Filed 11/9/23

CERTIFIED FOR PUBLICATION

IN THE COURT OF APPEAL OF THE STATE OF CALIFORNIA

SECOND APPELLATE DISTRICT

DIVISION SIX

DANA BRANCATI,

 Plaintiff and Appellant,

v.

CACHUMA VILLAGE, LLC,

 Defendant and Respondent.

2d Civ. No. B321616

(Super. Ct. No. 16CV03956)

(Santa Barbara County)

ORDER MODIFYING 

OPINION AND DENYING 

REHEARING

[NO CHANGE IN 

JUDGMENT]

THE COURT:

It is ordered that the opinion filed herein on October 16, 2023, be 

modified as follows:

1. On page 1, the first paragraph is deleted and the following 

paragraph is inserted in its place: 

Here we decide an expert is qualified to render an 

opinion on whether a person’s exposure to mold is 

harmful. It is up to the trier of fact to determine the 

expert’s credibility.

2. On page 1, line 5 of the second paragraph, the word “toxic” is 

deleted.

3. On page 2, line 3 of the second paragraph, the word “toxic” is 

deleted.

4. On page 5, the word “Toxic” is deleted from the heading 

“Evidence of Toxic Mold at Brancati’s Residence.”
2.

5. On page 5, the first sentence of the second full paragraph is 

changed to read: “Stachybotrys, aspergillus, and penicillium may 

be toxic.”

6. On page 6, the word “Toxic” is deleted from the heading 

“Simon’s Ability as a Medical Doctor to Diagnose Toxic Mold as 

the Cause of Brancati’s Respiratory Illness.”

7. On page 6, line 7 of the first full paragraph, the word “toxic” is 

changed to “hazardous.”

8. On page 6, the second sentence of the second full paragraph is 

changed to read: 

He was board certified in allergy and immunology and 

was qualified to testify about the impact of hazardous 

substances on Brancati’s respiratory tract (San Jose 

Neurospine v. Aetna Health of California, Inc., supra, 45 

Cal.App.5th at p. 960); the symptoms she suffered (Finn 

v. G.D. Searle & Co., supra, 35 Cal.3d at p. 704); and, as 

an “allergist,” he could identify the symptoms consistent 

with mold exposure.

9. On page 7, line 2 of the second full paragraph, the word “toxic” 

is deleted.

10. On page 8, line 3 of the first full paragraph, the word “toxic” 

is changed to “harmful,” and, in the same paragraph, line 6, the 

word “toxic” is deleted.

11. On page 9, the word “toxic” is deleted in three places: in the 

second, seventh, and last line of the first full paragraph.

12. On page 10, line 9 of the first full paragraph, the word “toxic” 

is deleted.

13. On page 11, line 2 of the last paragraph, the word “toxic” is 

deleted.

14. On page 18, line 1 of the first full paragraph, the word “toxic” 

is deleted.

There is no change in the judgment.
3. 

Respondent’s petition for rehearing is denied. 

GILBERT, P. J. BALTODANO, J. CODY, J.
Filed 10/16/23

CERTIFIED FOR PUBLICATION

IN THE COURT OF APPEAL OF THE STATE OF CALIFORNIA

SECOND APPELLATE DISTRICT

DIVISION SIX

DANA BRANCATI,

 Plaintiff and Appellant,

v.

CACHUMA VILLAGE, LLC,

 Defendant and Respondent.

2d Civ. No. B321616

(Super. Ct. No. 16CV03956)

(Santa Barbara County)

Here we decide an expert is qualified to render an opinion 

on whether a person’s exposure to toxic mold is harmful. 

Dana Brancati, a former tenant, appeals a judgment of 

dismissal following the trial court’s granting a motion in limine 

filed by defendant Cachuma Village, LLC (Cachuma), her

landlord. Brancati filed a complaint for, among other things,

personal injuries for exposure to toxic mold. Cachuma moved in 

limine to exclude Brancati’s medical expert from testifying about 

the medical causation of her illnesses due to mold. 

Because the medical expert was qualified and his opinion 

was based on facts and a differential diagnosis, the trial court 

erred in excluding his evidence. We reverse. 
2.

FACTS

Brancati entered a month-to-month lease with Cachuma to 

reside in its premises. She resided there from April 2012 to April 

2016. She complained to Cachuma about mold “infestation” and 

Cachuma’s failure to correct that problem. In 2016, Insight 

Environmental, a company that specialized in mold testing,

determined there were high levels of a variety of dangerous types 

of mold at her residence at Cachuma. 

Brancati filed a complaint for breach of the warranty of 

habitability, fraud, constructive eviction, and personal injuries 

for exposure to toxic mold. She alleged that she had suffered 

“respiratory illnesses” because of exposure to the mold. She 

sought $50,000 for her injuries. 

Brancati relied on the testimony of Ronald A. Simon, M.D.,

as her expert to prove the cause of her medical illnesses. At his 

deposition Simon testified that “as a result of living” in her home 

environment with “excess mold growth,” Brancati had “a variety 

of adverse health effects that started fairly shortly after she 

moved in there.” 

Cachuma moved in limine to exclude Simon from testifying 

on causation, or, alternatively, for an Evidence Code section 402 

hearing to determine admissibility. Cachuma claimed Simon was 

not qualified to testify on medical causation of Brancati’s 

illnesses due to mold.

In her opposition, Brancati claimed, “Dr. Simon’s testimony 

is not only based on both his examinations of [Brancati], but his 

experience and the scientific literature which establishes that 

exposure to damp moldy environments has negative effects on 

health.” 
3.

At a pretrial hearing, the trial court ruled Simon was not

qualified to testify on the medical causation issue. Brancati was 

not able to proceed to trial without Simon’s testimony. The trial

court dismissed this action.

DISCUSSION

Standard of Review

Where a trial court grants a motion in limine that prevents 

a party’s expert from testifying and leads to a dismissal, we 

review that order for an abuse of discretion. (Kelly v. New West 

Federal Savings (1996) 49 Cal.App.4th 659, 677; see also Geffcken 

v. D’Andrea (2006) 137 Cal.App.4th 1298, 1311 [“ ‘If the court 

excludes expert testimony on the ground that there is no 

reasonable basis for the opinion, we review the exclusion of 

evidence under the abuse of discretion standard’ ”].) 

Where the granting of a motion in limine “precludes an 

entire cause of action” or is tantamount to a nonsuit, we may also 

conduct our review de novo to determine whether the trial court 

erred as a matter of law. (Kinda v. Carpenter (2016) 247 

Cal.App.4th 1268, 1279; McMillin Companies, LLC v. American

Safety Indemnity Co. (2015) 233 Cal.App.4th 518, 530.)

Brancati presented evidence showing her expert is a

qualified medical doctor and a scientific researcher. She was 

prepared to present relevant evidence on the cause of her 

respiratory illness. The trial court’s ruling prevented her from 

having a trial. The court’s order is not consistent with the 

standard courts must use to decide whether to exclude an expert 

from testifying. 

Disqualifying Experts

“Trial judges have a ‘substantial “gatekeeping”

responsibility’ to ensure that an expert’s opinion is based on both 
4.

reliable material and sound reasoning.” (Bader v. Johnson &

Johnson (2023) 86 Cal.App.5th 1094, 1104.) “ ‘The trial court’s 

preliminary [or gatekeeping] determination whether the expert 

opinion is founded on sound logic is not a decision on its 

persuasiveness.’ ” (Id. at p. 1105.) “ ‘The court must not weigh 

an opinion’s probative value or substitute its own opinion for the 

expert’s opinion.’ ” (Ibid.) “ ‘Rather, the court must simply 

determine whether the matter relied on can provide a reasonable 

basis for the opinion or whether that opinion is based on a leap of 

logic or conjecture.’ ” (Ibid.) “ ‘The court does not resolve 

scientific controversies.’ ” (Ibid.)

In determining evidence of causation, the court applies a 

substantial factor standard. “ ‘The substantial factor standard is 

a relatively broad one, requiring only that the contribution of the 

individual cause be more than negligible or theoretical.’ ”

(Bockrath v. Aldrich Chemical Co., Inc. (1999) 21 Cal.4th 71, 79.)

“As a general rule, the factual basis of an expert opinion 

goes to the credibility of the testimony, not the admissibility, and 

it is up to the opposing party to examine the factual basis for the 

opinion in cross-examination.” (Bonner v. ISP Technologies, Inc. 

(8th Cir. 2001) 259 F.3d 924, 929.) “Only if the expert’s opinion is 

so fundamentally unsupported that it can offer no assistance to 

the jury must such testimony be excluded.” (Id. at pp. 929-930.)

Medical doctors are experts who are in the best position to 

determine the nature of illnesses experienced by patients. (San 

Jose Neurospine v. Aetna Health of California, Inc. (2020) 45 

Cal.App.5th 953, 960.)

Doctor Simon testified that Brancati’s “adverse health 

effects” were the result of her living at the Cachuma residence

where she was exposed to “excess mold growth.” The trial court 
5.

ruled Simon was not qualified to make a diagnosis of mold as the 

cause of her illnesses. But Simon’s opinion was based on facts,

not on a “leap of logic or conjecture.” (Bader v. Johnson & 

Johnson, supra, 86 Cal.App.5th at p. 1105.)

Evidence of Toxic Mold at Brancati’s Residence

The 2016 Insight Environmental testing report showed 

Brancati’s residence at Cachuma showed “high levels” of 

“aspergillus” and “penicillium” mold growth near her shower. Air 

samples from her hallway showed “elevated levels of 

Aspergillus/Penicillium and Stachybotrys mold growth.” (Italics 

added.) Insight Environmental said that stachybotrys, 

aspergillus, and penicillium produce “fungal metabolites that 

may be toxic” when “inhaled.” These are the types of mold that 

“produce mycotoxins.” It also determined that the “mold spores” 

at her residence “pose an immediate threat of occupant exposure.”

(Italics added.) Included within that report were color 

photographs that showed large concentrations of mold growth in 

various parts of Brancati’s Cachuma residence.

Stachybotrys chartarum, aspergillus, and penicillium are 

toxic molds. (Jarman & Felstiner, Mold Is Gold: But, Will it be 

the Next Asbestos (2003) 30 Pepperdine L.Rev. 529, 549.) 

Stachybotrys chartarum “has killed animals.” (Id. at p. 542.) It 

is “especially harmful to small children.” (Id. at p. 533.) Health 

professionals have linked it to sudden infant death syndrome. 

(Ibid.) “[E]xcessive exposure to mold has been a health issue for 

humans for many years.” (Id. at p. 534.)

Methods to Prove Mold as the Cause of an Illness

There are two methods used to prove mold is the cause of 

an illness. An expert may testify using a “methodology generally 

recognized in the scientific community” to determine mold as the 
6.

cause (B.T.N. v. Auburn Enlarged City School Dist. (N.Y.App.Div. 

2007) 845 N.Y.S.2d 614) and may rely on epidemiological studies 

to show a statistical link between exposure to the substance and 

the cause of the illness. (Johnson & Johnson Talcum Powder 

Cases (2019) 37 Cal.App.5th 292, 326.) Alternatively, a doctor 

who examines a patient may use a medical “differential 

diagnosis” to determine mold as the cause of a diagnosed illness. 

(B.T.N., at p. 1340; see also Cooper v. Takeda Pharmaceuticals

America, Inc. (2015) 239 Cal.App.4th 555, 586; Cottle v. Superior 

Court (1992) 3 Cal.App.4th 1367, 1384-1385.) Here Simon, as a 

medical doctor and a researcher, attempted to use both methods.

Simon’s Ability as a Medical Doctor to Diagnose Toxic Mold

as the Cause of Brancati’s Respiratory Illness

Medical doctors who examine patients may reach the most 

probable diagnosis for a patient’s condition through a process of 

elimination. (Cottle v. Superior Court, supra, 3 Cal.App.4th at 

pp. 1384-1385.) They are expected to identify the “source of a 

patient’s illness” (Finn v. G.D. Searle & Co. (1984) 35 Cal.3d 691, 

704) and diagnose “the nature of [the] disease . . . from a study of 

its symptoms.” (Ibid.) Doctors may consider exposure to toxic 

substances as a factor causing an illness. (Davis v. Honeywell 

Internat. Inc. (2016) 245 Cal.App.4th 477, 495.) 

Simon, a medical doctor, examined Brancati. He was board 

certified in allergy and immunology and was qualified to testify 

about the impact of natural toxic substances on Brancati’s 

respiratory tract (San Jose Neurospine v. Aetna Health of

California, Inc., supra, 45 Cal.App.5th at p. 960); the symptoms

she suffered (Finn v. G.D. Searle & Co., supra, 35 Cal.3d at 

p. 704); and, as an “allergist,” he could identify the symptoms 

consistent with toxic mold exposure.
7.

Simon testified that he conducted “a differential diagnosis” 

to determine the cause of Brancati’s illness. This is a standard 

method doctors use to eliminate potential causes of illness to be 

able to reach a diagnosis. (Cooper v. Takeda Pharmaceuticals 

America, Inc., supra, 239 Cal.App.4th at p. 586.) This process 

does not require doctors to eliminate all hypothetical causes 

before making a diagnosis. (Ibid.) A “proper differential 

diagnosis is adequate to support [an] expert medical opinion on 

causation.” (Westberry v. Gislaved Gummi AB (4th Cir. 1999) 178 

F.3d 257, 263; Kennedy v. Collagen Corp. (9th Cir. 1998) 161 F.3d 

1226, 1230.) 

Simon knew Brancati’s Cachuma residence was 

contaminated with toxic mold. He determined that she had the 

typical combination of “respiratory symptoms” of mold exposure 

that included “nasal congestion, runny nose, coughing, sneezing,” 

and the “exacerbation of her migraine headaches.” She also was 

“not . . . able to sleep” due to “respiratory” illness. Simon 

presented evidence to show these are the symptoms that have

been identified as being caused by mold exposure. “Testimony 

regarding objectively verifiable physical symptoms leading to a 

medical diagnosis is admissible as garden variety expert 

testimony.” (Ramona v. Superior Court (1997) 57 Cal.App.4th

107, 121.) Medical theories of causation of illnesses are 

admissible when based on standard diagnostic methods. (Roberti 

v. Andy’s Termite & Pest Control, Inc. (2003) 113 Cal.App.4th

893, 903.)

Simon considered the timing of Brancati’s symptoms. He 

determined the onset of her symptoms was consistent with her 

time in the Cachuma residence. Brancati did not have the 

“respiratory tract symptoms” until she moved to Cachuma. Her 
8.

symptoms “lessened when she moved out.” A “temporal 

connection” may be a “reliable indicator of a causal relationship.”

(Bonner v. ISP Technologies, Inc., supra, 259 F.3d at p. 931; 

Westberry v. Gislaved Gummi AB, supra, 178 F.3d at p. 265, 

italics added [a “temporal relationship between exposure to a 

substance and the onset of a disease or a worsening of symptoms 

can provide compelling evidence of causation”]; Martin v. Chuck 

Hafner’s Farmers’ Market, Inc. (N.Y. 2006) 814 N.Y.S.2d 442, 

443-444 [evidence that respiratory illness occurred after exposure 

to mold supported a triable issue of fact on causation].)

Brancati resided at Cachuma for four years. The 

“ ‘ “length, frequency, proximity and intensity of exposure” ’ ” to a 

toxic substance are factors “that a medical expert may rely upon 

in forming his or her expert medical opinion.” (Davis v. 

Honeywell Internat. Inc., supra, 245 Cal.App.4th at p. 495.) Here 

the level of exposure to the toxic molds was high and long term.

Simon’s determination that there was “excessive” mold is 

supported by the photographs in the mold testing report.

Before reaching his differential diagnosis of mold exposure, 

Simon prepared two medical reports where he eliminated several

potential causes for Brancati’s respiratory illness. He reviewed 

her “collateral allergic history” and found it was “totally 

noncontributory.” He reviewed a “four page allergy, asthma and 

immunology review form with her.” That is a standard procedure 

to “rule out other possible causes” in mold cases. (New Haverford

Partnership v. Stroot (Del. 2001) 772 A.2d 792, 800.)

Simon reviewed her current symptoms and past history of 

symptoms. He considered her medications. He reviewed her 

history of “past adverse drug reactions.” He considered whether 

her symptoms could be caused by laryngopharyngeal reflux 
9.

(LPR). But he rejected that as the cause because Brancati’s 

symptoms “are not the most typical LPR symptoms.” He 

considered her pre-existing conditions. He said Brancati had a 

“pre-existing” condition involving migraine headaches. But he 

determined her home environment had an aggravating impact on 

that condition because it “got much, much worse in the home” in 

Cachuma.

Simon determined whether Brancati would fall within the 

tiny percentage of people who are hypersensitive and have toxic 

allergic reactions to mold. He relied on a 2016 allergic skin 

testing report by Doctor Tubiolo who had examined Brancati. 

Simon concluded Brancati did not fall within that group. 

Brancati was normal and within the “99 percent” of the 

population who do not have such extreme toxic allergic reactions. 

In an allergy skin test report, Tubiolo found Brancati’s 

“inhalants” included “aspergillus” and other molds. That

aspergillus finding supported the conclusion that she had been 

breathing toxic mold.

Simon also conducted an “environmental survey.” 

Potential causes of allergic reactions may include smoking or pet 

allergies. (New Haverford Partnership v. Stroot, supra, 772 A.2d 

at p. 800.) But Simon eliminated those causes. He reviewed 

Brancati’s “smoking history” and found it was not relevant. He 

considered her history with cats and found that was not 

applicable in terms of allergies. He determined that she was 

“[n]egative for atopic disorders” and that she was physically “well 

developed.” He decided her “pulmonary function” was “within 

normal limits.” He found that her 2016 CT scan was, in relevant 

part, normal. He considered her “social history” and her “family 

history.” He excluded exposure to outdoor mold as a cause of her 
10.

illness because outdoor mold “get[s] dissipated” by the 

atmosphere. That is not the case with indoor mold. Simon could 

reasonably make these findings to exclude a number of potential 

causes in order to make a diagnosis. (Cooper v. Takeda 

Pharmaceuticals America, Inc., supra, 239 Cal.App.4th at p. 586; 

Wendell v. GlaxoSmithKline LLC (9th Cir. 2017) 858 F.3d 1227, 

1237 [“when an expert establishes causation based on a 

differential diagnosis, the expert may rely on his or her clinical 

experience as a basis for ruling out a potential cause of the 

disease”].)

Simon considered the 2016 mold testing report of Brancati’s

residence. It indicated that mold spores there posed an 

immediate threat of exposure. The air testing in that report was 

relevant on causation. A method “typically used to prove specific 

causation in mold cases is air sampling.” (Kanemoto, Scientific 

Expert Admissibility in Mold Exposure Litigation (2003) 26 

Hawaii L.Rev. 99, 129; New Haverford Partnership v. Stroot, 

supra, 772 A.2d at p. 800.) The air sampling, combined with a 

2016 medical report finding that she was breathing toxic mold, 

provided support for Simon’s theory.

A medical expert may also rely on published scientific 

studies showing odds ratios (OR) of 2.0 or more that show a 

causal effect between exposure to a substance and illness 

symptoms. (Johnson & Johnson Talcum Powder Cases, supra, 37 

Cal.App.5th at p. 326.) Simon relied on published studies. One 

study from Japan showed an OR of 4.36 for eye symptoms, 3.70 

for nose symptoms, and 3.45 for throat and respiratory symptoms 

for persons living in indoor environments containing dampness 

and visible mold growth. (Hope & Simon, Excess dampness and 

mold growth in homes: An evidence-based review of the 
11.

aeroirritant effect and its potential causes (May–June 2007) 28 

(No. 3) Allergy & Asthma Proceedings 264 (Hope & Simon), citing 

Saijo et al., Symptoms in relation to chemicals & dampness in 

newly built dwellings (2004) Internat. Archives of Occupational 

and Environmental Health.) Simon could rely on such studies to 

properly support his diagnosis and opinion.

Cachuma’s experts, who did not examine Brancati, claimed 

there might be causes for her illness other than indoor mold, such 

as her contact with horses. But a 2016 allergy skin test did not 

show any positive finding for Brancati inhaling “horse dander.” 

Simon prepared a medication plan for Brancati, and, as a 

treating doctor, he was in the best position to determine the cause 

of her illness (San Jose Neurospine v. Aetna Health of California, 

Inc., supra, 45 Cal.App.5th at p. 960) and to exclude other 

potential causes. (Wendell v. GlaxoSmithKlien LLC, supra, 858 

F.3d at p. 1237.)

Moreover, “[c]ausation is generally a question of fact for the 

jury, unless reasonable minds could not dispute the absence of 

causation.” (Lombardo v. Huysentruyt (2001) 91 Cal.App.4th 656, 

666.) Here there is a significant dispute. (See, e.g., Watters v. 

Dept. of Social Service (La.Ct.App. 2003) 849 So.2d 724, 733 

[genuine issue of material fact where in a dispute between 

experts, one doctor said mold was “capable of compromising the 

immune system”].) 

As a medical doctor, Simon could rule out other causes with 

his differential diagnosis and reach a probable diagnosis of toxic 

mold exposure as the cause of Brancati’s respiratory illnesses. 

(Roberti v. Andy’s Termite & Pest Control, Inc., supra, 113 

Cal.App.4th at pp. 901-902; Cottle v. Superior Court, supra, 3 

Cal.App.4th at pp. 1384-1385.)
12.

Simon’s Ability as a Scientific Researcher to Testify about the 

General Acceptance of His Theory in the Scientific Community

In addition to being a medical doctor, Simon is also a 

scientific researcher. His experience in that area provided 

additional support for his differential diagnosis that exposure to 

mold caused Brancati’s respiratory illness.

Simon researched the “aeroirritant” impact of moldy 

environments on health. He and another author published a 

peer-reviewed study on the aeroirritant effects of exposure to 

damp indoor environments. (Hope & Simon, supra, Allergy & 

Asthma Proceedings, at pp. 262-270.) In this published study,

Simon said, “[E]pidemiological studies support the link between a 

damp indoor environment and mold growth with upper airway 

irritant symptoms.” (Id. at p. 269.) Epidemiological studies may

show a statistical correlation between exposure to a substance 

and the cause of an illness. (Johnson & Johnson Talcum Powder 

Cases, supra, 37 Cal.App.5th at p. 326.)

Scientific researchers may opine on the scientific 

acceptance of their theories and the epidemiological factors and 

studies they relied on to reach their conclusions. (Bockrath v. 

Aldrich Chemical Co., supra, 21 Cal.4th at p. 79; Johnson &

Johnson Talcum Powder Cases, supra, 37 Cal.App.5th at p. 326;

Centex-Rooney Construction Co., Inc. v. Martin County (Fla. 1997)

706 So.2d 20, 26.) 

The trial court cited Geffcken v. D’Andrea, supra, 137 

Cal.App.4th 1298. There we held two scientific tests to link mold 

to illness had not achieved scientific acceptance, and an expert 

was not qualified to testify about a causal link between, among 

other things, mold and lung cancer. We noted that the plaintiffs’ 

theory was not supported by a single peer-reviewed scientific 
13.

reference and that the test results to prove causation were 

unreliable. There was no forensic investigation, there were chain 

of custody errors that invalidated the integrity of the sampling 

results, and samples had been inaccurately transposed. We also 

said our decision was fact specific and “[did] not constitute 

precedent for the exclusion” of evidence “under materially 

different factual scenarios.” (Id. at p. 1312, fn. 4.)

Brancati does not rely on the testing or theories mentioned 

in Geffcken and she does not claim mold causes cancer. The trial 

court’s reliance on Geffcken was misplaced. Our decision was not

intended to prevent medical doctors who examine their patients, 

as here, from performing a differential diagnosis to determine 

and opine on the cause of the patient’s illness. Moreover, as 

Brancati notes, there have been new scientific studies about mold 

that were not in existence in 2006 when we decided Geffcken.

Scientific Studies on Mold and Illness

Simon declared recent studies confirmed the scientific

accuracy and acceptance by the scientific community of his 

opinion about the link between respiratory diseases and exposure 

to mold. 

In 2016, in a statement on building dampness, mold, and 

health, the State Department of Public Health determined that 

“visible mold” or “mold odor” indicates “an increased risk of 

respiratory disease for occupants.” (Environmental Health 

Laboratory Branch, State Dept. of Pub. Health, Statement on 

Building Dampness, Mold, and Health (Feb. 2016) p. 1, italics 

added.)

In 2011, an Environmental Health Perspectives report

determined “[t]here is sufficient evidence of an association 

between indoor dampness-related factors and a wide range of 
14.

respiratory or allergic health effects.” (Mendell et al., Respiratory 

and Allergic Health Effects of Dampness, Mold, and DampnessRelated Agents: A Review of the Epidemiologic Evidence (June 

2011) 119 (No. 6) Environmental Health Perspectives 755, italics 

added.)

A World Health Organization (WHO) report in 2009 found 

a connection between exposure to mold and “increased 

prevalence[] of respiratory symptoms.” (WHO guidelines for 

indoor air quality: dampness and mould (Jan. 2009) <http:/

/www.who.int/publications/i/item/9789289041683> [as of Oct. 16,

2023], archived at <https://perma.cc/5SHE-7Z6M>.) 

In 2017, a review in the International Journal of Hygiene 

and Environmental Health determined that “indoor mold growth

must be considered as a potential health risk.” (Hurrass et al., 

Medical diagnostics for indoor mold exposure (2017) p. 306.)

A 2004 Institute of Medicine of the National Academies 

report, titled “Damp Indoor Spaces and Health,” concluded: 1) 

“There is sufficient evidence of an association between exposure 

to a damp indoor environment and upper respiratory tract 

symptoms,” and 2) “There is sufficient evidence of an association 

between the presence of ‘mold’ . . . in a damp indoor environment 

and upper respiratory tract symptoms.” (Id. at p. 194, italics 

added.)

A September 2017 report by the National Center for 

Environmental Health, Centers for Disease Control and 

Prevention, titled “Mold and Your Health,” concluded that for 

people sensitive to molds, “molds can cause nasal stuffiness, 

throat irritation, coughing or wheezing, eye irritation, or, in some 

cases, skin irritation.”
15. 

The United States Environmental Protection Agency (EPA) 

recently stated, “Research on mold and health effects is ongoing.” 

(U.S. EPA, Mold and Health (2023) <http:/ 

/www.epa.gov/mold/mold-and-health> [as of Oct. 16, 2023], 

archived at <https://perma.cc/YB8N-UL8J>.) But it noted, 

“Molds have the potential to cause health problems. Molds 

produce allergens (substances that can cause allergic reactions) 

and irritants. . . . [¶] [M]old exposure can irritate the eyes, skin, 

nose, throat, and lungs of both mold-allergic and non-allergic 

people.” (Ibid.) “Inhaling or touching mold or mold spores may 

cause allergic reactions in sensitive individuals. Allergic 

responses include hay fever-type symptoms, such as sneezing, 

runny nose, red eyes, and skin rash.” (Ibid.)

In addition to these studies, in a published article, Simon 

relied on additional scientific studies showing OR ratios well 

exceeding 2.0 for documented causal connections between 

exposure to damp and mold environments and various specific 

illness symptoms. (Hope & Simon, supra, Allergy & Asthma 

Proceedings, at pp. 264-265.) These were published studies from 

researchers in various countries, including Sweden, Taiwan, and 

Japan. (Ibid.) These studies used a scientific statistical method, 

considered similar causal factors, involved significantly large 

population groups, and their findings could be peer reviewed and 

duplicated. (Ibid.) Such studies, with such ratios, provided 

factual support for Simon’s theory about the causal link between 

mold and respiratory illness. (Johnson & Johnson Talcum 

Powder Cases, supra, 37 Cal.App.5th at p. 326.) 

Simon’s theory about mold exposure has “support in 

existing data, studies or literature.” (Marsh v. Smyth

(N.Y.App.Div. 2004) 785 N.Y.S.2d 440, 446.) General acceptance 
16.

“does not require unanimity, a consensus of opinion, or even 

majority support by the scientific community.” (People v. Leahy

(1994) 8 Cal.4th 587, 601.) The trial court may permit the 

introduction of “ ‘ “competing principles or methods in the same 

field of expertise.” ’ ” (Cooper v. Takeda Pharmaceuticals 

America, Inc., supra, 239 Cal.App.4th at p. 590.)

Judicial Decisions on Mold Exposure Causing Illnesses

Courts have found that “the scientific community has 

generally accepted the principle that a connection exists between 

the presence of mold and health.” (Mondelli v. Kendel Homes 

Corp. (Neb. 2001) 631 N.W.2d 846, 856, italics added.)

“[N]umerous publications accepted in the scientific community” 

recognize “the link between exposure to” highly “toxigenic molds” 

and “adverse health effects.” (Centex-Rooney Construction Co., 

Inc. v. Martin, supra, 706 So.2d at p. 26, italics added.) Although 

courts have been cautious about linking mold to a variety of 

illnesses, they have recognized that studies have linked “toxic 

effects as a result of mold exposure . . . to upper and lower 

respiratory tract symptoms.” (Young v. Burton (D.C. 2008) 567 

F.Supp.2d 121, 138.)

Consequently, courts have admitted expert evidence 

showing the specific causal link between molds and illnesses

suffered by parties. (B.T.N. v. Auburn Enlarged City School 

Dist., supra, 845 N.Y.S.2d at p. 615 [epidemiology evidence 

showed “atypical molds found to be present in the school building 

can cause plaintiffs’ symptoms”]; Martin v. Chuck Hafner’s 

Farmers’ Market, supra, 28 A.D.3d at p. 1067; Watters v. Dept. of 

Social Services, supra, 849 So.2d at p. 733; New Haverford 

Partnership v. Stroot, supra, 772 A.2d at pp. 797, 801 [expert 

testimony properly admitted to show cognitive defect symptoms 
17.

were the result of “exposure to atypical” mold]; Davis v. Fisher 

Single Family Homes, Ltd. (Ky.Ct.App. 2007) 231 S.W.3d 767, 

779 [expert permitted to testify about the “scientifically” valid 

“short-term health effects of mold exposure”]; Pauluk v. Savage

(9th Cir. 2016) 836 F.3d 1117, 1119 [doctors’ depositions 

“corroborated that [employee] was ill and that the illness was 

caused by mold”]; Caldwell v. Curioni (Tex.Ct.App. 2004) 125 

S.W.3d 784, 793 [treating doctors’ affidavits stating plaintiffs’ 

physical problems were caused “by exposure to mold infestation” 

were sufficient to overturn summary judgment for defendant

landlord]; Genna v. Jackson (Mich.Ct.App. 2009) 781 N.W.2d 

124, 130 [extremely high levels of mold “can cause” children’s 

symptoms of coughing, wheezing, vomiting, lack of oxygen, 

nosebleeds, and diarrhea].)

The scientific acceptance of the link between molds and 

illness has also been part of this state’s health public policy. 

California courts long ago found a link between mold and adverse 

health symptoms. (Miller v. Lakeside Village Condominium

Assn. (1991) 1 Cal.App.4th 1611, 1634 (conc. opn. of Johnson, J.) 

[“Mold in the condominium was the cause of all the symptoms”].) 

The California Toxic Mold Protection Act of 2001 requires 

landlords to disclose “the presence of toxic mold.” (JarmanFelstiner, Mold is Gold: But, Will it be the Next Asbestos, supra,

30 Pepperdine L.Rev. at p. 549.) Lawmakers enacted it to 

“[p]rotect the public’s health.” (Health & Saf. Code, § 26131, 

subd. (a)(2).) In 2016, the Legislature added major “visible mold” 

growth, confirmed by health officials, as a factor in classifying a 

premises as “substandard.” (Id., § 17920.3, subd. (a)(13).) 

Landlords are not shielded from liability for the presence of “mold 

infestation on the premises.” (Burnett v. Chimney Sweep (2004) 
18.

123 Cal.App.4th 1057, 1067.) They must provide safe and 

habitable premises. (Knight v. Hallsthammar (1981) 29 Cal.3d 

46, 52.) 

Federal courts have recognized the link between toxic mold 

and illness may constitute an “obvious health” hazard for the 

public. They have held that: 1) because apartments 

contaminated with mold constitute a threat to health, they may 

be condemned (Elsmere Park Club, L.P. v. Town of Elsmere (3d

Cir. 2008) 542 F.3d 412, 419); and 2) “[b]ecause removing an 

obvious health hazard is a matter of safety and not policy, the 

government’s alleged failure to control the accumulation of toxic 

mold in the Bangor commissary cannot be protected under the 

discretionary function exception” to the Federal Tort Claims Act. 

(Whisnant v. United States (9th Cir. 2005) 400 F.3d 1177, 1183, 

italics added.)

The trial court did not consider the deposition testimony of

Cachuma defense expert Marion J. Fedoruk, M.D. Fedoruk 

testified, “[M]old as being considered unhealthy in a building, 

obviously, generally, I would agree with that, yes.” From Simon’s

experience, his medical diagnosis, and the recent scientific 

literature, he could reasonably conclude that environments with 

high levels of aspergillus and stachybotrys, as here, form 

“aeroirritants” that had an adverse impact on Brancati’s 

respiratory health.

Cachuma claims that Simon’s research and theories are 

outside the mainstream and that his theory about “aeroirritant 

effects” is not based on traditional scientific wisdom and cannot

be used to support his testimony at trial. But this claim has been 

rejected. (Centex-Rooney Construction Co., Inc. v. Martin County,

supra, 706 So.2d at p. 26.)
19. 

 Moreover, on a motion in limine, the trial court “does not 

resolve scientific controversies” and it does not weigh the 

opinion’s “probative value.” (Bader v. Johnson & Johnson, supra, 

86 Cal.App.5th at p. 1105.) Those are matters for the jury at 

trial. Even if a theory involves a matter of scientific controversy, 

history shows new theories often replace the conventional 

scientific wisdom. Substances that were once thought to be 

harmless have later been determined to be dangerous, i.e., 

smoking, asbestos, lead paint, cyclamates, saccharin, Camp 

Lejeune drinking water, talcum powder, etc. 

Other Issues 

 Cachuma claims in Simon’s deposition he gave opinions 

about “MVOC” (microbial volatile organic compounds), but he 

was not an expert in that area, and he opined about a number of 

other factors based on speculation. Where an expert gives 

testimony in areas beyond his or her expertise, or provides 

speculation, that testimony may be excluded. (Jennings v. 

Palomar Pomerado Health Systems, Inc. (2003) 114 Cal.App.4th

1108, 1117; People v. Hogan (1982) 31 Cal.3d 815, 852, overruled 

on another ground by People v. Cooper (1991) 53 Cal.3d 771.) But 

Cachuma’s effort to completely prevent Simon from testifying in 

the various areas where he has expertise is unwarranted. 

 Cachuma contends Simon did not consider evidence of 

Brancati’s preexisting conditions before she moved into Cachuma. 

Her medical records show she was treated for an “upper 

respiratory infection” in 2009. But whether that infection is a 

preexisting condition or contradicts Brancati’s evidence on 

causation are matters for the trier of fact to resolve at trial. 
20. 

DISPOSITION 

 The judgment dismissing the action and disqualifying 

Doctor Simon from testifying is reversed. Costs on appeal are 

awarded to appellant. 

CERTIFIED FOR PUBLICATION. 

GILBERT, P. J. 

We concur: 

BALTODANO, J. 

CODY, J.
Timothy J. Staffel, Judge

Superior Court County of Santa Barbara

______________________________

Richard I. Wideman for Plaintiff and Appellant.

Mullen & Henzell, Rafael Gonzalez and Sean StratfordJones for Defendant and Respondent.