Aerosolization of Drinking Water Metals to Indoor Air and Assessment of Human Taste and Visual Thresholds for Manganese

Exposure to excess manganese via drinking water raises concerns due to potential for adverse neurological impacts, particularly in children. Manganese is ubiquitous in US groundwaters above the SMCL = 0.05 mg/L. Manganese is an essential nutrient, but exposures to elevated manganese have neurotoxic effects. Chapter 2 focuses on human senses' ability to detect manganese in drinking water. Findings indicate human senses cannot be relied upon to detect excess Mn(II) in drinking water. Mn(IV) is easily visually detected, but cannot be tasted at 10 times the SMCL. Chapter 3 is an assessment the ability of an ultrasonic humidifier to expel drinking water impurities in aerosols. The quality of the water used to charge the humidifier reservoir affects the composition of elements in the aerosols and condensate. Findings indicate condensed humidifier aerosols contain 85% of elements present in the reservoir water for a variety of water types if there is no precipitation. Waters with high concentration of hardness or iron formed precipitates that decreased the concentrations of these metals in the aerosols causing variable results for other elements that were initially present at < 1mg/L in the charge water. This indicates that humidifiers could be a source of inhalation exposure for source water contaminants.