Current Drinking Water Standards Research Articles

Prenatal exposure to tap water containing nitrate and the risk of small-for-gestational-age: A nationwide register-based study of Danish births, 1991–2015

BackgroundPrenatal nitrate exposure from household tap water has been associated with increased risk of fetal growth restriction, preterm birth, birth defects, and childhood cancer. We aim to examine the association between maternal consumption of drinking-water nitrate during pregnancy and small-for-gestational-age (SGA) in a nationwide study of Danish-born children, as only one prior study has examined this association. MethodsWe linked individual-level household estimates of nitrate in tap water and birth registry data to all live singleton Danish births during 1991–2015 from Danish-born parents where the mother resided in Denmark throughout the pregnancy. Exposure was both binned into four categories and modeled as an ln-transformed continuous variable. SGA was defined as the bottom 10% of births by birth weight per sex and gestational week. Multiple logistic regression models with generalized estimating equations were used to account for siblings born to the same mother while controlling for relevant confounders. ResultsIn the cohort of 1,078,892 births, the median pregnancy nitrate exposure was 1.9 mg/L nitrate. Compared to the reference group (≤2 mg/L), we found an increased risk of SGA in the second category (>2–5 mg/L) (OR = 1.04, 95% CI: 1.03–1.06) and third category (>5–25 mg/L) (OR = 1.02, 95% CI: 1.00–1.04) but not in the highest (>25 mg/L). There was strong (p = 0.002) evidence of an increase in SGA with nitrate in the model with continuous exposure (OR = 1.02, 95% CI: 1.01–1.04 per 10-fold increase in nitrate). Results were robust when restricting to households with nitrate levels at or below the current Danish and European Union regulatory drinking water standard (50 mg/L nitrate). ConclusionsOur findings suggest that exposure from nitrate in household tap water, even below current regulatory standards, may increase risk of SGA, raising concerns of whether current allowable nitrate levels in drinking water protect children from SGA.

Metal mixture exposures and multiplexed autoantibody screening in Navajo communities exposed to uranium mine wastes

BackgroundEnvironmental exposures to metals in uranium mining wastes and drinking water were documented in more than half of the 1304 Navajo community members of the Diné Network for Environmental Health (DiNEH) Project, the first comprehensive assessment of exposures to these metals and community health on the Navajo Nation. ObjectiveEvaluate environmental exposures among participants who provided blood and urine samples using multiplexed autoantibody positivity as an early effect biomarker. MethodsSurvey and geospatial location data, well water quality, and metals biomonitoring were used to assess exposures to mixed-metal wastes from 100 abandoned uranium waste sites. ResultsWe observed that the prevalence of multiplexed autoantibody positivity in 239 participants was more than double that reported for the U.S. population (27.2% v. 13.8%) even though the national prevalence was generated using a different assay, the HEp-2 cell-based antinuclear antibody test. Increased risk of multiplexed autoantibody screening positivity (OR = 3.07,95%CI 1.15–8.22) was found among DiNEH study people who lived close to uranium mine and milling wastes and consumed metals in drinking water. Associations for females were even stronger when they lived closed to contaminated uranium mining and milling sites. Anti-U1-RNP antibodies were associated with water consumption of nickel. ConclusionProximity to waste sites and consumption of metals in water even below current drinking water standards were associated with perturbations of immune tolerance. These findings are consistent with previous studies of autoimmunity in the local population and demonstrate that multiplexed autoantibody screening method has a potential as sentinel indicator of exposures to environmental metals. Impact statementThis is the first, community-engaged environmental health study in exposed Navajo communities that applied clinical multiplexed testing in risk assessment of environmental metals associated with abandoned, unremediated uranium mining and milling waste sites. Routine clinical autoimmunity measures could be used as early effect biomarkers of environmental metal exposures.

Are current drinking water standards for nitrate sufficient for preventing adverse birth outcomes and childhood cancer– Findings from a cohort of over one million children in Denmark

Are current drinking water standards for nitrate sufficient for preventing adverse birth outcomes and childhood cancer– Findings from a cohort of over one million children in Denmark

AWWA Water Science Author Spotlight

Having recently published an article in AWWA Water Science, Caroline E. Scruggs answered questions from the publication's editor-in-chief, Kenneth L. Mercer, about the research. Mapping Potable Reuse Survey Data Using Spatial Statistics to Inform Tailored Education and Outreach Maurice P. Cruz, Caroline E. Scruggs, and Lauren N. Distler Caroline and her son ski in Santa Fe, N.M. I went to Virginia Tech for a mechanical engineering degree, thinking I would work on innovations in wind and solar energy. However, I changed majors a few times and was ultimately drawn to civil engineering because of concerns about environmental degradation, and eventually I decided to pursue a master's degree in environmental engineering. From there it was a bit serendipitous—Professor Clifford Randall was looking for a research assistant for an interesting wastewater treatment project, which became my thesis project. I think my superpower is being organized. I was also raised with a strong work ethic, which has served me well. Perhaps most importantly, I'm fortunate to get to work on problems that I'm genuinely interested in; the great thing about academia is that I'm more or less free to pursue thought-provoking research questions that I enjoy digging into. The hills are lit with the gold of aspen in Angel Fire, N.M. My coauthors and I noticed that the water reuse literature did a good job of describing the reasons that residents in some communities have opposed potable water reuse projects, and some studies even included an investigation into the demographic characteristics of those who are opposed to (or accepting of) water reuse. While this information might be generally useful, it is not necessarily user friendly; it doesn't help water planners and utilities figure out how to tailor their programming to the segments of the population that need particular kinds of education, outreach, and trust-building to allow residents to make informed decisions about water resources and reuse. We were aiming to develop an approach that would enable targeted public engagement and input on future water resource planning. The Albuquerque International Balloon Fiesta started in 1972. It is scheduled each year for the first week in October. Broadly, I care deeply about passing down a healthy planet to future generations. More specifically, with my water research I hope to contribute toward allowing communities in arid areas, such as the one in which I live, to continue to thrive in the face of climate change. With my chemicals research, I want to minimize people's exposure to hazardous chemicals, and I hope to contribute toward common-sense chemical-related policies that better prioritize health and the environment. I see two challenges as research at this intersection progresses. First, people don't want to give up conveniences that they currently enjoy. Whether we're thinking about moving away from flush toilets to alternatives that save water, or removing chemicals from consumer products that are found to be hazardous, there will be resistance to change. Second, as we move toward direct potable reuse of wastewater in more communities, we will need to consider whether and how current drinking water standards should be modified to account for potentially hazardous chemicals and/or if their upstream uses should be reduced or restricted through chemical policy changes. I moved a lot growing up, so I don't really have deep roots in one place. Perhaps a benefit was getting exposure to so many different parts of the United States, each with its own unique natural environment, water challenges, pollution issues, and other inspiration for a budding environmentalist. I spend as much time with my kids as possible, and in New Mexico we're lucky to have amazing outdoor activities at our doorstep—we take advantage of the skiing, walking in the bosque (river forest), and everything in between. I also enjoy painting and music, and recently started drum lessons with my older son. To learn more about Caroline's research, read the article, available online at https://doi.org/10.1002/aws2.1197. This article is part of the Topical Collection on Potable Reuse. Visit https://news.awwa.org/reuse-collection to learn more about this collection.

Estimated prenatal exposure to nitrate in drinking water and birth defects: A population-based cohort study of over half a million births in Denmark

Background/Aim: Prior studies have yielded inconsistent evidence from prior studies of an association between nitrate in drinking water and an increased risk of birth defects (BDs). The aim of this study was to assess maternal exposure to nitrate in drinking water and BDs in a large population-based cohort with high-quality individual-level exposure estimates.Methods: A cohort of 564,232 singleton live births that occurred among Danish parents during 1994-2004 was identified from the Danish Birth Registry and information on BDs was obtained from ICD-10 codes within the Danish National Patient Register. Estimates of average nitrate concentrations in drinking water during each pregnancy were linked to these births using data from a national water quality registry. Logistic regression with generalized estimating equations was used to assess the relationship between nitrate exposure and BDs and account for multiple births to the same mother. Nitrate exposure was modeled as both a categorical and continuous variable.Preliminary Results: In total, 31,568 cases of BDs were identified, including 8,101 congenital heart defects, 2,581 urinary defects, 1,986 orofacial clefts, and 1,662 digestive system defects. An elevated risk of any birth defect [adjusted odds ratio: 1.05 (95% confidence interval: 1.01, 1.09)] was observed when comparing the highest quartile of exposure (≥4.9 mg/L NO3-) to the lowest (≤1.1 mg/L NO3-). There was also evidence of a positive exposure-response in models using categorical (p for trend=0.02) and to a lesser extent for continuous (p=0.06) nitrate exposure. No clear evidence of an association was observed between nitrate and specific BDs.Conclusions: Our study is the most statistically powerful study to date examining the relationship between nitrate in drinking water and BDs. Maternal nitrate exposure was associated with increased risk of BDs and at levels below current drinking water standards, adding to the evidence that the current standard is not sufficiently protective.

Source and Quality of Groundwater Surrounding the Qinghai Lake, NE Qinghai‐Tibet Plateau

Comprehensive studies on the spatial distribution, water quality, recharge source, and hydrochemical evolution of regional groundwater form the foundation of rational utilization of groundwater resources. In this study, we investigated the water levels, hydrochemistry, and stable isotope composition of groundwater in the vicinity of the Qinghai Lake in China to reveal its recharge sources, hydrochemical evolution, and water quality. The level of groundwater relative to the level of water in the Qinghai Lake ranged from -1.27 to 122.91 m, indicating most of the groundwater to be flowing into the lake. The local evaporation line (LEL) of groundwater was simulated as δ2 H=6.08 δ18 O-3.01. The groundwater surrounding the Qinghai Lake was primarily recharged through local precipitation at different altitudes. The hydrochemical type of most of the groundwater samples was Ca-Mg-HCO3 ; the hydrochemistry was primarily controlled by carbonate dissolution during runoff. At several locations, the ionic concentrations in groundwater exceeded the current drinking water standards making it unsuitable for drinking. The main source of nitrate in groundwater surrounding the Qinghai Lake was animal feces and sewage, suggesting that groundwater pollution should be mitigated in areas practicing animal husbandry in the Qinghai-Tibet Plateau, regardless of industrial and urbanization rates being relatively low in the region. The scientific planning, engineering, and management of livestock manure and wastewater discharge from animal husbandry practices is a crucial and is urgently required in the Tibetan Plateau.

Health risks associated with multiple metal(loid)s in groundwater: A case study at Hetao Plain, northern China

To compare the health risks of multiple metal(loid)s in groundwater, and discuss the feasibility of drinking water standards, 66 groundwater samples were collected from the Hetao Plain in October 2017. Eighteen metal(loid) species (boron (B), manganese (Mn), iron (Fe), strontium (Sr), barium (Ba), lithium (Li), scandium (Sc), titanium (Ti), vanadium (V), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), selenium (Se), rubidium (Rb), molybdenum (Mo), uranium (U)) were analyzed, and the related non-carcinogenic risks were assessed. The results showed that 83.3% of the groundwater samples had As and Fe contents above the maximum allowed contaminant levels (MCLs) in drinking water standards, followed by Mn (70.2%), B (65.2%), Se (60.6%), U (18.2%), Ni (18.2%) and Mo (1.50%). Compared with the dermal exposure pathway, oral ingestion made a risk contribution of more than 99% for all target metal(loid)s. Site-specific hazard quotient (HQ) values ranged from 2.30E+00 to 1.75E+02, indicating that multiple metal(loid)s in the drinking groundwater cause a serious non-carcinogenic risk to the local people. The risk contributions (mean value) were ranked as As (55.2%) > U (25.5%) > Li (10.8%) > other total metal(loid)s (8.60%), and the contributions of U and Li could reach 91.7% (site 20) and 69.8% (site 56), respectively. The calculation of specific health risks further indicated that the MCLs of metal(loid)s do not match the corresponding health risk well. Some metal(loid)s such as Li that showed high exposure risks in this study, still have no MCL values until now. Therefore, current drinking water standards need to be updated.

Factors affecting microbiological quality of household drinking water supplied by small-scale ultrafiltration systems: A field study

Small scale ultrafiltration (UF) systems have been increasingly used in rural areas for drinking water supply, but their effectiveness in guarantying microbiological water safety at household level has rarely been assessed. Therefore, this study surveyed six representative villages where UF was utilized for full-scale drinking water supply for at least four years. At each village, the influent and the effluent from every stages of the treatment, as well as household tap water, were sampled and analyzed for microbiological indicating parameters, including total coliform count, Escherichia coli count, and heterotrophic plate count. The results were further assessed against current drinking water quality guidelines and standards. It was found that: (1) the qualification rate of household tap water samples varied substantially in the studied villages (0–75%), mainly due to the lack of post-disinfection and the occurrence of fecal contamination during water distribution; (2) UF appeared to be effective in controlling microbial contamination for small-scale systems with high-quality source water, while for systems using inferior source water, fecal contamination during water distribution necessitated continuous post-disinfection; and, (3) existing monitoring of membrane operational parameters cannot ensure microbial quality of treated water, and therefore, routine monitoring of microbial indicators in household water is recommended.

Elevated autoimmunity in residents living near abandoned uranium mine sites on the Navajo Nation

Specific autoantibodies were assessed among residents of the Navajo Nation in New Mexico chronically exposed to metal mixtures from uranium mine wastes and in drinking water supplies. Age and the extent of exposure to legacy waste from 100 abandoned uranium mine and mill sites were associated with antibodies to denatured DNA, previously known to be an early indicator of medication-induced autoimmunity. Surprisingly, autoantibodies to native DNA and/or chromatin were also linked to environmental exposure, specifically uranium consumption through drinking water for both men and women, while urinary arsenic was negatively associated with these autoantibodies in women. These findings suggest that contaminants derived from uranium mine waste enhanced development of autoantibodies in some individuals, while arsenic may be globally immunosuppressive with gender-specific effects. Specific autoantibodies may be a sensitive indicator of immune perturbation by environmental toxicants, an adverse effect not considered in current drinking water standards or regulatory risk assessment evaluations.

Nitrate in drinking water and colorectal cancer risk: A nationwide population-based cohort study.

Nitrate in drinking water may increase risk of colorectal cancer due to endogenous transformation into carcinogenic N-nitroso compounds. Epidemiological studies are few and often challenged by their limited ability of estimating long-term exposure on a detailed individual level. We exploited population-based health register data, linked in time and space with longitudinal drinking water quality data, on an individual level to study the association between long-term drinking water nitrate exposure and colorectal cancer (CRC) risk. Individual nitrate exposure was calculated for 2.7 million adults based on drinking water quality analyses at public waterworks and private wells between 1978 and 2011. For the main analyses, 1.7 million individuals with highest exposure assessment quality were included. Follow-up started at age 35. We identified 5,944 incident CRC cases during 23 million person-years at risk. We used Cox proportional hazards models to estimate hazard ratios (HRs) of nitrate exposure on the risk of CRC, colon and rectal cancer. Persons exposed to the highest level of drinking water nitrate had an HR of 1.16 (95% CI: 1.08-1.25) for CRC compared with persons exposed to the lowest level. We found statistically significant increased risks at drinking water levels above 3.87 mg/L, well below the current drinking water standard of 50 mg/L. Our results add to the existing evidence suggesting increased CRC risk at drinking water nitrate concentrations below the current drinking water standard. A discussion on the adequacy of the drinking water standard in regards to chronic effects is warranted.

Microbial community response reveals underlying mechanism of industrial-scale manganese sand biofilters used for the simultaneous removal of iron, manganese and ammonia from groundwater

Most studies have employed aeration–biofiltration process for the simultaneous removal of iron, manganese and ammonia in groundwater. However, what’s inside the “black box”, i.e., the potential contribution of functional microorganisms behavior and interactions have seldom been investigated. Moreover, little attention has been paid to the correlations between environmental variables and functional microorganisms. In this study, the performance of industrial-scale biofilters for the contaminated groundwater treatment was studied. The effluent were all far below the permitted concentration level in the current drinking water standard. Pyrosequencing illustrated that shifts in microbial community structure were observed in the microbial samples from different depths of filter. Microbial networks showed that the microbial community structure in the middle- and deep-layer samples was similar, in which a wide range of manganese-oxidizing bacteria was identified. By contrast, canonical correlation analysis showed that the bacteria capable of ammonia-oxidizing and nitrification was enriched in the upper-layer, i.e., Propionibacterium, Nitrosomonas, Nitrosomonas and Candidatus Nitrotoga. The stable biofilm on the biofilter media, created by certain microorganisms from the groundwater microflora, played a crucial role in the simultaneous removal of the three pollutants.

Environmentally Relevant Chronic Low-Dose Tritium and Gamma Exposures do not Increase Somatic Intrachromosomal Recombination in pKZ1 Mouse Spleen.

The toxicity of tritium is a public health concern given its presence and mobility in the environment. For risk predictions using radiological protection models, it is essential to allocate an appropriate radiation weighting factor (WR). This in turn should be consistent with the observed relative biological effectiveness (RBE) of tritium beta radiation. Although the International Commission on Radiological Protection (ICRP) currently recommends a WR of 1 for the calculation of committed effective dose for X rays, gamma rays and electrons of all energies, including tritium energies, there are concerns that tritium health risks are underestimated and that current regulatory tritium drinking water standards need revision. In this study, we investigated potential cytotoxic and genotoxic effects in mouse spleen after one month and eight months of chronic exposure to low-dose tritiated water (HTO). The dose regimes studied were designed to mimic human chronic consumption of HTO at levels of 10 kBq/l, 1 MBq/l and 20 MBq/l. The total doses from these radiation exposures ranged from 0.01 to 180 mGy. We also compared the biological effects of exposure to HTO with equivalent exposure to external whole-body 60Co gamma rays. Changes in spleen weight and somatic intrachromosomal recombination (DNA inversions) in spleen tissue of pKZ1Tg/+ mice were monitored. Our results showed no overall changes in either spleen organ weights and no increase mouse splenic intrachromosomal recombination frequencies, indicating that current drinking water standards for tritium exposure in the form of HTO are likely to be adequately protective against cytotoxic and genotoxic damage in spleen. These results demonstrate no evidence for cytotoxicity or genotoxicity in mouse spleen following chronic exposures to HTO activities (or equivalent gamma doses) up to 20 MBq/L.

Knowledge, attitudes and practice of desalinated water among professionals in health and water departments in Shengsi, China: a qualitative study.

Desalination has been considered as an essential way to solve water stress all over the world. Most of previous studies focused on its environmental impacts, energy consumption and desalination technologies rather than human health. However, the safety of desalinated water remains unclear. This study was undertaken to investigate the knowledge, attitude and practice (KAP) of the residents in an island county in eastern China to desalinated water. Seventeen people working in medical and water industries were recruited, and focus group discussion and in-depth interview were conducted among them. Our results showed that the majority of people interviewed knew the definition and local supply pattern of desalinated water, while some of them showed some concern about the safety and nutrition of desalinated water. Current drinking water standard has no specific item for desalination, so we strongly suggest issuing a standard for desalinated water.

Synchrotron-based imaging of chromium and γ-H2AX immunostaining in the duodenum following repeated exposure to Cr(VI) in drinking water.

Current drinking water standards for chromium are for the combined total of both hexavalent and trivalent chromium (Cr(VI) and Cr(III)). However, recent studies have shown that Cr(III) is not carcinogenic to rodents, whereas mice chronically exposed to high levels of Cr(VI) developed duodenal tumors. These findings may suggest the need for environmental standards specific for Cr(VI). Whether the intestinal tumors arose through a mutagenic or non-mutagenic mode of action (MOA) greatly impacts how drinking water standards for Cr(VI) are derived. Herein, X-ray fluorescence (spectro)microscopy (µ-XRF) was used to image the Cr content in the villus and crypt regions of duodena from B6C3F1 mice exposed to 180 mg/l Cr(VI) in drinking water for 13 weeks. DNA damage was also assessed by γ-H2AX immunostaining. Exposure to Cr(VI) induced villus blunting and crypt hyperplasia in the duodenum—the latter evidenced by lengthening of the crypt compartment by ∼2-fold with a concomitant 1.5-fold increase in the number of crypt enterocytes. γ-H2AX immunostaining was elevated in villi, but not in the crypt compartment. µ-XRF maps revealed mean Cr levels >30 times higher in duodenal villi than crypt regions; mean Cr levels in crypt regions were only slightly above background signal. Despite the presence of Cr and elevated γ-H2AX immunoreactivity in villi, no aberrant foci indicative of transformation were evident. These findings do not support a MOA for intestinal carcinogenesis involving direct Cr-DNA interaction in intestinal stem cells, but rather support a non-mutagenic MOA involving chronic wounding of intestinal villi and crypt cell hyperplasia.

Input and Leaching Potential of Copper, Zinc, and Selenium in Agricultural Soil from Swine Slurry

Trace elements, such as copper, zinc, and selenium, used as feed additives were determined in samples of both fresh (N = 14) and anaerobically digested (N = 6) swine slurry collected on medium- to large-size farms in northeast Spain. Considering both fresh and anaerobically digested samples, mean concentrations of zinc (1,500 mg kg(-1) dry mass [dm]) were greater than those of copper (mean 239 mg kg(-1 )dm), and the selenium concentrations detected were even lower (mean 139 μg kg(-1) dm). Zinc concentrations were significantly greater in anaerobically digested samples, whereas no significant differences were found for copper or selenium. In addition, the leaching potential of zinc, copper, and selenium in cropped (lettuce heart) and uncropped experimental units subject to drip irrigation was assessed in a greenhouse experiment. Generally, the addition of swine slurry to soil (1.7 g kg(-1) dm) significantly increased zinc, copper, and selenium concentrations in leachates, which decreased in accordance with the volume of leachate eluted. Under the experimental conditions, the leaching potential of zinc and selenium was more strongly correlated with bulk parameters directly associated with the composition of the pig slurry (dissolved organic carbon, electrical conductivity, and ammonium), whereas copper mobility was more strongly associated with the crop root exudates. Although selenium has been shown to be mobile in soil, the selenium content found in the leachates did not pose any appreciable risk according to current drinking water standards.

Using community economics to compare arsenic compliance and noncompliance

Arsenic regulation in drinking water sparked great controversy; rule‐makers sought to be protective of public health while remaining mindful of national compliance costs. The revised arsenic standard was finalized more than a decade ago, but more than 500 systems still remain noncompliant. The purpose of this study was to determine whether median household income (MHI) has played a role in compliance. Systems that had arsenic concentrations exceeding the current drinking water standard between 1998 and 2005 were split into three groups—compliant, noncompliant, and closed—based on their system status in 2011. MHI was assigned using census data for the primary county served. The median MHI of counties containing noncompliant systems ($44,694) falls below that of systems that reached compliance ($46,047) or were closed ($46,798) by 2011. Although the results indicate that income may play a factor in compliance, case studies also show that nonquantifiable factors have compliance implications.

Unknown Quantity: Regulating Radionuclides in Tap Water

Radioactivity surrounds us; each day we are exposed to a certain amount by virtue of being alive on planet Earth. Some of this exposure comes from radioactive substances (radionuclides) that occur naturally in a wide variety of geologic and soil formations. Occasionally these naturally occurring substances become more concentrated or accessible through human activities such as mining and nuclear energy production, resulting in greater potential for exposure than their original natural occurrence would suggest. Other radionuclides are artificially created. Residents in almost all parts of the United States live on lands that contain minor to substantial concentrations of radionuclides of one type or another.1 These substances often make their way into tap water, leading to exposures by ingestion, inhalation, or dermal pathways during showering or other contact with the water. Although radionuclides are widespread, there are large gaps in our knowledge about sources of these materials, their distribution, associated health risks, and mitigation measures. However, the information we do have suggests that current drinking water standards for radionuclides established by the U.S. Environmental Protection Agency (EPA) may not adequately protect health. The EPA is set to review these standards relatively soon, and the next two years are prime time for filling in numerous information gaps and doing other legwork to make sure the review is as well informed as possible.

Removal of arsenite by Fe(VI), Fe(VI)/Fe(III), and Fe(VI)/Al(III) salts: Effect of pH and anions

The removal of arsenate and arsenite from drinking water poses challenges, especially when arsenite is present in a significant amount. The removal of arsenite by K 2FeO 4, K 2FeO 4/FeCl 3, and K 2FeO 4/AlCl 3 salts was studied at pH 6.5 and at an initial As concentration of 500 μg As(III) L −1. The arsenite removal in Fe(VI)/Fe(III) and Fe(VI)/Al(III) systems was also examined as a function of pH (6.0–8.0). Arsenite was first oxidized by Fe(VI) to arsenate, which was subsequently removed through adsorption by Fe(III) or mixed Fe(III)–Al(III) oxy/hydroxide phases. Fe(VI)/Al(III) salts had higher removal efficiency of arsenite than Fe(VI) and Fe(VI)/Fe(III) salts. A molar ratio of 6(3/3):1 for Fe(VI)/Al(III) to As(III) decreased arsenite concentration from 500 to 1.4 μg L −1 at pH 6.5. Arsenite removal increased with a decrease in pH from 8.0 to 6.0 and exhibited less pH dependence in the Fe(VI)/Al(III) system than in the Fe(VI)/Fe(III) system. Aluminum chloride salts performed better than FeCl 3 and FeCl 3/AlCl 3 salts (Fe:Al = 1:1) in removing As(V) from water. Effect of anions (phosphate, silicate, bicarbonate, nitrate, and sulfate) on the arsenite removal by Fe(VI)/Al(III) salts at pH 6.5 was examined. Phosphate, silicate, and bicarbonate ions interfered with the removal of arsenite in water. Nitrate and sulfate had none to minimal effect on arsenite removal. Fe(VI)/Al(III) salts showed a potential for removing arsenite below the current drinking water standard (10 μg L −1).

High reuse potential of effluent from an innovative vertical submerged membrane bioreactor treating municipal wastewater

The main objective of this study is to investigate the reuse possibility of effluent from a vertical submerged membrane bioreactor (VSMBR) treating municipal wastewater. The average removal efficiencies of total chemical oxygen demand (COD), total nitrogen (T-N), and total phosphorus (T-P) were 96, 74, and 78%, respectively at 8-h hydraulic retention time (HRT) and 60-day sludge retention time (SRT). Additional removal of organic matter and improved nitrification and denitrification efficiencies were found by the formation of a dynamic membrane. The effluent quality of the vertical submerged membrane bioreactor (VSMBR) could satisfy most items in the current drinking water standards of Korea and the WHO (World Health Organization). Accordingly, the reuse of the effluent from the VSMBR could be possible for various purposes such as toilet flushing, sprinkling, and car washing.

Toxicity and Carcinogenicity of Chromium Compounds in Humans

Chromium is a human carcinogen primarily by inhalation exposure in occupational settings. Although lung cancer has been established as a consequence of hexavalent chromium exposure in smokers and nonsmokers, some cancers of other tissues of the gastrointestinal and central nervous systems have also been noted. Except for a few reports from China, little is known about the health risks of environmental exposures to chromium. Likewise, there has been a lack of epidemiological studies of human exposure to hexavalent Cr by drinking water or ingestion, and it has been suggested that humans can perhaps tolerate hexavalent Cr at higher levels than the current drinking water standard of 50 ppb. This review highlights the most recent data on the induction of skin tumors in mice by chronic drinking-water exposure to hexavalent chromium in combination with solar ultraviolet light. This experimental system represents an important new animal model for chromate-induced cancers by ingestion of drinking water, and it suggests by extrapolation that chromate can likely be considered a human carcinogen by ingestion as well. The potential use of this animal model for future risk assessment is discussed.