[Causes of Countermeasures Against Serious Accidents Caused by Health Hazards of Chemical Substances, Based on Cases of Occupational Accidents in Japan].

The purpose of this study was to summarize the typical and specific causes and risk reduction measures of serious accidents in Japan caused by chemical substances in terms of the 10 types of human health hazards in the UN GHS (Globally Harmonized System of Classification and Labelling of Chemicals) classification. The list of "Cases of Major Accidents Caused by Chemical Substances" published on the "Safety in the Workplace Website" of the Ministry of Health, Labor and Welfare (MHLW) was linked to the "Results of GHS Classification by the Government" of the National Institute of Technology and Evaluation (NITE). Analysis was conducted by health hazards in order to obtain reference examples of measures taken against health hazards in response to the revision of the law on autonomous chemical substance management in 2022. Using the text mining tool KH Coder ver. Three using cluster analysis, we grouped causes and measures among serious disasters by health hazard, illustrated co-occurrence networks, and extracted typical examples of each in a co-occurrence network. Representative causes of and measures against occupational accidents caused by health hazardous properties were summarized from the extracted typical cases. Although few occupational accidents were caused by the health hazards of chemicals, when all health hazards were classified into acute toxicity, acute health hazard, and chronic health hazard, contact was a clear cause for many of the acute toxicity and acute health hazards, such as corrosiveness and sensitization. However, many occupational accidents were caused by the physical hazardous aspects of the chemical substances or by the safety aspects of the workplace. Causes of occupational accidents due to health hazards included unsafe behavior and unsafe conditions, or lack of understanding of the physicochemical properties of a substance and specific reactions such as mixing or hydrolysis of the substance. Typical risk reduction measures for health hazards included equipment to prevent human contact with health hazardous substances, systems to control unsafe behavior, promoting understanding of chemical reactions, and providing information about chemicals to all persons involved in testing, research, and subcontract work. The data of occupational accident cases of "death or more than 4 days lost from work" were used. Most of the cases were related to acute health hazards, but relatively few to chronic health hazards, and few occupational accidents were caused by health hazards. Most of the occupational accidents were caused by health hazards due to the physical hazards of chemical substances and inadequate workplace safety. In light of the above, it is necessary in autonomous chemical substance management to first take risk reduction measures for workplace safety and chemical physical hazards, then to prevent contact with acute toxicity and acute health hazards such as corrosiveness and sensitization, and, lastly, to take risk reduction measures for chronic health hazards, using allowable concentrations and controlled concentrations as indices.

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.

[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.

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.

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.

[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.

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.

Biological effect of carbon graphite whisker in rat lung by long-term Inhalation.

Carbon graphite whisker (CGW) was used in a 1-year inhalation study in male Wistar rats and its biological effect was observed until the 1-year clearance period. The inhalation study was conducted at 2.6 +/- 0.5 mg/m(3) (equivalent to 44.5 +/- 15.0 fibers/mL) for 6 hours a day, 5 days a week for 1 year. There were no differences in survival rate between the exposure and control groups during this examination; however, the body weights were significantly different at the end of the 1-year clearance. The lung weight at 3 days and 1 year after the end of exposure was not significantly different in both groups. The deposited amount of CGW was 6.83 +/- 0.75 mg at 3 days post-exposure; the deposition rate was 17.6%. Only around 30% of the total deposited CGW was cleared during the 1-year clearance period. The geometric means of CGW in the lung, i.e. CMD (count median diameter) and CML (count median length), hardly changed, and the clearance was delayed. In the histopathological examination, there was mild fibrosis in all exposed rats irrespective of the clearance period. One adenoma was observed in a single animal at 3 days post-exposure, while no adenomas were observed in the exposure group after the 1-year clearance. Epithelial hyperplasia was found in some animals.

[Construction of a tool for risk assessment of infectious diseases in a workplace--as a primary precaution].

We describe here a tool for risk assessment and management of infectious diseases in a workplace. This was constructed as a primary precaution for the prevention of infectious diseases in a workplace, not to be used as a countermeasure of diseases in the time of or after an occurrence. The tool grades risk levels of each of the factors influencing infectious diseases in the workplace and an assessment based on the total point are given. Ordinary workplaces should be chosen, such as factories and office buildings, not places where medical experts or hygienists work, such as hospitals, schools and concessionaries, etc. Three risk factors for infection are pathogens, route and human host. The factor of a pathogen is divided into two groups, spreadable (from human to human) and non-spreadable. The risk of spreadable pathogens is assessed by the ages of workers, CO2 concentration and air volume, and the combination of the existence of common places and collaborative work. The risk of non spreadable pathogens is evaluated by the ages of workers, air current and air volume, and existence of equipment generating aerosol. In cases where the total point is over 7, the risk is assessed as high level (group A) and daily measures must be taken, such as ensuring proper operation of the infection control committee, education, management of working conditions and management of working environments. In cases where the score is 5 or 6, the risk is assessed as intermediate level (group B) and daily measures are recommended, such as ensuring proper operation of the infection control committee and education. In the case of a score less than 4, the risk is assessed as low level (group C) and these daily measures are not necessary. Instead, an infection control committee should be organized and concrete measures should be taken upon an outbreak of an infectious disease.

[Bioaerosol concentrations and the identification of aerosolized bacteria by 16S rDNA analysis in work environments].

Bioaerosols cause sick building syndrome (SBS) and allergy. Many kinds of bioaerosol impactors are used for measurement of airborne microorganism concentrations in Japan. However, because the impactors are set on agar plates, some microorganisms cannot make colonies on the plates because of their lower viability or demands of nutrition. On the other hand, by double staining using ethidium bromide (EtBr) and carboxyfluorescein diacetate (CFDA), both total cells and cells with esterase activities can be detected without incubation. In this study, we calculated total cell concentrations and percentages of cells with esterase activities by the combination of filter sampling and double staining (EtBr and CFDA) from air of a laboratory, a conference room and outdoors. Temperature and humidity in the laboratory were constantly kept by an air conditioner, but in the conference room, an air conditioner was only operated sometimes because of its low frequency of use. There were no significant differences between total cell concentrations and humidity in both rooms, but increase of the percentages of cells with esterase activities depended on rainfall before the samplings (n=15, p<0.05 by Mann-Whitney test). The increase of active microorganisms by rainfall should be considered when we evaluate the risk of bioaerosols in the workplace. There were few differences in classifications of aerosolized bacteria by 16S rDNA sequence-based homology between the laboratory and the conference room. In both rooms, few pathogenic bacteria were observed.

A new desorption method for removing organic solvents from activated carbon using surfactant.

OBJECTIVES: A new desorption method was investigated, which does not require toxic organic solvents. Efficient desorption of organic solvents from activated carbon was achieved with an ananionic surfactant solution, focusing on its washing and emulsion action. METHODS: Isopropyl alcohol (IPA) and methyl ethyl ketone (MEK) were used as test solvents. Lauryl benzene sulfonic acid sodium salt (LAS) and sodium dodecyl sulfate (SDS) were used as the surfactant. Activated carbon (100 mg) was placed in a vial and a predetermined amount of organic solvent was added. After leaving for about 24 h, a predetermined amount of the surfactant solution was added. After leaving for another 72 h, the vial was heated in an incubator at 60°C for a predetermined time. The organic vapor concentration was then determined with a frame ionization detector (FID)-gas chromatograph and the desorption efficiency was calculated. RESULTS: A high desorption efficiency was obtained with a 10% surfactant solution (LAS 8%, SDS 2%), 5 ml desorption solution, 60°C desorption temperature, and desorption time of over 24 h, and the desorption efficiency was 72% for IPA and 9% for MEK. Under identical conditions, the desorption efficiencies for another five organic solvents were investigated, which were 36%, 3%, 32%, 2%, and 3% for acetone, ethyl acetate, dichloromethane, toluene, and m-xylene, respectively. CONCLUSIONS: A combination of two anionic surfactants exhibited a relatively high desorption efficiency for IPA. For toluene, the desorption efficiency was low due to poor detergency and emulsification power.

The effect of lung burden on biopersistence and pulmonary effects in rats exposed to potassium octatitanate whiskers by intratracheal instillation.

In our previous inhalation studies on health effects of the asbestos substitute, potassium octatitanate whiskers (POW), we showed that an excess amount of POW deposition in the rat lung increased biopersistence resulting in fibrotic changes. The critical deposition amount which induced the higher biopersistence was estimated to lie between 1.5 mg and 2.4 mg. In order to find the exact amount, the relationship between the lung POW burden and biopersistence was investigated by the intratracheal instillation method. The chemical formula of POW is K2Ti8O17 and the geometric mean fiber diameter (geometric standard deviation, GSD) and geometric mean fiber length (GSD) are 0.35 microm (1.6) and 4.4 microm (2.7), respectively. Rats were intratracheally instilled with 0.5 mg, 1.0 mg, 2.0 mg or 5.0 mg of POW and sacrificed at 1 day and 1, 3, 6 and 12 months after the instillation. The POW amount in each lung was chemically analyzed by ICP-AES after microwave digestion and the biological half time (BHT) of each POW dose was calculated. The BHTs of each group were 10, 15, 20 and 42 months for 0.5, 1.0, 2.0 and 5.0 mg of POW, respectively, and BHT showed a linear dose-dependent increase, but without a threshold within the range of 0.5 mg to 5.0 mg, which was recognized in our earlier inhalation studies. In the histopathological photograph just after the instillation, many macrophages, which had phagocytized many more fibers, existed around the bronchiole compared with the earlier inhalation study at almost the same deposited amount. The relationship between POW amount and biopersistence in this intratracheal instillation study was different from that of our previous inhalation studies, probably due to the unnatural method of the fiber introduction to the lung, which in turn led to a different fiber distribution. It is suggested that an intratracheal instillation study is not an appropriate method for estimating excess deposition amounts of POW and an inhalation study will be needed. However, this intratracheal instillation study clarified that the clearance of POW was delayed as compared with previous inhalation studies at similar deposition amounts and this result has importance for the hazard assessment of dusts in animal experiments.

[Measurement of gene expression of CYP mRNA in liver of rats exposed to toluene and 1-butanol vapors].

A reduction of the biological half life of toluene in blood in the simultaneous exposure to toluene and alcohol vapors has been reported. To clarify the cause of this reduction, gene expression of CYP mRNA in liver of rats exposed to bi-component organic vapors was investigated. Wistar male rats were repeatedly exposed to 500 ppm of toluene and 300 ppm of 1-butanol vapors individually and simultaneously by inhalation 6 hours a day, five days a week for 4 weeks. After the exposure, the rats were sacrificed and the livers were collected and homogenized. RNA was extracted from the livers, and gene expression of CYP mRNA was observed by reverse transcription-polymerase chain reaction (RT-PCR). The gene expression of CYP3A2 in the simultaneous exposure group was significantly higher than that in the toluene exposure group. However, there was no significant difference in that of CYP1A2, CYP2B1, CYP2C11, CYP2E1 and CYP4A1.

[Sampling and detection methods of bioaerosols for the risk assessment of microorganisms in work environments].

Bioaerosols including bacteria and fungi have been almost unrecognized as pollutants of work environments in Japan. The combination of filter sampling and DNA staining by ethidium bromide (EtBr) was examined for the detection and evaluation of total numbers of bioaerosols, including viable and dead microorganisms, for risk assessment in work environments. With direct counting of microorganisms by EtBr concentrations of total cells were obtained in a shorter time than plate culture, the traditional method for detection of microorganisms. Total cell concentrations (cells/m3) were about 100 times greater than colonized cell concentrations (CFU/m3) in all samples. In some microscopic fields, macro conidia produced from some kinds of fungi were observed, but they were not detected by plate culture. Airborne bacterial 16S rDNA amplified by PCR were determined for their base sequences by DNA sequence analysis and classified by sequence-based homologies. Base sequences from 2 samples each contained 6 common groups of phylum. The combination of filter sampling and direct counting by EtBr staining was shown to be a better method for detecting and evaluating total cell concentrations in the risk assessment of sick building syndrome and allergy.

Comparison of sensor characteristics of three real-time monitors for organic vapors.

OBJECTIVE: Sensor characteristics and performance of three real-time monitors for volatile organic compounds (VOC monitor) equipped with a photo ionization detector (PID), a sensor using the interference enhanced reflection (IER) method and a semiconductor gas sensor were investigated for 52 organic solvent vapors designated as class 1 and class 2 of organic solvents by the Ordinance of Organic Solvent Poisoning Prevention in Japan. METHODS: Test vapors were prepared by injecting each liquid solvent into a 50 l Tedlar® bag and perfectly vaporizing it. The vapor concentration was from one-tenth to twice the administrative control level for all solvents. The vapor concentration was measured with the monitors and a gas chromatograph equipped with a flame ionization detector simultaneously, and the values were compared. RESULTS: The monitor with the PID sensor could measure many organic vapors, but it could not detect some vapors with high ionization potential. The IER sensor could also detect many vapors, but a linear response was not obtained for some vapors. A semiconductor sensor could detect methanol that could not be detected by PID and IER sensors. CONCLUSIONS: Working environment measurement of organic vapors by real-time monitors may be possible, but sensor characteristics and their limitations should be known.

The effect of lung burden on biopersistence and pulmonary effects in rats exposed to potassium octatitanate whiskers by inhalation.

The effect of lung burden on biopersistence and histopathological changes caused by potassium octatitanate whiskers (POW) which is one of the asbestos substitutes were investigated for 1-yr and 4-wk inhalation periods. In the 1-yr inhalation experiment, male Wistar rats were exposed to POW (TW) for 6 h/d, 5 d/wk under the same conditions as a previous study of POW (PT1, JFM fiber) which is made by different manufacturer. The exposure concentration was 1.9 +/- 0.7 mg/m(3) and the mass median aerodynamic diameter (MMAD) and geometric standard deviation (GSD) in the chamber were 1.6 microm and 2.9. Rats were sacrificed at 3 d and 1 yr after the inhalation experiment and TW deposits in the lungs were determined by ICP-AES. Lung burden at 3 d and 1 yr after the inhalation was 2.39 +/- 0.50 mg and 1.37 +/- 0.96 mg, respectively, the deposition fraction was 8.1% and biological half time (BHT) was 15 months. Aggregated dust cells and mild fibrotic changes around these dust cells were observed in the exposed rat lung. These results were almost the same as those obtained in the previous 1-yr PT1 study. In the 4-wk inhalation experiment, to investigate the effect of lung burden on biopersistence and histopathological change, male Wistar rats were exposed to PT1. The exposure concentration was 102 +/- 21 mg/m(3), MMAD (GSD), the geometiric mean length and diameter (GSD) of the PT1 in the chamber were 1.6 microm (3.0), 2.2 microm (1.8) and 0.33 microm (1.5), respectively. Rats were sacrificed at 3 d, 1 wk, and 1, 3, 6 and 12 months after the inhalation experiment. The lung burden of POW at 3 d after 4 wk inhalation was 1.49 +/- 0.19 mg, which was close to the estimated amount of overload. The BHT of the total mass (4.1 months) was not prolonged, but aggregated dust cells were observed in the subpleural region and around the bronchioles and mild fibrotic changes were observed only around the dust cells at one year after the 4-wk inhalation. It is considered that the excessive exposure which impairs the function of alveolar macrophage mediated clearance may cause the aggregation of dust cells and fibrotic changes.

[Vapor-liquid equilibria for multicomponent organic solvents].

Most organic solvents used in the workplace are mixed solvents consisting of several components. It is therefore very important to know the equilibrated vapor concentrations in order to control the work environment. In this study, the vapor-liquid equilibrium for multicomponent organic solvents is estimated by introducing the activity coefficients, which are calculated with the UNIFAC (Universal Quasichemical Functional Group Activity Coefficient) model. For two-component solvents, that is, the toluene-methanol and o-xylene-methanol systems, the calculated values of the vapor fraction and the equilibrated vapor concentrations are in good agreement with the reference ones. For three- or four-component solvents that are used as thinners, the calculated values are also generally in good agreement with the reference ones.

[Antimicrobial activity of hinokitiol against Legionella pneumophila].

Antimicrobial activity of hinokitiol (beta-thujaplicin), which is a major component of the essential oil of Chamaecyparis obtuse, against Legionella pneumophila was investigated experimentally. The quantitative antibacterial assay of hinokitiol was carried out by the disk-diffusion method. The test concentrations of hinokitiol were 0.39 to 25.0 micrograms/disk, and the lowest concentrations of hinokitiol that showed growth inhibition against L. pneumophila were 1.56 micrograms/disk on B-SYE agar and 0.39 microgram/disk on B-SYE agar without iron.

Effects of inhaled methyl bromide gas on the metabolic system and kinetics of bromine ion in rats.

Wistar male rats were exposed to 2000 ppm of methyl bromide gas for one hour (single exposure experiment) or 300 ppm of the gas for 6 hours a day, 3 days a week for 4 or 8 weeks (repeated exposure experiment) to investigate the metabolism of inhaled methyl bromide. After the exposure was completed, the bromine ion concentration in serum was measured up to 60 days. The serum bromine ion concentration was determined by a headspace gas chromatography-mass spectrometry after converting bromine ion to methyl bromide by adding dimethyl sulfate in the serum samples. In the single exposure experiment, the bromine ion concentration decreased quickly within one day after the end of the exposure, and then began to decrease gradually. In the repeated exposure experiment, on the other hand, the bromine ion concentration decreased almost exponentially. A two-compartment model was applied to analyze the clearance rate of bromine ion. The biological half time of serum bromine ion was 9.1 days for the single exposure and 5.4 days for the repeated exposure. The amount of cytochrome P450 (CYP) in liver microsomes was measured after the end of exposure. CYP in liver was not significantly different after the repeated exposure but it decreased after the single exposure.