PMID- 34800908 OWN - NLM STAT- MEDLINE DCOM- 20211208 LR - 20211214 IS - 1879-2448 (Electronic) IS - 0043-1354 (Linking) VI - 207 DP - 2021 Dec 1 TI - Risks to children from inhalation of aerosolized aqueous manganese emitted from ultrasonic humidifiers can be greater than for corresponding ingestion. PG - 117760 LID - S0043-1354(21)00954-4 [pii] LID - 10.1016/j.watres.2021.117760 [doi] AB - The essential trace element manganese (Mn) can cause neurotoxicity with inhalation acknowledged as a more severe health and cognition threat than ingestion. METHODS: Over a range of aqueous Mn concentrations present in tap water, this research characterizes exposures and risks for adults and 0.25, 1, 2.5, and 6 yr old children who ingest the water and inhale respirable particles produced by a room-sized ultrasonic humidifier filled with the same water. Aqueous Mn concentrations evaluated included 50 microg/L USEPA esthetic guideline, 80 microg/L WHO infant guideline, and 120 microg/L Canadian regulatory level. Airborne-particle-bound Mn concentrations were generated for water filling an ultrasonic humidifier under four realistic room conditions (33 m(3) small or 72 m(3) large) with varying ventilation rates from 0.2/h -1.5/h. Average daily doses (ADD) and reference intake doses were calculated for ingestion and 8-h inhalation of humidified air. Hazard quotients (HQ) compared the intake doses and reference doses. Multi-path particle dosimetry (MPPD) model quantified the particle deposition and deposited dose in children's and adults' respiratory tracts. RESULTS: At only 11 microg/L Mn, the resulting humidified air Mn exceeds USEPA's reference concentration of 0.05 microg/m(3) Mn in small room with low, energy-efficient ventilation. Inhalation ADD are 2 magnitudes lower than ingestion ADD for identical water Mn concentrations and daily exposure frequency. Even so, ingestion HQs are approximately 0.2 but inhalation risk is significant (HQ>1) for children and adults when breathing Mn-humidified air under most small room conditions at 50, 80 or 120 microg/L Mn. MPPD model indicates inhaled Mn deposits in head and pulmonary regions, with greater Mn dose deposits in children than adults. CONCLUSION: Inhalation of Mn-particles produced from ultrasonic humidifiers can pose greater risks than ingestion at the same water concentration, especially for children. Aqueous Mn concentration and room size influence risks. Limiting manganese exposures and setting regulations requires consideration of both ingestion and inhalation of water. CI - Copyright (c) 2021. Published by Elsevier Ltd. FAU - Yao, Wenchuo AU - Yao W AD - Department of Civil and Environmental Engineering, Virginia Tech, 413 Durham Hall, Blacksburg, Virginia 24061, United States. FAU - Gallagher, Daniel L AU - Gallagher DL AD - Department of Civil and Environmental Engineering, Virginia Tech, 413 Durham Hall, Blacksburg, Virginia 24061, United States. FAU - Dietrich, Andrea M AU - Dietrich AM AD - Department of Civil and Environmental Engineering, Virginia Tech, 413 Durham Hall, Blacksburg, Virginia 24061, United States. Electronic address: andread@vt.edu. LA - eng PT - Journal Article DEP - 20211014 PL - England TA - Water Res JT - Water research JID - 0105072 RN - 059QF0KO0R (Water) RN - 42Z2K6ZL8P (Manganese) SB - IM MH - Adult MH - Canada MH - Child MH - Eating MH - Humans MH - *Humidifiers MH - Infant MH - Inhalation Exposure/analysis MH - *Manganese MH - Ultrasonics MH - Water OTO - NOTNLM OT - Indoor air OT - Ingestion OT - Inhalation OT - Manganese OT - Ultrasonic humidifier EDAT- 2021/11/21 06:00 MHDA- 2021/12/15 06:00 CRDT- 2021/11/20 20:25 PHST- 2021/07/06 00:00 [received] PHST- 2021/09/22 00:00 [revised] PHST- 2021/10/10 00:00 [accepted] PHST- 2021/11/21 06:00 [pubmed] PHST- 2021/12/15 06:00 [medline] PHST- 2021/11/20 20:25 [entrez] AID - S0043-1354(21)00954-4 [pii] AID - 10.1016/j.watres.2021.117760 [doi] PST - ppublish SO - Water Res. 2021 Dec 1;207:117760. doi: 10.1016/j.watres.2021.117760. Epub 2021 Oct 14.