This case study illustrates the role of toxicological weight-of-evidence (WOE) in
a case involving exposure to mold inside a motor home. It also illustrates how analytical
measurements and medical history can be considered as evidential in a toxicological
analysis.
Bumpy Panels and Spongy Floors
Shortly after purchasing a new motor home, the owner noticed wind noise and water
leaks along the doors and windows as well as interior panels which had become "bumpy"
and discolored. At one point upon opening the glove box, the owner found mildewed
vehicle paperwork floating in water. Subsequent repairs were made by the dealer
on several occasions. The owner later took the vehicle on a trip to Florida and
left it parked for a month unattended.
Upon returning, mushrooms and mold were found growing in numerous locations. The
dealer again supposedly made repairs. Later, upon noting a "musky" smell
and removing the interior panels, the owner found one entire wall covered with black
mold. Peeled-back carpets revealed a black and spongy floor. The owner attempted
to clean and remove the mold without respiratory protection and continued to reside
in the vehicle while in Florida.
Several months later, a suspicious spot on the owner's lung was discovered during
a regular medical scan. Due to a family history of lung cancer, physicians opted
to excise the growth surgically. The pathology report confirmed that the spot was
an aspergilloma (fungus ball) growing on the lung. Independent expert sampling of
the vehicle's air measured an Aspergillus count of 5,020 cfu (colony forming units)
per m3 and a Stachybotrys count of 78 cfu/m.3
These very high spore concentrations were obtained "post-remediation."
Causation Methodology
The owner filed a lawsuit for damages, alleging negligence of both the manufacturer
and the repair shop(s). Dr. Sawyer was retained to perform an independent causation
assessment as an expert toxicologist for the plaintiff. Defendants contended that
the plaintiff's lung growth was not an aspergilloma and/or was spontaneous and not
related to the mold in the motor home. Defendants noted plaintiff's demonstrable
medical history with respect to respiratory infections and attempted to characterize
the malady as "merely the latest in a pattern." They contended that
the particular mold species in the vehicle could not have caused the aspergilloma
for which plaintiff had been diagnosed. They further objected to the methodology
used to determine the type(s) and quantities of mold present — and moved to
strike the results.
A pertinent issue with respect to causation in this matter was the fact that air
sampling was conducted long after exposure and only as a "snapshot" in
time rather than samples acquired over multiple days or weeks during the exposure
interval. Additionally, spores can heavily concentrate in small, undisturbed areas
and may appear far less numerous in larger-volume locations. Thus, air concentration
alone was insufficient to establish specific causation.
The Role of Weight-of-Evidence
Specific causation is more difficult to demonstrate than general causation. The
toxicologist must satisfy a stringent set of conditions before a causative conclusion
is reached. Dr. Sawyer elected to apply a weight-of-evidence (WOE) approach to his
assessment using the toxicological methodology developed by Sir Bradford Hill for
inferring causation. In practice, this amounts to exhaustive research and a process
of elimination achieved by thoroughly reviewing several types of evidence. This
includes the documented effects of the plaintiff's exposure and medical history as well
as all of the available experimental and human epidemiological literature.
Dr. Sawyer consulted the U.S. indoor air quality standards. He performed a thorough
review of the available toxicological journals and relevant peer-reviewed studies
(upon which much of the regulatory guidance is based). He assessed plaintiff's medical
history and reviewed chest x-rays over a period of years during which he established
that plaintiff's medical treatment had resulted in a condition called neutropenia,
a compromising of the immune system. In his final report, Dr. Sawyer stated:
- The generally-accepted, peer-reviewed literature cites immunodeficiency and
neutropenia as major risk factors for invasive pulmonary aspergillosis. The
risk of pulmonary aspergillosis correlates strongly with the duration and degree
of neutropenia.
- Plaintiff had been prescribed corticosteroids (Prednisone) for treatment
of a rotator cuff injury during the period of exposure. Various toxicological studies
cite three weeks of steroid therapy as a risk factor for aspergillosis.
- A study of aspergillosis cases from 24 medical centers1
revealed that one-third of patients diagnosed with aspergillosis had received corticosteroids.
The study cited corticosteroid use as a contributing factor to the documented aspergillosis
diagnoses.
- Measured levels of Aspergillus and Stachybotrys in the motor home air (5,020 cfu/m3 and 78 cfu/m3 respectively)
were in the extreme upper range of any values reported in the toxicological literature.
Concentrations of spores can accumulate within a small, enclosed area particularly
in the absence of air movement. The Indoor Air Quality Association2
recommends that no individual fungal organism should contribute more than 50 cfu/m.3
- The timeline associated with the circumstances was in every respect consistent
with plaintiff's exposure history and testimony (e.g. the discovery of mold, the
supposed vehicle repairs, the frequency of exposure, the calculated dose and the
subsequent discovery of the aspergilloma during a routine medical exam).
- A thorough review and investigation of other possible causes either ruled them
out entirely or rendered them so unlikely as to be safely discounted in this matter.
Dr. Sawyer's report concluded that the available toxicological evidence was entirely
consistent with plaintiff's testimony. He presented a specific causative opinion
that plaintiff had been afflicted with aspergilloma through repeated exposure to
concentrated toxic mold spores in an enclosed indoor area during the same period
of time that plaintiff had been rendered more susceptible to such infection through
regular corticosteriod treatments and immunodeficiency.
Daubert Challenge
Defendants took strong exception to Dr. Sawyer's report and filed a federal court motion to exclude
it under the Daubert Standard which provides rules of evidence governing the admissibility
of expert witness testimony during legal proceedings. Defendants' Motion To Exclude
contended that Dr. Sawyer's methodology was flawed and his conclusions unreliable.
Defendants further contended that Dr. Sawyer's testimony should be excluded because he did
not perform any independent testing of the motor home. However, many years had elapsed
between the first discovery of mold growth and Dr. Sawyer's retention as plaintiff's
expert. Since "independent testing" would have been impossible, Dr. Sawyer
relied on earlier testing performed by a CIH (Certified Induistrial Hygenist).
Defendants had retained an industrial engineering expert who specialized in molds
and fungi. He contended that (a) all of the mold in the motor home "might"
have been some other species and further contended that (b) there can be no "potential"
causative relationship (despite the measured levels of mold spores in the air samples);
therefore, none of plaintiff's expert reports (including Dr. Sawyer's) could be
considered to be scientifically reliable — and should, therefore, be excluded.
Dr. Sawyer pointed out in his rebuttal that it was not his opinion that plaintiff
had been infected with invasive Aspergillosis, but rather was hosting a species of
Aspergillus within her lung. With regard to defendants' contentions, Dr. Sawyer
noted that defendants' own expert had published materials to the effect that (a)
Aspergillus and Penicillium species are two of the most ubiquitous fungi known,
(b) it is common for both species to be present indoors, (c) high concentrations
of airborne spores can exist in contaminated indoor areas, (d) Aspergillus spores
can pose health risks when inhaled, and (e) they are known to cause respiratory
symptoms and diseases. Dr. Sawyer noted that it was not possible to reconcile these
facts with expert testimony that "...there can be no potential causative
relationship." This self-contradiction strongly suggested a lack of
objectivity on the part of defendants' expert.
Dr. Sawyer further noted in his rebuttal that the factors cited by regulatory agencies3 with regard to indoor air quality and building dynamics
closely mirrored plaintiff's own exposure. Dr. Sawyer additionally noted that all
causative factors relevant to the circumstances had been addressed in his assessment.
These included:
- Strength of association between the exposure and a particular health effect
- Specificity of the association
- Consistency of the association
- Dose-responsiveness of the chemical
- Biological plausibility of the causal connection
- Coherence of the association
- Temporality (time relationships)
- Relevant experimental data
Summary
Dr. Sawyer presented the court with an objective opinion of specific causation through
application of weight-of-evidence and the Bradford Hill method of causative determination.
In its ruling, the court noted that defendants' own expert stated that there is
currently no reliable method to determine the level of airborne toxins in an indoor
environment — but Dr. Sawyer's opinions were not based solely on air samples.
With respect to Dr. Sawyer in particular, the court stated:
Dr. Sawyer's analysis and opinions establish specific causation and are sufficiently
supported by scientific data and evidence in the record. Before concluding that
plaintiff's exposure to the levels of toxic mold in the vehicle is consistent with
the diagnosis of aspergilloma, Dr. Sawyer detailed plaintiff's pertinent medical
history, weakened immune system, family's medical history, and history of hospitalizations
and cigarette smoking. He also noted that aspergillus grows on organic debris and
occurs naturally in some outdoor and hospital environments. It is reasonable to
infer that Dr. Sawyer took into account, and ultimately ruled out, these possible
factors before concluding that the high levels of aspergillus, penicillium, and
stachybotrys found in the vehicle caused the medical condition. … Dr. Sawyer
noted that the levels of aspergillus found in the vehicle "are in the extreme
upper range of any values ever reported in the literature for living quarter environments."
… [therefore] defendants' motion to preclude plaintiff's expert is DENIED.
Outcome
The court's written ruling characterized defendants' objections as "unpersuasive."
The inclusion of Dr. Sawyer's toxicological assessment and testimony significantly
undermined defendants' credibility and position in litigation. Defendants elected
to settle the case ahead of a likely jury verdict in favor of plaintiff.
(Disclaimer: Toxicology case studies are impartial and objective summaries of toxicological
matters in which TCAS was retained for the purpose of assessing health-based
factors which, in some cases, led to a determination of causation. No names or identifying
information have been provided due to privacy and legal considerations. In the above
matter, Dr. Sawyer was retained by plaintiff.)
Notes and References
- Perfect, JR, et al., "The impact of culture isolation of Aspergillus species:
a hospital-based survey of aspergillosis," 2001, Clinical Infectious Diseases,
Vol. 33, pages 1824-1833.
- Indoor Air Quality Association, Inc., "Recommended guidelines for indoor
environments," IAQA01-2000, Longwood, Florida.
- New York City Department of Health and Mental Hygiene, "Guidelines
on assessment and remediation of fungi in indoor environments," Appendix
A, November 2008
Images
- Photo by TCAS © Copyright 2017, adapted from case report
- Photo by TCAS © Copyright 2017, adapted from case report
- Photo by TCAS © Copyright 2017, adapted from case report
- Photo by TCAS © Copyright 2017, adapted from case report
- Photo by TCAS © Copyright 2017, adapted from case report