Akihiro Araki

Improved method for mutagenicity testing of gaseous compounds by using a gas sampling bag

A simple and safety gas exposure method was developed using a gas sampling bag as an exposure vessel and a preparation vessel of diluted gas. The gas exposure conditions such as amount of S9 in the plate, volume of gas for the plate, amount of top agar, exposure period and exposure temperature were examined by mutagenicity testing of 1,3-butadiene using the gas sampling bag. Mutagenicity tests of 14 compounds and 1,3-butadiene on S. typhimurium TA98, TA100, TA1535 and TA1537, and E. coli WP2 uvrA were also examined by the developed gas exposure method. 1,3-Butadiene, propyne (methyl acetylene), monochlorodifluoromethane, ethylchloride, diborane and silane were mutagenic. 1-Butene, 2-butene, 2-methylpropene, methyl vinyl ether, trichlorofluoromethane, dichlorodifluoromethane, 1,2-dichloro-1,1,2,2-tetrafluoroethane, 1,1-difluoroethane and phosphine were not mutagenic on S. typhimurium TA98, TA100, TA1535 and TA1537, and E. coli WP2 uvrA with or without metabolic activation. These results were compatible with a previous report, and this developed method has the advantage that it can be tested easily and safely for combustible and self-combustible substances such as 1,3-butadiene and silane.

Mutagenicities of xanthone derivatives in Salmonella typhimurium TA100, TA98, TA97, and TA2637

The mutagenicities of naturally occurring xanthones were tested in Salmonella typhimurium TA100, TA98, TA97, and TA2637 by the preincubation method. Xanthydrol, gentisein, gentisin, isogentisin, 1-hydroxy-3,7-dimethoxyxanthone, 1,3,7-trimethoxyxanthone, desmethylbellidifolin, bellidifolin and dimethylbellidifolin were mutagenic, but unsubstituted xanthone was not mutagenic to TA100, TA98, TA97 and TA2637 with or without a metabolic activation system. The beta-O-glucosides, norswertianolin and swertianolin, were only mutagenic when a metabolic activation system containing beta-glucosidase was used, and the C-glucoside mangiferin was not mutagenic even with this system.

Assessment of workplace air concentrations of formaldehyde during and before working hours in medical facilities

Workplace air concentrations of formaldehyde (FA) in medical facilities where FA and FA-treated organs were stored and handled were measured before and during working hours and assessed by the official method specified by Work Environment Measurement Law. Sixty-percent of the total facilities examined were judged as inappropriately controlled work environment. The concentrations of FA before working hours by spot sampling were found to exceed 0.1 ppm in some facilities, and tended to increase with increasing volume of containers storing FA and FA-treated materials. Regression analysis revealed that logarithmic concentrations of FA during working hours by the Law-specified analytical method were highly correlated with those before working hours by spot sampling, suggesting the importance for appropriate storing methods of FA and FA-treated materials. The concentrations of FA during working hours are considered to be lowered by effective ventilation of FA-contaminated workplace air and appropriate storage of FA and FA-treated materials in plastic containers in the medical facilities. In particular, such improvement by a local exhaust ventilation system and tightly-sealed containment of FA-treated material were urgently needed for the dissecting room where FA-treated cadavers were prepared and handled for a gross anatomy course in a medical school.

Quantitative assessment of occupational exposure to total indium dust in Japanese indium plants

This study quantitatively assessed personal exposure of 86 workers to indium compounds as total dust at 11 Japanese indium plants. The personal exposures to indium concentrations in the breathing zone during an 8 h work-shift were determined by ICP-MS. The arithmetic mean indium concentration of all the workers was 0.098 mg Indium (In)/m3, with individual values ranging from 0.0001 to 1.421 mg In/m3. There were 11 workers whose exposure to indium concentrations exceeded the American Conference of Governmental Industrial Hygienists’ Threshold Limit Value-Time Weighted Average (TLV-TWA) of 0.1 mg In/m3. Based on the condition TLV-TWA<X95 (upper 95th percentile of log-normal distribution), five indium plants were judged as “control measures required”, while 3 other plants were evaluated as “control measures not required”. Five workers belonging to the worst group were exposed to far higher indium concentrations than the TLV-TWA. Another group of 5 workers belonging to the best group was exposed to far lower indium concentrations than the TLV-TWA, and this was attributed to the stringent engineering control measures used at their workplaces. The quantitative assessment of occupational exposure to indium dust was influenced by different occupational exposure limit values without carcinogenicity and particle size-selectivity of indium particulates or “total” dust.

Evaluation of personal exposure of workers to indium concentrations in total dust and its respirable fraction at three Japanese indium plants

This study aimed to evaluate personal exposures of 27 workers to indium compounds as “total” dust and its “respirable” fraction in their breathing zones at 3 Japanese indium plants. Eight-hour time-weighted average (TWA) indium concentrations of personal exposure to dust collected in sampling periods of 6 h or longer were determined by ICP-MS. The arithmetic means of exposure concentrations were 0.095 mg indium (In)/m3, when sampled as total dust, and 0.059 mg In/m3, as respirable fraction. ACGIH’s TLV-TWA of 0.1 mg In/m3 for total particulate matter and Acceptable Exposure Concentration Limit (AECL) of 3×10−4 mg In/m3 for the respirable fraction notified by the Japanese Ministry of Health, Labour and Welfare were used to evaluate the exposure concentrations. Twenty-five out of 27 workers were exposed to indium concentrations lower than TLV-TWA, while all of the workers were exposed to the indium concentrations higher than AECL. We noted that there was a large discrepancy between the two occupational exposure limits referred to in this report, and these differences were attributed to the sampling strategies and health effects used as the prevention targets. Carcinogenicity of the respirable fraction of indium-containing particulates was considered in setting AECL, whereas it was not in ACGIH’s TLV.

Comparison of Sensitivity of Escherichia coli WP2 Tester Strains with and without TolC Outer Membrane Transport Protein Mutation in Detecting Chemical Mutagens

We compared the sensitivity of new Escherichia coli tester strains having the TolC outer membrane transport protein mutation (tolC strain), viz., WP2tolC, WP2tolC/pKM101, WP2uvrA, tolC and WP2uvrA, tolC/pKMO101, with E. coli strains not carrying this mutation (non-tolC strain), i.e., WP2, WP2/pKM101, WP2uvrA and WP2uvrA/pKM101, by measuring the specific activity (revertants/mg) of mutagens using a preincubation method. The tolC strains were more sensitive to polycyclic and heterocyclic compounds such as 2-aminoanthracene, 2-nitrofluorene, Glu-P-1, benzo[a]pyrene, mitomycin C, streptonigrin and doxorubicin than the non-tolC strains. Mutagenicity of 2-nitrofluorene was not detected by non-tolC strains WP2, WP2/pKM101 and WP2uvrA, but was detected by their tolC counterpart strains WP2tolC, WP2tolC/pKM 101 and WP2uvrA, tolC. However, these tolC strains were less mutagenic to streptozotocin or cisplatin than that of parent strains. Mutagenicity of 9-beta-D-arabinofuranoside was also not detected by the tolC strain WP2uvrA, tolC/pKM101, but was detected by the non-tolC strain WP2uvrA/pKM101. The enhancing effects of the mutagen detecting sensitivity by TolC outer membrane transport protein mutation were clearly observed with the low sensitivity strain WP2, but less clearly with the high sensitivity strain WP2uvrA/pKM101.