Taste Threshold Concentrations of Metals in Drinking Water

Abstract

The U.S. Public Health Service (USPHS) Drinking Water Standards of 1946 are currently being re‐examined in preparation for revision incorporating new knowledge acquired in the subsequent years. In establishing limits on concentrations of certain metals in drinking water, one of the several factors that must be considered is taste threshold. The technical literature is, unfortunately, lacking in such data. The study reported here was undertaken to provide taste threshold data on copper, iron, manganese, and zinc for consideration in the revised standard. The results of the study are summarized in 5 per cent and 50 per cent points on the cumulative frequency distributions of taste threshold concentrations are shown for each metal.

Detection thresholds and taste qualities of iron salts

“…Cohen et al (1960) reported that the most acute tasters were 6400 times as sensitive as the least acute panelists in their taste threshold of ferrous sulfate in drinking water. Thus, the taste of iron compounds might be characterized by a wide range of its detectability.…”

“…Davies (1936) found that iron present in milk in the form of lactate produced a metallic flavor already at a concentration of 15 ppm. As a part of taste threshold concentrations of metals in drinking water, Cohen, Kamphake, Harris, and Woodward (1960) reported that 50% of the panel were able to detect ferrous iron at 3.4 and 1.8 ppm in distilled and spring water respectively. In 1980, Böröcz-Szabó investigated the thresholds of ferrous and ferric salts and the sulfate and chloride anions of these salts in various liquid foods as well as the effect of corrosion products of carbon steel construction materials on sensory properties.…”

Chemical Evaluation of Commercial Bottled Drinking Water from Egypt

“…The detection levels for other zinc salts were somewhat higher. Water containing zinc at concentrations in the range 3}5 mg/L also tends to appear opalescent and develops a greasy "lm when boiled (Cohen, 1960).…”

“…According to Cohen (1960) zinc imparts an undesirable astringent taste to water. Tests indicate that 5% of a population can distinguish between zinc-free water and water containing zinc (as zinc sulphate) at a level of 4 mg/L.…”

“…Staining of laundry and plumbing "xtures occurs when copper concentrations in water exceed 1 mg/L. The taste threshold is above 5 mg/L, although taste is detectable in distilled water at 2.6 mg/L (Cohen, 1960). Natural copper concentrations in drinking water are around a few micrograms per liter (EPA, 1987c).…”