Thread by @jeffgilchrist

Impact of inhaling PM from Ultrasonic Humidifiers using tap water

Some people were asking since particulate matter (PM) from tap water was soluble how dangerous is it compared to typical outdoor PM, wouldn't the PM just dissolve in the body easily again after inhalation? 🧵1/

I'm definitely not an expert in this area but thanks to Greg Kochanski @[e-mail] on M for finding this study "Effect of aerosol particles generated by ultrasonic humidifiers on the lung in mouse" ( ). 2/ncbi.nlm.nih.gov/pmc/articles/P…

Japanese Scientists back in 2013 tested the "white dust" generated by ultrasonic humidifiers to investigate their effect on the lung tissue of mice. They tested multiple types of water including tap water and ultrapure water may be similar to distilled water. 3/

While this doesn't tell us exactly what happens in humans, it at least provides information on how mice handle this type of PM. 4/

The TLDR version, "These results indicate that aerosol particles released from ultrasonic humidifiers operated with tap water initiated a cellular response but did not cause severe acute inflammation in pulmonary tissue." 5/

The good news is they didn't find any severe acute inflammation in the lungs but they did find "Inhalation of particles caused dysregulation of genes related to mitosis, cell adhesion molecules, MHC molecules and endocytosis". 6/

The authors conclude, "Additionally, high mineral content tap water is not recommended and de-mineralized water should be recommended in order to exclude any adverse effects." 7/

Why use the precautionary principle? It looks like there is at least one case study of a "young infant with significant accidental inhalational lung injury related to dispersal of mineral dust from an ultrasonic home-use humidifier" ( ). 8/pubmed.ncbi.nlm.nih.gov/21199854/

Back to the mouse model, they specifically look at minerals Na, Ca, Mg, and Si in the water but they do not mention any metals that are commonly found in tap water so I'm not sure if that would change the impact when present. 9/

The study subjected the mice to the ultrasonic humidifier operating with tap water either 8 hours/day for 7 days, or 24 hours/day for 7 days. There was no long-term study of impact conducted. 10/

They measured the PM from tap water producing 460 ug/m3 at 75% relative humidity which is about half the 800 ug/m3 that was detected inside the bedroom of my colleague running his ultrasonic humidifier ( ). 11/

https://twitter.com/jeffgilchrist/status/1753906606738125119

With Ultrapure water they only measured < 0.01 ug/m3 of PM confirming that type of water was not generating PM from the ultrasonic humidifier. 12/

Also interesting is they didn't find much change in their short 7-day experiments but did start to find an impact in their 14 day experiments so may not have discovered the full implications of long-term exposure. 13/

Using a transmission electron microscope (TEM) they observed PM particles had been ingested my macrophages in the lungs and eventually dissolved by phagocytosis ( ). 14/sciencedirect.com/science/articl…

Unfortunately they didn't test mice using regular tap water for 14 days but just 7 days. 15/

With the high-silica water which had higher levels of Si (73 mg/L vs 24 mg/L) but similar levels of other minerals as tap water they did find an impact on gene expression at 14 days where they did not at only 7 days. 16/

The significantly enriched pathways they found from inhaling PM generated from drinking water include Asthma, viral myocarditis, autoimmune thyroid disease, and type I Diabetes Mellitus among others, see table image for full listing. 17/

This study specifically looked at the impact of lungs on mice, but we also know that "PM2.5 can pass through the lung–gas–blood barrier and the 'gut–microbial–brain' axis"... 18/

...and "directly enter brain tissue via the olfactory nerve" so we might not have the complete picture of the long-term impact of PM exposure from tap water in ultrasonic humidifiers ( ). 19/ncbi.nlm.nih.gov/pmc/articles/P…

The authors found that the concentration of dissolved minerals in the water is linearly correlated to the amount of PM that is generated from ultrasonic humidifiers, so the less minerals the better, and distilled water has none so would be the safest choice. 20/

While it is quite possible that PM generated from using tap water with ultrasonic humidifiers isn't as harmful as breathing in outdoor PM from vehicle and industrial pollution or wildfires, it is probably best to minimize the amount of PM that you inhale long-term. 21/

@threadreaderapp please unroll

This thread was a result of digging deeper into the impact of the high levels of PM that were detected using tap water in ultrasonic humidifiers (but not evaporative humidifiers) which you can read more about here ( ). 22/

https://twitter.com/jeffgilchrist/status/1753906606738125119

You can learn more about humidity, health effects, the different types of humidifiers and their pros/cons from this article written by @joeyfox85 ( ). 23/itsairborne.com/intro-to-humid…