Occurrence and human exposure to bromate via drinking water, fruits and vegetables in Chile

Perchlorate and chlorate assessment in drinking water in northern Chilean cities

Perchlorate and chlorate are endocrine disruptors considered emerging contaminants (ECs). Both oxyanions are commonly associated with anthropogenic contamination from fertilizers, pesticides, explosives, and disinfection byproducts. However, the soils of the Atacama Desert are the most extensive natural reservoirs of perchlorate in the world, compromising drinking water sources in northern Chile. Field campaigns were carried (2014-2018) to assess the presence of these ECs in the water supply networks of twelve Chilean cities. Additionally, the occurrence of perchlorate, chlorate and other anions typically observed in drinking water matrices of the Atacama Desert (i.e., nitrate, chloride, sulfate) was evaluated using a Spearman correlation analysis to determine predictors for perchlorate and chlorate. High concentrations of perchlorate (up to 114.48 μg L-1) and chlorate (up to 9650 μg L-1) were found in three northern cities. Spatial heterogeneities were observed in the physicochemical properties and anion concentrations of the water supply network. Spearman correlation analysis indicated that nitrate, chloride, and sulfate were not useful predictors for the presence of perchlorate and chlorate in drinking water in Chile. Hence, this study highlights the need to establish systematic monitoring, regulation, and treatment for these EC of drinking water sources in northern Chilean cities for public health protection.

Isolation of Anaerobic Bromate-Reducing Bacteria Using Different Carbon Sources and Transcriptomic Insights From Klebsiella variicola Glu3

Bromate, a possible human carcinogen, can be reduced to innocuous bromide by microorganisms. To characterize bromate reducers, microbes were enriched anaerobically from activated sludge by using bromate as the sole electron acceptor and different carbon sources as the electron donor. Bacteria that showed significant bromate-reducing activity but not coupled to cell growth were isolated. Two whole genomes of the isolates, namely, Raoultella electrica Lac1 and Klebsiella variicola Glu3, were reconstructed by Illumina and Nanopore sequencing. Transcriptomic analysis suggested that neither the respiratory nitrate reductase, the selenate reductase, nor the dimethylsulfoxide reductase was involved in the bromate reduction process, and strain K. variicola Glu3 reduced bromate via a yet undiscovered enzymatic mechanism. The results provide novel phylogenetic insights into bromate-reducing microorganisms and clues in putative genes encoding enzymes related to bromate reduction.

Hazardous inorganic disinfection by-products in Egypt's tap drinking water: Occurrence and human health risks assessment studies

This study is the first that monitored the presence and levels of chlorite, chlorate and bromate in tap drinking water of Egypt. Three hundred and eight samples were collected from 22 governorates across Egypt and were analyzed using a standardized ion chromatography method. Forty-seven samples were contaminated by one or more of the inorganic disinfection by-products (DBPs) and only 12 samples exceeded the admissible maximum contamination levels (MCLs). The ratio of samples detected, and exceeding the MCLs were low relative to the global literature. Chlorate was the most prevalent inorganic DBPs (40 samples; concentration <12-4082 μg/L) followed by bromate (12 samples; concentration <3-626 μg/L) then chlorite (5 samples; concentration <12-123 μg/L). Chlorite was always below the MCL and had no human health risk even for the worst-case scenario. Bromate is a real challenge as it poses a significant cancer risk even for the median concentrations. None of the inorganic DBPs was detected in the tap drinking water of Beheira, Cairo, Gharbia, Giza, Kafr El Sheikh, Luxor, Monufia, and Suez governorates. This study manifested the importance of routine monitoring, and implementing counter measures to control the levels of the hazardous inorganic DBPs in tap drinking water.

A review on water treatment technologies for the management of oxoanions: prospects and challenges

Oxoanions are a class of contaminants that are easily released into the aquatic systems either through natural or anthropogenic activities. Depending on their oxidation states, they are highly mobile, resulting in the contamination of underground water. Above the permissible level in groundwater, they pose as threats to mammals when the contaminated water is consumed. Some of the health challenges caused are cancer, neurological, cardiac, gastrointestinal, and skin disorders. Several treatment technologies have been adopted over the years for the management of these oxoanions present in the aquatic systems. However interesting these treatment technologies might be, they also have their limitations such as cost-effectiveness, the complexity of the process, and generation of secondary pollutants. This work focused on some of the water treatment technologies applied for the removal of oxoanions. Some of the advantages and disadvantages of these treatment technologies are also highlighted. Amongst all the treatment technologies, adsorption is the most applied method for the removal of oxoanions. However, photocatalysis has a higher prospect since it is non-selective and secondary pollutants are not generated after the treatment process. Also, photocatalysis can simultaneously reduce and oxidise oxoanions as well as organic pollutants respectively.

Chronic Effects of Bromate on Sexual Reproduction of Freshwater Rotifer Brachionus calyciflorus

The effects of potassium bromate (KBrO₃), sodium bromate (NaBrO₃), and potassium bromide (KBr) on the sexual reproduction of the rotifer Brachionus calyciflorus were studied by 2-d population growth, 4-d sexual reproduction, and 7-d resting egg production tests. The results showed that low concentrations of bromate promote 2-d and 4-d rotifer population growth, while high concentrations limit it. Bromate stress significantly affected parameters of rotifer sexual reproduction, including the ratio of mictic to amictic females, the mictic rate of rotifers, and the fertilization rate of mictic females. KBrO₃ at 0.001, 0.01, 1, and 10 mg/L, NaBrO₃ at 1 and 10 mg/L, and KBr at 100 and 200 mg/L significantly increased resting egg production, while KBrO₃ at 100 and 200 mg/L, and NaBrO₃ at 200 mg/L significantly decreased it. Resting egg production appears to provide a sensitive endpoint in evaluating the effect of bromate on rotifer sexual reproduction.

TiO2-based catalysts for photocatalytic reduction of aqueous oxyanions: State-of-the-art and future prospects

Nowadays, an increasing discharge of oxyanions to the natural environment has been attracting worldwide attention. TiO₂-based photocatalysis is regarded as one of the most promising technologies for the conversion of toxic oxyanions (such as chromate, nitrate, nitrite, bromate, perchlorate and selenate) to harmless and/or less toxic substances in contaminated waters. Various types of TiO₂-based catalysts have been developed, and each of them exhibits its own advantages in catalytic reduction of oxyanions. However, the application of these nanostructured TiO₂ in real water bodies remains a challenge, with limitations associated with sunlight harvesting abilities, production costs, reuse stability and exposure risks. Herein, we aim to present a critical review on reported TiO₂-based photocatalytic reduction of aqueous oxyanions, provide a comprehensive understanding of the possible reaction pathways of formed active species, and evaluate the reduction performance of different types of TiO₂-based catalysts. In addition, the impact of operating parameters (such as solution pH, temperature, dissolved oxygen and coexisting substances) on catalytic reduction performance is discussed. Furthermore, the perspectives of TiO₂-based photocatalytic reduction of oxyanions are also proposed.

Elevated concentrations of bromate in Drinking water and groundwater from Kuwait and associated exposure and health risks

Drinking water is an important source of human exposure to bromate, an ubiquitous environmental contaminant and a suspect human carcinogen. Nevertheless, little is known with regard to bromate exposure from water produced by thermal desalination of seawater. The purpose of this study was to determine the occurrence of bromate in desalinated drinking water and groundwater from Kuwait and estimate associated exposure and health risks to consumers. In this study, 194 tap and ground water samples collected from Kuwait were analyzed for the presence of bromate and bromide (reduced form of bromine). Bromate was found in almost all tap water samples with a mean concentration of 19.6 μg/L, which is higher than the maximum acceptable contaminant level (MCL) of 10 μg/L. The mean concentration of bromide in tap water samples was 46.2 μg/L. In bottled water, lower mean bromate concentration was found (2.89 μg/L) with mean bromide levels at 76.1 μg/L. Saline brackish water had bromate concentration at 9.48 μg/L while bromate was not detected in saline groundwater/well water samples. The mean estimated daily intake (EDI) of bromate by the Kuwaiti population through tap water and commonly consumed bottled water was 21.7 μg/d and 3.21 μg/d, respectively. Among the five age groups, 3 to 5-year-old children had the highest EDI of bromate at 15.4 μg/d. The excess cancer risk due to ingestion of bromate in tap water was estimated to be 3.92 × 10^-4, which is approximately one order of magnitude higher than the maximum acceptable level of risk (2× 10^-5). This study highlights the significance of desalinated water as a source of bromate exposure.