Fine particulate matters with a diameter of <2.5 µm (PM_2.5) adversely affect the respiratory and immune systems. However, the contributing factors to its health effects remain unclear due to the variety of the PM_2.5 components depending on the season and source. We aimed to investigate the differences in the effects of PM_2.5 extracts collected from Saitama during the different seasons on the respiratory and immune systems and to clarify the contributing factors to health effects of PM_2.5. PM_2.5 were collected by a filter at the Center for Environmental Science in Saitama (Kazo City, Saitama Prefecture) from April 2013 to March 2018 and were divided into aqueous and organic extracts. Chemical analyses revealed that the aqueous components in the autumn were significantly affected by open burning. The aqueous components of PM_2.5 caused a pro-inflammatory response, such as IL-6 release from antigen-presenting cells. The effects varied depending on the season, especially in the autumn. OC4 in PM_2.5 showed the highest positive correlation with the IL-6 release from antigen-presenting cells. These results suggest that the PM_2.5 aqueous components derived from open burning can cause a pro-inflammatory effect in antigen-presenting cells.

To evaluate photochemical oxidants in detail, the total peroxy acyl nitrates (PANs) analyzer based on the TD/CAPS technique (cavity attenuated phase shift spectroscopy combined with a thermal dissociation reactor) was utilized and continuous observations of PANs, O₃, NO₂ and NO were successfully conducted over three years in a suburban site in Tokorozawa, Saitama, Japan. In this study, the period from April 2023 to August 2024 was investigated in order to characterize the relationship between the PANs and total oxidants (PO=O₃+NO₂) over one year and to focus on the outstanding cases in the summer of 2024. As the result of a correlation analysis between daytime PANs and PO, it was indicated that high PO events could be seen under the following conditions: (1) sunny days, (2) high temperature, (3) low NO_x/NMHCs ratio (NO_x-limited regime for O₃), (4) sufficiently high PO intercepts and/or slopes for day-by-day regression lines between the PANs and PO, and (5) long lifetime of PAN due to high NO₂/NO ratios. Consequently, during the over-3-year continuous observations, the practical utility of the PANs analyzer was confirmed. It was also confirmed that the correlation between total PANs and PO could be promising for evaluating and capturing the situations of photochemical ozone, including outstanding ozone events.

The present study examined the effects of ammonium sulfate and ammonium hydrogen sulfate on human adenocarcinoma-derived alveolar basal epithelial A549 cells and human adenocarcinoma-derived lung epithelial Calu-3 cells at an air-liquid interface. The exposure concentrations were 1, 10 or 100 mg/m³ for the L, M or H group and the control group. The experiments involving the A549 cells showed that ammonium sulfate enhanced the oxidative stress markers, heme oxygenase-1 and glutathione (GSH) approximately 2-fold compared to the in control group. The experiments using Calu-3 cells showed that ammonium sulfate attenuated the inflammation marker, IL-8, in the L group and enhanced it in the M group, enhanced IL-6 in the M group and attenuated it in the H group, and enhanced GSH in the H group. Ammonium hydrogen sulfate had no effect on the A549 and Calu-3 cells. Although the possibility of inflammation was suggested in an ammonium sulfate exposure experiment, the concentration of the H group was 50,000 times higher than the average atmospheric concentration of ammonium sulfate in Tokyo. These results suggest that the effects on cultured cells at atmospheric concentration levels of ammonium sulfate and ammonium hydrogen sulfate are extremely weak.