Jun Kurai

The effect of ambient air pollutants and Asian dust (AD) on absence from school due to sickness has not been well researched. By conducting a case-crossover study, this study investigated the influence of ambient air pollutants and desert sand dust particles from East Asia on absence from school due to sickness. From November 2016 to July 2018, the daily cases of absence due to sickness were recorded in five elementary schools in Matsue, Japan. During the study period, a total of 16,915 absence cases were recorded, which included 4865 fever cases and 2458 cough cases. The relative risk of overall absence in a 10-μg/m³ increment of PM_2.5 and a 0.1-km⁻¹ of desert sand dust particles from East Asia were found with 1.28 (95%CI: 1.15–1.42) and 2.15 (1.04–4.45) at lag0, respectively. The significant influence of PM_2.5 persisted at lag5 and that of desert sand dust particles at lag2. NO₂ had statistically significant effects at lag2, lag3, and lag4. However, there was no evidence of a positive association of O_x and SO₂ with absence from school. These results suggested that PM_2.5, NO₂, and AD increased the risk of absence due to sickness in schoolchildren.

Experimental and controlled human exposure studies have demonstrated additive effects of ambient particulate matter and ozone on health. A few epidemiological studies have suggested that ambient particulate matter components are important for the combined effects of ambient particulate matter and ozone on health. However, few studies have examined whether ozone changes the effects of ambient particulate matter on pro-inflammatory cytokine production. In this study, the influence of ozone on pro-inflammatory cytokine production in response to ambient particulate matter was evaluated. Ambient particulate matter smaller than 1 μm was collected and the suspension of this particulate matter was bubbled through 0.12 ppm and 0.24 ppm ozone. THP1 cells were stimulated by the solution containing the particulate matter with and without bubbling through ozone at 1 μg/mL. The interleukin-8 concentrations in the supernatants of THP1 cells stimulated by collected particulate matter dissolved in solution were 108.3 ± 24.7 pg/mL without ozone exposure, 165.0 ± 26.1 pg/mL for 0.12 ppm ozone bubbling for 1 min, 175.1 ± 33.1 pg/mL for 0.12 ppm for 5 min, 183.3 ± 17.8 pg/mL for 0.12 ppm for 15 min, 167.8 ± 35.9 pg/mL for 0.24 ppm for 1 min, 209.2 ± 8.4 pg/mL for 0.24 ppm for 5 min, and 209.3 ± 14.3 pg/mL for 0.24 ppm for 15 min. Ozone significantly increased interleukin-8 concentrations compared to those for particulate matter dissolved in solution without ozone exposure and the solvent only (8.2 ± 0.9 pg/mL) in an ozone concentration-dependent manner. Collected particulate matter in solutions with or without bubbling through ozone had no effect on interleukin-6 production. The antioxidant N-acetyl-L-cysteine significantly inhibited the increases in interleukin-8 induced by solutions with particulate matter, regardless of ozone exposure. The reactive oxygen species concentration in solutions with collected particulate matter was not associated with ozone bubbling. Ozone may augment the production of interleukin-8 in response to ambient particulate matter by a mechanism unrelated to reactive oxygen species. These results support the epidemiological evidence for combined effects of ambient particulate matter and ozone on human health.

The adverse effects of Asian dust (AD) on health have been demonstrated in earlier studies, but there is no standardized definition for heavy–AD. This study aimed to examine which definition of heavy–AD has the most adverse effect on respiratory function. One–hundred–and–thirty–seven adults with asthma, and 384 school children self-measured their morning peak expiratory flow (PEF). The four definitions of heavy–AD are: (1) the definition provided by the Japan Meteorological Agency (JMA), (2) daily median AD particle level ≥ 0.07 km−1, obtained through light detection and ranging (LIDAR) (3) hourly AD particle level ≥ 0.1 km−1, and (4) hourly level ≥ 0.07 km−1. Linear mixed models were used to estimate the effects of heavy–AD, by definition type, on daily PEF values. In adults with asthma, as per the JMA’s definition, significantly reduced PEF were observed on heavy–AD days (lag 0), lag 0–1, and lag 0–3. In school children, after a heavy–AD event, as defined by the JMA, PEF significantly decreased on lag 0–1, lag 0–2, and lag 0–3. However, as per the other definitions, there was no significant decrease in the PEF in the adults and children. The associations between heavy–AD and respiratory function differed between these definitions.

Recently, Asian dust (AD) has become a serious health problem and several studies have clearly proven that AD can aggravate asthma. However, it remains unclear as to which components of AD have a strong effect on the asthma exacerbation caused by AD exposure. Outdoor fungi can increase emergency department visits and hospitalization for asthma exacerbation and can aggravate asthma symptoms. Therefore, this study was aimed at investigating the relationship between AD and outdoor fungi and determining the potential of fungi to cause airborne particulate matter (PM)-related inflammatory responses. Airborne PM was collected each day from January 26, 2015 to February 27, 2015. Daily levels of outdoor fungi-associated PM were calculated using a culture-based method. Production of cytokines such as interleukin (IL)-6, IL-8, and tumor necrosis factor (TNF)-α was assessed in THP1 cells stimulated by the collected airborne PM each day. Daily levels of AD particles were assessed using Light Detection and Ranging and did not correlate with outdoor fungi (r = −0.17, P = 0.94). There was also no association between outdoor fungi and the daily production of IL-6 (r = 0.16, P = 0.37), IL-8 (r = 0.19, P = 0.30), or TNF-α induced by collected PM (r = 0.07, P = 0.70). However, the daily levels of AD particles were significantly associated with IL-6 (r = 0.91, P < 0.0001), IL-8 (r = 0.64, P = 0.0004), and TNF-α (r = 0.72, P < 0.0001) production. AD did not increase the acute levels of outdoor fungi and outdoor fungi did not affect the cytokine production induced by airborne PM. These results suggest that outdoor fungi do not have any detectable effect on the asthma exacerbation caused by AD exposure.

Numerous studies have unmasked the deleterious effects of particulate matter less than 2.5 μm (PM_2.5) on health. However, epidemiologic evidence focusing on the effects of PM_2.5 on skin health remains limited. An important aspect of Asian dust (AD) in relationship to health is the amount of PM_2.5 contained therein. Several studies have demonstrated that AD can aggravate skin symptoms. The current study aimed to investigate the effects of short-term exposure to PM_2.5 and AD particles on skin symptoms in schoolchildren. A total of 339 children recorded daily skin symptom scores during February 2015. Light detection and ranging were used to calculate AD particle size. Generalized estimating equation logistic regression analyses were used to estimate the associations among skin symptoms and the daily levels of PM_2.5 and AD particles. Increases in the levels of PM_2.5 and AD particles were not related to an increased risk of skin symptom events, with increases of 10.1 μg/m³ in PM_2.5 and 0.01 km⁻¹ in AD particles changing odds ratios by 1.03 and 0.99, respectively. These results suggest that short-term exposure to PM_2.5 and AD does not impact skin symptoms in schoolchildren.

Asian dust (AD) can aggravate airway inflammation in asthma, but the association between AD and the development of asthma remains unclear. This study aimed to investigate the effects of AD on the early stage of antigen sensitization using a mouse model of asthma, as well as the role of leukotrienes (LTs) in antigen-induced airway inflammation potentiated by AD particles. NC/Nga mice were co-sensitized by intranasal instillation of AD particles and/or Dermatophagoides farinae (Df) for five consecutive days. Df-sensitized mice were stimulated with an intranasal Df challenge at seven days. Mice were treated with the type 1 cysteinyl LT (CysLT₁) receptor antagonist orally 4 h before and 1 h after the allergen challenge. At 24 h post-challenge, the differential leukocyte count, inflammatory cytokines, and LTs in bronchoalveolar lavage fluid were assessed, and airway inflammation was evaluated histopathologically. AD augmented neutrophilic and eosinophilic airway inflammation with increased CysLTs and dihydroxy-LT in a mouse model of asthma. The CysLT₁ receptor antagonist was shown to attenuate both neutrophilic and eosinophilic airway inflammation augmented by AD. Therefore, exposure to AD may be associated with the development of asthma and LTs may play important roles in airway inflammation augmented by AD.

The relationship between particulate air pollutants and respiratory symptoms in children has not been consistent among studies, potentially owing to differences in the inflammatory response to different particulate air pollutants. This study aimed to investigate the effect of particulate air pollutants on respiratory symptoms and the inflammatory response in schoolchildren. Three hundred-and-sixty children were included in the study. The children recorded daily respiratory symptom scores for October 2015. In addition, the daily amount of interleukin (IL)-6, IL-8, and tumor necrosis factor (TNF)-α production was assessed in THP1 cells stimulated with suspended particulate matter (SPM), which was collected every day during the study period. Generalized estimating equation logistic regression analyses were used to estimate the associations among respiratory symptoms and the daily levels of SPM, IL-6, IL-8, and TNF-α. Daily SPM levels were not associated with respiratory symptoms or the daily IL-6, IL-8, and TNF-α levels. Conversely, there was a significant association between respiratory symptoms and the daily IL-6, IL-8, and TNF-α levels. These results suggested that the effects of particulate air pollutants on respiratory symptoms in schoolchildren might depend more on the pro-inflammatory response to them than on their mass concentration.

This study aimed to investigate the effects of winter and spring particulate matter (PM) on airway inflammation and allergies in a mouse asthma model. PM was collected during 7–28 February 2013 (winter) and during 7–28 April 2013 (spring) in Yonago, Japan. NC/Nga mice were co-sensitized using intranasal instillation of the PMs and Dermatophagoides farinae (Df) for 5 consecutive days, and were subsequently challenged using intranasal Df at 7 days after the last sensitization. At 24 h after the challenge, serum immunoglobulin levels, differential leukocyte counts, and inflammatory cytokines levels were measured in the mice’s bronchoalveolar lavage fluid (BALF). Compared to co-sensitization using spring PM and Df, winter PM and Df induced greater increases in the BALF neutrophil and eosinophil counts and total serum IgE and IgG2a levels. Furthermore, winter PM-sensitized mice exhibited higher BALF levels of interleukin-5, interleukin-13, interleukin-6, and keratinocyte-derived chemokine. Therefore, we observed seasonal variations in the effects of PM on asthma-related airway inflammation. These findings suggest that the compositions of PM vary according to season, and that it is important to evaluate PM compositions in order to understand the associations between asthma and PM.

Outdoor fungi are important components of airborne particulate matter (PM). However, the associations between pulmonary function and outdoor fungi are less well known compared to other airborne PM constituents. The objective of this study was to investigate the association between outdoor fungi and pulmonary function in children. Morning peak expiratory flow (PEF) rates were measured daily in 339 schoolchildren (including 36 with asthma), aged 10 to 12, 2 to 27 February 2015. Airborne PM was collected on filters, using a high volume air sampler, each day during the study period. The daily concentration of outdoor fungi-associated PM was calculated using a culture-based method. A linear mixed model was used to estimate the association between PEF values and daily concentrations of outdoor fungi, and the daily levels of suspended PM (SPM) and PM ≤ 2.5 μm (PM_2.5). An increase in the interquartile range (46.2 CFU/m³) for outdoor fungal concentration led to PEF changes of −1.18 L/min (95% confidence interval, −2.27 to −0.08) in all children, 1.22 L/min (−2.96 to 5.41) in children without asthma, and −1.44 L/min (−2.57 to −0.32) in children with asthma. Outdoor fungi showed a significant negative correlation with PM_2.5 levels (r = −0.4, p = 0.04), but not with SPM (r = ‒0.3, p = 0.10) levels. Outdoor fungi may be associated with pulmonary dysfunction in children. Furthermore, children with asthma may show greater pulmonary dysfunction than those without asthma.

Although adult asthma is attributable to occupational factors, few reports are available on asthma prevalence among health care workers in Japan. The objective of this study was to estimate the prevalence of asthma and wheeze among Japanese nursing professionals. A cross-sectional study was conducted by postal survey using a translated version of the European Community Respiratory Health Survey questionnaire from April to June 2013. The analysis included 4634 nursing professionals (257 men and 4377 women) and the overall response rate was 84.8%. The prevalence of current asthma and wheeze were 10.7% (95% confidence interval (CI), 9.9%–11.7%) and 15.6% (95% CI, 14.5%–16.6%), respectively. More than one year of work experience as a nursing professional and more than one year of experience with bed-making tasks were associated with odds ratios (ORs) of 1.95 (95% CI, 1.12–3.39) and 1.64 (95% CI, 1.15–2.23) for wheeze, respectively. Current smoking was significantly associated with the presence of wheeze, with ORs of 2.27 for men (95% CI, 1.11–4.64) and 2.01 for women (95% CI, 1.54–2.64). Among female nurses, latex allergy was associated with wheeze (OR, 1.87; 95% CI, 1.56–2.23), as was body mass index ≥30 (OR, 2.76; 95% CI, 1.65–4.62). This study has provided the prevalence of asthma and wheeze among Japanese nursing professionals. Employment period, bed-making tasks, latex allergy, obesity, and smoking may be risk factors for prevalent wheeze among nursing professionals.