Systematic tracking, visualizing, and interpreting of consumer feedback for drinking water quality

Solvent-like bis (2-chloro-1-methylethyl) ether occurrence in drinking water: Multidimensional risk assessment integrated health and aesthetic aspects

Bis (2-chloro-1-methylethyl) ether (DCIP), one U.S. Environmental Protection Agency priority pollutant, could pose health and/or odor risk in water environment. In this study, odor characteristics, occurrence and source of DCIP in drinking waters of China were investigated based on sensory analysis and a nation-wide investigation covering 140 drinking water treatment plants. Then multi-risk integrated health and aesthetic aspects through oral and inhalation (showering) exposure by drinking water were first estimated. Sensory evaluation showed DCIP exhibited "solvent-like" odor with thresholds of 34.8 ng/L in air and 142.0 ng/L in water. DCIP was detected at comparable concentrations in raw and finished waters (<1280 ng/L) and was by-product from industrial production of epichlorohydrin/propylene oxide. Lifetime Average Daily Dose through oral exposure was 0-36.65 ng/day/kg, corresponding to odor activity values of 0-8.4 and hazard quotients of far < 1, indicating drinking tap water might cause odor issues rather than significant health hazard. The proportion of sensitive population to DCIP's odor was 6.1%. In contrast, residents rarely detect DCIP's odor by inhalation. The presence in drinking water as industrial by-product, poor removal using conventional water treatment and potential to be T&O issues, indicates urgent demand for pollutant source control to protect DCIP from entering source waters.

Management of biogenic taste and odour: From source water, through treatment processes and distribution systems, to consumers

Biogenic taste and odour (T&O) have become a global concern for water utilities, due to the increasing frequency of algal blooms and other microbial events arising from the combined effects of climate change and eutrophication. Microbially-produced T&O compounds impact source waters, drinking water treatment plants, and drinking water distribution systems. It is important to manage across the entire biogenic T&O pathway to identify key risk factors and devise strategies that will safeguard the quality of drinking water in a changing world, since the presence of T&O impacts consumer confidence in drinking water safety. This study provides a critical review of current knowledge on T&O-causing microbes and compounds for proactive management, including the identification of abiotic risk factors in source waters, a discussion on the effectiveness of existing T&O barriers in drinking water treatment plants, an analysis of risk factors for biofilm growth in water distribution systems, and an assessment of the impacts of T&O on consumers. The fate of biogenic T&O in drinking water systems is tracked from microbial production pathways, through the release of intracellular T&O by cell lysis, to the treatment of microbial cells and dissolved T&O. Based on current knowledge, five impactful research and management directions across the T&O pathway are recommended.

Tap Water Quality and Habits of Its Use: A Comparative Analysis in Poland and Ukraine

Water, as one of the main media of human existence on earth, is the basis of the functioning of most societies. This article discusses various activities related to water resource management and analyzes the evaluation of selected quality parameters of tap water in Poland and Ukraine. The aim of the manuscript was to compare opinions on tap water quality and habits of its use in Poland and Ukraine, taking into account different seasons of the year as periods of use of supplied water. The hypothesis of the study was that tap water parameters are evaluated differently in Poland and Ukraine at different times of water supply. Due to the complexity of research aspects, a mixed-methods research procedure was used, in which a literature review was combined with a survey and statistical analysis. For the purpose of the survey, the authors’ questionnaire “Survey of customers’ opinions on selected parameters of tap water supplied in Poland and Ukraine” was created. The results of the research confirmed the hypothesis and allowed for the development a model for the evaluation of parameters of tap water supplied on the territory of Poland and Ukraine and to get to know the expectations of customers of these countries. The presented model provides practical indications that can be used to optimize water supply and meet customers’ expectations, including improvement of water quality parameters.

Implications for emergency response to the severe odor incident occurred in source water: Potential odorants and control strategy

Sudden odor incidents occurring in the source water have been a severe problem for water suppliers. In order to apply emergency control measures effectively, it is necessary to identify the target compounds responsible for odor incidents rapidly. The present work identified the odorants and explored emergency disposal mechanisms for sudden and severe odors in the QT River's drinking water source (HZ city, China). Medicinal, chemical, septic, and musty odors with strong intensities were detected in the source water. The effect of conventional treatments of drinking water treatment plant (DWTP) on odors' removal was limited, which was evident by the presence of medicinal, chemical, and musty odors with moderate intensities in the effluent of DWTP. Total seventeen odorants were identified successfully in the source water of QT River and the effluent of DWTP. The measured OAVs and reconstituting the identified odorants explained 87, 87, 89, and 94% of medicinal, chemical, septic, and musty odors, respectively, in the source water of the QT River and 90, 87, and 88% of medicinal, chemical, and musty odors in the effluent. Styrene, phenol, 2-chlorophenol, 2-tert-butylphenol, and 2-methylphenol were associated with the medicinal odor, while propyl sulfide, diethyl disulfide, propyl disulfide, and indole were related to the septic odor. Geosmin and 2-methylisoborneol (2-MIB) were responsible for the musty odor, and cyclohexanone, 1,4-dichlorobenzene, and nitrobenzene were involved with the chemical odor. Based on the characteristics of identified odorants, powdered activated carbon (PAC) was applied to control the odors in the QT River. The results indicated that the medicinal, chemical, septic, and musty odors could be removed entirely after adding 15 mg/L PAC, which effectively controlled emergency odor problems. Overall, the study would offer a scientific basis and operational reference for emergency odor management and control in DWTP with similar complicated odor incidents.

The formation, analysis, and control of chlor(am)ination-derived odor problems: A review

Odors and tastes have become universal problems related to drinking water quality. In addition to the typical odor problems caused by algae or microorganisms, the occurrence of odors derived from drinking water disinfection have attracted attention. The chlor(am)ination-derived odor substances have certain toxicity and odor-causing characteristics, and would enter the tap water through water distribution systems, directly affecting drinking water safety and customer experience. This study provided a comprehensive overview of the occurrence, detection, and control of odor substances derived from drinking water chlor(am)ination disinfection. The occurrence and formation mechanisms of several typical types of disinfection derived odor substances were summarized, including haloanisoles, N-chloroaldimines, iodotrihalomethanes, and halophenoles. They are mainly derived from specific precursors such as halophenols, anisoles, and amino acids species during the disinfection or distribution networks. In addition, the change of disinfectant during chlor(am)ination was also one of the causes of disinfection odors. Due to the extremely low odor threshold concentrations (OTCs) of these odor substances, the effective sample pre-enrichment for instrument identification and quantification are essential. The control strategies of odor problems mainly include adsorption, chemical oxidation, and combined processes such as ozonation and biological activated carbon processes (O₃/BAC) and ultraviolet-based advanced oxidation processes (UV-AOPs). Finally, the challenges and possible future research directions in this research field were discussed and proposed.

A critical review on geosmin and 2-methylisoborneol in water: sources, effects, detection, and removal techniques

The exposure to geosmin (GSM) and 2-methylisoborneol (2-MIB) in water has caused a negative impact on product reputation and customer distrust. The occurrence of these compounds and their metabolites during drinking water treatment processes has caused different health challenges. Conventional treatment techniques such as coagulation, sedimentation, filtration, and chlorination employed in removing these two commonest taste and odor compounds (GSM and 2-MIB) were found to be ineffective and inherent shortcomings. The removal of GSM and MIB were found to be effective using combination of activated carbon and ozonation; however, high treatment cost associated with ozonation technique and poor regeneration efficiency of activated carbon constitute serious setback to the combined system. Other shortcoming of the activated carbon adsorption and ozonation include low adsorption efficiency due to the presence of natural organic matter and humic acid. In light of this background, the review is focused on the sources, effects, environmental pathways, detection, and removal techniques of 2-MIB and GSM from aqueous media. Although advanced oxidation processes (AOPs) were found to be promising to remove the two compounds from water but accompanied with different challenges. Herein, to fill the knowledge gap analysis on these algal metabolites (GSM and 2-MIB), the integration of treatment processes vis-a-viz combination of one or more AOPs with other conventional methods are considered logical to remove these odorous compounds and hence could improve overall water quality.

Check-if-apply approach for consumers and utilities to communicate about drinking water aesthetics quality

Globally, consumers judge their drinking water through its aesthetic qualities because tastes, odors, and appearances are readily detectable by untrained consumers. Consumer feedback is critical to the water industry for efficient resolution of aesthetic water quality issues, although consumer descriptions of taste and odor issues can sometimes be unfocused or confusing. A user-friendly approach can facilitate consumer communications to utilities in the challenging task of describing drinking water taste and odor issues. The purpose of this study was to develop a list of taste and odor descriptors and test a novel "check-if-apply" approach to describe drinking water quality. The final list contained 28 individual and/or groups of descriptors. 75 participants tested water samples impacted by various tastants or odorants: duplicate samples of chloraminated tap water, tap water with heptanal, tap water with 2-methylisoborneol (MIB), tap water with NaCl, bottled water, and bottled water with CuSO₄. Participants used a 9-point hedonic scale (1 = 'dislike extremely'; 9 = 'like extremely') to rate overall liking of each sample, and they used the check-if-apply list to describe the taste or odor. Participants also answered a brief questionnaire and used a 5-point scale (1 = 'very difficult'; 5 = 'very easy') to evaluate their experience using the check-if-apply list. Significant differences were observed in acceptability and sensory profile of samples (p-value <0.05). Tap water with MIB had the lowest acceptability mean score (3.43 ± 1.74), while flavorless bottled water had the highest acceptability mean score (6.23 ± 1.47). 'Salty', 'metallic', 'chemical' and 'musty/earthy' were the dominant descriptors for NaCl, CuSO_4, heptanal, and MIB, respectively. Most participants (81%) found the check-if-apply list as 'somewhat easy' to 'very easy' to use (mean = 3.44 ± 1.07) and suggested it as a user-friendly lexicon for consumers and utilities to communicate about water quality.

Pyrazines: A diverse class of earthy-musty odorants impacting drinking water quality and consumer satisfaction

The presence of earthy-musty odors in drinking water is a major concern for water suppliers and consumers worldwide. While geosmin and 2-methylisoborneol are the most studied earthy-musty odor-causing compounds, pyrazine and its alkyl and methoxy compounds possess similar odors and are widely distributed in nature, foods, and beverages. In this study, odor characteristics of pyrazines and their presence in natural and treated waters were determined. Pyrazine, 2,6-dimethyl-pyrazine (DMP), 2,3,5-trimethyl-pyrazine (TrMP), 2-ethyl-5(6)-methyl-pyrazine (EMP), 2,3,5,6-tetramethyl-pyrazine (TeMP), 2-isobutyl-3-methoxy-pyrazine (IBMP) and 2-isopropyl-3-methoxy-pyrazine (IPMP) were measured in source and finished drinking water across China. 2-Methoxy-3,5-dimethyl-pyrazine (MDMP), IBMP, and IPMP were investigated in rivers in Virginia, USA. The results showed that "musty" and "sweet" were the most common descriptors for pyrazine, DMP, MDMP, TrMP, and TeMP. While IBMP and IPMP were never detected in 140 source or drinking water samples from across China, pyrazine, DMP, MDMP, TrMP, and TeMP occurred throughout with concentrations of n.d.-62.2 ng/L-aq in source water and n.d.-39.6 ng/L-aq in finished water. IBMP, IPMP, and MDMP were present in two Virginia rivers; MDMP occurred in 18% of the samples with concentrations of n.d.-4.4 ng/L, many of which were above the aqueous odor threshold of 0.043 ng/L MDMP. The removal efficiencies through conventional water treatment were poor, ranging from negative removals to ∼10%. Advanced oxidation water treatment could only remove EMP and TrMP. The widespread presence of earthy-musty-sweet pyrazines in source and drinking waters on two continents, their poor removal during water treatment, and ng/L odor threshold concentrations confirm their potential to be T&O issues for consumers.

A review: The challenge, consensus, and confusion of describing odors and tastes in drinking water

Documentation exists for many chemicals that cause tastes and odors in water, however, water suppliers do not routinely monitor for these chemicals. Effective management of a taste-and-odor (T&O) problem in drinking water often requires good verbal description of the offending sensory experience. Experience demonstrates that obtaining verbal descriptions is challenging. To improve our understanding of communications, sensory science literature was reviewed to obtain descriptors for twenty-one chemicals acknowledged to cause T&O issues in drinking water. The review focused on pure chemicals above their odor threshold concentrations. Results reveal that descriptors follow four general categories. For select chemicals, strong consensus exists around a single or very few appropriate descriptors. Examples are "salty" for sodium and "chlorinous" for free chlorine. The next category has moderate agreement for several descriptors, with at least one major descriptor. For example the microbiological metabolite 2-methylisoborneol is most commonly described as "earthy/musty/moldy" but also "camphor, grass, and sweet". Some chemicals have weak agreement on their descriptors, but overall associate words with similar meaning. An example is the chemical toluene with descriptors of "solvent-like" words including "solvent", "gasoline", "paint-like", "cleaning fluid", and "etherish", but also "vinegar" and "sweet". The last chemical category possesses diverse descriptors with no consensus. For example, the oxylipin n-heptanal is described as "oily, fatty, chemical, musty/earthy/moldy, rancid, sweaty, grass, sickening, and stale". While descriptor diversity for select chemicals may not identify the cause of T&O, understanding that certain chemicals are perceived very differently aids in effective communications and eliminates confusion from expecting consumers or utility personnel to respond with consensus.

Identification of odorant characters using GC-MS/O in biosolids emissions from aerobic and anaerobic stabilisation

Malodorous emissions from biosolids limit potential re-use opportunities. Emissions from anaerobically stabilised biosolids have been widely studied. In contrast, emissions from aerobically stabilised biosolids have not been well documented. Individual odorants in complex emissions can be detected using sensorial analysis methods, such as gas chromatography mass spectroscopy coupled with an odour detection port (GC-MS/O) where assessors sniff the GC effluent to identify odorants present. In this study, GC-MS/O was used to study and compare emissions from biosolids produced from aerobically and anaerobically stabilised biosolids from different wastewater treatment plants (WWTPs). The WWTPs varied in size, catchments and dewatering technology. Three GC-MS/O assessors were used for the sensorial analysis. The identified odorants varied significantly between the two sites using aerobic stabilisation, in number of odour characters detected, as well as their intensity. Different odour characters were noted from biosolids generated at the aerobic digestion sites compared to characters from biosolids generated at the anaerobic digestion site. Biosolids from the aerobic digestion sites had medicinal, acrid or putrid type odours not noted from the anaerobic site. However, descriptors of biosolids emissions were commonly noted as: rotten vegetables, seaweed, garbage, garlic, or bad-breath. Many of the descriptors were associated with the presence of sulfur-type compounds. The importance of assessor variability was also highlighted in the paper where certain characters were not detected or were described differently by assessors.

Sensory politics: The tug-of-war between potability and palatability in municipal water production

Sensory information signaled the acceptability of water for consumption for lay and professional people into the early twentieth century. Yet as the twentieth century progressed, professional efforts to standardize water-testing methods have increasingly excluded aesthetic information, preferring to rely on the objectivity of analytic information. Despite some highly publicized exceptions, consumer complaints remain peripheral to the making and regulating of drinking water. This exclusion is often attributed to the unreliability of the human senses in detecting danger. However, technical discussions among water professionals during the twentieth century suggest that this exclusion is actually due to sensory politics, the institutional and regulatory practices of inclusion or exclusion of sensory knowledge from systems of action. Water workers developed and turned to standardized analytical methods for detecting chemical and microbiological contaminants, and more recently sensory contaminants, a process that attempted to mitigate the unevenness of human sensing. In so doing, they created regimes of perception that categorized consumer sensory knowledge as aesthetic. By siloing consumers' sensory knowledge about water quality into the realm of the aesthetic instead of accommodating it in the analytic, the regimes of perception implemented during the twentieth century to preserve health have marginalized subjective experiences. Discounting the human experience with municipal water as irrelevant to its quality, control and regulation is out of touch with its intended use as an ingestible, and calls for new practices that engage consumers as valuable participants.

Effects of inequality of supply hours on consumers' coping strategies and perceptions of intermittent water supply in Kathmandu Valley, Nepal

To investigate the effects of unequal supply hours on consumers' coping strategies and perceptions of the intermittent water supply (IWS) in the Kathmandu Valley (KV), Nepal we conducted a randomized household survey (n=369) and on-site water quality tests. Half of the households received piped water for 6 or fewer hours per week. To augment or cope with the inadequate supply, 28% of the households used highly contaminated and expensive tanker-delivered water. Half of the piped water samples (n=13) were contaminated with Escherichia coli. Free chlorine concentration in all piped water samples was below the national standards (0.1-0.2mg/L), but combined chlorine was detected at an average of 0.24mg/L, indicating ingression of contaminants in the network. Point-of-use devices could increase access to safe water in the KV from 42% to 80%. The use of Lorenz curves and Gini coefficients revealed inequality of piped water supply hours per week both between and within service areas in the KV, due mainly to a small percentage of households who receive longer supply hours. To cope with reduced supply hours, home owners pay more to get water from alternative sources, while tenants compromise their water consumption. Under IWS, expectations for improvements in piped water quality and supply regularity are higher than those for supply volume. Consumers' perceptions of the piped water services worsen with the reduction in supply hours, but perceptions of piped water tariff are independent of supply hours.

Identification and characterization of phenylacetonitrile as a nitrogenous disinfection byproduct derived from chlorination of phenylalanine in drinking water

Unregulated disinfection byproducts (DBPs), including nitrogenous disinfection byproducts (N-DBPs), originating from chlorination of the precursor amino acid phenylalanine in aqueous systems, were identified in laboratory reactions and distributed tap. The major N-DBP identified was phenylacetonitrile, and minor DBPs of benzyl chloride, phenylacetaldehyde, 2-chlorobenzyl cyanide, and 2, 6-diphenylpyridine were also formed. Phenylacetonitrile was generated through decarboxylation, dechlorination and/or hydrolysis processes. With an aromatic structure, phenylacetonitrile has an unpleasant odor of various descriptors and an odor threshold concentration of 0.2 ppt-v as measured through gas chromatography-olfactometry. The half-life of phenylacetonitrile in reagent water and chlorinated water at 19 °C were 121 h and 792 h, respectively. The occurrence of phenylacetonitrile as an N-DBP in tap water was investigated for the first time; the results revealed that μg/L concentrations were present in nine different distributed drinking waters in China and the United States. Phenylacetonitrile deteriorates the aesthetic quality of drinking water and may present risk due to its prolonged existence in drinking water, especially in the presence of residual chlorine.

Enabling Science Support for Better Decision-Making when Responding to Chemical Spills

Chemical spills and accidents contaminate the environment and disrupt societies and economies around the globe. In the United States there were approximately 172,000 chemical spills that affected US waterbodies from 2004 to 2014. More than 8000 of these spills involved non-petroleum-related chemicals. Traditional emergency responses or incident command structures (ICSs) that respond to chemical spills require coordinated efforts by predominantly government personnel from multiple disciplines, including disaster management, public health, and environmental protection. However, the requirements of emergency response teams for science support might not be met within the traditional ICS. We describe the US ICS as an example of emergency-response approaches to chemical spills and provide examples in which external scientific support from research personnel benefitted the ICS emergency response, focusing primarily on nonpetroleum chemical spills. We then propose immediate, near-term, and long-term activities to support the response to chemical spills, focusing on nonpetroleum chemical spills. Further, we call for science support for spill prevention and near-term spill-incident response and identify longer-term research needs. The development of a formal mechanism for external science support of ICS from governmental and nongovernmental scientists would benefit rapid responders, advance incident- and crisis-response science, and aid society in coping with and recovering from chemical spills.

The occurrence of haloanisoles as an emerging odorant in municipal tap water of typical cities in China

In this study, occurrence of the haloanisoles odorous compounds in tap water of Chinese cities, were investigated by solid-phase microextraction (SPME)-GC/MS analysis. This study revealed the occurrence of four kinds of haloanisoles in 22 cities of China in both summer and winter. Except 2,4,6-tribromoanisole (2,4,6-TBA), all studied haloanisoles showed higher frequency of detection. 2,3,6-Trichloroanisole (2,3,6-TCA) and 2,3,4-trichloroanisole (2,3,4-TCA) showed higher occurrence concentration; however, the relative odor values of them was lower. These values of 2,4,6-TBA and 2,4,6-trichloroanisole (2,4,6-TCA) in all samples were greater than zero in both summer and winter, indicating the odor from haloanisoles could be felt by human noise. This study further showed that Beijing exhibited most serious occurrence of haloanisoles that were depended on the season and drinking water distribution system (country and city). From this study, it was confirmed that haloanisoles was important taste and odor compounds in tap water of China. Based on the survey of occurrence of halophenol and residual chlorine, the possible source for the formation of haloanisoles in tap water was discussed. Furthermore, several suggestions on control the haloanisoles odor in drinking water treatment plant and water distribution system were provided.

Subtleties of human exposure and response to chemical mixtures from spills

Worldwide, chemical spills degrade drinking water quality and threaten human health through ingestion and inhalation. Spills are often mixtures of chemicals; thus, understanding the interaction of chemical and biological properties of the major and minor components is critical to assessing human exposure. The crude (4-methylcyclohexyl)methanol (MCHM) spill provides an opportunity to assess such subtleties. This research determined the relative amounts, volatilization, and biological odor properties of minor components cis- and trans-methyl-4-methylcyclohexanecarboxylate (MMCHC) isomers and major components cis- and trans-4-MCHM, then compared properties and human exposure differences among them. (1)H nuclear magnetic resonance and chromatography revealed that the minor MMCHC isomers were about 1% of the major MCHM isomers. At typical showering temperature of 40 °C, Henry's law constants were 1.50 × 10(-2) and 2.23 × 10(-2) for cis- and trans-MMCHC, respectively, which is 20-50 fold higher than for 4-MCHM isomers. The odor thresholds were 1.83 and 0.02 ppb-v air for cis- and trans-MMCHC, which were both described as predominantly sweet. These data are compared to the higher 120 ppb-v air and 0.06 ppb-v odor thresholds for cis- and trans-4-MCHM, for which the trans-isomer had a dominant licorice descriptor. Application of a shower model demonstrated that while MMCHC isomers are only about 1% of the MCHM isomers, during showering, the MMCHC isomers are 13.8% by volume (16.3% by mass) because of their higher volatility. Trans-4-MCHM contributed about 82% of the odor because of higher volatility and lower odor threshold, trans-MMCHC, which represents 0.3% of the mass, contributed 18% of the odor. This study, with its unique human sensory component to assess exposure, reaffirmed that hazard assessment must not be based solely on relative concentration, but also consider the chemical fate, transport, and biological properties to determine the actual levels of exposure across different media.

Assessing clarity of message communication for mandated USEPA drinking water quality reports

The United States Environmental Protection Agency mandates that community water systems (CWSs), or drinking water utilities, provide annual consumer confidence reports (CCRs) reporting on water quality, compliance with regulations, source water, and consumer education. While certain report formats are prescribed, there are no criteria ensuring that consumers understand messages in these reports. To assess clarity of message, trained raters evaluated a national sample of 30 CCRs using the Centers for Disease Control Clear Communication Index (Index) indices: (1) Main Message/Call to Action; (2) Language; (3) Information Design; (4) State of the Science; (5) Behavioral Recommendations; (6) Numbers; and (7) Risk. Communication materials are considered qualifying if they achieve a 90% Index score. Overall mean score across CCRs was 50 ± 14% and none scored 90% or higher. CCRs did not differ significantly by water system size. State of the Science (3 ± 15%) and Behavioral Recommendations (77 ± 36%) indices were the lowest and highest, respectively. Only 63% of CCRs explicitly stated if the water was safe to drink according to federal and state standards and regulations. None of the CCRs had passing Index scores, signaling that CWSs are not effectively communicating with their consumers; thus, the Index can serve as an evaluation tool for CCR effectiveness and a guide to improve water quality communications.

Tale of two isomers: complexities of human odor perception for cis- and trans-4-methylcyclohexane methanol from the chemical spill in West Virginia

Application of gas chromatography with mass spectrometric and human olfactory "sniffer" detectors reveals the nature of odorous chemicals from an industrial chemical spill. Crude 4-methylcyclohexane methanol (4-MCHM) spilled in a river and then contaminated drinking water and air for over 300000 consumers living in West Virginia. Olfactory gas chromatography allows investigators to independently measure the odor of chemical components in a mixture. Crude 4-MCHM is comprised of several major cyclohexane components, four of which have distinct isomer pairs. The cis- and trans-4-MCHM isomers are the only components to have distinct odors at the concentrations used in this study. The trans-4-MCHM is the dominant odorant with descriptors of "licorice" and "sweet". Trans-4-MCHM has an air odor threshold concentration of 0.060 ppb-v (95% CI: 0.040-0.091). The odor threshold concentrations are not influenced by gender or age but are lower by a factor of 5 for individuals with prior exposure compared to naïve subjects. Individual trans-4-MCHM odor threshold concentrations vary by more than a factor of 100. The cis-4-MCHM isomer has approximately a 2000-fold higher odor threshold concentration, different descriptors, and an even wider individual response range.

Critical review and rethinking of USEPA secondary standards for maintaining organoleptic quality of drinking water

Consumers assess their tap water primarily by its taste, odor, and appearance. Starting in 1979, USEPA promulgated Secondary Maximum Contaminant Levels (SMCLs) as guidance for contaminants with organoleptic effects and also to maintain consumers’ confidence in tap water. This review assesses the basis for the 15 SMCLs (aluminum, chloride, color, copper, corrosivity, fluoride, foaming agents, iron, manganese, odor, pH, silver, sulfate, total dissolved solids, zinc) and summarizes advances in scientific knowledge since their promulgation. SMCLs for aluminum, color, pH, silver, sulfate, total dissolved solids, and zinc are appropriate at current values and remain consistent with sensory science literature. Recent advances in sensory and health sciences indicate that SMCLs for chloride, copper, fluoride, iron, and manganese are too high to minimize organoleptic effects. The SMCLs for corrosivity and foaming agents may be outdated. The SMCL for odor requires rethinking as the test does not correlate with consumer complaints. Since current stresses on source and treated waters include chemical spills, algal blooms, and increased salinization, organoleptic episodes that negatively impact consumer confidence and perception of tap water still occur and may increase. Thus, adherence to SMCLs can help maintain production of palatable water along with consumers’ confidence in their water providers.