A new approach for diffusive sampling based on SPME for occupational exposure assessment.

Passive sampling is a well-established methodology for the evaluation of exposures to environmental volatile organic compounds (VOCs). The solid-phase microextraction (SPME) technique is a reliable means of sampling VOCs in air. SPME is also being applied as a passive sampler to determine time-weighted average exposure. The use of SPME as a diffusive sampler was evaluated. The passive sampler is based on the use of a cylindrical diffusion cell (porous hydrophobic polyethylene) with an 80 µm carboxen/polydimethylsiloxane fiber to obtain radial diffusion of the analytes to the sorbent. Standard atmospheres of organic vapors in air were used to determine the experimental uptake rates for toluene and chlorobenzene. Toluene concentrations between 2 and 38 mg/m(3) with sampling times between 15 and 60 min were evaluated, as well as chlorobenzene concentrations between 2 and 47 mg/m(3) with sampling times between 30 and 60 min. The mean diffusive uptake rate was 2.14 mL/min for toluene and 2.57 mL/min for chlorobenzene, and no statistical significant effects of concentration and sampling time were observed under the studied conditions for the two compounds. Relative standard deviation ranged from 2.6 to 6.5%. The performance of the sampler under varying concentrations of toluene was also tested, showing that the sampler reflects the average exposure concentration. Effects of temperature, relative humidity, velocity of the air, back diffusion, competitive adsorption, and the stability of chlorobenzene in the sampler were also studied. Sampler behavior was tested in gas stations, and the results were successfully compared with a 3M-3500 diffusive sampler. The results are promising for using this new SPME device for diffusive monitoring for occupational exposure assessment.

Storage stability of ketones on carbon adsorbents.

Activated coconut carbon constitutes the more widely used sorbent for preconcentration of volatile organic compounds in sampling workplace air. Water vapour is always present in the air and its adsorption on the activated carbon surface is a serious drawback, mainly when sampling polar organic compounds, such as ketones. In this case, the recovery of the compounds diminishes; moreover, ketones can be decomposed during storage. Synthetic carbons contain less inorganic impurities and have a lower capacity for water adsorption than coconut charcoal. The aim of this work was to evaluate the storage stability of various ketones (acetone, 2-butanone, 4-methyl-2-pentanone and cyclohexanone) on different activated carbons and to study the effect of adsorbed water vapour under different storage conditions. The effect of storage temperature on extraction efficiencies was significant for each ketone in all the studied sorbents. Recovery was higher when samples were stored at 4 degrees C. The results obtained for storage stability of the studied ketones showed that the performance of synthetic carbons was better than for the coconut charcoals. The water adsorption and the ash content of the carbons can be a measure of the reactive sites that may chemisorb ketones or catalize their decomposition. Anasorb 747 showed good ketone stability at least for 7 days, except for cyclohexanone. After 30-days storage, the stability of the studied ketones was excellent on Carboxen 564. This sorbent had a nearly negligible ash content and the adsorbed water was much lower than for the other sorbents tested.

SPE-GC-MS for the sampling and determination of unmetabolized styrene in urine.

The urinary excretion of unmetabolized styrene can be a very good indicator for biomonitoring styrene in occupationally exposed people. The use of a new urine sampling system, involving a solid-phase extraction cartridge, offers several advantages for determining styrene. The advantages are especially related to the pre-analytical phase of styrene determination, which may be influenced by many variables. The effect on styrene recovery of sorbent type, eluting solvent, elution volume, elution flow-rate, and the addition of methanol to the washing solvent, was evaluated by experimental design methodology. As a result, Oasis HLB cartridges were selected for urine sampling, as well as 1.5 mL of ethyl acetate at 0.5 mL/min for eluting the retained styrene. These conditions were then applied to the validation of the solid-phase extraction combined with GC-MS method for the sampling and analysis of unmetabolized styrene in urine. The overall uncertainty was in the 12-22% range and the limit of detection was 2.2 microg/L for a 4 mL urine sample. The stability of styrene has been studied both in cartridges and in vials under different storage periods. After 1 month period the styrene stored on cartridges at room temperature remained stable, whereas this is not the case for styrene recovery from vials. The results obtained indicate that on-site solid-phase extraction of urine can provide a simple, accurate and reproducible sampling and analytical method for the biomonitoring of styrene in urine.

Evolution of occupational exposure to environmental levels of aromatic hydrocarbons in service stations.

During refuelling, people may easily be exposed to extremely high levels of gasoline vapour for a short time, although such exposure takes on more importance in the case of service station attendants. The volume of gasoline sold in refuelling operations and the ambient temperature can significantly increase the environmental level of benzene, toluene and xylene (BTX) vapours and, subsequently, the occupational risk of service station attendants. This is especially true in the case of benzene, the most important component of gasoline vapours from a toxicological point of view. The European Directive 98/70/EC, limiting the benzene composition of gasoline, and 94/63/EC, concerning the use of vapour recovery systems in the delivery of gasoline to services stations, were applied in Spain from January 2000 and 2002, respectively. In addition, a new limit value for occupational exposure of 3.25 mg/m(3) was fixed for benzene in Directive 97/42/EC, applied from June 2003. However, recent years have seen the growing use of diesel as well as of unleaded and reformulated gasoline. In this study, we analyse the differences found between air concentration levels of BTXs in 2000 and 2003, analysing samples taken from the personal breathing-zone of occupationally exposed workers in service stations. The results are compared with those obtained in a similar study carried out in 1995 (before the new regulations came into force). The study was carried out in two phases. The first phase was carried out in 2000, after application of the new legal regulation limiting the benzene concentration in gasoline. In this case, an occupationally exposed population of 28 service station attendants was sampled in July, with a mean ambient temperature of 30-31 degrees C. In the second phase, 19 exposed subjects were sampled in July 2003, one of the warmest months in recent years with mean temperatures of 35-36 degrees C during the time of exposure monitoring. The results were then compared with those obtained in 1995, for similar summer weather conditions (environmental temperature between 28 and 30 degrees C). A significant relationship between the volume of gasoline sold and the ambient concentration of aromatic hydrocarbons was found for each worker sampled in all three of the years. Furthermore, a significant decrease in the environmental levels of BTXs was observed after January 2000, especially in the case of benzene, with mean time-weighted average concentrations for 8 h of 736 microg/m(3) (range 272-1603) in 1995, 241 microg/m(3) (range 115-453) in 2000 and 163 microg/m(3) (range 36-564) in 2003, despite the high temperatures reached in the last mentioned year.

Urinary benzene determination by SPME/GC-MS. A study of variables by fractional factorial design and response surface methodology.

The urinary excretion of the unmetabolized benzene seems to be a very good index for biomonitoring benzene in occupationally exposed people. The use of solid phase microextraction (SPME) offers important advantages for its determination. Several variables can influence the benzene extraction process. Experimental design methodology was used to estimate the influence of the different variables and to evaluate the simultaneous effect of the more significant variables on the benzene extraction. The results showed that sample temperature, sample volume and their interaction were the more significant factors. A model was found that relates the amount of benzene extracted with the studied variables. The more adequate working conditions were: extraction temperature 15 degrees C, incubation time 1 min, extraction time 1 min and 2.5 ml of sample volume. The results indicate that this method is capable of providing sensitive and accurate results for the biomonitoring of benzene in urine.

Application of solid-phase microextraction and gas chromatography-mass spectrometry to the determination of volatile organic compounds in end-exhaled breath samples.

Analysis of exhaled air is of particular interest as an indicator of health as well as a tool for the diagnosis of diseases. It is also a very attractive procedure for the biological control of the exposition to hazardous solvents. This kind of analysis presents numerous advantages over other methods, the most important being that it is not an invasive procedure and, therefore, it is well accepted and can be applied to a wide range of compounds. Furthermore, the analysis is simplified since the matrix is less complex that in the case of blood or urine. In spite of these obvious advantages and the good results obtained, analysis of exhaled air is not in daily use, probably due to the fact that there are no normalized systems of sampling, thus making the interpretation of the results difficult. In this paper, a method for the determination of tetrachloroethylene in exhaled air using solid-phase microextraction is presented. This method, which can be applied to other volatile organic compounds, was developed with special emphasis of end-exhaled breath sampling. The sample is collected in a glass tube whose ends are closed once the exhalation is finished. The tube has an orifice sealed with a septum through which the fiber is inserted. Then, the fiber is desorbed in the injector of a gas chromatograph and the analysis is accomplished using mass spectrometry for the identification and quantification of the components. The proposed system avoids the need of complex sampling equipment and allows analysis of the alveolar fraction. Additionally, the system is economical and easy to handle, thus facilitating the development of normalized methods and its routine use in field studies.

Evaluation of environmental levels of aromatic hydrocarbons in gasoline service stations by gas chromatography.

The volume of gasoline sold in refuelling operations and the ambient temperature, can increase significantly the environmental levels of aromatic hydrocarbon vapours and subsequently, the occupational risk of gasoline service station attendants, specially in the case of benzene. We have evaluated the occupational exposure to aromatic hydrocarbons by means of personal-breathing-zone samples of gasoline vapours in a service station attendant population. This evaluation was carried out using diffusive samplers, in two periods at quite different temperatures (March and July). A significant relationship between the volume of gasoline sold during the shift and the ambient concentration of benzene, toluene, and xylenes was found for each worker sampled. Furthermore a significant difference was found between the time-weighted average concentration of aromatic compounds measured in March, with ambient temperatures of 14-15 degrees C and July, with temperatures of 28-30 degrees C. In addition, 20% of the population sampled in the last period were exposed to a time-weighted average concentration of benzene above the proposed Threshold Limit Value of 960 micrograms/m(3) of the American Conference of Governmental Industrial Hygienists (ACGIH).

Biological monitoring of occupational exposure to isoflurane by measurement of isoflurane exhaled breath.

The relationship between isoflurane environmental concentrations in operating rooms and the corresponding isoflurane concentration in the exhaled air of the operating personnel at the end of the exposure has been investigated. Isoflurane was retained in an adsorbent cartridge and after thermal desorption the concentration was estimated by gas chromatography. Significant correlation between environmental and exhaled air isoflurane concentrations allowed the establishment of a biological exposure index and biological exposure limits corresponding to proposed atmospheric threshold values.

Biological monitoring of styrene exposure and possible interference of acetone co-exposure.

The object of this study is the evaluation of some of the toxicokinetic effects of exposure to low concentrations of styrene, and the possible influence of simultaneous exposure to acetone. To this end we studied 19 workmen simultaneously exposed to both solvents. During a week of 4-h work shifts, the workmen underwent daily personal environmental monitoring and the collection of urine samples, at both the beginning and the end of the work period, for the determination of mandelic acid (MA) and phenylglyoxylic acid (PGA). The presence of the solvents in the atmosphere was evaluated using passive personal monitoring and gas chromatography. Average exposure to styrene and acetone were respectively 72.2 mg/m3 and 225.7 mg/m3. MA and PGA were quantified by high-performance liquid chromatography (HPLC). The daily urinary concentration averages, both at commencement and at the end of work shifts, of both the metabolites studied and of the sum of the two were in statistically significant linear correlation with the average daily styrene exposure. Concentrations of MA and PGA in urine samples collected at the start of the work shift averaged 61.5 mg/g creatinine and 45.2 mg/g creatinine respectively, representing 41% and 72% of those at the endo of the work shift which were 148.3 and 62.6 mg/g creatinine, respectively. With equal exposure to styrene, the average urinary concentrations of MA and PGA at both the beginning and end of the work shift increased significantly (P < 0.001) during the working week. Moreover, we found that with equal exposure to styrene, urinary excretion of MA, PGA and MA + PGA at the end of the shift was inversely correlated with the intensity of acetone exposure (r = 0.4659, 0.3410 and 0.542 respectively, P < 0.001). In conclusion, these results express slower urinary kinetics of styrene metabolites than is usually described in the literature, and favor a tendency to accumulate MA and PGA in the organism as a consequence of the retardation of urinary excretion kinetics. Acetone apparently represents one of the determining factors in this interference.

Behaviour of urinary 2,5-hexanedione in occupational co-exposure to n-hexane and acetone.

We analysed the relationship between free 2,5-hexanedione (2,5-HD) and total 2,5-HD in the urine of 87 workers exposed to n-hexane and other solvents (hexane isomers, acetone and toluene), in relation to different working conditions. The concentration of free 2,5-HD in urine of workers exposed to n-hexane was about 12% of total urinary 2,5-HD. The most significant correlation (r = 0.936) was that of total 2,5-HD in urine with environmental n-hexane and exhaled air. With equal exposure to n-hexane, the concentrations in urine of free and total 2,5-HD increased when cutaneous absorption was involved (gloves not used), during the working week and with co-exposure to acetone. An analysis of the relationship between combined exposure to acetone and urinary concentrations of the various forms of 2,5-HD suggests that acetone might influence the toxicokinetics of n-hexane, increasing the proportion of free 2,5-HD.

Purge-and-trap method for the determination of styrene in urine.

A purge-and-trap method for biological monitoring of styrene in urine was developed. Sorbent tubes packed with Tenax TA were used to trap styrene vapour purged from urine. Thermal desorption-gas chromatography was used for sorbent tubes analysis. The detection limit (0.70 micrograms/1), linearity range, recovery (> 94% for spiked urine samples) and repeatability for urine from occupational exposed workers show the suitability of the method for the determination of styrene in urine. One specific advantage of this method is the possibility of storage of the charged sorbent tubes during long periods of time without a significant loss of styrene. This approach can be used, with slight modifications, for urinary determination of several others organic contaminants commonly present in occupational exposures.

Correlation between concentrations of n-hexane and toluene in exhaled and environmental air in an occupationally exposed population.

We determined the correlations between the concentrations of n-hexane and toluene in exhaled and environmental air in the shoe manufacturing industry. Data were collected in 1988 and in 1992 from a total of 265 subjects. Environmental air samples were collected with personal diffusive samplers by adsorption on activated charcoal during exposure and from end-expired air (alveolar air) on cartridges of activated charcoal after exposure. Both compounds were desorbed with carbon disulphide and analysed by gas chromatography. Linear regression analyses showed a good correlation between environmental and end-expired air concentrations (r = 0.82 for n-hexane and r = 0.81 for toluene). These correlations allowed us to calculate the concentrations in expired air corresponding to current environmental limit values. The calculated concentrations in end-expired air that correspond to current environmental threshold limit values of 176 mg m-3 for n-hexane and 377 mg m-3 for toluene are 28 mg m-3 (95% confidence limit, 27-29 mg m-3) and 40 mg m-3 (95% confidence limit, 39-41 mg m-3), respectively. Similar correlations were found when the data from the two study periods were analysed separately.

Application of thermal desorption to the biological monitoring of organic compounds in exhaled breath.

We have developed a thermal desorption-gas chromatographic method for the analysis of organic compounds in exhaled breath air, to be used in the biological monitoring of environmental exposure. The exhaled breath sampler is based on the concentration of compounds present in alveolar air in a solid sorbent material. Isoflurane (1-chloro-2,2,2-trifluoroethyl-difluoromethyl-ether), an inhaled anaesthetic used widely in surgery, and styrene, used in boat construction and the manufacture of fibreglass-reinforced plastics, are partially eliminated from the body in exhaled breath, samples of which can therefore be used to monitor biological exposure to these two organic compounds. Recoveries were tested in controlled atmospheres of isoflurane or styrene, with Chromosorb 106 or Tenax, respectively, as the adsorbent. We also investigated the influence of relative humidity, an important factor in breath sampling, on adsorption.

Biological monitoring of occupational exposure to n-hexane by exhaled air analysis and urinalysis.

To compare two methods of biological monitoring for the evaluation of risk of occupational exposure to n-hexane, we analyze the relationship between environmental exposure to this solvent and urinary excretion of 2,5-hexanedione and n-hexane in exhaled air in 69 workers employed in the shoe industry. Environmental exposure to the solvent was monitored with personal diffusive samplers, which were desorbed with carbon sulfide and analyzed by gas chromatography. To measure 2,5-hexanedione, urine was subjected to acid hydrolysis, separation in octadecyl silane columns, elution with 5% aqueous acetonitrile solution and extraction with dichloromethane, followed by gas chromatography. In exhaled air, n-hexane was measured with a sampling system that permitted concentration of aliquots of end-exhaled air (alveolar air) from one or more exhalations in a tube packed with activated charcoal, which was then desorbed with carbon sulfide and analyzed by gas chromatography. Concentrations of n-hexane in breathing zone air were significantly correlated with urinary concentrations of 2,5-hexanedione (r = 0.88) and with exhaled air n-hexane (r = 0.86); in addition, the two biological indicators correlated significantly (r = 0.70). Analyses in both exhaled air and urine were thus considered useful for biological monitoring of the risk of exposure to n-hexane.

Design and evaluation of an exhaled breath sampler for biological monitoring of organic solvents.

We designed a breath sampler based on a tube which collects the final portion of exhaled air. The passage of successive fractions through a layer of activated charcoal is controlled by a three-way valve. This system was validated in a controlled atmosphere of n-hexane and toluene at four concentrations between 12 and 110 mg m-3 and 12 and 115 mg m-3, respectively. Uptake volumes of 0.1, 0.2 and 0.31 were tested at relative humidities of 46% and 98%. There were no significant differences in the recoveries obtained under any of the conditions tested. We confirmed the reproducibility between successive samples in volunteers and exposed workers, and found no significant differences between the different sampling conditions studied. Our system enriches the sample in an adsorbent cartridge by collecting successive fractions of end-exhaled breath from one or more exhalations until the amount required by the analytical method has been accumulated. It is portable, economical and highly operative in the field.