<p>Airborne fungal load is a major driving factor for asthmatic and allergenic immune responses. The present study aims to classify the health risk rating scale of two selected slum areas located in the humid tropical zone of the Kolkata metropolitan. Fungal load was assessed for six consecutive months in 20 different households in each selected location (<i>n</i> = 480). The health risk rating was calculated based on fungal concentration, diversity, and dominance, as well as the exposure time &amp; age of the residents, and most importantly, the presence of indoor fungal growth-promoting factors. High fungal load in the range of 7775–27,000 CFU/m³ in aerosols and 7200–14,000 CFU/m³ in house dust samples was observed, higher in the Topsia slum area, followed by Bantala. Microscopic characterization revealed the dominance of <i>Aspergillus</i> spp. in both aerosol and house dust followed by <i>Fusarium</i> spp., <i>Cladosporium</i> spp., and <i>Neurospora</i> spp. in aerosols and <i>Trichoderma</i> spp. in house dust samples. Both slum locations were observed to be in high-risk zones with an average health risk rating of &gt; 90, both as aerosol as well as house dust samples. Slum residents are at high health risk, and necessary measures should be taken to avoid the adverse health impacts. Proper waste management, minimizing or eliminating burning fossil fuels, maintaining proper ventilation, cleanliness, and hygiene are recommended to reduce the microbial load and sustain human health.</p>