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An Industrial Hygienist’s Encounter with Dirty Sock Syndrome

Denise L. Daggett, MS, CIH The Scripps Research Institute La Jolla, CA daggett@scripps.edu. An Industrial Hygienist’s Encounter with Dirty Sock Syndrome . Case Study Outline. The Scene The Situation Testing and Results The “Resolution” and Lessons Learned Outrage Control.

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An Industrial Hygienist’s Encounter with Dirty Sock Syndrome

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  1. Denise L. Daggett, MS, CIH The Scripps Research Institute La Jolla, CA daggett@scripps.edu An Industrial Hygienist’s Encounter with Dirty Sock Syndrome

  2. Case Study Outline • The Scene • The Situation • Testing and Results • The “Resolution” and Lessons Learned • Outrage Control

  3. The Scene: The Scripps Research Institute (TSRI) • Academic research • > Million square feet of lab and office space • 13 lab buildings • ~500 fume hoods • 100% fresh air

  4. What is that smell? The Situation

  5. How It All Began • Late 2005 • Reports of odors in our large chemistry building • Musty • Grandma’s attic • Wet dog, wet burlap, wet money • Locker room • Isolated to a couple of labs • Occurred around mid-day • Worsened through the winter months • Disappeared in April

  6. Symptoms • Eye irritation • Upper respiratory irritation • Taste in mouth • Headaches • Nausea • Mild to severe responses

  7. Approached as an Indoor Air Quality Project • Interviews • Questionnaires • Odor logs and phone calls to notify • Air sampling • Outrage escalated each time an episode occurred • Brought in consultants • Offered medical evaluations with our Occupational Medicine Physician

  8. Additional Complaints • In 2008, occupants in another lab building reported same condition • Always in the cooler months • Same time of day • Occupants would point to certain supply grills as the source • Some of our neighboring companies and institutions were experiencing the same problems

  9. Pinpointing Origin • During an episode • Entered the air handler unit (AHU) feeding the lab • Odor present and very strong • Ah-Ha moment

  10. Fact Finding and Data Testing and Results

  11. Fact Finding • Searched the literature • Condition described as Dirty Sock Syndrome • Small HVAC units (cars) • Residential units • Large AHUs (sport arenas) • Odor due to bacteria and mold growth on the coils • Employees want to know • What the odor is • What is flying through the air • No description of the actual chemical composition

  12. The Experts • Spoke to: • Harvard researcher – mainly bacteria with a biofilm, odor is metabolites from mainly bacteria • Houston engineer – salts, dirt, and microbial material • Montana State University – bacteria with a biofilm • TSRI Occupational Medicine Physician – typical indoor air quality symptoms, likely will not cause permanent harm • What is a biofilm?

  13. Biofilm • forms when bacteria adhere to surfaces in aqueous environments and excrete a slimy, glue-like substance • can be formed by a single bacterial species, but more often consist of many species, debris and corrosion products • Other examples: plaque on teeth, slime on pet feed/water bowls Information and figure courtesy of the Center of Biofilm Engineering, Montana State University

  14. Sampling in an Air Handling Unit

  15. Working Theories about Causation Chemical Oxidized metal Salts Moisture Debris from fires Other debris Biological Bacteria w/ biofilm Mold Protozoa

  16. Sampling and Data:Chemical

  17. Sampling and Data: Biological

  18. Likely Not One or the Other but Both Chemical Biological Dew Point plays a role: When coil is damp, odor occurs. Is the smell from a wet coil (like wet pavement) or moistened biofilm?

  19. Biological and Chemical The “Resolution” and Paths Forward

  20. Next Step: Clean the Coils • First cleaning occurred in April 2009 • A few odor complaints, then gone for several months • Back in autumn • Outrage of occupants continues to simmer

  21. Cleaning and More Cleaning

  22. Biofilms and Antimicrobials • Biofilms are hard to breakdown and treat • Protection • Persister cells • Colony can reestablish in as little as 100 to 200 hours

  23. Coil Facts • Copper and other metal alloys • Fine fin width/huge surface area • 3 levels of filtration • Poly • Secondary • Final • All AHUs with problem are from the same manufacturer

  24. Coil Exposure Conditions • Constant exposure to salts, humidity • Wild fires in 2003, 2007 • Dew point & temperature differential plays a role

  25. What Now? • As predicted the odor dissipated for the summer • Odor returned Oct 2010 • Employees continue to be concerned • Now 5 buildings involved

  26. Pursued Another Path - UV • After 2009 cleaning, a UV system was installed • No benefit noted • 2010: a better designed UV system installed • Unfortunately, no improvement

  27. Still a Third Path: Bring in Help! • Issued an RFP • Identify odor source • Develop control strategy • Awarded contract this month • Winning company from Texas with experience

  28. Managing the Outrage • One-on-one conversations • Town hall-style meeting • Angry letters and conversations • Back to one-on-one conversations to key individuals • Technical summit

  29. Questions? daggett@scripps.edu

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