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. 2025 Jul 24:13:1626827.
doi: 10.3389/fpubh.2025.1626827. eCollection 2025.

Microbial indoor air pollution in Delhi Metropolitan City is attributable to severe respiratory and general health effects among residents

Pradeep Kumar  1   2 , Rajeev Singh  1   3
Affiliations

Microbial indoor air pollution in Delhi Metropolitan City is attributable to severe respiratory and general health effects among residents

Pradeep Kumar et al. Front Public Health. .

Abstract

Indoor air quality plays a crucial role in the health and well-being of residents. Delhi, known as one of the most polluted cities globally, often receives insufficient attention in managing and mitigating related health impacts. This study isolated, characterized, and assessed microbial indoor air quality (bioaerosols) using multiproxy approaches and correlated findings with associated health effects. The spatial variation of bacterial aerosols showed irregular patterns, increasing from winter to summer and decreasing in fall; fungal aerosols consistently increased from winter to fall. Bacterial aerosol concentrations ranged from 730 to 5,300 CFU/m3, while fungal concentrations were between 1,330 and 6,050 CFU/m3, significantly exceeding the recommended limits. The size distribution of fungal aerosols varied across seasons, with higher concentrations in the 4th and 5th stages of the sampler. Several airborne bacterial and fungal genera, including Staphylococcus, Streptococcus, Micrococcus, Aspergillus, Penicillium, and Cladosporium, were identified in homes. Health effects were most pronounced in winter followed by fall, with symptoms such as headaches, eye irritation, allergic rhinitis, coughing, and sneezing being common. As per this study, there may be a correlation between indoor bioaerosol concentrations, seasonal variations, and health outcomes, though further in-depth in vitro, exposure assessment, and epidemiological studies are necessary to substantiate these findings.

Keywords: bacteria; fungi; indoor air quality; questionnaire survey; respiratory problems.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Figure 1
Figure 1
Simplified overview of the methodology used for bioaerosol sampling and analysis (Created with BioRender.com).
Figure 2
Figure 2
Schematic presentation of the comparison of size distribution of Andersen impactor with human respiratory system (54). (Created with BioRender.com).
Figure 3
Figure 3
Seasonal concentration of culturable bioaerosols indoor places. (a) Bacteria (b) Fungi. n = 336 samples in all seasons (84 each season); Error bars represent SD of triplicates.
Figure 4
Figure 4
Size distribution in different seasons. (a) Bacterial. (b) Fungi.
Figure 5
Figure 5
Proportion of microbes isolated from indoor residential houses. (a) Bacteria. (b) Fungi.
See this image and copyright information in PMC

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