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1.  Exposure Assessment at 30 000 Feet: Challenges and Future Directions 
Few studies of cancer mortality and incidence among flight crew have included a detailed assessment of both occupational exposures and lifestyle factors that may influence the risk of cancer. In this issue, Kojo et al. (Risk factors for skin cancer among Finnish airline cabin crew. Ann. Occup. Hyg 2013; 57: 695–704) evaluated the relative contributions of ultraviolet and cosmic radiation to the incidence of skin cancer in Finnish flight attendants. This is a useful contribution, yet the reason flight crew members have an increased risk of skin cancer compared with the general population remains unclear. Good policy decisions for flight crew will depend on continued and emerging effective collaborations to increase study power and improve exposure assessment in future flight crew health studies. Improving the assessment of occupational exposures and non-occupational factors will cost additional time and effort, which are well spent if the role of exposures can be clarified in larger studies.
PMCID: PMC4509733  PMID: 23818455
cosmic radiation; exposure assessment; flight crew; skin cancer; ultraviolet radiation
2.  Analysis of Silica in Bulk Materials Response 
Annals of Occupational Hygiene  2014;58(5):658-659.
PMCID: PMC4305119  PMID: 24848630
3.  Analysis of Crystalline Silica in Bulk Materials 
Annals of Occupational Hygiene  2014;58(5):657-659.
PMCID: PMC4305118  PMID: 24681562
4.  Workplace measurements by the U.S. Occupational Safety and Health Administration since 1979: Descriptive analysis and potential uses for exposure assessment 
Annals of Occupational Hygiene  2013;57(5):681-683.
This letter summarizes modifications to the results presented in Lavoué et al. (2012): Lavoué, J., Burstyn, I., Friesen, M. (2012) Workplace Measurements by the US Occupational Safety and Health Administration since 1979: Descriptive Analysis and Potential Uses for Exposure Assessment. Annals of occupational hygiene 57(1):77–97. Although several results were altered, the conclusions were not affected by the changes.
PMCID: PMC3900859  PMID: 23946941
5.  Photothermal Desorption of Single-Walled Carbon Nanotubes and Coconut Shell-Activated Carbons Using a Continuous Light Source for Application in Air Sampling 
Annals of Occupational Hygiene  2014;58(7):877-888.
Many techniques exist to measure airborne volatile organic compounds (VOCs), each with differing advantages; sorbent sampling is compact, versatile, has good sample stability, and is the preferred technique for collecting VOCs for hygienists. Development of a desorption technique that allows multiple analyses per sample (similar to chemical desorption) with enhanced sensitivity (similar to thermal desorption) would be helpful to field hygienists. In this study, activated carbon (AC) and single-walled carbon nanotubes (SWNT) were preloaded with toluene vapor and partially desorbed with light using a common 12-V DC, 50-W incandescent/halogen lamp. A series of experimental chamber configurations were explored starting with a 500-ml chamber under static conditions, then with low ventilation and high ventilation, finally a 75-ml high ventilation chamber was evaluated. When preloaded with toluene and irradiated at the highest lamp setting for 4min, AC desorbed 13.9, 18.5, 23.8, and 45.9% of the loaded VOC mass, in each chamber configuration, respectively; SWNT desorbed 25.2, 24.3, 37.4, and 70.5% of the loaded VOC mass, respectively. SWNT desorption was significantly greater than AC in all test conditions (P = 0.02–<0.0001) demonstrating a substantial difference in sorbent performance. When loaded with 0.435mg toluene and desorbed at the highest lamp setting for 4min in the final chamber design, the mean desorption for AC was 45.8% (39.7, 52.0) and SWNT was 72.6% (68.8, 76.4) (mean represented in terms of 95% confidence interval). All desorption measurements were obtained using a field grade photoionization detector; this demonstrates the potential of using this technique to perform infield prescreening of VOC samples for immediate exposure feedback and in the analytical lab to introduce sample to a gas chromatograph for detailed analysis of the sample.
PMCID: PMC4184402  PMID: 25016598
air sampling; bucky paper; exposure assessment; industrial hygiene; photothermal desorption; single-walled carbon nanotubes; toluene; VOC
6.  Aerosols and Criteria Gases in an Underground Mine That Uses FAME Biodiesel Blends 
The contribution of heavy-duty haulage trucks to the concentrations of aerosols and criteria gases in underground mine air and the physical properties of those aerosols were assessed for three fuel blends made with fatty acid methyl esters biodiesel and petroleum-based ultra-low-sulfur diesel (ULSD). The contributions of blends with 20, 50, and 57% of biodiesel as well as neat ULSD were assessed using a 30-ton truck operated over a simulated production cycle in an isolated zone of an operating underground metal mine. When fueled with the B20 (blend of biodiesel with ULSD with 20% of biodiesel content), B50 (blend of biodiesel with ULSD with 50% of biodiesel content), and B57 (blend of biodiesel with ULSD with 57% of biodiesel content) blends in place of ULSD, the truck’s contribution to mass concentrations of elemental and total carbon was reduced by 20, 50, and 61%, respectively. Size distribution measurements showed that the aerosols produced by the engine fueled with these blends were characterized by smaller median electrical mobility diameter and lower peak concentrations than the aerosols produced by the same engine fueled with ULSD. The use of the blends resulted in number concentrations of aerosols that were 13–29% lower than those when ULSD was used. Depending on the content of biodiesel in the blends, the average reductions in the surface area concentrations of aerosol which could be deposited in the alveolar region of the lung (as measured by a nanoparticle surface area monitor) ranged between 6 and 37%. The use of blends also resulted in slight but measurable reductions in CO emissions, as well as an increase in NOX emissions. All of the above changes in concentrations and physical properties were found to be correlated with the proportion of biodiesel in the blends.
PMCID: PMC4505372  PMID: 25060241
alternative fuels; diesel aerosols; FAME biodiesel; nitrogen oxides; number concentrations; size distributions; underground mining
7.  Effects of Breathing Frequency and Flow Rate on the Total Inward Leakage of an Elastomeric Half-Mask Donned on an Advanced Manikin Headform 
The objective of this study was to investigate the effects of breathing frequency and flow rate on the total inward leakage (TIL) of an elastomeric half-mask donned on an advanced manikin headform and challenged with combustion aerosols.
An elastomeric half-mask respirator equipped with P100 filters was donned on an advanced manikin headform covered with life-like soft skin and challenged with aerosols originated by burning three materials: wood, paper, and plastic (polyethylene). TIL was determined as the ratio of aerosol concentrations inside (Cin) and outside (Cout) of the respirator (Cin/Cout) measured with a nanoparticle spectrometer operating in the particle size range of 20–200 nm. The testing was performed under three cyclic breathing flows [mean inspiratory flow (MIF) of 30, 55, and 85 l/min] and five breathing frequencies (10, 15, 20, 25, and 30 breaths/min). A completely randomized factorial study design was chosen with four replicates for each combination of breathing flow rate and frequency.
Particle size, MIF, and combustion material had significant (P < 0.001) effects on TIL regardless of breathing frequency. Increasing breathing flow decreased TIL. Testing with plastic aerosol produced higher mean TIL values than wood and paper aerosols. The effect of the breathing frequency was complex. When analyzed using all combustion aerosols and MIFs (pooled data), breathing frequency did not significantly (P = 0.08) affect TIL. However, once the data were stratified according to combustion aerosol and MIF, the effect of breathing frequency became significant (P < 0.05) for all MIFs challenged with wood and paper combustion aerosols, and for MIF = 30 l/min only when challenged with plastic combustion aerosol.
The effect of breathing frequency on TIL is less significant than the effects of combustion aerosol and breathing flow rate for the tested elastomeric half-mask respirator. The greatest TIL occurred when challenged with plastic aerosol at 30 l/min and at a breathing frequency of 30 breaths/min.
PMCID: PMC4479205  PMID: 24106004
breathing frequency; combustion aerosol; flow rate; half-mask; manikin; total inward leakage
8.  Systematically Extracting Metal- and Solvent-Related Occupational Information from Free-Text Responses to Lifetime Occupational History Questionnaires 
Annals of Occupational Hygiene  2014;58(5):612-624.
Lifetime occupational history (OH) questionnaires often use open-ended questions to capture detailed information about study participants’ jobs. Exposure assessors use this information, along with responses to job- and industry-specific questionnaires, to assign exposure estimates on a job-by-job basis. An alternative approach is to use information from the OH responses and the job- and industry-specific questionnaires to develop programmable decision rules for assigning exposures. As a first step in this process, we developed a systematic approach to extract the free-text OH responses and convert them into standardized variables that represented exposure scenarios.
Our study population comprised 2408 subjects, reporting 11991 jobs, from a case–control study of renal cell carcinoma. Each subject completed a lifetime OH questionnaire that included verbatim responses, for each job, to open-ended questions including job title, main tasks and activities (task), tools and equipment used (tools), and chemicals and materials handled (chemicals). Based on a review of the literature, we identified exposure scenarios (occupations, industries, tasks/tools/chemicals) expected to involve possible exposure to chlorinated solvents, trichloroethylene (TCE) in particular, lead, and cadmium. We then used a SAS macro to review the information reported by study participants to identify jobs associated with each exposure scenario; this was done using previously coded standardized occupation and industry classification codes, and a priori lists of associated key words and phrases related to possibly exposed tasks, tools, and chemicals. Exposure variables representing the occupation, industry, and task/tool/chemicals exposure scenarios were added to the work history records of the study respondents. Our identification of possibly TCE-exposed scenarios in the OH responses was compared to an expert’s independently assigned probability ratings to evaluate whether we missed identifying possibly exposed jobs.
Our process added exposure variables for 52 occupation groups, 43 industry groups, and 46 task/tool/chemical scenarios to the data set of OH responses. Across all four agents, we identified possibly exposed task/tool/chemical exposure scenarios in 44–51% of the jobs in possibly exposed occupations. Possibly exposed task/tool/chemical exposure scenarios were found in a nontrivial 9–14% of the jobs not in possibly exposed occupations, suggesting that our process identified important information that would not be captured using occupation alone. Our extraction process was sensitive: for jobs where our extraction of OH responses identified no exposure scenarios and for which the sole source of information was the OH responses, only 0.1% were assessed as possibly exposed to TCE by the expert.
Our systematic extraction of OH information found useful information in the task/chemicals/tools responses that was relatively easy to extract and that was not available from the occupational or industry information. The extracted variables can be used as inputs in the development of decision rules, especially for jobs where no additional information, such as job- and industry-specific questionnaires, is available.
PMCID: PMC4053931  PMID: 24590110
cadmium; chlorinated solvents; exposure assessment methodology; lead
9.  Relevance of Urinary 3-Hydroxybenzo(a)pyrene and 1-Hydroxypyrene to Assess Exposure to Carcinogenic Polycyclic Aromatic Hydrocarbon Mixtures in Metallurgy Workers 
Annals of Occupational Hygiene  2014;58(5):579-590.
In metallurgy, workers are exposed to mixtures of polycyclic aromatic hydrocarbons (PAHs) in which some compounds are carcinogenic. Biomonitoring of PAH exposure has been performed by measuring urinary 1-hydroxypyrene (1-OHP), a metabolite of pyrene which is not carcinogenic. This study investigated the use of 3-hydroxybenzo(a)pyrene (3-OHBaP), a metabolite of benzo(a)pyrene (BaP) which is the main carcinogenic component in PAHs, to improve carcinogen exposure assessment.
We included 129 metallurgy workers routinely exposed to PAHs during working hours. Urinary samples were collected at three sampling times at the beginning and at the end of the working week for 1-OHP and 3-OHBaP analyses.
Workers in anode production showed greater exposure to both biomarkers than those in cathode or silicon production, with respectively, 71, 40, and 30% of 3-OHBaP concentrations exceeding the value of 0.4 nmol mol−1 creatinine. No difference was observed between the 3-OHBaP levels found at the end of the penultimate workday shift and those at the beginning of the last workday shift. Within these plants, the 1-OHP/3-OHBaP ratios varied greatly according to the workers’ activity and emission sources. Using linear regression between these two metabolites, the 1-OHP level corresponding to the guidance value for 3-OHBaP ranged from 0.7 to 2.4 µmol mol−1 creatinine, depending on the industrial sector.
This study emphasizes the interest of monitoring urinary 3-OHBaP at the end of the last workday shift when working week exposure is relatively steady, and the irrelevance of a single guideline value for 1-OHP when assessing occupational health risk.
PMCID: PMC4305110  PMID: 24504174
1-hydroxypyrene (CAS n°:5315-79-7); 3-hydroxybenzo(a)pyrene (CAS n°: 13345-21-6); biological monitoring; metallurgy; occupational exposure; polycyclic aromatic hydrocarbons (PAHs)
10.  Measurement of Mass-Based Carbon Nanotube Penetration through Filtering Facepiece Respirator Filtering Media 
Annals of Occupational Hygiene  2014;58(5):646-656.
Recent studies suggest that a wide range of human health effects could result from exposure to carbon nanotubes (CNTs). A National Institute for Occupational Safety and Health survey of the carbonaceous nanomaterial industry found that 77% of the companies used respiratory protection, such as filtering facepiece respirators (FFRs). Despite CNT studies in some occupational settings being reported, the literature for mass-based penetration of CNTs through FFRs is lacking. The aim of this study was to conduct a quantitative study of single-walled CNT (SWCNT) and multiwalled CNT (MWCNT) penetration through FFRs. A CNT aerosol respirator testing system was used to generate charge-neutralized airborne SWCNTs and MWCNTs for this study. The size distribution was 20–10000nm, with 99% of the particles between 25 and 2840nm. Mass median diameters were 598 and 634nm with geometric standard deviations of 1.34 and 1.48 for SWCNTs and MWCNTs, respectively. Upstream and downstream CNTs were collected simultaneously using closed-face 3.7-cm-diameter filter cassettes. These samples were subsequently analyzed for organic carbon and elemental carbon (EC), with EC as a measure of mass-based CNTs. The mass-based penetration of SWCNTs and MWCNTs through six FFR models at constant flow rates of 30 l min−1 (LPM) was determined. Generally, the penetrations of SWCNTs and MWCNTs at 30 LPM had a similar trend and were highest for the N95 FFRs, followed by N99 and P100 FFRs. The mass-based penetration of MWCNTs through six FFR models at two constant flow rates of 30 and 85 LPM was also determined. The penetration of MWCNTs at 85 LPM was greater compared with the values of MWCNTs at 30 LPM.
PMCID: PMC4305111  PMID: 24802251
aerosol respirator testing system; elemental carbon; filtering facepiece respirators; mass-based penetration; multiwalled carbon nanotubes; single-walled carbon nanotubes
11.  The Revised Electromagnetic Fields Directive and Worker Exposure in Environments With High Magnetic Flux Densities 
Annals of Occupational Hygiene  2014;58(5):529-541.
Some of the strongest electromagnetic fields (EMF) are found in the workplace. A European Directive sets limits to workers’ exposure to EMF. This review summarizes its origin and contents and compares magnetic field exposure levels in high-risk workplaces with the limits set in the revised Directive. Pubmed, Scopus, grey literature databases, and websites of organizations involved in occupational exposure measurements were searched. The focus was on EMF with frequencies up to 10 MHz, which can cause stimulation of the nervous system. Selected studies had to provide individual maximum exposure levels at the workplace, either in terms of the external magnetic field strength or flux density or as induced electric field strength or current density. Indicative action levels and the corresponding exposure limit values for magnetic fields in the revised European Directive will be higher than those in the previous version. Nevertheless, magnetic flux densities in excess of the action levels for peripheral nerve stimulation are reported for workers involved in welding, induction heating, transcranial magnetic stimulation, and magnetic resonance imaging (MRI). The corresponding health effects exposure limit values for the electric fields in the worker’s body can be exceeded for welding and MRI, but calculations for induction heating and transcranial magnetic stimulation are lacking. Since the revised European Directive conditionally exempts MRI-related activities from the exposure limits, measures to reduce exposure may be necessary for welding, induction heating, and transcranial nerve stimulation. Since such measures can be complicated, there is a clear need for exposure databases for different workplace scenarios with significant EMF exposure and guidance on good practices.
PMCID: PMC4305112  PMID: 24557933
electromagnetic fields; legislation; occupational exposure; peripheral nervous system
12.  Personal Exposure to Inhalable Dust and the Specific Latex Aero-Allergen, Hev b6.02, in Latex Glove Manufacturing in Thailand 
Annals of Occupational Hygiene  2014;58(5):542-550.
Latex product manufacturing is an important industry in south-east Asia but has the potential for considerable occupational exposure of workers to latex allergens. Although exposure to latex allergens can result in adverse health reactions, few studies to characterize this exposure have been conducted to date. This study therefore aimed to characterize current airborne inhalable dust and the specific allergen, Hev b 6.02, exposures in this industry in Thailand.
Workers were recruited from three factories in the southern part of Thailand. Full-shift inhalable dust personal air sampling was conducted using IOM sampling heads equipped with polytetrafluoroethylene filters at a 2.0 l min−1 flowrate. After weighing to determine inhalable dust levels, filters were extracted and analysed for Hev b 6.02 using an enzyme immunometric assay.
Two hundred and seventy-five workers agreed to participate, resulting in a total of 292 measurements. Geometric mean (GM) personal exposure to inhalable dust was 0.88mg m–3, but individual exposures up to 12.34mg m–3 were measured. The pattern of exposure was similar across factories, with highest exposures in the stripping (GM 2.08–4.05mg m–3 for the 3 factories) and tumbling departments (1.11–2.17mg m–3). Within-worker (day-to-day) variability contributed 92% to total variability. The Hev b 6.02 exposure pattern was similar with time-weighted average GM exposure levels in the oldest factory ranging from 8.7mg m–3 in the laboratory to 30.2mg m–3 in the stripping department. In contrast to inhalable dust exposure, total exposure variability was primary driven by variability between workers (67%).
Workers in these latex product factories get routinely exposed to measurable Hev b 6.02 levels, which may give rise to increased incidence of allergic symptoms and occupational asthma. Also, in this measurement campaign a 10mg m–3, but not 15mg m–3, occupational exposure limit for inhalable dust was occasionally exceeded. Highest Hev b 6.02 exposures were found in the stripping and tumbling departments, which would be natural targets for interventions aimed at reducing exposure.
PMCID: PMC4305113  PMID: 24569810
allergens; allergy; glove manufacturing; hev b 6.02; inhalable dust; latex allergens; latex gloves; latex products; occupational asthma; occupational exposure; occupational hygiene
13.  Validation and Comparison of Two Sampling Methods to Assess Dermal Exposure to Drilling Fluids and Crude Oil 
Annals of Occupational Hygiene  2014;58(5):591-600.
Dermal exposure to drilling fluids and crude oil is an exposure route of concern. However, there have been no published studies describing sampling methods or reporting dermal exposure measurements. We describe a study that aimed to evaluate a wipe sampling method to assess dermal exposure to an oil-based drilling fluid and crude oil, as well as to investigate the feasibility of using an interception cotton glove sampler for exposure on the hands/wrists. A direct comparison of the wipe and interception methods was also completed using pigs’ trotters as a surrogate for human skin and a direct surface contact exposure scenario. Overall, acceptable recovery and sampling efficiencies were reported for both methods, and both methods had satisfactory storage stability at 1 and 7 days, although there appeared to be some loss over 14 days. The methods’ comparison study revealed significantly higher removal of both fluids from the metal surface with the glove samples compared with the wipe samples (on average 2.5 times higher). Both evaluated sampling methods were found to be suitable for assessing dermal exposure to oil-based drilling fluids and crude oil; however, the comparison study clearly illustrates that glove samplers may overestimate the amount of fluid transferred to the skin. Further comparison of the two dermal sampling methods using additional exposure situations such as immersion or deposition, as well as a field evaluation, is warranted to confirm their appropriateness and suitability in the working environment.
PMCID: PMC4305114  PMID: 24598941
contact scenario; crude oil; dermal exposure; drilling fluids; offshore; sampling methods
14.  Occupational Exposure Assessment of Airborne Chemical Contaminants Among Professional Ski Waxers 
Annals of Occupational Hygiene  2014;58(5):601-611.
Ski waxes are applied onto the skis to improve the performance. They contain different chemical substances, e.g. perfluoro-n-alkanes. Due to evaporation and sublimation processes as well as mechanically generated dust, vapours, fumes, and particulates can contaminate the workroom atmosphere. The number of professional ski waxers is increasing, but occupational exposure assessments among professional ski waxers are lacking.
The aim was to assess exposure to airborne chemical contaminants among professional ski waxers. It was also a goal to construct a ventilation system designed for ski waxing work operations.
Forty-five professional ski waxers were included. Personal measurements of the inhalable and the respirable aerosol mass fractions were executed in 36 different waxing cabins using Conical Inhalable Sampler cassettes equipped with 37-mm PVC filters (5 µm) and Casella respirable cyclones equipped with 37-mm PVC filters (0.8 µm), respectively. Volatile organic components were collected using Anasorb CSC charcoal tubes. To examine time trends in exposure patterns, stationary real-time measurements of the aerosol mass fractions were conducted using a direct-reading Respicon® sampler.
Mean aerosol particle mass concentrations of 3.1 mg·m−3 (range: 0.2–12.0) and 6.2 mg·m−3 (range: 0.4–26.2) were measured in the respirable and inhalable aerosol mass fractions, respectively. Real-time aerosol sampling showed large variations in particle concentrations, with peak exposures of ~10 and 30 mg·m−3 in the respirable and the inhalable aerosol particle mass fractions, respectively. The custom-made ventilation system reduced the concentration of all aerosol mass fractions by more than 90%.
PMCID: PMC4305115  PMID: 24607772
occupational exposure; perfluoro-n-alkanes; ski wax; ski waxer; ventilation suction cap
15.  Chemical Markers of Occupational Exposure to Teak Wood Dust 
Annals of Occupational Hygiene  2014;58(5):566-578.
A novel high-performance liquid chromatographic/ultraviolet method was developed to detect lapachol (LP) and deoxylapachol (DLP) in wood dust as chemical markers of teak wood (a suspected human carcinogen). The specificity of this analysis was determined by noting the absence of LP and DLP in 12 other specimens of different woods belonging to the angiosperm family. The consistency was examined by analyzing teak from three different sources, where the percentages (wt/wt) of the chemicals ranged from 0.006 to 0.261 for LP and from 0.038 to 0.497 for DLP, respectively. Although the LP and DLP components of teak varied according to source, a very high correlation coefficient (r 2 > 0.98 always) was found between the content of the two markers in the bulk specimens and in bulk dust derived from them. The method was then applied to teak dust collected on polyvinylchloride filters from aerosol in an exposure chamber in the range of mass loadings between 0.03 and 3.65mg, which corresponds to a dust exposure between 0.124 and 8.703mg m−3 for a sampling time of 2h. A field test was also carried out in a small factory where teak was used. A good correlation was confirmed between LP and DLP versus the dust collected on the filter in both cases. LP and DLP can be markers to estimate the true quantities of teak dust inhaled in a workplace with mixed wood dust, provided the results are matched to the content of LP and DLP in the bulk wood. LP and DLP have also been proposed as the agents responsible for allergic reaction to teak dust. Therefore, it would be useful to evaluate the exposure to these two substances even without a relationship to teak dust exposure.
PMCID: PMC4305116  PMID: 24671613
deoxylapachol; lapachol; occupational exposure; teak dust; wood dust
16.  Computational Fluid Dynamics Investigation of Human Aspiration in Low Velocity Air: Orientation Effects on Nose-Breathing Simulations 
Annals of Occupational Hygiene  2014;58(5):625-645.
An understanding of how particles are inhaled into the human nose is important for developing samplers that measure biologically relevant estimates of exposure in the workplace. While previous computational mouth-breathing investigations of particle aspiration have been conducted in slow moving air, nose breathing still required exploration. Computational fluid dynamics was used to estimate nasal aspiration efficiency for an inhaling humanoid form in low velocity wind speeds (0.1–0.4 m s−1). Breathing was simplified as continuous inhalation through the nose. Fluid flow and particle trajectories were simulated over seven discrete orientations relative to the oncoming wind (0, 15, 30, 60, 90, 135, 180°). Sensitivities of the model simplification and methods were assessed, particularly the placement of the recessed nostril surface and the size of the nose. Simulations identified higher aspiration (13% on average) when compared to published experimental wind tunnel data. Significant differences in aspiration were identified between nose geometry, with the smaller nose aspirating an average of 8.6% more than the larger nose. Differences in fluid flow solution methods accounted for 2% average differences, on the order of methodological uncertainty. Similar trends to mouth-breathing simulations were observed including increasing aspiration efficiency with decreasing freestream velocity and decreasing aspiration with increasing rotation away from the oncoming wind. These models indicate nasal aspiration in slow moving air occurs only for particles <100 µm.
PMCID: PMC4305117  PMID: 24665111
dust; dust sampling convention; inhalability; inhalable dust; low velocity; model; nose
17.  Evaluation of a Diffusion Charger for Measuring Aerosols in a Workplace 
Annals of Occupational Hygiene  2014;58(4):424-436.
The model DC2000CE diffusion charger from EcoChem Analytics (League City, TX, USA) has the potential to be of considerable use to measure airborne surface area concentrations of nanoparticles in the workplace. The detection efficiency of the DC2000CE to reference instruments was determined with monodispersed spherical particles from 54 to 565.7nm. Surface area concentrations measured by a DC2000CE were then compared to measured and detection efficiency adjusted reference surface area concentrations for polydispersed aerosols (propylene torch exhaust, incense, diesel exhaust, and Arizona road dust) over a range of particle sizes that may be encountered in a workplace. The ratio of surface area concentrations measured by the DC2000CE to that measured with the reference instruments for unimodal and multimodal aerosols ranged from 0.02 to 0.52. The ratios for detection efficiency adjusted unimodal and multimodal surface area concentrations were closer to unity (0.93–1.19) for aerosols where the majority of the surface area was within the size range of particles used to create the correction. A detection efficiency that includes the entire size range of the DC2000CE is needed before a calibration correction for the DC2000CE can be created. For diesel exhaust, the DC2000CE retained a linear response compared to reference instruments up to 2500mm2 m−3, which was greater than the maximum range stated by the manufacturer (1000mm2 m−3). Physical limitations with regard to DC2000CE orientation, movement, and vibration were identified. Vibrating the DC2000CE while measuring aerosol concentrations may cause an increase of ~35mm2 m−3, whereas moving the DC2000CE may cause concentrations to be inflated by as much as 400mm2 m−3. Depending on the concentration of the aerosol of interest being measured, moving or vibrating a DC2000CE while measuring the aerosol should be avoided.
PMCID: PMC4318931  PMID: 24458322
diffusion charger; nanoparticles; surface area monitor
18.  Beryllium Concentrations at European Workplaces: Comparison of ‘Total’ and Inhalable Particulate Measurements 
Annals of Occupational Hygiene  2015;59(6):788-796.
A field study was carried out in order to derive a factor for the conversion of historic worker exposure data on airborne beryllium (Be) obtained by sampling according to the 37-mm closed faced filter cassette (CFC) ‘total’ particulate method into exposure concentration values to be expected when sampling using the ‘Gesamtstaubprobenahmesystem’ (GSP) inhalable sampling convention. Workplaces selected to represent the different copper Be work processing operations that typically occur in Germany and the EU were monitored revealing a broad spectrum of prevailing Be size distributions. In total, 39 personal samples were taken using a 37-mm CFC and a GSP worn side by side for simultaneous collection of the ‘total’ dust and the inhalable particulates, respectively. In addition, 20 static general area measurements were carried out using GSP, CFC, and Respicon samplers in parallel, the latter one providing information on the extra-thoracic fraction of the workplace aerosol. The study showed that there is a linear relationship between the concentrations measured with the CFC and those measured with the GSP sampler. The geometric mean value of the ratios of time-weighted average concentrations determined from GSP and CFC samples of all personal samples was 2.88. The individual values covered a range between 1 and 17 related to differences in size distributions of the Be-containing particulates. This was supported by the area measurements showing that the conversion factor increases with increasing values of the extra-thoracic fraction covering a range between 0 and 79%.
PMCID: PMC4497491  PMID: 25808693
aerosols; dust sampling conventions; exposure assessment methodology
20.  Respirable Silica Dust Suppression During Artificial Stone Countertop Cutting 
Annals of Occupational Hygiene  2014;59(1):122-126.
To assess the relative efficacy of three types of controls in reducing respirable silica exposure during artificial stone countertop cutting with a handheld circular saw.
A handheld worm drive circular saw equipped with a diamond segmented blade was fitted with water supply to wet the blade as is typical. The normal wetted-blade condition was compared to (i) wetted-blade plus ‘water curtain’ spray and (ii) wetted-blade plus local exhaust ventilation (LEV). Four replicate 30-min trials of 6-mm deep, 3-mm wide cuts in artificial quartz countertop stone were conducted at each condition in a 24-m3 unventilated tent. One dry cutting trial was also conducted for comparison. Respirable cyclone breathing zone samples were collected on the saw operator and analyzed gravimetrically for respirable mass and by X-ray diffraction for respirable quartz mass.
Mean quartz content of the respirable dust was 58.5%. The ranges of 30-min mass and quartz task concentrations in mg m−3 were as follows—wet blade alone: 3.54–7.51 and 1.87–4.85; wet blade + curtain: 1.81–5.97 and 0.92–3.41; and wet blade + LEV: 0.20–0.69 and <0.12–0.20. Dry cutting task concentrations were 69.6mg m−3 mass and 44.6mg m−3 quartz. There was a statistically significant difference (α = 0.05) between the wet blade + LEV and wet blade only conditions, but not between the wet blade + curtain and wet blade only conditions, for both respirable dust and respirable silica.
Sawing with a wetted blade plus LEV reduced mean respirable dust and quartz task exposures by a factor of 10 compared to the wet blade only condition. We were unable to show a statistically significant benefit of a water curtain in the ejection path, but the data suggested some respirable dust suppression.
PMCID: PMC4290629  PMID: 25326187
countertop cutting; engineering controls; respirable silica
21.  Computational Fluid Dynamics Investigation of Human Aspiration in Low-Velocity Air: Orientation Effects on Mouth-Breathing Simulations 
Annals of Occupational Hygiene  2013;57(6):740-757.
Computational fluid dynamics was used to investigate particle aspiration efficiency in low-moving air typical of occupational settings (0.1–0.4 m s−1). Fluid flow surrounding an inhaling humanoid form and particle trajectories traveling into the mouth were simulated for seven discrete orientations relative to the oncoming wind (0°, 15°, 30°, 60°, 90°, 135° and 180°). Three continuous inhalation velocities (1.81, 4.33, and 12.11 m s−1), representing the mean inhalation velocity associated with sinusoidal at-rest, moderate, and heavy breathing (7.5, 20.8, and 50.3 l min−1, respectively) were simulated. These simulations identified a decrease in aspiration efficiency below the inhalable particulate mass (IPM) criterion of 0.5 for large particles, with no aspiration of particles 100 µm and larger for at-rest breathing and no aspiration of particles 116 µm for moderate breathing, over all freestream velocities and orientations relative to the wind. For particles smaller than 100 µm, orientation-averaged aspiration efficiency exceeded the IPM criterion, with increased aspiration efficiency as freestream velocity decreased. Variability in aspiration efficiencies between velocities was low for small (<22 µm) particles, but increased with increasing particle size over the range of conditions studied. Orientation-averaged simulation estimates of aspiration efficiency agree with the linear form of the proposed linear low-velocity inhalable convention through 100 µm, based on laboratory studies using human mannequins.
PMCID: PMC3916737  PMID: 23316076
aspiration efficiency; CFD inhalability; computational fluid dynamics; continuous inhalation; inhalable particulate mass; mouth breathing; orientation averaged; particle aspiration; particle transport; ultralow velocity
22.  Simply Scan—Optical Methods for Elemental Carbon Measurement in Diesel Exhaust Particulate 
Annals of Occupational Hygiene  2014;58(7):889-898.
This article describes a performance assessment of three optical methods, a Magee Scientific OT21 Transmissometer, a Hach-Lange Microcolor II difference gloss meter, and a combination of an office scanner with Adobe Photoshop software. The optical methods measure filter staining as a proxy for elemental carbon in diesel exhaust particulate (DEP) exposure assessment and the suitability of each as a replacement for the existing Bosch meter optical method. Filters loaded with DEP were produced from air in a non-coal mine and the exhaust gases from a mobile crane. These were measured with each apparatus and then by combustion to obtain a reference elemental carbon value. The results from each apparatus were then plotted against both the Bosch number and reference elemental carbon values. The equations of the best fit lines for these plots were derived, and these gave functions for elemental carbon and Bosch number from the output of each new optical method. For each optical method, the range of DEP loadings which can be measured has been determined, and conversion equations for elemental carbon and Bosch number have been obtained. All three optical methods studied will effectively quantify blackness as a measure of elemental carbon. Of these the Magee Scientific OT21 transmissometer has the best performance. The Microcolor II and scanner/photoshop methods will in addition allow conversion to Bosch number which may be useful if historical Bosch data are available and functions for this are described. The scanner/photoshop method demonstrates a technique to obtain measurements of DEP exposure without the need to purchase specialized instrumentation.
PMCID: PMC4125000  PMID: 24939982
BC; black carbon; DEP; diesel exhaust; EC; elemental carbon; exposure assessment; non-destructive; optical method
23.  Systemic Exposure to PAHs and Benzene in Firefighters Suppressing Controlled Structure Fires 
Annals of Occupational Hygiene  2014;58(7):830-845.
Turnout gear provides protection against dermal exposure to contaminants during firefighting; however, the level of protection is unknown. We explored the dermal contribution to the systemic dose of polycyclic aromatic hydrocarbons (PAHs) and other aromatic hydrocarbons in firefighters during suppression and overhaul of controlled structure burns. The study was organized into two rounds, three controlled burns per round, and five firefighters per burn. The firefighters wore new or laundered turnout gear tested before each burn to ensure lack of PAH contamination. To ensure that any increase in systemic PAH levels after the burn was the result of dermal rather than inhalation exposure, the firefighters did not remove their self-contained breathing apparatus until overhaul was completed and they were >30 m upwind from the burn structure. Specimens were collected before and at intervals after the burn for biomarker analysis. Urine was analyzed for phenanthrene equivalents using enzyme-linked immunosorbent assay and a benzene metabolite (s-phenylmercapturic acid) using liquid chromatography/tandem mass spectrometry; both were adjusted by creatinine. Exhaled breath collected on thermal desorption tubes was analyzed for PAHs and other aromatic hydrocarbons using gas chromatography/mass spectrometry. We collected personal air samples during the burn and skin wipe samples (corn oil medium) on several body sites before and after the burn. The air and wipe samples were analyzed for PAHs using a liquid chromatography with photodiode array detection. We explored possible changes in external exposures or biomarkers over time and the relationships between these variables using non-parametric sign tests and Spearman tests, respectively. We found significantly elevated (P < 0.05) post-exposure breath concentrations of benzene compared with pre-exposure concentrations for both rounds. We also found significantly elevated post-exposure levels of PAHs on the neck compared with pre-exposure levels for round 1. We found statistically significant positive correlations between external exposures (i.e. personal air concentrations of PAHs) and biomarkers (i.e. change in urinary PAH metabolite levels in round 1 and change in breath concentrations of benzene in round 2). The results suggest that firefighters wearing full protective ensembles absorbed combustion products into their bodies. The PAHs most likely entered firefighters’ bodies through their skin, with the neck being the primary site of exposure and absorption due to the lower level of dermal protection afforded by hoods. Aromatic hydrocarbons could have been absorbed dermally during firefighting or inhaled during the doffing of gear that was off-gassing contaminants.
PMCID: PMC4124999  PMID: 24906357
aromatic hydrocarbons; benzene; biomarkers; dermal exposure; exhaled breath; firefighters; PAHs; urine
24.  Assessing Occupational Exposure to Chemicals in an International Epidemiological Study of Brain Tumours 
Annals of Occupational Hygiene  2013;57(5):610-626.
The INTEROCC project is a multi-centre case–control study investigating the risk of developing brain cancer due to occupational chemical and electromagnetic field exposures. To estimate chemical exposures, the Finnish Job Exposure Matrix (FINJEM) was modified to improve its performance in the INTEROCC study and to address some of its limitations, resulting in the development of the INTEROCC JEM. An international team of occupational hygienists developed a crosswalk between the Finnish occupational codes used in FINJEM and the International Standard Classification of Occupations 1968 (ISCO68). For ISCO68 codes linked to multiple Finnish codes, weighted means of the exposure estimates were calculated. Similarly, multiple ISCO68 codes linked to a single Finnish code with evidence of heterogeneous exposure were refined. One of the key time periods in FINJEM (1960–1984) was split into two periods (1960–1974 and 1975–1984). Benzene exposure estimates in early periods were modified upwards. The internal consistency of hydrocarbon exposures and exposures to engine exhaust fumes was improved. Finally, exposure to polycyclic aromatic hydrocarbon and benzo(a)pyrene was modified to include the contribution from second-hand smoke. The crosswalk ensured that the FINJEM exposure estimates could be applied to the INTEROCC study subjects. The modifications generally resulted in an increased prevalence of exposure to chemical agents. This increased prevalence of exposure was not restricted to the lowest categories of cumulative exposure, but was seen across all levels for some agents. Although this work has produced a JEM with important improvements compared to FINJEM, further improvements are possible with the expansion of agents and additional external data.
PMCID: PMC3888250  PMID: 23467593
cancer epidemiology; case–control; job-exposure matrix
25.  Influence of Analysis Methods on Interpretation of Hazard Maps 
Annals of Occupational Hygiene  2012;57(5):558-570.
Exposure or hazard mapping is becoming increasingly popular among industrial hygienists. Direct-reading instruments used for hazard mapping of data collection are steadily increasing in reliability and portability while decreasing in cost. Exposure measurements made with these instruments generally require no laboratory analysis although hazard mapping can be a time-consuming process. To inform decision making by industrial hygienists and management, it is crucial that the maps generated from mapping data are as accurate and representative as possible. Currently, it is unclear how many sampling locations are necessary to produce a representative hazard map. As such, researchers typically collect as many points as can be sampled in several hours and interpolation methods are used to produce higher resolution maps. We have reanalyzed hazard-mapping data sets from three industrial settings to determine which interpolation methods yield the most accurate results. The goal is to provide practicing industrial hygienists with some practical guidelines to generate accurate hazard maps with ‘off-the-shelf’ mapping software. Visually verifying the fit of the variogram model is crucial for accurate interpolation. Exponential and spherical variogram models performed better than Gaussian models. It was also necessary to diverge from some of the default interpolation parameters such as the number of bins used for the experimental variogram and whether or not to allow for a nugget effect to achieve reasonable accuracy of the interpolation for some data sets.
PMCID: PMC3916742  PMID: 23258453
exposure mapping; hazard mapping; interpolation; kriging

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