How Clean Are Your Dishes?

by updated 2011/07/17

Recently a group of European scientist found that our dishwashers may be hosting a once rare organism, the Black Yeast Fungus, (Exophiala dermatitidis or E. phaeomuriformis).  These organisms were once rare in nature, but have apparently taken a liking to the harsh, hot, moist, area around the seals of our dishwashers.  Upon reading about this, I immediately inspected our dishwasher.  I had to look closely as we try to keep the dishwasher clean but guess what I found at the inside bottom of the door seal?  Yes indeed, in a spot that was not readily visible unless you took out the bottom tray and stuck you head inside, a build up of a black coating.  Of course I don’t know if it is the specific organism referred to in all the recent publicity, but its looks sure fit the part.

These fungi are very tolerant to extremes of temperature, salt, acidity, alkalinity; and don’t mind the dishwasher detergent at all. I found a quote from one of the microbiologist researchers, Nina Gunde-Cimerman, that seemed to be quite alarming.

“We tested the dishes after they had been cleaned in these dishwashers and they were full of this black yeast, so too the cutlery that you put in your mouth. We just don’t know how serious this could be.”

These statement were also attributed to the researchers:

“The invasion of black yeasts into our homes represents a potential health risk”

“The discovery of this widespread presence of extremophilic fungi in some of our common household appliances suggests that these organisms have embarked on an extraordinary evolutionary process that could pose a significant risk to human health in the future.”

The first thing that I wonder is how dangerous these fungi really are to normally healthy people. I am reminded of the sometime hysterical press in recent years that could make you think all of our homes are unfit for habitation because of mold spores.   Yes some homes are really infested, but the levels in the vast majority of houses seem to pose no threat to otherwise healthy occupants.  Maybe that is the case here also?  Specifically it is stated that these fungi are a real danger to Cystic Fibrosis patients.  That is surely an important bit of information for these people, their families, and their doctors.  But it really says nothing about the risk to the rest of us.

I found that Frank Odds, a Professor of Medical Mycology at The University of Aberdeen has some thoughts on the risks:

“There’s absolutely no reason why anyone should be upset by finding any kind of fungus around their house. Yes, they cause infections, but luckily for us they’re very rare, We breathe millions of mold and spores and yeast particles every minute of the day and we seem to be well adapted to not being affected by them…  The exception is for people who are very ill, are immunosuppressed, or have had transplantation surgery”

I found several articles that state these fungi are common on shower curtains and along the edges of bath tubs and sinks.  That seems questionable to me as I always thought that stuff was mold, not fungus.  That would also go against the statement by the researchers that these fungi where, until recently, rare.  At least in many of the showers and baths I have frequented over the years, that black stuff was anything but rare.  I have always had to keep is at bay with periodic cleanings with bleach.

For now I will just clean off the inside of our dishwasher more frequently and keep an ear open for further news about any real risk.  With five people at home this summer, I don’t think we are going to retire the dishwasher anytime soon!

Will Sig

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