Regional disparities of microbiological drinking water quality: assessment of spatial pattern and potential sociodemographic determinants

Even in industrialized countries like Germany, drinking water quality is a sensitive issue. Despite a generally high level of drinking water safety, contamination events do occur. We address the question whether demographic change may cause a spatial mismatch between installed capacities at the supply side and actual demand by water users, thereby increasing risks of microbiological contamination. Our investigation is based on a quantitative analysis using the largest publically available data-set on drinking water quality in Germany. We found that the number of reported contamination events in areas affected by population decrease was about twice as high as in areas with a stable or growing population. The relative frequency of microbiological contamination was found to be significantly correlated with rapidly depopulating areas. We conclude that in regions with negative population development, a statistically higher risk of microbiological drinking water contamination may coincide with a greater risk of recontamination during a longer passage in the distribution network.     

Heavy metal contamination of water, soil and produce within riverine communities of the Río Pilcomayo basin, Bolivia

The Río Pilcomayo heads on the Cerro Rico de Potosí precious metal-polymetallic tin deposits of Southern Bolivia. Mining of the Potosí deposits began in 1545 and has led to the severe contamination of the Pilcomayo's water and sediments for at least 200 km downstream of the mines. This investigation addresses the potential human health affects of metal and As contamination on four communities located along the upper Río Pilcomayo by examining the potential significance of human exposure pathways associated with soils, crops and water (including river, irrigation and drinking water supplies). The most significantly contaminated agricultural soils occur upstream at Mondragón where Cd, Pb and Zn concentrations exceed recommended guideline values for agricultural use. Further downstream the degree of contamination decreases, and metal concentrations are below Dutch, German and Canadian guideline values. Metal and As concentrations in agricultural products from the four communities were generally below existing guidelines for heavy metal content in commercially-sold vegetables. Thus, the consumption of contaminated produce does not appear to represent a significant exposure pathway. A possible exception is Pb in carrots, lettuce and beetroots from Sotomayor and Tuero Chico; 37% and 55% of the samples, respectively, exceeded recommended guidelines. Most communities obtain drinking water from sources other than the Río Pilcomayo. In general, dissolved concentrations of metals and As in drinking water from the four studied communities are below the WHO guideline values with the exception of Sb, which was high at Tasapampa. The inadvertent ingestion of contaminated water from irrigation canals and the Río Pilcomayo represents a potential exposure pathway, but its significance is thought to be minimal. Given the degree of soil contamination in the area, perhaps the most significant exposure pathway is the ingestion of contaminated soil particles, particularly particles attached to, and consumed with vegetables. The risks associated with this pathway can be reduced by thoroughly washing or peeling the vegetables prior to consumption. Other exposure pathways that are currently under investigation include the consumption of contaminated meat from livestock and poultry, which drink polluted waters and the ingestion of contaminated wind-blown dust.     

Risk assessment of exposure to volatile organic compounds in groundwater in Taiwan

The purpose of this study is to assess the risks from exposure to 14 volatile organic compounds (VOCs) in selected groundwater sites in Taiwan. The study employs the multimedia environment pollutant assessment system (MEPAS) model to calculate the specific non-cancer and cancer risks at an exposure level of 1 μg/L of each VOC for a variety of exposure pathways. The results show that the highest specific non-cancer risk is associated with water ingestion of vinyl chloride (VC) and that the highest specific cancer risk is associated with indoor breathing of VC. The three most important exposure pathways for risk assessment for both non-cancer and cancer risks are identified as water ingestion, dermal absorption when showering, and indoor breathing. Excess tetrachloroethylene (PCE), trichloroethylene (TCE), dichloroethylene (DCE), and VC are detected in the groundwater aquifers of one dump site and one factory. However, the study suggests that the pollutants in the contaminated groundwater aquifers do not travel extensively with groundwater flow and that the resulting VOC concentrations are below detectable levels for most of the sampled drinking-water treatment plants. Nevertheless, the non-cancer and cancer risks resulting from use of the contaminated groundwater are found to be hundred times higher than the general risk guidance values. To ensure safe groundwater utilisation, remediation initiatives for soil and groundwater are required. Finally, the study suggests that the current criteria for VOCs in drinking water might not be capable of ensuring public safety when groundwater is used as the primary water supply; more stringent quality criteria for drinking water are proposed for selected VOCs.     

The impact of water consumption, point-of-use filtration and exposure categorization on exposure misclassification of ingested drinking water contaminants

The use of population-level indices to estimate individual exposures is an important limitation of previous epidemiologic studies of disinfection by-products (DBPs). We examined exposure misclassification resulting from the use of system average DBP concentrations to estimate individual-level exposures. Data were simulated (n=1000 iterations) for 100 subjects across 10 water systems based on the following assumptions: DBP concentrations ranged from 0-99 microg/L with limited intra-system variability; water intake ranged from 0.5-2.5 L/day; 20% of subjects used bottled water exclusively; 20% of subjects used filtered tap water exclusively; DBP concentrations were reduced by 50% or 90% following filtration. DBP exposure percentiles were used to classify subjects into different exposure levels (e.g., low, intermediate, high and very high) for four classification approaches. Compared to estimates of DBP ingestion that considered daily consumption, source type (i.e., unfiltered tap, filtered tap, and bottled water), and filter efficiency (with 90% DBP removal), 48-62% of subjects were misclassified across one category based on system average concentrations. Average misclassification across at least two exposure categories (e.g., from high to low) ranged from 4-14%. The median classification strategy resulted in the least misclassification, and volume of water intake was the most influential modifier of ingestion exposures. These data illustrate the importance of individual water use information in minimizing exposure misclassification in epidemiologic studies of drinking water contaminants.     

Occurrence, oral exposure and risk assessment of volatile organic compounds in drinking water for Izmir

Concentrations of volatile organic compounds (VOCs) were measured in the drinking water in Province of Izmir, Turkey, and associated health risks due to ingestion of these compounds were investigated using population weighted random samples. A total of 100 houses were visited in different districts of Izmir and drinking water samples were collected from consumers' drinking water source. Questionnaires were administered to one participant in each house to determine demographics and drinking water consumption rates. Oral exposure and risks were estimated for each participant and Izmir population by deterministic and probabilistic approaches, respectively. The four trihalomethane (THM) species (i.e., chloroform, bromodichloromethane, dibromochloromethane, and bromoform), benzene, toluene, p-xylene, and naphthalene were the most frequently detected VOCs with concentrations ranging from below detection limit to 35 microg/l. The risk estimates were found to be less than the values reported in the literature with few exceptions. Noncarcinogenic risks attributable to ingestion of VOCs for Izmir population were negligible, whereas the mean carcinogenic risk estimates for bromodichloromethane and dibromochloromethane were above the de minimis level of one in a million (10(-6)). For all VOCs, the concentrations measured in metropolitan area were greater than those in other districts. All THM species were detected in higher concentrations in tap water, whereas nontap water contained more benzene, toluene, p-xylene, and naphthalene. Therefore, the concentrations of the latter four compounds and associated risks increased with increasing income and education level since bottled water was used in larger proportions within these subgroups. The results of this study showed that oral exposure to drinking water contaminants and associated risks may be higher than the acceptable levels even if the concentrations fall below the standards.     

Effects of time and point-of-use devices on arsenic levels in Southeastern Michigan drinking water, USA

Health effects associated with chronic, low-level exposures to arsenic in drinking water (<100 microg/L) remain unclear, in part due to uncertainties in assessing exposure. Drinking water concentrations have been used to assess past exposure to arsenic in epidemiological studies, under the assumption that a single measurement can be used to estimate historical exposure. This study aims to better understand (1) temporal variability in arsenic concentrations in drinking water and (2) the impact of point-of-use (POU) treatment devices on arsenic exposure measurements, and on reliability of the exposure measurement for population-level studies. Multiple drinking water samples were collected at two points in time (an average of fourteen months apart) for 261 individuals enrolled in a case-control study of arsenic exposure and bladder cancer in Michigan. Sources of drinking water included private wells (n = 221), public water supplies (n = 33), and bottled water (n = 7); mean arsenic concentration was highest in private wells (7.28 microg/L) and lowest in bottled water samples (0.28 microg/L). Arsenic concentrations in primary drinking water samples were highly correlated (r = 0.88, p < 0.0001, n = 196), with 3% of the water sources exceeding the United States Environmental Protection Agency's Maximum Contaminant Level (MCL) in one sample but not in the other sample. Measurement reproducibility did not vary by type of POU device (e.g., softener, filter, reverse osmosis system). Arsenic concentrations did differ, however, between samples treated with POU devices and untreated samples taken on the same day. Substantial differences in arsenic concentrations were consistently observed for reverse osmosis systems; other POU devices had variable effects on arsenic concentrations. These results indicate that while a single residential arsenic measurement may be used to represent exposure in this region, researchers must obtain information on changes in water source and POU treatment devices to better characterize population exposures over time.     

Drinking Water Standards and Risk Assessment

T he role and use of risk assessment methods in the establishment of drinking water standards are described, with emphasis on recent applications in the USA. The process essentially includes an attempt to quantify human exposure from all routes including drinking water, animal toxicology and human epidemiology, when available, to arrive at drinking water concentrations at which exposure would result in 'no known or anticipated adverse effects on health, with a margin of safety'. The process itself is straightforward; however, the application to decision making for substances which are considered to be potentially non-threshold acting in their toxicity (e.g. carcinogenic) requires many policy choices beyond the scientific data, and is subject to considerable controversy.     

Reevaluation of health risk benchmark for sustainable water practice through risk analysis of rooftop-harvested rainwater

Health risk concerns associated with household use of rooftop-harvested rainwater (HRW) constitute one of the main impediments to exploit the benefits of rainwater harvesting in the United States. However, the benchmark based on the U.S. EPA acceptable annual infection risk level of ≤1 case per 10,000 persons per year (≤10⁻⁴ pppy) developed to aid drinking water regulations may be unnecessarily stringent for sustainable water practice. In this study, we challenge the current risk benchmark by quantifying the potential microbial risk associated with consumption of HRW-irrigated home produce and comparing it against the current risk benchmark. Microbial pathogen data for HRW and exposure rates reported in literature are applied to assess the potential microbial risk posed to household consumers of their homegrown produce. A Quantitative Microbial Risk Assessment (QMRA) model based on worst-case scenario (e.g. overhead irrigation, no pathogen inactivation) is applied to three crops that are most popular among home gardeners (lettuce, cucumbers, and tomatoes) and commonly consumed raw. The infection risks of household consumers attributed to consumption of these home produce vary with the type of produce. The lettuce presents the highest risk, which is followed by tomato and cucumber, respectively. Results show that the 95th percentile values of infection risk per intake event of home produce are one to three orders of magnitude (10⁻⁷ to 10⁻⁵) lower than U.S. EPA risk benchmark (≤10⁻⁴ pppy). However, annual infection risks under the same scenario (multiple intake events in a year) are very likely to exceed the risk benchmark by one order of magnitude in some cases. Estimated 95th percentile values of the annual risk are in the 10⁻⁴ to 10⁻³ pppy range, which are still lower than the 10⁻³ to 10⁻¹ pppy risk range of reclaimed water irrigated produce estimated in comparable studies. We further discuss the desirability of HRW for irrigating home produce based on the relative risk of HRW to reclaimed wastewater for irrigation of food crops. The appropriateness of the ≤10⁻⁴ pppy risk benchmark for assessing safety level of HRW-irrigated fresh produce is questioned by considering the assumptions made for the QMRA model. Consequently, the need of an updated approach to assess appropriateness of sustainable water practice for making guidelines and policies is proposed.     

Sources of nitrate and ammonium contamination in groundwater under developing Asian megacities

The status of nitrate (NO(3)(-)), nitrite (NO(2)(-)) and ammonium (NH(4)(+)) contamination in the water systems, and the mechanisms controlling their sources, pathways, and distributions were investigated for the Southeast Asian cities of Metro Manila, Bangkok, and Jakarta. GIS-based monitoring and dual isotope approach (nitrate delta(15)N and delta(18)O) suggested that human waste via severe sewer leakage was the major source of nutrient contaminants in Metro Manila and Jakarta urban areas. Furthermore, the characteristics of the nutrient contamination differed depending on the agricultural land use pattern in the suburban areas: high nitrate contamination was observed in Jakarta (dry fields), and relatively lower nutrients consisting mainly of ammonium were detected in Bangkok (paddy fields). The exponential increase in NO(3)(-)-delta(15)N along with the NO(3)(-) reduction and clear delta(18)O/delta(15)N slopes of NO(3)(-) ( approximately 0.5) indicated the occurrence of denitrification. An anoxic subsurface system associated with the natural geological setting (e.g., the old tidal plain at Bangkok) and artificial pavement coverage served to buffer NO(3)(-) contamination via active denitrification and reduced nitrification. Our results showed that NO(3)(-) and NH(4)(+) contamination of the aquifers in Metro Manila, Bangkok, and Jakarta was not excessive, suggesting low risk of drinking groundwater to human health, at present. However, the increased nitrogen load and increased per capita gross domestic product (GDP) in these developing cities may increase this contamination in the very near future. Continuous monitoring and management of the groundwater system is needed to minimize groundwater pollution in these areas, and this information should be shared among adjacent countries with similar geographic and cultural settings.     

Fluorescence monitoring at a recycled water treatment plant and associated dual distribution system – Implications for cross-connection detection

Dual distribution systems are becoming increasingly common in greenfield housing developments in Australia for the redistribution of recycled water to households for non-potable use. Within such schemes there exists the potential for cross-connections between recycled and drinking water systems. Due to the high level of recycled water treatment, these events are unlikely to lead to outbreaks of illness in the community. Nonetheless, they do represent a breach of the recycled water risk management strategy and therefore an elevated level of risk to consumers. Furthermore, cross-connection events have the potential to undermine public confidence in these types of water recycling. A rapid, highly sensitive method of cross-connection detection may therefore provide an additional level of confidence in these schemes. The aim of this research was to determine the potential for using fluorescence spectroscopy as a monitoring tool in water treatment plants and dual distribution systems. Samples from both the water recycling plant and dual distribution system were collected on a weekly basis over 12 weeks. Fluorescence excitation–emission matrix (EEM) spectra and water quality parameters including dissolved organic carbon, UV₂₅₄, pH, conductivity, free chlorine and turbidity were obtained for each sample. The fluorescence EEM spectra of recycled and drinking water were distinctly different and exhibited low variability throughout the course of the sampling program, indicating a degree of stability of the fluorescent components within the organic matter. A ten-fold difference in mean fluorescence intensity was observed for recycled water compared to drinking water, which was greater than the difference observed for the other measured water quality parameters. Probabilistic analysis was used to determine the reliable detection limit of recycled water contamination of drinking water. Accounting for the inherent variability of both recycled water and drinking water, a 45% contamination of recycled water in drinking water could be detected with a signal-to-noise ratio greater than 3 for more than 95% of individual random sample pairs. Greater sensitivity can be assured by averaging numerous samples. In comparison, a 70% contamination of recycled water in drinking water was required for the same detection using conductivity.     

Organic micropollutants in drinking water: An overview

Biological contamination is still the most significant public health risk from drinking water even in industrialized countries. High potential for organic chemical transport to drinking water continues to exist even with source protection because of the multitude of chemical types and quantities. Drinking water is usually not a unique source nor the most significant contributor to total exposure from synthetic organic chemicals but it might be one of the most controllable.The major public concern with drinking water contamination has been possible contribution to cancer risks from organic micropollutants. Even though the actual risks are probably small in most cases it is clearly within the public interest to prevent adulteration of water supplies and to protect their quality for the future so that these concerns or risks can be avoided.A risk assessment/management decision model is suggested which may assist the process of making rational assessments of these contamination problems and control decisions that consciously consider all of the available data in a consistent manner.     

The correlation of arsenic levels in drinking water with the biological samples of skin disorders

Arsenic (As) poisoning has become a worldwide public health concern. The skin is quite sensitive to As and skin lesions are the most common and earliest nonmalignant effects associated to chronic As exposure. In 2005-2007, a survey was carried out on surface and groundwater arsenic contamination and relationships between As exposure via the drinking water and related adverse health effects (melanosis and keratosis) on villagers resides on the banks of Manchar lake, southern part of Sindh, Pakistan. We screened the population from arsenic-affected villages, 61 to 73% population were identified patients suffering from chronic arsenic toxicity. The effects of As toxicity via drinking water were estimated by biological samples (scalp hair and blood) of adults (males and females), have or have not skin problem (n = 187). The referent samples of both genders were also collected from the areas having low level of As (< 10 μg/L) in drinking water (n = 121). Arsenic concentration in drinking water and biological samples were analyzed using electrothermal atomic absorption spectrometry. The range of arsenic concentrations in lake surface water was 35.2-158 μg/L, which is 3-15 folds higher than World Health Organization [WHO, 2004. Guidelines for drinking-water quality third ed., WHO Geneva Switzerland.]. It was observed that As concentration in the scalp hair and blood samples were above the range of permissible values 0.034-0.319 μg As/g for hair and < 0.5-4.2 μg/L for blood. The linear regressions showed good correlations between arsenic concentrations in water versus hair and blood samples of exposed skin diseased subjects (R² = 0.852 and 0.718) as compared to non-diseased subjects (R² = 0.573 and 0.351), respectively.     

Inelastic stability of liners of cylindrical conduits with local imperfection under external pressure

Liners are typically used to prevent leakage from large-diameter conduits (e.g., sewage pipelines, shafts, tunnels, or penstocks) to their surroundings. The liner is usually designed to resist buckling from external grout pressure during installation or from the external water pressure or internal negative pressure when the conduit is dewatered quickly for inspection and/or maintenance. This study uses the finite element method to investigate the inelastic stability of cylindrical liners with localized wavy imperfections. The liner’s material is assumed to follow elastic-perfectly-plastic stress–strain relationship. The effects of the different geometrical parameters of the liner on its stability are studied. This is in addition to the effect of the liner’s material properties (Young’s modulus, Poisson’s ratio, and yield stress) on its buckling pressure. Results of the study are expected to contribute to the understanding of the mechanical behavior of locally imperfect cylindrical liners when subjected to external uniform pressure, and also in the improvement of the associated design standards.     

Probability of detecting and quantifying faecal contaminations of drinking water by periodically sampling for E. coli: a simulation model study

Drinking water supply companies monitor the presence of Escherichia coli in drinking water to verify the effectiveness of measures that prevent faecal contamination of drinking water. Data are lacking, however, on the sensitivity of the monitoring programmes, as designed under the EU Drinking Water Directive. In this study, the sensitivity of such a monitoring programme was evaluated by hydraulic model simulations of contamination events and calculations of the detection probability of the actual sampling programme of 2002. In the hydraulic model simulations of 16-h periods of 1l h(-1) ingress of untreated domestic sewage, the spread of the contamination through the network and the E. coli concentration dynamics were calculated. The results show that when large parts of the sewage reach reservoirs, e.g. when they originate from the treatment plant or a trunk main, mean detection probabilities are 55-65%. When the contamination does not reach any of the reservoirs, however, the detection probability varies from 0% (when no sampling site is reached) to 13% (when multiple sites are reached). Mean detection probabilities of nine simulated ingress incidents in mains are 5.5% with an SD of 6.5%. In reality, these detection probabilities are probably lower as the study assumed no inactivation or clustering of E. coli, 100% recovery efficiency of the E. coli detection methods and immediate mixing of contaminations in mains and reservoirs. The described method provides a starting point for automated evaluations and optimisations of sampling programmes.     

Effect of pathogen concentrations on removal of Cryptosporidium and Giardia by conventional drinking water treatment

The presence of waterborne enteric pathogens in municipal water supplies contributes risk to public health. To evaluate the removal of these pathogens in drinking water treatment processes, previous researchers have spiked raw waters with up to 10(6) pathogens/L in order to reliably detect the pathogens in treated water. These spike doses are 6-8 orders of magnitude higher than pathogen concentrations routinely observed in practice. In the present study, experiments were conducted with different sampling methods (i.e., grab versus continuous sampling) and initial pathogen concentrations ranging from 10(1) to 10(6) pathogens/L. Results showed that Cryptosporidium oocyst and Giardia cyst removal across conventional treatment were dependent on initial pathogen concentrations, with lower pathogen removals observed when lower initial pathogen spike doses were used. In addition, higher raw water turbidity appeared to result in higher log removal for both Cryptosporidium oocysts and Giardia cysts.     

A relative-risk framework for evaluating transient pathogen intrusion in distribution systems

Hydraulic transients generate significant negative pressures in water systems that may cause intrusion of contaminated water from the environment into the pipe. This paper expands the consideration of transient intrusion events from their purely hydraulic aspects by developing a risk-based framework for comparing the relative risk-reduction achieved by alternative transient-intrusion mitigation strategies. Alternative strategies may be any combination of changes to system operation or surge controls that would reduce the potential for intrusion of contaminants from the soil-groundwater environment surrounding the pipe. A reference groundwater contamination is assumed, and intrusion volumes and time-varying pathogen concentrations are computed respectively using hydraulic transient and water quality models. Risk-based measures are proposed to provide quantitative assessments of the relative reduction in the risk of receptor infection achieved by alternative mitigation strategies.     

Perfluorooctane sulphonate in raw and drinking water sources in the United Kingdom

There has been increasing interest in the widely used perfluorinated chemicals such as perfluorooctane sulphonate (PFOS). PFOS has been shown to be toxic, persistent and bioaccumulative in the environment and is a focus for restriction within the European Union. Limited monitoring data, especially in the United Kingdom, are available for PFOS in environmental waters, and even less for its detection in drinking water. Data available in the United Kingdom indicate that PFOS contamination of environmental waters has only occurred following specific incidents. Monitoring of 20 raw and treated drinking water sites in England, covering four seasonal periods, showed that PFOS is not a widespread background contaminant of raw and treated drinking water in England. Low levels of PFOS (0.012–0.208 μg/L) were detected at four specific sites, which were at a higher risk for contamination. At three of these sites, where PFOS was detected in both raw and final drinking water, treatment processes [chlorination, ozonation and granular activated carbon (GAC)] did not appear to remove PFOS. The findings of this work are pertinent to risk assessments now required by the drinking water quality regulations.     

Microbiological risk assessment and management of shallow groundwater sources in Lichinga, Mozambique

The principal water target of the Millennium Development Goals (MDG) is to ensure environmental sustainability by halving the proportion of people without access to safe water by 2015. Although great strides have been made in meeting this challenge since the year 2000, the safety of many of these water supplies remains unknown. Acknowledging the weaknesses of current water quality and hydrogeological means of assuring microbial safety, this paper has the objective of developing improved methods for the assessment and management of microbiological water safety based on a ‘risk’ paradigm. This paper provides evidence for the risk assessment of both conventional aquifer pathways and localised (short circuiting) pathways to 25 wells of three well technology types in Mozambique between 2002 and 2005. 1 Findings from the research outline improve methods of risk assessment and management by demonstrating that (1) the predominant source of contamination was from animal faeces rather than from latrines/septic tanks, (2) short circuiting is a significant risk to shallow groundwater in developing countries, (3) the use of alternative indicator organisms (e.g. enterococci) may improve risk understanding and (4) the World Health Organisation Water Safety Plans are recommended as an appropriate method of risk management.     

Arsenic-contaminated cold-spring water in mountainous areas of Hui County, Northwest China: a new source of arsenic exposure

Although pump-well is the primary drinking water source in rural areas of China, there are still 8.4% of villages reliant on cold-spring. In this study, a survey of arsenic concentration in cold-springs and pump-wells was carried out in Hui County, Northwest China. A total of 352 drinking water samples, including 177 cold-springs and 175 pump-wells, were collected. The maximum arsenic concentrations in cold-springs and pump-wells were 0.482 mg/L and 0.067 mg/L, respectively. We found that 15.8% (28) of total cold-springs and 1.1% (2) of total pump-wells had arsenic concentrations exceeding the maximum allowable concentration of arsenic in drinking water of rural China (0.05 mg/L). Our findings show that 5 cold spring-contaminated villages are located in the mountainous areas of Hui County and 2224 inhabitants may be at risk of high arsenic exposure. This paper indicates that arsenic contamination of cold-springs may be more serious than expected in mountainous areas of Northwest China and extensive surveys and epidemiological studies should be carried out to investigate the potential contaminated areas and affected population.     

Models for predicting disinfection byproduct (DBP) formation in drinking waters: A chronological review

Disinfection for the supply of safe drinking water forms a variety of known and unknown byproducts through reactions between the disinfectants and natural organic matter. Chronic exposure to disinfection byproducts through the ingestion of drinking water, inhalation and dermal contact during regular indoor activities (e.g., showering, bathing, cooking) may pose cancer and non-cancer risks to human health. Since their discovery in drinking water in 1974, numerous studies have presented models to predict DBP formation in drinking water. To date, more than 48 scientific publications have reported 118 models to predict DBP formation in drinking waters. These models were developed through laboratory and field-scale experiments using raw, pretreated and synthetic waters. This paper aims to review DBP predictive models, analyze the model variables, assess the model advantages and limitations, and to determine their applicability to different water supply systems. The paper identifies the current challenges and future research needs to better control DBP formation. Finally, important directions for future research are recommended to protect human health and to follow the best management practices.