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PubMed1994

Evaluation of waste anesthetic gases, monitoring strategies, and correlations between nitrous oxide levels and health symptoms.

The release of waste anesthetic gases (WAG) in hospital operating rooms (ORs) was evaluated to determine if staff exposure to nitrous oxide exceeded the American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Value (TLV) and investigate possible correlations between symptoms and nitrous oxide exposure. The monitoring strategy consisted of nitrous oxide measurements by personal monitoring of the anesthetists and scrub nurses, and area monitoring at the exhaust grills. In addition, room ventilation rates and carbon dioxide concentrations were measured. Self-administered questionnaires were given to both the operating room personnel and staff on control wards. Nitrous oxide levels exceeded the current TLV of 50 ppm in 4 of 12 ORs. Anesthetists typically received the highest nitrous oxide exposure. There was a strong correlation (r2 = 0.90) for nitrous oxide dosimetry results between anesthetists and scrub nurses, and a fair correlation (r2 = 0.35) between area monitoring results and the anesthetists' personal exposures. Carbon dioxide levels commonly exceeded 1000 ppm on control wards. A correlation between reported symptoms and nitrous oxide exposure was not demonstrated. Reported symptoms more closely correlated with carbon dioxide levels. Nitrous oxide dosimetry of the anesthetists appears to be the only accurate strategy for monitoring human exposure to WAG in an operating room.

Air Pollutants, Occupational↗
PubMed1996

Worker exposure to endotoxin, phenolic compounds, and formaldehyde in a fiberglass insulation manufacturing plant.

Worker exposures in a fiberglass wool insulation manufacturing plant were studied. The plant used a continuous process and operated at full production during a six-week study. Area samples were used to characterize spatial variability of contaminant levels. Repeated personal samples were used to characterize the distribution and to explore within- and between-worker variability of exposures. The greatest potential for exposure to each of the contaminants was restricted to specific areas of the plant. Area geometric mean concentrations were 1 to 390 ng/m3 for endotoxin and 22 to 414 micrograms/m3 for formaldehyde. There was considerable within-area variation of endotoxin (geometric standard deviation [GSD] 2.6 to 5.5) and formaldehyde (GSD 2.0 to 4.5). Concentrations of phenolic compounds were correlated with endotoxin and were influenced by a relatively high limit of detection. The ranges of personal GM exposures across homogeneous groupings were smaller than the range for the corresponding areas (endotoxin 5.8 to 36.4 ng/m3; formaldehyde 18.1 to 67.4 micrograms/m3). Variability in personal exposure was high. Individual GSDs ranged up to 10, with the mean individual GSD of 3.4 for endotoxin, and up to 12 with mean 3.7 for formaldehyde. Suggested thresholds for acute respiratory effects of endotoxin exposure were frequently exceeded (46% of 8-hr personal samples > 10 ng/m3, 7% > 100 ng/m3). No personal samples exceeded the Occupational Safety and Health Administration permissible exposure level or the American Conference of Government Industrial Hygienists' threshold limit value for formaldehyde; however, 34% were greater than 60 micrograms/m3 and 11% were greater than 120 micrograms/m3. Thus, exposures fell in a range where important exposure-response relationship could be examined.

Air Pollutants, Occupational↗
PubMed1996

Exposure to total and respirable minerals in an abrasive manufacturing facility.

This work describes the qualitative and quantitative determination of some elements found in emery dust in air from abrasive manufacturing industry materials. The analysis of samples was done by neutron activation analysis and atomic absorption spectrometry techniques. Silicon, aluminum, chromium, iron, magnesium, calcium, bromine, manganese, zinc, lead, nickel, and vanadium elements were found. The concentration of silicon in the sampling area was 15.87 +/- 0.87 mg/m3 and 7.93 +/- 0.45 mg/m3 to personal samples, which exceed the threshold limit values (TLV). The other elements were present in concentrations lower than their respective TLVs.

Air Pollutants, Occupational↗
PubMed1996

A screening method for occupational reproductive health risk.

Most currently recognized occupational exposure limits do not consider reproductive toxicological end points consistently when establishing recommended exposure limits. In many cases the information is not available, but perhaps as often, existing data is not employed. Further, many manufacturer's material safety data sheets omit reproductive hazard information. A method for identifying potential reproductive toxins and screening levels for associated health risks useful for hazard communication and exposure control is presented. To date, the Registry of Toxic Effects of Chemical Substances lists between 5000 and 6000 chemicals, drugs, and natural substances that show a positive outcome in at least 1 reproductive effects study. This reproductive health risk assessment began with these substances. Using elements of the Environmental Protection Agency's health risk assessment process, the list was reduced to 213 chemicals during the hazard identification step. Occupational reproductive guidelines (ORGs) were developed in the dose-response evaluation step. At the time of this writing, 85% of the chemicals identified in the hazard identification step have had a screening level dose-response assessment completed. Of these, 13% are greater than or equal to a threshold limit value (TLV). The remaining 87% do not have a TLV or ORGs below the TLV. The reproductive toxins list, along with the corresponding dose-response-derived ORGs that have been completed, appears at the end of the text.

Dose-Response Relationship, Drug↗
PubMed1996

Cobalt exposure level and variability in the hard metal industry of Japan.

Cobalt, used as a binder for tungsten carbide, has been demonstrated to be toxic to the lung and to be a sensitizer of the bronchial airways among hard metal workers. To determine cobalt exposure levels in 9 job groups at a hard metal factory, 935 samples were collected from 356 workers. The arithmetic means of 8-hr time-weighted averages were more than 50 micrograms/m3 (American Conference of Governmental Industrial Hygienists' threshold limit value) in the powder preparation, rubber press, and shaping groups. The within-worker and between-worker components of exposure variation were estimated for each job group using the random effects analysis-of-variance model. The geometric standard deviations indicating the within-worker and between-worker components ranged from 1.88 to 2.77 and 1.00 to 2.31, respectively.

Air Pollutants, Occupational↗
PubMed1996

Variability in biological exposure indices using physiologically based pharmacokinetic modeling and Monte Carlo simulation.

By using physiologically based pharmacokinetic (PBPK) modeling coupled with Monte Carlo simulation, the interindividual variability in the concentrations of chemicals in a worker's exhaled breath and urine were estimated and compared with existing biological exposure indices (BEIs). The PBPK model simulated an exposure regimen similar to a typical workday, while exposure concentrations were set to equal the ambient threshold limit values (TLVs) of six industrial solvents (benzene, chloroform, carbon tetrachloride, methylene chloride, methyl chloroform, and trichloroethylene). Based on model predictions incorporating interindividual variability, the percentage of population protected was derived using TLVs as the basis for worker protection. Results showed that current BEIs may not protect the majority or all of the workers in an occupational setting. For instance, current end-expired air indices for benzene and methyl chloroform protect 95% and less than 10% of the worker population, respectively. Urinary metabolite concentrations for benzene, methyl chloroform, and trichloroethylene were also estimated. The current BEI recommendation for phenol metabolite concentration at the end-of-shift sampling interval was estimated to protect 68% of the worker population, while trichloroacetic acid (TCAA) and trichloroethanol (TCOH) concentrations for methyl chloroform exposure were estimated to protect 54% and 97%, respectively. The recommended concentration of TCAA in urine as a determinant of trichloroethylene exposure protects an estimated 84% of the workers. Although many of the existing BEIs considered appear to protect a majority of the worker population, an inconsistent proportion of the population is protected. The information presented in this study may provide a new approach for administrative decisions establishing BEIs and allow uniform application of biological monitoring among different chemicals.

Humans↗
PubMed1998

Occupational noise exposure of operators of heavy trucks.

Over 400 measurements were taken across Canada to assess the noise exposure of truck operators. The exposure of the driver was evaluated using both 3-dB (Leq) and 5-dB (L5dB) exchange rates. Driving with windows closed and radio not operating resulted in the lowest exposure. The drivers' Leq ranged from 78 to 89 dBA, with a mean of 82.7 dBA; operating the radio increased the mean by 2.8 dB; driving with the driver's side window open increased the mean exposure by 1.3 dB; and driving with the window open and operating the radio resulted in an increase of 3.9 dB. Trucks with cabs mounted over the engine appear to be quieter than standard trucks by about 2.6 dB. Operations on four-lane highways are 1.6 dB noisier than on two-lane highways, most likely as a result of higher speeds on the former. Long haul (city-to-city) operations on hilly terrain appear to be quieter than on flat terrain by about 2.2 dB, again probably indicating the strong effect of speed. Regression analysis was used to obtain relationships between a number of variables such as Leq and L5dB, etc. These measurements indicate that the exposure of a driver is almost certain to exceed the current threshold limit value for noise (85 dBA for 8 hours with a 3-dB exchange rate) when driving with the radio on and the driver's side window open. Comparable numbers in terms of L5dB are also reported.

Analysis of Variance↗
PubMed2004

Evaluation of worker exposure to asphalt roofing fumes: influence of work practices and materials.

A field study was conducted on 42 asphalt-roofing workers at 7 built-up roofing sites across the United States. Sixteen out of 42 samples show levels of exposure to asphalt fumes that exceed the current American Conference of Governmental Industrial Hygienists' (ACGIH)-recommended threshold limit value of 0.5 mg/m(3) as benzene extractable inhalable particulate. Statistically, the geometric mean of all 42 worker samples was 0.27 mg/m(3) (geometric standard deviation = 3.40), the average was 0.70 mg/m(3) (standard deviation = 1.69) and the median value was 0.24 mg/m(3). The impact of work practices is discussed including the use of a novel product that uses a polymer skin to reduce fumes from built up roofing asphalt. Its use resulted in a reduction of benzene soluble matter (BSM) of >70%. Other testing measures utilized included total particulate matter, total organic matter, simulated distillation, and fluorescence analysis. Additionally, a controlled pilot study using 16 kettle-area and 16 worker samples clearly showed that when the temperature of the kettle was reduced by 28 degrees C, there was a 38-59% reduction in fume exposure and a 54% reduction in fluorescence with standard asphalts. Reduction of BSM exposures using fuming-suppressed asphalt was also confirmed during this pilot plant study (81-92%), with fluorescence lowered by 88%. Confounding agents such as roof tear-off materials were also analyzed and their contribution to worker exposure is discussed.

Construction Materials↗
PubMed2004

Adaptation and evaluation of a personal electronic nose for selective multivapor analysis.

The evaluation of a commercial, belt-mountable "electronic nose" modified for the rapid recognition and quantification of individual solvent vapors and simple vapor mixtures at low ppm concentrations is described. Marketed under the name VaporLab this direct-reading instrument was designed for qualitative determinations of the presence or absence of selected individual vapors and was adapted in this study for quantitative determinations of vapors and vapor-mixture components. Vapor samples are concentrated on a small adsorbent bed and then thermally desorbed for analysis by an array of four polymer-coated surface acoustic wave sensors. Tests were performed with 13 organic solvent vapors individually and in selected binary, ternary, and quaternary mixtures at concentrations ranging from 0.1 to 12 times the respective American Conference of Governmental Industrial Hygienists' (ACGIH) threshold limit value (TLV). Pattern recognition analyses yielded a library of response patterns to which subsequent actual and virtual (i.e., Monte-Carlo simulated) samples were compared to assess performance. Limits of detection >0.025 x TLV are achieved (based on the most sensitive sensors) for 0.25 L of preconcentrated air samples collected over a 2-min period. Individual vapors from different functional group classes can be recognized, quantified, and discriminated from other vapors with little error, and discrimination of the components of binary mixtures is possible where the component vapor response patterns are sufficiently different. Within-class individual vapor and binary-mixture discriminations are more difficult and most ternary and higher-order mixtures could not be analyzed with acceptable accuracy. Changes in ambient humidity have no effect on responses and changes in temperature lead to well-behaved and compensable changes in responses. Tests of fluctuating concentrations demonstrate the capability for accurately tracking short-term variations in exposure. Overall, results suggest that this instrument could serve effectively as a personal exposure monitor in previously characterized occupational environments with proper revisions in design.

Air Pollution, Indoor↗
PubMed2005

Evaluation of potential toxicity from co-exposure to three CNS depressants (toluene, ethylbenzene, and xylene) under resting and working conditions using PBPK modeling.

Under OSHA and American Conference of Governmental Industrial Hygienists (ACGIH) guidelines, the mixture formula (unity calculation) provides a method for evaluating exposures to mixtures of chemicals that cause similar toxicities. According to the formula, if exposures are reduced in proportion to the number of chemicals and their respective exposure limits, the overall exposure is acceptable. This approach assumes that responses are additive, which is not the case when pharmacokinetic interactions occur. To determine the validity of the additivity assumption, we performed unity calculations for a variety of exposures to toluene, ethylbenzene, and/or xylene using the concentration of each chemical in blood in the calculation instead of the inhaled concentration. The blood concentrations were predicted using a validated physiologically based pharmacokinetic (PBPK) model to allow exploration of a variety of exposure scenarios. In addition, the Occupational Safety and Health Administration and ACGIH occupational exposure limits were largely based on studies of humans or animals that were resting during exposure. The PBPK model was also used to determine the increased concentration of chemicals in the blood when employees were exercising or performing manual work. At rest, a modest overexposure occurs due to pharmacokinetic interactions when exposure is equal to levels where a unity calculation is 1.0 based on threshold limit values (TLVs). Under work load, however, internal exposure was 87%higher than provided by the TLVs. When exposures were controlled by a unity calculation based on permissible exposure limits (PELs), internal exposure was 2.9 and 4.6 times the exposures at the TLVs at rest and workload, respectively. If exposure was equal to PELs outright, internal exposure was 12.5 and 16 times the exposure at the TLVs at rest and workload, respectively. These analyses indicate the importance of (1) selecting appropriate exposure limits, (2) performing unity calculations, and (3) considering the effect of work load on internal doses, and they illustrate the utility of PBPK modeling in occupational health risk assessment.

Animals↗
PubMed2006

Airborne crystalline silica concentrations at coal-fired power plants associated with coal fly ash.

This study presents measurements of airborne concentrations of respirable crystalline silica in the breathing zone of workers who were anticipated to encounter coal fly ash. Six plants were studied; two were fired with lignite coal, and the remaining four plants used bituminous and subbituminous coals. A total of 108 personal breathing zone respirable dust air samples were collected. Bulk samples were also collected from each plant site and subjected to crystalline silica analysis. Airborne dust particle size analysis was measured where fly ash was routinely encountered. The results from bituminous and subbituminous fired plants revealed that the highest airborne fly ash concentrations are encountered during maintenance activities: 0.008 mg/m3 to 96 mg/m3 (mean of 1.8 mg/m3). This group exceeded the threshold limit values (TLV) in 60% of the air samples. During normal production activities, airborne concentrations of crystalline silica ranged from nondetectable to 0.18 mg/m3 (mean value of 0.048 mg/m3). Air samples collected during these activities exceeded the current and proposed TLVs in approximately 54% and 65% of samples, respectively. Limited amounts of crystalline silica were detected in samples collected from lignite-fired plants, and approximately 20% of these air samples exceeded the current TLV. Particle size analysis in areas where breathing zone air samples were collected revealed mass median diameters typically between 3 microm and 8 microm. Bulk and air samples were analyzed for all of the common crystalline silica polymorphs, and only alpha quartz was detected. As compared with air samples, bulk samples from the same work areas consistently yielded lower relative amounts of quartz. Controls to limit coal fly ash exposures are indicated during some normal plant operations and during episodes of short term, but high concentrations of dust that may be encountered during maintenance activities, especially in areas where ash accumulations are present.

Air Pollutants, Occupational↗
PubMed2006

A preliminary study on gram-negative bacteria (GNB) and their endotoxins in a gin house in India.

The presence of byssinosis, an occupational disease found among cotton mill workers, has been well documented in different parts of the world. The disease develops due to exposure to environmental cotton dust. Evidence suggests that the causative agent for the disease is gram-negative bacteria (GNB) and their endotoxins present on the cotton fibers. An investigation was carried out in a gin house in western India. Environmental dust samples were collected by vertical elutriator (VE). Airborne dust concentrations were very high in the working environment: 2.11 mg/m3 in ginning and 0.95 mg/m3 in the press department (p < 0.05), which was higher than the threshold limit value collected by VE (0.2 mg/m3), and higher than the permissible exposure limit for respirable dust (0.5 mg/m3 for nontextile industries using cotton). In the office control site, the dust concentration was 0.31 mg/m3. The Occupational Safety and Health Administration's cotton dust standard permissible exposure limit for respirable dust is 0.2 mg/m3 in yarn manufacturing, 0.75 mg/m3 in slashing and weaving, and 0.5 mg/m3 in nontextile industries using cotton. These samples also showed high concentrations of airborne endotoxin (p < 0.001) in ginning and pressing (2.77 and 1.52 micro g/m3) compared with the office control site (0.009 micro g/m3 measured by Limulus amoebocyte lysate technique). Total enumeration of airborne GNB was carried out qualitatively by the petri plate exposure method and quantitatively by an Andersen 6-stage viable sampler and VE. GNB were recovered in quite high numbers. Among all the GNB, Enterobacter agglomerans were the dominant bacterial flora. Results indicate that gin workers are occupationally exposed to airborne GNB and endotoxins, and require masks.

Air Pollutants, Occupational↗
PubMed2001

Solvent exposures in screen printing shops.

A comprehensive description of working conditions, exposure patterns for organic solvents, and related health symptoms among workers in ten small screen printing companies located in Seattle, Washington, is presented. Sampling methods included continuous area monitoring, grab sampling, personal sampling, and time study observation. A total of 27 workers were observed and monitored for solvent exposure. Short-term peak exposures were characterized in terms of magnitude, duration and repetition, and their contribution to time weighted average (TWA) exposures were evaluated. A health questionnaire addressing the symptoms potentially attributable to solvents was used to investigate the possible health effects from exposure. Significant differences in the prevalence of headaches, dizziness, intoxication, and dry skin (p < 0.01) were reported among workers who had some solvent exposure compared with the referent group that was not exposed. Exposed workers were also more likely to report fatigue, loss of strength in the arms and hands, difficulty concentrating, sore throat, and a low alcohol tolerance. The study documented highly variable levels of solvent exposures. Screen printing workers in different companies, while performing the same basic tasks, had time weighted average (TWA) exposures ranging from 2% to 100% of the recommended threshold limit value (TLV) for mixtures. Continuous monitoring indicated that high short-term exposures are responsible for the bulk of TWA exposures. Grab samples and continuous monitoring verified that recommended Short Term Exposure Limits (STEL) for individual solvents may be exceeded on a routine basis. Frequent skin contact with solvents was also observed. Health problems in this industry and other small industries using organic solvents may result from these complex patterns of exposure.

Air Pollution, Indoor↗
PubMed2002

Solid phase microextraction: measurement of volatile organic compounds (VOCs) in Dhaka City air pollution.

A solid phase microextraction (SPME) technique was applied for the sampling of volatile organic compounds (VOCs) in ambient air polluted by two stroke autorickshaw engines and automobile exhausts in Dhaka city, Bangladesh. Analysis was carried out by capillary gas chromatography (GC) and GC-mass spectrometry (MS). The methodology was tested by insitu sampling of an aromatic hydrocarbon mixture gas standard with a precision of +/-5% and an average accuracy of 1-20%. The accuracy for total VOCs concentration measurement was about 7%. VOC's in ambient air were collected by exposing the SPME fiber at four locations in Dhaka city. The chromatograms showed signature similar to that of unburned gasoline (petrol) and weathered diesel containing more than 200 organic compounds; some of these compounds were positively identified. These are normal hydrocarbons pentane (n-C5H2) through nonacosane (n-C29H60), aromatic hydrocarbons: benzene, toluene, ethylbenzene, n-propylbenzene, n-butylbenzene, 1,3,5-trimethylbenzene, xylenes, and 1-isocyanato-3-methoxybenzene. Two samples collected near an autorickshaw station contained 783000 and 1479000 microg/m3 of VOCs. In particular, the concentration of toluene was 50-100 times higher than the threshold limiting value of 2000 microg/m3. Two other samples collected on street median showed 135000 microg/m3 and 180000 microg/m3 of total VOCs. The method detection limit of the technique for most semi-volatile organic compounds was 1 microg/m3.

Air Pollutants↗
PubMed1989

Effect of respiratory protective equipment on exposure to asbestos fibres during removal of asbestos insulation.

Asbestos concentrations were measured within powered respirators used by workers involved in the removal of asbestos-containing insulation. Fibre concentrations within the protective gear appeared to be above the Dutch threshold limit value for crocidolite (0.2 f cm-3). Possible sources of exposure were analysed and measures were taken to improve the situation. After this, the fibre concentrations in the breathing area were reduced and were below the Dutch concentration limit.

Air Pollutants, Occupational↗
PubMed2002

Respirable crystalline silica dust exposure during concrete finishing (grinding) using hand-held grinders in the construction industry.

Studies reporting the findings of exposure to crystalline silica dust during concrete finishing in construction settings are scarce due to the dynamic nature of the activity and the existence of many confounding factors. This study was initiated to explore the issue. A total of 49 personal respirable dust samples were collected during concrete finishing while workers used hand-held grinders. Only 15 (31%) of the grinders were equipped with local exhaust ventilation (LEV) systems. The confounding factors (e.g. wind velocity, wind direction, relative humidity and ambient temperature) were determined. To make the sampling task-specific, air sampling was activated only during actual grinding. Task-specific sampling times during each work shift ranged from 10 to 200 min. The concentration of total respirable particulate ranged from 0.34 to 81 mg/m3, with a mean +/- SD of 18.6 +/- 20.4 mg/m3, and the concentration of crystalline silica in the samples ranged from 0.02 to 7.1 mg/m3, with a mean +/- SD of 1.16 +/- 1.36 mg/m3. LEV on the grinders reduced the silica dust level significantly (P < 0.01) compared to grinders without LEV. Increased wind velocity also reduced the silica dust concentration significantly (P < 0.03). Working upwind reduced the exposure to silica dust compared to working downwind, but the difference was not statistically significant. The time-weighted average concentration of silica dust in 69% of the samples exceeded the current recommended threshold limit value of 0.05 mg/m3, indicating a strong need to devise methods for controlling workers' exposure to crystalline silica dust during concrete finishing activities.

Air Movements↗
PubMed2004

Detailed exposure assessment for a molecular epidemiology study of benzene in two shoe factories in China.

OBJECTIVES: We carried out a detailed exposure assessment of benzene and toluene in two shoe factories in Tianjin, China. Our goal was to identify workers with a broad range of benzene exposures, for an epidemiologic study relating exposure to early biologic effects. METHODS: A comprehensive exposure survey program was initiated. Over a period of 16 months, 2783 personal solvent exposure samples were collected in two workplaces from 250 workers. Mixed-effects models were used to identify factors affecting exposure. Principal component analyses (PCA) and subsequent regression analyses on the scores of the identified principal components were used to relate potential co-exposures to various exposure sources present in the workplace. RESULTS: The mean benzene exposure level was 21.86 p.p.m. (10th-90th percentiles 5.23-50.63 p.p.m.) in the smaller shoe factory (factory A) and 3.46 p.p.m. (10th-90th percentiles 0.20-7.00 p.p.m.) in the larger shoe factory (factory B). Within-factory exposure levels differed among job titles and were higher for subjects directly involved in handling glues. In contrast, mean toluene levels were relatively similar in the two factories (factory A, 9.52 p.p.m.; factory B, 15.88 p.p.m.). A seasonal trend was identified for both benzene and toluene in factory B. This could be explained in part by changes in air movement and ventilation patterns occurring during the year. A seasonal trend was not present in the smaller shoe factory, where general ventilation was absent. Supplemental analysis showed that exposure levels to other hydrocarbons were low (< or =5 p.p.m.), less than 5% of their respective ACGIH threshold limit values, and generally comparable in the two factories. PCA showed that co-exposures in factory B could largely be explained by glue sources that were used in distinct areas in the workplace. CONCLUSIONS: We demonstrated the occurrence of a broad range of benzene exposure levels in two shoe manufacturing factories in Tianjin, China. Benzene and toluene exposures were determined in part by the degree of contact with glues, the benzene and toluene content of each glue, air movement and ventilation patterns. The availability of long-term monthly personal monitoring data provides an excellent opportunity to estimate individual exposures at different times during the 1 yr period of observation.

Adhesives↗
PubMed2004

The efficacy of local exhaust ventilation for controlling dust exposures during concrete surface grinding.

This study assessed the effectiveness of a commercially available local exhaust ventilation (LEV) system for controlling respirable dust and crystalline silica exposures during concrete grinding activities. Surface grinding was conducted at six commercial building construction sites in Seattle, WA, by cement masons. Time-integrated filter samples and direct reading respirable dust concentrations were collected using a cyclone in line with a direct reading respirable dust monitor. Personal exposure levels were determined with and without LEV, one sample directly after the other. A total of 28 paired samples were collected in which three different dust collection shroud configurations were tested. Data obtained with a direct reading respirable dust monitor were adjusted to remove non-work task-associated dust exposures and was subsequently used to calculate the exposure reduction achieved. The application of LEV resulted in a reduction in the overall geometric mean respirable dust exposure from 4.5 to 0.14 mg/m(3), a mean exposure reduction of 92%. Despite the effective control of dust generated during surface grinding, 22 and 26% of the samples collected while LEV was being used were greater than the 8 h time-weighted average permissible exposure limit (Occupational Safety and Health Administration) and threshold limit value (American Congress of Governmental Industrial Hygienists) for respirable crystalline silica, respectively.

Construction Materials↗