Nitrosamine Formation Research Articles

Effects of chlorination on the nitrosamines formation from two algae species in drinking water source-M. aeruginosa and C. meneghiniana

The effects of chlorine dosage, reaction time, algae concentration, and cell components, including extracellular organic matter (EOM), intracellular organic matter (IOM) and cell debris (CD), were evaluated on the formation of nitrosamines (NAs), including N-Nitrosodimethylamine (NDMA), -Nitrosomethylethylamine (NMEA), N-Nitrosodi-n-propylamine (NDPA), N-nitrosodi-n-butylamine (NDBA), N-Nitrosopyrollidine (NPyr), during the chlorination of Microcystis aeruginosa (M. aeruginosa) and Cyclotella meneghiniana (C. meneghiniana) in drinking water treatment. In addition, the NAs formation from Chlorophyll-a and Microcystin-LR (MC-LR) chlorination was investigated. The results showed that NDMA was the most dominant product of two algae, while only a small yield of NPyr, NMEA and NDBA was generated with NDPA as the least. The nitrosamines formation potential (NAsFP) of M. aeruginosa was positively correlated with the chlorine concentration, while the highest NAsFP of C. meneghiniana was observed at 10 mg/L chlorine. With the increase of reaction time, the NAsFP from C. meneghiniana was higher than M. aeruginosa. The NAs formation enhanced with the increase of cell concentration. Moreover, the impacts of cellular components on the NAsFP followed the order of CD > IOM > EOM and IOM > EOM > CD for M. aeruginosa and C. meneghiniana, respectively. The results indicated that proteins and soluble microbial products (SMPs) were the main cellular components to contribute to NAs formation and IOM was the primary source of NAs precursor for both algae. Chlorination of Chlorophyll-a and MC-LR showed that chlorophyll-a formed only a small yield of NDMA and NDBA, while MC-LR made a more significant contribution to the types of NAs.

Atmospheric Chemistry of 2-Amino-2-methyl-1-propanol: A Theoretical and Experimental Study of the OH-Initiated Degradation under Simulated Atmospheric Conditions.

The OH-initiated degradation of 2-amino-2-methyl-1-propanol [CH3C(NH2)(CH3)CH2OH, AMP] was investigated in a large atmospheric simulation chamber, employing time-resolved online high-resolution proton-transfer reaction-time-of-flight mass spectrometry (PTR-ToF-MS) and chemical analysis of aerosol online PTR-ToF-MS (CHARON-PTR-ToF-MS) instrumentation, and by theoretical calculations based on M06-2X/aug-cc-pVTZ quantum chemistry results and master equation modeling of the pivotal reaction steps. The quantum chemistry calculations reproduce the experimental rate coefficient of the AMP + OH reaction, aligning k(T) = 5.2 × 10–12 × exp (505/T) cm3 molecule–1 s–1 to the experimental value kexp,300K = 2.8 × 10–11 cm3 molecule–1 s–1. The theoretical calculations predict that the AMP + OH reaction proceeds via hydrogen abstraction from the −CH3 groups (5–10%), −CH2– group, (>70%) and −NH2 group (5–20%), whereas hydrogen abstraction from the −OH group can be disregarded under atmospheric conditions. A detailed mechanism for atmospheric AMP degradation was obtained as part of the theoretical study. The photo-oxidation experiments show 2-amino-2-methylpropanal [CH3C(NH2)(CH3)CHO] as the major gas-phase product and propan-2-imine [(CH3)2C=NH], 2-iminopropanol [(CH3)(CH2OH)C=NH], acetamide [CH3C(O)NH2], formaldehyde (CH2O), and nitramine 2-methyl-2-(nitroamino)-1-propanol [AMPNO2, CH3C(CH3)(NHNO2)CH2OH] as minor primary products; there is no experimental evidence of nitrosamine formation. The branching in the initial H abstraction by OH radicals was derived in analyses of the temporal gas-phase product profiles to be BCH3/BCH2/BNH2 = 6:70:24. Secondary photo-oxidation products and products resulting from particle and surface processing of the primary gas-phase products were also observed and quantified. All the photo-oxidation experiments were accompanied by extensive particle formation that was initiated by the reaction of AMP with nitric acid and that mainly consisted of this salt. Minor amounts of the gas-phase photo-oxidation products, including AMPNO2, were detected in the particles by CHARON-PTR-ToF-MS and GC×GC-NCD. Volatility measurements of laboratory-generated AMP nitrate nanoparticles gave ΔvapH = 80 ± 16 kJ mol–1 and an estimated vapor pressure of (1.3 ± 0.3) × 10–5 Pa at 298 K. The atmospheric chemistry of AMP is evaluated and a validated chemistry model for implementation in dispersion models is presented.

Formation of nitrosamines during chloramination of two algae species in source water—Microcystis aeruginosa and Cyclotella meneghiniana

The contribution of two algae species, Microcystis aeruginosa (M. aeruginosa) and Cyclotella meneghiniana (C. meneghiniana), to the formation of nitrosamines (NAs) during chloramination in drinking water treatment was investigated. A variety of factors including contact time, algae cell concentration, chloramine dosages, and algal cell components (cell debris (CD), intracellular organic matter (IOM), and extracellular organic matter (EOM)) were evaluated for influencing the formation of different NAs, such as N-Nitrosodiethylamine (NDMA), N-Nitrosomethylethylamine (NMEA), N-Nitrosodibutylamine (NDBA), N-Nitrosodi-n-propylamine (NDPA), and N-nitrosopyridine (NPyr). In addition, NAs formation from Chlorophyll-a and Microcystin-LR (MC-LR) after chloramination was studied. These results showed that the increase of reaction time and algae cell concentration enhanced the formation potential of five types of NAs from both algae species, except for the NDMA formation from C. meneghiniana, which increased first and then decreased with increased reaction time. The generation of NDMA was detected as the dominated type of NAs. The formation of total NAs from both algae species followed same pattern of increasing first and then decreasing with the increase of chloramine dosage. The largest NAs formation potential (NAsFP) of M. aeruginosa and C. meneghiniana showed at 1.5 mM and 1.0 mM monochloramine, respectively. Moreover, the impacts of algae cellular components on the formation potential of NAs followed the order of IOM > EOM ≫ CD and IOM ≫ CD > EOM for M. aeruginosa and C. meneghiniana, respectively, indicating that IOM was the main source of NAs precursors for both algae. Furthermore, EEM analysis before and after chloramination confirmed that the soluble microbial products (SMPs) and protein-like substances were the main cellular components that contributed to NAs formation for both algae. The NAs formation potential of Microcystin-LR was much higher than that of Chlorophyll-a chloramination.

Nitrosamine Reactivity: A Survey of Reactions and Purge Processes

Drug recalls have led to increased regulatory scrutiny into the formation and presence of nitrosamine (N-nitrosoamine) impurities in medicines. This review aims to assist the development of risk mitigation strategies by summarizing known reactions of nitrosamines, with a focus on reactions useful within the context of complex molecule synthesis. This review should serve as a useful reference and help lead to the development of chemical processes which effectively control nitrosamines.

Decolorization of amaranth RI and fast red E azo dyes by thermophilic Geobacillus thermoleovoransKNG 112

AbstractBACKGROUNDAccumulation of industrial dyes in wastewater creates not only environmental problems, but also medical and aesthetic problems. Removal of synthetic dyes from contaminated hot textile industrial discharge is a fundamental issue. Herein, the microbial decolorization of azo dyes amaranth RI and fast red E was studied. The decolorization process was studied in terms of various physicochemical and analytical parameters.RESULTSThe azo dye decolorization efficiency was improved with beef extract and maltose as nitrogen and carbon sources, respectively. At 55 °C, Geobacillus thermoleovorans KNG 112 showed the maximum decolorization for both amaranth RI and fast red E at pH 7 and 8, respectively. Fourier transform infrared spectral analysis revealed the formation of amide, nitrosamine, aromatic and carbonyl compounds, alkyne, alkane, alcohol and alkyl halide groups after dye decolorization. Mixed dye (amaranth RI and fast red E) decolorization resulted in formation of various alkyl acetals, amines (nitrosamines, secondary and tertiary amines) azo groups and alkyl chloride. Furthermore, phytotoxic effect of azo dyes on the germination of fenugreek and green gram showed no inhibitory effects; however, more and rapid germination compared to the control group was observed.CONCLUSIONSThe results lead to the conclusion that the optimization of G. thermoleovorans KNG 112 for removal of azo dyes could have applications in decontamination of hot industrial discharges. © 2021 Society of Chemical Industry (SCI).

Polymer‐Driven Nitrosamine Formation in Houston's Drinking Water

After finding nitrosamines in its water system, the City of Houston studied how polymer coagulants and different stages of water purification affect nitrosamine formation. Results showed that as polymer dose increased and as water backwash or recycled water was mixed in, nitrosamine levels increased. Utilities should remove nitrosamine precursors from source water and optimize polymer dosage to reduce nitrosamines in the purification plant and drinking water distribution system.

Aqueous N-nitrosamines: Precursors, occurrence, oxidation processes, and role of inorganic ions

N-Nitrosamines, well-known human carcinogens, are widely considered to be formed through the disinfection of waters containing compounds with amine moieties. The formation mechanisms of nitrosamines during the disinfection of drinking water and wastewater have been previously reviewed in the literature. However, no study to date has reviewed the effects of inorganic ions on nitrosamines formation during disinfection. Inorganic ions are ubiquitous in the environment and are present at significant concentrations in water and wastewater. Their presence influences aqueous nitrosamines formation, depending on the type, concentration, and environmental conditions. In this review, we have critically reviewed nitrosamines’ precursors and occurrence, disinfection processes associated with nitrosamines’ formation/destruction, and the impact of inorganic ions on the formation or removal of nitrosamines during disinfection of water and wastewater. The disinfectants reviewed in the study were chlorine, chloramine, chlorine dioxide, ozone, and radicals generated through advanced oxidation processes (AOPs). N-Nitrosodimethylamine formation pathways, in the presence and absence of inorganic ions, were also reviewed to summarize our current understanding. Although chloramination has been associated with the formation of nitrosamines, many ozonation studies have also shown significant levels of nitrosamines formation. Pre-oxidation and AOPs have been reported as the most promising mitigation strategies for controlling nitrosamines formation, requiring prolonged exposure of precursors for effective mineralization.

Nitrosamine formation from the reaction of methamphetamine with gaseous nitrous acid.

Methamphetamine is the most commonly seized amphetamine-type stimulant (ATS) worldwide. Chemical residues associated with the use or manufacture of methamphetamine can persist in the air and surfaces in a property for over 5 years and potentially pose risks to the health and safety of the public. When a house is tested for contamination, the test focuses on the presence of surface methamphetamine residue; however, other hazardous chemicals may also be present, including methamphetamine precursors and reaction products. As little has been reported about the ageing of the methamphetamine inside dwellings, there is currently large uncertainty regarding its fate and/or degradation products in such environments. If the indoor reactivity of methamphetamine is similar to that of nicotine-derived third-hand smoke, the production of a carcinogenic nitrosamine is an expected result. Thus, this proof-of-concept study investigated the reaction of methamphetamine with the common gaseous indoor oxidant nitrous acid (HONO) and monitored the fate of the resulting reaction products in simulated laboratory experiments to further understand the potential health risks associated with contaminated properties. Surface methamphetamine residue was observed to decrease with an exponential decay with an upper limit of 2.38 ± 0.5 × 10-3 min-1 upon exposure to HONO gas (5.7 ppmv, 0.25 L min-1 ). N-nitrosomethamphetamine (NMA), a suspected human mutagen and carcinogen, was detected to have a steady-state formation over the sampling time frame, with a surface area concentration of 0.87 μg/100 cm2 , suggesting that the risks to public health for properties contaminated with methamphetamine may be currently underestimated.

New Insights into the Chemical Reactivity of Dry-Cured Fermented Sausages: Focus on Nitrosation, Nitrosylation and Oxidation.

Nitrite and nitrate are added to cured meat for their bacteriological, technological and sensorial properties. However, they are suspected to be involved in the formation of nitroso compounds (NOCs), such as potentially mutagenic nitrosamines, nitrosylheme and nitrosothiols. Controlling the sanitary and sensorial qualities of cured meat products by reducing these additives requires elucidating the mechanisms involved in the formation of NOCs. To this end, we studied the dose-response relationship of added sodium nitrite and/or sodium nitrate (0/0, 80/80, 0/200, and 120/120 ppm) on the formation of NOCs in dry cured fermented sausages. The results showed a basal heme iron nitrosylation in the absence of NaNO2/NaNO3 due to starter cultures. This reaction was promoted by the addition of NaNO2/NaNO3 in the other conditions. Reducing the dose to 80/80 ppm still limits lipid oxidation without the formation of non-volatile nitrosamines. Conversely, the addition of NO2/NO3 slightly increases protein oxidation through higher carbonyl content. The use of 80/80 ppm could be a means of reducing these additives in dry-cured fermented meat products.

Inhibitory effect of alkyl groups on N-nitrosamine formation from secondary and tertiary alkylamines with monochloramine

N -nitrosamines are contaminants of emerging concern, and controlling these chemicals in potable water and recycled water for potable reuse has become important for protecting public health. This study aimed to evaluate the influence of the alkyl chain lengths of N -nitrosamine precursors (secondary and tertiary amines) on the formation of N -nitrosamines via chloramination. The molar conversion efficiency from dimethylamine, an N -nitrosodimethylamine (NDMA) precursor, to NDMA (0.67%) was greater than that from diethylamine, an N -nitrosodiethylamine (NDEA) precursor, to NDEA (0.38%). Similarly, the molar conversion efficiency from trimethylamine to NDMA (0.92%) was greater than from triethylamine to NDEA (0.33%). Interestingly, a considerable difference in molar conversion efficiencies were observed for tertiary amines with the N , N -dialkyl- α -arylamine structure: the molar conversion efficiencies from N , N -dimethylbenzylamine and N , N -diethylbenzylamine to NDMA and NDEA were 50.2% and 1.7%, respectively. These results indicate that amines with ethyl groups have lower potentials for producing the corresponding N -nitrosamines than those with methyl groups. These differences in yields between amines with methyl and ethyl groups can be explained by the difference in electron density in the nitrogen atom of the amine, which influences the protonation of the amine and stabilization of intermediate species. These findings could be useful for enhancing source control of water and wastewater by regulating runoff or industrial wastewater containing high concentrations of specific N -nitrosamine precursors. • Formation of four N -nitrosamines from the secondary and tertiary amines were tested. • The molar conversion of amines having ethyl group were lower than those of methyl group. • Benzylamines had higher molar conversion values in comparison with simple alkylamines. • Longer alkyl chains in amines suppressed N -nitrosamine formation reactions.

Determination of dimethylamine and nitrite in pharmaceuticals by ion chromatography to assess the likelihood of nitrosamine formation

Since July 2018 several drugs have been recalled due to contamination with N-nitrosodimethylamine (NDMA), a probable human carcinogen. Dimethylamine (DMA) and nitrite are precursors in the formation of NDMA. In this study, ion chromatography (IC) methods were developed for the determination of these two precursors in drug substances and drug products. Two methods were developed to determine DMA in two drug products using a cation exchange separation coupled to suppressed conductivity detection. The limit of detection of DMA is < 1 μg/g of active pharmaceutical ingredient (API) for both methods. Nitrite was determined using an anion exchange separation coupled with UV absorbance detection. The limit of detection of nitrite was 0.918 μg/g API. The developed methods were successfully applied to DMA and nitrite determinations in five drug products including metformin, losartan, ranitidine, Nytol, and Benadyrl, and two drug substances (APIs), losartan potassium and metformin hydrochloride. Some samples contained nitrite and DMA at detectable levels. Dimethylamine and nitrite recovery from pharmaceutical samples ranged from 96.0-104 %. The developed methods should be useful for the rapid screening and quantification of nitrite and DMA in pharmaceuticals and in-process samples to assess the likelihood of NDMA formation. The methods for DMA should be applicable to other amines to assess the likelihood of the formation of other nitrosamines in pharmaceutical products.

Nitrosamines in Aquatic Ecosystems: Sources, Formation, Toxicity, Environmental Risk (Review) 1. Structure, Properties, Ways of Entering and Formation in Waterbodies

Due to the saturation of natural waters with nitrogen compounds resulting from natural processes and anthropogenic activities, the problem arises of studying the ways of their migration, transformation in the hydrosphere and in aquatic biota. One of the ways of nitrogen transformation in the environment is the formation of nitrosamines—toxic organisms or biota that exhibit carcinogenic, mutagenic and teratogenic properties and have a toxic effect on living beings. The main sources of nitrogen-containing compounds, precursors of nitrosamines, into waterbodies are agricultural, industrial and municipal wastewater. The present paper analyses the ways of synthesis of nitrosamines in the aquatic environment and in living organisms or biota, the main methods of analysis of these compounds, their distribution and transformation in hydrosphere, as well as the ways of decrease in their concentrations and modern techniques for removal of nitrosamines from aquatic ecosystems.

Role of ranitidine in N-nitrosodimethylamine formation during chloramination of competing micropollutants

Ranitidine (RNT) is a widely known precursor of N-nitrosodimethylamine (NDMA) as evinced by the self-catalytic formation of NDMA during chloramination. In the present study, the NDMA formation potentials (NDMA-FP) of 26 micropollutants were assessed, particularly when mixed with RNT. 11 compounds were identified as individual precursors, including trimebutine and cimetidine, which exhibited substantial NDMA-FP, with up to 10% molar yield. In addition, nitrosamines, other than NDMA, namely N-nitrosodiethylamine and N-nitrosomethylamine, were observed from diethylamine-containing precursors, such as metoclopramide. In a 1:1 mixture of RNT and a competitor, the change in NDMA-FP was mostly comparable (within 20% deviation), while antagonistic interactions were observed for competitors, such as diethylhydroxylamine. The scattered overall NDMA-FP should be considered as a product of competition among the precursors for core substrates and intermediates for NDMA formation. The co-existence of either trimebutine or metoclopramide with RNT led to an exceptionally synergetic NDMA generation. Degradation kinetics and chlorination/nitrosation experiments combined with mass spectroscopy analyses indicated that RNT would accelerate both the initial chlorination and nitrosation of trimebutine and metoclopramide, leading to N-nitroso complexes, which have well-understood NDMA formation pathways, i.e., amination with subsequent aminyl radical generation. This work demonstrates a wide array of precursors with NDMA-FP, suggesting that nitrosamine formation is potentially underestimated in field environments.

N-nitrosamine Impurities in Medicines: Toxicity, Formation Pathways, Methods of Determination, and Limits (Review)

Introduction. N-nitrosamine compounds are potent genotoxic agents in animal species and some are classified as probable human carcinogens. This group of genotoxic impurities was found in drugs such as angiotensin II receptor blockers, histamine H1 receptor antagonists, and synthetic antidiabetic drugs. This discovery caused a flurry of alarm in the global pharmaceutical industry and resulted in a series of international investigations trying to determine root causes of nitrosamine formation in medicinal products and to find ways to minimize risks associated with nitrosamine contamination.Text. This paper provides an overview of the current state of the problem. It summarises the main pathways of N-nitrosamine formation in medicinal products at the stages from synthesis of active pharmaceutical ingredients to storage of finished pharmaceutical products. The paper describes the main mechanism responsible for the toxic effect of this group of impurities in human body. It also describes methods of extraction and analysis of N-nitrosamines found in medicinal products. It was demonstrated that high-performance liquid chromatography and gas chromatography-mass spectrometry are a golden standard for the detection of these contaminants. The paper also touches upon the main principles of setting limits for nitrosamine impurities in medicinal products.Conclusion. The data presented give a picture of the root causes of N-nitrosamine formation in medicinal products, as well as current detection and control methods used worldwide. Meanwhile, the paper raises a key issue about the need to develop Russian standards that would control the purity of medicinal products in terms of N-nitrosamine impurities. For that end, it will be necessary to draw on the experience of the leading USA and EU regulatory authorities.

Nitrite reduction in fermented meat products and its impact on aroma.

Fermented meat products are important not only for their sensory characteristics, nutrient content and cultural heritage, but also for their stability and convenience. The aroma of fermented meat products is unique and its formation mechanisms are not completely understood; however, the presence of nitrite and nitrate is essential for the development of cured aroma. The use of nitrite and nitrate as curing agents in meat products is based on its preservation activity. Even though their presence has been associated with several risks due to the formation of nitrosamines, their use is guarantee due to their antimicrobial action against Clostridium botulinum. Recent trends and recommendations by international associations are directed to use nitrite but at the minimum concentration necessary to provide the antimicrobial activity against Clostridium botulinum. This chapter discuss the actual limits of nitrite and nitrite content and their role as curing agents in meat products with special impact on dry fermented products. Regulatory considerations, antimicrobial mechanisms and actual trends regarding nitrite reduction and its effect on sensory and aroma properties are also considered.

The competitive effect of different chlorination disinfection methods and additional inorganic nitrogen on nitrosamine formation from aromatic and heterocyclic amine-containing pharmaceuticals

Amine-containing pharmaceuticals formed nitrosamines that are nitrogenous disinfection byproducts of public concerns due to their carcinogenicity. The objective of this study was to investigate the co-effect of additional inorganic nitrogen in different forms (ammonium, nitrite, and nitrate) and different disinfection approaches (chlorination, monochloramination, dichloramination, and two-step chlorination) on eight nitrosamine formation from four widely used pharmaceuticals. N-nitrosodimethylamine (NDMA) was the main species formed. The presence of N-nitrosomethylethylamine (NMEA), nitrosomorpholine (NMor), and N-nitrosopiperidine (NPip) was found in certain experiments. For one-step chlorination, the influential factors, in decreasing order of importance, were the molecular structural characteristics of the pharmaceutical, oxidation method, and presence and form of additional nitrogen. In four pharmaceuticals with comparative structures, the availability of amine intermediates during degradation was the key to higher nitrosamine yields. Monochloramine significantly enhanced nitrosamine formation from four pharmaceuticals. NDMA formation by adding hypochlorous acid and ammonium separately were lower than those during monochloramination. During two-step chlorination, NDMA formation was enhanced at certain pre-chlorine doses (e.g., a Cl/N molar ratio of 20 or 4). The pre-chlorine dose changed the Cl/N ratio. As the ratio was increased, the combined chlorine residual was formed and decreased. When the ratio was high, breakpoint chlorination possibly occurred enhancing NDMA formation. While NDMA formation was successfully inhibited by two-step chlorination, ammonium brought the NDMA yields of these pharmaceuticals back to the range observed in chloramination, suggesting the importance of ammonium control for limiting NDMA formation from pharmaceuticals during two-step chlorination.

Pathways for N-Nitroso Compound Formation: Secondary Amines and Beyond

Recent drug recalls (e.g., valsartan and ranitidine) linked to the discovery of nitrosamine impurities have led to increased regulatory scrutiny in the manufacturing process of marketed medicines, notably for determining any sources of risk for nitrosamine (or related N-nitroso compound) formation within the manufacturing process. This review seeks to aid the risk assessment process through identifying known conditions and reactants through which N-nitroso compounds can be formed.

Daily intake of nitrate and nitrite via meat and poultry in Egypt

ABSTRACT Nitrate and nitrite are the most applied food additives to inhibit microbial growth. The main risk of nitrate and nitrite presence in food is the formation of nitrosamines during food preparation and digestion. However, dietary intake of nitrite and nitrate from food has potential cardiovascular benefits. Accordingly, 160 samples from meat and poultry were randomly collected to evaluate the level of occurrence nitrate and nitrite using an HPLC method and estimate the daily intake (EDI) of Egyptian adults and children. The levels of nitrate and nitrite ranged between 1.3–557 mg/kg and 6–812 mg/kg, respectively. The EDI was compared with the accepted daily intake (ADI) represented in the hazard index (HI) scale. The nitrite results clarify that all HI values were above 1 for all commodities, while for nitrate it exceeded 1 only for canned meat and basturma, when consumed by children.

Spatial, temporal variability and carcinogenic health risk assessment of nitrosamines in a drinking water system in China

Nitrosamines, as a class of emerging frequently detected nitrogenous disinfection byproducts (N-DBPs) in drinking water, have gained increasing attention due to their potentially high health risk. Few studies focus on the occurrence variation and carcinogenic health risk of nitrosamines in drinking water systems. Our study aimed to investigate the spatial and temporal variability of nitrosamines in a drinking water system and to conduct a carcinogenic health risk assessment. Three types of water samples, including influent water, treated water and tap water, were collected monthly during an entire year in a drinking water system utilizing a combination of chlorine dioxide and chlorine in central China, and 9 nitrosamines were measured. The nitrosamine formation potentials (FPs) in influent water were also determined. N-nitrosodimethylamine (NDMA) was the most prevalent compound and was dominant in the water samples with average concentrations ranging from 2.5 to 67.4 ng/L, followed by N-nitrosodiethylamine (NDEA) and N-nitrosopiperidine (NPIP). Nitrosamine occurrence varied monthly, and significant seasonal differences were observed in tap water (p < .05). There were decreasing mean NDMA, NDEA and NPIP concentrations from influent water to treated water to tap water, but no significant spatial variability was observed within the water distribution system (p > .05). The average and 95th percentile total lifetime cancer risks for the three main nitrosamines were 4.83 × 10−5 and 4.48 × 10−4, respectively, exceeding the negligible risk level (10−6) proposed by the USEPA. Exposure to nitrosamines in drinking water posed a higher cancer risk for children than for adults, and children aged 0.75 to 1 years suffered the highest cancer risk. These results suggest that nitrosamine occurrence in tap water varied temporally but not spatially. Exposure to drinking water nitrosamines may pose a carcinogenic risk to human health, especially to children.

Catalytic degradation of chlorpheniramine over GO-Fe3O4 in the presence of H2O2 in water: The synergistic effect of adsorption

Chlorpheniramine is a pharmaceutical widely used and found in water environments. Besides hormone disruption and adverse environmental effects, chlorpheniramine forms carcinogenic nitrosamines during disinfection. We have demonstrated previously the efficient adsorption of chlorpheniramine from aqueous solution onto graphene oxide-magnetite composite (GO-Fe3O4). The present study focused on the elimination of chlorpheniramine and the formation of nitrosamine byproducts during reaction with H2O2 over GO-Fe3O4 catalyst. The effects of the morphology of GO-Fe3O4 in terms of iron fraction, pH, concentrations of H2O2 and organic matters on chlorpheniramine removal in the GO-Fe3O4-H2O2 system were investigated. Chlorpheniramine was efficiently removed at pH 9 when GO-Fe3O4 had a higher micropore volume and surface area. Kinetics study showed that both oxidation (k = 5.1(±0.2) × 10−3 (mg g−1)−1 min−1) and adsorption reactions (k = 2.7(±0.1) × 10−3 (mg g−1)−1 min−1) fitted well with the second-order kinetics model. The adsorption sites on the GO-Fe3O4 surface could be different from those involved during catalytic oxidation. Chlorpheniramine removal decreased by 44.9% in the 5th cycle without regeneration due to the structural fracture of GO-Fe3O4. A tentative pathway of chlorpheniramine degradation and nitrosamine formation by GO-Fe3O4-H2O2 was proposed. GO-Fe3O4 was an adsorbent and effective catalyst in chlorpheniramine degradation by H2O2 that exhibited limited nitrosamine formation at moderate reaction time.