Methyltetrahydrophthalic anhydride in air--sampling and analysis.

Methyltetrahydrophthalic anhydride (MTHPA), an organic anhydride, is a sensitizing agent even at low air concentrations: no methods for its sampling and analysis have previously been reported. This paper outlines the use of Amberlite XAD-2 for sampling MTHPA vapour in air, followed by analysis using gas chromatography with flame ionization detection. The level of detection corresponds to a concentration in air of 10 micrograms m-3 for a 20 l. sampling volume. Up to 200 l. air has been sampled, at a sampling rate of 1 l. min-1, without detectable losses. The adsorption efficiency and the stability of the anhydride in the XAD-2 tubes were not influenced by a relative air humidity (RH) of 40%, but at RH 80% there was a loss of 18% at 50 l. air-sample volume. Results from sampling in XAD-2 tubes were 8% lower than those from parallel sampling in midget bubblers containing 10 ml 0.01 M sodium hydroxide.     

Laboratory evaluation of stain-length passive dosimeters for monitoring of vinyl chloride and ethylene oxide

The effects of vapor concentration in the range of 1.2 to 5.1 ppm (vinyl chloride) and 8.3 to 29.1 ppm (ethylene oxide) on the response of new stain-length passive dosimeters were evaluated separately in a dynamic exposure chamber. The vinyl chloride dosimeter was prepared with a permanganate impregnated blend of Chromosorb W and silica gel, while a silica gel-coated plastic strip (TLC plate) impregnated with dichromate was used to detect ethylene oxide. The use of a TLC plate as the inert support allowed us to reduce the amount of reagent loaded per length of tube, thus significantly enhancing in the sensitivity of the unit, which was necessary for accurately detecting ethylene oxide at these low concentrations. At the vinyl chloride exposure of 8 ppm-hrs the length of stain was 0.76 cm and the 95% confidence interval about this point was +/- 1.4 ppm-hrs (18%). For the ethylene oxide dosimeter the length of stain at the exposure of 80 ppm-hrs was 0.90 cm and the 95% confidence interval about this point was +/- 16 ppm-hrs (20%). Although some shortening of the stain was noted at low relative humidity (26%) in the vinyl chloride device, no effect on the dosimeter response was observed over the range of relative humidity of 35 to 96%. The ethylene oxide dosimeter response was not affected by relative humidity in the range of 28 to 90%. The use of a TLC plate as the inert support of the colorimetric reagent has proven to be an excellent means of improving the sensitivity of these stain-length passive dosimeters.(ABSTRACT TRUNCATED AT 250 WORDS)     

被动式有机蒸气采样器的研制

此采样器,可采集空气中六种有机蒸气,它无采样泵。体积小,重量轻,既可采集个体在接触时间内的累积量也可采集定点样品。采样后取出采样介质,加二硫化碳解吸,用气相色谱法测定。对准确度、精密度、吸附容量、样品储存期、风速影响、湿度影响及干扰等进行了实验观察。六种蒸气全过程的准确度为±7.7～±13.6%,符合NIOSH的推荐标准。合并变异系数为 2.7～5.3%。文中还报告了现场测定结果。     

Stain length passive dosimeter for monitoring of carbon monoxide

A new passive dosimeter for the personal monitoring of carbon monoxide exposure in the workplace has been developed. This new type of sampling device does not require follow-up analysis of the collected sample to determine the exposure. Rather, the time-weighted average concentration is determined directly from the length of a colored stain which is produced instantaneously during the exposure period in a specially prepared indicator tube. The colored stain length is a function of both contaminant concentration and exposure time. The effects of carbon monoxide concentration in the range of 0.5 T TLV to 2.0 X TLV on the response of the dosimeter were evaluated in a dynamic exposure chamber. In this range of concentration, plots of stain length against exposure collapsed onto a single curve. At the TLV exposure the stain length was 2.1 cm and the 95% confidence interval about this point was +/- 17%. Relative humidity in the range of 26 to 92% and face velocity in the range of 0.01 to 1.0 m/s (2 to 200 fpm) did not significantly affect the dosimeter response. These data were fitted to the appropriate model equation with a correlation coefficient of 0.968. By eliminating the need for follow-up analysis, this stain length dosimeter significantly reduces the cost of monitoring. The instantaneous readout eliminates the delay between exposure and quantification, enabling more careful control of the workplace environment.     

Determining the 222Rn exhalation rate of building materials using liquid scintillation counting

A new method for determining the free 222Rn exhalation rate from building materials is described. The sample is enclosed in a container from which the exhaled Rn is continuously purged by nitrogen gas. After 2-3 h, when the Rn level in the container has reached a steady-state concentration, the outflowing Rn is trapped on silica gel at about -190 degrees C. About 16 h after sampling, the silica gel is analyzed by liquid scintillation counting to determine the area exhalation rate. The method described has a good repeatability and reproducibility with coefficients of variation of 7.8% and 8.3%, respectively, at 5 Bq m-2 h-1. The low limit of detection of 11 mBq 222Rn offers the opportunity to quantify the exhalation rate of almost all kinds of building materials. It was found that the air humidity strongly influences the exhalation rates of building material and, therefore, should be controlled. Two typical building materials were investigated. For gypsum, an increase in the exhalation rate with increasing water vapor pressure was found, whereas for concrete, a linear decrease with increasing water vapor pressure was observed. The 222Rn area exhalation rates of 20 Dutch building materials, including some experimental ones, were determined at 50% RH, 20 degrees C, showing a range of less than 0.02-15.8 Bq m-2 h-1. The lowest values were found for natural gypsum board, the highest for phosphogypsum blocks. Building materials containing fly ash gave area exhalation rates comparable to those of similar materials without fly ash.     

An integrating thermoluminescent Rn daughter personal dosimeter

An integrating Rn daughter dosimeter using conventional Dy-doped CaSO4 thermoluminescent (TL) material has been developed for use as a personal monitor. The dosimeter was found to have a linear response over the range 0.5 WL-h to 25 WL-h and to be insensitive to the state of equilibrium of the Rn daughters. The use of the dosimeter to monitor both 222Rn and 220Rn daughters is described. The limiting sensitivity of the dosimeter, at a sampling rate of 1 L min-1, was determined to be 0.1 WL-h for 222Rn daughters and 0.5 WL-h for 220Rn daughters. The application of the thermoluminescent dosimeter (TLD) to occupational monitoring of 222Rn and 220Rn daughters is discussed.     

相对湿度对光散射法测定大气细颗粒物浓度的影响

目的探讨相对湿度对光散射法测定大气细颗粒物(PM2.5)浓度的影响。方法在2010年冬季和2011年夏季分别用光散射法和滤膜称重法对大气PM2.5浓度进行24d平行测定,同时收集采样期间的相对湿度数据,分析比较不同相对湿度对光散射法测定大气PM2.5浓度的影响。结果采样时期光散射法测定结果与滤膜称重法结果呈统计学相关(r=0.948,P<0.001),但是两种测定方法结果的一致性随着相对湿度的变化而改变。相对湿度<50%时,两种方法的测定结果差异无统计学意义(P=0.114);相对湿度>50%时,光散射法测定结果与滤膜称重法结果差异有统计学意义(P=0.001),且两种方法的测定结果比值与相对湿度呈正相关(r=0.894,P<0.001)。结论相对湿度>50%会对光散射法测定大气PM2.5的准确性造成影响,因此在采用光散射法测定大气PM2.5浓度时应考虑采样期间相对湿度的影响。     

Determination of methyltetrahydrophthalic anhydride in air using gas chromatography with electron-capture detection.

Methyltetrahydrophthalic anhydride (MTHPA) stimulates the production of specific IgE antibodies which can cause occupational allergy even at extremely low levels of exposure (15-22 micrograms/m3). Safe use in industry demands control of the levels of exposure causing allergic diseases. Thus, the air monitoring of MTHPA is very important, and sensitive methods are required to measure low air concentrations or short-time peak exposures. This paper outlines the use of silica-gel tubes for sampling airborne MTHPA vapour, followed by analysis using gas chromatography with electron-capture detection. No breakthrough was observed at 113, 217, 673 and 830 micrograms/m3 (sampling volume 30, 60, 60 and 20 l, respectively; relative humidity 40-55%). Concentrations > 1.0 microgram/m3 could be quantified at 20-min sampling with a sampling rate of 1 l/min. The present method can also be applied to measurements of exposure to hexahydrophthalic and methylhexahydrophthalic anhydride. The risk of MTHPA exposure in two condenser plants was also assessed by determining MTHPA levels in air of the workplace. In conclusion, our method was found to be reliable and sensitive, and can be applied to the evaluation of MTHPA exposure.     

扩散法被动式氟化氢个体监测器的研制

本工作研制了基于分子扩散法的被动式ＨＦ个体采样器，采样速度１１０ｍｌ／ｍｉｎ，相对标准差９％。考察了环境条件对采样速率的影响，结果表明：在室温（１０～３５℃）、风速１０～１５０ｃｍ／ｓ、相对湿度１０％～８０％条件下使用，采样速率基本不变。与ＩＳＯ标准方法现场对比测定，总不确定度±１９％，可适用于室内空气污染和个体接触量监测。     

Electrostatic effects in asbestos sampling. I: Experimental measurements

Electrostatic charge can cause errors during sampling of airborne asbestos fibers and other particles. The change in particle trajectories caused by charge effects during sampling can result in nonuniform deposits on the collecting filter surface and net loss of sample. The degree of these electrostatic effects depends on particle charge, sampler charge, sampler conductivity, and sampling flow rate and direction. The purpose of this research was to evaluate the dependence of sampling efficiency and sample uniformity on these variables. Humidity has been postulated as a primary determinant of particle charge during aerosol generation. Measurements of particle charge and concentration were made as a function of relative humidity with chrysotile fibers generated from a fluidized bed. A strong increase in charge and a decrease in concentration of fibers was noted as the relative humidity was decreased below 15%. The effects of conductive versus nonconductive samplers and sampling flow rate were measured as a function of particle and sampler charge levels. Nonconductive samplers can carry a large and variable charge distribution on their surfaces. This can result in a biased and highly variable particle deposit on the filter when sampling charged particles. Conductive cowls spread any acquired charge over the entire surface and produce a more symmetrical and less biased charged particle deposit. Increasing the sampling flow rate will improve sampling efficiency and decrease deposit variability because the charged particle has less time to interact with the field produced by the sampler. These results suggest that sampling problems caused by electrostatic charge interactions are most likely to occur under low humidity conditions of dust generation, that sampling should be done at as high a flow rate as possible to reduce these effects, and that analysts should select fields toward the center of the filter to minimize bias and variability.     

House dust collection efficiency of the high volume small surface sampler on worn carpets

The High Volume Small Surface Sampler (HVS3) is a dust-sampling vacuum that allows for set airflow and back pressure during sampling, increasing precision. Total dust collection efficiency of the HVS3 has been evaluated only on new carpets-not worn carpets. We performed a factorial study to assess the impact of carpet wear, dust deposition level, carpet type, and relative humidity during sampling on HVS3 collection efficiency. House dust was aerosolized in a 1-m3 exposure chamber and allowed to settle on test carpets and reference filters. Dust was embedded into the carpets and later extracted with the HVS3 under controlled environmental conditions according to established protocols. Overall collection efficiency was high, 88.3%. Collection efficiency was significantly higher at low relative humidity levels (30%) relative to high (75%) (p = < 0.0001), though differentially between cut-pile and closed-loop carpets. Collection efficiency of carpets with high wear was significantly lower than those with midlevel wear (p = 0.01). These results demonstrate that the design of the HVS3 partially corrects for differences in dust load and carpet type. However, collection efficiency of the HVS3 is affected by high levels of carpet wear and ambient humidity during sampling.     

Correcting diacetyl concentrations from air samples collected with NIOSH method 2557

Diacetyl (2,3-butanedione), a diketone chemical used to impart a buttery taste in many flavoring mixtures, has been associated with bronchiolitis obliterans in several industrial settings. For workplace evaluations in 2000-2006, National Institute for Occupational Safety and Health (NIOSH) investigators used NIOSH Method 2557, a sampling and analytical method for airborne diacetyl utilizing carbon molecular sieve sorbent tubes. The method was subsequently suspected to progressively underestimate diacetyl concentrations with increasing sampling site humidity. Since underestimation of worker exposure may lead to overestimation of respiratory health risk in quantitative exposure-effect analyses, correction of the diacetyl concentrations previously reported with Method 2557 is essential. We studied the effects of humidity and sample storage duration on recovery of diacetyl from experimental air samples taken from a dynamically generated controlled test atmosphere that allowed control of diacetyl concentration, temperature, relative humidity, sampling duration, and sampling flow rate. Samples were analyzed with Method 2557, and results were compared with theoretical test atmosphere diacetyl concentration. After fitting nonlinear models to the experimental data, we found that absolute humidity, diacetyl concentration, and days of sample storage prior to extraction affected diacetyl recovery as did sampling flow rate to a much smaller extent. We derived a mathematical correction procedure to more accurately estimate historical workplace diacetyl concentration based on laboratory-reported concentrations of diacetyl using Method 2557, and sample site temperature and relative humidity (to calculate absolute humidity), as well as days of sample storage prior to extraction in the laboratory. With this correction procedure, quantitative risk assessment for diacetyl can proceed using corrected exposure levels for air samples previously collected and analyzed using NIOSH Method 2557 for airborne diacetyl.     

Wind velocity effects on sampling rate of NO2 badge.

The effects of wind velocity on a sampling rate of a nitrogen dioxide (NO2) diffusive badge were experimentally determined using a turntable. The use of a turntable permits the collection of the large amounts of data that are needed for statistically reliable results at several wind velocities in one experiment. The regression model for the wind effect determined by these experiments was closely correlated with data previously gathered from experiments using wind tunnels. Experiments at two different relative humidities, 35% and 60%, were performed and analyzed by a simple least square regression model. A multi-regression model containing two independent variables, wind velocity and relative humidity, also was developed. The multi-regression model was useful at relative humidity between 20% and 60% and wind velocity between 0 and 7 meter per second (m/sec).     

Explanation of pressure effects on a nitrogen dioxide (NO2) sampler

When nitrogen dioxide (NO2) samplers were exposed at several reduced pressures, it was found that the sampling rate was correspondingly decreased; that finding did not agree with accepted diffusional theory. When the experiments were repeated using water vapor as the gas and molecular sieve as the sorbent, the observed sampling rates were in very good agreement with diffusional theory. These findings demonstrated that the pressure effect was not common to all diffusional samplers and suggested that there might be an alternate explanation for the results with NO2-triethanolamine (TEA). The best possibility appeared to be the dehydration of TEA that takes place at reduced pressures. That this is a very significant factor was demonstrated by simultaneous exposure to identical concentrations of NO2 at 1 atm and 50% or 0% relative humidity. In dry air the sampling rate was equivalent to that found previously at about 1/10 atm. The earlier results can be satisfactorily explained as indirect rather than direct effects of reduced pressure.     

A thermoluminescent dosimetry intercomparison in operational power station fields.

A dosimetry intercomparison was held among the five agencies in Canada that are recognized by the Atomic Energy Control Board as competent to perform external dosimetry. Exposures of thermoluminescent dosimeter badges were made under operational conditions to radiation fields in Candu nuclear generating stations. Details of the method are described including the large, block-type phantoms (with a rotating front face so that all badges were equally exposed) and a small device to measure the depth-dose distribution. Thirty-six exposures (or "runs") were made, exposing 522 badges for periods of 1 h-2 d. Normalization between the runs was based on the absorbed dose at 1,000 mg cm-2 for each run, as measured by the depth-dose device. Using this method, the average relative readings for the five participants ranged from 1.01-1.40 (dimensionless).     

天平室温度和湿度的变化对测尘滤膜称量结果的影响

目的 研究称量环境温度和湿度的变化对采样前后滤膜称量结果的影响.方法 在(18±1)℃和(28±1)℃2个温度下,调节天平室的湿度,于不同气象条件下对采集煤尘前后的测尘滤膜进行称量,计算采样后承载滤膜的增量(相同称量气象条件下的承载滤膜质量减去相对应的空白滤膜的质量),对结果进行比较分析.结果 空白滤膜和承载滤膜在(18±1)℃和(28±1)℃的称量结果波动范围分别为0.10～0.13 mg和0.06～0.09 mg,温度和湿度均变化时,称量结果波动范围为0.12～0.16 mg;各组承载滤膜增量均值在(18±1)℃和(28±1)℃的波动范围分别为0.07～0.10 mg和0.04～0.08 mg,温度和湿度均变化时,波动范围为0.09～0.14 mg.同一温度组内,空白滤膜组和承载滤膜组的称量均值随着湿度升高呈上升趋势,而各承载滤膜的增量与湿度不相关;在相同湿度下,(18±1)℃时承载滤膜增量高于(28±1)℃,差异有统计学意义(P＜0.01);除总尘高增量组外,其余各组称量均值在(18±1)℃随湿度升高的上升趋势比(28±1)℃更明显,差异有统计学意义(P＜0.01).当湿度相同时,各承载滤膜组(18±1)℃的增量均值高于(28±1)℃,差异有统计学意义(P＜0.01).结论 实验室温度和湿度的变化导致测尘滤膜称量结果的波动,湿度对采样前后滤膜增量影响不明显,但低温时滤膜增量高于高温时,会影响粉尘浓度测定结果.     

Glycol ethers--validation procedures for tube/pump and dosimeter monitoring methods

Methods were developed and validated for personal monitoring of exposures to airborne glycol ethers, both short-term and long-term time-weighted-averages. Either a 600 mg charcoal tube or a 780 mg silica gel tube is recommended for monitoring nine glycol ethers, depending upon the humidity and other organic compounds to be monitored. The charcoal tube allows maximum sensitivity and is unaffected by high humidity conditions. Two-phase solvent desorption with CS2 and water allows aqueous phase recoveries of DOWANOL EM, PM, EE, DM, DPM, and TM glycol ethers. DOWANOL EB, DB and TPM glycol ethers are partitioned between the two layers, necessitating chromatographic analysis of both layers. The silica gel tube method can be used to monitor all nine glycol ethers tested, but is affected by high humidity conditions, resulting in significant breakthrough of the more volatile glycol ethers. The 3M organic vapor monitor can accurately and conveniently determine exposure concentrations for DOWANOL EM, EE, and PM glycol ethers, but sensitivities may be inadequate for sampling periods less than one hour. These methods were validated at levels down to 0.1 times the Dow internal exposure guidelines for those substances with Dow exposure guidelines and well above the current ACGIH and OSHA guidelines. This paper also illustrates validation procedures for tube/pump and dosimeter methods, allowing good definition of method accuracy and precision. Some screening experiments are described for diffusional dosimeters to check the most important parameters in a minimum of time. This methodology will allow assessment of human airborne exposures relative to the new toxicology data available on animals.     

The development and evaluation of a thermally-desorbable miniature passive dosimeter for the monitoring of organic vapors

A thermally desorbable passive dosimeter for organic vapors has been developed in conformity with theoretical and practical aspects of passive dosimeter design. The device was optimized for low sample loadings which result from short-term and/or low concentration level exposure. Laboratory evaluation of this device for factors critical to the performance of passive dosimeters included the following: desorption efficiency, capacity, sensitivity, accuracy and precision, concentration level, environmental conditions (e.g., air face velocity, relative humidity) and sample stability during short and long periods of time. This device has been shown to operate in accordance with theoretically predicted performance and should be adequate for short-term exposure limits and/or low concentration monitoring of organic vapors in the workplace.     

低浓度挥发性有机化合物被动式个体采样器的研究

研制了扩散式挥发性有机化合物（ＶＯＣｓ）个体采样器,适用于对环境空气中和非职业性个体接触ＶＯＣｓ的监测。在风速１０～２６０ｃｍ／ｓ,相对湿度为３０％～８０％,温度为１０～３０℃的范围内使用,采样速率分别为苯：２５．７４ｍｌ／ｍｉｎ,甲苯：２５．１６ｍｌ／ｍｉｎ,四氯乙烯：２５．８５ｍｌ／ｍｉｎ,对－二甲苯：８．１６ｍｌ／ｍｉｎ,苯乙烯：６．４７ｍｌ／ｍｉｎ。与主动式活性炭纤维（ＡＣＦ）管采样法比较,本个体采样器测定空气中靶ＶＯＣｓ的总不确定度均在±２５％以内。     

Evaluation of the GMD systems, Inc., thermally-desorbable diffusional dosimeter for monitoring methyl chloride

The GMD Systems, Inc., thermally-desorbable diffusional dosimeter using Anasorb GM solid sorbent was evaluated for monitoring methyl chloride (CH3Cl) in the workplace. The effects of CH3Cl concentration; dosimeter exposure time; relative humidity, temperature, and face velocity during exposure; excursion exposure behavior; and storage temperature and duration after collection were investigated. Only extremely low face velocities (0.020 m/sec) and storage periods of over 8 days at room temperature or of around 30 days at reduced (refrigerator or freezer) temperatures caused sample degradation. Side-by-side measurements of CH3Cl using the diffusional monitor and a validated charcoal tube method under field conditions yielded statistically indistinguishable results. This diffusional monitor used in combination with Anasorb GM solid sorbent is a satisfactory means of determining CH3Cl exposures in the workplace.