Novel Approaches in Industrial Hygiene Sampling and Analysis


Thursday, May 26, 2016, 1:00 PM - 3:40 PM


Evaluation of Sampling Bias During VOC Exposures Involving Peaks Using Capillary Flow Controllers Coupled with Evacuated Canisters

R. LeBouf, CDC/NIOSH, Morgantown, WV

Objective: NIOSH is in the process of evaluating canister methods for sampling of a wide range of VOCs. Capillary flow controllers have a well-defined drop in flow rate over the sampling period as the pressure in the canister rises closer to atmospheric pressure. Peak exposures during this period will give rise to a positive or negative bias in sampling results. This study was conducted to assess the influence of the time of occurrence of the peak on the performance of the method.

Methods: Six flow controllers coupled with 400 mL evacuated canisters were tested in a small chamber (32 L) to evaluate sampling bias with respect to grab samples using canisters. All samples were pressurized with ultra-high purity nitrogen and analyzed with a 1 mL gas sample loop and a gas chromatograph/flame ionization detector. Toluene was used as a representative chemical of indoor/industrial contaminants. A 2 ppm concentration of toluene was generated in a chamber using a Dynamic Dilution System. Peaks of 200 ppm (100x) were generated at either the beginning of the sampling period to assess positive sampling bias or at the end of the sampling period to assess negative sampling bias. A photoionization detector was used to monitor the stability of the concentration of toluene throughout the sampling period. Two sampling periods were assessed: 4 hours and 8 hours representing 25% and 50% volume filled in the canister. Three experiments were run for each sampling period with six replicate canisters per experiment. The reference concentration was established using a series of canisters drawn directly from the chamber with no flow control device (grab sampler). Comparison of the reference values to the concentrations collected by the capillary flow controllers allowed for an assessment of the capillary flow controller bias.

Results: The bias for all experiment trials ranged from 0.01% to -25% as compared to the reference concentrations. Relative standard deviations ranged from 1.0% to 16.3%. Reducing the volume filled in the canister from one-half to one-quarter decreased sampling bias from -25% to -16% for a peak at the end of the sampling period.

Conclusions: Full-shift and half-shift sampling with small, evacuated canisters were found to provide results comparable to the reference values. Sampling bias can be reduced by filling the canister to a smaller percentage of the canister volume.



Determinations of Bisphenol A and Bisphenol A Analogues by Solid-Phase Microextraction with On-Fiber Derivatizations

F. Hsu and S. Tsai, Environmental Health, Taipei, Taiwan

Objective: Bisphenol A (BPA) is widely used in consumer products, such as the lining in various types of cans. The leaching of BPA from such products can result in adverse human exposures. For example, BPA could be released into canned foods and cause possible adverse effects, especially for infants. Many countries have prohibited the use of BPA in food packaging. The common substitutes of BPA include Bisphenol S (BPS), Bisphenol F (BPF) and Bisphenol E (BPE). However, previous studies have shown that exposure to those substitutes might still cause the same or more serious health concerns. Therefore, to assess the health risk from these possible sources of exposures, there is a need to determine the concentrations of BPA and BPA analogues.

Methods: BPA and BPA analogues were extracted by using solid phase microextraction (SPME) with direct sample immersions. The analytes adsorbed on the SPME fiber were then derivatized with the derivatizing reagent: N,O-Bis(trimethylsilyl)trifluoroacetamide (BSTFA). Afterwards, the derivatives were determined by gas chromatograph and mass spectrometry (GC/MS). Canned foods and infant formula were purchased from the markets for method validations. The food samples were mixed with water before filtration and the SPME procedures.

Results: The results showed that the desorption efficiency was 100% when the desorption time was 4 min under 240 degrees Celsius. The best suitable fiber coating was 65μm Polyethylene Glycol (PEG) and the optimum condition of derivatization was 30 minutes at 50 degrees Celsius by adding 50 μL BSTFA. The working range for the analysis was between 0.01 - 10 μg/L. Different levels of BPA and BPA analogues were found in commercially available canned foods and infant formula.

Conclusions: Compared with conventional extraction methods, the SPME provides a time saving and solvent free procedures. In addition, the sensitivities of the method for BPA and BPA analogues were low enough to determine the concentrations from various types of samples.



A Review of PCB Analytical Methods for Industrial Hygiene Sampling and Recommended Practices

W. Mills, Northern Illinois University, Sycamore, IL

Situation/Problem: Indoor air exposure to polychlorinated biphenyls (PCBs) from building materials, such caulk and joint sealants, has been recognized as an issue in Europe for a number of years and more recently in the United States (US). The US Environmental Protection Agency (USEPA) and several state agencies have issued guidance on the sampling and analysis of air and solids. Many investigators are often not aware of a number of issues and limitations with the sampling and analysis of air and solids for PCBs, which are not addressed by these guidance documents.

Resolution: The available sampling and analysis methodologies for PCBs with applicability to indoor air and solids samples, with their associated uncertainties were reviewed. The analytical methods identified include high resolution gas chromatography (HRGC) with various detectors such as electron capture detection (ECD), low resolution mass spectrometry (LRMS) and high resolution mass spectrometry (HRMS). A review of worldwide guidelines for PCB air concentration guidelines and basis (i.e. Aroclor, congener, homolog) was completed. Dynamic flux chamber experiments to investigate changes in PCB patterns, due to volatilization were carried out. The data is analysed by congener and homolog and Aroclor. Predictive models were developed which matched the observed congener patterns quite closely.

Results: The USEPA, NIOSH and OSHA sampling documents for PCBs are all based on work originally carried out during the 1970’s and 1980’s. Occupational exposures to Aroclor mixtures were at much higher concentrations than current guidelines. As a result of changing exposure scenarios and analytical advances, Aroclortm analysis of indoor air samples is no longer an acceptable methodology. The use of congener or homolog specific PCB analysis is required in order to provide accurate, usable data. In addition, passive air sampling methods under development may offer less intrusive, longer term monitoring data for the same or lower costs. A predictive model for vapor phase congener patterns was developed. Using this data, the observed air sample pattern (congener or homolog) can be fit with predicted vapor phase and original Aroclortm patterns to determine if the air sample is vapor phase vs. aerosol, and predict the source profile using data analysis techniques.

Lessons learned: Sampling and analysis of PCBs in indoor air and solids, has a number of potential sources of errors and limitations, of which the investigator and unwary data user need to be aware. This presentation provides recommended practices to avoid, or at least recognize and/or minimize, these sources of error.



Sampling and Analysis of Airborne Hazardous Chemicals in Bakeries in Taiwan

P. Chang and S. Tsai, Department of Public Health & Institute of Environmental Health, College of Public Health, National Taiwan University, Taipei City, Taiwan; P. Hung, Institute of Labor, Occupational Safety and Health, Ministry of Labor, Executive Yuan, Taipei City, Taiwan

Objective: Baker’s Asthma, the most frequently reported occupational asthma makes occupational health a critical issue in bakeries. Flour dust, an airborne allergen, has been recognized as the primary risk factor. In addition, it has been reported that a wide variety of food flavorings are constantly used in the bakeries and the concentrations of hazardous airborne chemicals might be enhanced during the blending and heating processes. To assess the associated health risks for bakers in Taiwan, the airborne concentrations of flour dust, ketones and aldehydes were determined.

Methods: Silica gel tube, XAD-2 tube, and IOM inhalable dust sampler were used for the air sampling, and the flow rates were 50ml min-1, 50ml min-1, and 1000ml min-1, respectively. After 6-hour sampling, the filters were weighed and the samplers were desorbed by ethyl alcohol:water (95:5) or toluene followed by the analysis with gas chromatograph and mass spectrometer (GC/MS). In addition, questionnaires were administrated to the bakers to collect the information regarding the disease history of asthma, work conditions and related symptoms.

Results: From questionnaires, the symptoms of respiratory and dermal irritation were significantly higher for the exposure group, and only a few bakers wore personal protection equipment. It was found that various compounds and high concentration of flour dust existed in the air of the bakeries. In some work groups, especially for dough making, the environmental concentration of flour dust exceeded the ACGIH® TLV®-TWA (0.5 mg/m3). In addition, other airborne chemicals, such as 2,3-butanedione, 2,3-pentanedione, furfural, and acetaldehyde, were also detected around ovens and bakeries with various levels.

Conclusions: The results indicated that airborne chemical exposure is a problem worthy of attention in the bakeries. Although the permissible exposure limits of some detected chemicals have not been set, the respiratory symptoms were still observed. Therefore, monitoring the indoor air quality and improving the ventilation systems are both crucial to preventing work related exposures in the bakeries.



Development of a Pre-Filter for Thermal Desorption Tubes

C. Chang, K. Yang, C. Lin, S. Huang, N. Yu, and C. Chen, Department of Public Health, National Taiwan University, Taipei, Taiwan; Y. Kuo, Chung-hwa University of Medical Technology, Tainan, Taiwan; C. Chen, Institute of Labor, Occupational Safety and Health, Ministry of Labor, New Taipei City, Taiwan

Objective: Thermal desorption tubes are commonly used to quantify trace amounts of volatile organic compounds in air. Previous studies have demonstrated that the aerosol loading on the sorbent could significantly influence the adsorption and desorption characteristics. Normally, a piece of glass wool is placed in front of the sorbent, but filtration efficiency data can be limited. This study aimed to evaluate the filtration characteristic of the glass wool, and to design a pre-filter for the better performance of thermal desorption tubes.

Methods: A constant output aerosol generator and an ultrasonic atomizing nozzle were used to generate sub-micrometer sized and micrometer sized aerosol particles, respectively. A scanning mobility particle sizer and an aerodynamic particle sizer were employed to measure the aerosol concentration and size distribution upstream and downstream of the test filter. The pressure drop across the filter was simultaneously monitored. Glass wool, stainless steel mesh (#400, #1500), polyurethane foam (110 ppi) and filter disc cut from N95 filtering facepieces were tested in this work.

Results: The experimental results showed that the most penetrating particle size (MPPS) of the glass wool was 0.3-0.5 μm and the aerosol penetration of MPPS was about 60-75%, under the sampling flow of 0.2 L/min. To reach the same level of performance of glass wool, it took 60 layers of #400 stainless steel mesh. Higher aerosol collection efficiency (90%) could be achieved by increasing the mesh number and disc size (to reduce face velocity). The use of stainless steel mesh was too clumsy because of the size. For 110 ppi foam, the total height of the foam disc was estimated to be 30 cm to attain the required collection efficiency (90%). The aerosol collection efficiency could be enhanced by increasing the foam packing density. However, there was no guarantee of the packing quality to gain stable performance. The use of N95 filter disc appeared quite promising. The aerosol penetration was 5% and pressure drop was only 9.8 mmH2O, the lowest among all tested materials.

Conclusions: The glass wool pieces did not provide stable and sufficient filtration efficiency to protect the sorbents from aerosol contamination. Among the filter materials tested, the N95 filter worked best, for low cost, low pressure drop and stable quality. The oil-resistant P95 filter could be used when oil aerosol particles were present in the workplace.



IOM Inhalable and Respirable Sampling Compared to Conventional Total and Respirable Sampling for Assessing Welders Exposure to Manganese

F. Akbar-Khanzadeh, M. Shomody, S. Milz, A. Ames, and M. Valigosky, UT HSC College of Medicine, Toledo, OH

Objective: Total and respirable concentrations of airborne manganese (Mn) are conventionally determined by using two separate sampling devices/methods. The Institute of Occupational Medicine (IOM) technique can be used to determine inhalable and respirable concentrations of airborne Mn by using only one device. There are currently no known published studies that compared these methods during welder’s exposure to Mn.

Methods: In this study, the OSHA sampling method was compared with IOM dual fraction for assessing occupational exposure to airborne Mn during Shielded Metal Arc Welding (SMAW). Welding was performed in a barge at a marine facility. Using OSHA Method, an aluminum cyclone was loaded with a 25 mm Mixed Cellulose Ester (MCE) filter to sample respirable Mn contaminant. A filter cassette loaded with a 25 mm MCE filter was used to sample total Mn contaminant. The IOM sampler was used to sample inhalable and respirable fractions simultaneously by a foam insert with specific porosity to trap inhalable particles, and respirable size particles are allowed to pass through and be collected on a 25 mm MCE filter. All monitoring was performed by area sampling. A total of 20 side by side samples were collected for respirable Mn and 18 side by side samples were collected for inhalable and total Mn.

Results: The volume of air sampled ranged from 202.2-1077 liters. Concentration (mg/m3) of respirable Mn by IOM method ranged from 0.00-0.41(mean±sd; 0.13±0.14) and by conventional method from 0.00-0.51 (0.19±0.18). Inhalable Mn ranged from 0.01- 0.52 (0.20±0.19) and total Mn from 0.01-0.41 (0.21±0.18). Conventional respirable readings, except one, were consistently higher than those of the IOM respirable readings (slope = 0.746; r2 = 0.943) and the difference of the means was significant (p < 0.01). The mean concentration of inhalable Mn was not significantly different from the mean of total Mn (slope=1.02; r2=0.921).

Conclusions: The findings of this study suggest that for sampling airborne Mn during SMAW welding: (1) the IOM respirable sampler may not be suitable as an alternative meth​​​od to the conventional respirable sampler; and (2) the IOM inhalable sampler may be used as an alternative method to conventional total sampler.



Treated and Untreated Rock Dusts: Silica Content and Physical Characterization

J. Soo, T. Lee, W. Chisholm, D. Farcas, D. Schwegler-Berry, and M. Harper, CDC/NIOSH/HELD/EAB, Morgantown, WV

Objective: To assess the free silica content and physical characteristics of four selected rock dusts consisting of calcium and/or magnesium carbonate, in both treated and untreated form.

Methods: Four selected rock dusts were investigated: AMC (untreated), AMC with X-10 (treated), Micro-White 100 (untreated) and Imerys Phase IV (treated blend of 87.5% Micro-White 100 and 12.5% Kotamite). For each rock dust, two different size fractions (bulk and respirable size fractions) were tested to determine quartz content (%). The selected rock dusts were aerosolized and introduced into an aerosol chamber. A total of 72 individual samples of respirable dust were collected using FSP10 cyclones. Particle size segregating samplings were conducted using a Micro-Orifice Uniform Deposit Impactor (MOUDI). Silica measurement was performed according to NIOSH Method 7603. Particle morphology was examined with a combination of scanning electron microscopy and energy-dispersive x-ray spectroscopy analysis (EDX).

Results: The silica content of AMC in respirable dust (0.84%) was the largest but not significantly different from that of AMC X-10 (0.68%). The Micro-White 100 had significantly lower silica content than the other rock dusts but was not significantly different from Imerys Phase IV. The respirable fraction of AMC dust, treated and untreated, had a significantly higher silica content than did the bulk material. Silica is enriched in the respirable fraction but not above the Mine Safety and Health Administration (MSHA) limit for silica in bulk dust. All particle size distributions showed log-normal distributions, with the mass median aerodynamic diameters between 1.2 and 5.3 µm and geometric standard deviations less than 2.8. The dust spectra from EDX analysis are predominantly from limestone, clay particles and gypsum particles. No free quartz particles were observed, but that is reasonable considering the low quantity of silica and the number of particles studied.

Conclusions: All four dusts contained respirable silica. Treated rock dusts had slightly lower silica content than untreated ones. Silica can be elevated in the respirable fraction compared to the bulk, but this enrichment is not likely to lead to silica concentrations above the MSHA Permissible Exposure Limit (PEL), provided there is compliance with the PEL for respirable dust.



Vermiculite Containing Asbestos & Zonolite Insulation

D. Ewert, RJ Lee Group, Monroeville, PA

Situation/Problem: Since the association between asbestos related disease and Libby, Montana vermiculite mining was first proven, products containing vermiculite have consistently been classified as a hazard. In fact, since 2013 all vermiculite insulting materials have been regulated under New York State laws as Asbestos Containing Material (ACM). Further, the EPA states clearly in its homeowner outreach that "YOU SHOULD ASSUME THE VERMICULITE CONTAINS ASBESTOS AND DO NOT DISTURB IT!" Obviously, these approaches to vermiculite insulation are real and impact the lives of property owners and contractors every day.

Resolution: A new method was developed for the sample preparation and analysis of vermiculite containing materials to accurately speciate and quantify the asbestiform mineral which exists in vermiculite containing ores and finished products. This achievement is possible via a technique which chemically dissolves vermiculite and other interfering substances. Scanning Electron Microscopy and Energy Dispersive Spectroscopy speciate and quantify any amphibole species which occur. This technique achieves a detection limit of 0.01%.

Results: The method accurately detects and quantifies asbestiform minerals embedded in vermiculite. In July of 2014, the method (LAB.055.1) received New York State Dept. of Health certification for the analysis of asbestos in Spray-On Fireproofing Containing Vermiculite (SOF-V). Numerous samples have been analyzed including amphibole-spiked fireproofing materials as well as pure Zonolite based insulating products originating from Libby, Montana. The resulting data will demonstrate the unique ability of this technique to not only make 100% of the amphibole species available for inspection, but also to consistently and reproducibly determine the asbestos content in vermiculite containing materials.

Lessons learned: Given the impact and importance of accurately characterizing the amphibole asbestos content of Libby-based vermiculite containing materials, methods capable of accurately and precisely defining the asbestos content are a critical to any health assessments being performed. This work describes the results of one such method and builds awareness of the true asbestos content which exists in those vermiculite containing materials we now treat as asbestos.​