study cannot be directly compared for some ESs because ART allows a combination of up to four subtasks (and nonexposed periods) to be included, whereas the database for Stoffenmanager, separately developed under the permission of the legal owner of Stoffenmanager, permits the use of only one task to predict exposure estimates. Thus, it would be most appropriate to compare full-shift measurements against ART predictions (full shift including nonexposed periods) and task-based measurements against task-based Stoffenmanager predictions. For liquids with VP > 10 Pa category, Stoffenmanager(R)v4.5 appeared to be reasonably accurate and robust when predicting exposures [percentage of measurements exceeding the tool's 90th percentile estimate (%M > T) was 15%]. Areas that could potentially be improved include ESs involving the task of handling of liquids on large surfaces or large work pieces, allocation of high and medium VP inputs, and absence of local exhaust ventilation input. Although the ART's median predictions appeared to be reasonably accurate for liquids with VP > 10 Pa, the %M > T for the 90th percentile estimates was 41%, indicating that variance in exposure levels is underestimated by ART. The %M > T using the estimates of the upper value of 90% confidence interval (CI) of the 90th percentile estimate (UCI90) was considerably reduced to 18% for liquids with VP > 10 Pa. On the basis of this observation, users might be to consider using the upper limit value of 90% CI of the 90th percentile estimate for predicting reasonable worst case situations. Nevertheless, for some activities and input parameters, ART still shows areas to be improved. Hence, it is suggested that ART developers review the assumptions in relation to exposure variability within the tool, toward improving the tool performance in estimating percentile exposure levels. In addition, for both tools, only some handling/activity descriptions and input parameters were considered. Thus, further validation studies are still necessary. |
Evaluation of a portable gas chromatograph with photoionization detector under variations of VOC concentration, temperature and relative humidity
Soo JC , Lee EG , LeBouf RF , Kashon ML , Chisholm W , Harper M . J Occup Environ Hyg 2018 15 (4) 0 The objective of this present study was to evaluate the performance of a portable gas chromatograph horizontal line photoionization detector (GC-PID), under various test conditions to determine if it could be used in occupational settings. A mixture of seven volatile organic compounds (VOCs) - acetone, ethylbenzene, methyl isobutyl ketone, toluene, m-xylene, p-xylene, and o-xylene - was selected because its components are commonly present in paint manufacturing industries. A full-factorial combination of four concentration levels (exposure scenarios) of VOC mixtures, three different temperatures (25 C, 30 C, and 35 C), and three relative humidities (RHs; 25%, 50%, and 75%) was conducted in a full- size controlled environmental chamber. Three repetitions were conducted for each test condition allowing for estimation of accuracy. Time-weighted average exposure data were collected using solid sorbent tubes (Anasorb 747, SKC Inc.) as the reference sampling medium. Calibration curves of Frog-4000 using the dry gases showed R(2) > 0.99 for all analytes except for toluene (R(2) = 0.97). Frog-4000 estimates within a test condition showed good consistency for the performance of repeated measurement. However, there was approximately 41-64% reduction in the analysis of polar acetone with 75% RH relative to collection at 25% RH. Although Frog-4000 results correlated well with solid sorbent tubes (r = 0.808-0.993, except for toluene) most of the combinations regardless of analyte did not meet the < 25% accuracy criterion recommended by NIOSH. The effect of chromatographic co-elution can be seen with m, p-xylene when the results are compared to the sorbent tube sampling technique with GC-flame ionization detector. The results indicated an effect of humidity on the quantification of the polar compounds that might be attributed to the pre-concentrator placed in the selected GC-PID. Further investigation may resolve the humidity effect on sorbent trap with micro GC pre-concentrator when water vapor is present. Although this instrument does not fulfill the accuracy criterion specified in the NIOSH technical report No. 2012-162, it can be used as a screening tool for range finding monitoring with dry gases calibration in the occupational setting rather than compliance monitoring. |
Occupational Exposures to New Drycleaning Solvents: High-flashpoint Hydrocarbons and Butylal
Ceballos DM , Whittaker SG , Lee EG , Roberts J , Streicher R , Gong FN , Broadwater W , Broadwater K . J Occup Environ Hyg 2016 13 (10) 0 The drycleaning industry is moving away from using perchloroethylene. Occupational exposures to two alternative drycleaning solvents, butylal and high-flashpoint hydrocarbons, have not been well-characterized. We evaluated four drycleaning shops that used these alternative solvents. The shops were staffed by Korean- and Cantonese-speaking owners, and Korean-, Cantonese-, and Spanish-speaking employees. Because most workers had limited English proficiency we used language services in our evaluations. In two shops we collected personal and area air samples for butylal. We also collected air samples for formaldehyde and butanol, potential hydrolysis products of butylal. Because there are no occupational exposure limits for butylal, we assessed employee health risks using control banding tools. In the remaining two shops we collected personal and area air samples for high-flashpoint hydrocarbon solvents. In all shops the highest personal airborne exposures occurred when workers loaded and unloaded the drycleaning machines and pressed drycleaned fabrics. The air concentrations of formaldehyde and butanol in the butylal shops were well below occupational exposure limits. Likewise, the air concentrations of high-flashpoint hydrocarbons were also well below occupational exposure limits. However, we saw potential skin exposures to these chemicals. We provided recommendations on appropriate work practices and the selection and use of personal protective equipment. These recommendations were consistent with those derived using control banding tools for butylal. However, there is insufficient toxicological and health information to determine the safety of butylal in occupational settings. Independent evaluation of the toxicological properties of these alternative drycleaning solvents, especially butylal, is urgently needed. |
Evaluation of the dark-medium objective lens in counting asbestos fibers by phase-contrast microscopy
Lee EG , Nelson JH , Kashon ML , Harper M . Ann Occup Hyg 2015 59 (5) 616-28 A Japanese round-robin study revealed that analysts who used a dark-medium (DM) objective lens reported higher fiber counts from American Industrial Hygiene Association (AIHA) Proficiency Analytical Testing (PAT) chrysotile samples than those using a standard objective lens, but the cause of this difference was not investigated at that time. The purpose of this study is to determine any major source of this difference by performing two sets of round-robin studies. For the first round-robin study, 15 AIHA PAT samples (five each of chrysotile and amosite generated by water-suspended method, and five chrysotile generated by aerosolization method) were prepared with relocatable cover slips and examined by nine laboratories. A second round-robin study was then performed with six chrysotile field sample slides by six out of nine laboratories who participated in the first round-robin study. In addition, two phase-shift test slides to check analysts' visibility and an eight-form diatom test plate to compare resolution between the two objectives were examined. For the AIHA PAT chrysotile reference slides, use of the DM objective resulted in consistently higher fiber counts (1.45 times for all data) than the standard objective (P-value < 0.05), regardless of the filter generation (water-suspension or aerosol) method. For the AIHA PAT amosite reference and chrysotile field sample slides, the fiber counts between the two objectives were not significantly different. No statistically significant differences were observed in the visibility of blocks of the test slides between the two objectives. Also, the DM and standard objectives showed no pattern of differences in viewing the fine lines and/or dots of each species images on the eight-form diatom test plate. Among various potential factors that might affect the analysts' performance of fiber counts, this study supports the greater contrast caused by the different phase plate absorptions as the main cause of high counts for the AIHA PAT chrysotile slides using the DM objective. The comparison of fiber count ratios (DM/standard) between the AIHA PAT chrysotile samples and chrysotile field samples indicates that there is a fraction of fibers in the PAT samples approaching the theoretical limit of visibility of the phase-contrast microscope with 3-degree phase-shift. These fibers become more clearly visible through the greater contrast from the phase plate absorption of the DM objective. However, as such fibers are not present in field samples, no difference in counts between the two objectives was observed in this study. The DM objective, therefore, could be allowed for routine fiber counting as it will maintain continuity with risk assessments based on earlier phase-contrast microscopy fiber counts from field samples. Published standard methods would need to be modified to allow a higher aperture specification for the objective. |
Assessing Exposures to 1-chloro-4-(trifluoromethyl) Benzene (PCBTF) in U.S. Workplaces
Lee EG , Lewis B , Burns DA , Kashon ML , Kim SW , Harper M . J Occup Environ Hyg 2015 12 (7) D123-30 The chemical compound 1-Chloro-4-(trifluoromethyl) benzene (CAS No: 98-56-6)—also known as PCBTF, Oxsol 100, or Parachlorobenzotrifluoride—was nominated to the National Toxicology Program (NTP) for toxicity and carcinogenicity studies (http://ntp.niehs.nih.gov/ntp/noms/support_docs/pcbtf06-0409.pdf). The nomination was based on the increasing use of PCBTF by industries and consumers, since it was exempted by the Environmental Protection Agency (EPA) as a volatile organic compound in emissions reporting on the basis of not reacting in a manner that would contribute to the formation of tropospheric ozone.(1) Although PCBTF is no longer manufactured in the United States, approximately 29 million lbs. were imported in 2012(2) and used in various applications to replace other chlorinated solvents with known environmental or human health hazards. Those applications include the automotive industry as industry-wide applications in coatings, thinners, and cleaning solvents, and repair and maintenance cleaning and as a consumer product for cosmetic stain removal and aerosol rust prevention.(3) | The toxicity information on PCBTF is available from various resources(4,5) including the NTP website.(6) These studies, however, are limited to short-term toxicity, and chronic inhalation toxicity and carcinogenicity studies are unavailable. There are no Occupational Safety and Health Administration (OSHA) regulations specific to limiting occupational exposures to PCBTF. The National Institute for Occupational Safety and Health (NIOSH) has not established a time-weighted average (TWA) recommended exposure level, and the American Conference of Governmental Industrial Hygienists (ACGIH®) has not established a TWA-threshold limit value (TLV®) for PCBTF. The Occidental Chemical Corporation, which used to manufacture PCBTF in the United States, established a corporate exposure limit (CEL), which was a TWA limit of 25 ppm (185 mg/m3) for an 8-hr work-shift. The toxicological basis for setting this limit is not known to us. However, Occidental Chemical Corporation no longer manufactures or imports PCBTF into the United States. |
Evaluation of pump pulsation in respirable size-selective sampling: Part III. Investigation of European standard methods
Soo J-C , Lee EG , Lee LA , Kashon ML , Harper M . Ann Occup Hyg 2014 58 (8) 1006-17 Lee et al. (Evaluation of pump pulsation in respirable size-selective sampling: part I. Pulsation measurements. Ann Occup Hyg 2014a;58:60–73) introduced an approach to measure pump pulsation (PP) using a real-world sampling train, while the European Standards (EN) (EN 1232-1997 and EN 12919-1999) suggest measuring PP using a resistor in place of the sampler. The goal of this study is to characterize PP according to both EN methods and to determine the relationship of PP between the published method (Lee et al., 2014a) and the EN methods. Additional test parameters were investigated to determine whether the test conditions suggested by the EN methods were appropriate for measuring pulsations. Experiments were conducted using a factorial combination of personal sampling pumps (six medium- and two high-volumetric flow rate pumps), back pressures (six medium- and seven high-flow rate pumps), resistors (two types), tubing lengths between a pump and resistor (60 and 90cm), and different flow rates (2 and 2.5 l min-1 for the medium- and 4.4, 10, and 11.2 l min-1 for the high-flow rate pumps). The selection of sampling pumps and the ranges of back pressure were based on measurements obtained in the previous study (Lee et al., 2014a). Among six medium-flow rate pumps, only the Gilian5000 and the Apex IS conformed to the 10% criterion specified in EN 1232-1997. Although the AirChek XR5000 exceeded the 10% limit, the average PP (10.9%) was close to the criterion. One high-flow rate pump, the Legacy (PP = 8.1%), conformed to the 10% criterion in EN 12919-1999, while the Elite12 did not (PP = 18.3%). Conducting supplemental tests with additional test parameters beyond those used in the two subject EN standards did not strengthen the characterization of PPs. For the selected test conditions, a linear regression model [PPEN = 0.014 + 0.375 × PPNIOSH (adjusted R 2 = 0.871)] was developed to determine the PP relationship between the published method (Lee et al., 2014a) and the EN methods. The 25% PP criterion recommended by Lee et al. (2014a), average value derived from repetitive measurements, corresponds to 11% PPEN. The 10% pass/fail criterion in the EN Standards is not based on extensive laboratory evaluation and would unreasonably exclude at least one pump (i.e. AirChek XR5000 in this study) and, therefore, the more accurate criterion of average 11% from repetitive measurements should be substituted. This study suggests that users can measure PP using either a real-world sampling train or a resistor setup and obtain equivalent findings by applying the model herein derived. The findings of this study will be delivered to the consensus committees to be considered when those standards, including the EN 1232-1997, EN 12919-1999, and ISO 13137-2013, are revised. |
Comparison of lead and tin concentrations in air at a solder manufacturer from the closed-face 37 mm cassette with and without a custom cellulose-acetate cassette insert
Lee EG , Chisholm WP , Burns DA , Nelson JH , Kashon ML , Harper M . J Occup Environ Hyg 2014 11 (12) 0 A polyvinyl chloride (PVC) cassette insert with PVC filter (ACCU-CAP) in a 37-mm closed -face cassette (CFC) was designed for gravimetric analysis. A customized version of the ACCU-CAP, also to be used in the CFC, was manufactured from an acid-digestible cellulose-acetate cassette insert joined to a mixed cellulose ester (MCE) filter for wet chemical analysis. The aim of this study was to compare metal particle concentrations as sampled by the customized insert (CI) in a CFC sampler with the traditional sampling method using only a MCE filter in the CFC. Thirty-nine personal and 13 area samples were taken using paired filter-based CFC and the CI in CFC samplers at a solder manufacturing plant. The CI was removed from its CFC, digested and analyzed as a whole. The MCE filter from the typical CFC was removed for analysis and then the interior of the cassette was wiped with Ghost Wipe for a separate analysis. The MCE filter only, Ghost Wipe, and CI were separately dissolved in heated nitric acid for ICP-MS analysis. Overall, the geometric mean concentration of the filter-only (FO) samples was considerably lower than that of the CI samples, by 53% for lead and 32% for tin. However, if the FO analysis was added to the corresponding Ghost Wipe analysis, i.e., filter+interior wipe (FW), the geometric mean concentrations of the FW results were similar to those of the CI results (by 113% for lead and 98% for tin). For both lead and tin the comparison of (log-transformed) metal concentrations between the FW and CI results showed no statistically significant difference (p-value = 0.3009 for lead and 0.800 for tin), while the comparison between the FO and CI results shows statistically significant differences (all p-values<0.05). In conclusion, incorporating the sampler internal non-filter deposits by wiping or use of an internal filter capsule gave higher results than analyzing only the filter. Close agreement between the two methods of including non-filter deposits is an indication of general equivalency. |
Exposure to chlorpyrifos in gaseous and particulate form in greenhouses: a pilot study
Kim SW , Lee EG , Lee T , Lee LA , Harper M . J Occup Environ Hyg 2014 11 (8) 547-55 Phase distribution of airborne chemicals is important because intake and uptake mechanisms of each phase are different. The phase distribution and concentrations are needed to determine strategies of exposure assessment, hazard control, and worker protection. However, procedures for establishing phase distribution and concentration have not been standardized. The objective of this study was to compare measurements of an airborne semivolatile pesticide (chlorpyrifos) by phase using two different procedures. Six pesticide applications in two facilities were studied and at each site, samples were collected for three time slots: T1, the first 1 or 2 hours after the commencement of application; T2, a six-hour period immediately following T1; and T3, a six-hour period after the required reentry interval (24 hours for chlorpyrifos).Two phase-separating devices were collocated at the center of each greenhouse: Semivolatile Aerosol Dichotomous Sampler (SADS) using flow-rates of 1.8 l.min-1 and 0.2 l.min-1, corresponding to a total inlet flow rate of 2.0 l.min-1 with a vapor phase flow fraction of 0.1, and electrostatic precipitator (ESP), along with a standard OVS XAD-2 tube. Chlorpyrifos in vapor and particulate form in SADS sampling train and that in vapor form in ESP sampling train were collected in OVS tubes. Chlorpyrifos in particulate form in ESP setting would have been collected on aluminum substrate. However, no chlorpyrifos in particulate form was recovered from the ESP. Overall (vapor plus particle) concentrations measured by OVS ranged 11.7-186.6 mug/m3 at T1 and decreased on average 77.1% and 98.9% at T2 and T3, respectively. Overall concentrations measured by SADS were 66.6%, 72.7%, and 102% of those measured by OVS on average at T1, T2, and T3, respectively. Particle fractions from the overall concentrations measured by SADS were 60.0%, 49.2%, and 13.8%, respectively, for T1, T2, and T3. SADS gives better guidance on the distribution of chlorpyrifos than does the ESP, although the accuracy of the concentration distribution cannot be verified in the absence of a standardized procedure for determining phase division. |
Evaluation of pump pulsation in respirable size-selective sampling: Part I. pulsation measurements
Lee EG , Lee L , Mohlmann C , Flemmer MM , Kashon M , Harper M . Ann Occup Hyg 2013 58 (1) 60-73 Pulsations generated by personal sampling pumps modulate the airflow through the sampling trains, thereby varying sampling efficiencies, and possibly invalidating collection or monitoring. The purpose of this study was to characterize pulsations generated by personal sampling pumps relative to a nominal flow rate at the inlet of different respirable cyclones. Experiments were conducted using a factorial combination of 13 widely used sampling pumps (11 medium and 2 high volumetric flow rate pumps having a diaphragm mechanism) and 7 cyclones [10-mm nylon also known as Dorr-Oliver (DO), Higgins-Dewell (HD), GS-1, GS-3, Aluminum, GK2.69, and FSP-10]. A hot-wire anemometer probe cemented to the inlet of each cyclone type was used to obtain pulsation readings. The three medium flow rate pump models showing the highest, a midrange, and the lowest pulsations and two high flow rate pump models for each cyclone type were tested with dust-loaded filters (0.05, 0.21, and 1.25mg) to determine the effects of filter loading on pulsations. The effects of different tubing materials and lengths on pulsations were also investigated. The fundamental frequency range was 22-110 Hz and the magnitude of pulsation as a proportion of the mean flow rate ranged from 4.4 to 73.1%. Most pump/cyclone combinations generated pulse magnitudes ≥10% (48 out of 59 combinations), while pulse shapes varied considerably. Pulsation magnitudes were not considerably different for the clean and dust-loaded filters for the DO, HD, and Aluminum cyclones, but no consistent pattern was observed for the other cyclone types. Tubing material had less effect on pulsations than tubing length; when the tubing length was 183cm, pronounced damping was observed for a pump with high pulsation (>60%) for all tested tubing materials except for the Tygon Inert tubing. The findings in this study prompted a further study to determine the possibility of shifts in cyclone sampling efficiency due to sampling pump pulsations, and those results are reported subsequently. |
Evaluation of pump pulsation in respirable size-selective sampling: Part II. changes in sampling efficiency
Lee EG , Lee T , Kim SW , Lee L , Flemmer MM , Harper M . Ann Occup Hyg 2013 58 (1) 74-84 This second, and concluding, part of this study evaluated changes in sampling efficiency of respirable size-selective samplers due to air pulsations generated by the selected personal sampling pumps characterized in Part I (Lee E, Lee L, Mohlmann C et al. Evaluation of pump pulsation in respirable size-selective sampling: Part I. Pulsation measurements. Ann Occup Hyg 2013). Nine particle sizes of monodisperse ammonium fluorescein (from 1 to 9 mum mass median aerodynamic diameter) were generated individually by a vibrating orifice aerosol generator from dilute solutions of fluorescein in aqueous ammonia and then injected into an environmental chamber. To collect these particles, 10-mm nylon cyclones, also known as Dorr-Oliver (DO) cyclones, were used with five medium volumetric flow rate pumps. Those were the Apex IS, HFS513, GilAir5, Elite5, and Basic5 pumps, which were found in Part I to generate pulsations of 5% (the lowest), 25%, 30%, 56%, and 70% (the highest), respectively. GK2.69 cyclones were used with the Legacy [pump pulsation (PP) = 15%] and Elite12 (PP = 41%) pumps for collection at high flows. The DO cyclone was also used to evaluate changes in sampling efficiency due to pulse shape. The HFS513 pump, which generates a more complex pulse shape, was compared to a single sine wave fluctuation generated by a piston. The luminescent intensity of the fluorescein extracted from each sample was measured with a luminescence spectrometer. Sampling efficiencies were obtained by dividing the intensity of the fluorescein extracted from the filter placed in a cyclone with the intensity obtained from the filter used with a sharp-edged reference sampler. Then, sampling efficiency curves were generated using a sigmoid function with three parameters and each sampling efficiency curve was compared to that of the reference cyclone by constructing bias maps. In general, no change in sampling efficiency (bias under +/-10%) was observed until pulsations exceeded 25% for the DO cyclone. However, for three models of pumps producing 30%, 56%, and 70% pulsations, substantial changes were confirmed. The GK2.69 cyclone showed a similar pattern to that of the DO cyclone, i.e. no change in sampling efficiency for the Legacy producing 15% pulsation and a substantial change for the Elite12 producing 41% pulsation. Pulse shape did not cause any change in sampling efficiency when compared to the single sine wave. The findings suggest that 25% pulsation at the inlet of the cyclone as measured by this test can be acceptable for the respirable particle collection. If this test is used in place of that currently in European standards (EN 1232-1997 and EN 12919-1999) or is used in any International Organization for Standardization standard, then a 25% pulsation criterion could be adopted. This work suggests that a 10% criterion as currently specified in the European standards for testing may be overly restrictive and not able to be met by many pumps on the market. Further work is recommended to determine which criterion would be applicable to this test if it is to be retained in its current form. |
Exposure models for the prior distribution in bayesian decision analysis for occupational hygiene decision making.
Lee EG , Kim SW , Feigley CE , Harper M . J Occup Environ Hyg 2012 10 (2) 97-108 This study introduces two semi-quantitative methods, Structured Subjective Assessment (SSA) and Control of Substances Hazardous to Health (COSHH) Essentials, in conjunction with 2-dimensional Monte Carlo simulations for determining prior probabilities. Prior distribution using expert judgment was included for comparison. Practical applications of the proposed methods were demonstrated using personal exposure measurements of isoamyl acetate in an electronics manufacturing facility and of isopropanol in a printing shop. Applicability of these methods in real workplaces was discussed based on the advantages and disadvantages of each method. Although these methods could not be completely independent of expert judgments, this study demonstrated a methodological improvement in the estimation of the prior distribution for the Bayesian decision analysis tool. The proposed methods provide a logical basis for the decision process by considering determinants of worker exposure. [Supplementary materials are available for this article. Go to the publisher's online edition of Journal of Occupational and Environmental Hygiene for the following free supplementary resource: Coding of the MC Simulation (SSA Method)] |
Effects of covered solid sorbent tube sample holders on organic vapor measurements
Marpoe BS , Groves WA , Lee EG , Slaven JE , Harper M . J Occup Environ Hyg 2012 9 (10) 572-9 A study was conducted to examine whether there are significant differences between organic vapor concentrations measured using charcoal tubes with three different configurations: uncovered sample holder (open tube), SKC, and Buck brand covered sample holders. A fractional factorial experimental design was used with the following factors and levels: vapor (n-hexane vs. m-xylene), pump type (pulsating vs. continuous), exposure profile (variable vs. constant), flow rate (30 mL/min vs. 200 mL/min), duration (30 min vs. 80 min), and sample placement (mannequin vs. free hanging). Two of each sampler configuration (six total) were placed in an exposure chamber, and a dynamic test-atmosphere generation system was used to prepare atmospheres containing approximately 12-15 ppm n-hexane or m-xylene with exposure profiles and sampling conducted according to a run sheet generated for the experimental design. A total of 24 runs were completed with six samplers per run, yielding 144 samples that were analyzed by gas chromatography/flame ionization detector. Concentration results for each pair of SKC and Buck covered sample holders were averaged and normalized by dividing by the average result for the open tube sampler from the same run to eliminate the effect of daily variation in chamber concentrations. The resulting ratio of covered sample tube holder and open tube concentrations was used as the response variable. Results of analysis of variance using the general linear model (MINITAB 16) identified statistically significant main effects and/or interactions for pump type, exposure profile, flow rate, and sample holder. However, the magnitude of the effects was generally less than 10%, and overall mean concentration ratios were 0.989 and 1.02 for the Buck and SKC sample holders, respectively. These results show good agreement between covered sample holder results and open tube measurements and demonstrate that exposure assessment errors resulting from the use of covered sorbent tube sample holders for organic vapor monitoring are relatively small (<10%) and not likely to be of practical importance. |
Quartz measurement in coal dust with high-flow rate samplers: laboratory study
Lee T , Lee EG , Kim SW , Chisholm WP , Kashon M , Harper M . Ann Occup Hyg 2012 56 (4) 413-425 A laboratory study was performed to measure quartz in coal dust using high-flow rate samplers (CIP10-R, GK2.69 cyclone, and FSP10 cyclone) and low-flow rate samplers [10-mm nylon and Higgins-Dewell type (BGI4L) cyclones] and to determine whether an increased mass collection from high-flow rate samplers would affect the subsequent quartz measurement by Fourier transform infrared (FTIR) and X-ray diffraction (XRD) analytical procedures. Two different sizes of coal dusts, mass median aerodynamic diameter 4.48 m (Coal Dust A) and 2.33 m (Coal Dust B), were aerosolized in a calm air chamber. The mass of coal dust collected by the samplers was measured gravimetrically, while the mass of quartz collected by the samplers was determined by FTIR (NIOSH Manual of Analytical Method 7603) and XRD (NIOSH Manual of Analytical Method 7500) after one of two different indirect preparations. Comparisons between high-flow rate samplers and low-flow rate samplers were made by calculating mass concentration ratios of coal dusts, net mass ratios of coal dusts, and quartz net mass. Mass concentrations of coal dust from the FSP10 cyclone were significantly higher than those from other samplers and mass concentrations of coal dust from 10-mm nylon cyclone were significantly lower than those from other samplers, while the CIP10-R, GK2.69, and BGI4L samplers did not show significant difference in the comparison of mass concentration of coal dusts. The BGI4L cyclone showed larger mass concentration of 9% compared to the 10-mm nylon cyclone. All cyclones provided dust mass concentrations that can be used in complying with the International Standard Organization standard for the determination of respirable dust concentration. The amount of coal dust collected from the high-flow rate samplers was found to be higher with a factor of 2-8 compared to the low-flow rate samplers but not in direct proportion of increased flow rates. The high-flow rate samplers collected more quartz compared to low-flow rate samplers in the range of 2-10. There was no significant difference between the per cent (%) quartz in coal dust between the FTIR and XRD analyses. The findings of this study indicated that the increased mass of quartz collected with high-flow rate samplers would provide precise analytical results (i.e. significantly above the limit of detection and/or limit of quantification) compared to the mass collected with low-flow rate samplers, especially in environments with low concentrations of quartz or where short sampling times are desired. (2011 The Author.) |
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