Occupational Safety And Health Administration Permissible Exposure Limit Research Articles

Analysis of biomonitoring data to assess employer compliance with OSHA's permissible exposure limits for air contaminants.

The Occupational Safety and Health Administration (OSHA) regulates exposures to hazardous chemicals in workplace air. When contemporaneous exposure measurements are unavailable, retrospective analysis of biomarkers could provide valuable information about workers' exposures. Single-compartment pharmacokinetic (PK) models were created to relate the concentration of a chemical in the air to the concentration of the chemical or its metabolite in workers' blood or urine. OSHA utilized the PK models in investigations of three fatal incidents in which workers were exposed to nickel carbonyl, methyl bromide, or styrene. To obtain the minimum plausible estimate of each exposure, OSHA used conservative assumptions about parameters such as workers' inhalation rates, baseline levels of biomarker, and chemicals' volumes of distribution. OSHA analyzed a worker's urinary nickel concentration and concluded that his 8-htime-weighted average exposure to nickel carbonyl was at least 0.06 mg/m3 . Analysis of a worker's postexposure, premortem blood bromide level revealed that his exposure to methyl bromide was at least 181 mg/m3 . Post-mortem blood styrene measurements suggested that a third worker's exposure to styrene was at least 625 mg/m3 . These exposures exceeded OSHA's permissible exposure limits of 0.007 mg/m3 for nickel carbonyl, 80 mg/m3 for methyl bromide, and 426 mg/m3 for styrene. OSHA successfully cited the three employers for violations of chemical exposure limits. Analysis of biomarkers via PK modeling enables retrospective evaluations of workers' acute exposures to hazardous chemicals. These techniques are useful to occupational regulators who assess employer compliance with mandatory exposure limits.

Safety of Drilling 3-Dimensional–Printed Temporal Bones

Three-dimensional (3-D) printing of temporal bones is becoming more prevalent. However, there has been no measure of the safety of drilling these models to date. It is unknown whether the heat and sheer from the drill may create harmful volatile organic compounds (VOCs). To determine the level of exposure to airborne contaminants when conducting high-speed drilling on 3-D-printed models and to explore whether there is a need for exposure control measures. In this occupational safety assessment carried out in a temporal bone laboratory, 3 individual 3-D-printed temporal bones were made using 3 different materials commonly cited in the literature: polylactic acid (PLA), photoreactive acrylic resin (PAR), and acrylonitrile butadiene styrene (ABS). Each model was drilled for 40 minutes while the surgeon wore a sampling badge. Sampling was conducted for airborne concentrations of VOCs and total particulate (TP). Monitoring for VOCs was conducted using Assay Technology 521-25 organic vapor badge worn at the surgeon's neckline. Monitoring for TP was conducted using a polyvinyl chloride filter housed inside a cassette and coupled with an SKC AirChek 52 personal air-sampling pump. Samples were collected and analyzed in accordance with NIOSH Method 500. Presence of VOCs and TP count exposures at Occupational Safety and Health Administration (OSHA) actionable levels. Results of the VOC sample were less than detection limits except for isopropyl alcohol at 0.24 ppm for PAR. The TP samples were less than the detection limit of 1.4 mg/m3. The results are below all applicable OSHA Action Levels and Permissible Exposure Limits for all contaminants sampled for. Drilling 3-D-printed models made from PLA, ABS, and PAR was safe by OSHA standards. Continued monitoring and safety testing are needed as 3-D-printed technologies are introduced to our specialty.

Comparative health risk of inhaled exposure to organic solvents, toxic metals, and hexavalent chromium from the use of spray paints in Taiwan.

The study investigated the exposure of spray painters to organic solvents, toxic metals, and hexavalent chromium over 21 working days in 2017. The results found these concentrations of 12 VOCs to be below the short-term exposure limit (STEL) established by the US Occupational Safety and Health Administration (OSHA). The mass concentration of total particulate matter (PM) exposure to workers was 20.01±10.78mg/m3, which exceeds OSHA's permissible exposure level of 15mg/m3. The mean concentration of the total metals for all particle sizes was 109.1±12.0μg/m3, and those for lead (496,017.0ng/m3) and iron (252,123.8ng/m3) were the highest of metal elements. Significantly, the mean concentrations of Pb and As exceeded OSHA's permissible exposure limits (PELs) of 0.05 and 0.01mg/m3, respectively. The total hexavalent chromium concentration was 1163.01ng/m3, and the individual particle sizes (PM1-2.5, PM1, and PM0.25) were strongly and positively correlated with the Cr(VI) concentrations for PM2.5. The study determined that approximately 56.14% of the hexavalent chromium inhaled during the spray-painting process was deposited in the upper respiratory system of the head airway region, followed by the alveolar and tracheobronchial regions, with fractions of 11.93 and 0.05%, respectively. Although the mean ratio of hexavalent chromium to total chromium was only 3.6% for all particle sizes, the cancer risk of the total particles in Cr(VI) (1.6×10-3) exceeded the acceptable risk value (10-6). The cancer risks of As and Cr(VI) associated with quasi-ultrafine particles, PM0.5-1, PM1-2.5, and PM> 2.5, also exceeded 10-6. Comparison of the carcinogenicity risk of VOCs and metals suggests that the adverse health effect of inhaled particles on spray-painting workers is more serious than that from VOC exposure.

Improving the ACGIH threshold limit value (TLV) process

The intent of this manuscript is to elucidate needed improvements in American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit value (TLV) deliberations. More broadly, irreproducibility and bias adversely impact the collection, interpretation, statistical analysis, presentation, and reporting of results in many fields. In 2012, Begley and Ellis reported that scientists at Amgen had attempted to confirm published findings related to research topics of possible interest to Amgen. Fifty-three papers were deemed “landmark” studies. The authors were “shocked” when scientific findings were confirmed in only 6 (11%) cases. Many studies have confirmed that the peer-reviewed literature in biomedicine is in the midst of an irreproducibility crisis. Compounding the irreproducibility crisis is the existence of a significant bias against the publication of negative results. In the toxicology setting, negative toxicity test results are infrequently published as compared with reports that a chemical possesses a particular toxicity in a given test. Despite these deficiencies, the ACGIH states that “…the TLV®-CS Committee preferably relies on published, peer reviewed literature available in the public domain.” The primarily academic studies published in the peer-reviewed literature upon which ACGIH relies to determine TLVs rarely report raw data not already statistically transformed that are thus incalculable. In contrast, consideration of unpublished studies funded by industry, the vast majority of which are good laboratory practice-conducted contract lab studies, is only acceptable to ACGIH if the data owner provides the raw data to third parties upon request. This asymmetry in both the source of data emphasized, and inability to independently statistically analyze findings reported in the published academic literature, introduces a strong skew toward reliance on unverifiable although published measurements in the TLV process. Since Occupational Safety and Health Administration (OSHA) recommends that workplaces rely on ACGIH TLVs and National Institute for Occupational Safety and Health recommended exposure limits rather than older OSHA permissible exposure limit values to optimize worker safety, ACGIH should adopt a more transparent and science-based process.

Statistical Modeling of Occupational Exposure to Polycyclic Aromatic Hydrocarbons Using OSHA Data

Polycyclic aromatic hydrocarbons (PAHs) are a group of pollutants with multiple variants classified as carcinogenic. The Occupational Safety and Health Administration (OSHA) provided access to two PAH exposure databanks of United States workplace compliance testing data collected between 1979 and 2010. Mixed-effects logistic models were used to predict the exceedance fraction (EF), i.e., the probability of exceeding OSHA's Permissible Exposure Limit (PEL = 0.2 mg/m3) for PAHs based on industry and occupation. Measurements of coal tar pitch volatiles were used as a surrogate for PAHs. Time, databank, occupation, and industry were included as fixed-effects while an identifier for the compliance inspection number was included as a random effect. Analyses involved 2,509 full-shift personal measurements. Results showed that the majority of industries had an estimated EF < 0.5, although several industries, including Standardized Industry Classification codes 1623 (Water, Sewer, Pipeline, and Communication and Powerline Construction), 1711 (Plumbing, Heating, and Air-Conditioning), 2824 (Manmade Organic Fibres), 3496 (Misc. Fabricated Wire products), and 5812 (Eating Places), and Major group's 13 (Oil and Gas Extraction) and 30 (Rubber and Miscellaneous Plastic Products), were estimated to have more than an 80% likelihood of exceeding the PEL. There was an inverse temporal trend of exceeding the PEL, with lower risk in most recent years, albeit not statistically significant. Similar results were shown when incorporating occupation, but varied depending on the occupation as the majority of industries predicted at the administrative level, e.g., managers, had an estimated EF < 0.5 while at the minimally skilled/laborer level there was a substantial increase in the estimated EF. These statistical models allow the prediction of PAH exposure risk through individual occupational histories and will be used to create a job-exposure matrix for use in a population-based case-control study exploring PAH exposure and breast cancer risk.

Occupational Exposures to Styrene Vapor in a Manufacturing Plant for Fiber-Reinforced Composite Wind Turbine Blades

A utility-scale wind turbine blade manufacturing plant requested assistance from the National Institute for Occupational Safety and Health (NIOSH) in controlling worker exposures to styrene at a plant that produced 37 and 42 m long fiber-reinforced wind turbine blades. The plant requested NIOSH assistance because previous air sampling conducted by the company indicated concerns about peak styrene concentrations when workers entered the confined space inside of the wind turbine blade. NIOSH researchers conducted two site visits and collected personal breathing zone and area air samples while workers performed the wind turbine blade manufacturing tasks of vacuum-assisted resin transfer molding (VARTM), gelcoating, glue wiping, and installing the safety platform. All samples were collected during the course of normal employee work activities and analyzed for styrene using NIOSH Method 1501. All sampling was task based since full-shift sampling from a prior Occupational Safety and Health Administration (OSHA) compliance inspection did not show any exposures to styrene above the OSHA permissible exposure limit. During the initial NIOSH site visit, 67 personal breathing zone and 18 area air samples were collected while workers performed tasks of VARTM, gelcoating, glue wipe, and installation of a safety platform. After the initial site visit, the company made changes to the glue wipe task that eliminated the need for workers to enter the confined space inside of the wind turbine blade. During the follow-up site visit, 12 personal breathing zone and 8 area air samples were collected from workers performing the modified glue wipe task. During the initial site visit, the geometric means of the personal breathing zone styrene air samples were 1.8 p.p.m. (n = 21) for workers performing the VARTM task, 68 p.p.m. (n = 5) for workers installing a safety platform, and 340 p.p.m. (n = 14) for workers performing the glue wipe task, where n is the number of workers sampled for a given mean result. Gelcoating workers included job categories of millers, gelcoat machine operators, and gelcoaters. Geometric mean personal breathing zone styrene air samples were 150 p.p.m. (n = 6) for millers, 87 p.p.m. (n = 2) for the gelcoat machine operators, and 66 p.p.m. (n = 19) for gelcoaters. The geometric mean of the personal breathing zone styrene air samples from the glue wipe task measured during the follow-up site visit was 31 p.p.m. (n = 12). The closed molding VARTM process was very effective at controlling worker exposures to styrene. Personal breathing zone styrene air samples were reduced by an order of magnitude after changes were made to the glue wipe task. The company used chemical substitution to eliminate styrene exposure during the installation of the safety platform. Recommendations were provided to reduce styrene concentrations during gelcoating.

A study of significant variables and their effects on the analysis of hexavalent chromium

The recent reduction in the Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) for hexavalent chromium Cr(VI) will most certainly cause employers to perform more exposure determinations. The standard applies to Cr(VI) in both the soluble and insoluble form. The National Institute for Occupational Safety and Health (NIOSH) Method 7600, an analytical technique utilizing visible spectrophotometry, was examined. The new OSHA PEL of 5 micrograms per cubic meter (μg/m 3 ) mandated that the lowest possible method detection limit (MDL) be obtained. Also, the solubilities of the test samples were in most cases unknown. Accordingly, this study focused on the following: (1) removal of filter debris or other turbidity, (2) filter type, storage stability and (3) the alkaline extraction of the samples. Preliminary analysis of blank polyvinyl chloride (PVC) filters resulted in noticeable debris and turbidity. To test turbidity a blank PVC filter was placed in a centrifuge tube and extracted with sulfuric acid. Eight replicates yielded a MDL of 4 micrograms per liter (μg/L). The aliquots were then filtered using a Buchner funnel and yielded 2 μg/L MDL. Finally, the filtrates were centrifuged for 2 minutes further reducing the MDL to 0.7 μg/L. The use of the centrifuge to eliminate turbidity was significant enough to necessitate further investigation. To determine the effect of an alkaline extraction on soluble Cr(VI), a standard addition of 0.5 μg of potassium chromate was performed on a filter, allowed to dry and then extracted with the alkaline solution. Three replicates had a 109.4% recovery. Centrifuging the filters was useful in eliminating the CO 2 interference for the alkaline extraction. Also, the use of an alkaline extraction did not negatively impact the soluble Cr(VI). The positive result of the preliminary extractions resulted in further investigation of an alkaline extraction to incorporate the inclusion of both soluble and insoluble Cr(VI).

Asbestos Exposure during Routine Brake Lining Manufacture

Occupational exposure to asbestos fiber and total dust of workers of a major brake lining manufacture plant in a developing country were examined and compared with those in developed countries. Time weighted average of total dust and asbestos fiber concentration in the potential sources of exposure were monitored. All personal air sampling were collected on membrane filters and analyzed by phase contrast optical microscopy (PCM) for comparison with the occupational safety and health administration (OSHA) permissible exposure limit (PEL) of 0.1 f/cc, 8-h time--weighted average. This study demonstrates that routine mixing, polishing and beveling process in the brake lining production can result in elevated levels of airborne asbestos. Greater releases of airborne asbestos were observed during mixing process and mixer machine. The results also showed that the employees working in the process had the exposure to total dust concentrations ranging from 2.08 to 16.32 mg/m(3) that is higher than OSHA, recommendation. According to OSHA definition of fibers, it has been indicated that from 3,000 counted particles, 90% of particles are in the form of non-fiber and reaming have fiber-shaped. The particle analyze gives the geometric mean diameter as 6.02 mum, and also indicated that the arithmetic mean of the number distribution for the particle population was 8.4 mum. Approximately 60.4% of the counted fibers were lower than 10 mum in length, from which only 8% consists of fibers (>5 mum in length). In conclusion, the analysis showed a presence in the air of only chrysotile asbestos and an absence of other types of asbestos. During an 8-h shift, the average asbestos fiber exposure (0.78 f/cc) were 7.8 time in excess of OSHA PEL. Additional studies in occupational exposure to asbestos are needed.

Beryllium Exposure Data: Rosenman et al. Respond

We thank Kolanz for his careful reading of our article (Rosenman et al. 2005). An erratum correcting the problem he noted appears on page A214. How do these corrected numbers change our results? More chronic beryllium disease (CBD) and sensitization occurred with exposure below the Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) of 2 μg/m3 (OSHA 2005) than we previously reported, but no CBD or sensitization was found below the Department of Energy (DOE) guidelines of 0.2 μg/m3 (DOE 1999) or the even more protective level proposed by the American Conference of Governmental Industrial Hygienists (ACGIH 2005) of 0.02 μg/m3. There was an insufficient number of individuals—only three, and they were all normal—to assess the safety of the DOE guidelines or proposed ACGIH level. Our previously reported findings regarding chemical and physical form—that sensitized individuals compared with individuals with CBD had higher exposure to beryllium in a soluble form and to fumes of beryllium (Rosenman et al. 2005)—remain unchanged. However, the mean peak exposure for the sensitized group in our Table 8, the mean nonsoluble exposure for the sensitized group in Table 9, and the mean dust exposure for the sensitized group and mean fume exposure for the CBD group in Table 10 were no longer significantly different, whereas the peak fume exposure for the CBD group was now significantly different in Table 10. Having acknowledged and corrected the error pointed out by Kolanz, we take strong exception to his statement that “the study cannot sustain conclusions about the degree of risk associated with lower levels of exposure,” by which he means less than the OSHA PEL of 2 μg/m3 (OSHA 2005). One of Kolanz’s criticisms of our article (Rosenman et al. 2005) is that the daily weighted average (DWA) represented the daily exposure based on data averaged over 3 months. Breslin and Harris (1958) conducted a time study, which was updated as activities and location changed for each job title. During a 3-month period, three or more samples were collected and standardized to represent the general area where each person worked, and in some cases the breathing zone during work activities. The arithmetic average of the samples for each location/type was then calculated and weighted by time (Breslin and Harris 1958). Use of these summed weighted values, divided by the shift duration, is consistent with the American Industrial Hygiene Association (AIHA) exposure assessment guidance (Mulhausen and Damiano 1998) cited by Kolanz. We agree with Kolanz’s comment about the use of the flame spectroscopy method of chemical analysis and its general limit of detection of 0.1 μg/m3. In the job exposure matrix and task exposure matrix developed to support this project (Chen 2001), no exposure estimate was < 0.1 μg/m3, so this issue would have no effect on our results. Kolanz also takes exception with our estimates of mean exposures, stating that these values were derived by triple averaging. We derived the mean exposures as follows: for a given worker in a given job in a given year, we multiplied the number of days worked in that year for that worker by our best estimated DWA for that job in that year. We then summed those values over all jobs for that worker to derive that worker’s cumulative exposure. Next we divided that worker’s cumulative exposure by the total number of days worked in his/her job history to derive that worker’s mean exposure. Thus, there is only one averaging on each worker and a subsequent averaging for the population. We used multiple metrics (cumulative, average, peak job, and peak task for total exposure; exposure by chemical form; and exposure by physical form) to characterize not only the central tendencies of the exposures but also their extreme excursions. We stand by our statement that The inclusion of genetic data combined with exposure data may better define which individuals in this cohort are at a particularly high risk of development of CBD and/or sensitization and may account for the absence of typical exposure–response seen with other environmental or occupational toxins. It is also important to note that both peak exposure and the different chemical and physical forms may be important factors in the risk of development of CBD but are not part of the current OSHA standard (OSHA 2005). Finally, Kolanz states that “Rosenman et al. (2005) made no recommendations regarding how to protect beryllium workers.” Clearly, however, our call to lower the allowable standard is a recommendation we put forth to protect beryllium workers. Despite the limitations of deriving historical exposure estimates, our corrected data continue to point to the inadequacy of the current OSHA standard to protect workers from developing chronic beryllium disease.

Analytical Performance Criteria

Column Editor Kevin Ashley

Ototoxic Occupational Exposures for a Stock Car Racing Team: II. Chemical Surveys

The National Institute for Occupational Safety and Health (NIOSH) conducted a series of surveys to evaluate occupational exposure to noise and potentially ototoxic chemical agents among members of a professional stock car racing team. Exposure assessments included site visits to the team's race shop and a worst-case scenario racetrack. During site visits to the race team's shop, area samples were collected to measure exposures to potentially ototoxic chemicals, including, organic compounds (typical of solvents), metals, and carbon monoxide (CO). Exposures to these chemicals were all below their corresponding Occupational Safety and Health Administration (OSHA) permissible exposure limits (PELs), NIOSH recommended exposure limits (RELs), and American Conference of Governmental Industrial Hygienists (ACGIH®) threshold limit values (TLVs®). During site visits to the racetrack, area and personal samples were collected for organic compounds, lead, and CO in and around the “pit” area where the cars undergo race preparation and service during the race. Exposures to organic compounds and lead were either nondetectable or too low to quantify. Twenty-five percent of the CO time-weighted average concentrations exceeded the OSHA PEL, NIOSH REL, and ACGIH TLV after being adjusted for a 10-hour workday. Peak CO measurements exceeded the NIOSH recommended ceiling limit of 200 ppm. Based on these data, exposures to potentially ototoxic chemicals are probably not high enough to produce an adverse effect greater than that produced by the high sound pressure levels alone. However, carbon monoxide levels occasionally exceeded all evaluation criteria at the racetrack.

Trends in occupational lead exposure since the 1978 OSHA lead standard.

The purpose of the study was to evaluate trends in occupational lead exposures throughout U.S. industry after the establishment of the general industry lead standard in 1978 and the construction industry standard in 1993. Lead exposure measurements collected by the Occupational Safety and Health Administration (OSHA) under their compliance and consultation programs were analyzed. Time trends in the distributions of exposure levels were evaluated graphically. Trends in the proportion of exposures above the OSHA permissible exposure limit (PEL) were analyzed using logistic regression models. The distribution of lead exposure levels declined over the study time period for general industry, but not for construction. The median exposure levels for general industry facilities decreased five- to tenfold. Logistic regression models reveal statistically significant declines in the odds of a lead exposure exceeding the PEL. This study provides evidence for relatively large decreases in lead exposure levels in general industry facilities over time. The study does not provide similar evidence for the construction industry. Given the limited number of years of data available since the implementation of the revised construction standard for lead, re-analysis of lead exposure levels within this industry would be worthwhile when more data become available.

Assessment of silica exposure and engineering controls during tuckpointing.

Exposures to crystalline silica in the construction industry are widespread. This report documents exposures to crystalline silica and describes the effectiveness of a commercially available dust collection system designed for tuckpointing tools. Exposure to respirable crystalline silica (quartz) can result in silicosis, a serious and often fatal disease with symptoms including shortness of breath, weight loss, weakness, and the onset of autoimmune diseases. The American Conference of Governmental Industrial Hygienists (ACGIH©R ) regards silica as a suspected human carcinogen, and the National Toxicology Program (NTP) and the National Institute for Occupational Safety and Health (NIOSH) have designated crystalline silica as a potential occupational carcinogen. NIOSH estimates that more than one million workers are at risk for silicosis, with the majority of them in construction trades.(1) The NIOSH Recommended Exposure Limit (REL) and ACGIH©R Threshold Limit Value (TLV©R ) for respirable quartz are 0.05 mg/m3. The Occupational Safety and Health Administration (OSHA) Permissible Exposure Limit (PEL) for respirable dust containing crystalline silica for the construction industry is measured in millions of particles per cubic foot (mppcf) and is calculated using the following formula: PEL = 250 mppcf/% silica + 5.(2) However, OSHA compliance officers use the general industry PEL for respirable silica to test for compliance on construction sites, calculating the allowable exposure based on the measured quartz percentage for each sample in accordance with the following equation: 10 mg/m3/(% quartz + 2).(1) In this article, we used the NIOSH REL and the ACGIH TLV as the evaluation criteria, as these values reflect more current research on the health effects of silica exposure. Construction workers are routinely exposed to silica-containing dust without any engineering controls. One study showed that tuckpointing workers were exposed to silica-containing dust at levels 17 to 116 times higher than the OSHA PEL and 212 to 4300 times higher than the NIOSH REL.(3) According to NIOSH, non-powered air purifying respirators are not recommended for workers who are exposed to greater than 10 times the NIOSH REL.(4) In cases such as this, engineering controls, not only respirators, are required to reduce the exposure to the workers. OSHA also requires that engineering controls be used to the extent feasible for reducing exposures to regulated agents.(5) Exposures in construction are closely related to task.(6) For the grinding process during tuckpointing, personal silica exposures can vary substantially between the component tasks a worker conducts. Exposure assessment and the design of effective control technology require knowledge of each task component’s relative contribution to the total exposure. Detailed work task–exposure analysis using a combination of direct reading monitor and videotaping is well suited to assess the exposure associated with each task component in the mortar grinding process.(7) The goals of this study were as follows: 1) to evaluate the efficiency of engineering controls by calculating the respirable dust reduction as the ratio of exposure, both with and without the engineering control; 2) to determine the contribution of each component task to the total exposure in the grinding process based on the detailed task-exposure analysis; 3) to suggest improvements to the engineering control based on the data analysis and the comments of the journeyman bricklayers participating in the evaluation; and, 4) to evaluate the suitability of the disposable half-mask respirators typically used in this process.

Continuing exposure to hexavalent chromium, a known lung carcinogen: an analysis of OSHA compliance inspections, 1990-2000.

Hexavalent chromium is widely recognized to be a lung carcinogen. However, the U.S. Occupational Safety and Health Administration (OSHA) has failed to reduce the permissible exposure limit (PEL), despite having acknowledged in 1994 that the current limit is too high. In 1993, Public Citizen and the Paper, Allied-Industrial, Chemical and Energy Workers International Union (PACE) petitioned to lower the PEL from the current 100 microg/m(3) to 0.5 microg/m(3) as an 8-hr time-weighted average (TWA). To assess industry compliance with the current PEL, and to determine the feasibility of achieving the proposed lower limit of 0.5 microg/m(3), we conducted a secondary data analysis of OSHA's Integrated Management Information System (IMIS) database. This database contains 813 measurements of hexavalent chromium exposure from inspections performed during the years 1990-2000. There was a statistically significant decline in the annual number of measurements over the study period from 127 in 1990 to 67 in 2000 (F = 0.0009; linear regression). The median TWA measurement was 10 microg/m(3) (range: 0.01-13,960 microg/m(3)) and the median ceiling measurement was 40.5 microg/m(3) (range: 0.25-25,000 microg/m(3)). Neither median TWA nor median ceiling exposures (if hexavalent chromium was detected) declined significantly during the study period (F = 0.065 and 0.57, respectively). Overall, 13.7% of TWA measurements were at or below the Public Citizen/PACE proposed standard; 65.0% were between the Public Citizen/PACE proposal and the current OSHA PEL; and 21.3% exceeded the OSHA PEL. Compared to OSHA measurements, state measurements were less likely to detect hexavalent chromium (40.2% vs. 52.1%; P = 0.0007; chi-square) and less likely to issue any citation (9.3% vs. 19.1%; P = 0.0003), including citations for overexposure if the exposure exceeded the PEL (54.8% vs. 78.8%; P = 0.012). U.S. workers continue to be exposed to dangerously high hexavalent chromium levels, but low exposure levels were found in some industries. Further investigations should examine whether state plans provide weaker enforcement than federal OSHA.

Engineering controls for furniture strippers to meet the OSHA methylene chloride PEL.

This case study demonstrates how methylene chloride exposures during furniture stripping can be reduced to below the Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) of 25 ppm (as an 8-hour time-weighted average). Five surveys were conducted at one facility; the first four resulted in employee exposure geometric means from 39 to 332 ppm. For the fifth survey local exhaust ventilation was used at the stripping tank and the rinsing area, which together exhausted 138 m3/min (4860 ft3/min). Additional controls included providing adequate make-up air, adding paraffin wax to the stripping solution, raising the level of the stripping solution in the tank, and discussing good work practices with the employee. The employees' methylene chloride exposures during the fifth survey resulted in a geometric mean of 5.6 ppm with a 95% upper confidence limit of 8.3 ppm, which was found to be significantly lower than the OSHA PEL and the OSHA action level of 12.5 ppm. The cost of the ventilation system was $8900.

The effects of temperature and pressure on airborne exposure concentrations when performing compliance evaluations using ACGIH TLVs and OSHA PELs.

Occupational hygienists perform air sampling to characterize airborne contaminant emissions, assess occupational exposures, and establish allowable workplace airborne exposure concentrations. To perform these air sampling applications, occupational hygienists often compare an airborne exposure concentration to a corresponding American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit value (TLV) or an Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL). To perform such comparisons, one must understand the physiological assumptions used to establish these occupational exposure limits, the relationship between a workplace airborne exposure concentration and its associated TLV or PEL, and the effect of temperature and pressure on the performance of an accurate compliance evaluation. This article illustrates the correct procedure for performing compliance evaluations using airborne exposure concentrations expressed in both parts per million and milligrams per cubic meter. In so doing, a brief discussion is given on the physiological assumptions used to establish TLVs and PELs. It is further shown how an accurate compliance evaluation is fundamentally based on comparison of a measured work site exposure dose (derived from the sampling site exposure concentration estimate) to an estimated acceptable exposure dose (derived from the occupational exposure limit concentration). In addition, this article correctly illustrates the effect that atmospheric temperature and pressure have on airborne exposure concentrations and the eventual performance of a compliance evaluation. This article also reveals that under fairly moderate conditions of temperature and pressure, 30 degrees C and 670 torr, a misunderstanding of how varying atmospheric conditions affect concentration values can lead to a 15 percent error in assessing compliance.

The Effects of Temperature and Pressure on Airborne Exposure Concentrations When Performing Compliance Evaluations Using ACGIH TLVs and OSHA PELs

Occupational hygienists perform air sampling to characterize airborne contaminant emissions, assess occupational exposures, and establish allowable workplace airborne exposure concentrations. To perform these air sampling applications, occupational hygienists often compare an airborne exposure concentration to a corresponding American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit value (TLV) or an Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL). To perform such comparisons, one must understand the physiological assumptions used to establish these occupational exposure limits, the relationship between a workplace airborne exposure concentration and its associated TLV or PEL, and the effect of temperature and pressure on the performance of an accurate compliance evaluation. This article illustrates the correct procedure for performing compliance evaluations using airborne exposure concentrations expressed in both parts per million and milligrams per cubic meter. In so doing, a brief discussion is given on the physiological assumptions used to establish TLVs and PELs. It is further shown how an accurate compliance evaluation is fundamentally based on comparison of a measured work site exposure dose (derived from the sampling site exposure concentration estimate) to an estimated acceptable exposure dose (derived from the occupational exposure limit concentration). In addition, this article correctly illustrates the effect that atmospheric temperature and pressure have on airborne exposure concentrations and the eventual performance of a compliance evaluation. This article also reveals that under fairly moderate conditions of temperature and pressure, 30 C and 670 torr, a misunderstanding of how varying atmospheric conditions affect concentration values can lead to a 15 percent error in assessing compliance.

Time trends in exposure measurements from OSHA compliance inspections of the pulp and paper industry.

Time trends in employee exposures to the air contaminants measured by the Occupational Safety and Health Administration (OSHA) during compliance inspections of pulp and paper manufacturing facilities conducted between 1979 and 1997 were evaluated based on the measurement results stored in the OSHA Integrated Management Information System (IMIS) database. The IMIS database is among the largest sources of occupational exposure measurements available for occupational health research in the United States. The IMIS database contains the results of 3,568 personal time-weighted average (TWA) measurements for 171 air contaminants made at 524 establishments in Standard Industrial Classification (SIC) 26. An analysis of these measurements revealed an overall decrease in the total number of measurements made per year since 1991, and a decrease in the percentage of measurements by year that exceeded the OSHA permissible exposure limits (PELs). Linear regression analyses detected decreasing trends in the geometric mean concentrations by year for 33 of the 36 agents analyzed.

Area and personal airborne exposure during abatement of asbestos-containing roofing material.

Exposure to asbestos-containing material (ACM) is considered to be hazardous and can result in various occupationally related diseases (Health Effects Institute Asbestos Research HEI, 1991). This has resulted in establishment of regulations to protect those associated with this industry (Lange et al. 1996, Lange and Thomulka, 1995), although it has also been claimed that such abatement regulations are a public policy disaster in the US (Ross, 1995). The United States Occupational Safety and Health Administration (OSHA) has published regulatory standards for abatement of asbestos-containing roofing material (ACRM) and these requirements have been described in a Settlement Agreement with the roofing industry (OSHA, 1995). Under item 9 paragraph 1101(f)(2)(ii) as codified in 29 C.F.R. initial exposure monitoring is not required if a negative exposure assessment has been prepared (OSHA, 1995). Negative assessment by its self does not eliminate future air monitoring, but does allow an employer to consider that work activities of a same nature result in similar exposure levels (Lange et al. 1996). If such a negative assessment suggests exposure is below the OSHA permissible exposure limit (PEL), which is 0.1 fibers per cubic centimeter (f/cc) timeweighted average (TWA) (OSHA, 1995) many of the practices involving personal protection can be minimized. The most commonly referenced requirement involving personal protection is employment of a respirator (Lange et al. 1996). Thus, information about historical exposure levels can result in cost savings for those involved with abatement of ACRM (Lange et al. 1996). Currently there are few published studies of airborne exposure from asbestos during abatement (HEI, 1991; Lange et al. 1996; Lange and Thomulka, 1999) particularly roofing materials. Publishing exposure data can assist those in the abatement field in establishing historical information on exposure (Lange et al. 1996). This will allow development of a database for anticipated exposure during abatement of various materials and with different work practices (HEI, 1991).

A Quantitative Analysis of Factors Affecting PELs and TLVs for Carcinogens

For carcinogens, this paper provides a quantitative examination of the roles of potency and weight‐of‐evidence (WOE) in setting permissible exposure limits (PELs) at the U.S. Occupational Safety and Health Administration (OSHA) and threshold limit values (TLVs) at the private American Conference of Governmental Industrial Hygienists (ACGIH). On normative grounds, both of these factors should influence choices about the acceptable level of exposures. Our major objective is to examine whether and in what ways these factors have been considered by these organizations. A lesser objective is to identify outliers, which might be candidates for further regulatory scrutiny. Our sample (N=48) includes chemicals for which EPA has estimated a unit risk as a measure of carcinogenic potency and for which OSHA or the ACGIH has a PEL or TLV. Different assessments of the strength of the evidence of carcinogenicity were obtained from EPA, ACGIH, and the International Agency for Research on Cancer. We found that potency alone explains 49% of the variation in PELs and 62% of the variation in TLVs. For the ACGIH, WOE plays a much smaller role than potency. TLVs set by the ACGIH since 1989 appear to be stricter than earlier TLVs. We suggest that this change represents evidence that the ACGIH had responded to criticisms leveled at it in the late 1980s for failing to adopt sufficiently protective standards. The models developed here identify 2‐nitropropane, ethylene dibromide, and chromium as having OSHA PELs significantly higher than predicted on the basis of potency and WOE.