OSHA PEL Research Articles

Chemiresistive sensor based on PMMA/rGO composite for detection ammonia

Reduced graphene oxide (rGO) has been a promising material in sensing applications. However, rGO-based sensors have very high recovery time at room temperature (RT). Therefore, various materials combination needs to explored to address this issue. We have developed chemiresistive sensor based on a composite of Poly (methyl methacrylate) (PMMA) and rGO for detection of ammonia (NH3). To prepare more oxidized graphene oxide (GO), peroxidation of graphite oxide (PGO) was used from graphite by following Improved Hummer’s Method (IHM). Due to PGO, synthesized rGO was more conductive and high charge capacity. Synthesized PMMA/rGO composite was drop cast on fabricated interdigitated copper electrodes. Various characterization tools were used for materials confirmation. The chemiresistive sensor based on PMMA/rGO exhibited very good sensing behaviour towards NH3 analytes. The range of detection was 1–10 ppm with very good reproducibility. It was far below the Occupational Safety and Health Administration Permissible Exposer Limit (OSHA PEL) of NH3. A chemiresistive sensor based on PMMA/rGO composite revealed better sensing results than a pristine rGO sensor. The response time and recovery time for rGO based sensor was 122 s and 168 s respectively at 2 ppm of NH3 whereas for PMMA/rGO based sensor it was 50 s and 75 s respectively. Moreover, the PMMA/rGO based sensor exhibited repeatability at 2 ppm for NH3 at RT. This type of PMMA/rGO sensor will be very much useful for the detection of hazardous gases in chemical laboratories and industrial areas.

Size Distributions of Inhalable Particulate Matter and Particle-bound Heavy Metals and Their Potential Occupational Health Risk Related to Informal E-waste Recycling in Thailand

Concentrations and size distributions of atmospheric particulates and particulate-bound heavy metals in different inhalable fractions were studied in working areas during manual dismantling, thermal cutting and cable sheath burning activities. The particulate samples were collected on quartz fiber filters using an eight-stage cascade impactor with flow rate of 28.3 l min-1. Mass concentrations of the particles were measured in each size fraction. Heavy metals bound on the particles were extracted with acid digestion and then analyzed using Atomic Absorption Spectrophotometer. Risk assessment of worker exposure to the particles was determined. The results indicated that the concentrations of ultrafine (dae < 0.43 μm), fine (0.43 < dae < 2.1 μm) and coarse (2.1 < dae < 10 μm) particles were in the ranges of 14.49-62.04, 57.51-120.26 and 153.26–646.99 μg m−3 during manual dismantling, 363.41-1,011.95, 2,105.40-4,899.11 and 1,698.54-7,075.61 μg m−3 during thermal cutting and 364.73-1,694.72, 1,953.33-4,431.41 and 1,385.97-6,126.13 μg m−3 during cable sheath burning, respectively. The concentrations of PM2.1 and PM10 released from these activities did not exceed the OSHA PEL threshold limits. Heavy metals adsorbed on the particles (Fe, Cr, Zn, Cu, Pb, Mn) detected during manual dismantling did not exceed the TWA standard. Concentrations of Cr and Pb during cable sheath burning highly exceeded the standards whereas Pb concentrations during thermal cutting slightly exceeded the standard. The heavy metals released from these recycling activities were more enriched on coarse mode than fine mode. Inhalation exposure to Cr, Pb and Mn posed a potential health risk to the workers.

Assessing Personal PM2.5 Exposure and Respiratory Virus Infections among Farmworkers in the Southeastern United States

BACKGROUND AND AIM: Occupational studies have identified exposure to particulate matter (PM) air pollution as an emerging concern among crop farmworkers, with previous data suggesting that harvesting tasks contribute to the highest occupational PM exposures among this population. Particulates from agricultural dust may be composed of multi-pollutant mixtures of pesticides, heavy metals, mineral silicas, and microbes. Moreover, chronic respiratory conditions, as well as mortality attributable to acute respiratory infections, are notably elevated among crop farmworkers. In the United States, this workforce is comprised primarily of migrant and immigrant populations that face a multitude of social inequities. METHODS: Our pilot study uses personal air samplers to assess occupational exposure to respirable agricultural dust (PM2.5) among a hard-to-reach and vulnerable population of mostly Mexican-American farmworkers harvesting crops in the southeastern US. Participants worked in fernery harvesting, nursery greenhouses, and strawberry harvesting. We conduct prospective, weekly follow-up of participants during influenza season to determine the incidence of acute respiratory symptoms and viral respiratory infections. RESULTS:We collected nasal swab biospecimens from symptomatic participants and tested these samples for SARS-Cov-2 and 20 different respiratory pathogens using a panel array (Biofire). Thus far, we have collected n=30 occupational PM2.5 exposure samples. A majority of occupational PM2.5 exposure levels were above the US EPA limit for annual PM2.5 concentration, with four participants exposed above the OSHA PEL. Of the participants that enrolled in weekly follow-ups (n=20), four participants reported acute respiratory symptoms. Molecular analysis of collected biospecimen were positive for human rhinovirus (n=2), SARS-Cov-2 (n=1), and two samples are pending laboratory analysis. CONCLUSIONS:Follow-up of participants and chemical analysis of PM2.5 filters is ongoing. To our knowledge, this is the first study to assess occupational PM2.5 exposure and incidence of respiratory infections in Southeastern US-hired farmworkers, while characterizing the chemical composition of occupational dust exposures. KEYWORDS: COVID-19, Epidemiology, Exposure assessment, Infectious diseases, Particulate matter, Occupational exposures

Wearable Chemical Sensor Badge

Objectives Under this program, a wearable chemical detection badge capable of detecting and alarming (visual + audible/vibratory) in the presence of relevant concentrations of toxic industrial chemicals (TICs) in air has been developed and demonstrated for ammonia, chlorine, hydrogen sulfide, and nitrogen dioxide. The badge will alarm via one of the user-chosen alarm modes in the presence of ½ Immediately Dangerous to Life or Health (1/2 IDLH) concentrations of these TICs in under 5 minutes. The technology operates in harsh environmental conditions (10-90% RH, -10 – 50 oC) and in the presence of interferents (e.g. smoke, fuels, bleach and diesel exhaust). The active sampling badge consists of a reusable detection device that is used in conjunction with a disposable colorimetric sensor coupon. The sensor badge is unobtrusive and can be worn in the breathing zone of the user with hands-free operation for up to 8 hours on battery power. Results Small prototype devices (2” x 2” x 0.5”) were manufactured based on feedback from expert first responder personnel. Key points from this feedback include: Must have a low false alarm rate; no nuisance level alarms (e.g. PEL)Alarm must be very visible/noticeableMust be small and unobtrusiveData logging would be beneficial for analysis at a later time Prototype devices and associated sensor coupons were tested in the presence of PEL, ½ IDLH, and multiple IDLH concentrations of the target TIC analytes (ammonia, chlorine, hydrogen sulfide, and nitrogen dioxide) under harsh environmental conditions: -10 oC, ~ 90%RH 23 oC, 10% RH/50% RH/90% RH 50 oC, 10% RH/50% RH/90% RHand in the presence of environmental interferents including smoke (burning wood), diesel exhaust, diesel fuel and bleach. Utilizing four interrogation bands of the visible spectrum and combinatorial colorimetric response alarm criteria, the prototype badges performed well with no false positive or false negative alarms due to environmental interferent exposure, nuisance level (PEL) exposure, or harsh environmental conditions. Conclusion/Significance First Responders under duress need a simple, low-cost, rugged device capable of detecting the presence of harmful levels of Toxic Industrial Chemicals (TICs) with high fidelity while avoiding nuisance level alarms (e.g. OSHA PEL) and false alarms due to environmental contaminants (e.g. smoke, fuels, diesel exhaust). This prototype sensor technology fills an unmet need for the first responder and is adaptable for the incorporation of new sensors in the future. Figure 1

Assessment of home care aides’ respiratory exposure to total volatile organic compounds and chlorine during simulated bathroom cleaning: An experimental design with conventional and “green” products

Home care (HC) aide visits to clients’ homes often involve cleaning and disinfecting (C&D) bathrooms. Some ingredients in C&D household products are associated with respiratory illness, including sodium hypochlorite (bleach) and quaternary ammonium compounds (quats). “Green” products may be safer for the environment, however there are limited quantitative evaluations of their respiratory risks. This study assessed airborne concentrations and time profiles of total volatile organic compounds (TVOC) and chlorine generated during typical bathroom cleaning performed by aides using conventional and green products. Aides performed cleaning tasks in a simulated residential bathroom constructed in an environmental air sampling laboratory. A balanced experimental design involved each aide coming to the lab for four visits during which she performed two 20-min cleaning sessions using one of three C&D products (bleach-based, 1–5% sodium hypochlorite by weight; quats-based, 0.1–1% by weight quaternary ammonium compounds; and “green,” 0.05% by weight thymol, a component of botanical thyme oil) or distilled water as a control. TVOC and chlorine direct reading instruments were attached to aides with sample inlets located in the breathing zone. Ten-second averages of TVOC and chlorine gas concentrations and instantaneous peak concentrations were recorded for the sessions’ duration. TVOC concentrations by methods of C&D application (spraying, streaming, wiping) also were evaluated. The study completed 169 air sampling sessions with 22 aides. The quats-based product generated more than twice the average TVOC concentrations (mean = 1,210 ppb) than the bleach-based (mean = 593 ppb) or green (mean = 498 ppb) products. Each product generated TVOC concentrations that rose rapidly within the first few minutes of application. Spraying produced the highest TVOC exposures, wiping the lowest. Thirteen aides (65%) experienced peak chlorine exposures above the OSHA PEL ceiling limit (1 ppm) when using the bleach-based product. HC aides may experience respiratory hazards from use of conventional or green C&D products formulated with bleach or other respiratory irritants and sprayed in small, poorly ventilated spaces typical of bathrooms. Spraying should be avoided.

The Impact of Surficial Biochar Treatment on Acute H2S Emissions during Swine Manure Agitation before Pump-Out: Proof-of-the-Concept

Acute releases of hydrogen sulfide (H2S) are of serious concern in agriculture, especially when farmers agitate manure to empty storage pits before land application. Agitation can cause the release of dangerously high H2S concentrations, resulting in human and animal fatalities. To date, there is no proven technology to mitigate these short-term releases of toxic gas from manure. In our previous research, we have shown that biochar, a highly porous carbonaceous material, can float on manure and mitigate gaseous emissions over extended periods (days–weeks). In this research, we aim to test the hypothesis that biochar can mitigate H2S emissions over short periods (minutes–hours) during and shortly after manure agitation. The objective was to conduct proof-of-the-concept experiments simulating the treatment of agitated manure. Two biochars, highly alkaline and porous (HAP, pH 9.2) made from corn stover and red oak (RO, pH 7.5), were tested. Three scenarios (setups): Control (no biochar), 6 mm, and 12 mm thick layers of biochar were surficially-applied to the manure. Each setup experienced 3 min of manure agitation. Real-time concentrations of H2S were measured immediately before, during, and after agitation until the concentration returned to the initial state. The results were compared with those of the Control using the following three metrics: (1) the maximum (peak) flux, (2) total emission from the start of agitation until the concentration stabilized, and (3) the total emission during the 3 min of agitation. The Gompertz’s model for determination of the cumulative H2S emission kinetics was developed. Here, 12 mm HAP biochar treatment reduced the peak (1) by 42.5% (p = 0.125), reduced overall total emission (2) by 17.9% (p = 0.290), and significantly reduced the total emission during 3 min agitation (3) by 70.4%. Further, 6 mm HAP treatment reduced the peak (1) by 60.6%, and significantly reduced overall (2) and 3 min agitation’s (3) total emission by 64.4% and 66.6%, respectively. Moreover, 12 mm RO biochar treatment reduced the peak (1) by 23.6%, and significantly reduced overall (2) and 3 min total (3) emission by 39.3% and 62.4%, respectively. Finally, 6 mm RO treatment significantly reduced the peak (1) by 63%, overall total emission (2) by 84.7%, and total emission during 3 min agitation (3) by 67.4%. Biochar treatments have the potential to reduce the risk of inhalation exposure to H2S. Both 6 and 12 mm biochar treatments reduced the peak H2S concentrations below the General Industrial Peak Limit (OSHA PEL, 50 ppm). The 6 mm biochar treatments reduced the H2S concentrations below the General Industry Ceiling Limit (OSHA PEL, 20 ppm). Research scaling up to larger manure volumes and longer agitation is warranted.

Setting safer exposure limits for toxic substance combinations

Toxic stimuli (stressors) exposure limits are typically based on single toxic stimuli experiments, but are presently used for both toxic stimuli in isolation and in combination with other toxic stimuli (simultaneous co-exposure or exposures separated in time). In the combination case, typically less of each constituent of the combination is required to cause damage compared to the amount determined from single stressor experiments. Thus, exposure limits based on single toxic stimulus experiments are inadequate for setting limits for stressor combinations.This article presents a recommended simplified approach to improving regulatory exposure limits for toxic stimuli combinations, and a more expansive and expensive alternative to the recommended simplified approach. The recommended approach will partially compensate for the enhanced adverse effects of toxic stimuli combinations relative to adverse effects of toxic stimuli in isolation. The approach covers myriad categories of toxic stimuli reflective of real-life exposures due to lifestyle, iatrogenic, biotoxin, occupational/environmental, and psychosocial/socioeconomic conditions. The proposed approach 1) assumes that all potential toxic stimuli to which an individual might be exposed have the same mechanisms/modes of action on biological mechanisms, and are, thus, indistinguishable by the impacted organism; 2) normalizes the myriad stimuli by converting the doses of toxic stimuli exposures to the respective toxicity reference values (TRV) fractions; 3) sums all the TRVs fractions from these toxic stimuli exposures; and 4) divides all the single substance TRVs by the sum of fractions. While it is an additive approach conceptually, it differs from other additive approaches in the breadth of its inter-category coverage, in order to reflect true inter-category real-life simulation. The newly posited approach does not account for hormetic, antagonistic, or synergistic effects of toxic stimuli in combination. It does not adjust for 1) low-dose toxicants with adverse effects that have been under-reported, or 2) exposure limits like the Occupational Safety and Health Administration - Permissible Exposure Limits (OSHA PELs) that are orders of magnitude above levels shown by published single toxic stimuli studies to have caused adverse effects. Practical considerations for the application of this approach are presented.

Inkjet-printed thin films on flexible substrate for electro-optical detection of methylamine gas

Methylamine (MA) is highly toxic even at low concentrations. The current U.S.A. Occupational Safety and Health Administration Permissible Exposure Limit (OSHA PEL) is 10 ppm in the gas phase. In this study we have developed low-cost, robust and stable copper sulphide film on flexible plastic and paper substrate. The sensitivity of the film towards MA as a function of print density is studied at room temperature. The electrical and colorimetric response of the sensing films is optimized with respect to print density. The performance parameters of the sensing films including, sensitivity, a lower limit of detection (LOD), selectivity and onset time of detection are determined. X-ray photoelectron spectroscopy is employed for chemical characterization of the sensing film. It is demonstrated that copper sulphide films register either change in resistance or colour when exposed to methylamine in a range of 1 to 100 ppm. A LOD of 1 ppm is achieved which is lower than the current OSHA PEL. The optimized sensing film has shown over three and six orders of magnitude change in resistance when exposed to 10 ppm and 500 ppm of MA respectively. The low cost, room temperature operation, electrical and colorimetric response of the developed sensing films make them promising candidates to be used for medical diagnostics as well as industrial use for example in chemical industry and environmental applications.

Ionic Liquid‐based Microchannels for Highly Sensitive and Fast Amperometric Detection of Toxic Gases

AbstractIonic liquid (IL)‐based microchannels sensors have been fabricated and employed for the detection of toxic ammonia (NH3) and hydrogen chloride (HCl) gases, with enhanced sensitivity and response times compared to conventional electrodes. Electrochemical techniques were employed to understand the behaviour of these highly toxic gases in two ionic liquids, [C4mpyrr][NTf2] and [C2mim][NTf2], on a gold modified microchannels electrode. The limits of detection (LODs) obtained in [C4mpyrr][NTf2] for NH3 (3.7 ppm) and in [C2mim][NTf2] for HCl (3.6 ppm) were lower than the current Occupational Safety and Health Administration Permissible Exposure Limit (OSHA PEL) for the two gases (25 ppm for NH3 and 5 ppm for HCl). The response time of the sensor is 15 s with a sensitivity of 143 nA ppm−1 and 14 nA ppm−1 for HCl and NH3, respectively. These results demonstrate the superiority of IL‐based microchannels sensors for detecting toxic gases, when compared to commercially available sensors or traditional IL‐based sensor designs, where high sensitivity or fast response time is still a challenge.

A meta-analysis of airborne asbestos fiber concentrations from work with or around asbestos-containing floor tile.

In this meta-analysis, exposures to airborne asbestos during work with or around floor tiles were characterized according to several variables: study, sample type, activity, and task. Personal breathing zone, bystander, and area sample exposure concentrations were differentiated and compared against current occupational exposure limits to asbestos. In total, 22 studies, including 804 personal, 57 bystander, and 295 area samples, were included in the analysis. The arithmetic mean airborne fiber concentrations were 0.05, 0.02, and 0.01f/cm3 for personal, bystander, and area samples, respectively. Arithmetic mean time-weighted-average fiber concentrations over an 8-h working day were 0.02 and 0.01f/cm3 for personal and bystander samples, respectively. Phase contrast microscopy (PCM) personal airborne fiber concentrations were highest for maintenance activities, followed by removal and installation. Tasks that involved buffing or burnishing, scoring or snapping, and scraping or lifting had the highest personal PCM concentrations, while stripping floor tile and removing it with chemical solvent had the lowest concentrations. Exposures associated with handling asbestos floor tiles, under working conditions normally encountered, do not generally produce airborne concentrations at levels that exceed the current OSHA PEL nor do they appear to approach the threshold cumulative asbestos dose concentrations that have been previously associated with an increased risk of asbestos-related disease.

Retrospective Assessment of Respirable Quartz Exposure for a Silicosis Study of the Industrial Sand Industry

In 2016, the OSHA PEL for crystalline silica was reduced, renewing interest in evaluating risk of silicosis from occupational exposures. The industrial sand industry, which deals with high-purity quartz sands, is the setting for a current epidemiologic investigation of silicosis risk and progression. In support of that investigation, respirable quartz (RQ) exposures were retrospectively estimated for 67 workers with silicosis and 167 matched control workers from 21 industrial sand plants, in which some started work as early as 1929. A job exposure matrix (JEM) was constructed by integrating a modern (post-1970) RQ exposure database containing more than 40000 measurements with archival particle count exposure data from a 1947 survey. A simulation algorithm was used to develop a conversion factor to convert the archival particle count data into modern measures of RQ by randomly generating 100000 virtual dust particles of varying diameters corresponding to the size distributions of 14 archival particle size distribution samples. The equivalent respirable mass and particle counts of the virtual particles were calculated, totalled, and ratioed to derive the conversion factor. The JEM was integrated with individual job histories to calculate average and cumulative exposure for each case and control. Multiple exposure estimates were derived for unprotected exposures as well as for exposures adjusted for estimated respiratory protective equipment use and efficiency. The mean of the count to respirable mass conversion factors derived from 14 archival particle size samples was 157 µg m-3 per mppcf (SD: 42; range: 96-263) with no statistical difference across process areas (drying, screening, vibrating, binning, bulk loading, bagging), P = 0.29. The JEM demonstrated an industry-wide decrease in prevailing exposures to RQ of up to about 2 orders of magnitude from the distant (1929) to the recent (2012) past. Unadjusted cumulative exposures for cases and controls were statistically different (P < 0.001) with respective medians (range) of 3764 µg m-3 year (221-25121) and 1595 µg m-3 year (0-16446). Adjustment of exposure for use of respiratory protection showed modest reductions in estimated exposure: median adjusted cumulative exposures assuming a protection factor of 5 were 86% and 77% of the unadjusted values for cases and controls, respectively. The industrial sand industry offers a unique setting for examination of silicosis risk because of the high silica content of industrial sand and a long history of radiographic silicosis surveillance of industry workers. However, the great majority of silicosis cases in this industry are found among former workers and are associated with exposures occurring in the distant past, which necessitates extensive retrospective exposure assessment and increases the likelihood of exposure misclassification. Nonetheless, the estimated cumulative exposures for silicosis cases and controls in this work were significantly different, with the median cumulative exposure for cases being more than twice that of their matched controls.

Determinants of Respirable Crystalline Silica Exposure among Sand-stone Workers

Objective: Our aim was to determine the occupational exposure level for respirable crystalline silica (RCS) and respirable dust (RD) among sandstone workers. Materials and methods: This study was a descriptive analysis of the occupational exposure to respirable crystalline silica (RCS) and respirable dust (RD), utilizing personal air sampling from the breathing zone. The samples were collected throughout the 8-h working day: 88 samples were collected from workers performing stone cutting in mines and at home (wetting system), as well as stone chiseling and stone carving (22 samples each). Twenty-two samples were collected of the RD using the Gravimetric method (NIOSH 600), while for occupational exposure, the level of RCS was measured using a NIOSH7601 spectrophotometer. Results: Sand-stone workers had a geometric mean occupational exposure to RD of GM 1.84 mg/m3. The highest respiratory dust (RD) concentration (2.83 mg/m3) was found among the stone carvers. Those cutting stone at the mines had the next highest GM (2.65 mg/m3), while the lowest occupational exposure was seen among those chiseling stone(GM 0.9 mg/m3). The occupational exposure to RCS had a geometric mean of 0.10 mg/m3. The highest exposure group was for those cutting stone in the mines (GM = 0.14 mg/m3) followed by those carving stone (GM = 0.10 mg/m3). The moderate exposure group was for those chiseling stone (GM 0.05 mg/m3 ) followed by those cutting stone at home (GM = 0.03 mg/m3). The low exposure group had a GM of 0.03 mg/m3 for RCS. We found the quartz silica concentrations of the sandstone used in this area high (≤90%) as was the percentage of quartz silica in the airborne particulates for stone carving (≤71.4% by volume). Conclusion: The stone cutting in mines group and the stone carving group reached occupational exposure limits to RCS which exceeded the 0.05 mg/m3 OSHA PEL. It is essential to prevent such high exposure through engineering controls, by adapting tools and implementing medical surveillance. All groups had a RCS occupational exposure which would warrant medical surveillance as each group exceeded the OSHA action level of 0.0025 mg/m3.

Assessment of noise in the airplane cabin environment.

To measure sound levels in the aircraft cabin during different phases of flight. Sound level was measured on 200 flights, representing six aircraft groups using continuous monitors. A linear mixed-effects model with random intercept was used to test for significant differences in mean sound level by aircraft model and across each flight phase as well as by flight phase, airplane type, measurement location and proximity to engine noise. Mean sound levels across all flight phases and aircraft groups ranged from 37.6 to >110 dB(A) with a median of 83.5 dB(A). Significant differences in noise levels were also observed based on proximity to the engines and between aircraft with fuselage- and wing mounted engines. Nine flights (4.5%) exceeded the recommended 8-h TWA exposure limit of 85 dB(A) by the NIOSH and ACGIH approach, three flights (1.5%) exceeded the 8-h TWA action level of 85 dB(A) by the OSHA approach, and none of the flights exceeded the 8-h TWA action level of 90 dB(A) by the OSHA PEL approach. Additional characterization studies, including personal noise dosimetry, are necessary to document accurate occupational exposures in the aircraft cabin environment and identify appropriate response actions. FAA should consider applying the more health-protective NIOSH/ACGIH occupational noise recommendations to the aircraft cabin environment.

Assessment of dust exposure in a steel plant in the eastern coast of peninsular Malaysia.

Steel manufacturing produces dust, fumes, and pollutant gases that may give adverse health effects to the respiratory function of workers. Improper occupational hygiene practice in the workplace will affect both workers wellbeing and productivity. To assess the level of particulate matter [(PM2.5, PM10, and Total Particulate Matter (TPM)], and trace metal dust concentrations in different sections of a steel plant and compare with the occupational exposure values. The work environmental parameters of the particulate matters were evaluated using Indoor Air Quality, while metal dust concentrations were measured using portable personal air sampler. A total of 184 personal samples were randomly collected from workers in three major sections; steel making plant, direct reduced plant, and support group. Trace metal dust concentrations were subjected to wet mineral acid mixture digestion and analysed by atomic absorption spectrophotometer (AAS). The overall average PM2.5 concentration observed was varied according to the section: steel making plant was 0.18 mg/m3, direct reduced iron plant was 0.05 mg/m3, and support plant was 0.05 mg/m3. Average PM 10 concentration in steel making shop (SMS) plant, direct reduced (DR) plant, and support plant were 0.70 mg/m3, 0.84 mg/m3, and 0.58 mg/m3, respectively. The average TWA8 of trace metal dusts (cobalt and chromium) in all the sections exceeded 1 to 3 times the ACGIH prescribed values, OSHA PELs, NIOSH RELs as well as USECHH OSHA, whereas TWA8 concentration of nickel for each section did not exceed the occupational exposure values. The average PM2.5, PM10 and TPM did not exceed the prescribed values, while average trace metal dust concentration TWA8 for cobalt and chromium in all plants exceeded occupational exposure prescribed values. However, the nickel found did not exceed the prescribed values in all the plants except for NIOSH RELs.

Electrochemical Detection of Low-Concentration Ammonia Gas on Miniaturised Electrodes in Room Temperature Ionic Liquids

The detection of ammonia (NH3) gas at low concentrations is of great importance due to its use in a wide range of industries e.g. the oil and gas industry, fertilizer industry, refrigeration industry1 and due to its high toxicity. Concentrations as low as 500 ppm can be lethal, and the current (USA) Occupational Health and Safety Permissible Exposure Limit (OSHA PEL) is 25 ppm in the gas phase. There are commercially available electrochemical gas sensors to monitor ammonia, mostly based on amperometric gas sensors (AGSs). However one problem with AGSs is that their solvent/electrolyte combinations are typically water/sulphuric acid, and can dry-up quickly, thus making the lifetime of these sensors very limited. Room Temperature Ionic Liquids (RTILs) have been attracting a great attention as replacement electrolytes in AGSs2 due to their unique physical properties such as wide electrochemical windows, high intrinsic conductivity, low volatility and negligible vapor pressure, high chemical and thermal stability and their ability to dissolve a wide range of compounds. Importantly, they do not evaporate when exposed to a high gas flow, and can function in hot and dry environments. In our work, we are investigating commercially available thin-film metal electrode surfaces as new sensing surfaces, consisting of three electrodes that are incorporated onto a small area on an inert substrate. Their small size means that only a few microliters RTIL solvent needed, and the small amount of inert metal required (e.g. platinum) minimizes the overall cost of the sensor. Four different techniques will be employed for ammonia oxidation: linear sweep voltammetry (LSV), differential pulse voltammetry (DPV) and square wave voltammetry (SWV), and potential-step chronoamperometry (PSC) over the concentration range of 10-100 ppm NH3. The results on commercially available Pt thin-film electrodes, screen-printed electrodes, and microarray thin-film electrodes will be compared to “ideal” Pt microdisk electrodes. Calibration curves (current vs. concentration) for all voltammetric techniques on all four surfaces will be presented, showing excellent linearity with increased concentrations of NH3. The limits of detection found on all four surfaces for all four techniques are in the range of ca. 2-5 ppm, much lower than minimum exposure limit (25 ppm) for NH3. These results are highly encouraging and suggest that RTILs and low-cost miniaturised electrodes can be combined in sensor devices to detect ammonia gas at low ppm concentrations.

Comparison between active (pumped) and passive (diffusive) sampling methods for formaldehyde in pathology and histology laboratories

ABSTRACTThis study was to determine occupational exposures to formaldehyde and to compare concentrations of formaldehyde obtained by active and passive sampling methods. In one pathology and one histology laboratories, exposure measurements were collected with sets of active air samplers (Supelco LpDNPH tubes) and passive badges (ChemDisk Aldehyde Monitor 571). Sixty-six sample pairs (49 personal and 17 area) were collected and analyzed by NIOSH NMAM 2016 for active samples and OSHA Method 1007 (using the manufacturer's updated uptake rate) for passive samples. All active and passive 8-hr time-weighted average (TWA) measurements showed compliance with the OSHA permissible exposure limit (PEL-0.75 ppm) except for one passive measurement, whereas 78% for the active and 88% for the passive samples exceeded the NIOSH recommended exposure limit (REL-0.016 ppm). Overall, 73% of the passive samples showed higher concentrations than the active samples and a statistical test indicated disagreement between two methods for all data and for data without outliers. The OSHA Method cautions that passive samplers should not be used for sampling situations involving formalin solutions because of low concentration estimates in the presence of reaction products of formaldehyde and methanol (a formalin additive). However, this situation was not observed, perhaps because the formalin solutions used in these laboratories included much less methanol (3%) than those tested in the OSHA Method (up to 15%). The passive samplers in general overestimated concentrations compared to the active method, which is prudent for demonstrating compliance with an occupational exposure limit, but occasional large differences may be a result of collecting aerosolized droplets or splashes on the face of the samplers. In the situations examined in this study the passive sampler generally produces higher results than the active sampler so that a body of results from passive samplers demonstrating compliance with the OSHA PEL would be a valid conclusion. However, individual passive samples can show lower results than a paired active sampler so that a single result should be treated with caution.

Sensors for highly toxic gases: methylamine and hydrogen chloride detection at low concentrations in an ionic liquid on Pt screen printed electrodes.

Commercially available Pt screen printed electrodes (SPEs) have been employed as possible electrode materials for methylamine (MA) and hydrogen chloride (HCl) gas detection. The room temperature ionic liquid (RTIL) 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C2mim][NTf2]) was used as a solvent and the electrochemical behaviour of both gases was first examined using cyclic voltammetry. The reaction mechanism appears to be the same on Pt SPEs as on Pt microelectrodes. Furthermore, the analytical utility was studied to understand the behaviour of these highly toxic gases at low concentrations on SPEs, with calibration graphs obtained from 10 to 80 ppm. Three different electrochemical techniques were employed: linear sweep voltammetry (LSV), differential pulse voltammetry (DPV) and square wave voltammetry (SWV), with no significant differences in the limits of detection (LODs) between the techniques (LODs were between 1.4 to 3.6 ppm for all three techniques for both gases). The LODs achieved on Pt SPEs were lower than the current Occupational Safety and Health Administration Permissible Exposure Limit (OSHA PEL) limits of the two gases (5 ppm for HCl and 10 ppm for MA), suggesting that Pt SPEs can successfully be combined with RTILs to be used as cheap alternatives for amperometric gas sensing in applications where these toxic gases may be released.

Screening-level human health risk assessment of toluene and dibutyl phthalate in nail lacquers

Toluene and dibutyl phthalate (DBP) are found in many consumer products, including cosmetics, synthetic fragrances, and nail polish. In 2012, the California Environmental Protection Agency evaluated 25 nail products and found that 83% of the products that claimed to be toluene-free contained toluene at concentrations ranging up to 190,000 ppm, and 14% of the products that claimed to be DBP-free contained DBP at concentrations ranging up to 88,000 ppm. We conducted a preliminary, screening-level analysis of the potential toluene and DBP-related health risks to consumers and professionals based on the medium and maximum concentrations of toluene and DBP presented in the 2012 report and evaluated dermal and inhalation exposure to a salon patron, nail technician, and home user. We concluded that the maximum toluene concentration for the technician and home user scenarios exceeded the California MADL, but the estimated air concentrations did not exceed the Federal or Cal OSHA PEL. The MADL for DBP was exceeded for all user scenarios at both the median and maximum concentrations. Using these highly conservative assumptions, exposures above regulatory limits could possibly occur during routine use of nail products; further research is needed in order to evaluate potential human health risks.

Flavoring exposure in food manufacturing.

Flavorings are substances that alter or enhance the taste of food. Workers in the food-manufacturing industry, where flavorings are added to many products, may be exposed to any number of flavoring compounds. Although thousands of flavoring substances are in use, little is known about most of these in terms of worker health effects, and few have occupational exposure guidelines. Exposure assessment surveys were conducted at nine food production facilities and one flavor manufacturer where a total of 105 area and 74 personal samples were collected for 13 flavoring compounds including five ketones, five aldehydes, and three acids. The majority of the samples were below the limit of detection (LOD) for most compounds. Diacetyl had eight area and four personal samples above the LOD, whereas 2,3-pentanedione had three area samples above the LOD. The detectable values ranged from 25-3124 ppb and 15-172 ppb for diacetyl and 2,3-pentanedione respectively. These values exceed the proposed National Institute for Occupational Safety and Health (NIOSH) recommended exposure limit for these compounds. The aldehydes had the most detectable samples, with each of them having >50% of the samples above the LOD. Acetaldehyde had all but two samples above the LOD, however, these samples were below the OSHA PEL. It appears that in the food-manufacturing facilities surveyed here, exposure to the ketones occurs infrequently, however levels above the proposed NIOSH REL were found. Conversely, aldehyde exposure appears to be ubiquitous.

History and evolution of warning labels for automotive friction products

There have been claims over the years that asbestos-containing product manufacturers did not sufficiently warn end users early enough regarding the potential health hazards associated with their products (1930s–1990s). To address this issue, we compared the content of the warnings associated with asbestos-containing friction products (brakes, clutches, and gaskets) manufactured by the US automotive industries to what was expected by regulatory agencies during the time period in which an understanding of asbestos health hazards was being developed. We ended our evaluation around 1990, since asbestos-containing manufacturer supplied automotive products were functionally removed from commerce by 1985 in the United States. We assessed the warnings issued in users’ manuals, technical service bulletins, product packaging materials, and labels placed on products themselves. Based on our evaluation, regulatory agencies had no guidelines regarding specific warning language for finished friction products, particularly when a product contained encapsulated asbestos fibers (i.e., modified by a bonding agent). Even today, federal regulations do not require labeling on encapsulated products when, based on professional judgment or sampling, user exposure is not expected to exceed the OSHA PEL. We concluded that, despite limited regulatory guidance, the US automotive industry provided adequate warnings with regards to its friction products.