Joe Spurgeon, PhD – Can Airborne Mold Samples be Interpreted Objectively Using Numerical Guidelines?

Air Date: 11-30-2018|Episode 525

This week we welcome back Dr. Joe Spurgeon to continue our conversation on the use of sampling as part of a mold inspection. We will focus on his latest paper and answer the question can airborne mold samples be interpreted objectively using numerical guidelines?

Dr. Spurgeon has a multidisciplinary doctorate degree in Analytical Chemistry and Environmental Health from the University of Pittsburgh; and was a Certified Industrial Hygienist from 1993 – 2013. His career has included working as a research chemist on the NBS Lead-Paint Poisoning Program, directing the FAA’s Combustion Toxicology Laboratory, performing Health Assessments for CDC/ATSDR, implementing US EPA’s Laboratory Exposure Assessment Project, and working as a consultant specializing in microbial indoor air quality for US PHS. He has performed over 4,000 residential and commercial investigations involving water intrusions and microbial contaminants; has taught courses on mold investigations, sampling, and data interpretation methods; and has served as an expert witness in numerous mold cases. Additional articles from Dr. Spurgeon are available at His books are available at

Z-Man’s Blog:

Assessing the Condition of Indoor Air Using Airborne Samples
This week IAQ Radio welcomed author, consultant, industrial hygienist and accomplished industry professional Joe Spurgeon, Ph.D. to discuss his opinions on mold sampling and sampling interpretation
Nuggets mined from today’s episode:
Joe Spurgeon, as an expert witness, interprets mold samples and reviews reports prepared by others. Many inspectors simply submit their lab report with a cover page without any interpretations or acknowledgement of patterns and correlations. He suggested the IAQ community could do better; and seeks improvement in the status quo.
Elements of a mold inspection: Incident History, Visual Inspection, Sampling Plan, Occupant Symptoms, & Forensic Investigation. Sampling is only one part, but an important part, of an inspection. When you don’t sample you can miss about a third of problem properties.
As inspectors must work within the client’s budget, he advocates proposal of a complete inspection protocol,which protects the inspector, from which the client can choose services from the menu. He provides a perspective of what he feels should be done.
Lab reports, which contain numerical results, cannot be interpreted objectively or consistently without reference to numerical guidelines.
The commonly utilized Reference Method of comparing Indoor samples to Outdoor samples is flawed. Using Indoor vs Outdoor comparisons may do a better job of assessing the variability of the outdoor air rather than assessing the condition of the indoor air.The method lacks Significance of results, Objectivity of criteria, Consistency of application, and Stability of the basis for comparison.
The InstaScope instrument (DetectionTek), an example of an emerging technology, provides data that meets the “SOCS” criteria- Significance, Objectivity, Consistency & Stability.
He opines the primary task of a mold inspector is to differentiate between normal and contaminated indoor environments; with this discussion focusing on the indoor air. He suggests this be done by using a data base to compare current results to previous results, and compare contaminated areas to uncontaminated areas as in the Control Method, and then make decisions based upon empirical guidelines or decision criteria.
Inspectors who do not follow sample manufacturer’s recommendations may be at legal risk. Example is using a different airflow rate for collecting wall cavity samples.
Current status of air sampling is that assessments of condition are subjective, and criteria are applied inconsistently across projects and between inspectors.
According to an informal survey of labs, 85%-90% of airborne samples are collected with Slit impaction cassettes.
Purpose of today’s discussion is to propose distribution method, which supports numerical guidelines.Distribution method assesses a sample result by comparing it to samples previously collected in similar environments; similar in concept to the Control Method. This method has been used in the environmental sciences for decades.
Guidelines were based on two databases; 450 “National”Samples and 204 “California” Samples. The National samples,contributed by Dan Bridge , included 450 indoor samples and 235 outdoors collected in 117 properties located in 23 cities in 9 states}. The California samples, contributed by Jack Clausen, included 204 indoor samples collected in 88 residential properties in southern California.
Decision criteria were: Asp/pen of 750 spores/m3 or less is typical; 750-1,500 spores/m3 is uncertain; and Asp/Pen greater than 1,500 spores per m3 is contaminated. Similar to Green-Yellow-Red for the DetectionTek InstaScope.
Applicability of conclusions- statistically robust databases; so presumably guidelines applicable to residences properties in general.These numerical guidelines were the same for (1) both National and CA databases, and (2) Air-O-Cell and Allergenco-D cassettes.
Guidelines established using a simple method. Using Asp/Pen transitional concentrations in rank-order plots of concentration v sample number.
Objective of mold inspector may be to assess building-related contamination or occupant exposure potential; different tasks, different methods (Example: examine cooling coils or sample supply ducts?)
Building-related Guidelines for interpreting indoor airborne samples
  • Asp/pen       < 750 normal      Use Pro Judgement       >1500 contaminated
  • Clad             <900 normal       Use Pro Judgement       >2000 contaminated
  • Total spores <2500 normal    Use Pro Judgement        >8000 contaminated
Important! The sample result is being interpreted, not the condition of the indoor environment.
The CA data were characterized by water damage, health complaints, and visible mold in the properties that were sampled. Average occupant exposures were 5-6 times higher in water-damaged properties compared to properties with no water damage.
Asp/Pen spores/m3 in properties without water damage ( normal, uncontaminated indoor air) were:
  • Less than 750 spores/m3 in 95% of samples
  • Less than 1,000 spores/m3 in 97% of samples
  • Less than 1,500 spores/m3 in 99% of samples
Conclusion: Very unlikely for Asp/Pen concentration to be higher than 1,500 spores/m3 if sample collected from normal, uncontaminated indoor air. Therefore, an Asp/Pen concentration greater than 1,500 spores/m3 was likely collected from an area with elevated airborne mold spores.
Based on the No Observed Effect Level (NOEL) for Penicillium chrysogenum, he estimated that average airborne mold concentrations of 1,000-2,000 spores/m3 would be sufficient to initiate adverse health effects in occupants. These average Asp/Pen concentrations were exceeded in at least 30% of the 117 properties included in the National database.
Joe would like to see a professional or working group gather data, construct distributions and criterion, and make the information available to their stakeholders.
Reference method, compares indoor to outdoor concentrations, and is often not the best method to use. Dr. Dan Bridge, PhD conducted a broad study collecting indoor and outdoor samples. [450 samples were collected, in 117 houses, in 23 cities, in 9 states, and over 2 years]. When indoor samples were compared to the outdoor samples, little correlation was demonstrated; and no valuable data was provided. However, when indoor samples were compared in rank order usable, actionable guidelines were obtained which also enabled future samples to be interpreted.
Control method used in commercial buildings, differentiates between normal background and contaminated areas. The method described by Dr. Spurgeon is similar to the Control Method. Mentioned in the Bioaerosols manual (1999) control samples should always be pulled in commercial buildings for present and future data comparison. Dr. Spurgeon also recommends pulling control samples in residential buildings. Comparing individual indoor-outdoor samples is not recommended by ACGIH, but comparing distributions of concentrations is recommended.
Data base method while not used in IAQ it is used in industrial hygiene comparing distribution of concentration rather than concentrations and is a more science-based data-interpretation method. For example: enter the Asp/Pen sampling results from the last 50 inspections on a spread sheet in rank order (from lowest to highest concentration). Compare current results to range of concentrations; when current results are in the 60th-70thpercentile that’s a typical concentration, if greater than the 70th percentile the concentration is elevated.
Sampling is one tool in the IEP’s tool box, others include: visible signs of moisture, incident reports of water damage, occupant health survey and sample results. Some sampling is a critical part of all mold investigations.
Investigator must understand the objective of what he is trying to accomplish; determine building-related contamination or occupant exposure potential. Slit-impaction cassettes may be useful for assessing building contamination, but they should be used with caution for assessing occupant exposure if their limitations are not considered as part of the assessment.
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Z-Man signing off
Trivia Question:
Name the Hollywood celebrity who added a fake 11th finger to his handprint at Los Angeles’ famous TCL Chinese theatre.
Trivia Answer:
Mel Brooks