Moldy odor from air conditioners in the residences of Japanese participants with and without asthma

Abstract

Fungi are a major environmental allergen. 1 Exposure and sensitization to environmental fungi are associated with asthma onset, severity, and exacerbation. 2 Furthermore, fungi pose a risk for the development of more severe conditions such as allergic bronchopulmonary aspergillosis/mycosis (ABPA/ABPM). An estimation of the global burden suggested that ABPA develops in approximately five million patients with asthma worldwide. 3 As more time is spent at home in the era of the coronavirus disease 2019 (COVID-19) pandemic, appropriate maintenance of the indoor environment is essential for the health of patients with asthma. However, less is known regarding environmental interventions to reduce indoor molds and their efficacy compared with the approaches for another major indoor allergen, house dust-mites. 4 Mold growth is affected by temperature, relative humidity, and ventilation. Therefore, heating, ventilating, and air-conditioning (HVAC) systems are beneficial for reducing the burden of airborne fungi. 5 However, if not properly maintained, air conditioners themselves can be contaminated with fungi and, consequently, spread fungal spores into indoor air. 6,7 We previously reported a case of ABPM with repeated deterioration due to recurrent exposure to

A Method to Evaluate and Eliminate Fungal Contamination in Household Air Conditioners

“…Airborne fungal concentration increases from 40-920 to 5,500-100,000 colony-forming units•m -3 immediately after the operation of household ACs [17]. In our online survey, 37.1% of 1,006 Japanese participants reported a moldy odor from household ACs indicating fungal contamination [20]. ACs contaminated with fungi can impact the health outcomes of patients with allergic fungal airway diseases.…”

“…Fungal abundance and composition were examined in the ACs of living rooms in the present study because Japanese residences are predominantly equipped with ACs in the living room (90.2%), followed by the bedroom (50.1%) [20]. Furthermore, a Canadian study reported that airborne spore concentrations were the highest in living rooms [31].…”

“…Several approaches have been employed to decontaminate household ACs. Approximately 80% of AC users perform some measures for AC maintenance [20]; among these, manual or automatic cleaning of filters is the easiest approach. Patients with asthma are more conscious regarding the maintenance of ACs and use biocidal detergent sprays more frequently than those without asthma [20].…”

“…Approximately 80% of AC users perform some measures for AC maintenance [20]; among these, manual or automatic cleaning of filters is the easiest approach. Patients with asthma are more conscious regarding the maintenance of ACs and use biocidal detergent sprays more frequently than those without asthma [20]. Notably, spraying the cleaner from the frontal side of heat exchangers may be ineffective, as fungal contamination in ductless minisplit AC units predominantly occurs in the downstream area of heat exchangers, as evidenced in the present study.…”

Assessing the impact of ventilation systems on indoor air quality: a mock-up experiment in Dubai

“…The apartment interiors were maintained at a room temperature of 24 °C using air conditioning, and a household humidifier was installed in the living room for humidification (Zhao et al, 2018). During the operation of the ventilation system, the indoor relative humidity did not reach 50% with a single household humidifier (Okada et al, 2022). However, considering using one humidifier per unit is common, only one humidifier was installed, and the humidification amount was set to the maximum.…”