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PubMed1990

Comprehensive Health Effects Testing Program for Denver's Potable Water Reuse Demonstration Project.

The Comprehensive Health Effects Testing Program for the Denver Water Department's Potable Water Reuse Demonstration Project is designed to evaluate the relative health effects of highly treated reclaimed water derived from secondary wastewater compared to Denver's present high-quality drinking water. The 1 million gallon per day (1 mgd) demonstration plant provides water to be evaluated in the studies treating unchlorinated secondary treated wastewater with the following additional processes: high pH lime clarification, recarbonation, filtration, ultraviolet irradiation, activated carbon adsorption, reverse osmosis, air stripping, ozonation, and chloramination. An additional sample is obtained from the identical treatment process substituting ultrafiltration for reverse osmosis. The toxicology tests to evaluate the possible long-term health effects are chronic toxicity and oncogenicity studies in Fischer 344 rats and B6C3F1 mice and reproductive/teratology in Sprague-Dawley rats. The results of these evaluations will be correlated with microbiological, chemical, and physical test results to establish the relative quality of reclaimed water compared to all established health standards as well as Denver's pristine drinking water.

Animals↗
PubMed2005

Stem photosynthesis not pressurized ventilation is responsible for light-enhanced oxygen supply to submerged roots of alder (Alnus glutinosa).

BACKGROUND AND AIMS: Claims that submerged roots of alder and other wetland trees are aerated by pressurized gas flow generated in the stem by a light-induced thermo-osmosis have seemed inconsistent with root anatomy. Our aim was to seek a verification using physical root-stem models, stem segments with or without artificial roots, and rooted saplings. METHODS: Radial O2 loss (ROL) from roots was monitored polarographically as the gas space system of the models, and stems were pressurized artificially. ROL and internal pressurization were also measured when stems were irradiated and the xylem stream was either CO2 enriched or not. Stem photosynthesis and respiration were measured polarographically. Stem and root anatomy were examined by light and fluorescence microscopy. KEY RESULTS: Pressurizing the models and stems to <or=10 kPa, values much higher than those reportedly generated by thermo-osmosis, created only a negligible density-induced increase in ROL, but ROL increased rapidly when ambient O2 concentrations were raised. Internal pressures rose by several kPa when shoots were exposed to high light flux and ROL increased substantially, but both were due to O2 accumulation from stem photosynthesis using internally sourced CO2. Increased stem pressures had little effect on O2 transport, which remained largely diffusive. Oxygen flux from stems in high light periods indicated a net C gain by stem photosynthesis. Chloroplasts were abundant in the secondary cortex and secondary phloem, and occurred throughout the secondary xylem rays and medulla of 3-year-old stems. Diurnal patterns of ROL, most marked when light reached submerged portions of the stem, were modified by minor variations in light flux and water level. Low root temperatures also helped improve root aeration. CONCLUSIONS: Pressurized gas flow to submerged roots does not occur to any significant degree in alder, but stem photosynthesis, using internally sourced CO2 from respiration and the transpiration stream, may play an important role in root aeration in young trees and measurably affect the overall carbon balance of this and other species.

Alnus↗
PubMed1998

Trace elements and micropollutant anions in the dialysis and reinfusion fluid prepared on-line for haemodiafiltration.

Exposure to the trace elements and micropollutions of tap water may be very considerable in dialysis patients. As few data on trace elements in reinfusion and dialysis fluid for haemodiafiltration (HDF) have been reported, we studied nine trace elements (microg/l; Al, As, Cd, Cr, Cu, Hg, Pb, Se, Zn) and five anions (mg/l; F-, NO2-, NO3-, PO4(3-), SO4(2-)) in tap water, in water after two passages of reverse osmosis (2RO), in dialysate and in on-line prepared reinfusate. NO3- and SO4(2-) were somewhat elevated in our tap water (22.2+/-7.6 and 21.8+/-11.3 mg/l) but decreased (P<0.001) after 2RO (1.4+/-1.5 and 0.9+/-1.1 mg/l); the other anions, which were at a very low level, remained unchanged. All trace elements decreased, with statistical significance only for Al, Cr and Zn from 14.9+/-19.9, 2.6+/-0.6 and 35.1+/-41.1 microg/ to 3.2+/-2.1, 0.2+/-0.2 and 3.5+/-4.8 microg/l, respectively. Due to impurities in concentrate salts for Al (5.4+/-3.1), Cr (0.5+/-0.4) and SO4(2-) (2.4+/-1.8), greater concentrations were found in dialysate and reinfusate than in tap water after 2RO (P<0.03). For all measurements, trace elements and anions were at acceptable levels according to international standards. Simultaneous determinations of trace elements at inflow (Din) and outflow (Dout) of the dialysate as well as in plasma or in whole blood at the beginning of on-line HDF documented Dout/Din>1 for Al, Cu and Zn and a positive gradient between the concentration in blood and dialysate inlet. In conclusion, our dialysate and reinfusate can be considered safe regarding trace elements and micropollution: two passages through reverse osmosis reduces the concentrations of trace elements and anions. The impurities of concentrates are acceptable. Accumulation or depletion of trace elements should be evaluated after longitudinal studies of plasma concentrations.

Anions↗
PubMed2004

Induced-charge electrokinetic phenomena: theory and microfluidic applications.

We give a general, physical description of "induced-charge electro-osmosis" (ICEO), the nonlinear electrokinetic slip at a polarizable surface, in the context of some new techniques for microfluidic pumping and mixing. ICEO generalizes "ac electro-osmosis" at microelectrode arrays to various di-electric and conducting structures in weak dc or ac electric fields. The basic effect produces microvortices to enhance mixing in microfluidic devices, while various broken symmetries--controlled potential, irregular shape, nonuniform surface properties, and field gradients--can be exploited to produce streaming flows. Although we emphasize the qualitative picture of ICEO, we also briefly describe the mathematical theory (for thin double layers and weak fields) and apply it to a metal cylinder with a dielectric coating in a suddenly applied dc field.

Journal Article↗
PubMedDate not supplied

The Fresenius Medical Care home hemodialysis system.

The Fresenius Medical Care home dialysis system consists of a newly designed machine, a central monitoring system, a state-of-the-art reverse osmosis module, ultrapure water, and all the services associated with a successful implementation. The 2008K@home hemodialysis machine has the flexibility to accommodate the changing needs of the home hemodialysis patient and is well suited to deliver short daily or prolonged nocturnal dialysis using a broad range of dialysate flows and concentrates. The intuitive design, large graphic illustrations, and step-by-step tutorial make this equipment very user friendly. Patient safety is assured by the use of hydraulic systems with a long history of reliability, smart alarm algorithms, and advanced electronic monitoring. To further patient comfort with their safety at home, the 2008K@home is enabled to communicate with the newly designed iCare remote monitoring system. The Aquaboss Smart reverse osmosis (RO) system is compact, quiet, highly efficient, and offers an improved hygienic design. The RO module reduces water consumption by monitoring the water flow of the dialysis system and adjusting water production accordingly. The Diasafe Plus filter provides ultrapure water, known for its long-term benefits. This comprehensive approach includes planning, installation, technical and clinical support, and customer service.

Equipment Design↗
PubMed1978

Preparative isolation of middle molecular weight fractions from the hemofiltrate of patients with chronic uremia.

Fractions in the molecular weight range of the so-called middle molecules (500--3000 daltons) were isolated on a preparative scale from hemofiltrate of patients. Hemofiltration was performed with an RP-6 dialyzer using a predilution technique. The hemofiltrate was concentrated and desalinated by reverse osmosis with membranes with a normal cut-off of 500 daltons. The retentate was freeze-dried, redissolved in volatile buffer and fractionated on Sephadex G-15 macrocolumns. The middle molecule molecular weight range in the elution profiles (detected at 206 and 280 nm simultaneously) was marked with peptides. Isolated fractions in the middle molecule molecular weight range showed strong inhibitory activity upon 3H-thymidine incorporation into rat bone-marrow cells in vitro. The described combination of hemofiltration, reverse osmosis and gel chromatography is suggested as a useful approach to the isolation of these ninhydrin-positive substances which, according to their proved heterogeneity, are to be subfractionated by further procedures.

Chromatography, Gel↗
PubMed1990

Isotonic secretion via frog skin glands in vitro. Water secretion is coupled to the secretion of sodium ions.

In isolated frog skin at least three different types of cells are engaged in the transepithelial ion and water transport; these are the granular cells, the mitochondria-rich cells and the glandular cells. The experiments presented were carried out on isolated frog skin bathed in Cl- or NO3- Ringer's solution, where the active transepithelial Na+ uptake via the granular cells was blocked by amiloride. Transepithelial current and water flow were measured. When a negative current was passed across the skins (the skins were clamped at -100 mV), the current was mainly carried by a net influx of Cl- via the mitochondria-rich cells. The current had no effect on the transepithelial water movement. This finding indicates that there is nearly no coupling between the Cl- flux and the movement of water via the mitochondria-rich cells. Prostaglandin E2 activates the glandular cells of the exocrine glands in the skin. When prostaglandin E2 was added under these experimental conditions (the skins were clamped at -100 mV, with amiloride in the apical bathing solution, and the glandular secretion of ions was blocked by the use of NO3- Ringer's solution), then the transepithelial current became more negative. This change in current was mainly due to an increase in the Na+ efflux via the glands. Thus PGE2 increase the Na+ conductance of the skin glands. Together with this increase in the Na+ efflux a highly significant increase in the water secretion was observed. The water movement (secretion) across the skin was under these conditions coupled to the PGE2-induced efflux of Na+, and when one Na+ was pulled from the basolateral to the apical solution via this pathway 215 molecules of water followed. This must be due to electro-osmosis (friction between ions and water) or current-induced local osmosis.

Animals↗
PubMedDate not supplied

The influence of bacteria in dialysis water on its endotoxin level.

The influence of bacteria in dialysis water and its endotoxin level is one of the main important issues of purified water for haemodialysis. The current methods, assessing the number of water bacteria, are insufficient; due to their large diversity, only a small fraction of them grow on our used culture agars. Bacterial cells are classified into three categories: the A cells represent cultivable cells, B cells are living though not cultivable whereas the C cells are dead cells. Methods assessing these different cell categories are discussed. Endotoxin is only released from the C-type cells and is removed by the Reverse Osmosis membranes. It is our task to ensurethat we keep the A-cell level low after the Reverse Osmosis. The purified water must not remain very long in the pipe system and the use of Permeate tanks should be avoided.

Bacteria↗
PubMed1998

A mixture theory for charged-hydrated soft tissues containing multi-electrolytes: passive transport and swelling behaviors.

A new mixture theory was developed to model the mechano-electrochemical behaviors of charged-hydrated soft tissues containing multi-electrolytes. The mixture is composed of n + 2 constituents (1 charged solid phase, 1 noncharged solvent phase, and n ion species). Results from this theory show that three types of force are involved in the transport of ions and solvent through such materials: (1) a mechanochemical force (including hydraulic and osmotic pressures); (2) an electrochemical force; and (3) an electrical force. Our results also show that three types of material coefficients are required to characterize the transport rates of these ions and solvent: (1) a hydraulic permeability; (2) mechano-electrochemical coupling coefficients; and (3) an ionic conductance matrix. Specifically, we derived the fundamental governing relationships between these forces and material coefficients to describe such mechano-electrochemical transduction effects as streaming potential, streaming current, diffusion (membrane) potential, electro-osmosis, and anomalous (negative) osmosis. As an example, we showed that the well-known formula for the resting cell membrane potential (Hodgkin and Huxley, 1952a, b) could be derived using our new n + 2 mixture model (a generalized triphasic theory). In general, the n + 2 mixture theory is consistent with and subsumes all previous theories pertaining to specific aspects of charged-hydrated tissues. In addition, our results provided the stress, strain, and fluid velocity fields within a tissue of finite thickness during a one-dimensional steady diffusion process. Numerical results were provided for the exchange of Na+ and Ca++ through the tissue. These numerical results support our hypothesis that tissue fixed charge density (CF) plays a significant role in modulating kinetics of ions and solvent transport through charged-hydrated soft tissues.

Biological Transport↗
PubMed1987

Bacterial colonization and endotoxin content of a new renal dialysis water system composed of acrylonitrile butadiene styrene.

We measured endotoxin and bacterial levels in tap water, in water purified by reverse osmosis, and in dialysate samples over a 4-month period in a new 10-bed renal dialysis unit. Water treated by reverse osmosis is conducted to the 10 stations through 111 m of piping composed of acrylonitrile butadiene styrene (ABS). All determinations were made prior to the opening of the unit and after the system was purged for 35 h with all bedside station taps open. Formaldehyde disinfection of the piping system was attempted with a recommended protocol after 11 weeks by feeding 2.5 liters of 37% formaldehyde (0.85%, vol/vol) into the delivery system. Prior to water purging, 24 ng of endotoxin per ml was detected. This level decreased to 2.0 ng of endotoxin after the purging. Levels of endotoxin remained below 1.0 ng of endotoxin per ml throughout the duration of the study. In contrast, the level of viable microorganisms recovered from the treated water was approximately 3.5 X 10(4) CFU/100 ml. Even after disinfection of the system, there was no significant decrease in culturable bacteria from the water even though endotoxin levels were lower. Species isolated from the renal dialysis system were predominately pseudomonads, whereas species isolated from the tap water were Bacillus and Flavobacterium species. ABS provides a surface suitable for long-term colonization and growth of bacteria. Currently recommended decontamination protocols are ineffective in removing potentially pathogenic bacteria from ABS pipes and thus constitute an increased risk to patients undergoing dialysis.

Acrylic Resins↗
PubMed1995

A rapid, direct method for enumerating respiring enterohemorrhagic Escherichia coli O157:H7 in water.

Simple, rapid methods for the detection and enumeration of specific bacteria in water and wastewater are needed. We have combined incubation using cyanoditolyl tetrazolium chloride (CTC) to detect respiratory activity with a modified fluorescent-antibody (FA) technique, for the enumeration of specific viable bacteria. Bacteria in suspensions were captured by filtration on nonfluorescent polycarbonate membranes that were then incubated on absorbent pads saturated with CTC medium. A specific antibody conjugated with fluorescein isothiocyanate was reacted with the cells on the membrane filter. The membrane filters were mounted for examination by epifluorescence microscopy with optical filters designed to permit concurrent visualization of fluorescent red-orange CTC-formazan crystals in respiring cells which were also stained with the specific FA. Experiments with Escherichia coli O157:H7 indicated that both respiratory activity and specific FA staining could be detected in logarithmic- or stationary-phase cultures, as well as in cells suspended in M9 medium or reverse-osmosis water. Following incubation without added nutrients in M9 medium or unsterile reverse-osmosis water, the E. coli O157:H7 populations increased, although lower proportions of the organisms reduced CTC. Numbers of CTC-positive, FA-positive cells compared with R2A agar plate counts gave a strong linear regression (R = 0.997). Differences in injury did not appear to affect CTC reduction. The procedure, which can be completed within 3 to 4 h, has also been performed successfully with Salmonella typhimurium and Klebsiella pneumoniae.

Culture Media↗
PubMed1991

Comparison of microbiologic assay methods for hemodialysis fluids.

To help prevent pyrogenic reactions and bacteremia in hemodialysis patients, the Association for the Advancement of Medical Instrumentation and the Centers for Disease Control recommend microbiologic assay of hemodialysis fluids at least monthly. Five commercially available assay systems were evaluated by using the membrane filtration technique with standard methods agar and trypticase soy agar as the standards for comparison. Each assay system was challenged with dialysate and reverse-osmosis water from local dialysis centers, aqueous suspensions of eight laboratory strains of gram-negative bacilli and nontuberculous mycobacteria, and a mixed microbial flora inoculated into reverse-osmosis water and laboratory-prepared dialysate. Mean viable counts from triplicate samples were obtained after incubation at 37 degrees C for up to 72 h. The efficiency of recovery varied with the specific type of microbial challenge. The SPC water sampler (Millipore Corp., Bedford, Mass.) was the most consistent in obtaining the highest viable counts. Other commercial systems were comparable to each other in overall performance. All assay systems tested provided an acceptable balance between microbial recovery and required sampling time, equipment, and expertise.

Bacteria↗
PubMed1980

Water balance in the California newt, Taricha torosa.

Both dehydration to 87% of original body weight (Wo) and arginine vasotocin (AVT: 20 mU/g) elicited rapid weight gains (ca. 9% of Wo in the 1st h) when terrestrial-phase T. torosa were given access to water. In each case, net weight gain resulted from increased integumental osmosis and antidiuresis. Mesotocin (0.001 -- 0.1 micrograms/g) elicited modest but significant weight gains (ca. 1%/h) caused solely by increased integumental osmosis. Integumental water uptake from wet moss was 66% that of totally immersed animals. Water movement from ventral to dorsal body surface occurred along channels on the skin. Urinary bladder storage capacities in excess of 50% of Wo were observed. Following AVT administration, bladder water resorption increased significantly, while glomerular filtration rate dropped to 16% of control values. The structural and physiological adaptations for water balance in T. torosa are comparable to those found in some terrestrial anurans.

Animals↗
PubMed1989

Disappearance of aluminic bone disease in a long term asymptomatic dialysis population restricting A1(OH)3 intake: emergence of an idiopathic adynamic bone disease not related to aluminum.

In dialysis centers using reverse osmosis-treated water but not restricting A1(OH)3 administration, a high prevalence of histological aluminum bone disease has been reported. To assess whether this is also the case in our center where A1(OH)3 intake has always been restricted and even completely given up after 1980 thanks to high doses of CaCO3, we reviewed 42 bone biopsies performed between 1975 and 1985 in patients dialyzed for a mean duration of 56 months. Seventeen of these patients had been dialyzed before 1978 with softened water moderately contamined by aluminum, 15 had always been dialyzed with reverse osmosis-treated water and 10 had been exclusively treated by hemofiltration. The prevalence of aluminum bone disease in the whole population was 9.5% (4 patients) and consisted only of adynamic bone disease, osteomalacia being totally absent. When the patients dialyzed with aluminum-contaminated water were excluded as well as 1 diabetic patient who had taken A1(OH)3 for 1.5 years the prevalence of aluminum bone disease was null in this population. When the whole population is considered the prevalence of the other types of bone disease was 76% for osteitis fibrosa and 14.5% for a non-aluminic adynamic bone disease (6 cases). These latter cases differed from the osteitis fibrosa group only by a relative hypoparathyroidism not explained by higher plasma concentrations and higher oral cumulative doses of calcium, magnesium and aluminum or by lower plasma concentrations of phosphate and bicarbonate. None had previous parathyroidectomy, one had an unsuccessful transplantation and one was diabetic. Iron overload was excluded by negative Perls staining.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

[The removability of pesticides during the production of dialysis water (2)].

In many cases it can be demonstrated that the amount of plant protectives and plant treatments (pesticides) in drinking-water exceeds the permitted levels of the drinking-water decree which will be effective on October 1st, 1989. These components are in parts toxicologically important. Therefore, an examination was made on how far pesticides are removed during the conventional purification of dialysis water, but especially during the reverse osmosis. Retention rates of a reverse osmosis plant for 14 different pesticides were discovered which were used in different concentrations and compositions. In part 2 of this contribution the results of the investigation are presented. The figures demonstrate that almost all of the examined components were retained with an effectiveness of 92-98%. The elimination efficiency did not depend on the basic concentration of the pesticides. After an initial phase of 50 h duration, the permeat concentration reached a constant value which did not alter even after more than 700 h.

Dialysis↗
PubMed2003

Icodextrin: a review of its use in peritoneal dialysis.

UNLABELLED: Icodextrin (Extraneal) is a high molecular weight glucose polymer developed specifically for use as an alternative osmotic agent to dextrose during the once-daily long-dwell exchange in peritoneal dialysis (PD). Isosmotic 7.5% icodextrin solution induces transcapillary ultrafiltration (UF) by a mechanism resembling 'colloid' osmosis (unlike hyper-osmolar dextrose-based solutions, which induce UF by crystalline osmosis). In addition, absorption of icodextrin from the peritoneal cavity is relatively slow compared with that of dextrose; this results not only in UF of longer duration, but also a lower carbohydrate load compared with medium (2.5%) and strong (4.25%) dextrose exchanges. In randomised clinical trials of up to 2 years in duration, administration of icodextrin for the long (8- to 16-hour) overnight exchange in continuous ambulatory peritoneal dialysis (CAPD) or daytime exchange in automated peritoneal dialysis (APD) produced net UF which exceeded that with 1.5% and 2.5% dextrose solutions (thereby improving fluid balance), and was equivalent to that with 4.25% dextrose solution. Icodextrin also increased peritoneal clearances of creatinine and urea nitrogen compared with 2.5% dextrose solution. The increase in UF volume with icodextrin was enhanced in CAPD patients with high peritoneal membrane permeability (i.e. high and high-average transporters), maintained in the small number of patients followed-up for 2 years and sustained during episodes of peritonitis. Icodextrin reduced the percentage of patients with net negative UF in contrast to 1.5% and 2.5% dextrose and, in noncomparative studies, extended PD technique survival in patients who had failed dextrose-based dialysis. The use of icodextrin was also associated with some symptomatic improvements and health-related quality of life advantages, and no adverse effect on patient survival, compared with dextrose, although confirmation of these findings is ideally required in appropriately designed studies. The tolerability of icodextrin was generally similar to that of dextrose-based solutions in controlled clinical trials, although there was an approximate three-fold increase in the risk of new skin rash (5.5% vs 1.7%). However, reports of severe cutaneous hypersensitivity reactions remain rare; this possibility should not preclude the use of the polymer. CONCLUSION: 7.5% icodextrin solution offers the first feasible alternative to conventional dextrose solutions for the once-daily long-dwell exchange in PD. It is effective, generally well tolerated and appears to be most useful in situations of reduced or inadequate UF with dextrose, including in high and high-average transporters, during episodes of peritonitis and patients who have failed dextrose-based dialysis.

Clinical Trials as Topic↗
PubMed2006

Major advances in concentrated and dry milk products, cheese, and milk fat-based spreads.

Advances in dairy foods and dairy foods processing since 1981 have influenced consumers and processors of dairy products. Consumer benefits include dairy products with enhanced nutrition and product functionality for specific applications. Processors convert raw milk to finished product with improved efficiencies and have developed processing technologies to improve traditional products and to introduce new products for expanding the dairy foods market. Membrane processing evolved from a laboratory technique to a major industrial process for milk and whey processing. Ultra-filtration and reverse osmosis have been used extensively in fractionation of milk and whey components. Advances in cheese manufacturing methods have included mechanization of the making process. Membrane processing has allowed uniform composition of the cheese milk and starter cultures have become more predictable. Cheese vats have become larger and enclosed as well as computer controlled. Researchers have learned to control many of the functional properties of cheese by understanding the role of fat and calcium distribution, as bound or unbound, in the cheese matrix. Processed cheese (cheese, foods, spreads, and products) maintain their importance in the industry as many product types can be produced to meet market needs and provide stable products for an extended shelf life. Cheese delivers concentrated nutrients of milk and bio-active peptides to consumers. The technologies for the production of concentrated and dried milk and whey products have not changed greatly in the last 25 yr. The size and efficiencies of the equipment have increased. Use of reverse osmosis in place of vacuum condensing has been proposed. Modifying the fatty acid composition of milkfat to alter the nutritional and functional properties of dairy spread has been a focus of research in the last 2 decades. Conjugated linoleic acid, which can be increased in milkfat by alteration of the cow's diet, has been reported to have anticancer, anti-atherogenic, antidiabetic, and antiobesity effects for human health. Separating milk fat into fractions has been accomplished to provide specific fractions to improve butter spreadability, modulate chocolate meltability, and provide texture for low-fat cheeses.

Animals↗
PubMed1998

Water distribution system and diarrheal disease transmission: a case study in Uzbekistan.

Deteriorating water treatment facilities and distribution systems pose a significant public health threat, particularly in republics of the former Soviet Union. Interventions to decrease the disease burden associated with these water systems range from upgrading distribution networks to installing reverse osmosis technology. To provide insight into this decision process, we conducted a randomized intervention study to provide epidemiologic data for water policy decisions in Nukus, Uzbekistan, where drinking water quality is suboptimal. We interviewed residents of 240 households, 120 with and 120 without access to municipal piped water. Residents of 62 households without piped water were trained to chlorinate their drinking water at home in a narrow-necked water container with a spout. All study subjects (1583 individuals) were monitored biweekly for self-reported diarrheal illness over a period of 9.5 weeks. The home chlorination intervention group had the lowest diarrheal rate (28.8/1,000 subjects/month) despite lack of access to piped water in their homes. Compared with the two groups that did not receive the intervention this rate was one-sixth that of the group with no piped water (179.2/1,000 subjects/month) and one-third that of the households with piped water (75.5/1,000 subjects/month). More than 30% of the households with piped water lacked detectable levels of chlorine residues in their drinking water, despite two-stage chlorination of the source water, and were at increased risk of diarrhea. Forty-two percent of these municipal users reported that water pressure had been intermittent within the previous two days. The dramatic reduction in diarrheal rates in the home-chlorination intervention group indicates that a large proportion of diarrheal diseases in Nukus are water-borne. The home-chlorination group had less diarrhea than the group with piped water, implicating the distribution system as a source of disease transmission. Taken together, these epidemiologic data would support the hypothesis that diarrhea in the piped water group could be attributed to cross-contamination between the municipal water supply and sewer, due to leaky pipes and lack of water pressure. Relatively inexpensive steps, including chlorination, maintaining water pressure, and properly maintaining the distribution system, rather than reverse osmosis technology, should reduce diarrheal rates.

Adult↗