This study describes the size distribution and concentration of particles expelled by a portable, 3-L ultrasonic humidifier. The ultrasonic humidifier was filled with waters of varying mineral content and hardness. Aerosol size distributions were measured during 8 hours of humidifier operation in a typical bedroom. Humidifiers produced approximately 1.22 × 10 10 -2.50 × 10 10 airborne particles per milliliter of water consumed, resulting in airborne particle concentrations of 3.01-5.91 × 10 4 #/cm 3 , with modes ranging between 109 and 322 nm in diameter. The emission rate of particles varied by water type from 1.02 × 10 9 to 2.27 × 10 9 #/s. Lower mineral waters produced fewer, smaller particles when compared to higher mineral waters. Chemical analyses of particles collected with a cascade impactor indicated that the minerals in emitted particles had the same relative mineral concentrations as the fill water. Our results demonstrate that ultrasonic humidifiers should be considered a source of inhalation exposure to minerals dissolved in water, and that the magnitude of exposure to inhalable particles will vary with water quality. K E Y W O R D Sair quality, air-water interface, humidifier, inhalation exposure, PM2.5, water quality While humidifiers offer increased comfort and improved wellbeing by raising humidity indoors, they may also introduce contaminants to indoor air. This is less of a concern with evaporative humidifiers, which release only water and highly volatile compounds into air, but is a possibility with ultrasonic humidifiers, as they create tiny droplets consisting of water and its impurities. Once the water evaporates, the impurities can remain suspended as airborne particles. | INTRODUCTIONOne of the primary concerns for household humidifiers is their ability to aerosolize pathogenic microbes. 7,8 There is limited information about a humidifier's ability to aerosolize specific minerals, though it is acknowledged that use of waters containing minerals may result in expulsion of "white dust." 1,9,10 This "white dust" was associated with respiratory distress in children if inhaled and was found to be deposited in the lungs of mice exposed to humidifier effluent. 11,12 Ultrasonic humidifiers efficiently aerosolize 85%-90% of dissolved minerals present in the water used to fill the humidifier. 10,13Indoor air quality is not frequently monitored within a household, although individuals spend ~90% of their time indoors 14 and tighter buildings are leading to higher contaminant concentrations and, therefore, increased exposures to inhalable contaminants. 15 Common sources of indoor particles include cooking (eg, frying, grilling, and the use of appliances such as stoves, ovens, microwaves), vacuuming, smoking, using photocopiers and color printers, and burning candles or incense, resulting in increases in particle concentrations 1.5-27 times | 81above background concentrations. [16][17][18] The increased exposure time to indoor air, combined with an ultrasonic humidifier's ability to efficient...

In 2014, crude (4-methylcyclohexyl)methanol (MCHM) spilled, contaminating the drinking water of 300,000 West Virginians and requiring "do not use" orders to protect human health. When the spill occurred, known crude MCHM physicochemical properties were insufficient to predict human inhalation and ingestion exposures. Objectives are (1) determine Henry's Law Constants (HLCs) for 4-MCHM isomers at 7, 25, 40, and 80°C using gas chromatography; (2) predict air concentrations of 4-MCHM and methyl-4-methylcyclohexanecarboxylate (MMCHC) during showering using an established shower model; (3) estimate human ingestion and inhalation exposure to 4-MCHM and MMCHC; and (4) determine if predicted air 4-MCHM exceeded odor threshold concentrations. Dimensionless HLCs of crude cis- and trans-4-MCHM were measured to be 1.42×10(-4)±6% and 3.08×10(-4)±3% at 25°C, respectively, and increase exponentially with temperature as predicted by the van't Hoff equation. Shower air concentrations for cis- and trans-4-MCHM are predicted to be 0.089 and 0.390ppm-v respectively after 10min, exceeding the US EPA's 0.01ppm-v air screening level during initial spill conditions. Human exposure doses were predicted using measured drinking water and predicted shower air concentrations and found to greatly exceed available guidance levels in the days directly following the spill. Odors would be rapidly detected by 50% of individuals at aqueous concentrations below analytical gas chromatographic detection limits. MMCHC, a minor odorous component (0.935%) of crude MCHM, is also highly volatile and therefore is predicted to contribute to inhalation exposures and odors experienced by consumers.

Sain et al | http://dx.

Manganese and iron are both internationally known causes of aesthetic issues in drinking water, however, there are limited data supporting their specific aesthetic guidelines, of which typical values are 0.05 mg/L Mn and 0.3 mg/L Fe. This study aims to clarify the concentrations at which off-flavors and off-colors caused by manganese and iron may be detected by consumers. Triangle tests of Mn(II) determined a best estimate taste threshold of 165 mg/L Mn(II), which is much higher than the reported range of 0.03-0.17 mg/L for Fe(II). Unlike Fe(II), Mn(II) taste tests showed there is no relationship between individual taste threshold and subject age. Mn(II) and Fe(II) oxidation in artificial saliva showed that Mn(II) had a non-detectable amount of oxidation and Fe(II) had up to 80% oxidation within 5 minutes at both 22 and 37 W C. Neither Mn(IV) nor Fe(III) exhibited detectable tastes. Visual testing of Mn(IV) and Fe(III), using the one-in-five forced choice method, showed that oxidized metals are visually detectable at concentrations below their typical aesthetic guidelines. Reduced Mn(II) and Fe(II) are colorless at concentrations much greater than established standards. This study demonstrates that current manganese and iron aesthetic standards may not be protective of off-flavors and off-colors.