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.     

A solid sorbent air sampling and analytical procedure for methyl-, dimethyl-, ethyl-, and diethylamine

A sampling and analytical procedure for methyl-, dimethyl-, ethyl-, and diethylamine was developed in order to avoid problems typically encountered in the sampling and analysis of low molecular weight aliphatic amines. Samples are collected with adsorbent tubes containing Amberlite XAD-7 resin coated with the derivatizing reagent, NBD chloride (7-chloro-4-nitrobenzo-2-oxa-1,3-diazole). Analysis is performed by high performance liquid chromatography with the use of a fluorescence and/or UV/visible detector. All four amines can be monitored simultaneously, and neither collection nor storage is affected by humidity. Samples are stable at room temperature for at least two weeks. The methodology has been tested for each of the four amines at sample loadings equivalent to air concentration ranges of 0.5 to 30 ppm for a sample volume of 10 liters. The method shows promise for determining other airborne primary and secondary low molecular weight aliphatic amines.     

Methyltetrahydrophthalic acid in urine as an indicator of occupational exposure to methyltetrahydrophthalic anhydride

Objective: To investigate whether methyltetrahydrophthalic acid (MTHP acid) in urine can be used as a biomarker for exposure to methyltetrahydrophthalic anhydride (MTHPA). Methods: Workers occupationally exposed to MTHPA were studied in combination with one of the authors, who was experimentally exposed to MTHPA. Air levels of MTHPA were determined by personal sampling in the breathing zone. The MTHPA in air was sampled by silica gel and analyzed by gas chromatography (GC) with electron-capture detection. Urinary levels of MTHP acid, a metabolite of MTHPA, were determined in 15 subjects in total. Urine was collected from 14 workers immediately before the start of the work shift and then after 4 and 8 h, and from one of the authors at intervals during 24 h. MTHP acid in urine was analyzed by GC with mass spectrometric detection. Results: The time-weighted average (TWA) air levels ranged from 1.0 g to 200 g MTHPA/m³ during 8 h work shifts. The urinary levels of MTHP acid increased during exposure and decayed after the end of exposure, with an estimated half-time of about 3 h. A close correlation was found between the TWA air levels of MTHPA and creatinine-adjusted MTHP acid levels in urine collected at the end of the shift (r=0.955; P<0.0001). The current occupational exposure limit of 50 g MTHPA/m³ (Japan Society for Occupational Health) corresponded to about 1300 g MTHP acid/g creatinine, which was equivalent to about 900 nmol/mmol creatinine in the International System of Units (SI). Conclusions: These results indicate that the determination of MTHP acid in urine is suitable for use in the biological monitoring of MTHPA exposure.     

Risk factors for sensitisation to methyltetrahydrophthalic anhydride.

OBJECTIVES: To examine an association between specific IgE to methyltetrahydrophthalic anhydride (MTHPA) and exposure time, atopic history, smoking habits, and total IgE concentrations. METHODS: A cross sectional survey was carried out on a population of 148 workers from two condenser plants using epoxy resin with MTHPA, an acid anhydride curing agent known to cause allergy. RESULTS: Using a Pharmacia CAP system with a MTHPA human serum albumin conjugate, specific IgE antibody was detected in serum from 97 (66%) out of the 148 workers exposed to MTHPA. Stepwise multiple linear regression analysis showed a striking relation between log concentrations of specific and total IgE (P < 0.0001). Furthermore, when the workers were divided into two groups according to a cut-off point (100 IU/ml) between low and high total IgE, current smoking was significantly (P = 0.025) associated with specific IgE production only in the group with low total IgE (< 100 IU/ml). CONCLUSIONS: Smoking is the most significant risk factor for raising specific IgE to MTHPA in the group with low total IgE concentrations.     

Collection and ion chromatographic determination of ammonia and methylamines in air

A method is described for the collection of ammonia (NH3), monomethylamine (MMA), dimethylamine (DMA), and trimethylamine (TMA) from air and their subsequent determination by ion chromatography. Samples are collected with 800-mg silica gel sampling tubes at a flow rate of 1 L/min for 10 minutes or at 100 mL/min for up to 7.5 hours. Samples collected with sulfuric acid-treated tubes can be stored at room temperature for at least 21 days with no loss in recovery. Untreated samples can be stored in a refrigerator up to 32 days. The method has been validated from 2 to 50 ppm v/v when a 10 L air sample is taken. No loss in recovery was observed when sampling up to 23 L of air at 100% relative humidity. The recovery and total precision (95% confidence level) for NH3, MMA, DMA, and TMA were 91 +/- 12.5%, 93 +/- 10.3%, 92 +/- 9.6% and 84 +/- 17.6%, respectively.     

Detection and clinical relevance of a type I allergy with occupational exposure to hexahydrophthalic anhydride and methyltetrahydrophthalic anhydride

Summary Hexahydrophthalic anhydride (HHPA) and methyltetrahydrophthalic anhydride (MTHPA) belong to the group of the acid anhydrides and, among other applications, are used in the production of epoxy resins. These substances are known as potent low-molecular allergens and induce predominantly type I allergies according to Coombs and Gell. We examined 110 employees exposed to HHPA and MTHPA. With all of them a RAST was carried out with the commercially available conjugates of phthalic anhydride (PA) and a skin prick test with 1% and 5% acetonic solutions of PA. In 109 of these sera a radio allergo sorbent test (RAST) was carried out with the not commercially available conjugates of HHPA and of MTHPA. With complaints connected with the workplace the working materials used (HHPA, MTHPA) were also checked by means of the skin prick test. With at least one positive immunological finding (in the RAST and/or skin prick test) in connection with complaints at the workplace, we performed a workplace-related inhalation test under experimental conditions. Specific IgE against acid anhydrides was detected in a total of 17 (15.4%) persons. In the challenge test, six (5.4%) sensitisations were shown to be clinically relevant. On inclusion of borderline positive findings with PA conjugates the RAST produced three false negative and one false positive finding compared with a RAST with HHPA and MTHPA conjugates. With the conjugates of trimellitic anhydride, in no case could specific IgE be detected. The skin prick test led, in comparison with the RAST, to three false positive and three false negative findings. With all clinically relevant sensitisations the skin prick test was regarded as positive. RASTs with conjugates of PA and skin prick tests with native acid anhydrides can, according to our investigations, validly ascertain workplace-related sensitisations to HHPA and MTHPA.     

Methods for sampling and determining chlorotrifluoroethylene (CTFE) in air

Two new methods for sampling and analysis of chlorotrifluoroethylene (CTFE) exceeding 1 ppm (4.8 mg/m3) time-weighted-average concentrations were developed and compared. The first involved collecting air in bags followed by gas chromatographic (GC) analysis of sample aliquots using flame ionization detection (FID). Using specified procedural details, analyte recoveries of greater than 90% were demonstrated even for samples stored for five days. A second method used charcoal to adsorb and concentrate analyte from 10-L air samples. Toluene was used to desorb CTFE which was quantitated by GC/FID. Desorption efficiencies were greater than 90%. Analyte recoveries of greater than 90% were obtained from charcoal tubes which had been used to sample air containing 10 ppm of CTFE and were stored for two weeks at 4 degrees C. Recoveries from five field spikes (3 to 20 ppm) averaged 94%. Using dry air containing 800 ppm CTFE, no significant breakthrough of a 400 mg sorbent bed was observed. After comparing the advantages and disadvantages of each method, the charcoal procedure was recommended.     

工作场所空气中正丙醇测定方法研究

目的 研究并建立适用于工作场所空气中正丙醇的定量检测方法。
方法 工作场所空气中正丙醇由活性炭管采集, 经体积比为1:100的异丙醇-二硫化碳混合溶剂解吸后, 经石英弹性毛细管柱HP-INNOWAX (30.0 m×0.53 mm×1.0μm)分离, 氢焰离子化检测器检测, 标准曲线法定量。
结果 正丙醇浓度在10~500 μg/mL范围内和峰面积呈线性关系, 回归方程y=2.12 x+1.96, 相关系数r=0.999 9(P < 0.05)。以3.0 L采样量计, 方法最低检出浓度0.09 mg/m3, 最低定量浓度0.30 mg/m3; 不同浓度加标样品测定结果的相对标准偏差为1.7%~3.6%, 解吸效率89.3%~94.7%, 采样效率> 96%, 100 mg活性炭对正丙醇的穿透容量为16 mg; 采样后的活性炭管在室温条件下至少可放置7 d。
结论 建立的工作场所空气中正丙醇溶剂解吸-气相色谱测定方法准确可靠、灵敏度高、稳定性良好, 适用于工作场所空气中正丙醇的现场检测。
     

测定工作场所空气中二氧化硫的离子色谱法

目的建立在线超滤-离子色谱法测定工作场所空气中SO2。方法用装有10.0 ml浓度为5.73 g/L的过氧化氢溶液的多孔玻板吸收管采集工作场所空气中的SO2,吸收液直接通过在线超滤系统自动过滤后经Metrosep A Supp 5阴离柱分离,电导检测器检测,以SO2氧化后生成的硫酸根保留时间定性,峰面积定量。按照《职业卫生标准制定指南第4部分工作场所空气中化学物质测定方法》的要求进行试验。结果硫酸根的浓度在2～25μg/ml内线性关系良好,回归方程为Y=39.34 X-17.72,相关系数r为0.999 3。方法的检出限以硫酸根记为9.6 ng,以SO2记为6.4 ng（进样量20μl）,以采样体积为7.5 L计算该方法对空气中SO2的最低检出浓度为0.43 mg/m＾3。方法的重现性好,不同浓度的相对标准偏差为0.16%～1.87%;方法的平均采样效率为（99.24±0.21）%;穿透容量≥2.90 m;方法能准确地检测SO2标准气的浓度;样品至少在4℃可保存7d。结论该方法快速、灵敏和准确,各项指标均达到指南的要求。     

Determination of total sulfur compounds and benzothiazole in asphalt fume samples by gas chromatography with sulfur chemiluminescence detection

As part of a collaborative project between the National Institute for Occupational Safety and Health and the Federal Highway Administration to evaluate asphalt pavers' exposures to asphalt fume and their potential health effects, a method was developed for the determination of total sulfur compounds and benzothiazole in asphalt fume samples. Asphalt fume samples were collected from asphalt mixtures with and without the addition of ground-up rubber tires. The asphalt fume samples were collected with sampling trains that consisted of a Teflon membrane filter and an XAD-2 adsorbent tube. Filter and sampling tube media were extracted with hexane and subsequently analyzed by gas chromatography with a sulfur chemiluminescence detector. Separation was achieved with a 100 percent dimethyl polysiloxane fused silica column. Typical calibration curves had linear correlation coefficients of 0.99 or better with a relative standard deviation (RSD) of 5 percent. Benzothiazole desorption efficiency (DE) determined using spiked sampling tubes ranged from 96.5 percent at 5.0 micrograms to 89.4 percent at 40 micrograms with RSD values from 0.9 to 4.0 percent. Benzothiazole storage recovery determined using sampling tubes spiked at 20 micrograms and refrigerated for 30 days at 4 degrees C was 89.8 percent when corrected for the DE with an RSD of 1.1 percent. The limit of detection for the method determined using spiked sampling tubes was 0.30 microgram. Quantitation for total sulfur compounds and benzothiazole was against benzothiazole standards in hexane. Because of detector selectivity, sample preparation consisted of a simple hexane extraction even when samples had a high background due to hydrocarbon overload. Detector sensitivity provided quantitation in the sub-microgram region. Because of the sample preparation step and because benzothiazole was determined during the same analysis run, this method is straightforward and analytically efficient. The method has been used to analyze asphalt fume samples collected at several asphalt paving and roof operations.     

测定工作场所空气中丙烯酸的离子色谱法

目的建立在线超滤-离子色谱法测定工作场所空气中丙烯酸。方法空气样品用硅胶管采集,1.0 mmol/L Na HCO3＋3.2 mmol/L Na2CO3淋洗液解吸,解吸液通过在线超滤系统自动过滤后进样分析,经Metrosep A Supp 5阴离柱分离,电导检测器检测,以保留时间定性,峰面积定量。按照《职业卫生标准制定指南第4部分工作场所空气中化学物质测定方法》的要求进行试验。结果丙烯酸在0.52-7.78μg/ml浓度范围内线性良好;相关系数为0.999 6;检出限为0.048μg/ml（进样量20μl）,以采样体积为7.5 L计算该方法的最低检出浓度为0.16 mg/m^3;方法的重现性好,不同浓度的相对标准偏差为0.55%-2.20%;平均解吸效率为99.10%±1.53%;方法的模拟样品的加标回收率为96.11%-101.11%。结论该方法快速、灵敏和准确,各项指标均达到《职业卫生标准制定指南第4部分工作场所空气中化学物质测定方法》的要求。     

Exposure assessment and sensitisation in workers exposed to organic acid anhydrides

Objectives: To clarify whether the intensity of exposure to organic acid anhydrides (OAAs) is associated with the risk of sensitisation to these allergens. Methods: The investigations were carried out in three different manufacturing plants (A, B, and C) where OAAs were used in the production of epoxy resins. Methyltetrahydrophthalic acid anhydride (MTHPA) was used in all three plants. The exposure assessment included stationary and ambient air monitoring (OAAs in the air) and biological monitoring (metabolites in urine). In plant A 20, in plant B 86 and in plant C 113 employees were examined by a physician (anamnesis, skin-prick test, specific IgE, spirometry). In plants B and C, the exposure areas were classified as high, medium, and low, without the results of the exposure assessment being known. Results: The ambient air concentrations (in μg/m³) of MTHPA were 37.2 and 58.5 in plant A (number of samples n=2), ranged from <0.5–26.2 in plant B (n=5) and from 2.1–57.9 in plant C (n=3) with stationary air collecting, and from 8–45 (n=6), from <4.7–35.7 (n=3) and from 2–37.8 (n=3) with personal air collection. The metabolites of OAAs in urine (in nmol/mmol creatinine) ranged from 5.7–645 (median of MTHPA: 346) in plant A, from <1–213 (median of MTHPA: 10.1) in plant B and from 0.1–830 (median of the sum of the OOA metabolites: 108.6) in plant C. The prevalence of sensitisation was 35% in plant A, 21% in plant B and 29% in plant C. A higher prevalence in the highly exposed areas, however, could not be seen. Levels of IgE specific for conjugates of MTHPA were not associated with the metabolites in the end of shift urine. Levels of IgG specific for conjugates of MTHPA, however, were associated with the metabolites in the end of shift urine. Conclusions: The data showed that biological monitoring is a useful tool in the exposure assessment of OAAs. Comparing the prevalence of sensitisation and the results of biological monitoring, between the three plants, we found that sensitisation increased with increasing exposure. Within a plant a higher risk of sensitisation in persons working in highly exposed areas at the time of the examination could not be seen, possibly due to frequent job rotation. Received: 2 August 1999 / Accepted: 29 January 2000     

Occupational dimethylformamide exposure

A diffusive sampling method with water as absorbent was examined in comparison with 3 conventional methods of diffusive sampling with carbon cloth as absorbent, pumping through National Institute of Occupational Safety and Health (NIOSH) charcoal tubes, and pumping through NIOSH silica gel tubes to measure time-weighted average concentration of dimethylformamide (DMF). DMF vapors of constant concentrations at 3-110 ppm were generated by bubbling air at constant velocities through liquid DMF followed by dilution with fresh air. Both types of diffusive samplers could either absorb or adsorb DMF in proportion to time (0.25-8 h) and concentration (3-58 ppm), except that the DMF adsorbed was below the measurable amount when carbon cloth samplers were exposed at 3 ppm for less than 1 h. When both diffusive samplers were loaded with DMF and kept in fresh air, the DMF in water samplers stayed unchanged for at least for 12 h. The DMF in carbon cloth samplers showed a decay with a half-time of 14.3 h. When the carbon cloth was taken out immediately after termination of DMF exposure, wrapped in aluminum foil, and kept refrigerated, however, there was no measurable decrease in DMF for at least 3 weeks. When the air was drawn at 0.2 l/min, a breakthrough of the silica gel tube took place at about 4,000 ppm.min (as the lower 95% confidence limit), whereas charcoal tubes could tolerate even heavier exposures, suggesting that both tubes are fit to measure the 8-h time-weighted average of DMF at 10 ppm.     

Exposure to Chlorpyrifos in Gaseous and Particulate Form in Greenhouses: A Pilot Study

Phase distribution of airborne chemicals is important because intake and uptake mechanisms of each phase are different. The phase distribution and concentrations are needed to determine strategies of exposure assessment, hazard control, and worker protection. However, procedures for establishing phase distribution and concentration have not been standardized. The objective of this study was to compare measurements of an airborne semivolatile pesticide (chlorpyrifos) by phase using two different procedures. Six pesticide applications in two facilities were studied and at each site, samples were collected for three time slots: T1, the first 1 or 2 hr after the commencement of application; T2, a 6-hr period immediately following T1; and T3, a 6-hr period after the required re-entry interval (24 hr for chlorpyrifos).Two phase-separating devices were co-located at the center of each greenhouse: semivolatile aerosol dichotomous sampler (SADS) using flow rates of 1.8 l.min^?1 and 0.2 l.min^?1, corresponding to a total inlet flow rate of 2.0 l.min^?1 with a vapor phase flow fraction of 0.1; and an electrostatic precipitator (ESP), along with a standard OVS XAD-2 tube. Chlorpyrifos in vapor and particulate form in a SADS sampling train and that in vapor form in an ESP sampling train were collected in OVS tubes. Chlorpyrifos in particulate form in the ESP setting would have been collected on aluminum substrate. However, no chlorpyrifos in particulate form was recovered from the ESP. Overall (vapor plus particle) concentrations measured by OVS ranged 11.7 – 186.6 μg/m³ at T1 and decreased on average 77.1% and 98.9% at T2 and T3, respectively. Overall concentrations measured by SADS were 66.6%, 72.7%, and 102% of those measured by OVS on average at T1, T2, and T3, respectively. Particle fractions from the overall concentrations measured by SADS were 60.0%, 49.2%, and 13.8%, respectively, for T1, T2, and T3. SADS gives better guidance on the distribution of chlorpyrifos than does the ESP, although the accuracy of the concentration distribution cannot be verified in the absence of a standardized procedure for determining phase division.     

Biological monitoring of methylhexahydrophthalic anhydride by determination of methylhexahydrophthalic acid in urine and plasma from exposed workers

Objective: To investigate whether methylhexahydrophthalic acid (MHHP acid) in urine and plasma can be used as a biomarker for exposure to methylhexahydrophthalic anhydride (MHHPA). Methods: MHHPA in air was sampled by Amberlite XAD-2 and analysed by gas chromatography (GC) with flame ionisation detection. MHHP acid in urine and plasma was analysed by GC with mass spectrometric detection. Workers occupationally exposed to MHHPA were studied. Air levels of MHHPA were determined by personal sampling in the breathing zone. Urinary levels of MHHP acid, a metabolite of MHHPA, were determined in 27 workers. In eight workers all urine was collected at intervals during 24 h. Plasma levels of MHHP acid were determined in 20 workers. Results: The time-weighted average (TWA) air levels ranged from 5 to 60 μg MHHPA/m³ during 8-h work-shifts. The urinary levels of MHHP acid increased during exposure and decayed after the end of exposure with an estimated half-life of about 6 h. A correlation was found between the TWA air levels of MHHPA and creatinine-adjusted MHHP acid levels in urine collected during the last 4 h of exposure. A correlation was also seen between the TWA air levels of MHHPA and the plasma concentrations of MHHP acid. An exposure to 20 μg MHHPA/m³ corresponded to about 140 nmol MHHP acid/mmol creatinine and about 40 nmol MHHP acid/l plasma. Conclusion: The results indicate that MHHP acid in urine or plasma may be used for biological monitoring of the exposure to MHHPA. Received: 4 October 1996 / Accepted: 2 January 1997     

工作场所空气中1,1-二氯-1-硝基乙烷的气相色谱测定法

目的 建立工作场所空气中1,1-二氯-1-硝基乙烷的气相色谱测定方法.方法 活性炭管采集工作场所空气中的1,1-二氯-1-硝基乙烷,以二硫化碳解吸后毛细管柱气相色谱法测定.结果 方法的测定范围为4.0～858.2μg/ml;回归方程Y=283X-1076,相关系数r=0.9999;最低检出浓度为0.4 mg/m3(以采集3L空气样品计);不同浓度测定的相对标准偏差(RSD)为1.8%～4.1%(批内精密度试验的RSD分别为2.9%、1.8%和2.0%;批间精密度试验的RSD分别为4.1%、3.5%和3.2%);解吸效率为88.5%～90.6%;穿透容量大于0.7 mg;采样效率100%;样品在室温下至少可保存7 d.结论 方法的各项指标均符合GBZ/T210.4-2008<职业卫生标准制订指南-工作场所空气中化学物质测定方法>要求,可用于工作场所空气中1,1-二氯-1-硝基乙烷的测定.     

Allergy to methyltetrahydrophthalic anhydride in epoxy resin workers.

One hundred and forty four current and 26 former workers in a plant producing barrels for rocket guns from an epoxy resin containing methyltetrahydrophthalic anhydride (MTHPA; time weighted average air concentration up to 150 micrograms/m3) were studied. They showed higher frequencies of work related symptoms from the eyes (31 v 0%; p < 0.001), nose (53 v 9%; p < 0.001), pharynx (26 v 6%; p < 0.01), and asthma (11 v 0%; p < 0.05) than 33 controls. Also they had higher rates of positive skin prick test to a conjugate of MTHPA and human serum albumin (16 v 0%; p < 0.01), and more had specific IgE and IgG serum antibodies (18 v 0%; p < 0.01 and 12 v 0%; p < 0.05 respectively). There were statistically significant exposure-response relations between exposure and symptoms from eyes and upper airways, dry cough, positive skin prick test, and specific IgE and IgG antibodies. There was a non-significant difference in reaction to metacholine between exposed workers and non-smoking controls. In workers with and without specific IgE antibodies, differences existed in frequency of nasal secretion (54 v 23%; p < 0.05) and dry cough (38 v 12%; p < 0.05). Workers with specific IgG had more dry cough (38 v 12%; p < 0.05), but less symptoms of non-specific bronchial hyperreactivity (0 v 26%; p < 0.05). Atopic workers sneezed more than non-atopic workers (65 v 30%; p < 0.01). In a prospective study five sensitised workers who left the factory became less reactive to metacholine, and became symptom free. In 41 workers who stayed, there was no improvement, despite a 10-fold reduction in exposure. The results show the extreme sensitising properties of MTHPA.     

Determination of phthalic anhydride in ambient air by high performance liquid chromatography

The paper considers the measurement of phthalic anhydride in the ambient air samples by high performance liquid chromatography. It describes conditions for air sampling and analysis of phthalic anhydride levels in the presence of concomitant components of its production (phthalic and maleic acids, maleic anhydride, etc.) on a liquid chromatograph with an UV detector. The procedure was tested, by estimating the quality of ambient air at the border of a sanitary protection zone of phthalic anhydride production and when analyzing the air in the industrial area. Field studies detected the concentrations of phthalic anhydrate in the air of an enterprise area, which were equal to 0.017-0.115 mg/dm3. Phthalic anhydride was detectable at a concentration of 0.001-0.0021 mg/dm3 at the border of the existing sanitary protection zone in single cases. The procedure has been recommended to measure the mass concentrations of phthalic anhydride aerosol and vapors in ambient air at the reference concentration.     

The effect of dry and humid hot air inhalation on expired relative humidity during exercise.

It has been previously demonstrated that under certain environmental conditions, expired air is not fully water saturated because of the low relative humidity of the first part of the expirate. This finding is of interest to those involved in respirator research, particularly those who design and test robotic metabolic simulators. These simulators must accurately mimic the physiological responses of human airways to breathing air of various temperatures and relative humidities (RHs). Because these responses are not fully quantified, this study examined the mean relative humidity of expired air during four inspired air conditions: cool dry (26 degrees C, 60% RH), cool humid (26 degrees C, 95% RH), hot dry (45 degrees C, 11% RH), and hot humid (45 degrees C, 95% RH). These conditions were administered during three exercise intensities: rest, low (35% VO2max), and moderate (70% VO2max). As compared to the cool dry (CD) condition, frequency of breathing (f) was 9.3% lower and tidal volume (VT) was 9.4% greater across all exercise intensities for the hot humid (HH) condition (p less than 0.05). Mean expired relative humidity (ERH) was substantially lower for the hot dry (HD) condition as compared to the other three conditions during each sampling period. These findings support the conclusion that the mean ERH of expired air depends upon several respiratory and environmental factors in addition to inspired air temperature.     

Evaluation of a new ammonia sampling and analytical procedure

A new monitoring procedure is described for the collection of ammonia in the workplace environment. Sampling is conducted using air sampling tubes packed with beaded activated carbon coated with sulfuric acid. The low cationic background of this packing permits the analysis of samples to be performed by ion chromatography, a technique which offers considerable advantage over current methods used to analyze industrial hygiene samples for ammonia. Excellent precision and accuracy are demonstrated on samples collected from atmospheres containing 0.5, 1 and 2 times TLV levels of ammonia. The analytical detection limit is such that a concentration 0.05 of TLV may be detected in a 3-L air sample with less than one percent breakthrough found in a 24-L sample at TLV.