Degradation of micropollutants in flow-through VUV/UV reactors: Impact of internal diameter and baffle allocation.

Application of VUV/UV process for micropollutants removal in decentralized water supply systems (e.g., rural drinking water treatment) is promising while few researches by far paid attention to the performance of practical flow-through reactors. This study investigated the degradation of atrazine (ATZ), sulfamethoxazole (SMX) and metoprolol (MET) under different hydrodynamic conditions in reactors with varied internal diameters and baffle allocations. Results showed that the target micropollutants could be degraded efficiently in the flow-through VUV/UV reactors following basically the pseudo-first order kinetics (R2 ≥ 0.97). The largest degradation rate constants were found in the D35 reactor and incorporation of baffles in the D50 and D80 reactors accelerated obviously the micrpollutants degradation. The improved performances of the baffled reactors were due mainly to the elevated utilization of HO•, and a new parameter named UEHO (HO• utilization efficiency) was proposed accordingly. The calculated UEHO values of the reactors ranged between 30.2% and 69.2% with the largest found in the D50-5 reactor. This testified the usually insufficient utilization of radicals in flow-through reactors and the effectiveness of baffle implementation. Electrical energy per order (EEO) values of micropollutants degradation in the reactors were in the range of 0.104-0.263 kWh m-3 order-1. The degradation was inhibited significantly by high-concentration nitrate yet the formed nitrite concentration stayed consistently below the drinking water limitation. The acute toxicity of the micropollutant solutions increased first and leveled off afterwards during the VUV/UV treatment, as indicated by the inhibition ratios of luminescence intensity of Vibrio fischeri.

Impact of aqueous environments on hydrogen peroxide activation by manganese oxides: Kinetics and the critical role of bicarbonate.

MnO2 activating H2O2 is a promising way in the field of advanced oxidation processes (AOPs) and in situ chemical oxidation (ISCO) to remove contaminants. However, few studies have focused on the influence of various environmental conditions on the performance of MnO2-H2O2 process, which restricts the application in real world. In this study, the effect of essential environmental factors (ionic strength, pH, specific anions and cations, dissolved organic matter (DOM), SiO2) on the decomposition of H2O2 by MnO2 (ε-MnO2 and ß-MnO2) were investigated. The results suggested that H2O2 degradation was negatively correlated with ionic strength and strongly inhibited under low pH conditions and with phosphate existence. DOM had a slight inhibitory effect while Br-, Ca2+, Mn2+ and SiO2 placed negligible impact on this process. Interestingly, HCO3- inhibited the reaction at low concentrations but promoted H2O2 decomposition at high concentrations, possibly due to the formation of peroxymonocarbonate. This study may provide a more comprehensive reference for potential application of H2O2 activation by MnO2 in different water systems.

Polyurethane Foam Face Masks as a Dosimeter for Quantifying Personal Exposure to Airborne Volatile and Semi-Volatile Organic Compounds.

Airborne volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs) are commonly quantitated by collecting the analytes on solid sorbent tubes or passive air samplers, followed by solvent extraction and instrumental analysis, or by grab bag/canister measurements. We report herein a user-friendly sampling method by breathing through polyurethane foam (PUF) face masks to collect airborne VOCs and SVOCs for chemical analysis. Specifically, dibasic esters, phthalate esters, polycyclic aromatic hydrocarbons, linalool, and nicotine trapped on PUF masks were quantitated by gas chromatography-mass spectrometry analysis as model VOCs and SVOCs. Results showed that the amount of these model VOCs and SVOCs trapped on PUF masks is proportional to the exposure duration. After cross-validation by parallel sampling using XAD-2 packed sorbent tubes, the method was used to quantitate VOCs and SVOCs in a variety of indoor and outdoor environments with varying air concentrations of analytes, temperature, humidity, and wind speed. Because air pollution is considered a major cause of many human diseases and premature deaths and the developed PUF mask sampling method showed high trapping efficiencies for both VOCs and SVOCs, it is believed that the developed sampling method will find wide application in assessing air pollution-associated disease risks with possible extension to more classes of VOCs and SVOCs when coupled with suitable instrumental detection methods.

On the Flip Side of Mask Wearing: Increased Exposure to Volatile Organic Compounds and a Risk-Reducing Solution.

Surgical masks have been worn by the public worldwide during the COVID-19 pandemic, yet hazardous chemicals in the petroleum-derived polymer layer of masks are currently ignored and unregulated. These organic compounds pose potential health risks to the mask wearer through dermal contact or inhalation. Here, we show that surgical masks from around the world are loaded with semivolatile and volatile organic compounds (VOCs), including alkanes, polycyclic aromatic hydrocarbons (PAHs), phthalate esters, and reactive carbonyls at ng to µg/mask levels. Naphthalene was the most abundant mask-borne PAH, accounting for over 80% of total PAH levels; acrolein, a mutagenic carbonyl, was detected in most of the mask samples, and di(2-ethylhexyl) phthalate, an androgen antagonist, was detected in one-third of the samples. Furthermore, there is large mask-to-mask variability of the residue VOCs, revealing the uneven quality of masks. We confirm that masks containing more residue VOCs lead to significantly higher exposure levels and associated disease risks to the wearer, which should warrant the attention of the general public and regulatory agencies. We find that heating the masks at 50 °C for as short as 60 min lowers the total VOC content by up to 80%, providing a simple method to limit our exposure to mask-borne VOCs.

Analysis of Polycyclic Aromatic Hydrocarbons and Phthalate Esters in Soil and Food Grains from the Balkan Peninsula: Implication on DNA Adduct Formation by Aristolochic Acid I and Balkan Endemic Nephropathy.

Balkan endemic nephropathy (BEN) is a chronic tubulointerstitial nephropathy affecting residents of rural farming areas in many Balkan countries. Although it is generally believed that BEN is an environmental disease caused by multiple geochemical factors with much attention on aristolochic acids (AAs), its etiology remains controversial. In this study, we tested the hypothesis that environmental contamination and subsequent food contamination by polycyclic aromatic hydrocarbons (PAHs) and phthalate esters are AA toxicity factors and important to BEN development. We identified significantly higher concentrations of phenanthrene, anthracene, diethyl phthalate (DEP), dibutyl phthalate (DBP), and benzyl butyl phthalate (BBP) in both maize and wheat grain samples collected from endemic villages than from nonendemic villages. Other PAHs and phthalate esters were also detected at higher concentrations in the soil samples from endemic villages. Subsequent genotoxicity testing of cultured human kidney cells showed an alarming phenomenon that phenanthrene, DEP, BBP, and DBP can interact synergistically with AAs to form elevated levels of AA-DNA adducts, which are associated with both the nephrotoxicity and carcinogenicity of AAs, further increasing their disease risks. This study provides direct evidence that prolonged coexposure to these environmental contaminants via dietary intake may lead to greater toxicity and accelerated development of BEN.

Fabric Masks as a Personal Dosimeter for Quantifying Exposure to Airborne Polycyclic Aromatic Hydrocarbons.

In this study, we assessed the feasibility of using ordinary face masks as a sampling means to collect airborne polycyclic aromatic hydrocarbons (PAHs). Nonwoven fabric masks can trap three-ring or larger PAHs at a high efficiency (>70%) and naphthalene at ∼17%. The sampling method is quantitative as confirmed by comparison with the standard method of the National Institute for Occupational Safety and Health. In conjunction with sensitive fluorescence detection, the method was applied to quantify nine airborne PAHs in a range of indoor and outdoor environments. Wearing the mask for 2 h allowed quantification of individual PAHs as low as 0.07 ng/m3. The demonstration shows applicability of the method in monitoring PAHs down to ∼30-80 ng/m3 in university office and laboratory settings and up to ∼900 ng/m3 in an incense-burning temple. Compared with traditional filter-/sorbent tube-based approaches, which require a sampling pump, our new method is simple, convenient, and inexpensive. More importantly, it closely tracks human exposure down to the individual level, thus having great potential to facilitate routine occupational exposure monitoring and large-scale surveillance of PAH concentrations in indoor and outdoor environments.

Novel natural mutations in the hepatitis B virus reverse transcriptase domain associated with hepatocellular carcinoma.

BACKGROUND/AIM: Hepatitis B Virus (HBV) mutations play a role in the development of hepatocellular carcinoma (HCC). However, the association between HBV polymerase gene mutations and HCC has not been reported. In this study, we conducted a multi-stage study to identify HCC-related mutations in the reverse transcriptase (RT) domain of the HBV polymerase gene. METHODS: A total of 231 HCCs and 237 non-HCC controls from Qidong, China, were included in this study. The entire sequence of HBV RT was first compared between 29 HCC and 35 non-HCC cases, and candidate mutations were then evaluated in two independent validation sets. RESULTS: There were 15 candidate mutations identified from the discovery set, with A799G and T1055A being consistently associated with HCC across all studies. A pooled analysis of samples revealed that A799G, A987G, and T1055A were independent risk factors for HCC, with adjusted odds ratios of 5.53 [95% confidence interval (CI), 1.69-18.10], 4.20 (95%CI, 1.15-15.35), and 3.78 (95%CI, 1.45-9.86), respectively. A longitudinal study showed that these mutations were detectable 4-5 years prior to HCC diagnosis. CONCLUSIONS: Our study provides evidence the first that HBV RT contains naturally occurring mutations that can be used as predictive markers for HCC.