池上 昭彦

Focusing on the relatively unexplored presence of micro- and nano-plastic aerosol particles, this study quantitatively assessed the emission of nano-plastic particles during the machining of carbon fiber reinforced plastic (CFRP) in the working environment. Measurements of aerosol particles smaller than 1 µm in size were performed by aerosol mass spectrometry. The findings revealed that concentrations of carbonous aerosol particles (organic aerosol and refractory black carbon (rBC)) were higher during working hours than during non-working hours. Positive matrix factorization identified CFRP particles as a significant source, contributing an average of approximately 30% of concentration of carbonous aerosol particles during working hours. This source apportionment was corroborated by the presence of bisphenol A and F fragments, principal components of the epoxy resins used in CFRP, and was corroborated by similarities to the carbon cluster ion distribution observed in rBC during CFRP pipe-cutting operations. Further, the particle size distribution suggested the existence of plastic aerosol particles smaller than 100 nm. This study established the method to quantitatively distinguish nano-plastic aerosol particles from other aerosol particles in high temporal resolution and these techniques are useful for accurately assessing exposure to nano-plastic aerosol particles in working environments.

OBJECTIVES: Carbon fibers are used in a variety of industrial applications, based on their lightweight and high stiffness properties. There is little information on the characteristics and exposure levels of debris generated during the factory processing of carbon fibers or their composites. This study revisits the general assumption that carbon fibers or their debris released during composite processing are considered safe for human health. METHODS: The present interventional study was conducted at a factory located in Japan, and involved on-site collection of debris generated during the industrial processing of polyacrylonitrile (PAN)-based carbon-fiber-reinforced plastic (CFRP). The debris were collected before being exhausted locally from around different factory machines and examined morphologically and quantitatively by scanning electron microscopy. The levels of exposure to respirable carbon fibers at different areas of the factory were also quantified. RESULTS: The collected debris mainly contained the original carbon fibers broken transversely at the fiber's major axis. However, carbon fiber fragments morphologically compatible with the WHO definition of respirable fibers (length: > 5 μm, width: < 3 μm, length/width ratio: > 3:1) were also found. The concentrations of respirable fibers at the six examined factory areas under standard working conditions in the same factory were below the standard limit of 10 fibers/L, specified for asbestos dust-generating facilities under the Air Pollution Control Law in Japan. CONCLUSIONS: Our study identified potentially dangerous respirable fibers with high aspect ratio, which was generated during the processing of PAN-based CFRP. Regular risk assessment of carbon fiber debris is necessary to ensure work environment safety.

BACKGROUND: Allergen-specific immunoglobulins have a crucial role in allergic diseases. Most wheeze episodes develop before school age, and allergic rhinitis later develops during early elementary school years. However, the clinical background and cytokine/chemokine profiles associated with changes in immunoglobulins during early school-age are poorly understood. METHODS: This study used blood samples from children participating in the JECS Pilot Study. We examined nineteen kinds of aeroallergen-specific immunoglobulins (IgE, IgG1, IgG4, and IgA) levels in patients at age 6 and age 8. Fluctuations of Der f 1- and Cry j 1-specific immunoglobulins levels during the two periods were compared to assess the frequency of allergic statuses and clusters of cytokine/chemokine profiles. RESULTS: The medians of aeroallergen-specific IgE levels did not fluctuate, and almost all IgG1 and IgG4 decreased. In IgA, four (e.g., Der f 1) increased, whereas the other four (e.g., Cry j 1) decreased. The ratio of the Der f 1-specific IgG1 level at age 8 to that at age 6 was higher in children with poor asthma control than in children with better asthma control. Moreover, the cytokine/chemokine cluster with relatively lower IL-33 and higher CXCL7/NAP2 was associated with lower Der f 1- and Cry j 1-specific IgG4 levels, but not IgE levels. CONCLUSIONS: The cluster of cytokine/chemokine profiles characterized by lower IL-33 and higher CXCL7/NAP2 was associated with the maintenance of aeroallergen-specific IgG4 levels. This result provides a basis for considering the control of aeroallergen-specific immunoglobulins.