Risk Exposure during Showering and Water-Saving Showers

Abstract

Eco-friendly showers aim to lower energy and water consumption by generating smaller water droplets than those produced by traditional systems. To evaluate the risk of users inhaling the contaminants associated with such water droplets—namely, chemical components or opportunistic bacterial pathogens such as Legionella—we modeled the behavior of water droplets aerosolized by water-atomization technology at a flow rate of 2.2 L/min and compared the results obtained using this model with those determined experimentally in a typical shower stall. Additionally, we monitored the number and mass of inhalable water droplets emitted by twelve showerheads—eight using water-atomization technology and four using continuous-flow technology—which have distinct characteristics in terms of water flow rate, water pressure, spray angle, and number of and diameter of nozzles. The water-atomizing showers tested not only had lower flow rates, but also larger spray angles, less nozzles, and larger nozzle diameters than those of the continuous-flow showerheads. We observed a difference in the behavior of inhalable water droplets between the two technologies, both unobstructed and with the presence of a mannequin. The evaporation of inhalable water droplets emitted by the water-atomization showers favored a homogenous distribution in the shower stall. In the presence of the mannequin, the number and mass of inhalable droplets increased for the continuous-flow showerheads and decreased for the water-atomization showerheads. The water-atomization showerheads emitted less inhalable water mass than the continuous-flow showerheads did per unit of time; however, they generally emitted a slightly higher number of inhalable droplets (1.6 times more), including those large enough to carry a bacterium each—only one model performed as well as the continuous-flow showerheads in this regard. Further experiments are needed to assess whether this slight increase in the number of inhalable water droplets increases the biological risk.

Risk Exposure to Legionella pneumophila during Showering: The Difference between a Classical and a Water Saving Shower System

“…We selected two commercial showerheads, one continuous flow and one using the water atomization technology, among previously tested showerheads that emit the most water droplets in the bacterium size range [ 26 ]. The characteristics of these two showerheads models, namely STA for the continuous flow water technology and ECO for the water-atomizing technology, are described in Table 1 .…”

“…The showers were run inside a 815-PGB glove box “La petite glove box” at atmospheric pressure (variation between glove box and exterior environment did not exceed 0.5 kPa (0.077 PSI)). A Fisher Scientific pump model STERWINS-900 W, 3800 L·h −1 , 4.3 bars (Leroy Merlin, France) was used to draw the Legionella suspension from a 4 L reservoir through a flexible hose (150 cm) and showerhead (STA or ECO) at a water flow similar to that observed in the real sized shower cabin used for showerheads selection [ 26 ]. The water coming out from the showerhead (~2.75 L) was collected in a bag.…”

“…Water-efficient showerheads are devices aimed reducing water and energy consumption. The water flow rate of showerheads drastically decreased from 9 L/min for classical showers to 6 L/min [ 25 ] and even 2.8 L/min for showers that use water atomizing technology [ 26 ]. To reach these ecological goals, water atomization showerheads generate water droplets smaller than that produced by classic shower systems [ 27 ], which can increase the risk of exposure to bioaerosols generated from water-associated contamination, such as the bacterium Legionella .…”

“…This number is strongly influenced by the shower system characteristics (number of nozzles, nozzle diameter, spray angle, water pressure, etc. ), but also by the presence of a mannequin, which mimics the presence of the user under the shower [ 26 , 32 ]. We recently pointed out the differences between the two technologies in the behavior of inhalable water droplets emitted, both unobstructed and with the presence of a mannequin.…”

“…We recently pointed out the differences between the two technologies in the behavior of inhalable water droplets emitted, both unobstructed and with the presence of a mannequin. While the mass of inhalable droplets increased with the presence of the mannequin during showering events with a continuous-flow showerhead [ 26 , 32 ], it decreased when a water-atomizing showerhead was used [ 26 ]. Moreover, in the presence of the mannequin, the inhaled water mass was reasonably consistent among the water atomization showers.…”