Chinese researchers have undertaken an assessment of stand-alone portable air purifiers. These types of devices are being used on a wider basis to address dust inside homes and especially in areas where outdoor pollution levels are high. While there are different views about the effectivness of such devices, the use of fixed or portable units has become a popular means of controlling individual inhalation exposure. Many such devices use high efficiency particulate air (HEPA) fiters.
However, there are concerns in general about exposure to bacterial endotoxins and the role these cellular fragments play in relation to respiratory inhalation health (triggering conditions such as asthma, especially as endotoxin exacerbates asthma). For example, a Japanese study published in 2020 found that endotoxin in outdoor air is significantly associated with an increased risk of asthma exacerbation in children.
Of concern to the researchers from Beihang University, Beijing, is the impact of indoor air purifiers. The researchers looked at changes in endotoxin levels in indoor air before and after purification by a portable air purifying devices.
The results showed an increase in endotoxins after a previously used air purifier was turned on in order to clean indoor air. This led the researchers to conlude that the use of air purifier devices could lead to increased endotoxin deposition in airways when used in the home. The particular physioogical area of concern was the alveolar region.
In terms of why this should be the case, the scientists demonstrated that endotoxin concentrations on the HEPA filters were strongly correlated with the free DNA concentrations on the HEPA filters. This correlation indicates that bacteria disrupted by the HEPA filter (which is designed to capture bacteria and pollutants like pollen) led to the release of free bacterial DNA and endotoxins.
Hence, HEPA filters are a source of indoor airborne endotoxins and could have an association with different respiratory diseases.
The research has been published in the journal Environment International. The research paper is titled “Indoor air filtration could lead to increased airborne endotoxin levels.”