Critical Review and Rethinking of USEPA Secondary Standards for Maintaining Organoleptic Quality of Drinking Water

Abstract

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 The SMCLs for corrosivity and foaming agents may be outdated.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.

Biochemistry and genetics of taste- and odor-producing cyanobacteria

“…Other more diagnostic sensory methods (e.g. Flavor Profile Analysis (FPA) and the Attribute Rating Test (ART)) provide a rapid and economical screening tool that is easily learned and applied but nevertheless can only be used for initial screening and cannot identify the compounds or sources ( Dietrich and Burlingame, 2015).…”

“…Australia, Japan and some districts in the USA are perhaps the most advanced in T&O management, with guidelines for geosmin and 2-MIB at 10 ng/L (NHMRC and NRMMC, 2011;Kishida et al, 2013;Dietrich and Burlingame, 2015). However, long term management of T&O-causing cyanobacteria requires a fundamental understanding of their ecology, and how it varies among taxa, waterbodies and seasons and is influenced by the physics, chemistry and biology of the source waters and drainage basin.…”

“…Watson, 2013;Burgos et al, 2014); nevertheless, they profoundly influence human behavior. Most people judge the safety and acceptability of food and drink by their aesthetics -taste, odor and color, and changes in these aesthetics, particularly if episodic, can elicit widespread public alarm and distrust in potable water supplies and impart major costs to the drinking water industry in treatment and customer relations (Dietrich and Burlingame, 2015;Dunlap et al, 2015). In extreme cases, T&O outbreaks can affect treatment plant operation and cause severe drinking water shortages -as seen, for example, in the 2007 Lake Taihu 'Wuxi crisis' where foul organosulfur-derived odors shut down the water supply to over 2 million residents for five days (Ma et al, 2013).…”

Size and mineral composition of airborne particles generated by an ultrasonic humidifier

“…19,20 Due to anthropogenic activities, TDS of fresh water is currently increasing nationally, indicating there is potential for greater numbers of consumers to have higher TDS tap water. 21,22 Common tap water minerals include calcium, magnesium, bicarbonate/carbonate, chloride, sodium, and sulfate usually at >10 mg/L with typically <1 mg/L of other minerals, which may include aluminum, arsenic, copper, fluoride, lead, iron, manganese, and zinc. 21 Arsenic, copper, and lead have enforceable standards to limit their presence in tap water, while aluminum, chloride, sulfate, iron, manganese, and zinc have nonenforceable esthetic guidelines; therefore, it is important to consider their presence when evaluating inhalation exposures to humidifier aerosols.…”

“…21,22 Common tap water minerals include calcium, magnesium, bicarbonate/carbonate, chloride, sodium, and sulfate usually at >10 mg/L with typically <1 mg/L of other minerals, which may include aluminum, arsenic, copper, fluoride, lead, iron, manganese, and zinc. 21 Arsenic, copper, and lead have enforceable standards to limit their presence in tap water, while aluminum, chloride, sulfate, iron, manganese, and zinc have nonenforceable esthetic guidelines; therefore, it is important to consider their presence when evaluating inhalation exposures to humidifier aerosols. 20,23,24 Additionally, lead, arsenic, copper, and manganese are all recognized as neurotoxins when inhaled, and therefore may represent potential health risk from inhalation of tap water.…”