Annals of Occupational Hygiene - recent issues

Toward Better Exposure Assessment Strategies--The New NIOSH Initiative

Ramachandran, G. — 2008-07-08

NIOSH has embarked on a project to update its exposure sampling strategies manual. The current NIOSH strategy has a number of limitations. This is an opportunity to develop a robust and comprehensive exposure assessment strategy. Some of the key features of such a strategy are outlined. The importance of accurate professional judgment and exposure modeling is discussed. Bayesian statistics offers a rational approach to integrating sampling data, professional judgments, and the outputs of exposure models in a comprehensive framework.

Variability in Endotoxin Exposure Levels and Consequences for Exposure Assessment

2008-07-08

Objectives: Workers in many industries are exposed to endotoxins, which may cause adverse health effects. In exposure assessment, information about exposure variability is essential. However, variability in exposure has rarely been investigated for biological agents and more specifically for endotoxin. Therefore, variance components and determinants of exposure were studied in a large database with >2000 endotoxin measurements.

Methods: Data from 10 individual studies were combined to create a database with 2010 personal inhalable dust and endotoxin measurements, of which 1650 were repeated measurements. Exposure groups were defined based on job codes. Between- and within-worker variance components were estimated for different grouping strategies, and determinants of exposure were studied using mixed effects models.

Results: Inhalable dust and endotoxin exposure levels are summarized for 46 industries and 4 broadly defined sectors. The between-worker variability exceeded the within-worker variability overall and within sectors and subsectors, and variance components were larger for endotoxin than for dust. Between-worker variability also exceeded within-worker variability in nearly half of the exposure groups based upon industries or job code within industries for endotoxin exposure and in 10% of the groups for dust exposure. Among other things, dustiness of the process, contact with animals, bulk production, presence of plant material or a cyclic process appeared as determinants of exposure, which largely explained the between-worker variability.

Conclusions: Exposure groups were much less homogeneous for endotoxin exposure than for dust exposure. This is distinctly different than for chemical exposure. Large variability in measured exposure levels is inherent to endotoxin exposure, which is caused in part by determinants that influence growth of microorganisms. These findings have major consequences for the design of future occupational intervention and epidemiological studies. The measurement effort needs to be greater than exposure assessment for chemical agents which demonstrate lower exposure variability, especially when evaluating endotoxin exposure for compliance testing. The established determinants of exposure give direction for potential exposure control, although more information about determinants of day-to-day variability in exposure is still needed to be able to effectively control endotoxin exposure.

Exposure to Fibres, Crystalline Silica, Silicon Carbide and Sulphur Dioxide in the Norwegian Silicon Carbide Industry

Foreland, S., Bye, E., Bakke, B., Eduard, W. — 2008-07-08

Objectives: The aim of this study was to assess personal exposure to fibres, crystalline silica, silicon carbide (SiC) and sulphur dioxide in the Norwegian SiC industry.

Methods: Approximately 720 fibre samples, 720 respirable dust samples and 1400 total dust samples were collected from randomly chosen workers from the furnace, processing and maintenance departments in all three Norwegian SiC plants. The respirable dust samples were analysed for quartz, cristobalite and non-fibrous SiC content. Approximately 240 sulphur dioxide samples were collected from workers in the furnace department.

Results: The sorting operators from all plants, control room and cleaning operators in Plant A and charger, charger/mix and payloader operators in Plant C had a geometric mean (GM) of fibre exposure above the Norwegian occupational exposure limit (OEL) (0.1 fibre cm^–3). The cleaner operators in Plant A had the highest GM exposure to respirable quartz (20 µg m^–3). The charger/mix operators in Plant C had the highest GM exposure to respirable cristobalite (38 µg m^–3) and the refinery crusher operators in Plant A had the highest GM exposure to non-fibrous SiC (0.65 mg m^–3). Exposure to the crystalline silica and non-fibrous SiC was generally low and between 0.4 and 2.1% of the measurements exceeded the OELs. The cleaner operators in Plant A had the highest GM exposure to respirable dust (1.3 mg m^–3) and total dust (21 mg m^–3). GM exposures for respirable dust above the Norwegian SiC industry-specific OEL of 0.5 mg m^–3 were also found for refinery crusher operators in all plants and mix, charger, charger/mix and sorting operators in Plant C. Only 4% of the total dust measurements exceeded the OEL for nuisance dust of (10 mg m^–3). Exposure to sulphur dioxide was generally low. However, peaks in the range of 10–100 p.p.m. were observed for control room and crane operators in Plants A and B and for charger and charger/mix operators in Plant C.

Conclusion: Workers in the SiC industry are exposed to a mixture of several agents including SiC fibres, quartz, cristobalite, non-fibrous SiC and sulphur dioxide. Exposure levels were generally below the current Norwegian OELs; however, high exposure to fibres and respirable dust still occurs in the furnace department.

Trends in Occupational Exposure to Styrene in the European Glass Fibre-Reinforced Plastics Industry

2008-07-08

Aim: This study presents temporal trends of styrene exposure for workers in the European glass fibre-reinforced plastics (GRP) industry during the period 1966–2002.

Methods: Data of personal styrene exposure measurements were retrieved from reports, databases and peer-reviewed papers. Only sources with descriptive statistics of personal measurements were accepted. The styrene exposure data cover personal air samples and biological monitoring data, that is, urinary styrene metabolites (mandelic acid and/or phenylglyoxylic acid) and styrene in blood. Means of series of measurements were categorized by year, country, production process, job and sampling strategy. Linear mixed models were used to identify temporal trends and factors affecting exposure levels.

Results: Personal exposure measurements were available from 60 reports providing data on 24145 1–8-h time-weighted average shift personal air samples. Available data of biological exposure indicators included measurements of mandelic acid in post-shift urine (6361 urine samples being analysed). Trend analyses of the available styrene exposure data showed that the average styrene concentration in the breathing zone of open-mould workers in the European GRP industry has decreased on average by 5.3% per year during the period 1966–1990 and by only 0.4% annually in the period after 1990. The highest exposures were measured in Southern Europe and the lowest exposures in Northern Europe with Central Europe in between. Biological indicators of styrene (mandelic acid in post-shift urine) showed a somewhat steeper decline (8.9%), most likely because urine samples were collected in companies that showed a stronger decrease of styrene exposure in air than GRP companies where no biological measurements were carried out.

Visualization of the Airflow around a Life-Sized, Heated, Breathing Mannequin at Ultralow Windspeeds

Schmees, D. K., Wu, Y.-H., Vincent, J. H. — 2008-07-08

During the past two decades, there has been considerable progress in developing particle size-selective criteria for aerosol sampling and exposure assessment that relate more realistically to actual human exposures than previously. An important aspect has been the aspiration efficiency—the ‘inhalability’—with which particles enter through the nose and mouth of aerosol-exposed individuals during breathing. Most of the reported experiments to determine inhalability have been conducted in wind tunnels with life-sized, breathing mannequins, for windspeeds from 0.5 m s^–1 and above. A few experiments have been reported for calm air. However, nothing has been reported for the intermediate range from 0.5 m s^–1 downward, and it so happens—as we now know—that this corresponds to most industrial workplaces. The research described in this paper represents a first step toward filling this knowledge gap. It focuses on identifying the features of the airflow near the mannequin at such low windspeeds that might have important influences on the nature of particle transport, and hence on inhalability, and eventually the performances of personal aerosol samplers mounted in the breathing zone. We have carried out flow visualization experiments for the realistic range of windspeeds indicated, investigating specifically the effect of the air jet released into the freestream during expiration and the effect of the upward-moving boundary layer near the body associated with the buoyancy of air in that region as a result of heat received from the warm body. We set out to identify the combinations of conditions—external windspeed, breathing mode (nose versus mouth breathing), breathing rate and body temperature—where such factors need to be taken into account. We developed an experimental system that allowed the visualization of smoke traces, providing very good observation of how the flow was modified as conditions changed. From inspection of a large number of moving pictures, we developed a matrix of regimes—categorized by windspeed and breathing rate—where the effect of the expired air is sufficient to permanently and seriously destabilize the airflow approaching the mannequin. It was found that the effect of body temperature was minimal. Such results will be important in the interpretation of current and future inhalability experiments carried out at realistic low windspeeds.

Size-Separated Sampling and Analysis of Isocyanates in Workplace Aerosols. Part I. Denuder--Cascade Impactor Sampler

Dahlin, J., Spanne, M., Karlsson, D., Dalene, M., Skarping, G. — 2008-07-08

Isocyanates in the workplace atmosphere are typically present both in gas and particle phase. The health effects of exposure to isocyanates in gas phase and different particle size fractions are likely to be different due to their ability to reach different parts in the respiratory system. To reveal more details regarding the exposure to isocyanate aerosols, a denuder–impactor (DI) sampler for airborne isocyanates was designed. The sampler consists of a channel-plate denuder for collection of gaseous isocyanates, in series with three-cascade impactor stages with cut-off diameters (d₅₀) of 2.5, 1.0 and 0.5 µm. An end filter was connected in series after the impactor for collection of particles smaller than 0.5 µm. The denuder, impactor plates and the end filter were impregnated with a mixture of di-n-butylamine (DBA) and acetic acid for derivatization of the isocyanates. During sampling, the reagent on the impactor plates and the end filter is continuously refreshed, due to the DBA release from the impregnated denuder plates. This secures efficient derivatization of all isocyanate particles. The airflow through the sampler was 5 l min^–1. After sampling, the samples containing the different size fractions were analyzed using liquid chromatography-mass spectrometry (LC-MS)/MS. The DBA impregnation was stable in the sampler for at least 1 week. After sampling, the DBA derivatives were stable for at least 3 weeks. Air sampling was performed in a test chamber (300 l). Isocyanate aerosols studied were thermal degradation products of different polyurethane polymers, spraying of isocyanate coating compounds and pure gas-phase isocyanates. Sampling with impinger flasks, containing DBA in toluene, with a glass fiber filter in series was used as a reference method. The DI sampler showed good compliance with the reference method, regarding total air levels. For the different aerosols studied, vast differences were revealed in the distribution of isocyanate in gas and different particle size fractions. The opportunity to obtain detailed information regarding the distribution of isocyanates in aerosols in addition to the total air levels make the DI sampler a valuable tool for studies of possible health effects in the different parts of the airways.

Size-Separated Sampling and Analysis of Isocyanates in Workplace Aerosols--Part II: Aging of Aerosols from Thermal Degradation of Polyurethane

Dahlin, J., Spanne, M., Dalene, M., Karlsson, D., Skarping, G. — 2008-07-08

A new type of isocyanate sampler has been used to investigate aging aerosols generated during thermal degradation of polyurethane (PUR). The sampler consists of a denuder connected in series with a three-stage cascade impactor and a filter. The denuder collects gas-phase isocyanates. The three impactor stages had cut-off diameters (d₅₀) of 2.5, 1.0 and 0.5 µm, respectively. The end filter collects particles <0.5 µm. For derivatization of isocyanates in the sampler, di-n-butylamine mixed with an equimolar amount of acetic acid was used for impregnation of the sampler stages. Consecutive sampling using three denuder–impactor samplers was performed in a test chamber, with a total sampling time of 9 min. Analysis of air samples was performed using liquid chromatography-mass spectrometry (LC-MS)/MS. Particle size measurements were performed using a scanning mobility particle sizer (SMPS). A time-dependent behavior was observed for aromatic diisocyanates during aging of the aerosol. Thermal degradation of different PUR materials showed different distribution of isocyanates between gas and particles. Aromatic diisocyanates (toluene diisocyanate (TDI) and methylene diphenyl diisocyanate) were initially in gas phase and associated to very small particles. After a few minutes most of these isocyanates were associated with particles <1 µm. Monoisocyanates and hexamethylene diisocyanate (HDI) were not found to be associated with particles.

Filter Performance of N99 and N95 Facepiece Respirators Against Viruses and Ultrafine Particles

2008-07-08

The performance of three filtering facepiece respirators (two models of N99 and one N95) challenged with an inert aerosol (NaCl) and three virus aerosols (enterobacteriophages MS2 and T4 and Bacillus subtilis phage)—all with significant ultrafine components—was examined using a manikin-based protocol with respirators sealed on manikins. Three inhalation flow rates, 30, 85, and 150 l min^–1, were tested. The filter penetration and the quality factor were determined. Between-respirator and within-respirator comparisons of penetration values were performed. At the most penetrating particle size (MPPS), >3% of MS2 virions penetrated through filters of both N99 models at an inhalation flow rate of 85 l min^–1. Inhalation airflow had a significant effect upon particle penetration through the tested respirator filters. The filter quality factor was found suitable for making relative performance comparisons. The MPPS for challenge aerosols was <0.1 µm in electrical mobility diameter for all tested respirators. Mean particle penetration (by count) was significantly increased when the size fraction of <0.1 µm was included as compared to particles >0.1 µm. The filtration performance of the N95 respirator approached that of the two models of N99 over the range of particle sizes tested (~0.02 to 0.5 µm). Filter penetration of the tested biological aerosols did not exceed that of inert NaCl aerosol. The results suggest that inert NaCl aerosols may generally be appropriate for modeling filter penetration of similarly sized virions.

Linking Expert Judgement and Trends in Occupational Exposure into a Job-Exposure Matrix for Historical Exposure to Asbestos in The Netherlands

Swuste, P., Dahhan, M., Burdorf, A. — 2008-07-08

The aim of this article was to describe the structure and content of a job-exposure matrix (JEM) for historical asbestos exposure in The Netherlands. The JEM contained 309 occupational job title groups in 70 branches of industry during 10 periods of 5 years during 1945–1994, resulting in 3090 evaluations. Dutch sources on asbestos exposure measurements provided quantitative guidance for 69 evaluations (2.2%) in 25 occupational title groups. In addition, three databases from the UK Health and Safety Executive contributed to 222 evaluations (7.2%) and several other sources aided in another 133 evaluations (4.3%). These evaluations resulted in seven categories of exposure levels for all 3090 combinations of occupational title groups and periods. A verification process with five experts was used to adjust the assignments of exposure categories. The trends in exposure patterns over time were described in relation to production activities, operational control measures and the presence of dust control measures. For the majority of asbestos-related diseases in the past decades, reliable information on their historical exposure patterns was lacking. The limited availability of exposure measurements in the past illustrates the need for a structured assessment of historical asbestos exposure through a JEM.

Exposure to Bioaerosols in Poultry Houses at Different Stages of Fattening; Use of Real-time PCR for Airborne Bacterial Quantification

Oppliger, A., Charriere, N., Droz, P.-O., Rinsoz, T. — 2008-07-08

Previous studies have demonstrated that poultry house workers are exposed to very high levels of organic dust and consequently have an increased prevalence of adverse respiratory symptoms. However, the influence of the age of broilers on bioaerosol concentrations has not been investigated. To evaluate the evolution of bioaerosol concentration during the fattening period, bioaerosol parameters (inhalable dust, endotoxin and bacteria) were measured in 12 poultry confinement buildings in Switzerland, at three different stages of the birds’ growth; samples of air taken from within the breathing zones of individual poultry house employees as they caught the chickens ready to be transported for slaughter were also analysed. Quantitative polymerase chain reaction (Q-PCR) was used to assess the quantity of total airborne bacteria and total airborne Staphylococcus species. Bioaerosol levels increased significantly during the fattening period of the chickens. During the task of catching mature birds, the mean inhalable dust concentration for a worker was 26 ± 1.9 mg m^–3 and endotoxin concentration was 6198 ± 2.3 EU m^–3 air, >6-fold higher than the Swiss occupational recommended value (1000 EU m^–3). The mean exposure level of bird catchers to total bacteria and Staphylococcus species measured by Q-PCR is also very high, respectively, reaching values of 53 (±2.6) x 10⁷ cells m^–3 air and 62 (±1.9) x 10⁶ m^–3 air. It was concluded that in the absence of wearing protective breathing apparatus, chicken catchers in Switzerland risk exposure beyond recommended limits for all measured bioaerosol parameters. Moreover, the use of Q-PCR to estimate total and specific numbers of airborne bacteria is a promising tool for evaluating any modifications intended to improve the safety of current working practices.

Exposure Assessment of Workers to Airborne PCDD/Fs, PCBs and PAHs at an Electric Arc Furnace Steelmaking Plant in the UK

Aries, E., Anderson, D. R., Fisher, R. — 2008-06-05

Occupational exposure studies were undertaken at a UK electric arc furnace (EAF) steelmaking plant to investigate the exposure of workers via inhalation to dioxins, polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) including benzo[a]pyrene (B[a]P). Surveys were undertaken in areas including the melting shop, the casting department and a furnace control cabin. The highest concentrations of dioxins and PCBs were found inside the melting shop nearby EAFs, whereas dioxin and PCB concentrations in the casting department and inside the control cabin were significantly lower. Risk characterization was carried out by comparing the daily intake of dioxins and PCBs through inhalation with the recommended tolerable daily intake (TDI). Health risk assessments were also carried out by combining exposure data with inhalation cancer potency factors to quantify the cancer risk. For the most exposed category of workers (melting shop workers), the estimated daily intake via inhalation was 0.35 pg WHO-TEQ kg^–1 body weight (bw) in the worst case scenario. Considering that the average UK adult exposure to dioxins from the diet is 1.8 pg WHO-TEQ kg^–1 bw day^–1, the results indicated that the estimated daily intake of dioxins via inhalation at the EAF would not result in the recommended range of the TDI (1–4 pg WHO-TEQ kg^–1 bw day^–1) being exceeded. Cancer risks for a 40-year occupational exposure period were determined by multiplying the inhalation dose by the inhalation cancer potency factor for 2,3,7,8-tetrachlorodibenzo-p-dioxin. For melting shop workers, cancer risks from exposure to dioxins and PCBs ranged from 2.05 x 10^–5 to 7.54 x 10^–5. Under most regulatory programmes, excess cancer risks between 1.0 x 10^–4 and 1.0 x 10^–6 indicate an acceptable range of excess cancer risk, suggesting a limited risk from dioxin exposure for workers in the EAF plant. For the calculation of excess cancer risks, no account has been taken of the protection provided by protective respiratory equipment worn by EAF workers. If personal protective equipments were taken into consideration, it is likely that the excess cancer risks for EAF workers would have been lower and considered as negligible. The highest concentrations of PAHs were found in the melting shop and the casting areas of the plant. In the melting shop area, B[a]P concentrations ranged from 1.4 to 24.5 ng m^–3, with a mean value of 7 ng m^–3. No workplace exposure limits have been published by the Health and Safety Executive in the UK for PAHs; however, the B[a]P concentrations found were below the limit value of 150 ng m^–3 (8-h time-weighted average) specified for workplace exposure in France. Exposure assessment of workers to PAHs via inhalation was carried out by calculating a potential cancer risk considering a 40-year occupational exposure period and B[a]Peq concentrations. Estimated cancer risks for the most exposed category of workers (i.e. melting shop workers) ranged from 3.66 x 10^–6 to 1.64 x 10^–5. The cancer risks determined in this study were well within an acceptable range of excess cancer risk of 1.0 x 10^–4 to 1.0 x 10^–6, specified by the US Environmental Protection Agency.

Determinants of Wood Dust Exposure in the Danish Furniture Industry--Results from Two Cross-Sectional Studies 6 Years Apart

2008-06-05

Objectives: This paper investigates determinants of wood dust exposure and trends in dust level in the furniture industry of Viborg County, Denmark, using data from two cross-sectional studies 6 years apart.

Methods: During the winter 1997/1998, 54 factories were visited (hereafter study 1). In the winter 2003/2004, 27 factories were revisited, and personal dust measurements were repeated. In addition, 14 new factories were included (hereafter study 2). A total of 2303 woodworkers participated in study 1, and 2358 measurements from 1702 workers were available. From study 2, 1581 woodworkers participated and 1355 measurements from 1044 workers were available. Information on occupational variables describing potential determinants of exposures like work task, exhaust ventilation, enclosure and cleaning procedures were collected. A total of 2627 measurements and 1907 persons were included in the final mixed model in order to explore determinants of exposure and trends in dust level.

Results: The overall inhalable wood dust concentration (geometric means (geometric standard deviation)) has decreased from 0.95 mg/m³ (2.05) in study 1 to 0.60 mg/m³ (1.63) in study 2, representing a 7% annual decrease in dust concentration, which was confirmed in the mixed model. From study 1 to study 2 there has been a change towards less manual work and more efficient cleaning methods, but on the contrary also more inadequate exhaust ventilation systems. The following determinants were found to ‘increase’ dust concentration: sanding; use of compressed air; use of full-automatic machines; manual work; cleaning of work pieces with compressed air; kitchen producing factories and small factories (<20 employees). The following determinants of exposure were found to ‘decrease’ dust concentration: manual assembling/packing; sanding with adequate exhaust ventilation; adequate exhaust ventilation; vacuum cleaning of machines and special cleaning staff.

Conclusions: Despite a substantial drop in the dust concentration during the last 6 years in the furniture industry in Viborg County, further improvements are possible. There should be more focus on improved exhaust ventilation, professional cleaning methods and avoiding use of compressed air.

GABIE and Perkin Elmer Passive Sampler Performance under Fluctuating Concentration Conditions

Langlois, E. — 2008-06-05

Passive sampling is an approved and accurate method for the assessment of organic compound exposure over long sampling time. This method could be very convenient for the short-time exposure assessment, but passive samplers have to be validated for this use. In this article, the behaviour of two commercial passive samplers (GABIE and Perkin Elmer) under fluctuant concentration conditions is studied. Artificial atmospheres were produced in the laboratory and passive samplers were exposed to different concentration profiles. Both theoretical and experimental results detailed in the paper underline the capability of these two samplers to assess pollutant exposure either when the concentration is unsteady or when the sampling time is short. Then, a suitable sampling strategy is proposed for the assessment of short-term exposure, based on the association of a direct reading photoionization device and passive sampler.

Diffusive Sampling of C7-C16 Hydrocarbons in Workplace Air: Uptake Rates, Wall Effects and Use in Oil Mist Measurements

Simpson, A. T., Wright, M. D. — 2008-06-05

The measurement of semi-volatile hydrocarbons in workplace air is complicated by their readiness to condense to form aerosols or adsorb on to surfaces. The diffusive sampling and analysis by thermal desorption of alkanes up to hexadecane was investigated with the aim of quantifying vapour from petroleum distillate fractions and possibly differentiating particles from vapour in oil mist measurements of light mineral oil-based metalworking fluids. Diffusive uptake rates were measured on Perkin Elmer thermal desorption tube samplers packed with Tenax TA, and the potential for deposition within the tubes was examined. Hydrocarbon vapour was found to adsorb on the oxide layer that can develop on the sampler's internal walls. General measurements of mixed hydrocarbon vapours (i.e. petroleum distillate fractions) should not be unduly affected if concentrations are greater than ~5 mg m^–3 and the tubes are in good condition. For the purposes of differentiating light mineral oil mist and vapour from a total hydrocarbon measurement, it is unlikely that measuring the vapour separately could be used to calculate mist concentrations <3 mg m^–3 with sufficient accuracy.

Hazardous Off-Gassing of Carbon Monoxide and Oxygen Depletion during Ocean Transportation of Wood Pellets

Svedberg, U., Samuelsson, J., Melin, S. — 2008-06-05

Five ocean vessels were investigated for the characterization and quantification of gaseous compounds emitted during ocean transportation of wood pellets in closed cargo hatches from Canada to Sweden. The study was initiated after a fatal accident with several injured during discharge in Sweden. The objective with the investigation was to better understand the off-gassing and issues related to workers' exposure. Air sampling was done during transport and immediately before discharge in the undisturbed headspace air above the wood pellets and in the staircase adjacent to each hatch. The samples were analyzed with Fourier transform infrared spectroscopy and direct reading instruments. The following compounds and ranges were detected in samples from the five ships: carbon monoxide (CO) 1460–14650 ppm, carbon dioxide (CO₂) 2960–21570 ppm, methane 79.9–956 ppm, butane equivalents 63–842 ppm, ethylene 2–21.2 ppm, propylene 5.3–36 ppm, ethane 0–25 ppm and aldehydes 2.3–35 ppm. The oxygen levels were between 0.8 and 16.9%. The concentrations in the staircases were almost as high as in the cargo hatches, indicating a fairly free passage of air between the two spaces. A potentially dangerous atmosphere was reached within a week from loading. The conclusions are that ocean transportation of wood pellets in confined spaces may produce an oxygen deficient atmosphere and lethal levels of CO which may leak into adjacent access spaces. The dangerous combination of extremely high levels of CO and reduced oxygen produces a fast-acting toxic combination. Measurement of CO in combination with oxygen is essential prior to entry in spaces having air communication with cargo hatches of wood pellets. Forced ventilation of staircases prior to entry is necessary. Redesign, locking and labeling of access doors and the establishment of rigorous entry procedures and training of onboard crew as well as personnel boarding ocean vessels are also important.

Airborne Concentrations of Asbestos Onboard Maritime Shipping Vessels (1978-1992)

2008-06-05

The exposure of shipyard workers to asbestos has been frequently investigated during the installation, repair or removal of asbestos insulation. The same level of attention, however, has not been directed to asbestos exposure of maritime seamen or sailors. In this paper, we assemble and analyze historical industrial hygiene (IH) data quantifying airborne asbestos concentrations onboard maritime shipping vessels between 1978 and 1992. Air monitoring and bulk sampling data were compiled from 52 IH surveys conducted on 84 different vessels, including oil tankers and cargo vessels, that were docked and/or at sea, but these were not collected during times when there was interaction with asbestos-containing materials (ACMs). One thousand and eighteen area air samples, 20 personal air samples and 24 air samples of unknown origin were analyzed by phase contrast microscopy (PCM); 19 area samples and six samples of unknown origin were analyzed by transmission electron microscopy (TEM) and 13 area air samples were analyzed by scanning electron microscopy (SEM). In addition, 482 bulk samples were collected from suspected ACMs, including insulation, ceiling panels, floor tiles, valve packing and gaskets. Fifty-three percent of all PCM and 4% of all TEM samples were above their respective detection limits. The average airborne concentration for the PCM area samples (n = 1018) was 0.008 fibers per cubic centimeter (f cc^–1) (95th percentile of 0.040 f cc^–1). Air concentrations in the living and recreational areas of the vessels (e.g. crew quarters, common rooms) averaged 0.004 f cc^–1 (95th percentile of 0.014 f cc^–1), while air concentrations in the engine rooms and machine shops averaged 0.010 f cc^–1 (95th percentile of 0.068 f cc^–1). Airborne asbestos concentrations were also classified by vessel type (cargo, tanker or Great Lakes), transport status (docked or underway on active voyage) and confirmed presence of ACM. Approximately 1.3 and 0% of the 1018 area samples analyzed by PCM exceeded 0.1 and 1 f cc^–1, respectively. This data set indicates that historic airborne asbestos concentrations on these maritime shipping vessels, when insulation–handling activities were not actively being performed, were consistently below contemporaneous US occupational standards from 1978 until 1992, and nearly always below the current permissible exposure limit of 0.1 f cc^–1.

Sharps Injuries in Healthcare Waste Handlers

Blenkharn, J. I., Odd, C. — 2008-06-05

Clinical waste disposal carries with it a risk of serious and possibly life-threatening infection. Combining confidential questionnaires and structured interviews with discrete observation, the attitudes and approach to safe handling of bulk clinical wastes by staff in a specialist waste treatment facility were assessed. With particular attention to glove use and hand hygiene, observations were supplemented by review of group-wide accident and incident records, with emphasis on sharps injuries and related blood and bloodstained body fluid exposures. Deficiencies in glove selection and use, and in hand hygiene, were noted despite extensive and on-going training and supervision of waste handlers. Though ballistic puncture-resistant gloves protect against sharps injury, these were uncomfortable in use and were sometimes rejected by waste handlers who preferred thin-walled nitrile gloves that were more comfortable in use though provide no resistance to penetrating injury. Among the waste handlers working for a single specialist waste disposal company, sharps injuries (n = 40) occurred at a rate of approximately 1 per 29 000 man hours. Injuries were caused by hypodermic needles from improperly closed or overfilled sharps boxes (n = 6) or from sharps incorrectly discarded into thin-walled plastic sacks intended only for soft wastes (n = 34). Most injuries occurred to the fingers or hands. No seroconversions occurred, though two individuals suffered anxiety/stress disorder necessitating prolonged leave of absence with professional counselling and support. Glove use and hand hygiene must feature prominently in the on-going training of waste handlers. Though ballistic gloves afford protection against sharps injury, the initial segregation and safe disposal of clinical wastes by healthcare professionals must provide the primary control measure. Despite robust and unambiguous legislation and good practice guidelines, serious errors by healthcare staff that result in the disposal of hypodermic needles and other sharps to thin-walled plastic waste sacks places waste handlers at risk of bloodborne virus infection. Further improvement in the standards of waste segregation and disposal by healthcare professionals are still required to protect ancillary and support staff and waste handlers working in the disposal sector.

Performance of Laboratories Analysing Welding Fume on Filter Samples: Results from the WASP Proficiency Testing Scheme

Stacey, P., Butler, O. — 2008-06-05

This paper emphasizes the need for occupational hygiene professionals to require evidence of the quality of welding fume data from analytical laboratories. The measurement of metals in welding fume using atomic spectrometric techniques is a complex analysis often requiring specialist digestion procedures. The results from a trial programme testing the proficiency of laboratories in the Workplace Analysis Scheme for Proficiency (WASP) to measure potentially harmful metals in several different types of welding fume showed that most laboratories underestimated the mass of analyte on the filters. The average recovery was 70–80% of the target value and >20% of reported recoveries for some of the more difficult welding fume matrices were <50%. This level of under-reporting has significant implications for any health or hygiene studies of the exposure of welders to toxic metals for the types of fumes included in this study. Good laboratories' performance measuring spiked WASP filter samples containing soluble metal salts did not guarantee good performance when measuring the more complex welding fume trial filter samples. Consistent rather than erratic error predominated, suggesting that the main analytical factor contributing to the differences between the target values and results was the effectiveness of the sample preparation procedures used by participating laboratories. It is concluded that, with practice and regular participation in WASP, performance can improve over time.

Annals of Occupational Hygiene Performance Indicators, 2007

Ogden, T. — 2008-04-11

Captan Exposure and Evaluation of a Pesticide Exposure Algorithm among Orchard Pesticide Applicators in the Agricultural Health Study

2008-04-11

Pesticide exposure assessment in the Agricultural Health Study (AHS) has relied upon two exposure metrics: lifetime exposure days and intensity-weighted lifetime exposure days, the latter incorporating an intensity score computed from a questionnaire-based algorithm. We evaluated this algorithm using actual fungicide exposure measurements from AHS private orchard applicators. Captan was selected as a marker of fungicide exposure. Seventy-four applicators from North Carolina and Iowa growing apples and/or peaches were sampled on 2 days they applied captan in 2002 and 2003. Personal air, hand rinse, 10 dermal patches, a pre-application first-morning urine and a subsequent 24-h urine sample were collected from each applicator per day. Environmental samples were analyzed for captan, and urine samples were analyzed for cis-1,2,3,6-tetrahydrophthalimide (THPI). Task and personal protective equipment information needed to compute an individual's algorithm score was also collected. Differences in analyte detection frequency were tested in a repeated logistic regression model. Mixed-effects models using maximum-likelihood estimation were employed to estimate geometric mean exposures and to evaluate the measured exposure data against the algorithm. In general, captan and THPI were detected significantly more frequently in environmental and urine samples collected from applicators who used air blast sprayers as compared to those who hand sprayed. The AHS pesticide exposure intensity algorithm, while significantly or marginally predictive of thigh and forearm captan exposure, respectively, did not predict air, hand rinse or urinary THPI exposures. The algorithm's lack of fit with some exposure measures among orchard fungicide applicators may be due in part to the assignment of equal exposure weights to air blast and hand spray application methods in the current algorithm. Some modification of the algorithm is suggested by these results.

Sampling of High Amounts of Bioaerosols Using a High-Volume Electrostatic Field Sampler

Madsen, A. M., Sharma, A. K. — 2008-04-11

For studies of the biological effects of bioaerosols, large samples are necessary. To be able to sample enough material and to cover the variations in aerosol content during and between working days, a long sampling time is necessary. Recently, a high-volume transportable electrostatic field sampler for collection of fine particles has been described. The aim of this study was to investigate whether this sampler can be used for collection of high amounts of authentic bioaerosols that can subsequently be used for biological analysis. The investigation was carried out at a biofuel plant in a straw storage room and in a boiler room over two seasons. The sampled dust was quantified in terms of mass and characterized regarding microbial components and compared with dust sampled by Gravikon and GSP samplers. For the electrostatic field sampler, a prefilter was used to remove large objects. The prefilter was characterized for particle penetration and this testing indicated that the prefilter did not remove particles up to 10 µm, and therefore respirable dust was sampled by the electrostatic field sampler. Using the electrostatic field sampler in the straw storage and in the boiler room, 330 and 315 mg dust (net recovery of the lyophilized dust) was sampled during a period of 7 days, respectively. The sampling rates of the electrostatic field samplers were between 1.34 and 1.96 mg dust per hour, the value for the Gravikon was between 0.083 and 0.108 mg dust per hour and the values for the GSP samplers were between 0.0031 and 0.032 mg dust per hour. The standard deviations of replica samplings and the following microbial analysis using the electrostatic field sampler and GSP samplers were at the same levels. The exposure to dust in the straw storage was 7.7 mg m^–3 when measured by the electrostatic field sampler and 11.8 mg m^–3 when measured by the GSP inhalable dust sampler. The quantity (amount per mg dust) of total fungi, Aspergillus fumigatus, total bacteria, endotoxin and mesophilic actinomycetes sampled by the electrostatic field samplers and the Gravikon samplers varied within the same season by a factor smaller than four. The quantities of some microbial components were higher in the dust collected with all samplers in March than in August. In conclusion, by using the electrostatic field sampler, it was possible to sample replicas of large authentic aerosol samples that can be used, e.g. biological analysis. (Sharma AK et al., 2007a).

Respiratory Performance Offered by N95 Respirators and Surgical Masks: Human Subject Evaluation with NaCl Aerosol Representing Bacterial and Viral Particle Size Range

Lee, S.-A., Grinshpun, S. A., Reponen, T. — 2008-04-11

Objectives: This study aimed at determining the protection factors (PFs) provided by N95 filtering facepiece respirators and surgical masks against particles representing bacterial and viral size ranges (aerodynamic size: 0.04–1.3 µm).

Methods: The protection levels of N95 filtering facepiece respirators (four models) and surgical masks (three models) were investigated while they were donned by 12 subjects performing the OSHA (US Occupational Safety and Health Administration) fit-testing exercises in a test chamber.

Results: About 29% of N95 respirators and ~100% of surgical masks had PFs <10, which is the assigned PF designated for this type of respirator by the OSHA. On average, the PFs of N95 respirators were 8–12 times greater than those of surgical masks. The minimum PFs were observed in the size range of 0.04–0.2 µm. No significant difference in PF results was found between N95 respirators with and without an exhalation valve.

Conclusions: The study indicates that N95 filtering facepiece respirators may not achieve the expected protection level against bacteria and viruses. An exhalation valve on the N95 respirator does not affect the respiratory protection; it appears to be an appropriate alternative to reduce the breathing resistance.

Usage of Air Monitoring and Biomarkers of Isocyanate Exposure to Assess the Effect of a Control Intervention

Tinnerberg, H., Mattsson, C. — 2008-04-11

Exposure to isocyanates is known to have respiratory effects in workers and therefore it is essential to monitor the occupational exposure. An earlier study of a continuous foaming plant using toluene diisocyanate (TDI) showed that the exposure to isocyanates can be high. Since then several preventive actions were implemented at the plant. The aim of this study was to observe the effect of these actions measured by air and biological monitoring. Four workers were monitored in the year 2000 and six in 2005, with air measurements during the continuous foaming process, and with measurements of biomarkers in one plasma sample each year and with two urinary samples being collected in the year 2000 and one in 2005. The median TDI air concentrations in 2005 were ~20% of the 2000 levels and the median levels of biomarkers in 2005 were ~10% of the 2000 levels. According to our measurements the preventive action had a real effect to decrease the exposure to TDI. As the workers both before and after the preventive actions used personal protective equipment, the use of biomarkers was necessary to assess the real gain in the preventive actions.

Health Survey of Workers Exposed to Mixed Solvent and Ergonomic Hazards in Footwear and Equipment Factory Workers in Thailand

Todd, L., Puangthongthub, S. T., Mottus, K., Mihlan, G., Wing, S. — 2008-04-11

A cross-sectional health study was performed at four footwear and one equipment factory in Thailand to evaluate the prevalence of chemical- and ergonomic-related symptoms in Thai factory workers and to investigate associations between these symptoms and exposures to organic solvents, isocyanates and ergonomic risks. A 10-page health questionnaire was administered to 1784 workers across the four footwear and equipment factories. A total of 1675 questionnaires were returned, yielding a 94% response rate. The questionnaires asked about age, gender, use of chemicals, use of personal protective equipment and health outcomes. Without exception, the percentages of workers reporting symptoms after being hired were higher than those reporting symptoms before being hired for all the factories. The highest symptom percentages were related to ergonomic stressors. Multiple logistic regression was used to calculate adjusted prevalence odds ratios and 95% confidence intervals. This study showed that adverse health effects experienced by footwear and equipment factory workers are associated with occupational exposures to chemicals (volatile organic solvents and water-based adhesives) and ergonomic hazards.

Filter Quality of Pleated Filter Cartridges

Chen, C.-W., Huang, S.-H., Chiang, C.-M., Hsiao, T.-C., Chen, C.-C. — 2008-04-11

The performance of dust cartridge filters commonly used in dust masks and in room ventilation depends both on the collection efficiency of the filter material and the pressure drop across the filter. Currently, the optimization of filter design is based only on minimizing the pressure drop at a set velocity chosen by the manufacturer. The collection efficiency, an equally important factor, is rarely considered in the optimization process. In this work, a filter quality factor, which combines the collection efficiency and the pressure drop, is used as the optimization criterion for filter evaluation. Most respirator manufacturers pleat the filter to various extents to increase the filtration area in the limit space within the dust cartridge. Six sizes of filter holders were fabricated to hold just one pleat of filter, simulating six different pleat counts, ranging from 0.5 to 3.33 pleats cm^–1. The possible electrostatic charges on the filter were removed by dipping in isopropyl alcohol, and the air velocity is fixed at 100 cm s^–1. Liquid dicotylphthalate particles generated by a constant output atomizer were used as challenge aerosols to minimize particle loading effects. A scanning mobility particle sizer was used to measure the challenge aerosol number concentrations and size distributions upstream and downstream of the pleated filter. The pressure drop across the filter was monitored by using a calibrated pressure transducer. The results showed that the performance of pleated filters depend not only on the size of the particle but also on the pleat count of the pleated filter. Based on filter quality factor, the optimal pleat count (OPC) is always higher than that based on pressure drop by about 0.3–0.5 pleats cm^–1. For example, the OPC is 2.15 pleats cm^–1 from the standpoint of pressure drop, but for the highest filter quality factor, the pleated filter needed to have a pleat count of 2.65 pleats cm^–1 at particle diameter of 122 nm. From the aspect of filter quality factor, this study suggests that the respirator manufacturers should add ~0.5 pleats cm^–1 to the OPC derived from the generalized correlation curve for pleated filter design based on minimum pressure drop.