PFASs significantly altered swimming behaviour in zebrafish embryos. Some short-chain PFASs caused behaviour toxicity, but not acute toxicity. A PFAS mixture was less potent than some individual PFASs. Bioconcentration factor (BCF) after six days was 0.9e2700 for individual PFASs. Toxicity and BCF were related to perfluorocarbon chain length and functional group.

No abstract

Very high levels of a range of pharmaceuticals have been reported recently in the effluent from a wastewater treatment plant near Hyderabad, India. The plant serves approximately 90 manufacturers of bulk drugs that primarily are exported to the world market. Fluoroquinolone antibiotics were found at levels that are highly toxic to various microorganisms. Even though milligram-per-liter levels of drugs targeting human proteins also have been found, it is difficult to conclude whether these levels are sufficiently high to adversely affect fish or amphibians due to the lack of relevant chronic toxicity data for most human pharmaceuticals. To assess potential effects on aquatic vertebrates, tadpoles of Xenopus tropicalis were exposed to three dilutions of effluent (0.2, 0.6, and 2%) over 14 d, starting at developmental stage 51. Additionally, newly fertilized zebrafish (Danio rerio) were exposed to diluted effluent in 96-well plates for up to 144 h postfertilization (hpf). The tadpoles' body lengths, weights, and developmental stages were recorded, whereas a larger number of sublethal and lethal endpoints were studied in the zebrafish. A 40% reduced growth of the exposed tadpoles was demonstrated at the lowest tested effluent concentration (0.2%), indicating potent constituents in the effluent that can adversely affect aquatic vertebrates. The median lethal concentration (LC50) for zebrafish at 144 hpf was between 2.7 and 8.1% in different experiments. Reduced spontaneous movements, pigmentation, and heart rate were recorded within 48 hpf at 8 and 16% effluent concentrations. Treated effluent from a plant that serves as an important link in the global supply chain for bulk drugs is thus shown to cause adverse effects to aquatic vertebrates even at very high dilutions.

No abstract

Antimicrobial resistance (AMR) is a major threat to global health. Understanding the emergence, evolution, and transmission of individual antibiotic resistance genes (ARGs) is essential to develop sustainable strategies combatting this threat. Here, we use metagenomic sequencing to analyse ARGs in 757 sewage samples from 243 cities in 101 countries, collected from 2016 to 2019. We find regional patterns in resistomes, and these differ between subsets corresponding to drug classes and are partly driven by taxonomic variation. The genetic environments of 49 common ARGs are highly diverse, with most common ARGs carried by multiple distinct genomic contexts globally and sometimes on plasmids. Analysis of flanking sequence revealed ARG-specific patterns of dispersal limitation and global transmission. Our data furthermore suggest certain geographies are more prone to transmission events and should receive additional attention.