Association between transported Asian dust and outdoor fungal concentration during winter in a rural area of western Japan.

Background: 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.

Methods: 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.

Results: Daily levels of AD particles were assessed using Light Detection and Ranging and did not correlate with outdoor fungi (r = -0.17,  0.94). There was also no association between outdoor fungi and the daily production of IL-6 (r = 0.16,  0.37), IL-8 (r = 0.19,  0.30), or TNF-α induced by collected PM (r = 0.07,  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,  0.0004), and TNF-α (r = 0.72,  < 0.0001) production.

Conclusion: 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.