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Most fine ambient particulate matter (PM_2.5)-based epidemiological models use globalized concentration-response (CR) functions assuming that the toxicity of PM_2.5is solely mass-dependent without considering its chemical composition. Although oxidative potential (OP) has emerged as an alternate metric of PM_2.5toxicity, the association between PM_2.5mass and OP on a large spatial extent has not been investigated. In this study, we evaluate this relationship using 385 PM_2.5samples collected from 14 different sites across 4 different continents and using 5 different OP (and cytotoxicity) endpoints. Our results show that the relationship between PM_2.5mass vs. OP (and cytotoxicity) is largely non-linear due to significant differences in the intrinsic toxicity, resulting from a spatially heterogeneous chemical composition of PM_2.5. These results emphasize the need to develop localized CR functions incorporating other measures of PM_2.5properties (e.g., OP) to better predict the PM_2.5-attributed health burdens.

 

Understanding the movement of antimicrobial resistance genes (ARGs) in the environment is critical to managing their spread. To assess potential ARG transport through the air via urban bioaerosols in cities with poor sanitation, we quantified ARGs and a mobile integron (MI) in ambient air over periods spanning rainy and dry seasons in Kanpur, India ( n = 53), where open wastewater canals (OCWs) are prevalent. Gene targets represented major antibiotic groups—tetracyclines ( tetA ), fluoroquinolines ( qnrB ), and beta-lactams ( bla TEM )—and a class 1 mobile integron ( intI1 ). Over half of air samples located near, and up to 1 km from OCWs with fecal contamination ( n = 45) in Kanpur had detectable targets above the experimentally determined limits of detection (LOD): most commonly intI1 and tetA (56% and 51% of samples, respectively), followed by bla TEM (8.9%) and qnrB (0%). ARG and MI densities in these positive air samples ranged from 6.9 × 10 1 to 5.2 × 10 3 gene copies/m 3 air. Most (7/8) control samples collected 1 km away from OCWs were negative for any targets. In comparing experimental samples with control samples, we found that intI1 and tetA densities in air are significantly higher ( P = 0.04 and P = 0.01, respectively, alpha = 0.05) near laboratory-confirmed fecal contaminated waters than at the control site. These data suggest increased densities of ARGs and MIs in bioaerosols in urban environments with inadequate sanitation. In such settings, aerosols may play a role in the spread of AR. 

Abstract In India, high rates of antibiotic consumption and poor sanitation infrastructure combine to pose a significant risk to the public through the environmental transmission of antimicrobial resistance (AMR). The WHO has declared extended-spectrum beta-lactamase (ESBL)-positive Escherichia coli a key indicator for the surveillance of AMR worldwide. In the current study, we measured the prevalence of AMR bacteria in an urban aquatic environment in India by detecting metabolically active ESBL-positive E. coli. Water samples were collected in duplicate from 16 representative environmental water sources including open canals, drains, and rivers around Kanpur, Uttar Pradesh. We detected culturable E. coli in environmental water at 11 (69%) of the sites. Out of the 11 sites that were positive for culturable E. coli, ESBL-producing E. coli was observed at 7 (64%). The prevalence of ESBL-producing E. coli detected in the urban aquatic environment suggests a threat of AMR bacteria to this region. 

Little is known about microbial communities in the Ganges River, India and how they respond to intensive anthropogenic inputs. Here we applied shotgun metagenomics sequencing to study microbial community dynamics and function in planktonic samples collected along an approximately 700 km river transect, including urban cities and rural settings in upstream waters, before and after the monsoon rainy season. Our results showed that 11%–32% of the microbes represented terrestrial, sewage and human inputs (allochthonous). Sewage inputs significantly contributed to the higher abundance, by 13‐fold of human gut microbiome (HG) associated sequences and 2‐fold of antibiotic resistance genes (ARGs) in the Ganges relative to other riverine ecosystems in Europe, North and South America. Metagenome‐assembled genome sequences (MAGs) representing allochthonous populations were detectable and tractable across the river after 1–2 days of (downstream) transport (> 200 km apart). Only approximately 8% of these MAGs were abundant in U.S. freshwater ecosystems, revealing distinct biodiversity for the Ganges. Microbial communities in the rainy season exhibited increased alpha‐diversity and spatial heterogeneity and showed significantly weaker distance‐decay patterns compared with the dry season. These results advance our understanding of the Ganges microbial communities and how they respond to anthropogenic pollution.