Elimination of antibiotic resistance genes and control of horizontal transfer risk by UV-based treatment of drinking water: A mini review

Antibiotic-resistant bacteria and antibiotic resistance genes are in water bodies. UV/chlorination method is better to remove ARGs than UV or chlorination alone. Research on UV/hydrogen peroxide to eliminate ARGs is forthcoming. UV-based photocatalytic processes are effective to degrade ARGs. Antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) have been recognized as one of the biggest public health issues of the 21st century. Both ARB and ARGs have been determined in water after treatment with conventional disinfectants. Ultraviolet (UV) technology has been seen growth in application to disinfect the water. However, UV method alone is not adequate to degrade ARGs in water. Researchers are investigating the combination of UV with other oxidants (chlorine, hydrogen peroxide (H₂O₂), peroxymonosulfate (PMS), and photocatalysts) to harness the high reactivity of produced reactive species (Clž·, ClOž·ž, Clž₂·ž⁻, žž·OH, and SOž₄ž·⁻€) in such processes with constituents of cell (e.g., deoxyribonucleic acid (DNA) and its components) in order to increase the degradation efficiency of ARGs. This paper briefly reviews the current status of different UV-based treatments (UV/chlorination, UV/H₂O₂, UV/PMS, and UV-photocatalysis) to degrade ARGs and to control horizontal gene transfer (HGT) in water. The review also provides discussion on the mechanism of degradation of ARGs and application of q-PCR and gel electrophoresis to obtain insights of the fate of ARGs during UV-based treatment processes.     

Treatment of organic pollutants by homogeneous and heterogeneous Fenton reaction processes

Nowadays, the water ecosystem is being polluted due to the rapid industrialization and massive use of antibiotics, fertilizers, cosmetics, paints, and other chemicals. Chemical oxidation is one of the most applied processes to degrade contaminants in water. However, chemicals are often unable to completely mineralize the pollutants. Enhanced pollutant degradation can be achieved by Fenton reaction and related processes. As a consequence, Fenton reactions have received great attention in the treatment of domestic and industrial wastewater effluents. Currently, homogeneous and heterogeneous Fenton processes are being investigated intensively and optimized for applications, either alone or in a combination of other processes. This review presents fundamental chemistry involved in various kinds of homogeneous Fenton reactions, which include classical Fenton, electro-Fenton, photo-Fenton, electro-Fenton, sono-electro-Fenton, and solar photoelectron-Fenton. In the homogeneous Fenton reaction process, the molar ratio of iron(II) and hydrogen peroxide, and the pH usually determine the effectiveness of removing target pollutants and subsequently their mineralization, monitored by a decrease in levels of total organic carbon or chemical oxygen demand. We present catalysts used in heterogeneous Fenton or Fenton-like reactions, such as H₂O₂–Fe³⁺(solid)/nano-zero-valent iron/immobilized iron and electro-Fenton-pyrite. Surface properties of heterogeneous catalysts generally control the efficiency to degrade pollutants. Examples of Fenton reactions are demonstrated to degrade and mineralize a wide range of water pollutants in real industrial wastewaters, such as dyes and phenols. Removal of various antibiotics by homogeneous and heterogeneous Fenton reactions is exemplified.     

Persistent free radicals in humin under redox conditions and their impact in transforming polycyclic aromatic hydrocarbons

• Regulation of redox conditions promotes the generation of free radicals on HM. • HM-PFRs can be fractionated into active and inactive types depending on stability. • The newly produced PFRs readily release electrons to oxygen and generate ROS. • PFR-induced ROS mediate the transformation of organic contaminants adsorbed on HM. The role of humic substance-associated persistent free radicals (PFRs) in the fate of organic contaminants under various redox conditions remains unknown. This study examined the characterization of original metal-free peat humin (HM), and HM treated with varying concentrations of H₂O₂ and L-ascorbic acid (VC) (assigned as H₂O₂-HM and VC-HM). The concentration of PFRs in HM increased with the addition of VC/H₂O₂ at concentrations less than 0.08 M. The evolution of PFRs in HM under different environmental conditions (e.g., oxic/anoxic and humidity) was investigated. Two types of PFRs were detected in HM: a relatively stable radical existed in the original sample, and the other type, which was generated by redox treatments, was relatively unstable. The spin densities of VC/H₂O₂-HM readily returned to the original value under relatively high humidity and oxic conditions. During this process, the HM-associated “unstable” free radicals released an electron to O₂, inducing the formation of reactive oxygen species (ROS, i.e., ^•OH and ^•O₂⁻). The generated ROS promoted the degradation of polycyclic aromatic hydrocarbons based on the radical quenching measurements. The transformation rates followed the order naphthalene>phenanthrene>anthracene>benzo[a]pyrene. Our results provide valuable insight into the HM-induced transformation of organic contaminants under natural conditions.     

Scientometric analysis: identification of research trends for ozone as an air pollutant for 2011–2019

Environmental Science and Pollution Research - Ground level ozone is a major air pollutant with known toxic effects on humans. The research field is well established with many scientists from...     

Human health risks in megacities due to air pollution

This study evaluates the health risks in megacities in terms of mortality and morbidity due to air pollution. A new spreadsheet model, Risk of Mortality/Morbidity due to Air Pollution (Ri-MAP), is used to estimate the excess numbers of deaths and illnesses. By adopting the World Health Organization (WHO) guideline concentrations for the air pollutants SO₂, NO₂ and total suspended particles (TSP), concentration-response relationships and a population attributable-risk proportion concept are employed. Results suggest that some megacities like Los Angeles, New York, Osaka Kobe, Sao Paulo and Tokyo have very low excess cases in total mortality from these pollutants. In contrast, the approximate numbers of cases is highest in Karachi (15,000/yr) characterized by a very high concentration of total TSP (～670 μg m^?3). Dhaka (7000/yr), Beijing (5500/yr), Karachi (5200/yr), Cairo (5000/yr) and Delhi (3500/yr) rank highest with cardiovascular mortality. The morbidity (hospital admissions) due to Chronic Obstructive Pulmonary Disease (COPD) follows the tendency of cardiovascular mortality. Dhaka and Karachi lead the rankings, having about 2100/yr excess cases, while Osaka-Kobe (～20/yr) and Sao Paulo (～50/yr) are at the low end of all megacities considered. Since air pollution is increasing in many megacities, and our database of measured pollutants is limited to the period up to 2000 and does not include all relevant components (e.g. O₃), these numbers should be interpreted as lower limits. South Asian megacities most urgently need improvement of air quality to prevent excess mortality and morbidity due to exceptionally high levels of air pollution. The risk estimates obtained from Ri-MAP present a realistic baseline evaluation for the consequences of ambient air pollution in comparison to simple air quality indices, and can be expanded and improved in parallel with the development of air pollution monitoring networks.     

Elevated biogenic sulphur dioxide concentrations over the North Atlantic

Elevated biogenic SO₂ from the oxidation of dimethylsulphide (DMS) in the marine atmosphere was measured over the North Atlantic Ocean in spring and summer 2003. Stable isotope apportionment was used to distinguish between anthropogenic and biogenic SO₂ in the marine atmosphere south of Greenland. Atmospheric DMS measurements were within range of previous studies. Biogenic SO₂ concentrations were as high as 82 nmol m^?3 (spring geometric mean: 4 nmol m^?3, σ = 17; summer geometric mean 7 nmol m^?3, σ = 19) and are the highest reported values for marine biogenic SO₂ in the literature. Elevated biogenic SO₂ was found in air masses influenced by anthropogenic pollutants during the summer. This indicates that anthropogenic pollutants may affect the fate of oceanic emissions of sulphur compounds in the atmosphere favoring the formation of cloud condensation nuclei.     

Organochlorine pollutants in human blood and their relation with age, gender and habitat from North-east India

Organochlorine pesticides (OCPs) have been beneficial to man and environment but their inadvertent use has caused considerable harm to human health. Despite the proliferation of different types of pesticides, organochlorines such as HCH and DDT still account for two third of the total consumption in India because of their low cost and versatility in action again various pests. Since, Assam, a state in North-eastern part of India is an endemic area with perennial transmission where mosquito borne diseases are serious health problems; these pesticides are still being used in huge quantities in vector control as well as in agriculture. A total of 331 human blood samples were collected from district Nagaon and Dibrugarh of Assam to determine the residue levels of DDT and HCH in human blood. The concentrations of selected persistent organochlorine pollutants were measured with gas chromatography-electron capture detector. The results demonstrated that the mean levels of total DDT and HCH were 743 μg L(-1) and 627 μg L(-1) for district Nagaon while 417 μg L(-1) and 348 μg L(-1) for district Dibrugarh. The difference of total HCH and total DDT between these two districts was found to be highly significant (P<0.0001). Among DDT metabolites, the same trend was observed for both the districts as p,p-DDT was the principal component contributed 41% for Nagaon and 58% for Dibrugarh. In case of HCH residues, for Nagaon, β-HCH was the predominant contaminant comprised more than 34% while for Dibrugarh, it was α-HCH that was contributing 43% of total HCH concentration.