Waste sorting plants (WSPs) are integral to managing refuse and recycling but pose significant health risks to workers due to exposure to various microorganisms. Recent research published on March 15, 2025, utilized high-throughput sequencing (HTS) to characterize the microbial communities found within personal air samples collected at six contemporary WSPs across Norway. This groundbreaking study identified not only diverse microbial populations but also potential human pathogens, raising serious health concerns for those working in waste handling.
The study found substantial variations within and among the microbiomes of different plants, emphasizing the need for thorough risk assessments. Specifically, the research gathered 112 personal air samples, which revealed significant presence of harmful microorganisms. The survey noted Cladosporium sp. as the dominant fungal genus and Aerococcus sp. as the leading bacterial genus across the sampled workplaces. Alarmingly, these samples contained several potential human pathogens, including Aspergillus spp., Fusarium spp., and Enterobacteriaceae. Some of the identified strains are known to exhibit potential drug resistance, thereby increasing the health risks to exposed workers.
Despite previous studies primarily focusing on culturable organisms, the current research demonstrates the limitations of such approaches, which may underestimate microbial diversity. The findings, based on HTS methodology, revealed 63,637 merged non-chimeric bacterial reads, leading to the identification of 20,881 unique amplicon sequence variants (ASVs) and 30,345 merged non-chimeric fungal reads, leading to 2,231 unique fungal ASVs. This highlights the extensive diversity of the airborne microbiome and indicates the complexity of assessing its health impacts on workers.
Notably, this research did not find evidence supporting the notion of seasonality affecting microbial community composition within the WSPs. While fluctuations in environmental conditions can influence microbial communities, the study concluded the microbial diversity largely varied based on the waste material being sorted and the specific operations performed by workers. Therefore, the risk of exposure was fundamentally linked to the task at hand rather than seasonal variability.
High levels of bacterial ASVs, which accounted for 68% of the microbial load compared to fungi at about 32%, highlight the necessity for targeted health assessments, particularly considering the presence of pathogenic bacteria such as Staphylococcus aureus. The latter was detected across all WSPs and is recognized for its potential multi-drug resistance, prompting concerns about its health impact. The fungus Fusarium, often associated with infections, was also found within the air samples, summing to 5 different fungi outlined by the World Health Organization (WHO) as priority pathogens.
The diversity of microbial communities encountered varied significantly between the plants. Analyses showed alpha diversity metrics indicating significant differences between certain sites, reflecting how microbial populations are affected by the handling processes at each plant. These findings demonstrate the importance of monitoring airborne microbiomes using advanced sequencing techniques, such as HTS, to not only assess risks but to potentially inform workplace safety practices.
This study's findings provide significant insights for health professionals and employers within the waste management sector by underscoring the uniquely variable and potentially harmful exposure risks faced by workers. With the current reliance on HTS, which has significantly broadened the scope of microbial detection, it is recommended to implement improved ventilation and personal protective equipment based on the findings to mitigate the risks associated with waste sorting tasks.
Looking forward, researchers advocate for continued exploration to identify seasonal patterns and broader microbial diversity through even more advanced techniques. Further studies must address environmental variables such as humidity and temperature's impact on microbial exposure to develop comprehensive protective strategies for waste sorting personnel.