Environmental exposure to active pharmaceutical ingredients (APIs) can have negative effects on the health of ecosystems and humans. While numerous studies have monitored APIs in rivers, these employ different analytical methods, measure different APIs, and have ignored many of the countries of the world. This makes it difficult to quantify the scale of the problem from a global perspective. Furthermore, comparison of the existing data, generated for different studies/regions/continents, is challenging due to the vast differences between the analytical methodologies employed. Here, we present a global-scale study of API pollution in 258 of the world’s rivers, representing the environmental influence of 471.4 million people across 137 geographic regions. Samples were obtained from 1,052 locations in 104 countries (representing all continents and 36 countries not previously studied for API contamination) and analyzed for 61 APIs. Highest cumulative API concentrations were observed in sub-Saharan Africa, south Asia, and South America. The most contaminated sites were in low- to middle-income countries and were associated with areas with poor wastewater and waste management infrastructure and pharmaceutical manufacturing. The most frequently detected APIs were carbamazepine, metformin, and caffeine (a compound also arising from lifestyle use), which were detected at over half of the sites monitored. Concentrations of at least one API at 25.7% of the sampling sites were greater than concentrations considered safe for aquatic organisms, or which are of concern in terms of selection for antimicrobial resistance. Therefore, pharmaceutical pollution poses a global threat to environmental and human health, as well as to delivery of the United Nations Sustainable Development Goals.

The oxidation mechanism of dimethyl ether is investigated using ab initio methods. The structure and energetics of reactants, products, and transition structures are determined for all pathways involved in the oxidation mechanism. The detailed pathways leading to the experimentally observed products of dimethyl ether oxidation are presented. The energetics of over 50 species and transition structures involved in the oxidation process are calculated with G2 and G2(MP2) energies. The principal pathway following the initial attack of dimethyl ether (CH 3 OCH 3 ) by the OH radical is the formation of the methoxymethyl radical (CH 2 OCH 3 ). Oxidation steps lead to the formation of methyl formate, which is consistent with the experimentally observed products. Oxidation pathways of methyl formate are also considered.

Abstract. Using recent kinetic data, two-dimensional (2-D) chemical-transport modeling of the atmospheric lifetimes of dimethyl ether and fluorinated ethers CH3OCF 3 (E143a), CHF2OCHF 2 (E134), and CHF2OCF3 (E125) shows that E134 and E125 have substantially larger lifetimes than previously estimated. Dimethyl ether has a short atmospheric lifetime of 5.1 days and a relatively insignificant radiative forcing leading to a relatively low global warming potential. Increasing fluorination is accompanied by slower rates of reaction with hydroxyl radical and ultimately longer lifetimes. E143a, E134, and E125 were found to have lifetimes of 5.7, 29.7, and 165 years, respectively. In addition, our work uses ab initio methodology to determine IR absorption cross sections for each ether. Our study finds that E134 and E125 have significant infrared absorption and thus relatively high radiative forcing values. These two properties together yield global warming potentials for E134 and E125 of 5720 and 14,000, respectively, integrated over a 100 year period.

Abstract. We have examined CF3OCF=CF 2 regarding its reactivity toward OH radical, its infrared spectroscopic properties, its atmospheric lifetime, and its radiative forcing. From these we then determined the Global Warming Potentials (GWPs) for CF3OCF=CF 2. The examination is completed using a combination of discharge flow coupled with mass spectrometer and resonance fluorescence (DF/MS/RF), Fourier transform infrared (FTIR) spectroscopy, ab initio molecular orbital calculation, and atmospheric and radiative transfer modeling. Mass spectral evidence suggests that both HF and CF3OCFC (

The atmospheric oxidation mechanisms of E143a (CF3OCH3), E134 (CHF2OCHF2), and E125 (CHF2OCF3) have been investigated using experimental and ab initio methodology. The oxidation of E143a produces the stable reservoir species trifluoromethyl formate, CF3OCOH, which further oxidizes to CF2O and CO2. Oxidation of E134 and E125 shows the presence of only CF2O under the condition of high O2 concentrations. Carbonyl fluoride can be formed from two competing pathways involving the halogenated alkyl radicals formed from hydrogen abstraction of E134 and E125. CO bond fission reactions and O2 addition reactions compete to produce carbonyl fluoride and a CF x H3 - x radical fragment. Computational modeling of the reaction pathways provides insight into the molecular steps of the degradation process.