Walters et al v. Flint et al

Filing 487

OPINION AND ORDER granting in part and denying in part 335 Motion to Exclude the Testimony and Report of Dr. William Bithoney. Signed by District Judge Judith E. Levy. (WBar)

UNITED STATES DISTRICT COURT
EASTERN DISTRICT OF MICHIGAN
SOUTHERN DIVISION
In re Flint Water Cases

Judith E. Levy
United States District Judge

__________________________________/
This Order Relates To:
Bellwether I Cases
Case No. 17-10164
__________________________________/
OPINION AND ORDER GRANTING IN PART AND DENYING IN
PART DEFENDANTS VEOLIA NORTH AMERICA, LLC, VEOLIA
NORTH AMERICA, INC., AND VEOLIA WATER NORTH
AMERICA OPERATING SERVICES, LLC’S MOTION TO
EXCLUDE THE TESTIMONY AND REPORT OF DR. WILLIAM
BITHONEY [335]
This opinion is the fourth in a series addressing the admissibility of
the testimony and reports of eight experts retained by Plaintiffs in
anticipation of the first bellwether trial, currently set to begin on
February 15, 2022. Defendants argue that none of these experts can meet
the standards set by Federal Rule of Evidence 702 and Daubert v. Merrell
Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993).

Currently before the Court is the motion by Veolia North America,
LLC, Veolia North America, Inc., and Veolia Water North America
Operating Services, LLC (collectively “VNA”) to exclude the testimony
and reports of Dr. William Bithoney (ECF No. 335.) The LAN and LAD
Defendants join VNA’s motion. (ECF No. 344.) For the reasons set forth
below, VNA’s motion to exclude is GRANTED IN PART and DENIED IN
PART.
I.

Background

Dr. William Bithoney is a medical doctor with over 40 years of
experience diagnosing and treating lead exposed children. (ECF No. 436,
PageID.33913-33919). He is currently a consulting physician for the
NAACP Lead Poisoning Project in Indiana and the Chief Medical Officer
at Ninth Dimension Biotech. (ECF No. 373-2, PageID.24686.) Dr.
Bithoney’s qualifications as an expert are not disputed.
Plaintiffs seek to offer Dr. Bithoney as an expert on both general
and specific causation. They retained Dr. Bithoney to determine (1)
whether lead-poisoning could cause the adverse health effects they have
experienced (general causation), and (2) whether lead-poisoning in fact
did cause those adverse effects (specific causation) in the four bellwether
2

Plaintiffs. Some of Dr. Bithoney’s expected testimony is also relevant to
the element of injury. Dr. Bithoney’s opinions as to each element are
summarized below.
A. General Causation Opinions
Dr. Bithoney indicates that there is a very strong scientific
consensus that exposure to lead, even in very small quantities, can cause
the neurocognitive symptoms experienced by Plaintiffs.
Dr. Bithoney first notes that lead exposure can cause decreased
academic achievement. (E.g., ECF No. 330-19, PageID.15042.) That
conclusion is primarily based on a study which showed that for every 1
g/dl increase in blood-lead concentration, there was a 0.7 point decrease
in arithmetic scores, a 1 point decrease in reading scores, a 0.1 point
decrease in scores on a measure of nonverbal reasoning, and a 0.5
decrease in scores on short-term memory tests. Bruce P. Lanphear et. al.,
Cognitive Deficits Associated with Blood Lead Concentrations <10
mcg/dl in U.S. Children and Adolescents, 115 Public Health Reports 521
(2000) (“Lanphear (2000)”); See also ECF No. 330-19, PageID.15043
(discussing Lanphear study).

3

Dr. Bithoney also considers research that addresses the causal link
between overall decrements in intelligence and lead exposure. As early
as the 1990s, studies found that minimal exposures to lead could cause
decreases in IQ. A 1994 meta-analysis found with a margin of error of
less than 0.001% that lead poisoning could cause decreases in IQ at blood
lead levels as low as 1 g/dl. Joel Schwartz, Low-Level Lead Exposure and
Children’s IQ: A Meta-analysis and Search for a Threshold, 65
Environmental Research 42, 53 (1994) (“Schwartz (1994)”). So far, no
study has discovered any threshold below which lead does not cause such
harms.
Dr. Bithoney testified that he further reviewed the Toxicological
Profile for Lead, an exhaustive literature review published by the Agency
for Toxic Substances and Disease Registry (“ATSDR”). (ECF No. 436,
PageID.34038-34039.) The Toxicological Profile is one of the most
authoritative sources available on the topic of lead poisoning. It, too,
concludes that lead can cause decrements in intelligence at very low
levels of exposure. See ATSDR, Toxicological Profile for Lead (Aug. 2020)
(https://www.atsdr.cdc.gov/ToxProfiles/tp13.pdf) (“Toxicological Profile”),

4

at 140-176 (reviewing published studies showing a link between lead
exposure and decreases in IQ).
Dr. Bithoney

next

opines that

lead exposure can

cause

neurobehavioral concerns, including attention deficit hyperactivity
disorder (“ADHD”). His report cites to several studies supporting that
conclusion. A study by Lisa M. Chiodo reviewed what is known as lead’s
“behavioral signature,” which includes symptoms “in the specific
domains of attention, executive function, visual-motor integration, social
behavior, and motor skills.” Lisa M. Chiodo et al., Neurodevelopmental
effects of postnatal lead exposure at very low levels, 26 Neurotoxicology
and Teratology 3, 359-371, at 359 (2004) (“Chiodo (2004)”). Chiodo
concludes that lead poisoning is directly associated with “higher ADHD
and inattention scores…and poorer attention.” Id. at 365. Moreover,
according to Chiodo, toddlers exposed to lead “had more difficulties with
emotion regulation and behavior orientation.” Id. at 368. Other studies
draw similar conclusions. See, e.g., Joe M. Braun, Exposures to
Environmental Toxicants and Attention Deficit Hyperactivity Disorder in
U.S. Children, 114 Environmental Health Perspectives 12 (2006) (“Braun

5

(2006)”) (estimating that 290,000 U.S. cases of ADHD are caused by lead
exposure).
Dr. Bithoney further mentions that those who are exposed to lead
face an increased risk of other health conditions, such as “cardiovascular
disease, hypertension, renal disease, and neurologic deficits.” (ECF No.
330-17, PageID.15015.)
Based on these sources, the Toxicological Profile, and an
informational website on the health effects of lead published by the
National Institute of Environmental Health Sciences,1 Dr. Bithoney
concludes that any amount of lead in the body can cause neurocognitive
harms. (See ECF No. 330-17, PageID.15014.)
B. Specific Causation Testimony
Dr. Bithoney then turns to the four individual bellwether Plaintiffs
to consider whether exposure to lead was the cause of their
neurocognitive injuries. According to Dr. Bithoney, each of the Plaintiffs’
neurocognitive injuries was likely caused by lead-poisoning.

See “Lead and Your Health,” National Institute of Environmental Health Sciences,
May 2021, available at
https://niehs.nih.gov/health/materials/lead_and_your_health_508.pdf.
1

6

While

COVID-19 prevented Dr. Bithoney from personally

examining each Plaintiff, he did conduct thorough interviews with each
of the Plaintiffs’ parents. (ECF No. 436, PageID.33888-33889.) In his
deposition, Dr. Bithoney explains that he took a “very extensive history”
during those interviews:
I got a social history, where did they live…when did they live
[there],

family

history,

genetic

history,

history

of

developmental difficulties in the family members, past
medical history, history of hospitalizations, what’s called a
review of systems, headaches, nausea, vomiting, blurred
vision, double vision, cough up blood, trouble hearing, trouble
seeing,

asthma,

difficult[y]

breathing,

gastrointestinal

disease, rashes, broken bones, evidence of child abuse. Just a
very extensive history.
Id. at PageID.33889. Dr. Bithoney also collected information about how
much water each Plaintiff ingested, when, and in what form. Id. Finally,
Dr. Bithoney questioned each parent about potential sources of lead
around the house. (Id. at PageID.34151.)

7

In addition to these interviews, Dr. Bithoney relied on the reports
of Dr. Mira Krishnan (Plaintiffs’ expert psychologist),2 medical and school
records for each Plaintiff, all lead exposure assessments taken of each
Plaintiff (both bone and blood tests), and several secondary sources on
the Flint Water Crisis. Dr. Bithoney also hired a graduate student to
conduct block-by-block “geomapping” of Plaintiffs’ neighborhoods, which
identified factors relevant to alternative sources of lead, such as the age
of housing and lead paint. (ECF No. 437, PageID.34273-34274.)
Dr. Bithoney ultimately concludes that the neurocognitive harms
Dr. Krishnan identified were caused by lead poisoning due to the
ingestion of Flint River water.
First, Dr. Bithoney relies on the bone lead tests conducted by Dr.
Aaron Specht to determine that each child was in fact exposed to
significant quantities of lead. (ECF No. 330-34, PageID.15510; ECF No.
330-18, PageID.15021; ECF No. 330-17, PageID.15006; ECF No. 330-34,
PageID.15035.) He explains that the negative blood lead tests taken for
each Plaintiff do not indicate otherwise, because the half-life of blood lead

The Court has summarized Dr. Krishnan’s findings in its recent opinion regarding
her testimony, see ECF No. 456.
2

8

in children is only approximately 10 days. (e.g., ECF No. 330-34,
PageID.15512.) Accordingly, blood lead tests taken long after an
exposure do not provide reliable information about the severity of that
exposure. Id. Moreover, the “thousands of micrograms of lead” revealed
to have been deposited in the Plaintiffs’ bones could not be explained
except by a significant exposure to lead. (ECF No. 436, PageID.33952.)
Dr. Bithoney estimates what peak blood lead levels could have
been by relying on the quantities of water each child likely consumed and
the likely lead content of that water. Three out of four Plaintiffs “drank
between 4 and 6 glasses of tap water per day,” while the other drank “3
glasses of tap water per day.” (ECF No. 330-34, PageID.15513.) A 2015
study by Virginia Tech University indicated that more than 40% of the
water in Flint had lead levels greater than 5 parts per billion (“ppb”), and
17% had lead levels greater than 15 ppb. (ECF No. 330-34,
PageID.15509.)3 Because the samples used in that study were not
representative and did not include any “high-risk homes,” it is likely that

The results of the sampling referred to by Dr. Bithoney are available online, here:
http://flintwaterstudy.org/information-for-flint-residents/results-for-citizen-testingfor-lead-300-kits/.
3

9

the true percentage of water above the 15 ppb mark was much higher
than reported. Id.
Dr. Bithoney explains how this data can be used to estimate the
actual blood lead peaks. Suppose that a toddler drinks 1 liter (4 glasses)
of water a day, with a lead content of 10 ppb. That would amount to
consuming 10g of lead every day. Children absorb between 50% and
100% of the lead they drink. (ECF No. 330-34, PageID.15514.) Someone
who drank 1 liter of water with a lead content of 10ppb for three months
would therefore have absorbed at least 450g of lead. The average toddler
has approximately 1.5 liters of blood in which to disperse that lead. Id.
Accordingly, three months of consuming water with a lead concentration
of 10 ppb would easily cause a toxic level of lead exposure, considering
that cognitive harms have been detected at blood lead concentrations as
low as 1 g/dl.
Accordingly, Dr. Bithoney concludes that each Plaintiff was
exposed to enough lead to cause the neurocognitive harms they
experienced. Dr. Bithoney testifies he used family histories to rule out
alternative, non-lead related causes of these harms and found no other
plausible explanations. (ECF No. 436, PageID.34085-34086.) Dr.
10

Bithoney also tried to rule out sources of lead exposure other than Flint’s
water. Because neither his graduate student’s report, nor his interviews
of the Plaintiffs’ parents yielded any plausible alternative explanations,
however, Dr. Bithoney concluded that Flint River water was by far the
most likely source of the lead exposure that caused Plaintiffs’ injuries.
(ECF No. 330-34, PageID.15517.)
C. Injury Testimony
In addition to his testimony regarding causation, Dr. Bithoney
draws two conclusions related to the Plaintiffs’ injuries. First, he explains
that “many children who are Pb [lead] intoxicated do well in early
childhood but then fall behind due to [the] so called ‘lag effect’.” (ECF No.
330-34,

PageID.15518)

(citing

Maureen

Dennis,

Developmental

Neuropsychology: a developmental approach (2d ed. 2019), at 17).
Accordingly, he opines that the Plaintiffs will likely fall further behind in
school as they are confronted with more complex academic challenges. Id.
Second, Dr. Bithoney notes that because of their exposure to lead,
Plaintiffs face a higher likelihood of contracting the serious medical
conditions associated with lead poisoning, such as cardiovascular

11

disease, hypertension, renal disease, and neurologic deficits. (ECF No.
330-34, PageID.15519.)
II.

Legal Standard

The admissibility of expert testimony is governed by Federal Rule
of Evidence 702, which sets forth three requirements: (1) the witness
must be qualified, (2) the testimony must be relevant, and (3) the
testimony must be reliable. Fed. R. Evid. 702; In re Scrap Metal Antitrust
Litig., 527 F.3d 517, 528–29 (6th Cir. 2008). As the Supreme Court
explained in Daubert, Rule 702 imposes a “gatekeeping” obligation on the
courts to ensure that scientific testimony “is not only relevant, but
reliable.” Daubert, 509 U.S. at 589; See also Kumho Tire Co., Ltd. v.
Carmichael, 526 U.S. 137, 147 (1999).
Daubert provides a non-exclusive list of factors courts may consider
when evaluating reliability: (1) whether the theory or technique at the
basis of the opinion is testable or has been tested, (2) whether it has been
published and subjected to peer review, (3) what the known error rates
are, and (4) whether the theory or technique is generally accepted.
Daubert, 509 U.S. at 593; see also In re Scrap Metal, 527 F.3d at 529
(listing same factors). Not every factor needs to be present in every
12

instance, and courts may adapt them as appropriate for the facts of an
individual case. Kumho 526 U.S. at 150.
“Rejection of expert testimony is the exception, rather than the
rule.” United States v. LaVictor, 848 F.3d 428, 442 (6th Cir. 2017)
(quoting In re Scrap Metal, 527 F.3d at 529–30)). Nevertheless, the
burden is on Plaintiffs to show by a “preponderance of proof” that the
proffered expert meets the standards of Rule 702 as interpreted by
Daubert. Pride v. BIC Corp., 218 F.3d 566, 578 (6th Cir. 2000) (quoting
Daubert, 509 U.S. at 592).
III. Analysis
VNA challenges every aspect of Dr. Bithoney’s testimony. First,
VNA argues that Dr. Bithoney’s general causation testimony is
unreliable because there is insufficient evidence of a causal relationship
between lead poisoning and any of the injuries suffered by Plaintiffs.
Second, it argues that Dr. Bithoney’s specific causation testimony is
unreliable because he (1) does not properly assess the Plaintiffs’ level of
exposure to lead, (2) has insufficient evidence for his conclusion that
Flint’s water was the source of Plaintiffs’ lead poisoning, and (3) does not
conduct a proper differential diagnosis. Third, VNA objects to all of Dr.
13

Bithoney’s injury testimony as prejudicial and unduly speculative.
Finally, VNA maintains that even if all of Dr. Bithoney’s testimony were
reliable, it would still be irrelevant under Rule 702.
Most of Dr. Bithoney’s complex testimony clearly meets the
standards of Rule 702 and Daubert. Indeed, Dr. Bithoney’s deposition
transcripts offer a powerful illustration of his expertise in the area of lead
poisoning. Even so, VNA raises valid concerns regarding some portions
of Dr. Bithoney’s testimony, and his testimony will be subject to the
limitations set forth below.
A. General Causation
VNA challenges all of Dr. Bithoney’s general causation testimony.
According to VNA, Dr. Bithoney has provided no evidence to suggest that
there is a causal link between lead poisoning and mood disorder or mild
neurocognitive disorder. (ECF No. 330-2, PageID.14202-14208.) While
VNA acknowledges that there is evidence of an association between lead
exposure and ADHD, it argues that mere association is insufficient to
support general causation testimony. Id. And VNA challenges Dr.
Bithoney’s testimony regarding physical health conditions on both
reliability and relevance grounds.
14

1. Lead and ADHD
Dr. Bithoney’s conclusion that lead exposure can cause ADHD is
reliable and well-supported. The Toxicological Report, which Dr.
Bithoney reviewed and relied on for his conclusions (ECF No. 436,
PageID.34038-34039), discusses fifteen studies all indicating “that risk
of childhood ADHD increases in association with increasing PbB [lead]
within the range of PbB <10g/dl.” Toxicological Profile, 172. An
additional study focusing on bone lead concentrations found that
“increasing bone lead was associated with…behaviors indicative of
attention deficit hyperactivity disorder assessed at age 7-15 years.”
Toxicological Profile, 175. In his reports, Dr. Bithoney highlights studies
by Lisa Chiodo and Joe Braun which draw similar conclusions.4 See
Chiodo (2004) and Braun (2006).
VNA relies on Nelson v. Tenn. Gas Pipeline, 243 F.3d 244, 253 (6th
Cir. 2001) for the proposition that “an association does not mean there is

VNA asserts that the Chiodo study “did not examine the relationship between lead
exposure and ADHD, but rather the relationship between lead exposure and teacherreported attention-related behaviors.” (ECF No. 330-2, PageID.14205.) That is at best
a misleading description of the Chiodo study, because the teachers involved were
“asked to complete the Barkley—DuPaul Attention Deficit Hyperactivity Disorder
(ADHD) Scale,” and their answers were used to compile “a total ADHD score.” Chiodo
(2006), at 362.
4

15

a cause-and-effect relationship.” This Court recently explained that
Nelson’s warning does not apply to evidence of association based on
epidemiological studies which account for confounding variables. In re
Flint Water Cases, No. 17-10164, 2021 WL 5631706 at *7-8 (E.D. Mich.
Dec. 1, 2021) (“Graziano”). That much is evident from the face of Nelson,
which continues by noting that “before any inferences are drawn about
causation, the possibility of other reasons for the association must be
examined.” Nelson, 243 F.3d at 253.
As is set forth above, many peer-reviewed studies have found a
sufficiently strong association between lead exposure and ADHD to infer
a causal link, and those studies carefully examined “the possibility of
other reasons for the association,” Nelson 243 F.3d at 253. For instance,
the Braun study accounted for the child’s (1) sex, (2) age, (3) race, (4)
socioeconomic status, (5) health insurance coverage, (6) preschool
attendance, (7) low birth weight and (8) ferritin (iron) levels and (9)
childhood admission to a neonatal intensive care unit as potential
covariates or confounding variables. See Braun (2006), at 1905. Nothing
forbids Dr. Bithoney from relying on such studies.

16

VNA also cites to Rochkind v. Stevenson, a recent Maryland Court
of Appeals decision which held that an expert witness’ testimony
regarding the causal link between lead exposure and ADHD was
unreliable. Rochkind v. Stevenson, 454 Md. 277 (2017). The witness in
Rochkind cited to an Environmental Protection Agency (“EPA”)
publication which found that there was “a causal relationship between
[lead] exposure and attention decrements, impulsivity, and hyperactivity
in children.” Id. at 288. Because the EPA publication did not explicitly
find a causal relationship between lead exposure and ADHD, the court
held that the expert did not have a “sufficient factual foundation” for her
conclusions. Id. at 290.
Rochkind is of limited persuasive value. The expert in Rochkind
explained that the symptoms discussed in the EPA study were the very
symptoms that constitute ADHD. The court’s refusal to permit the expert
to draw the reasonable inference that the EPA study supported a causal
link between ADHD and lead poisoning is difficult to reconcile with the
general rule that experts “need not testify to what is known to a certainty
but must only state an inference or assertion derived by the scientific
method.” Jahn v. Equine Serv.’s, PSC., 233 F.3d 382, 388 (6th Cir. 2000)
17

(cleaned up) (quoting Daubert, 509 U.S. at 592-93). But Rochkind is also
clearly distinguishable. The expert in that case relied on a single
publication which did not explicitly address ADHD, while Dr. Bithoney
relies on several studies which do explicitly identify a link between lead
exposure and ADHD. Accordingly, Dr. Bithoney’s opinions are far better
supported than those of the expert in Rochkind.
For these reasons, Dr. Bithoney’s conclusion that lead exposure can
cause ADHD meets the standards set forth by Rule 702 and Daubert.
2. Lead, Mood Disorder, and Mild Neurocognitive Disorder
VNA next argues that Dr. Bithoney has not provided sufficient
evidence to support the conclusion that lead poisoning can cause either
mood disorder or mild neurocognitive disorder. In response, Plaintiffs
argue that even though Dr. Bithoney did not identify any study which
concluded that lead exposure could cause those conditions, he properly
relied on the data in those studies to draw his own conclusions. (ECF No.
373, PageID.24640-24641.)
Both parties forge ahead without considering the actual substance
of Dr. Bithoney’s reports and testimony. Dr. Bithoney nowhere opines
that lead poisoning causes either mild neurocognitive disorder or mood
18

disorder. He does not draw that conclusion in his reports, and he does not
draw it in his deposition. The Court cannot evaluate the reliability of
opinions that an expert does not express.
The closest Dr. Bithoney comes to suggesting that mood disorder or
mild neurocognitive disorder can be caused by lead poisoning is when he
concludes that Plaintiffs’ “ingestion of Flint River water is a significant
cause and exacerbating factor resulting in [the] developmental,
behavioral, and cognitive deficits described above by Dr. Krishnan.” (See,
e.g., ECF No. 330-34, PageID.15517-15518.) It is arguably ambiguous
whether Dr. Bithoney’s reference to “deficits” was intended to refer to the
symptoms experienced by Plaintiffs or Dr. Krishnan’s formal diagnoses.
Plaintiffs’ counsel indicated at oral argument that Dr. Bithoney
would be testifying that lead poisoning can cause these diagnoses, not
merely the symptoms discussed by Dr. Krishnan. (ECF No. 425,
PageID.31771.) To the extent Dr. Bithoney intended to offer that opinion
at all, however, it is not supported by the evidence he cites. The
Toxicological Profile makes no mention of either “mood disorder” or “mild
neurocognitive disorder.” Nor does the Chiodo paper on the “behavioral
signature” of lead poisoning. Indeed, the Court has been unable to find
19

any mention of either diagnosis in any of the sources cited by Dr.
Bithoney.
To be sure, Dr. Bithoney discusses many of the characteristic
symptoms of mood disorder and mild neurocognitive disorder. Links
between several of those symptoms—such as difficulty regulating moods,
difficulty with academic tasks, decreases in intelligence, impulsivity, and
lack of focus—are well-established in the scientific literature. See
generally Toxicological Profile, 140-176. Dr. Bithoney may testify about
these findings. But Dr. Bithoney nowhere explains their relationship to
the diagnoses of mood disorder and mild neurocognitive disorder.
Accordingly, Dr. Bithoney may not provide general causation testimony
to the effect that these particular diagnoses are known to be caused by
lead poisoning. That is an opinion Dr. Bithoney neither states nor
supports.
3. Lead and Other Conditions
Dr. Bithoney also opines that lead poisoning can cause a number of
illnesses from which Plaintiffs do not currently suffer: cardiovascular
disease, hypertension, renal disease, and neurologic deficits. The Court
recently addressed the admissibility of nearly identical testimony.
20

Graziano, 2021 WL 5631706 at *7. For the reasons stated in Graziano,
testimony regarding conditions from which no Plaintiff currently suffers
is inadmissible because it is more prejudicial than probative. Id. (citing
United States v. Asher, 910 F.3d 854, 860 (6th Cir. 2018)).
As in Graziano, Plaintiffs may request reconsideration of this
decision if they obtain evidence that they are in fact likely to suffer from,
or already suffer from, any of the conditions discussed by Dr. Bithoney.
4. Any Amount of Lead is Harmful Testimony
Finally, Dr. Bithoney opines that any amount of lead can be
harmful. For the reasons set forth in Graziano, Dr. Bithoney may not
testify that any amount of lead is harmful. He may, however, testify that
there is no known toxicity threshold for lead and that lead has been
shown to cause neurocognitive harms at quantities as low as 1 g/dl of
blood lead or 1 ppm of dentine lead. See Graziano, 2021 WL 5631706 at
*3-4.
B. Specific Causation
According to VNA, all of Dr. Bithoney’s specific causation testimony
is also inadmissible. VNA organizes its objections according to the three
elements of specific causation in Michigan law: (1) a toxic exposure, (2)
21

at a sufficient level to cause injury, (3) that in fact caused injury. PowellMurphy v. Revitalizing Auto Comm’s Environ. Response Trust, 333 Mich.
App. 234, 250 (2020) (quoting Lowery v. Enbridge Energy Ltd., P’ship.,
500 Mich. 886, 1046 (2016) (Markman, C.J., concurring)). According to
VNA, Dr. Bithoney cannot establish any of these elements.
As an initial matter, the Court notes that the question at issue in
this motion is not whether Dr. Bithoney’s testimony can prove specific
causation under Michigan law. Two other experts—Dr.’s Specht and
Michaels—will also provide testimony on the first two elements of
specific causation. At summary judgment, the Court will consider
whether Plaintiffs have raised a material question of fact as to specific
causation. At this stage, the question is only whether Dr. Bithoney’s
opinions are sufficiently relevant and reliable to be admissible under
Federal Rule of Evidence 702 and Daubert.
1. Exposure
VNA first argues that Dr. Bithoney cannot reliably opine that
Plaintiffs were exposed to lead. According to VNA, Dr. Bithoney’s
opinions are unreliable because (1) they are based on unreliable bone lead
tests, and (2) they discount the negative blood lead tests. In addition,
22

VNA argues that even if Plaintiffs were exposed to lead, Dr. Bithoney
cannot establish that Flint’s water was the source of that exposure.
It is clear that Dr. Bithoney can reliably opine that the Plaintiffs
were exposed to lead. The Court has already addressed the reliability of
bone lead scans. In re Flint Water Cases, No. 17-10164, 2021 WL 5356295
(E.D. Mich., Nov. 17, 2021) (“Specht”). For the reasons set forth in that
opinion, bone lead scans are not so unreliable as to warrant exclusion
under Rule 702 and Daubert.
Dr. Bithoney also does not discount the importance of the blood lead
tests. As is explained above, he carefully explains why those results do
not show that there was no exposure to lead.
VNA’s third argument, that Dr. Bithoney does not sufficiently rule
out other sources of lead exposure, presents a more difficult question.
Crucially, there is no quantitative evidence of the lead levels in any of
the Plaintiffs’ homes during the relevant period. Dr. Bithoney reasons
that because (1) there was a city-wide problem with lead in Flint River
water and (2) careful investigation did not reveal any sources of lead that
could account for Plaintiffs’ high bone lead test results, Flint River water
was the most likely source of Plaintiffs’ exposure to lead.
23

VNA claims that the absence of quantitative lead measurements of
Plaintiffs’ water during the relevant time is dispositive, but that could
not be true. Plaintiffs in toxic torts cases will rarely have access to such
contemporaneous, quantitative measurements. After all, we do not
ordinarily measure our environment for toxins before there is any reason
to suspect that toxins may be present. While Dr. Bithoney’s conclusion
that Flint River water was the cause of Plaintiffs’ lead exposure is
admissible only if it is based on “good grounds,” Daubert, 509 U.S. at 590,
the law does not set the burden as high as VNA suggests.
The cases cited by VNA do not show otherwise. In Polaino v. Bayer
Corp., 122 F.Supp.2d 63 (D. Mass. 2000), an expert without any relevant
experience or training opined that a mixer contained chemicals that
caused the plaintiff’s reactive airway dysfunction syndrome. Id. at 68-70.
The expert had not seen the mixer, had not verified the presence of the
assertedly harmful chemicals, and had not measured the plaintiff’s
exposure to any chemicals. Id. His testimony was based purely on a
sequence of events that may well have been coincidental. Id.
The same was true in Bland v. Verizon Wireless (VAW) LLC., 2007
WL 5681791 (S.D. Ia. Aug. 9, 2007). The specific causation testimony
24

there was unreliable because there was no evidence that the environment
contained toxins or that the plaintiff was exposed to them. Id. at *10. The
experts in Bland and Polaino thus lacked objective evidence of the fact of
exposure, the degree of exposure, and the source of exposure.
That is clearly not the case here, where Dr. Specht’s bone lead scans
provide clear evidence of both the fact and the degree of Plaintiffs’
exposure to lead. As Dr. Bithoney puts it in his deposition: “all the
children had very high levels of lead, definitive levels of lead in their
bones, indicating ongoing exposure…you can’t argue with the fact that
tens of thousands of micrograms of lead are in this child’s bones.” (ECF
No. 436, PageID.33952.)
VNA nevertheless maintains that Dr. Bithoney did not adequately
rule out other sources of lead as the cause of Plaintiffs’ exposure. It
asserts that “all [Dr. Bithoney] did to investigate potential alternative
sources was to ask Plaintiffs’ parents during a telephone call whether
they knew of any alternative sources of exposure.” (ECF No. 330-2,
PageID.14215). But this is incorrect. Dr. Bithoney clearly did not just ask
the Plaintiffs’ parents whether they knew of any other sources of lead.
Instead, as he repeatedly explains during his deposition, he questioned
25

each parent at length about possible alternative sources of exposure,
using a process that is standard clinical practice:
[Flint River water] is the only source I was able to identify.
You know, I’ve done a lot of evaluation of the epidemiology of
lead in a family’s home and so we typically ask about lead
paint and soil and all that, the age of housing, we did all
that…I assure you that we did look for other sources in the
parental interview. Didn’t find that. Didn’t find anything in
the depositions. Didn’t find anything, any other source other
than the lead in the water.
ECF No. 436, PageID.34150-34151; See also ECF No. 436, PageID.34086
(followed standard clinical exposure assessment during parental
interview), PageID.34153-34154 (explaining other factors that would be
considered during an evaluation of lead in a family home). Dr. Bithoney
also hired a graduate student to analyze potential sources of lead in
Plaintiffs’ neighborhoods. (ECF No. 437, PageID.34273-34274.) Only
after considering all this evidence did Dr. Bithoney conclude that Flint’s
water was the most likely source of Plaintiffs’ lead exposure.

26

Daubert “does not require perfect methodology.” Best v. Lowe’s
Home Ctr.’s Inc., 563 F.3d 171, 181 (quoting Kumho Tire, 526 U.S. at
152). Instead, it requires only that an expert “employ in the courtroom
the same level of intellectual rigor that characterizes the practice of an
expert in the relevant field.” Id. Expert testimony is not limited to “what
is known to a certainty.” Daubert, 509 U.S. at 590; accord Jahn v. Equine
Serv’s, PSC, 233 F.3d 382, 388 (6th Cir. 2000). It is sufficient for an expert
to reasonably identify the most likely cause of an exposure. See, e.g.,
Jahn, 233 F.3d at 389-91 (expert veterinarian could testify to the
probable cause of a horse’s death, even if he did not know what the cause
was); Best, 563 F.3d at 182 (treating physician could testify to the “most
likely cause” of the injury).
Plaintiffs’ exposure to lead did not occur in a vacuum. While these
Plaintiffs lived in Flint, the city experienced a major crisis involving the
lead pollution of its drinking water. Not only did a substantial number of
water samples taken throughout the City of Flint show significant lead
content, during the time of the water crisis blood lead measurements
taken from babies in Flint were 700% more likely to be elevated than
measurements taken from babies in Detroit. Mona Hanna-Attisha,
27

Umbilical Cord Blood Lead Level Disparities between Flint and Detroit,
38 AM. J. PERINATOLOGY e26 (2020).
It is true, as VNA points out, that an expert may not rely exclusively
on evidence that an environment contained a toxin to conclude that a
particular plaintiff was exposed to that toxin. Nelson v. Tenn. Gas
Pipeline Co., 243 F.3d 244, 253 (6th Cir. 2001). As has already been noted,
however, Dr. Bithoney does not rely on circumstantial evidence to
conclude that the Plaintiffs were exposed to lead—that is shown by bone
lead measurements. Once there is a known exposure, an expert may
clearly consider evidence of environmental toxins to determine the most
likely source of that exposure. Neither Nelson nor any other case holds
otherwise.
VNA argues that Dr. Bithoney should have considered the fact that
Plaintiffs’ homes did not have lead water pipes. Dr. Bithoney did not do
so because he is “not an expert in plumbing or pipes.” (ECF No. 436,
PageID.33981.) However, he explains that the water pipes leading into
Plaintiffs’ homes need not have contained lead for the Plaintiffs to have
been lead poisoned by water consumption. After all, each Plaintiff
regularly drank water at places other than her home. (ECF No. 437,
28

PageID.34289-34290.) Absent any explanation sufficient to account for
the tens of thousands of micrograms of lead in Plaintiffs’ bones, Dr.
Bithoney concluded that Flint Water remained the most likely source of
lead exposure. That inference is not so unreasonable as to warrant the
exclusion of his testimony.
2. Sufficient Exposure to Cause Harm
VNA next argues that Dr. Bithoney’s conclusion that Plaintiffs were
exposed to sufficient lead to cause their injuries is unreliable. According
to VNA, Dr. Bithoney does not analyze the level of exposure and instead
relies only on his opinion that lead is harmful at any level.
VNA is incorrect. Dr. Bithoney relies on Dr. Specht’s bone lead
measurements, which quantify Plaintiffs’ exposures. As is set forth
above, Dr. Bithoney also explains how the available data can be used to
estimate peak blood lead levels. For instance, a toddler who consumed 4
glasses of Flint water for approximately 3 months would have absorbed
an estimated 450g of lead, which would have been dispersed over
approximately 1.5 liters (viz., 150 deciliters) of blood before being
deposited in the bones. (ECF No. 330-18, PageID.15025.) In light of the
fact that lead is known to cause neurocognitive harms at blood lead levels
29

of well below 10 g/dl, including decreases in IQ at blood lead levels as
low as 1g/dl, it is hardly a stretch to conclude that Plaintiffs, who all
consumed Flint River water for more than three months, were exposed
to enough lead to cause the neurocognitive harms they experienced. See
Toxicological Profile, at 140-176 (reviewing neurocognitive harms caused
by lead exposure); Schwartz (1994) (lead exposure can cause decrease in
IQ at 1g/dl or 1 ppm dentine lead).
Dr. Bithoney also reasons back from the bone lead measurements
(which revealed lead concentrations of between 5-10 g/g) to estimate the
peak blood lead level. In a study by Linda H. Nie, children with peak
blood lead measurements of over 30 g/dl were later found to have a bone
lead content of only 0.7 g/g. Linda H. Nie et. al., Blood lead levels and
cumulative

blood

lead

index

(CBLI)

as

predictors

of

late

neurodevelopment in lead poisoned children, 16 Biomarkers 6, 517-524
(2011). Given that each Plaintiffs’ bone lead measurement was
substantially higher, this may suggest that their peak blood lead levels
exceeded 30 g/dl.
To be sure, Dr. Bithoney’s estimates are just that: estimates. But it
is clear that Plaintiffs were exposed to enough lead to leave tens of
30

thousands of micrograms of it deposited in their bones. Given the
evidence that each of the symptoms Plaintiffs have experienced can be
caused by very low levels of lead exposure, Dr. Bithoney’s conclusion that
each Plaintiff was exposed to enough lead to cause those harms is a
reasonable inference from the available evidence.
Accordingly, Dr. Bithoney’s testimony regarding the second
element of specific causation is admissible.5 For the reasons set forth
above, however, this testimony is again limited to (1) ADHD and (2) the
neurocognitive symptoms discussed in Dr. Bithoney’s reports and
testimony. Because Dr. Bithoney has not explained what exposure (if
any) would be sufficient to cause mood disorder or mild neurocognitive
disorder, he may not testify that the Plaintiffs were exposed to enough
lead to cause those disorders.

VNA also argues that Dr. Bithoney should not rely on any studies which involve
blood lead measurements because he himself has disclaimed reliance on blood lead
measurements. This argument is completely without merit. Dr. Bithoney does not
argue that blood lead tests are unreliable, only that blood lead is quickly deposited
into the bones.
5

31

3. Cause in Fact
VNA next argues that Dr. Bithoney cannot reliably opine that the
Plaintiffs’ exposure to lead in fact caused their injuries.
The Sixth Circuit has explained that a specific causation witness
must first “rule in” exposure to a toxin as a possible cause of the alleged
injury, and then “reliably rule out the rejected causes,” i.e., causes other
than the toxic exposure. Pluck v. BP Oil Pipeline Co., 640 F.3d 671, 678
(6th Cir. 2011) (quoting Tamraz v. Lincoln Elec. Co., 620 F.3d 665, 674
(6th Cir. 2010)). This process is known as a “differential diagnosis.” Id.
It is evident that Dr. Bithoney “rule[d] in” lead exposure as a cause
of the Plaintiffs’ injuries. Id. The question is therefore whether Dr.
Bithoney adequately ruled out the alternatives. VNA claims that Dr.
Bithoney did not even consider any alternatives, but that is clearly
untrue. Dr. Bithoney conducted extensive interviews with each Plaintiff’s
parents to establish their medical, genetic, and social backgrounds. (ECF
No. 436, PageID.33888-33889). Those interviews clearly investigated
plausible alternative causes for the Plaintiffs’ injuries. (See id.
(considering genetic, social, and medical histories); ECF No. 330-17,
PageID.15003 (considering maternal drug and alcohol use). Dr. Bithoney
32

also reviewed previous lab tests and other medical records for possible
alternative causes. (E.g., ECF No. 330-19, PageID.15034). The Sixth
Circuit has held similar differential diagnoses to be sufficient. Hardyman
v. Norfolk & Western Railway Co., 243 F.3d 255, 260-262 (6th Cir. 2001)
(reversing district court’s exclusion of expert witness, finding differential
diagnosis sufficient where doctor questioned plaintiff about other
activities which could have caused symptoms and examined medical and
employment histories).
The only difficulty with Dr. Bithoney’s approach to the differential
diagnosis is that he does not spell it out in his reports. Thus, he testifies
that he took a genetic history, but not which genetic causes he ruled out;
he lists information related to maternal drug and alcohol use but does
not explain that he collected it to rule out fetal alcohol syndrome.
This problem with Dr. Bithoney’s reports does not render his
methodology unreliable. It is clear from his testimony that Dr. Bithoney
conducted a standard differential diagnosis. The purpose of the Court’s
gatekeeping function is to exclude “expertise that is fausse and science
that is junky.” Kumho, 526 U.S. at 159 (Scalia, J., concurring). That does
not include scrutinizing an expert’s reports for particular catchphrases.
33

What matters is not whether Dr. Bithoney used the words “differential
diagnosis” in his reports, but whether he conducted one. His reports and
deposition show that he did. To the extent that it is unclear whether Dr.
Bithoney excluded any particular cause, he can clarify his methods at
trial. See Thompson v. Doane Pet Care Co., 470 F.3d 1201, 1203 (6th Cir.
2006) (Rule 26 contemplates that experts “will supplement, elaborate
upon, [and] explain” the conclusions in their reports at trial).
VNA argues that even if Dr. Bithoney did conduct a differential
diagnosis, his analysis was insufficient because it did not consider every
plausible alternative cause. For instance, VNA claims that Dr. Bithoney
should have considered whether a 2011 spike in the lead content of Flint’s
water caused the Plaintiffs’ injuries. (ECF No. 330-2, PageID.14247.)
Setting aside the fact that such an investigation would be scientifically
impossible—bone lead measurements do not establish a date of
exposure—it is uncontroversial that specific causation experts need not
rule out every conceivable alternative cause of an injury. To the contrary,
“the fact that several possible causes might remain uneliminated only
goes to the accuracy of the conclusion, not to the soundness of the
methodology.” Jahn, 233 F.3d at 390 (6th Cir. 2000) (quoting Ambrosini
34

v. Labarraque, 101 F.3d 129, 140 (D.C. Cir. 1996)) (cleaned up); accord
In re: E.I. Du Pont de Nemours and Comp. C-8, No. 2:13-CV-170, 2016
WL 659112, at *30 (S.D. Oh. Feb. 17, 2016); Matthews v. Novartis Pharm.
Corp., No. 3:12-cv-314, 2013 WL 5780415, at *5 (S.D. Oh. Oct. 25, 2013)).
Accordingly, Dr. Bithoney’s differential diagnosis is admissible.
C. Injury
VNA next objects to Dr. Bithoney’s two injury-related opinions: that
all Plaintiffs face an increased risk of future medical complications, and
that their neurocognitive symptoms are likely to worsen as they grow
older. The first opinion is inadmissible because, as is set forth above,
evidence involving conditions from which the Plaintiffs do not suffer is
more prejudicial than probative. Dr. Bithoney’s prediction that the
Plaintiffs’ neurocognitive difficulties will increase over time is clearly
admissible, however.
Dr. Bithoney has treated lead intoxicated children just like these
Plaintiffs for over four decades. He therefore has an unparalleled
understanding of the difficulties they are likely to face as they grow older.
Medical experts are permitted to rely on such professional experience.
Dickenson v. Cardiac and Thoracic Surgery of Eastern Tenn., 388 F.3d
35

976, 982 (6th Cir. 2004); In re Heparin Prod. Liab. Litig., 803 F.Supp.2d.
712, 745 (N.D. Oh. 2011); Seifert v. Balink, 372 Wis.2d 525, 566 (2017)
(citing Dickenson, 388 F.3d at 980). And Dr. Bithoney provides additional
support for his view by citing to publications explaining that children
often “grow into” neurocognitive deficits that are not immediately visible
after a brain-injuring event.6 (ECF No. 330-17, PageID.15014.) His
testimony

regarding

the

likely

development

of

the

Plaintiffs’

neurocognitive symptoms is therefore sufficiently reliable to be
admissible.
D. Relevance
Finally, VNA argues that the entirety of Dr. Bithoney’s testimony
is irrelevant under Rule 702 because it does not “fit” Plaintiffs’ case. (ECF
No. 330-2, PageID.14250-14252.) VNA reasons that because Dr.
Bithoney’s testimony does not prove that VNA caused the Plaintiffs’
injuries, it is not relevant for Plaintiffs’ case against VNA. Id.
This argument is meritless. Evidence is relevant for purposes of
Rule 702 when there is a “factual issue in dispute that expert testimony

VNA objects that these studies do not specifically address lead poisoning, (ECF No.
330-2, PageID.14248), but Dr. Bithoney’s professional experience provides that link.
6

36

can clarify.” United States v. LaVictor, 848 F.3d 428, 442 (6th Cir. 2017)
(citing Lee v. Smith & Wesson Corp., 760 F.3d 523, 527-28 (6th Cir.
2014)). No individual expert is required to singlehandedly prove
Plaintiffs’ case against VNA. Dr. Bithoney’s testimony goes to key
elements of Plaintiffs’ toxic torts claim. Accordingly, it is plainly relevant.
IV.

Conclusion

For the reasons set forth above, VNA’s motion to exclude Dr.
Bithoney’s opinions and testimony is GRANTED IN PART and DENIED
IN PART.
IT IS SO ORDERED.
Dated: December 9, 2021
Ann Arbor, Michigan

s/Judith E. Levy
JUDITH E. LEVY
United States District Judge

CERTIFICATE OF SERVICE
The undersigned certifies that the foregoing document was served
upon counsel of record and any unrepresented parties via the Court’s
ECF System to their respective email or First Class U.S. mail addresses
disclosed on the Notice of Electronic Filing on December 9, 2021.
s/William Barkholz
WILLIAM BARKHOLZ
Case Manager

37