OSHA Permissible Exposure Limit Research Articles

Gasoline Generators and their Effects on Air Quality of Some Selected Business Centers in Tertiary Institutions in Rivers State

This study considered gasoline generators and their effects on air quality of some selected business centers in tertiary institutions in Rivers State. Air quality monitor was positioned 1.5m above the floor to determine the concentration levels of CO, CO2 and O2. The measurements were done on a daily for a period of three weeks. At FCE (T), Omoku, the mean concentration values of CO for Business and Institution’s generators were 109.2ppm and 62.3ppm; CO2 283.6ppm and 27.4ppm and O2 185.8% and 192.1% respectively. At IAUE, Port-Harcourt, CO for Business and Institution’s generators had mean concentration values of 144.7ppm and 89.6ppm; CO2 210.9 ppm and 188.8ppm, and for O2, 225.4% and 239.2% respectively. Similarly, for RSU, Port-Harcourt, the mean concentration of CO for Business and Institution’s generators were 144.8ppm and 84.5ppm; CO2 171.1ppm and 124.ppm; and for O2, 196.8% and 164.3%. respectively. CEAP, Port-Harcourt, CO had mean concentration values of 215.3ppm and light 92.2ppm, CO2 226.2ppm and 109.2ppm, whileO2 mean concentration values of 120.1% and 198.2% respectively. The concentration levels of CO, CO2 for business generators were much higher compared to when Institutions’ generators were used. The mean values of CO concentrations for the selected institutions for the period under study were higher than OSHA permissible exposure limit (PEL) of 50ppm (55mg/m3), NIOSH recommended exposure limit (REL) of 35ppm (40 mg/m3) and ACGIH threshold limit value (TLV) of 25ppm (28.6mg/m3), while that of CO2 concentration levels were less than OSHA’s established permissible limit of 5000ppm, and American Conference of Governmental Industrial Hygienists(ACGIH) threshold limit value (TLV) of 25ppm. It was also observed that as the concentrations of CO and CO2 increase, the O2 levels also decrease. It is therefore, very important to state that tertiary institutions’ managements in Nigeria should consider the provision of regular power supply on

Occupational exposure to asbestos in the steel industry (1972-2006).

Historically, the use of asbestos in steelmaking has been limited to a few applications. Due to its physical and chemical properties, asbestos was not necessary or suitable for most purposes in a steel mill. The few applications where asbestos were used (i.e., certain gaskets, brakes, protective cloth, refractory materials, insulation materials, and hot top products) were replaced by alternative materials as they became available. We discuss historical uses of asbestos in steel manufacturing and the associated airborne asbestos concentrations collected at sixteen U.S. Steel facilities between 1972 and 2006. A total of 495 personal airborne asbestos samples from the U. S. Steel industrial hygiene records were analyzed across four time periods corresponding to changes in the OSHA permissible exposure limit (PEL) for asbestos. 68% of the samples (n = 337) were considered representative of an employee's workday. The remaining samples (n = 158) represented task samples. Samples were grouped by facility, department, and job category within the four time periods. The average fiber concentrations measured for each facility and department over time were below the contemporaneous OSHA PEL. The mean representative workday asbestos air concentration from 1972 and 1975 was 1.09 f/cc. The mean representative workday concentration decreased to 0.13 f/cc between 1976 and 1985, then decreased again to 0.02 f/cc between 1986 and 1993 and 0.03 f/cc between 1994 and 2006. For task samples, the mean air concentration from 1972 to 1975 was 3.29 f/cc. The mean task sample concentration decreased to 0.48 f/cc between 1976 and 1985, then decreased again to 0.01 f/cc between 1986 and 1993 and 0.03 f/cc between 1994 and 2006. Only eleven out of the 495 samples (2.2%), for both task and representative workday samples, were in exceedance of the contemporaneous PEL(as an 8-hour TWA), ten of which occurred prior to 1978. Eight of these eleven PEL exceeding samples were task samples. Of the remaining three representative workday samples, two had unknown sampling times. This paper presents an analysis of all the available personal sampling data for airborne asbestos across 16 facilities of the U.S. Steel Corporation between 1972 and 2006. This dataset has previously never been publicly shared or analyzed. It represents one of the more complete industrial hygiene datasets from a corporation to be presented in a scientific journal and, due to the similarities in the processesat each mill, it should reflect analogous exposures throughout the steelmaking industry in the United States. One of the benefits of presenting these data is that it also provides insight into where asbestos-containing materials (ACMs) were used in the steel making process. This is just one example of a large firm that released information that had previously remained in file cabinets for decades. We believe that another benefit of publishing this paper is that it may encourage the largest firms in industry to assemble and analyze their industrial hygiene data to benefit the occupational hygiene, medical, and epidemiology communities. This can support future epidemiology studies and improve the design of future industrial hygiene programs.

11 Raman Spectroscopy to Monitor Short-Term and Transient RCS Aerosol Exposure

Abstract Exposure to respirable crystalline silica (RCS) at concentrations at or below the OSHA permissible exposure limit (PEL) of 50 µg/m3 are challenging to monitor with the current industry standard methods X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR). In particular, the assessment of short-term or transient exposure to RCS concentration calls for more sensitive analytical methods that are able to quantify RCS from low dust amounts within the desired uncertainty limits. Here, we present results from a verification study of a Raman spectroscopy-based Identifier system including dedicated respirable air samplers (badges) for the collection of airborne RCS. The air sampling badges concentrate the analyte onto dedicated 1 mm2 collection membranes suitable for direct-on-filter (DOF) Raman analysis. The sampling efficiency of the badges was assessed experimentally and shown to closely adapt the respirable sampling convention according to ISO 7708, with a low sampler bias of < 10%. Using a fully automated Raman-based bench-top reader, the limit of detection (LOD) and limit of quantification (LOQ) were determined empirically with 0.1 and 0.3 µg, respectively. The limits are approx. an order of magnitude lower than for the current industry standards and enable the relevant monitoring of short-term or transient exposure of workers to RCS, as they typically occur in construction or mining environments. The optimized workflow of the Identifier system makes it an attractive alternative to the industry standards XRD and FTIR, with the opportunity to monitor exposure down to the action level.

The Evaluation of Worker Exposure to Airborne Silica Dust During Five OSHA Table I Construction Tasks.

Fifty-one (51) personal silica air samples were collected over 13 days on 19 construction employees while they performed five different construction tasks found in the Occupational Safety and Health Administration's (OSHA) respirable crystalline silica standard for construction, Table 1, which specifies engineering, work practice, and respiratory protection controls that employers can use in lieu of exposure monitoring to adhere to the standard. The average construction task time was 127 min (range: 18-240 min) with a mean respirable silica concentration of 85 μg m-3 (standard deviation [SD] = 176.2) for all 51 measured exposures. At least one OSHA-specified silica dust control measure was used during all 51 samples collected. The mean silica concentrations for the five tasks were: core drilling 11.2 μg m-3 (SD = 5.31 μg m-3), cutting with a walk-behind saw 126 μg m-3 (SD = 115 μg m-3), dowel drilling 99.9 μg m-3 (SD = 58.7 μg m-3), grinding 172 μg m-3 (SD = 145 μg m-3), and jackhammering 23.2 μg m-3 (SD = 5.19 μg m-3). Twenty four of 51 (47.1%) workers were exposed above the OSHA Action Level (AL) of 25 μg m-3 and 15 of 51 (29.4%) were exposed above the OSHA Permissible Exposure Limit (PEL) of 50 μg m-3 when exposures were extrapolated to an 8-h shift. When silica exposures were extrapolated to 4 h, 15 of 51 (29.4%) of workers sampled were exposed over the OSHA AL and 8 of 51 (15.7%) were exposed over the OSHA PEL. A total of 15 area airborne respirable crystalline silica samples were collected on days where the personal task-based silica samples were taken, with an average sampling time of 187 min. Of the 15 area respirable crystalline silica samples, only four were greater than the laboratory reporting limit of 5 μg m-3. The four area silica samples with reportable concentrations revealed background silica concentrations of 23 μg m-3, 5 μg m-3, 40 μg m-3, and 100 μg m-3. Odds ratios were used to analyze the apparent association between dichotomous background construction site exposures to respirable crystalline silica (detectable or not detectable), and personal exposure category (over or not over the OSHA AL and PEL) when exposure times were extrapolated to 8 h. The associations were strongly positive and significant between detectable background exposures and personal overexposures for workers conducting the five Table 1 tasks with engineering controls in place. The results of this study suggest that exposure to hazardous levels of respirable crystalline silica may be present even when OSHA-specified engineering controls are implemented. The current study findings also suggest that background construction site silica concentrations may potentially cause task-based overexposures, even when the OSHA Table 1 control methods have been put in place.

Characterization of Occupational Exposures to Respirable Silica and Dust in Demolition, Crushing, and Chipping Activities.

Exposures to respirable crystalline silica (RCS) and respirable dust (RD) were investigated during demolition, crushing, and chipping at several Massachusetts construction sites. Personal breathing zone samples (n = 51) were collected on operating engineers working at demolition and crushing sites, laborers performing miscellaneous tasks at demolition sites, crushing machine tenders at crushing sites, and chipping workers at substructure bridge repair sites. Area samples (n = 33) were collected at the perimeter of demolition and crushing sites to assess potential bystanders' exposures. Exposures 'with' and 'without' the use of dust suppression methods were compared when possible. RD samples were analyzed for crystalline silica content with Fourier Transform Infrared Spectrophotometry (FT-IR) according to the National Institute for Occupational Safety and Health (NIOSH) Method 7602. Statistical analyses of the exposure data were performed in SAS version 9.4. Chipping workers had the highest exposure levels [the geometric mean (GM) time-weighted average (TWA) for RCS was 527 µg/m3 and the GM for RD was 4750 µg/m3]. The next highest exposures were among crushing machine tenders (RCS GM of 93.3 µg/m3 and RD GM of 737.6 µg/m3), while laborers and operating engineers had the lowest exposures (RCS GM of 17.0 and 6.2 µg/m3, respectively). Personal 8-h TWA RCS exposures were higher than the new OSHA permissible exposure limit (PEL) of 50 µg/m3 for 80% of samples collected on chipping workers (n = 31) and 50% of samples collected on crushing machine tenders (n = 8). Operating engineers (n = 9) and laborers (n = 3) had RCS exposures lower than OSHA PEL. The highest concentrations measured would have exceeded the PEL within 15 min chipping and within 2 h of crushing with no further exposure. Chipping workers' RCS exposures were higher than OSHA PEL even when they were adjusted to account for the assigned protection factor of the half-face N95 cartridge respirators used during chipping. Exposures of crushing tenders were reduced to levels under the OSHA PEL when a water spraying system in crushing machines was utilized, but not when a water cannon machine was used. Area samples at demolition and crushing sites indicate overall lower exposures than the PEL, however, bystander workers at crushing sites could be exposed to higher levels compared to demolition sites. Real-time dust monitoring during demolition indicate very high short-term peak exposures. Controlling or reducing crystalline silica exposures to levels under the new OSHA PEL of 50 µg/m3 remains challenging for chipping workers and crushing machine tenders. Even with the use of dust suppression controls, respiratory protection may be required for various tasks.

High-Resolution Metabolomics Study of Occupational Exposure to Trichloroethylene

Introduction: Trichloroethylene (TCE) is a common water contaminant and continues to be used in the workplaces of many developing countries. It causes kidney cancer and possibly non-Hodgkin lymphoma and liver cancer. However, the underlying pathophysiology of TCE-induced cancer is not well understood. To evaluate biological responses to TCE, we conducted a cross-sectional molecular epidemiology study of workers exposed to TCE and unexposed controls and applied non-targeted metabolomics analysis.Methods: We studied 80 healthy workers that used TCE and 95 comparable unexposed controls in Guangdong, China. The TCE-exposed workers had a median 8-hour time weighted average personal air exposure of 12 ppm (range: 0.4 to 230 ppm), with almost all workers having exposure under the current U.S. OSHA Permissible Exposure Limit of 100 ppm. Metabolomics analysis of plasma samples was conducted by ultra-high resolution mass spectrometryResults: Metabolic features associated with TCE exposure included known TCE metabolites and additional unidentified chlorinated compounds. TCE exposure was also associated with multiple alterations in endogenous metabolism, including changes in purine catabolism and decreases in sulphur amino acid and bile acid biosynthesis pathways. Specific metabolite associations with TCE exposure included uric acid, glutamine, cystine, methylthioadenosine, taurine and chenodeoxycholic acid, consistent with immunosuppressive, hepatotoxic and nephrotoxic effects that have been related to TCE. There were also correlations between multiple metabolites and additional exposure, immunologic, and nephrotoxic biomarkers that had been measured previously.Conclusion: Untargeted high-resolution metabolomics correlated occupational exposure to TCE with internal dose and metabolic responses, providing new insights into molecular mechanisms of TCE-related disease.

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.

Characterizing and Communicating Risk with Exposure Reconstruction and Bayesian Analysis: Historical Locomotive Maintenance/Repair Associated with Asbestos Woven Tape Pipe Lagging.

Our reconstructed historical work scenarios incorporating a vintage 1950s locomotive can assist in better understanding the historical asbestos exposures associated with past maintenance and repairs and fill a literature data gap. Air sampling data collected during the exposure scenarios and analyzed by NIOSH 7400 (PCM) and 7402 (PCME) methodologies show personal breathing zone asbestiform fiber exposures were below the current OSHA exposure limits for the eight-hour TWA permissible exposure limit (PEL) of 0.1 f/cc (range <0.007-0.064 PCME f/cc) and the 30-minute short-term excursion limit (EL) of 1.0 f/cc (range <0.045-0.32 PCME f/cc) and orders of magnitude below historic OSHA PEL and ACGIH TLVs. Bayesian decision analysis (BDA) results demonstrate that the 95th percentile point estimate falls into an AIHA exposure category 3 or 4 as compared to the current PEL and category 1 when compared to the historic PEL. BDA results demonstrate that bystander exposures would be classified as category 0. Our findings were also significantly below the published calcium magnesium insulations exposure range of 2.5 to 7.5 f/cc reported for historic work activities of pipefitters, mechanics, and boilermakers. Diesel-electric locomotive pipe systems were typically insulated with a woven tape lagging that may have been chrysotile asbestos and handled, removed, and reinstalled during repair and maintenance activities. We reconstructed historical work scenarios containing asbestos woven tape pipe lagging that have not been characterized in the published literature. The historical work scenarios were conducted by a retired railroad pipefitter with 37 years of experience working with materials and locomotives.

Exposure to airborne asbestos in thermal power plants in Mongolia.

Coal-fired thermal power plants (TPPs) in Mongolia use various types of asbestos-containing materials (ACMs) in thermal insulation of piping systems, furnaces, and other products. To investigate the occupational exposure of insulation workers to airborne asbestos in Mongolian power plants. Forty-seven air samples were collected from four power plants in Mongolia during the progress of insulation work. The samples were analyzed by phase contrast microscopy (PCM) and transmission electron microscopy (TEM). The average phase contrast microscopy equivalent (PCME) asbestos fiber concentration was 0·93 f/cm(3). Sixteen of the 41 personal and one of the area samples exceeded the United States Occupational Safety and Health Administration (US OSHA) short-term exposure limit of 1·0 f/cm(3). If it is assumed that the short-term samples collected are representative of full-shift exposure, then the exposures are approximately 10 times higher than the US OSHA 8-hour permissible exposure limit of 0·1 f/cm(3). Power plant insulation workers are exposed to airborne asbestos at concentrations that exceed the US OSHA Permissible Exposure Limit. Action to mitigate the risks should be taken in Mongolia.

Asbestos exposure among transmission mechanics in automotive repair shops.

Asbestos has been used in a broad variety of industrial products, including clutch discs of the transmission system of vehicles. Studies conducted in high-income countries that have analyzed personal asbestos exposures of transmission mechanics have concluded that these workers are exposed to asbestos concentrations in compliance with the US Occupational Safety and Health Administration (US OSHA) occupational standards. Clutch facings are the friction component of clutch discs. If clutch facings are sold separated from the support, they require manipulation before installation in the vehicle. The manipulation of asbestos containing clutch facings is performed by a group of mechanics known as riveters, and includes drilling, countersinking, riveting, sanding, and occasionally grinding, tasks that can potentially release asbestos fibers, exposing the mechanics. These manipulation activities are not reported in studies conducted in high-income countries. This study analyzes personal asbestos exposures of transmission mechanics that manipulate clutch facings. Air sampling campaigns in two transmission repair shops (TRS) were conducted in November 2012 and July 2013 in Bogotá, Colombia. Four workers employed in these TRS were sampled (i.e. three riveters and one supervisor). Personal samples (n = 39), short-term personal samples (n = 49), area samples (n = 52), blank samples (n = 8), and background samples (n = 2) were collected in both TRS during 3-5 consecutive days, following US National Institute for Occupational Safety and Health (US NIOSH) methods 7400 and 7402. Asbestos samples were analyzed by an American Industrial Hygiene Association accredited laboratory. On at least one of the days sampled, all riveters were exposed to asbestos concentrations that exceeded the US OSHA permissible exposure limit or the Colombian permissible limit value. Additionally, from the forty-seven 30-min short-term personal samples collected, two (4.3%) exceeded the US OSHA excursion limit of 1 f cm(-3). In this study, we identified that the working conditions and use of asbestos containing transmission products expose transmission mechanics to asbestos concentrations that exceed both the Colombian and OSHA standards. The potential consequences for the health of these workers are of great concern.

Electricians’ chrysotile asbestos exposure from electrical products and risks of mesothelioma and lung cancer

Both mechanistic and epidemiology studies indicate chrysotile asbestos has a threshold below which it does not cause mesothelioma or lung cancer. We conducted a critical review to determine whether electricians are at increased risk for these cancers and, if so, whether their exposure to chrysotile in electrical products could be responsible. We found that most, but not all, epidemiology studies indicate electricians are at increased risk for both cancers. Studies that evaluated electricians’ exposure to asbestos during normal work tasks have generally reported low concentrations in air; an experimental study showed that grinding or drilling products containing encapsulated chrysotile resulted in exposures to chrysotile fibers far below the OSHA permissible exposure limit and the cancer no observed adverse effect level. Studies of other craftsmen who often work in the vicinity of electricians, such as insulators, reported asbestos (including amphibole) exposures that were relatively high. Overall, the evidence does not indicate that exposure to chrysotile in electrical products causes mesothelioma or lung cancer in electricians. Rather, the most likely cause of lung cancer in electricians is smoking, and the most likely cause of mesothelioma is exposure to amphibole asbestos as a result of renovation/demolition work or working in the proximity of other skilled craftsmen.

Room temperature gas sensor based on tin dioxide-carbon nanotubes composite films

Chemical sensors based on tin dioxide-carbon nanotubes (SnO2-CNT) composite films were fabricated by hot filament chemical vapor deposition (HF-CVD) technique. The composite films consist of SnO2 nanoparticles highly dispersed on the CNTs surface. Their resistivity is highly sensitive to the presence of adsorbates, which become easily attached or detached at room temperature and ambient pressure depending on their gas phase concentration. We systematically studied the sensitivity of the SnO2-CNT composite films for ethanol, methanol and H2S. The results were also compared to those for SnO2 and CNTs separately. It is shown that the SnO2-CNT composite films can detect ethanol, methanol and H2S down to ppm levels below OSHA's permissible exposure limits at room temperature and ambient pressure. Moreover, they self-recover within 1min without requiring any heating or energy source.

A Comparison of Two Sampling Methods for the Detection of Airborne Methylene Bisphenyl Diisocyanate

The purpose of this study was to determine if there was a significant difference between two readily available sampling methodologies for airborne methylene bisphenyl diisocyanate (MDI), which is an essential precursor in the spray-on truck bed lining industry. Seventy-two personal airborne samples of MDI were collected and analyzed from nine spray-on truck bed liner businesses in northern Colorado. Wide ranges of exposure concentrations were encountered during the spray-on application, including concentrations that exceeded the OSHA permissible exposure limit. The highest airborne MDI concentration measured was 690 ppb. A statistically significant difference between field-desorbed and laboratory-desorbed methods was determined. The field-desorbed sampling methodology yielded consistently higher MDI concentrations than the laboratory-desorbed sampling methodology, which suggests that immediate desorption minimizes isocyanate loss and potential underestimations. Results from the analysis of variance also indicated that different facility factors and environmental conditions within each company, such as the use of ventilation or humidity level, affected the MDI concentrations, indicating the potential for better mitigation of exposures using the hierarchy of controls.

Airborne benzene exposures from cleaning metal surfaces with small volumes of petroleum solvents

Airborne benzene concentrations were measured in a room with controlled air exchange during surface cleaning with two petroleum-based solvents (a paint thinner and an engine degreaser). The solvents were spiked with benzene to obtain target concentrations of 0.001, 0.01, and 0.1% by volume in the liquid. Personal samples on the worker and area samples up to 1.8m away were collected over 12 events (n=84 samples) designed to examine variation in exposure with solvent type, cleaning method (rag wipe or spatula scrape), surface area cleaned, air exchange rate, solvent volume applied, and distance from the cleaned surface. Average task breathing zone concentrations of benzene represented by 18-32 min time-weighted averages were 0.01 ppm, 0.05 ppm, and 0.27 ppm, when the solvents contained approximately 0.003, 0.008, and 0.07% benzene. Solvent benzene concentration, volume applied, and distance from the handling activities had the greatest effect on airborne concentrations. The studied solvent products containing 0.07% benzene (spiked) did not exceed the current OSHA permissible exposure limit of 1 ppm (averaged over 8h) or the ACGIH Threshold Limit Value of 0.5 ppm, in any of the tested short-term exposure scenarios. These data suggest that, under these solvent use scenarios, petroleum-based solvent products produced in the United States after 1978 likely did not produce airborne benzene concentrations above those measured if the concentration was less than 0.1% benzene.

Safe Use of Chemicals for Sterilization in Healthcare

Chemical sterilization is necessary for temperature sensitive items that cannot be sterilized with steam. These chemical sterilants are by their nature hazardous; otherwise, they would not function well. Modern sterilizers and associated equipment are designed so that these chemicals can be used safely. Whether through mechanical failure, wear and tear, or user error, leaks do sometimes occur. The maximum chemical exposure is determined by OSHA permissible exposure limits, if available, and if not available, employers should use recognized standards. Employers have a duty to ensure safe work environment and take appropriate action to mitigate potential risks. Employers should therefore assess the hazards of the chemicals used, the potential modes for leakage, means for identifying leaks and the risk of exposure of employees. Ideally, work practices should be developed by healthcare facilities so that sterile processing employees know what to do in case of a chemical leak or spill, and how to safely use these chemicals to ensure their own, and patient safety.

Comparison of modeled and measured concentrations of airborne benzene from the use of petroleum-based solvents spiked with low levels of benzene

Airborne benzene concentrations were measured in a room with controlled air exchange during surface cleaning with two petroleum-based solvents (a paint thinner and an engine degreaser). The solvents were spiked with benzene to obtain target concentrations of 0.001, 0.01, and 0.1% by volume in the liquid. Personal samples on the worker and area samples up to 1.8 m away were collected over 12 events (n = 84 samples) designed to examine variation in exposure with solvent type, cleaning method (rag wipe or spatula scrape), surface area cleaned, air exchange rate, solvent volume applied, and distance from the cleaned surface. Average task breathing zone concentrations of benzene represented by 18–32 min time-weighted averages were 0.01 ppm, 0.05 ppm, and 0.27 ppm, when the solvents contained approximately 0.003, 0.008, and 0.07% benzene. Solvent benzene concentration, volume applied, and distance from the handling activities had the greatest effect on airborne concentrations. The studied solvent products containing 0.07% benzene (spiked) did not exceed the current OSHA permissible exposure limit of 1 ppm (averaged over 8 h) or the ACGIH Threshold Limit Value of 0.5 ppm, in any of the tested short-term exposure scenarios. These data suggest that, under these solvent use scenarios, petroleum-based solvent products produced in the United States after 1978 likely did not produce airborne benzene concentrations above those measured if the concentration was less than 0.1% benzene.

A state of the science review of the potential health hazards associated with asbestos in shielded metal arc welding rods in the United States

Due to its unique chemical properties, chrysotile asbestos was historically incorporated into a wide variety of products, including the outer covering, or “flux” of certain classifications of general arc mild steel welding electrodes. The purpose of this analysis is to review the historical engineering, toxicology, regulatory, and epidemiology information relevant to asbestos in mild steel welding rods in order to assess whether mild steel welders are at increased risk of developing asbestos-related diseases as a result of welding rod use. We divided our analysis into four distinct time periods, based on what we perceived to be seminal events in welding technology or in the evolution of knowledge regarding asbestos and asbestos-related diseases. These time periods are as follows: late 1800s to 1929, 1930–1955, 1956–1970, and 1971–2006. We found that studies that attempted to measure airborne asbestos directly in welding rod fumes found no measurable fibers; this is likely due to the fact that the fibers degrade at high temperatures present in the welding arc. In addition, “worst-case” use simulation studies, specifically intended to generate airborne flux particles, reported that airborne asbestos concentrations were either undetectable or very low. The airborne concentrations generated were always below the current OSHA permissible exposure limit (0.1 f/cc TWA), and the lifetime doses associated with “worst-case” use were found to be far below the plausible thresholds for mesothelioma and lung cancer. The epidemiology of mild steel welders is difficult to interpret due to confounding exposures such as (1) possible exposure to nickel and hexavalent chromium in stainless steel welding fumes (lung cancer), (2) smoking (lung cancer), and (3) bystander exposure to amphibole asbestos (lung cancer and mesothelioma). None of the published welder studies controlled for all three factors, yet when any single source of bias was controlled for, the majority of the studies reported no significant risk in either asbestos-related disease. Furthermore, none of the investigators in any of the welder studies suggested that asbestos in welding rods might be a risk factor for lung cancer or mesothelioma, and there is not a single case report in the medical literature that attempts to link welding rod use to an asbestos-related disease. We conclude that the weight of evidence indicates that welders were not historically at risk of developing asbestos-related diseases as a result of welding rod use.

Asbestos Exposures of Mechanics Performing Clutch Service on Motor Vehicles

A study was conducted to assess historical asbestos exposures of mechanics performing clutch service on motor vehicles. For most of the 20th century, friction components used in brakes and manual transmission clutches contained approximately 25–60% chrysotile asbestos. Since the late 1960s, asbestos exposure assessment studies conducted on mechanics performing brake service have frequently reported levels below the current OSHA permissible exposure limit (PEL) of 0.1 fiber/cc (flcc). Although there is a robust asbestos exposure data set for mechanics performing brake service, there are almost no data for mechanics removing and replacing clutches in manual transmission vehicles. Personal and area airborne asbestos samples were collected during the removal of asbestos-containing clutches from 15 manual transmissions obtained from salvage facilities by an experienced mechanic. Clutch plates and debris were analyzed for asbestos using EPA and ISO published analytical methods. More than 100 personal and area air samples were collected and analyzed for asbestos fibers using NIOSH methods 7400 and 7402. A separate study involved a telephone survey of 16 automotive mechanics who began work prior to 1975. The mechanics were asked about the duration, frequency, and methods used to perform clutch service. Wear debris in the bell housing surrounding clutches had an average of 0.1% chrysotile asbestos by weight, a value consistent with similar reports of brake debris. Asbestos air sampling data collected averaged 0.047 flcc. Mechanics participating in the telephone survey indicated that clutch service was performed infrequently, the entire clutch assembly was normally replaced, and there was no need to otherwise handle the asbestos-containing clutch plates. These mechanics also confirmed that wet methods were most frequently used to clean debris from the bell housing. Combining the asbestos exposure that occurred when mechanics performed clutch service, along with the duration and frequency of this task, the incremental contribution of this task to mechanics' 8-hr time-weighted average (TWA) asbestos exposures was 0.0016 flcc. Using the range of data inputs that were obtained, the authors calculated a range of TWA exposures of 3.75 × 10−5 flcc to 0.03 flcc. The mean value of 0.0016 flcc is below background levels of asbestos that have been reported in garages during this time and below the current OSHA PEL of 0.1 flcc.

Screening Ventilation Strategies for Confined-Space Manure Storage Facilities

Fatalities associated with entry into on-farm confined-space manure storage facilities occur each year. The fatalities are due to asphyxiation or poisoning by exposure to high concentrations of hydrogen sulfide, methane, and carbon dioxide. Forced ventilation has been shown to be an effective way to reduce concentrations of noxious gases to levels that are safe for human entry into these storage facilities. Hydrogen sulfide (H2S) was used as an indicator gas to investigate the effectiveness of forced-air ventilation strategies for eliminating the toxic and oxygen-deficient atmosphere in confined-space manure storage facilities. This article focuses on experimental methods for identifying ventilation strategies that effectively reduce toxic gas (i.e., H2S) concentrations in a fan-ventilated confined-space manure tank to the OSHA permissible exposure limit (PEL) (H2S PEL = 10 ppm) and to 25% of the initial gas concentration. Typical H2S concentration reduction curves during forced-air ventilation were identified in the tank as well. Based on the experimental tests conducted in this research, the most promising candidate ventilation strategies were identified for this rectangular confined-space manure tank with solid, fully slotted, and partially slotted covers. In addition, based on the results of experimental tests, a field-based database was developed for future validation of computational fluid dynamics modeling protocols.

A pilot study to determine mercury exposure through vapor and bound to PM10 in a dental school environment

Mercury (Hg) is widely used in the dental working environment, exposing dental practitioners and assistants to potentially toxic Hg vapors. Concentrations of Hg in vapor and in particulate matter (PM10) were measured in the Dental Simulation Laboratory (DSL) and in the Dental Clinic (DC) at the School of Dentistry, University of Puerto Rico. PM10 samples were collected over a 36-h period and Hg vapor was collected for eight-hour periods. PM10 mass was determined gravimetically and Hg (bound to PM10 and vapor) was extracted and analyzed by atomic absorption. Indoor levels of PM10 in the DSL ranged from 9.2 to 41.6 microg/m3 and 35.0 to 68.2 microg/m3 in the DC. Levels of particle-bound Hg ranged from 0.1 to 1.2 microg/m3 and in vapor 1.1 to 3.3mg/m3 at the DSL; the DC levels ranged from <0.01 to 0.2 microg/m3 for particle bound Hg and 13.6 to 102.7 microg/m3 in vapor. PM10 concentrations were below Indoor Air Quality suggested limits for total dust (100 microg/m3). Levels of mercury bound to PM10 were low; however, mercury vapor was several times higher than the suggested OSHA (permissible exposure limit--100 microg/m3) in the DSL.