Time-weighted Average Sampling Research Articles

Noise Exposure and Evaluation at Tire- Changing Facilities.

Thirty (30) personal noise-exposure samples were collected on 20 tire-changing and repair technicians in three tire-changing facilities to determine their personal noise exposures and to estimate the maximum number of tire changes that could be performed without exceeding occupational exposure limits. Of the 30 projected 8-h time-weighted average noise samples, none exceeded the Occupational Safety and Health Administration's Permissible Exposure Limit, 1 (3%) exceeded the Occupational Safety and Health Administration's Action Level, and 18 (60%) exceeded the American Conference for Governmental Industrial Hygienists Threshold limit Value of 85 dBA, indicating the need for a hearing loss prevention program. The average shift time for the technicians was 6 h and 42 min and the average number of tire changes was 18. Based on the projected 8-h noise exposure 95% upper confidence limits, the estimated maximum number of tires that could be changed without exceeding the Occupational Safety and Health Administration's noise action level was 32 tires, the permissible exposure limit greater than 40 tires, and the American Conference of Industrial Hygienists' Threshold Limit Value was less than 20 tires. In addition, area noise samples of tire-changing equipment were taken with a sound-level meter to identify the noise sources that contributed to the tire technicians' exposures. The air ratchet, tire-changing machine, and tire-bead seater were measured at noise levels >85 dBA, increasing the risk of noise-induced hearing loss to the technicians.

An analysis of workplace exposures to asbestos at three steel mills located in the United States (1972-1982).

The objective is to present historical asbestos airborne concentrations associated with activities involving presumably asbestos-containing materials in steel mills. A total of 138 historical industrial hygiene air samples collected in three US steel mills from 1972 to 1982 were analyzed. The majority of samples were collected during relining of open hearth furnaces, stoves, and blast furnaces by steel mill bricklayers and bricklayer helpers. Over 75% of the samples (n = 106) were collected for 50 min or less, four samples were collected for 227 to 306 min, and sample durations were not reported for the remaining 28 samples. Average airborne fiber concentrations measured during relining activities of open hearth furnaces, stoves, and blast furnaces were 0.21 f/cc, 0.72 f/cc and 0.13 f/cc phase-contrast microscopy (PCM), respectively. Measured airborne fiber concentrations of four time-weighted average (TWA) samples (>227 min) averaged 0.045 f/cc. Estimated 8-h TWAs concentrations averaged 0.34 f/cc for bricklayers and 0.2 f/cc bricklayer helpers. While 8-h TWA concentration estimates for monitored tasks/jobs may often have exceeded current Occupational Safety and Health Administration (OSHA) Permissible Exposure Limits (PELs), they did not exceed relevant contemporaneous occupational exposure standards. This analysis provides a better understanding of historical airborne asbestos exposures that bricklayers and other tradesmen experienced during furnace and stove work in the US steel mills.

Development of Time-Weighted Average Sampling of Odorous Volatile Organic Compounds in Air with Solid-Phase Microextraction Fiber Housed inside a GC Glass Liner: Proof of Concept.

Finding farm-proven, robust sampling technologies for measurement of odorous volatile organic compounds (VOCs) and evaluating the mitigation of nuisance emissions continues to be a challenge. The objective of this research was to develop a new method for quantification of odorous VOCs in air using time-weighted average (TWA) sampling. The main goal was to transform a fragile lab-based technology (i.e., solid-phase microextraction, SPME) into a rugged sampler that can be deployed for longer periods in remote locations. The developed method addresses the need to improve conventional TWA SPME that suffers from the influence of the metallic SPME needle on the sampling process. We eliminated exposure to metallic parts and replaced them with a glass tube to facilitate diffusion from odorous air onto an exposed SPME fiber. A standard gas chromatography (GC) liner recommended for SPME injections was adopted for this purpose. Acetic acid, a common odorous VOC, was selected as a model compound to prove the concept. GC with mass spectrometry (GC–MS) was used for air analysis. An SPME fiber exposed inside a glass liner followed the Fick’s law of diffusion model. There was a linear relationship between extraction time and mass extracted up to 12 h (R2 > 0.99) and the inverse of retraction depth (1/Z) (R2 > 0.99). The amount of VOC adsorbed via the TWA SPME using a GC glass liner to protect the SPME was reproducible. The limit of detection (LOD, signal-to-noise ratio (S/N) = 3) and limit of quantification (LOQ, S/N = 5) were 10 and 18 µg·m−3 (4.3 and 7.2 ppbV), respectively. There was no apparent difference relative to glass liner conditioning, offering a practical simplification for use in the field. The new method related well to field conditions when comparing it to the conventional method based on sorbent tubes. This research shows that an SPME fiber exposed inside a glass liner can be a promising, practical, simple approach for field applications to quantify odorous VOCs.

Optimization of Time-Weighted Average Air Sampling by Solid-Phase Microextraction Fibers Using Finite Element Analysis Software.

Determination of time-weighted average (TWA) concentrations of volatile organic compounds (VOCs) in air using solid-phase microextraction (SPME) is advantageous over other sampling techniques, but is often characterized by insufficient accuracies, particularly at longer sampling times. Experimental investigation of this issue and disclosing the origin of the problem is problematic and often not practically feasible due to high uncertainties. This research is aimed at developing the model of the TWA extraction process and optimization of TWA air sampling by SPME using finite element analysis software (COMSOL Multiphysics, Burlington, MA, USA). It was established that sampling by porous SPME coatings with high affinity to analytes is affected by slow diffusion of analytes inside the coating, an increase of their concentrations in the air near the fiber tip due to equilibration, and eventual lower sampling rate. The increase of a fiber retraction depth (Z) resulted in better recoveries. Sampling of studied VOCs using 23 ga Carboxen/polydimethylsiloxane (Car/PDMS) assembly at maximum possible Z (40 mm) was proven to provide more accurate results. Alternative sampling configuration based on 78.5 × 0.75 mm internal diameter SPME liner was proven to provide similar accuracy at improved detection limits. Its modification with the decreased internal diameter from the sampling side should provide even better recoveries. The results obtained can be used to develop a more accurate analytical method for determination of TWA concentrations of VOCs in air using SPME. The developed model can be used to simulate sampling of other environments (process gases, water) by retracted SPME fibers.

Toluene Diisocyanate Exposure: Exposure Assessment and Development of Cross-Facility Similar Exposure Groups Among Toluene Diisocyanate Production Plants.

The objective of this study was to characterize workplace toluene diisocyanate (TDI) exposures using standardized industrial hygiene exposure assessment procedures for use in a prospective epidemiologic study of occupational asthma. Over 2300 representative routine full shift time-weighted average (TWA) and short-term high potential exposure tasks (HPETs) air samples in groups across three TDI plants were collected over a nearly 7-year period. Data-derived similar exposure groups (SuperSEGs) were developed across the plants based on TWA sampling using cluster analysis. Individual cumulative exposure estimates were developed on the basis of the SuperSEGs. Workplace TWA exposures to TDI were adequately characterized quantitatively, but HPET exposures were adequately characterized only by qualitative measures. The mean TWA exposure was 0.65 parts per billion for 1594 routine samples. These TWA and HPET exposures can be used to support exposure-response analyses.

Carbon Nanotube and Nanofiber Exposure Assessments: An Analysis of 14 Site Visits.

Recent evidence has suggested the potential for wide-ranging health effects that could result from exposure to carbon nanotubes (CNT) and carbon nanofibers (CNF). In response, the National Institute for Occupational Safety and Health (NIOSH) set a recommended exposure limit (REL) for CNT and CNF: 1 µg m(-3) as an 8-h time weighted average (TWA) of elemental carbon (EC) for the respirable size fraction. The purpose of this study was to conduct an industrywide exposure assessment among US CNT and CNF manufacturers and users. Fourteen total sites were visited to assess exposures to CNT (13 sites) and CNF (1 site). Personal breathing zone (PBZ) and area samples were collected for both the inhalable and respirable mass concentration of EC, using NIOSH Method 5040. Inhalable PBZ samples were collected at nine sites while at the remaining five sites both respirable and inhalable PBZ samples were collected side-by-side. Transmission electron microscopy (TEM) PBZ and area samples were also collected at the inhalable size fraction and analyzed to quantify and size CNT and CNF agglomerate and fibrous exposures. Respirable EC PBZ concentrations ranged from 0.02 to 2.94 µg m(-3) with a geometric mean (GM) of 0.34 µg m(-3) and an 8-h TWA of 0.16 µg m(-3). PBZ samples at the inhalable size fraction for EC ranged from 0.01 to 79.57 µg m(-3) with a GM of 1.21 µg m(-3). PBZ samples analyzed by TEM showed concentrations ranging from 0.0001 to 1.613 CNT or CNF-structures per cm(3) with a GM of 0.008 and an 8-h TWA concentration of 0.003. The most common CNT structure sizes were found to be larger agglomerates in the 2-5 µm range as well as agglomerates >5 µm. A statistically significant correlation was observed between the inhalable samples for the mass of EC and structure counts by TEM (Spearman ρ = 0.39, P < 0.0001). Overall, EC PBZ and area TWA samples were below the NIOSH REL (96% were <1 μg m(-3) at the respirable size fraction), while 30% of the inhalable PBZ EC samples were found to be >1 μg m(-3). Until more information is known about health effects associated with larger agglomerates, it seems prudent to assess worker exposure to airborne CNT and CNF materials by monitoring EC at both the respirable and inhalable size fractions. Concurrent TEM samples should be collected to confirm the presence of CNT and CNF.

Analysis of trace contaminants in hot gas streams using time-weighted average solid-phase microextraction: Pilot-scale validation

A new method was developed for collecting, identifying and quantifying contaminants in hot process gas streams using time-weighted average (TWA) passive sampling with retracted solid-phase microextraction (SPME) and gas chromatography. The previous lab scale proof-of-concept with benzene was expanded to include the remaining major tar compounds of interest in syngas: toluene, styrene, indene, and naphthalene. The new method was tested on high T (⩾100°C) process gas from a pilot-scale fluidized bed gasifier feeding switchgrass and compared side-by-side with conventional impingers-based method. Fourteen additional compounds were identified, representing 40–60% improvement over the conventional method’s detection capacity. Differences between the two methods were 1–20% and as much as 40–100% depending on the sampling location. Compared to the inconsistent conventional method, the SPME-TWA offered a simplified, solvent-free approach capable of drastically reducing sampling and sample preparation time and improving analytical reliability. The improved sensitivity of the new method enabled identification and quantification of VOCs beyond the capability of the conventional approaches, reaching concentrations in the ppb range (low mg/m3). RSDs associated with the TWA-SPME were <10%, with most lab-based trials yielding <2%. Calibrations were performed down to the lowest expected values of tar concentrations in ppb ranges (low mg/Nm3, with successful measurement of tar concentrations at times >4000ppm (up to 10g/Nm3). The new method can be a valid alternative to the conventional method for light tar quantification under certain conditions. The opportunity also exists to exploit TWA-SPME for process gas streams analysis e.g., pyrolysis vapors and combustion exhaust.

Gaseous and Particle‐bound VOC Products of Combustion Extracted by Needle Trap Samplers

AbstractGaseous benzene, toluene, ethylbenzene and o‐xylene (BTEX) were extracted by using the divinylbenzene (DVB) particles (mesh sizes 60–80, 80–100 and 100–120) as sorbents packed in passive needle trap samplers (NTS). This study performed feasibility tests of these self‐designed DVB‐NTS as diffusive time‐weighted average (TWA) samplers and compared extraction efficiency with that of 100 mm polydimethylsiloxane‐solid phase microextration (PDMS‐SPME) fiber for sampling gaseous and particle‐bound volatile organic compounds (VOCs) from burning mosquito coils. Experimental results indicated that extraction rate of NTS is a reliable index in extracting VOCs. Additionally, comparisons of the NTS in extracting BTEX mass showed the NTS packed with the smallest diameters of adsorbent particles (100–120 mesh DVB) were the most effective. The mass of gaseous BTEX extracted by 100 μm PDMS‐SPME fiber were substantially lower than that extracted by DVB‐NTS of all meshes for the 30‐min TWA sampling of burning mosquito coils, and NTS packed with 100–120 mesh DVB adsorbed BTEX 50–120 ng BTEX. Particles clogging inside the packed phase of NTS inhibited VOC extraction performance after 3–5 samplings of burning particles, especially NTS packed with small‐diameter adsorbents.

Time-Weighted Average Sampling of Airborne Propylene Glycol Ethers by a Solid-Phase Microextraction Device

A solid-phase microextraction (SPME) device was used as a diffusive sampler for airborne propylene glycol ethers (PGEs), including propylene glycol monomethyl ether (PGME), propylene glycol monomethyl ether acetate (PGMEA), and dipropylene glycol monomethyl ether (DPGME). Carboxen-polydimethylsiloxane (CAR/PDMS) SPME fiber was selected for this study. A polytetrafluoroethylene (PTFE) tubing was used as the holder, and the SPME fiber assembly was inserted into the tubing as a diffusive sampler. The diffusion path length and area of the sampler were 0.3 cm and 0.00086 cm2, respectively. The theoretical sampling constants at 30°C and 1 atm for PGME, PGMEA, and DPGME were 1.50 × 10−2, 1.23 × 10−2 and 1.14 × 10−2 cm3 min−1, respectively. For evaluations, known concentrations of PGEs around the threshold limit values/time-weighted average with specific relative humidities (10% and 80%) were generated both by the air bag method and the dynamic generation system, while 15, 30, 60, 120, and 240 min were selected as the time periods for vapor exposures. Comparisons of the SPME diffusive sampling method to Occupational Safety and Health Administration (OSHA) organic Method 99 were performed side-by-side in an exposure chamber at 30°C for PGME. A gas chromatography/flame ionization detector (GC/FID) was used for sample analysis. The experimental sampling constants of the sampler at 30°C were (6.93 ± 0.12) × 10−1, (4.72 ± 0.03) × 10−1, and (3.29 ± 0.20) × 10−1 cm3 min−1 for PGME, PGMEA, and DPGME, respectively. The adsorption of chemicals on the stainless steel needle of the SPME fiber was suspected to be one of the reasons why significant differences between theoretical and experimental sampling rates were observed. Correlations between the results for PGME from both SPME device and OSHA organic Method 99 were linear (r = 0.9984) and consistent (slope = 0.97 ± 0.03). Face velocity (0–0.18 m/s) also proved to have no effects on the sampler. However, the effects of temperature and humidity have been observed. Therefore, adjustments of experimental sampling constants at different environmental conditions will be necessary.

Breakthrough indicator for aromatic VOCs using needle trap samplers for activated carbon adsorbent

Internal circulation cabinets equipped with granular activated carbon (GAC) for adsorbing volatile organic compounds (VOCs) are widely used to store bottles containing organic solvents in universities, colleges, and hospital laboratories throughout Taiwan. This work evaluates the VOC adsorption capacities of GAC using various adsorption times for gas stream mixtures of 100 ppm toluene and 100 ppm o-xylene. Additionally, needle trap sampling (NTS) technology was used to indicate the time for renewing the GAC to avoid VOC breakthrough from adsorbents. Experimental results demonstrate that the proposed models can linearly express toluene and o-xylene adsorption capacities as the natural logarithm of adsorption time (ln(t)) and can accurately simulate the equilibrium adsorption capacities (Qe, g VOCs/g GAC) for gaseous toluene and o-xylene. The NTS, packed with 60–80 mesh divinylbenzene (DVB) particles, was compared in terms of extraction efficiency by simultaneously using the 75-μm Carboxen/polydimethylsiloxane–solid-phase microextraction (Carboxen/PDMS-SPME) fiber for time-weighted average (TWA) sampling, and experimental results indicated that the packed DVB-NTS achieved higher toluene extraction rates. Additionally, the NTS installed in the outlet air stream for adsorbing toluene and o-xylene exhausted through GAC accurately indicated toluene and o-xylene breakthrough times of 4700–5000 min. The GAC-NTS operational instructions to indicate the replacing time of adsorbent in the internal circulation cabinets are also included in this paper. Implications: The needle trap sampler has been evaluated to be a reliable device for indicating breakthrough of volatile organic compounds (VOCs) from adsorbent, which is used for adsorbing VOC emissions in a chemical storage cabinet. Applying this advanced indication technology for indicating VOC breakthrough would substantially reduce indoor emissions of VOCs in laboratories.

Field application of SPME as a novel tool for occupational exposure assessment with inhalational anesthetics

Occupational exposure to inhalational anesthetics occurs routinely in operating rooms. It could induce serious health hazards and diseases. This exposure assessment is a crucial step in determining risks. In this study, a pen-shaped holder for solid-phase microextraction (SPME) sampler was successfully applied as a time-weighted average sampling tool for workshift exposure assessment of operation room staff to halothane. It proved to be very convenient for use in occupational environments such as operation rooms. Samples were analyzed by a gas chromatography-mass spectrometry. The validity of the SPME method was checked in real-world conditions with Occupational Safety and Health Administration (OSHA) 103 standard method for the determination of inhalational anesthetics. A good agreement between OSHA 103 and SPME methods was obtained and results demonstrated no statistically significant differences in anesthetic concentrations determined by the two analytical methods (p ≥ 0.05). It is concluded that SPME in retracted mode could successfully be applied in occupational exposure assessment purposes.

Development of a new time-integrative sampler using in situ solvent extraction

Despite the great success of time-weighted average passive sampling of hydrophobic contaminants, such as PCBs and PAHs, the sampling of polar organic compounds still presents a challenge because the equilibrium between water and most sampling phases is attained in a relatively short time. In this study, we proposed a new time-integrative sampler using in situ solvent extraction (TISIS) for polar organic chemicals. The sampler was composed of a 15 cm poly(dimethylsiloxane) (PDMS) tubing, with an internal diameter of 0.5 mm and wall thickness of 0.5 mm, through which an extraction solvent (acetonitrile) was passed. Four polar organic contaminants, caffeine, atrazine, diuron and 17α-ethynylestradiol, were chosen for the evaluation of the performance of the sampler. Without the use of in situ solvent extraction, the PDMS tubing when exposed to a constant aqueous concentration of the four model compounds was able to linearly accumulate those compounds for less than 12 h and equilibrium between the PDMS tubing and water was attained in 2 d under our laboratory conditions. However, TISIS when exposed to a constant aqueous concentration was able to linearly accumulate all the model compounds without any exposure time limitation. The measured sampling rates at three different extraction flow rates (0.2, 0.5, 1.5 mL min −1) were similar, regardless of the chemicals, indicating that the overall mass transfer from aqueous solution to the extraction solvent was most likely dominated by partitioning to the PDMS tubing and the internal diffusion within PDMS. In addition, a pulsed exposure experiment confirmed that TISIS operated in a time-integrative mode when the environmental concentration was highly fluctuated.

Sampling and analysis of nanoparticles with cold fibre SPME device

A new approach is described to capture nano-size aerosols on internally-cooled micro tubing of the solid-phase microextraction (SPME) device followed by convenient introduction of the collected analytes into analytical instrument. Particles were generated using an aerosol formation by homogeneous nucleation of an organic vapor, and subsequent growth to nano-size particles by coagulation of decanedioic acid, bis[2-ethylhexyl] ester (DEHS). The approach was validated by using carbon dioxide-cooled micro tubing to collect the nanosize DEHS particles followed by analyses on GC-flame ionization detector (FID). Particle size ranged from 150 to 590 nm. Temperature difference between the SPME device and DEHS particles mixture created a temperature gradient and resulted in thermophoretic effect that was determining the extraction rate. SPME device was cooled to as low as -75 degrees C, while the DEHS remained close to room temperature. Several aspects of nanoparticle sampling were tested to demonstrate the principle of the sampling approach. These included the effects of thermal gradient, sample flow rate, sampling time, CO(2) delivery mode (constant coolant delivery vs. constant temperature), and particle size. Results were normalized to measure particulate concentrations using direct sampling with PTFE filters. Nanoparticle extractions of DEHS mass were proportional to sampling time. Normalized mass of DEHS extracted increased with increase in temperature gradient and with increase of the cross flow velocity. Preliminary results indicate that the variation of heat transfer boundary layer caused by the variation in the cross flow velocity produce self-compensating effect at constant coolant delivery, indicating that this approach could be used for field determinations including the time-weighted average sampling of nanoparticles. Thus, it may be possible to develop simple device based on this concept for field applications.

Chemicals present in automobile traffic tunnels and the possible community health hazards: A review of the literature

Dozens of volatile and semivolatile organic compounds can be detected in vehicle exhaust, along with numerous metals and oxides of sulfur, nitrogen, and carbon. While the adverse effects of these chemicals have been extensively studied surrounding open roadways, the hazards to local residents and commuters resulting from the presence of tunnel emission chemicals are less well known. Commuters and workers within tunnels are also exposed to tunnel atmospheres, and the risks have only been evaluated to a limited extent. Approximately 50 studies conducted at more than 35 different international traffic tunnels were reviewed in order to characterize the potential health impact on individuals residing near these tunnels. One objective of this article is to identify those chemicals that deserve further study in order to understand the hazards to humans who work in these tunnels, as well as the risks to those in the surrounding community. The second objective is to present the available information regarding the hazards to those living near these tunnels. The published information, for the most part, indicates that the concentration of most toxicants detected in communities exposed to tunnel emissions are below those concentrations that are generally considered to pose either a significant acute or chronic health hazard. However, there have been no comprehensive studies that have evaluated the concentration of all of the relevant toxicants on a real-time basis or using repetitive time-weighted average sampling. Based on our analysis of the existing information appearing in peer-reviewed literature and government reports, additional information on the variation of concentrations of various chemicals over time near the tunnel exits would be helpful. Optimally, these would be better if evaluated in conjunction with traffic magnitude and vehicle type. It would also be useful to further characterize acute exposures to commuters or tunnel workers during times of heavy volume or slow-moving traffic due to accidents within the tunnel structure, when tunnel pollutant levels would be expected to be substantially elevated. A recent review by the Australia’s National Health and Medical Research Council also discusses tunnel and air quality in detail (2008). Nearly 300 references are cited.

Task-Based Lead Exposures and Work Site Characteristics of Bridge Surface Preparation and Painting Contractors

This study of bridge painters working for small contractors in Massachusetts investigated the causes of elevated blood lead levels and assessed their exposure to lead. Bridge work sites were evaluated for a 2-week period during which personal and area air samples and information on work site characteristics and lead abatement methods were gathered. Short-duration personal inhalable samples collected from 18 tasks had geometric means (GM) of 3 μg/m3 to 7286 μg/m3. Full-shift, time-weighted average (TWA) inhalable samples (⩾6 hours) collected from selected workers and work sites had GMs of 2 μg/m3 to15,704 μg/m3; 80% of samples exceeded the permissible exposure limit (PEL) of 50 μg/m3, on average by a factor of 30. Area inhalable samples collected from three locations ranged from 2 μg/m3 to 40,866 μg/m3 from inside the containment, 2 μg/m3 to 471 μg/m3 from a distance of <6 meters, and 2 μg/m3 to 121 μg/m3 from >6 meters from the containment. Seventy nine percent of the area samples from inside the containment exceeded the PEL on average by a factor of 140. Through observations of work site characteristics, opportunities for improving work methods were identified, particularly the institution of engineering controls (which were only occasionally present) and improvement in the design and construction of the containment structure. The high levels of airborne lead exposures indicate a potential for serious exposure hazard for workers and environmental contamination, which can be mitigated through administrative and engineering controls. Although these data were collected over 10 years ago, a 2005 regulatory review by the Occupational Safety and Health Administration (OSHA) of its lead in construction standard reported that elevated lead exposures and blood lead levels, high occurrence of noncompliance with the lead standard, and nonimplementation of newer technology especially among small painting firms employing <10 workers are still widespread. As a result, the findings of this study are still quite germane even a decade after the introduction of the new OSHA standard.

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

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.

Biological exposure assessment to tetrachloroethylene for workers in the dry cleaning industry.

BackgroundThe purpose of this study was to assess the feasibility of conducting biological tetrachloroethylene (perchloroethylene, PCE) exposure assessments of dry cleaning employees in conjunction with evaluation of possible PCE health effects.MethodsEighteen women from four dry cleaning facilities in southwestern Ohio were monitored in a pilot study of workers with PCE exposure. Personal breathing zone samples were collected from each employee on two consecutive work days. Biological monitoring included a single measurement of PCE in blood and multiple measurements of pre- and post-shift PCE in exhaled breath and trichloroacetic acid (TCA) in urine.ResultsPost-shift PCE in exhaled breath gradually increased throughout the work week. Statistically significant correlations were observed among the exposure indices. Decreases in PCE in exhaled breath and TCA in urine were observed after two days without exposure to PCE. A mixed-effects model identified statistically significant associations between PCE in exhaled breath and airborne PCE time weighted average (TWA) after adjusting for a random participant effect and fixed effects of time and body mass index.ConclusionAlthough comprehensive, our sampling strategy was challenging to implement due to fluctuating work schedules and the number (pre- and post-shift on three consecutive days) and multiplicity (air, blood, exhaled breath, and urine) of samples collected. PCE in blood is the preferred biological index to monitor exposures, but may make recruitment difficult. PCE TWA sampling is an appropriate surrogate, although more field intensive. Repeated measures of exposure and mixed-effects modeling may be required for future studies due to high within-subject variability. Workers should be monitored over a long enough period of time to allow the use of a lag term.

Time-Weighted Average Water Sampling in Lake Ontario with Solid-Phase Microextraction Passive Samplers

In this study, three types of solid-phase microextraction (SPME) passive samplers, including a fiber-retracted device, a polydimethylsiloxane (PDMS)-rod and a PDMS-membrane, were evaluated to determine the time weighted average (TWA) concentrations of polycyclic aromatic hydrocarbons (PAHs) in Hamilton Harbor (the western tip of Lake Ontario, ON, Canada). Field trials demonstrated that these types of SPME samplers are suitable for the long-term monitoring of organic pollutants in water. These samplers possess all of the advantages of SPME: they are solvent-free, sampling, extraction and concentration are combined into one step, and they can be directly injected into a gas chromatograph (GC) for analysis without further treatment. These samplers also address the additional needs of a passive sampling technique: they are economical, easy to deploy, and the TWA concentrations of target analytes can be obtained with one sampler. Moreover, the mass uptake of these samplers is independent of the face velocity, or the effect can be calibrated, which is desirable for long-term field sampling, especially when the convection conditions of the sampling environment are difficult to measure and calibrate. Among the three types of SPME samplers that were tested, the PDMS-membrane possesses the highest surface-to-volume ratio, which results in the highest sensitivity and mass uptake and the lowest detection level.

Time-weighted average water sampling with a diffusion-based solid-phase microextraction device

A new diffusion-based solid-phase microextraction (SPME) time-weighted average (TWA) field water sampling device was developed and investigated by field trial. The sampler is constructed with copper tube and caps and a commercial SPME fiber assembly. The device possesses all advantages of SPME; it is solvent-free, reusable, combines sampling, isolation and enrichment into one step, and the fiber can be directly injected into a gas chromatograph for analysis with a commercial SPME fiber holder, without further treatment. Field trials in Laurel Creek (Waterloo, Ont., Canada) and Hamilton Harbour (Hamilton, Ont., Canada) illustrated that the device is durable, easy to deploy, and the mass uptake of the device is independent of the face velocity. The device provides good precision [relative standard deviations (RSDs) are less than 20%] and the data obtained with this device are quite comparable to those obtained with the spot sampling method, which demonstrates that the newly developed SPME water sampling device is suitable for long-term monitoring of organic pollutants in water.

On-rod standardization technique for time-weighted average water sampling with a polydimethylsiloxane rod

In this study, a polydimethylsiloxane (PDMS) rod was developed as a passive sampler, based on the solid-phase microextraction (SPME) technique. The on-rod standardization technique was applied to the PDMS rod passive sampler. Using the desorption of the pre-loaded standard on the PDMS rod to calibrate the absorption of the target analytes allows for the determination of the time-weighted average (TWA) concentrations of pollutants in the aqueous media. The PDMS rod passive sampler with the on-rod standardization technique was tested in the laboratory with a flow-through system and was subsequently applied to measure TWA concentrations of polycyclic aromatic hydrocarbons (PAHs) in the field (Hamilton Harbour, Hamilton, Ont., Canada). Both the laboratory and field experiments demonstrated that, with the on-rod standardization technique, the PDMS rod can be successfully used as a passive sampler for TWA water sampling in the field. The PDMS rod passive sampler benefits from the inherent advantages of the SPME approach: it incorporates sampling, isolation and enrichment into one step. The design of this system also addressed the additional needs for passive sampling techniques, providing an economical approach to field sampling that is also easy to deploy. Rather, with this approach, TWA concentrations of target analytes can be obtained by one sampler, and can be analyzed directly, with no further sample preparation treatment required.