Environmental determinants and microbial association of outdoor atmospheric antibiotic resistance genes

Despite broad recognition of antimicrobial resistance (AMR) as a major planetary health challenge, atmospheric antibiotic resistance genes (ARGs) remain an overlooked pathway for global dissemination. Unlike indoor air, which poses direct exposure risks to individuals, outdoor environments serve as planetary-scale reservoirs where particulate matter (PM), gaseous pollutants, heavy metals, and meteorological dynamics collectively influence the abundance and mobility of resistance determinants. This systematic review synthesizes evidence from 2015 to 2025 to assess the spatiotemporal distribution, environmental drivers, and microbial associations of atmospheric ARGs in outdoor air. Absolute concentrations of atmospheric ARGs peak in winter, coinciding with elevated PM and heating emissions, whereas relative abundances increase in spring and summer, reflecting the selective persistence of resistant taxa under seasonal stressors. Urban regions exhibit the highest ARG levels, dominated by clinically relevant genes such as the tetracycline-resistance gene ( tetA ) and the sulfonamide-resistance gene ( sul1 ), while rural and livestock settings are enriched with tetA and sul1 associated with agricultural practices. Network analyses indicate frequent co-occurrence between atmospheric ARGs/MGEs and bacterial taxa, including Pseudomonas and Acinetobacter , suggesting that outdoor aerosols may provide ecological contexts for ARG persistence or potential gene exchange. As climate change, urbanization, and intensive agriculture alter air quality and atmospheric circulation, outdoor atmospheric ARGs may exacerbate inequities in the AMR burden, especially in low- and middle-income countries where monitoring remains limited. Recognizing outdoor air as a neglected domain in AMR control is therefore urgent, requiring integration of ARG surveillance into global air-quality and “One Health” frameworks.