Municipal Water Source Research Articles

Resolving the source and mixing proportions of modern leakage to the Memphis aquifer in a municipal well field using geochemical and 3H/3He data, Memphis, Tennessee, USA

The Memphis aquifer in southwestern Tennessee is a confined to semi-confined unconsolidated sand aquifer and is the primary municipal water source for the Memphis metropolitan area. Leakage of modern water from shallow unconfined aquifers through the upper Claiborne confining unit locally degrades water quality in the Memphis aquifer and makes the aquifer more vulnerable to contamination. Major solute chemistry, tritium, and 3H/3He data were used to investigate the source and mixing proportions of modern water in the Memphis aquifer in the Davis well field, Memphis, Tennessee. Water quality in several production wells in the Davis well field has declined over the past 30 years, mainly through increased total dissolved solids, iron, alkalinity, and hardness. Trends in chemical data, tritium, and other hydrogeologic data support a source for the leakage from the Mississippi River Valley Alluvial aquifer. Mixing proportions of alluvial water in production well water obtained by inverse chemical modeling with PHREEQCi range from 7 to 45%. For two of the production wells, MLGW 414 and 432, 3H/3He data yield mixing ratios similar to those obtained from PHREEQCi in three of four cases; the dissimilar ratio is likely due to a poor solution from the PHREEQCi inverse modeling. Modeling of the age distribution obtained from MLGW 414 and 432 using an exponential-piston flow model (EPM) with an inverse solution computer code yielded mixed results. The EPM solution obtained for MLGW 414 converged with difficulty only for a 5-year transit time in the shallow aquifer and is consistent with a source from the Mississippi River Valley Alluvial aquifer; however, the modeled age of the water is greater than that observed. In comparison, the EPM solution for MLGW 432 converged for the 5- and 7-year transit periods in the shallow aquifer and yielded model ages consistent with observed 3H/3He ages; however, the extent of the maximum radii for infiltration source is not consistent with a Mississippi River Valley Alluvial aquifer source. Other potential sources for leakage to MLGW 432 include water from the Fluvial-terrace aquifer migrating along a fault east of the well field or infiltration of water from a lake south of the well field.

Retrospective Exposure Estimation for Perfluorooctanoic Acid (PFOA) for Participants in the C8 Health Project

O-30A6-2 Background/Aims: The primary source of PFOA in the environment of eastern Ohio and western West Virginia is believed to be the Washington Works facility. Percolation of deposited PFOA through the soil and pumping by industrial and municipal wells near the contaminated Ohio River is thought to explain elevated well water concentrations and human serum concentrations measured in recent years. Our objective is to estimate historical PFOA exposures and serum concentrations experienced by each of about 45,276 non-occupationally exposed participants in the C8 Health Project, based on their residential histories. Methods: We linked several environmental fate and transport models including AERMOD, PRZM3, BREZO, MODFLOW, and MT3D to simultaneously model PFOA air dispersion, transit through the unsaturated soil zone, surface water transport, and groundwater flow and transport. Annual PFOA exposure rates were estimated for each individual based on predicted calibrated water concentrations and predicted air concentrations, and default assumptions from the EPA Exposure Factors Handbook. Self-reported municipal water sources were verified using geocoded addresses and historical water distribution network maps for 6 municipal water districts. Individual exposure estimates were coupled with a one-compartment pharmacokinetic model to estimate annual serum PFOA concentrations. Results: Predicted water concentrations were within 2.3 times the observed mean water concentrations for all 6 municipal water districts. Predicted and observed median serum concentrations in 2005–2006 are 28.2 and 24.3 ppb, respectively (Spearman's rho = 0.66). Stratified by municipal water source at the time of the serum sample, Spearman rho ranges from 0.19 to 0.34. Conclusion: State-of-the-art fate and transport models provide the most defensible retrospective exposure estimates for epidemiologic studies when historical environmental measurements are lacking but source emissions rates are known. Our models predict recently observed municipal water PFOA concentrations and human serum PFOA concentrations surprisingly well, and will be used in a variety of epidemiologic studies being conducted in this region.

Effects of Iodine in Microbial Control of Dental Treatment Water

To determine the effects of low levels of iodine constantly present in the dental unit water system on microbial control of dental treatment water and biofilm control. This study used a dental unit water system simulator with eight dental unit waterline systems built to scale and function, each controlled via computer. Each of the eight units was operated independently, four units supplied with self-contained water reservoirs and four units supplied with municipal water. Four units were precleaned to remove biofilm buildup. The study had a well-balanced design with equal representation (variables) of presence/absence of biofilms, selfcontained reservoirs for introduction of treatment water, source water directly connected to municipal water source and iodinated cartridges within the self-contained reservoirs and between municipal water and dental unit. Point-of-use iodinated resin cartridges (IRC) were retrofitted proximal to handpiece and air/ water syringe tip lines in four units, and iodinated resin water cartridges (IRSWC) were fitted to the other four units at the source water output. Heterotrophic plate counts were performed at baseline and twice weekly for a period of 6 weeks. One representative waterline sample was taken from each group at baseline and end-of-study to analyze changes in biofilm status using scanning electron microscopy. Waterlines not previously contaminated with biofilms did not show organization of biofilm matrix in units equipped with IRSWC. Constantly present low levels of iodine, demonstrated some disruption of biofilms in waterlines already contaminated with mature biofilms. All groups showed contamination levels < 500 cfu/ml (colony forming units per milliliter) consistent with the CDC and ADA guidelines. In this 6 weeks study, IRSWC equipped waterlines showed disruption of established biofilms, controlled formation of new biofilms in clean lines and rendered the dental treatment water < 500 cfu/ml. Point-of-use iodinated resin cartridges were also effective in controlling contamination in the dental treatment water. Dental unit water systems that are in use get contaminated with microbes and biofilms in weeks of being put into use. These biofilms contaminate the treatment water thereby putting patients and staff at risk of infection by predominantly gram-negative microbes. Biofilms in the water systems must be cleaned periodically with a strong decontaminant and the dental treatment source water needs to be modified with a low-grade antimicrobial that can preserve the water quality yet safe to humans. In this translational research study, we evaluate the effects of elemental iodine dissolved in water flowing through an iodine containing cartridge in controlling biofilm and dental treatment water contamination using a dental unit water system simulator, prior to clinical utilization.

Disinfection By-products: A Question of Balance

Disinfection By-products: A Question of Balance

Investigation of an epidemic of Hepatitis E in Nellore in south India

To determine the incidence of acute hepatitis because of hepatitis E virus (HEV) and the source of the epidemic in Nellore in south India in 2008. Anti-HEV IgM ELISA and RT-PCR for HEV-RNA were carried out on blood and stool samples from patients with acute hepatitis presenting to different hospitals in the city. The city was divided into 33 clusters, and 20 families from each cluster were systematically interviewed to determine the incidence of hepatitis E in the city. The survey was conducted on 2685 residents of 673 households from 24th November to 4th December 2008. The overall incidence of hepatitis was 5.7% (152/2685), i.e. an estimated 23,915 persons in the city were affected. There were two deaths because of acute hepatitis in the population surveyed translating to an estimated 315 deaths. Men had higher attack rates than women (7.8%vs. 3.5%) and young adults compared to children under 5 years (6.9%vs. 2.9%). Families drinking water from the pumping station at Bujjamarevu had the highest attack rate of 54.5% (39.8-69.2%). HEV IgM antibodies were present in 80/100 plasma samples tested. HEV-RNA was detected in 43/100 individuals tested, and isolates were characterized as genotype 1 by sequencing. Sewage draining into the river close to the pumping stations and broken pipelines crossing sewage drains may have triggered this large outbreak.

Polymorphisms in GSTT1 , GSTZ1 , and CYP2E1 , Disinfection By-products, and Risk of Bladder Cancer in Spain

BackgroundBladder cancer has been linked with long-term exposure to disinfection by-products (DBPs) in drinking water.ObjectivesIn this study we investigated the combined influence of DBP exposure and polymorphisms in glutathione S-transferase (GSTT1, GSTZ1) and cytochrome P450 (CYP2E1) genes in the metabolic pathways of selected by-products on bladder cancer in a hospital-based case–control study in Spain.MethodsAverage exposures to trihalomethanes (THMs; a surrogate for DBPs) from 15 years of age were estimated for each subject based on residential history and information on municipal water sources among 680 cases and 714 controls. We estimated effects of THMs and GSTT1, GSTZ1, and CYP2E1 polymorphisms on bladder cancer using adjusted logistic regression models with and without interaction terms.ResultsTHM exposure was positively associated with bladder cancer: adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were 1.2 (0.8–1.8), 1.8 (1.1–2.9), and 1.8 (0.9–3.5) for THM quartiles 2, 3, and 4, respectively, relative to quartile 1. Associations between THMs and bladder cancer were stronger among subjects who were GSTT1 +/+ or +/− versus GSTT1 null (pinteraction = 0.021), GSTZ1 rs1046428 CT/TT versus CC (pinteraction = 0.018), or CYP2E1 rs2031920 CC versus CT/TT (pinteraction = 0.035). Among the 195 cases and 192 controls with high-risk forms of GSTT1 and GSTZ1, the ORs for quartiles 2, 3, and 4 of THMs were 1.5 (0.7–3.5), 3.4 (1.4–8.2), and 5.9 (1.8–19.0), respectively.ConclusionsPolymorphisms in key metabolizing enzymes modified DBP-associated bladder cancer risk. The consistency of these findings with experimental observations of GSTT1, GSTZ1, and CYP2E1 activity strengthens the hypothesis that DBPs cause bladder cancer and suggests possible mechanisms as well as the classes of compounds likely to be implicated.

Seroprevalence of hepatitis A antibodies among children in a Saudi community

Objective To determine the current seroprevalence of antibodies against hepatitis A virus in selected group of children aged 1-6 years in Northern borders region, Saudi Arabia, and to identify risk factors for infection. Methods A cross-sectional sero-epidemiological study of 950 children who attended 10 randomly selected primary health care centers (5 urban and 5 rural) was done. Parents of all children were subjected to a questionnaire including sociodemographic and housing environmental data. The determination of anti-HAV antibodies was carried out by ELISA-test. Results The prevalence of HAV-IgG was 33.8% overall, 35.5% among males and 32.0% among females with no statistically significant difference. Multivariate logistic regression analysis revealed that increasing age, rural residence, non Saudi nationality, and non availability of safe municipal water source were the most important independent predictors for HAV seropositivity in the studied children. Conclusions There is a clear decrease in hepatitis A prevalence in the studied children particularly in urban areas and indicates that a transition may be underway to intermediate endemicity and possible shift of the risk to the adult age with increased morbidity. So, we recommend including Hepatitis A in the schedule of routine childhood vaccinations.

Municipal drinking water source protection in low income countries: Case of Buea municipality- Cameroon

Source water contamination poses a risk to public health and increases the cost of drinking water treatment. Source water protection is a proactive approach for the enhancement of drinking water quality and quantity. A combination of research methods (desk review, interviews and reconnaissance field appraisal) have been used to identify major drinking water sources in Buea, land use activities which constitute potential threats and pathways of contamination of these sources as well as the capacity for source water protection in Buea. Our findings revealed that anthropogenic activities around the six major drinking water sources studied present visible potential threats and pathways for contamination, and that source water protection has not been given adequate attention in the planning and development of Buea. The potential human and social capacities are limited by the lack of financial and technical resources. This is further compounded by the fact that institutional arrangement does not facilitate the integration of land and water management at the local level. A framework for local strategic multi-stakeholder source water protection with the potential to foster leadership, pull together available resources from different stakeholders and reduce potential resistance to the integration of land and water management has been proposed. There is an urgent need for the adoption of a precautionary approach and research to develop baseline data that will enable comprehensive source water protection measures.

Effect of chemical environments on stress cracking of poly(ethylene terephthalate) beverage bottles

The influence of environmental factors on stress cracking in poly(ethylene terephthalate) beverage bottles was evaluated using failure rate data for sets of bottles stored in shallow puddles of aqueous solutions. Humidity and water alkalinity greatly affected bottle failure. Surprisingly, contact of bottles with water having alkalinity greater than that which is found in municipal water sources did not result in failure if evaporation of the water was prevented. During evaporation under conditions of high humidity, aqueous solutions of sodium bicarbonate became more concentrated and lost carbon dioxide to contain more basic and more nucleophilic anions. A mechanism for environmental stress cracking of PET including transformation of bicarbonate anions to carbonate and hydroxide anions during solution evaporation followed by hydrolysis of ester bonds is proposed.

Managing Gulls to Reduce Fecal Coliform Bacteria in a Municipal Drinking Water Source

Author(s): Nugent, Benjamin; Gagne, Kevin; Dillingham, Mary Jane | Abstract: Large numbers of ring-billed gulls, herring gulls, and greater black-backed gulls roost each night on a municipal drinking water source in Maine and have been identified as the primary source of elevated fecal coliform bacteria levels. The lake has a resident gull population of approximately 800, while more than 3,000 gulls have been observed during seasonal migration. To alleviate this public health concern, the U.S. Department of Agriculture APHIS Wildlife Services program implemented an Integrated Wildlife Damage Management program in 2005. The program included the use of pyrotechnics and watercraft to harass gulls, as well as shooting to reinforce and enhance the effectiveness of non-lethal methods. Management activities were effective in keeping gulls off the drinking water source and lowering coliform bacteria levels to within EPA water quality standards. Additionally, the integrated program also involves an ongoing survey in areas surrounding the lake to identify feeding, loafing, and roosting areas that may affect gull movement. Information collected from the survey will result in more effective management practices and contribute to the long-term goal of reducing gull use on the lake.

Virus occurrence in municipal groundwater sources in Quebec, Canada

A 1 year study was undertaken on groundwater that was a source of drinking water in the province of Quebec, Canada. Twelve municipal wells (raw water) were sampled monthly during a 1 year period, for a total of 160 samples. Using historic data, the 12 sites were categorized into 3 groups: group A (no known contamination), group B (sporadically contaminated by total coliforms), and group C (historic and continuous contamination by total coliforms and (or) fecal coliforms). Bacterial indicators (total coliform, Escherichia coli, enteroccoci), viral indicators (somatic and male-specific coliphages), total culturable human enteric viruses, and noroviruses were analyzed at every sampling site. Total coliforms were the best indicator of microbial degradation, and coliform bacteria were always present at the same time as human enteric viruses. Two samples contained human enteric viruses but no fecal pollution indicators (E. coli, enterococci, or coliphages), suggesting the limited value of these microorganisms in predicting the presence of human enteric viruses in groundwater. Our results underline the value of historic data in assessing the vulnerability of a well on the basis of raw water quality and in detecting degradation of the source. This project allowed us to characterize the microbiologic and virologic quality of groundwater used as municipal drinking water sources in Quebec.

Analysis of volatiles and semivolatiles in drinking water by microextraction and thermal desorption

A new technique to analyze aqueous samples for nanograms per liter levels of volatile and semivolatile compounds using microextraction and thermal desorption into a gas chromatograph/ion trap mass spectrometer (GC/MS) is described. This method is inherently sensitive (50 mL of aqueous sample is extracted prior to each desorption), uses no solvents, and detects volatiles and semivolatiles in the same analysis. Aqueous standards and environmental samples are pumped through a length of porous-layer open-tubular capillary column, which is then thermally desorbed onto a 30 m × 0.25 mm i.d. analytical column interfaced to an ion trap mass spectrometer for subsequent separation and detection. Sharp chromatographic peaks and reproducible retention times (RT) were observed. Replicate injections of surrogates ( n = 6) averaged 32.6% R.S.D. Analysis of domestic tap water detected 55 analytes, some at the low-nanograms per liter level, and detected 3 halogenated ethenes, not previously reported in drinking water. Analysis of an aqueous sample from a municipal ground water source detected the presence of numerous semivolatile compounds at trace-levels.

Mycobacterium abscessus in a long-term respiratory care unit

BACKGROUND/OBJECTIVES: Nontuberculous mycobacteria (NTM) can cause nosocomial outbreaks of disease and are transient in municipal water. In August 2001 and May 2002, bronchoscopic alveolar lavage cultures reported <i>Mycobacterium abscessus.</i> As this organism was never encountered at our facility, which included long-term ventilator patients, an investigation was undertaken. The initial investigation, which focused on the immediate environmental areas for a source of this outbreak, was negative. A third case was identified from bronchoscopic washings in March 2003. The occurrence of three ventilator cases prompted us to further investigate the occurrence and hopefully identify a point source, as this organism is not communicably disseminated. METHODS: We cultured all long-term ventilator patients and non-ventilator patients on the long-term respiratory unit to identify colonization. The investigators reviewed common exposures, measurement of the unit as a risk factor, environmental, equipment, and water sources in patient rooms and common areas. We widened our search for <i>Mycobacterium abscessus</i> by doing a prevalence study of ventilator patients on all other respiratory units. RESULTS: A total of 28 patients were investigated over a 3-year period. <i>Mycobacterium abscessus</i> was identified in 11 patients, and 2 additional patients were identified who were colonized with other NTM. A point source in the environment was not identified. However, environmental interventions took place such as removal of aquariums in all patient areas and adequate cleaning of ice machines and change of filters. SUMMARY/RECOMMENDATIONS: Identifying a point source for an outbreak of this organism can be challenging. As the organism is waterborne, we sought to identify environmental areas in which this may be a concern. Aquariums, municipal water source, ventilation system, ice machines, and bronchoscopes were investigated. <i>Mycobacterium abscessus</i> was not isolated, however other atypical mycobacteria were encountered in the aquarium and ice machine cultures <i>(Mycobacterium fortuitum, Mycobacterium chelonae,</i> respectively). <i>Mycobacterium abscessus</i> was absent in all cultures. As the organism may not be identified in patients during prolonged intervals, we continue to investigate for its occurrence. As of January 2004, no new cases have been identified. Our investigation led us to work closely with the Massachusetts Department of Public Health and the Centers for Disease Control and Prevention (CDC).

Performance and Cost Evaluations of Synthetic Resin Technology for the Removal of Methyl Tert -Butyl Ether from Drinking Water

This study investigated the performance of synthetic carbonaceous resin technology for the treatment of methyl tert-butyl ether (MTBE) contaminated waters using rapid small-scale column tests (RSSCTs). The RSSCTs were conducted using Ambersorb 563 carbonaceous resin (Rohm and Haas Corp., Philadelphia, Pa.) under multisolute conditions of typical municipal water source, soluble fuel components or additive/by-product, and MTBE. Specifically, one RSSCT column run was conducted with groundwater from Arcadia Wellfield, Santa Monica, Calif., with tert-butyl alcohol (TBA) and MTBE, while the other RSSCT column run was performed with surface water from Lake Perris, Calif., with benzene, toluene, p-xylene (BTX) and MTBE. The results obtained were compared to RSSCTs performed using PCB coconut shell granulated activated carbon (GAC) (Calgon Corp., Philadelphia, Pa.). The adsorbent comparisons indicate that the performance (as characterized by indicators such as carbon usage rates or integrated column capacity) of the Ambersorb 563 synthetic resin in multisolute conditions of TBA or BTEX with MTBE in typical municipal water source is significantly superior to that of the coconut shell PCB GAC. Cost comparison for the coconut shell GAC and synthetic resin system was also performed. Under multisolute conditions of typical municipal water source, flow rates, and influent MTBE concentrations, the cost of the resin system, for most of the scenarios evaluated, is demonstrated to be significantly lower than the complementary GAC system under the costing procedure used. Further, when soluble fuel components such as BTX or fuel additives/byproducts such as TBA were present along with MTBE, the predicted higher adsorbent usage rates for the coconut shell GAC were translated into significantly higher treatment costs relative to the synthetic carbonaceous resin system.

The Influence of Coal Quality Variation on Utilization of Water from Abandoned Coal Mines as a Municipal Water Source

As population increases and high quality water becomes more difficult to obtain, many communities will seek alternative water supply sources. Some municipalities have realized that they have a reservoir of unexploited water readily available in abandoned underground coal mines. Analysis of the mine’s history, the quality of the coal and water that reside within the mine, and knowledge of local hydrology, geology, and mine chemistry will provide communities with the information they need to determine the best mine sites to use.

Irrigating Landscape Bedding Plants and Cut Flowers With Recycled Nursery Runoff and Constructed Wetland Treated Water

Abstract Direct nursery runoff (runoff), wetland treated recycled nursery runoff (recycled), and a municipal water source (tap) with and without elevated salt (NaCl targeted injection to 3.0 dS·m−1) levels were tested as potential drip irrigation sources for production of in-ground cut flower crops and landscape bedding plants. Two species of cut flowers, Helianthus annuus L. ‘Mammoth’ (sunflower) and Gladiolus hortulanus L. ‘Tout A Toi’ (gladiolus), and two bedding plants, Catharanthus roseus G. Don ‘Pacifica Red’ (vinca) and Zinnia elegans N.J. von Jacquin ‘Lilliput Mixed Colors’ (zinnia), were established in trial beds irrigated with the four water treatments during the summer of 2001 as a warm season experiment. A second experiment was conducted from November 2001 to May 2002 to investigate growth and flowering responses of two species of cut flower crops [Consolida ambigua (L.) P Ball &amp; V Heywood (larkspur) and Narcissus tazetta L. ‘Galilea’ (paperwhite narcissus)] and two bedding plants [Antirrhinum majus L. ‘Montego Mix’ (snapdragons) and Viola × wittrockiana H. Gams ‘Crown Mix’ (pansies)]. Marketable crops of sunflower, paperwhite narcissus, and larkspur were produced with all four water treatments. Direct nursery runoff, recycled wetland treated water, and NaCl spiked water that were high in soluble salts during the heat of summer reduced yield and inflorescence diameter with sunflowers, but only slightly reduced inflorescence quality and had no effect on yield of paperwhite narcissus. These three treatments also affected stand density, but not yield of cut larkspur inflorescences in the cool season. Irrigation with water containing elevated NaCl levels reduced flower counts on pansies and growth indices on pansies and snapdragons over much of the growing season, but reduced snapdragon flowering only in spring. Vinca was unaffected by the irrigation treatments. Zinnia survival and flowering were reduced or delayed by irrigation with recycled or elevated NaCl water.

The geochemistry and mixing of leakage in a semi-confined aquifer at a municipal well field, Memphis, Tennessee, USA

The Memphis aquifer in southwestern Tennessee is confined to a semi-confined unconsolidated sand aquifer and is the primary municipal water source in the Memphis metropolitan area. Past studies have identified regions in the metropolitan area in which the overlying upper Claiborne confining unit lacks significant clay and provides a hydraulic connection between the shallow aquifer and the Memphis aquifer. In this study, major solute chemistry, 3H, and 3H/ 3He groundwater dating are used to investigate the extent and chemical effects of leakage through the confining unit to the Memphis aquifer in the vicinity of a municipal well field. The 3H/ 3He dates and geochemical modeling of the chemical data are used to constrain mixing fractions and the timing of modern recharge. Tritium activities of as much as 2.8 TU are observed in shallow production wells, but deeper production wells have 3H activities that approach the detection limit. Trends in water chemistry indicate vertical mixing in the aquifer of shallow Na–SO 4–Cl-rich water and deeper Ca–Mg–HCO 3-rich water. Water chemistry does not vary consistently with seasonal pumping, but 3H activity generally decreases during low use periods. Stable O and H isotopes show little variation and are not useful groundwater tracers for this study. The 3H-bearing, Na–SO 4–Cl-rich water is interpreted to reflect recharge of modern water through the upper Claiborne confining unit. The 3H/ 3He dates from 5 production wells indicate modern recharge, that infiltrated 15–20 a ago, is present in the shallow production wells. Geologic data and hydrologic boundary conditions suggest that the most likely source for continued leakage is a nearby stream, Nonconnah Creek. Geochemical reaction modeling using the NETPATH computer code suggests that proportions of shallow aquifer water leaking into the Memphis aquifer range from 6 to 32%. The 3H/ 3He dating and NETPATH modeling results correlate well, suggesting that these complementary analytical tools provide an effective means to evaluate proportions of modern water leaking into semi-confined aquifers. These results also indicate a need to carefully consider connections between surface water and semi-confined groundwater resources in wellhead protection programs.

Exposure to tap water during pregnancy.

Studies of disinfection byproducts (DBPs) in drinking water and risk of adverse reproductive outcome have usually relied on approximate measures of exposure. Individual differences in consumption of bottled or filtered water, variability in tap water consumption at home and at work, dermal and inhalation exposure to volatile contaminants, and changes in residency during pregnancy may lead to exposure misclassification. We characterized exposures to tap water and other risk factors among 71 pregnant and 43 non-pregnant women attending public health clinics. Nearly all residences had a municipal water source, but 25% of women drank filtered or bottled water. Fifty percent of the women in our sample reported working outside the home where, on average, one third of their daily water intake took place. Pregnant women consumed more water than non-pregnant women (3.4 vs. 3.0 total l/day), especially cold tap water at home (1.8 vs. 1.3 l/day, 95% CI for the difference=0.1, 0.9). Patterns of showering were similar for both groups of women, but pregnant women were more likely to bathe and to bathe more frequently. The prevalence of smoking was lower among pregnant women (22.5% vs. 32.6%), as was the consumption of alcohol (4.2% vs. 53.5%, 95% CI for the difference=-64.9, -33.7). Thirty-two percent of women had moved during their current pregnancy. The data reaffirm the importance of collecting individual-level data for water consumption and exposure to potential confounders to avoid misclassification bias. This study is the first to target women of low socio-economic status (SES) and therefore of particular interest in studies of adverse reproductive outcomes for which this group is at increased risk.

The effect of a dental unit waterline treatment regimen on the shear bond strength of resin-based composite

Numerous methods of disinfecting dental waterlines have been suggested. This study evaluates the effects of one disinfecting technique on the strength of resin-based composite's bond to enamel and to dentin. The authors bonded resin-based composite cylinders to enamel and dentin surfaces similarly mounted and prepared using three irrigation solutions. After undergoing acid etching, the tooth surface was rinsed with either distilled water, water from a municipal water source or a mixture of distilled water and mouthwash concentrate. The authors shear-tested the samples and analyzed the data statistically. The group rinsed with distilled water mixed with mouthwash exhibited the lowest shear bond strengths. However, a one-way ANOVA indicated no statistically significant differences in the mean values among the treatment groups for either enamel (P = .295) or dentin (P = .393). Specimens bonded to enamel demonstrated primarily adhesive fracture at the tooth/composite interface. Those bonded to dentin showed a similar pattern, with some sites of cohesive fracture in the resin-based composite. There was no significant difference in shear bond strengths of resin-based composite to tooth structure when rinsed with distilled water mixed with mouthwash, distilled water or water from a municipal source. Dental unit waterlines disinfected using a diluted mouthwash solution may be used while bonding resin-based composite to either enamel or dentin.

Reflective coating for sunlight, paint outside a spraybooth, and case-by-case MACT for in-mold painting

Existing desalination capacity and the prospects for future adoption varies across US states and differs for brackish water and seawater. Brackish water desalination—treatment of waters with dissolved solids of 1000 and 10,000 milligrams per liter (mg/L)—in states like Florida, California, and Texas has made the United States a global leader in this type of desalination. In contrast, the United States has only a limited number of municipal seawater desalination facilities. As of 2015, treated brackish water and seawater were not significant municipal water sources at the national level; water from desalination represented less than 1% of US municipal water supplies. This situation, however, does not reflect the future role that desalination may play in addressing regional and local shortages of developed freshwater supplies.