Analysis of perfluoroalkyl carboxylates in vacuum cleaner dust samples in Japan

Perfluorooctanoic acid (PFOA) has long been an environmental contaminant of concern owing to its potential health risk. However, exposure to perfluorinated carboxylic acids (PFCAs) other than PFOA is not well understood. In this study, we investigated the concentrations of PFCAs in vacuum cleaner dust in Japan to measure the PFCAs contamination in an indoor environment. Most of the 77 samples contained PFCAs with 6-13 carbon atoms. The median concentration of perfluorononanoic acid (PFNA, 23.2 ng g⁻¹) was highest among PFCAs, followed by PFOA (20.8 ng g⁻¹) and perfluoroundecanoic acid (PFUnDA, 12.9 ng g⁻¹). The 90th percentile concentrations of PFNA, PFUnDA and perfluorotridecanoic acid (PFTrDA) were 948, 283 and 110 ng g⁻¹, respectively, and these were detected at greater concentrations than neighboring, even-numbered PFCAs. The proportion of long-chain PFCAs in vacuum cleaner dust from Japan was relatively higher than those reported for other countries. Factor analysis showed three independent factors. Odd-numbered long chain PFCAs (PFNA, PFUnDA and PFTrDA), which can correspond to factor 1, were major components of PFCAs in vacuum cleaner dust. Short chain PFCAs (factor 2) and even numbered long chain PFCAs (factor 3) were also statistically separated. These findings suggest that there are several sources of PFCAs with different origins in indoor environment. Further investigations into the origins of PFCAs are needed to evaluate indoor contamination with PFCAs.     

Mechanism of Depolymerization Reaction of Polyethylene Terephthalate: Experimental and Theoretical Studies

The depolymerization reaction of polyethylene terephthalate (PET) was analyzed on the basis of both experimental data and numerical data obtained from quantum chemistry calculations. Various alcohols were used as solvents in the search for the reaction mechanism. The activation energy obtained from the optimized structures of the ground state and the transitional state was compared with our experimental data. Based on these comparisons, it was found that the formation of rings from alkoxyl groups and carbonyl carbon atoms at the transitional state is highly important when the ester bonds of PET are broken. Moreover, the most appropriate alcohol was suggested for the depolymerization reaction.     

Occupational noise exposure and hearing defects among sawmill workers in the south of Thailand

The aim of this study was to investigate occupational noise exposure and hearing defects among sawmill workers in the south of Thailand. Seven hundred sawmill workers participated, of which 335 (47.9%) were male. The mean age of the sawmill workers was 33.5 years (SD 10.2), and more than 60% were <35 years old; 75.1% of the workers had less than 5 years of work experience. Only about one in four workers (25%) had been trained in use of personal protective equipment (PPE), and half of the participants never or rarely wore PPE while working. The prevalence rate of noise-induced hearing loss (NIHL) was 22.8% (N?=?42). Male workers had significantly higher risk than female workers (odds ratio [OR]?=?2.21). Workers aged older than 25 years had significantly higher risks for NIHL (OR?=?3.51–12.42) than workers younger than 25 years. Sawing workers had higher risk for NIHL than office workers (OR?=?3.07).     

Diffusion mechanism of chloride ions in sodium montmorillonite

For safety assessment of geological disposal of HLW, it is necessary to understand the diffusion mechanism of radionuclides in compacted bentonite. In this study, the diffusion behavior of chloride ions in compacted montmorillonite was studied from the viewpoints of the activation energy for apparent diffusion and the basal spacing of the compacted montmorillonite. A unique change in the activation energy as a function of the dry density of the montmorillonite was found. The activation energy decreased from 17.4 to 13.5 kJ mol-1 as the dry density increased from 0.7 to 1.0 Mg m-3 and increased to 25.1 kJ mol-1 at dry densities above 1.0 Mg m-3. The basal spacing of 1.88 nm, corresponding to the three-water layer hydrate state, was not observed by X-ray diffraction (XRD) until the dry density increased to 1.0 Mg m-3, where the minimum activation energy was obtained. On the other hand, a basal spacing of 1.56 nm, corresponding to the two-water layer hydrate state, was observed at the dry densities of 1.4 Mg m-3 and above, where the activation energies were more than 22 kJ mol-1. These experimental results suggest that there are at least two additional diffusion processes that can raise or reduce the activation energy and are affected by water in the region adjacent to the montmorillonite surfaces. If the "Grahame model" can be introduced to describe the electrical double layer, surface diffusion will be considered the possible predominant diffusion process, even for anions like chloride ions.     

Polyfluorinated telomers in indoor air of Japanese houses

The fluorotelomer alcohols (FTOHs) have been detected in various environmental compartments, including indoor and outdoor air, in North America and Europe. In our previous studies, FTOHs were detected at a relative higher concentration in outdoor air in the Keihan (Kyoto–Osaka, one of the major industrial zones) area, Japan compared to reported data. The exposure level of FTOHs in indoor air in the Keihan area remains unclear. In the present study, indoor air FTOH concentrations were investigated using a passive air sampler containing activated carbon felts. The indoor air sampling was conducted in 49 households of the Keihan area, during winter and summer 2008. Most samples contained 6:2 FTOH, 8:2 FTOH, 10:2 FTOH and 8:2 FTOAc. The median concentration of 8:2 FTOH (5.84 ng m^?3) was highest among fluorotelomers, followed by those of 10:2 FTOH (1.12 ng m^?3), 6:2 FTOH (0.29 ng m^?3), and others. Significant correlations among fluorotelomers were observed in collected samples. The association between housing conditions and 8:2 FTOH concentrations showed that samples collected from bed rooms have higher 8:2 FTOH concentrations than those collected from other locations. In addition, samples collected in winter showed lower levels of 8:2 FTOH than those collected in summer. These findings suggest that 8:2 FTOH is the predominant component among fluorotelomers in indoor air, and that there are emission sources of fluorotelomers in indoor environments of the Keihan area. Further investigations into the origins of fluorotelomers are needed to evaluate indoor contamination with fluorotelomers.     

Occurrence of perfluorinated carboxylic acids (PFCAs) in personal care products and compounding agents

Perfluorinated carboxylic acids (PFCAs), including perfluorooctanoic acid (PFOA), are persistent organic pollutants that pose human health risks. However, sources of contamination and exposure pathways of PFCAs have not been explored. In this study, PFCA concentrations were quantified in personal care products. Among 24 samples that listed fluorinated compounds, such as polyfluoroalkyl phosphate esters (PAPs), in their international nomenclature of cosmetic ingredients (INCI) labels, 21contained PFCAs (13 of 15 cosmetic samples, and 8 of 9 sunscreen samples). The concentrations of total PFCAs ranged from not detected to 5.9 μg g⁻¹ for cosmetics and from not detected to 19 μg g⁻¹ for sunscreens. We also investigated components of PFCAs in cosmetics and sunscreens. Commercially available compounding agents, mica and talc, which were treated with PAPs were analyzed and high concentrations of PFCAs were detected (total PFCAs 2.5 μg g⁻¹ for talc treated with PAPs, 35.0 μg g⁻¹ for mica treated with PAPs). To the best of our knowledge, this is the first report on contamination of end consumer products containing PAPs with high concentrations of PFCAs.     

Large-scale evaluation of the current level of polybrominated diphenyl ethers (PBDEs) in breast milk from 13 regions of Japan

Polybrominated diphenyl ethers (PBDEs) were measured in 2004 in 105 breast milk samples collected from 13 regions of Japan (Hokkaido, Akita, Miyagi, Tokyo, Gifu, Fukui, Kyoto, Hyogo, Wakayama, Shimane, Yamaguchi, Kochi and Okinawa). Six congeners (BDE-28, BDE-47, BDE-99, BDE-100, BDE-153 and BDE-154) were determined by gas chromatography /mass spectrometry (GC/MS). Total PBDE levels ranged from 0.01 to 23.0 ng/g lipid (geometric mean (GM), 1.34 ng/g lipid). BDE-47 (GM, 0.66 ng/g lipid, 59% of sigmaPBDE) was the most abundant congener present in breast milk and was detected in 99% of the samples. Total PBDE levels were higher in northern Japan than in other regions. We analyzed the effects of occupation, age, smoking status, alcohol consumption and number of deliveries on total PBDE levels. None of these factors were significantly associated with the level of PBDEs. The present study revealed that the current level of exposure to PBDEs in Japan is lower than that in the USA or Sweden. GMs (ng/g lipid) (GSD, geometric standard deviation) and medians (ng/g lipid) of PBDE levels in each district are as follows: Hokkaido 2.70 (1.70), 2.74; Akita 4.49 (2.19), 5.44; Miyagi 1.77 (4.37), 1.11; Tokyo 1.39 (2.09), 1.63, Gifu 2.83 (4.79), 2.23; Fukui 1.05 (2.34), 1.18; Kyoto 1.31 (2.95), 1.33; Hyogo 1.02 (2.69), 0.88; Wakayama 1.33 (3.80), 1.70; Shimane 0.83 (2.51), 0.66; Yamaguchi 1.74 (2.82), 1.76; Kochi 0.50 (2.69), 0.74 and Okinawa 1.91 (2.75), 1.22. This is the first large-scale study of current PBDE levels in breast milk in Japan.