An Industrial Hygienist

1
An Industrial Hygienists Encounter with Dirty
Sock Syndrome

• Denise L. Daggett, MS, CIH
• The Scripps Research Institute
• La Jolla, CA
• daggett_at_scripps.edu

2
Case Study Outline

• The Scene
• The Situation
• Testing and Results
• The Resolution and Lessons Learned
• Outrage Control

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The Scene The Scripps Research Institute (TSRI)

• Academic research
• gt Million square feet of lab and office space
• 13 lab buildings
• 500 fume hoods
• 100 fresh air

4
The Situation

• What is that smell?

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How It All Began

• Late 2005
• Reports of odors in our large chemistry building
• Musty
• Grandmas 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

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Symptoms

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

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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

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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

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Pinpointing Origin

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

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Testing and Results

• Fact Finding and Data

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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

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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?

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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
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Sampling in an Air Handling Unit
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Working Theories about Causation
Chemical Oxidized metal Salts Moisture Debris
from fires Other debris
Biological Bacteria w/ biofilm Mold Protozoa
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Sampling and Data Chemical
Method/Comments Results
MIRAN unknown sample pulled into instrument cell and qualitative analysis against library CO2 and acetone
SUMMA Canisters taken inside AHU lab, EPA TO-15 analysis ppb levels of lab solvents acetone, chloromethane, methylene chloride, toluene
Prism Analytical sampling pumps and tubes for volatile organics of biological origin Prepped to sample Ppb ppt range of reporting Isobutyric acid, isovaleric acid
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Sampling and Data Biological
Method/Comments Results
Air-o-Cells indoors compared to outside Very low counts of Aspergillus/Penicillium types and Cladosporium, Basidoiospores
Swab samples Bacterial Moderate to high counts Bacillus species Gram and rods, Gram Cocci Fungal low counts Cladosporium, Aureobasidium Exophiala, Acrodontium
Scrapings from inside air handler looked like mold No biologicals high salts, metal oxides, and dirt
Biocassette samples bacteria and mold, taken inside the air handler No viable bacteria No viable fungi
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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?
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The Resolution and Paths Forward

• Biological and Chemical

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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

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Cleaning and More Cleaning
Date Action Coil Position
April 2009 Low pressure rinse, mild bleach solution, then rinse Removed hot and cold coils
January 2010 Water rinse, application of an EPA-approved coil cleaning product, then rinse Remained in place
February 2010 Cross plumbed hot water to cold coil, heated it up to 180 F, then application of coil cleaning product, then rinsed Remained in place
March 2010 April 2010 May 2010 Heated up cold coil, low pressure spray down, steam application, the use of a different EPA-approved biocidal material, then rinsed Remained in place
October 2010 November 2010 Cleaned the coil using another EPA-approved cleaning product which a neighboring company used Remained in place
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Biofilms and Antimicrobials

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

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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

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Coil Exposure Conditions

• Constant exposure to salts, humidity
• Wild fires in 2003, 2007
• Dew point temperature differential plays a role

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What Now?

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

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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

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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

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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

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daggett_at_scripps.edu

• Questions?