Characteristics of Adsorption of Organic Solvent Vapors by a New Porous Carbon Material Made of Rice Husk as Measured by Breakthrough Curves.

We investigated the adsorbed amount of organic solvent vapors and adsorption rate of a new porous carbon material made from rice husk (rice husk activated carbon) in comparison with those of coconut shell activated carbon by the breakthrough curve. The adsorbed amount on the rice husk activated carbon and that on the coconut shell activated carbon were 81.3 ±â€¯3.3 mg/g and 71.7 ±â€¯5.0 mg/g for acetone, 8.0 ±â€¯1.7 mg/g and 6.3 ±â€¯0.2 mg/g for methanol, 196.8 ±â€¯8.8 mg/g and 262.8 ±â€¯10.4 mg/g for ethyl acetate, 234.8 ±â€¯11.9 mg/g, and 364.6 ±â€¯43.8 mg/g for toluene, respectively. These results suggest that the amount of organic solvent vapors adsorbed per unit weight of rice husk activated carbon is slightly larger for high polar compounds and is smaller for low polar compounds than that of coconut shell activated carbon. We compared the adsorption rate of the two materials by using the slope of the breakthrough curves. Even though there are some limitations to the characteristics of the new porous carbon material, it may be possible to use rice husk activated carbon as an alternative to coconut shell activated carbon in occupational and environmental measures.

[Adsorption Characteristics of Volatile Organic Compounds on Used Coffee Grounds Based on the Breakthrough Curves].

We investigated the adsorption characteristics of volatile organic compounds (VOCs) on the surface of coffee beans after extraction (coffee grounds). Temperature-controllable adsorption equipment of VOC vapor was manufactured, and nitrogen gas containing about 100 ppm of VOC vapor was introduced into a coffee extraction residue. The air in the downstream was analyzed with a gas chromatograph equipped with a flame ionization detector over a period of time. A breakthrough curve was obtained from the analysis of values and time, and the adsorbed amount of each volatile organic compound on the coffee grounds was calculated from a graphical integration of the breakthrough curve. Fourteen VOCs were tested, and the adsorbed amount tended to increase with increases in the boiling point of the VOCs. It was also found that the adsorbed amount of methanol and toluene was affected by the water content in the coffee grounds used in the experiment.

Examination of a New Desorption Method for Solid Adsorption Method of Working Environment Measurement －Attempt to Improve Desorption Efficiency of Organic Solvents from a Coconut-Shell-Activated Carbon Using Surfactant Solutions－.

For a new desorption method development for working environment measurement, desorption efficiency of organic solvent vapors from an activated carbon was examined using desorption solutions that consisted of anionic and nonionic surfactants. Ten µl of an aqueous solution of isopropyl alcohol or methyl ethyl ketone diluted with distilled water was spiked into a 10 ml vial with a coconut-shell-activated carbon (100 mg). The vial was left for 24 h, and 5 ml a desorption solution was added. Afterwards, the vial was put into an incubator at 60°C and left for 24 h, then the desorption efficiency was determined by analyzing the headspace gas in the vial with a gas chromatograph equipped with flame ionization detector. By adding one or four kinds of nonionic surfactants to the aqueous solution containing two kinds of anionic surfactants, the effect adding nonionic surfactant to the desorption efficiency was investigated, but improvement of desorption efficiency was not observed. On the other hand, desorption efficiency varied depending on the production lot of the coconut-shell-activated carbon tube used as the adsorbent.

Estimation of Equilibrated Vapor Concentrations Using the UNIFAC Model for the Tetrachloroethylene-Chlorobenzene System.

Equilibrated vapor concentrations at 25°C of the tetrachloroethylene-chlorobenzene system were obtained in the presence of air to establish a method for estimating vapor concentrations in work environments where multicomponent organic solvents are used. The experimental data were correlated by introducing activity coefficients calculated by the UNIFAC (Universal Quasichemical Functional Group Activity Coefficient) model. There were four interaction parameters between groups in this solution system, and three had already been determined.However, the fourth parameter--the interaction parameter between ACCl and Cl-(C=C) groups--remains unknown. Therefore, this parameter was determined by a nonlinear least-squares method to obtain the best fit for the experimental data. The calculated values were found to be in good agreement with the experimental values.

Decomposition Characteristics of Toluene Vapor Using Titanium Dioxide Photocatalyst and Zeolite Thermally Sprayed on an Aluminum Fiber Filter.

Decomposition characteristics of toluene vapor by titanium dioxide photocatalyst and zeolite that are prepared by thermal spraying on an aluminum fiber filter (photocatalyst filter) were investigated. Toluene vapor was injected into a small chamber made of stainless steel, and an air cleaner equipped with the photocatalyst filter was operated. The vapor concentration in the chamber decreased exponentially. The decreasing rate of toluene vapor in the chamber depended on the initial toluene concentration, and the higher the initial vapor concentration was, the lower the decreasing rate was obtained. The decreasing rate was constant during each decomposition experiment, although the concentration decreased with time. To investigate the effect of zeolite on the reduction of the vapor concentration, we compared the decreasing rates of toluene vapor by photocatalyst filters with and without zeolite.The decreasing rate of toluene concentration using the filter without zeolite was larger than that with zeolite. The reason for this would be that photocatalyst decomposed toluene not only in air but also adsorbed in zeolite.

Prenatal Exposure to 1-Bromopropane Suppresses Kainate-Induced Wet Dog Shakes in Immature Rats.

1-Bromopropane (1-BP) is used in degreasing solvents and spray adhesives. The adverse effects of 1-BP have been reported in human cases and adult animal models, and its developmental toxicity has also been reported, but its effects on developmental neurotoxicity have not been investigated in detail. We evaluated the effects in rat pups of prenatal exposure to 1-BP on behaviors such as scratching and wet dog shakes (WDS), which were induced by injection of kainate (KA). Pregnant Wistar rats were exposed to vaporized 1-BP with 700 ppm from gestation day 1 to day 20 (6 h/day). KA at doses of 0.1, 0.5, and 2.0 mg/kg were intraperitoneally injected into a control group and a 1-BP-exposed group of pups on postnatal day 14. There was no significant difference in scratching between the control and the prenatally 1-BP-exposed groups, while suppression of the occurrence ratio of WDS was observed at the low dose of 0.1 mg/kg of KA in the prenatally 1-BP-exposed pups. Our results suggest that prenatal exposure to 1-BP affects neurobehavioral responses in the juvenile period.

[Trial of a rapid measurement method by absorption photometer for the determination of the number of bacteria in the air].

A quick method to measure the number and the concentration of airborne bacteria was examined by combining bacteria staining with a crystal violet solution and absorptiometry. The suspension of the bacteria isolated from the environment was adjusted to 3.0 × 10(8) colony forming units (CFU) / ml in E. coli equivalent, and a 10-fold dilution series was created. After centrifugation of each bacterial suspension, the supernatant was removed and the bacteria were stained by adding a crystal violet solution. The sample was centrifuged again, and the supernatant was collected and named the unabsorbed sample. The residual bacteria were washed two times, and ethanol was added to the stained cells. The recovered solution collected by centrifugation of the cells was named the recovered sample.The chemicals in the samples were examined by high performance liquid chromatography, but no peak could be observed without the staining material. Absorption spectrophotometry showed that the determination limit of bacteria in the unabsorbed samples was 3.0 × 10(7) CFU / ml in E. coli equivalent and that in the recovered samples was 3.0 × 10(8) CFU / ml, indicating that the unabsorbed sample had a lower determination limit.

Reducing exposure levels of immersion washing workers to ortho-phthalaldehyde by improving exhaust systems.

OBJECTIVES: Concerning occupational exposure to ortho-phthalaldehyde (OPA) used in washing endoscope probes, the American Conference of Governmental Industrial Hygienists recommends a threshold limit value-ceiling (TLV-C) of 0.1 ppb. To adhere to this extremely low exposure limit, this case study aimed to reduce OPA exposure concentrations of workers during immersion washing of an endoscope probe body. This was achieved by attaching a new duct and hood to the existing ceiling exhaust system. METHODS: The type of hood was determined by calculating and comparing the capture velocity obtained by assuming the exterior or enclosing hood. Additionally, the effect on improving the working environment was tested before and after the installation of the hood by measuring the OPA vapor concentration. RESULTS: The calculated capture velocities of the exterior and enclosing hoods were 0.05 m/s and 0.19 m/s, respectively. Considering the operability, the exterior hood was more appropriate; however, the calculated capture velocity indicated potential inadequacy in meeting the TLV-C requirement, leading to the adoption of the enclosing hood. The OPA vapor concentration in ceiling value measurement taken after enclosing hood implementation was reduced to 0.2 ppb, that is 1/10 of the original concentration. CONCLUSIONS: Although the environmental concentration after the improvement still exceeded the TLV-C of 0.1 ppb, this study's findings indicate that even substances with extremely low occupational exposure limits can be managed with appropriate local exhaust ventilation.

Evaluation of a real-time method for monitoring volatile organic compounds in indoor air in a Japanese university.

OBJECTIVE: Real time monitoring of total volatile organic compounds (TVOC) in rooms of Japanese university buildings was carried out to understand the temporal changes in actual indoor air quality. METHODS: The TVOC concentrations in seven different rooms, consisting of a lecture room, a seminar room, three laboratories, a computer room and a library, were monitored continuously for 24 h via a personal VOC monitor equipped with a semiconductor gas sensor. An active sampling-thermal desorption method using stainless steel tubes packed with Tenax-TA was also carried out simultaneously to verify the usability of the monitor. RESULTS: The TVOC concentrations measured by the personal VOC monitor were closely correlated with those measured by the active sampling method. The TVOC concentration in all rooms was generally low during the day and increased during the night. This concentration change corresponded to the ventilation cycle in the building. During the day, the TVOC concentration was generally lower than the provisional target criterion (advisable value) of indoor air quality in Japan (400 µg/m³). During the night, however, it exceeded this criterion in several rooms, especially during the summer season. CONCLUSION: The real-time monitor using a semiconductor gas sensor can provide useful data on changes in the TVOC concentration in indoor air with high sensitivity.

[Present state and problems of work environment control in the workplaces using hazardous materials based on the Occupational Safety and Health Act in Japan].

In Japan, working environment measurement is prescribed in the designated workplaces using hazardous materials. Measurements should be carried out periodically and countermeasures are performed depending on the results. By introducing such a system, working environments have remarkably improved. However, in the designated workplaces, measurements should be continued even in work environments found safe. On the other hand, measurement need not be obliged for non-designated workplaces even if hazardous materials are utilized.In the United States of America and many European countries, work environment management and work management are carried out by measuring personal exposure concentrations. In Japan, the Ministry of Health, Labour and Welfare is now discussing the introduction of personal exposure monitoring. However, many problems exist to prevent the simple introduction of American and European methods. This paper describes the brief history, present state and problems of work environment control in Japan, comparing with the systems of American and European countries.

Characteristics of a real time monitor using the interference enhanced reflection method for organic vapors.

Performance and sensor characteristics of a monitor for volatile organic compounds (VOC monitor) using the interference enhanced reflection (IER) method were investigated for 52 organic solvent vapors that are designated as class 1 and class 2 organic solvents by the Ordinance of Organic Solvent Poisoning Prevention in Japan. Test vapors were prepared by injecting 1 to 3 µl of liquid solvent into a 20 l Tedlar(®) bag and perfectly vaporizing them. The vapor concentration was simultaneously measured with the monitor and a gas chromatograph (GC) equipped with flame ionization detector, and both values were compared. The monitor could detect all the solvent vapors that we used. Linear response was obtained between the concentration measured by the monitor and those by the GC. The monitor could detect 1/10 of the administrative control level for 37 of 52 solvent vapors, including toluene and xylenes. For 15 vapors, on the other hand, the monitor could not be used for the working environment measurement because the sensor response was low or the regression lines did not pass through the origin.

The effect of mask fit test on the association between the concentration of metals in biological samples and the results of time-weighted average personal exposure: A study on Japanese male welders.

OBJECTIVES: The mask fit test confirms whether the wearing condition of the wearer's face and the facepiece of the respirators are used appropriately. This study aimed to examine whether the results of the mask fit test affect the association between the concentration of metals related to welding fumes in biological samples and the results of time-weighted average (TWA) personal exposures. METHODS: A total of 94 male welders were recruited. Blood and urine samples were obtained from all participants to measure the metal exposure levels. Using personal exposure measurements, the 8-h TWA (8 h-TWA) of respirable dust, TWA of respirable Mn, and 8-h TWA of respirable Mn were calculated. The mask fit test was performed using the quantitative method specified in the Japanese Industrial Standard T8150:2021. RESULTS: Fifty-four participants (57%) passed the mask fit test. Only in the Fail group of the mask fit test, it was observed that blood Mn concentrations be positively associated with the results of TWA personal exposure after adjusting for multivariate factors (8-h TWA of respirable dust; coefficient, 0.066; standard error (SE), 0.028; P = 0.018, TWA of respirable Mn: coefficient, 0.048; SE, 0.020; P = 0.019, 8 h-TWA of respirable Mn: coefficient, 0.041; SE, 0.020; P = 0.041). CONCLUSIONS: The results clarify that welders with high concentrations of welding fumes in their breathing air zone are exposed to dust and Mn if there is leaking air owing to the lack of fitness between respirators and the wearer's face when using human samples in Japan.

Associations between welding fume exposure and neurological function in Japanese male welders and non-welders.

OBJECTIVES: There are some studies reporting the association between (manganese [Mn]) exposure to welding fume and neurological dysfunction. This study examined the relationship between Mn exposure and neurological behavior in Japanese male welders and non-welders using biological samples, which to date has not been assessed in Japan. METHODS: A total of 94 male welders and 95 male non-welders who worked in the same factories were recruited. The blood and urine samples were obtained from all the participants to measure Mn exposure levels. Neurological function tests were also conducted with all participants. The sampling of the breathing air zone using a personal sampler was measured for welders only. RESULTS: The odds ratios (ORs) for the Working Memory Index (WMI) scores were significantly higher among all participants in the low blood Mn concentration group than those in the high blood Mn concentration group (OR, 2.77; 95% confidence interval [CI], 1.24, 6.19; P = .013). The association of WMI scores and blood Mn levels in welders had the highest OR (OR, 3.73; 95% CI, 1.04, 13.38; P = .043). Although not statistically significant, a mild relationship between WMI scores and blood Mn levels was observed in non-welders (OR, 2.09; 95% CI, 0.63, 6.94; P = .227). CONCLUSIONS: The results revealed a significant positive relationship between blood Mn and neurological dysfunction in welders. Furthermore, non-welders at the same factories may be secondarily exposed to welding fumes. Further research is needed to clarify this possibility.

[Sensing characteristics of a real-time monitor using a photoionization detector on organic solvent vapors].

Measurements of organic solvents in the work environment are carried out by either direct sampling using plastic bags/gas chromatography, solid sorbent adsorption using charcoal tubes/gas chromatography, or by a direct reading method using detector tubes. However, these methods cannot always measure the work environment accurately because the concentration of hazardous materials changes from time to time, and from space to space. In this study, the sensor characteristics of a real time monitor using a photoionization detector that can monitor vapor concentration continuously were investigated for 52 organic solvent vapors that are required to be measured in the work environment by the Ordinance of Organic Solvent Poisoning Prevention in Japan. The sensitivity of the monitor was high for the solvents with low ionization potential. However, the sensitivity for the solvents with high ionization potential was low, and the sensor could not detected 7 solvents. Calibration of the sensor using a standard gas was desirable before being used for measurement because the sensitivity of the sensor was variable.

[Relationship between physical configuration of hood and velocity for local exhaust systems].

The hood performance of a local exhaust ventilation system is determined by the capture velocity and the air flow rate. The equation proposed by Dalla Valle has been widely used to speculate this relationship. However, Dalla Valle used different formulae for slot and plain opening (rectangular) hoods, and the calculated values near the boundary between the slot and plain opening by these formulae do not always match each other. In this study, we measured capture velocity of four hoods by changing the distance from the hood face for different aspect ratios. We also tried to develop an empirical formula to express a relationship that could be applied to both types of hoods. As a result, it was found that the relationship between air velocity in front of exterior hoods and air flow rate could be expressed as the sum of two exponential functions with distance. In addition, when the hood aspect ratio was less than 9 the values of the capture velocity calculated by the proposed equation were in good agreement with the experimental ones.

Cerebral excitability in pup rats prenatally exposed to 1-bromopropane is suppressed by bromide accumulated in the brain.

Previously, we reported that prenatal exposure to 1-bromopropane (1-BP) causes the accumulation of bromide (Br-) in the brain of rat pups. Here, we aimed to investigate the effects of Br- accumulation in rat pups prenatally exposed to 1-BP vapor. Dam rats were exposed to 1-BP (400 or 700 ppm; 1-BP group) by inhalation, or to NaBr (20 mM; Br- group) in drinking water during gestation days 1-20. We also analyzed pentylenetetrazole (PTZ, 60 mg/kg, ip)-induced behavioral changes in pups prenatally exposed to 1-BP or Br- on postnatal day (PND) 14. PTZ-induced epileptic convulsions were inhibited in both 1-BP (700 ppm) and Br- groups. The inhibition of neuronal excitability induced by Br- was evaluated electrophysiologically using the hippocampal slices obtained from PND14-16 pups. PTZ (2 mM) failed to induce epileptiform discharge in the presence of 1.2 mM Br- in the slices obtained from the control group. However, it induced epileptiform discharge following the removal of Br-, by perfusing artificial cerebrospinal fluid into the slices obtained from the Br- group. Our results indicate that Br- accumulates in the brain of neonatal rat pups prenatally exposed to 1-BP vapor suppressed neuronal excitability.

Method of estimating changes in vapor concentrations continuously generated from two-component organic solvents.

We measured vapor concentrations continuously evaporated from two-component organic solvents in a reservoir and proposed a method to estimate and predict the evaporation rate or generated vapor concentrations. Two kinds of organic solvents were put into a small reservoir made of glass (3 cm in diameter and 3 cm high) that was installed in a cylindrical glass vessel (10 cm in diameter and 15 cm high). Air was introduced into the glass vessel at a flow rate of 150 ml/min, and the generated vapor concentrations were intermittently monitored for up to 5 hours with a gas chromatograph equipped with a flame ionization detector. The solvent systems tested in this study were the methanoltoluene system and the ethyl acetate-toluene system. The vapor concentrations of the more volatile component, that is, methanol in the methanol-toluene system and ethyl acetate in the ethyl acetate-toluene system, were high at first, and then decreased with time. On the other hand, the concentrations of the less volatile component were low at first, and then increased with time. A model for estimating multicomponent organic vapor concentrations was developed, based on a theory of vapor-liquid equilibria and a theory of the mass transfer rate, and estimated values were compared with experimental ones. The estimated vapor concentrations were in relatively good agreement with the experimental ones. The results suggest that changes in concentrations of two-component organic vapors continuously evaporating from a liquid reservoir can be estimated by the proposed model.

Development of a measurement method to determine the ceiling exposure concentration of ortho-phthalaldehyde handling workers.

OBJECTIVES: The purpose of this research was to develop and validate an analytical method for rapid determination of the exposure of workers to ortho-phthalaldehyde (OPA) at the ceiling threshold concentration. METHODS: A 2,4-dinitrophenylhydrazine (DNPH)-silica cartridge was chosen as a sampler. OPA collected by the DNPH-silica cartridge was subsequently extracted with 5 mL of acetonitrile. A 50-µL aliquot of phosphoric acid/acetonitrile solution (2%, v/v) was added to 950 µL of the extraction solution and allowed to stand for 30 minutes at room temperature. This solution was then analyzed by high-performance liquid chromatography tandem mass spectrometry. The basic characteristics of the proposed method, such as recovery, repeatability, limit of quantification, and storage stability of the samples, were examined. RESULTS: The overall recoveries of OPA from OPA-spiked DNPH-silica cartridges were 93.6%-100.1% with relative standard deviations, representing the repeatability, of 1.5%-10.8%. The limit of quantification was 0.165 ng/sample. The recovery of OPA from DNPH-silica cartridges after 5 days of storage in a refrigerator exceeded 95%. CONCLUSIONS: The proposed method enabled the determination of the OPA concentration corresponding to the Threshold Limit Value-Ceiling of 0.1 ppb recommended by the American Conference of Governmental Industrial Hygienists, with a minimum sampling time of 18 seconds (corresponding to a sampling volume of 300 mL at 25°C and 1 atm). Thus, this method will be useful for estimating worker exposures to OPA.

Exposure to 1-bromopropane vapors during pregnancy enhances the development of hippocampal neuronal excitability in rat pups during lactation.

OBJECTIVES: Although 1-Bromopropane (1-BP) exposure has been reported to cause neurotoxicity in adult humans and animals, its effects on the development of the central nervous system remain unclear. Recently, we reported delayed developmental neurotoxicity (DNT) upon 1-BP exposure in rats. Here we aimed to study the effect of prenatal 1-BP exposure on the hippocampal excitability in the juvenile offspring. METHODS: Pregnant Wistar rats were exposed to vaporized 1-BP for 20 days (6 h/d) with concentrations of 0 (control), 400, or 700 ppm. Hippocampal slices were prepared from male offspring during postnatal days (PNDs) 13, 14, and 15. Field excitatory postsynaptic potential (fEPSP) and population spike (PS) were recorded simultaneously from the CA1 region. RESULTS: In the exposed groups, the stimulation/response relationships of fEPSP slope and PS amplitude were enhanced more than in the control group at PND 14. Analysis of fEPSP-spike coupling demonstrated increased values of Top and Eslope50 in the exposed groups. Real-time PCR analysis showed a significant increase in the mRNA levels of the adult type Nav 1.1 Na+ channel subunit and the GluR1 glutamate receptor subunit in the hippocampus of the 700 ppm group at PND 14. CONCLUSIONS: Our results provide evidence that prenatal exposure to 1-BP accelerates developmental enhancement of hippocampal excitability in the pups before eye-opening. The current study suggests that our evaluation method of DNT is applicable to the industrial chemical 1-BP.

Evaluation of the ceiling levels of ortho-phthalaldehyde exposure among health care workers engaged in endoscope disinfection: A new methodology using video-exposure monitoring.

OBJECTIVES: The present study aimed to develop a method for measuring the ceiling level of ortho-phthalaldehyde (OPA) exposure and evaluate the ceiling levels of OPA exposure among health care workers who handle disinfectant solutions containing OPA for the disinfection of endoscopes. METHODS: The study consisted of a preliminary survey and main survey. In the preliminary survey, processes involving high-concentration exposure to OPA were identified by video-exposure monitoring (VEM). In the main survey, the ceiling levels of OPA exposure for high-concentration exposure processes identified from the results of the preliminary survey were determined using a measuring method combining sampling using a 2,4-dinitrophenylhydrazine-silica cartridge and analysis by high-performance liquid chromatography tandem mass spectrometry. RESULTS: In the preliminary survey, seven processes involving high-concentration exposure to OPA were identified by VEM. The duration of each process was short, lasting from 20 seconds to a few minutes. In the main survey, the OPA concentrations for the identified high-concentration exposure processes ranged from 1.18 to 4.49 ppb, which markedly exceeded the threshold limit value ceiling (TLV-C) of 0.1 ppb recommended by the American Conference of Governmental Industrial Hygienists. CONCLUSIONS: The method for measuring the ceiling level of OPA exposure was established using VEM and the highly sensitive method of chemical analysis; and we successfully evaluated the ceiling levels of OPA exposure among health care workers engaged in endoscope disinfection. This approach can also be applied to other chemical substances with recommended TLV-Cs, and important information for reducing exposure can thus be obtained.