UNITED STATES DISTRICT COURTNORTHERN DISTRICT OF CALIFORNIAIN RE: ROUNDUP PRODUCTS
LIABILITY LITIGATIONMDL No. 2741

This document relates to:

ORDER GRANTING MOTION TO
EXCLUDE DR. LUOPING ZHANGAND GRANTING SUMMARYJUDGMENT TO MONSANTO

Bulone v. Monsanto Co., Case No. 20-cv03719-VC

Case No. 16-md-02741-VC

Re: Dkt. No. 18022

Monsanto’s motion to exclude the testimony of Dr. Luoping Zhang is granted. This orderassumes familiarity with the Court’s prior orders on general and specific causation and the Ninth
Circuit’s opinion in Hardeman. See generally, e.g., In re Roundup Products Liability Litigation,
390 F. Supp. 3d 1102 (N.D. Cal. 2018) (Pretrial Order No. 45, Dkt. No. 1596); In re Roundup
Products Liability Litigation, 358 F. Supp. 3d 956 (N.D. Cal. 2019) (Pretrial Order No. 85, Dkt.
No. 2799); Hardeman v. Monsanto Company, 997 F.3d 941 (9th Cir. 2021). It also assumes
familiarity with the record from the Daubert hearing on Zhang that took place on April 24, 2024.
See Hearing Tr. (Dkt. No. 18297).
Zhang’s presentation is based on a meta-analysis of the epidemiological literature that she
published in 2019. There are several issues with her opinion, each of which is an independent
ground for exclusion. First, Zhang’s meta-analysis is junk science. It has deep methodologicalproblems, not the least of which is that it doesn’t achieve its stated aim of examining only
“highly exposed” individuals. Instead, it examines an arbitrary selection of the available data.
Second, Zhang’s only engagement with the epidemiological literature is her meta-analysis, andher meta-analysis can’t substitute for a reliable general causation opinion. In other words, even if
the meta-analysis were somehow useful in the field of epidemiology, it still couldn’t reliably
serve as a litigation expert’s sole engagement with the epidemiological literature. Both of these
problems are exacerbated by the fact that Zhang struggled to answer basic questions about her
own paper, and the studies discussed in that paper. Nor can either problem be cured by intoningthat the paper was peer-reviewed and developed before an expert became personally involved inlitigation—those facts are relevant, but a court can’t wave junk science through the Daubert gate
simply because it survived some prepublication peer-review process. For each of those reasons,Zhang’s testimony must be excluded. And without Zhang, Bulone has no admissible generalcausation opinion, so Monsanto is entitled to summary judgment.
I
Dr. Zhang is a biochemist and a professor emeritus of toxicology at the University ofCalifornia, Berkeley. She has been designated to testify as a general causation expert in the
Bulone case. Zhang is Bulone’s sole expert on general causation.
Zhang’s presentation is different from those of past general causation experts in that the
only opinions she disclosed are those contained in two journal publications that she co-authored.
See Zhang Expert Report (Dkt. No. 18113-1) at 2 (stating that her “opinions in this matter, andthe bases for them, are set out in the following,” and citing two articles, without further
comment); see also Order Denying Motion to Strike Expert Report of Luoping Zhang, Ph.D.
(Dkt. No. 17743). In effect, these two publications are Zhang’s expert report. Only one of thesestudies, Zhang’s 2019 meta-analysis, grapples with the epidemiological evidence.1 That study isthe focus of Monsanto’s attack on Zhang’s presentation. Because an admissible expert opinion
on general causation is necessary to survive summary judgment, and because a complete generalcausation opinion must address the epidemiological evidence, Bulone’s case will stand or fall on

1

See Zhang et al., Exposure to Glyphosate-Based Herbicides and Risk for Non-Hodgkin
Lymphoma: A Meta-Analysis and Supporting Evidence, 781 Mutation Research 186 (2019)[“Zhang Meta-Analysis”] (Dkt. No. 18351-4).

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whether Zhang’s 2019 meta-analysis is an admissible treatment of the epidemiological evidence.
See Pretrial Order No. 45 at 13 (“As the parties acknowledge, epidemiology is central to thegeneral causation inquiry, and where such evidence exists, it must be addressed by the experts.”)(citing Norris v. Baxter Healthcare Corp., 397 F.3d 878, 882 (10th Cir. 2005)); see also id. at 6.
Zhang’s 2019 paper is a meta-analysis of six epidemiological studies of varying sizes,
methods, and quality: McDuffie (2001), Hardell (2002), De Roos (2003), Eriksson (2008), Orsi(2009), and Andreotti (2018). The paper’s approach is based on the “a priori hypothesis” that, if
glyphosate were carcinogenic, people who had been exposed to more glyphosate would be more
likely to show an increased risk of NHL. See Zhang Meta-Analysis § 2.3. Accordingly, theauthors purported to conduct the meta-analysis by isolating the data from the highest-exposuregroups, where available, across each of the studies and analyzing them using a fixed-effectstatistical model. However, not all of the epidemiological studies that Zhang analyzed broke out
their data into groups based on exposure levels. Some of the underlying studies only reported
their results on an ever-exposed/never-exposed basis. For those studies, the meta-analysis simply
used all of the data. See id. § 2.6.
The results of the meta-analysis are presented in the form of a “meta-risk ratio” of 1.41,
with a 95% confidence interval of 1.13–1.75. Id. § 3.1. Based on this top-line finding, as well assummary discussions of other kinds of animal studies and mechanistic studies, the meta-analysis
concludes that “[t]he overall evidence from human, animal, and mechanistic studies presented
here supports a compelling link between exposures to [glyphosate-based herbicides] andincreased risk for NHL.” Id. § 9.
Monsanto’s motion to exclude Zhang focused on an EPA critique of her meta-analysis
produced during the agency’s review of glyphosate’s registration under FIFRA. See Hsu Decl.
Ex. D, EPA Review (Dkt. No. 18022-5) at 8. The Daubert hearing brought some additional
issues to light, and the Court ordered further briefing. Bulone doesn’t dispute that the Court canconsider the issues raised at the hearing in ruling on Zhang, particularly given the supplemental
briefing. See Miller v. Baker Implement Co., 439 F.3d 407, 413 (8th Cir. 2006) (“A district3

court’s Daubert inquiry need not take any specific form, and its sua sponte consideration of theadmissibility of expert testimony is permissible so long as the court has an adequate record on
which to base its ruling.”) (citing Kirstein v. Parks Corp., 159 F.3d 1065, 1067 (7th Cir. 1998)).
II
In this litigation, the general causation question is “whether a reasonable jury could
conclude by a preponderance of the evidence that glyphosate can cause NHL at exposure levels
people realistically could have experienced.” Pretrial Order No. 45 at 2. Presenting an admissible
general causation opinion requires “offering independent and relatively comprehensive opinions
that the epidemiological and other evidence demonstrates glyphosate causes NHL in somepeople who are exposed to it.” Id. at 3. The admissibility of any opinion that Roundup is capableof causing NHL has always been a “very close question.” Id. at 1. Reliably offering such an
opinion requires serious engagement with the relevant literature: general causation experts must
be able to “assess whether a study is credible, to explain why they relied on one study more thananother, and to articulate how they reached their conclusion in the face of conflicting evidence.”
Pretrial Order No. 288 (Dkt. No. 17504) at 5; see also Pretrial Order No. 45 at 35.
A
The most fundamental problem with Zhang’s testimony is that her meta-analysis was notreliably performed. It has several methodological problems that, when taken together, make its
analysis of the epidemiological literature indefensible.
First, the meta-analysis was based on the hypothesis that, if glyphosate caused NHL, thenpeople with the highest levels of exposure would be most likely to get sick. Zhang and hercolleagues justified this hypothesis with reference to “the understanding that higher and longer
cumulative exposures are likely to yield higher risk estimates, given the nature of cancer
development.” Zhang Meta-Analysis § 2.2; see also Hearing Tr. at 122:3–15. They also argued
that data from high-exposure groups are less likely to be affected by confounders or to be diluted
by low-exposure data points. Zhang Meta-Analysis § 2.2. But the meta-analysis doesn’t grapple
with the fact that the Andreotti study, which it says is the highest-quality epidemiological study

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available, doesn’t show any kind of dose-response relationship between glyphosate exposure andNHL. See Pretrial Order No. 45 at 26 (discussing Andreotti, which reported risk ratios below 1
for every exposure quartile, with the highest risk ratio reported for the third-highest quartile);
Zhang Meta-Analysis, Table 2 (ranking the quality of the studies included in the meta-analysis
and listing Andreotti as the best study); see also Pretrial Order No. 45 at 40 (discussing theambiguous evidence regarding dose response issue).
Second, in applying its hypothesis, the meta-analysis ends up mixing different types ofstudies and different types of data in a way that ultimately seems hard to justify. Only half of thestudies that Zhang considered broke out their results according to the subjects’ exposure levels:
Eriksson, McDuffie, and Andreotti. See Hearing Tr. at 50:6–9. For the remaining three studies—
which reported their results on an ever-exposed/never-exposed basis—the meta-analysis simply
incorporated all of the studies’ data. So the meta-analysis used only a portion of the data fromthree of the studies, and the entirety of the data from the other studies. Id. at 59:9–12 (“[TheCourt]: So you took portions of the group of people studied in Eriksson and McDuffie andAndreotti and put them together with all of the people studied in the other three studies? A:
Yeah.”). One result of this uneven mixing of studies is that the meta-analysis, in effect,
artificially limited its use of data from Andreotti, the study Zhang said is the strongest and theone that showed no statistically significant association between glyphosate and NHL for any
level of exposure. This issue was noted in the EPA’s assessment of Zhang’s study. See EPA
Review at 8. Using a small portion of Andreotti’s data might be defensible if the meta-analysis
really took only a portion of the data from every study. But instead, the study methodologicallyde-emphasizes high-quality data that would tend to reduce the “meta-risk ratio,” while using thefull datasets from most of the lower-quality studies.2
Third, the studies that did stratify their results by exposure level used different exposure
2

The treatment of the Andreotti data is especially misleading given that the meta-analysis touts
itself as “the first meta-analysis to include the most recently updated Agricultural Health Study(AHS) cohort,” i.e., the Andreotti data. Zhang Meta-Analysis § 1.3; see also Hearing Tr. at
49:21–50:5.

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cut-offs and measured exposure differently. As a result, it’s likely that some people excluded by
the meta-analysis had as much or more exposure than people who were included. This makes themethod even more arbitrary. For example, the high-exposure category in McDuffie included
people who reported at least two exposure days per year. Hearing Tr. at 55:3–7. If that cutoff
were applied to the Andreotti data, it would probably capture many of the subjects from thatstudy’s third quartile (38.74–108.4 cumulative lifetime days of exposure) and even some fromthe second quartile (13.75–38.74 cumulative lifetime days of exposure).3 But these people were
uniformly excluded from Zhang’s analysis. Here again, the meta-analysis’s application of its
high-exposure hypothesis didn’t, in practice, result in the inclusion of only highly exposed
people. Instead, it resulted in the arbitrary exclusion of data from Andreotti and the overrepresentation of unadjusted data from the case-control studies.
That leads to the fourth point: the meta-analysis mixes results adjusted for the use ofother pesticides with unadjusted results. See Hearing Tr. at 80:8–81:17. Indeed, the metaanalysis’s selection criteria sometimes led Zhang to choose unadjusted data even when adjusted
data was available, which seems inexcusable. That is what Zhang did with the Eriksson study:
Eriksson reported unadjusted results stratified by exposure level, and Zhang included that data.
However, the study also reported adjusted results on an ever/never basis, and she ignored that
data. Id. at 91:2–24. (And then Zhang’s paper misleadingly states that five of the seven studies
reported data adjusted for other pesticides, which implies that it counted Eriksson as a study thatreported adjusted data. But the data from Eriksson that Zhang actually used in the primary metaanalysis was unadjusted. See Hearing Tr. at 94:21–95:7.) The inclusion of the unadjusted data
seems to have had a significant impact on the results, as evidenced by one of the paper’s
sensitivity analyses. That analysis substituted the Hohenadel study for the McDuffie study. The
Hohenadel study used the same subjects as the McDuffie study, but it adjusted for exposure to3

Gabriella Andreotti et al., Glyphosate Use and Cancer Incidence in the Agricultural HealthStudy, 110 Journal of the National Cancer Institute 1 (2018) (Dkt. No. 1136-1) at 3.

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malathion, an insecticide. See Hearing Tr. at 103:2–19; see also Zhang Meta-Analysis, Table 6,
Row: “Other”. (The relevant McDuffie data is unadjusted for other occupational exposures.)
With that substitution, Zhang’s “meta-risk ratio” became statistically insignificant. See id.
The issues with unadjusted data are especially important because they tend to undercut
the assumptions underlying Zhang’s entire method. Recall that part of the paper’s justification
for focusing on “high exposure” groups is that they are “less likely to be dominated by
confounding or other biases[.]” Zhang Meta-Analysis § 2.2. But, in this context, exposure toother pesticides is the major confounder, and people with high exposure to glyphosate (who tend
to be agricultural workers or landscapers) are likely to have more exposure to other pesticides,
not less. See Pretrial Order No. 45 at 24. That means that when Zhang isolated unadjusted, “highexposure” data from McDuffie and Eriksson, she may have increased the effect of confounders
on the meta-risk ratio. At the very least, it isn’t likely she reduced their effect.
The upshot of these four points is that the meta-analysis’s methods are impossible tojustify—and that becomes clear when one starts to drill down into the details. The stated purposeof the meta-analysis is to test the a priori hypothesis by examining what the totality of theepidemiological evidence shows about NHL incidence “following high cumulative GBH
exposure.” Zhang Meta-Analysis § 3.1. But the study doesn’t really do that. Instead, it slices anddices the available epidemiological evidence in a way that doesn’t actually isolate high-exposuredata. It takes all of the data from some studies that don’t report exposure levels; it excludes
subjects from Andreotti who were probably as highly exposed as subjects from McDuffie; and it
mixes whole datasets with partial ones, notably using only a small portion of the NHL cases
from the highest-quality study. Finally, the meta-analysis mixes adjusted and unadjusted data,
even choosing the latter in Eriksson even where adjusted data was available. See Hearing Tr. at
81:10–17.4 In short, the meta-analysis restricts itself to a more or less arbitrary subset of the
4This is not to suggest that it would never be appropriate for a meta-analysis to combine
adjusted numbers with unadjusted numbers. But to avoid using adjusted numbers for no apparent
reason is a different matter altogether. And when you combine that with the previous threeproblems discussed above, it becomes clear that Zhang’s meta-analysis is simply not an

7

epidemiological data points. And it does so in a way that seems likely to exacerbate, rather thanameliorate, problems with confounding. Even on its own terms, it is junk science.
B
There’s a second, independent problem. Even if Zhang’s paper could somehow be
considered a reliable meta-analysis, a reliable meta-analysis is not the same thing as a reliablegeneral causation opinion. In this respect, it matters that Zhang’s entire engagement with theepidemiological studies is based on her meta-analysis. Accordingly, the right way to think about
Zhang’s presentation is not just to ask whether it amounts to a reliable meta-analysis (although it
must at least be that). Instead, one also has to ask whether the meta-analysis is a reliableapproach to answering the question: “Does Roundup cause NHL in humans?”
To see why these are different questions, consider that the authors of the McDuffie,
Eriksson, or Orsi studies probably have fair claims that their case-control studies were reliably
conducted. Those studies were peer-reviewed and published, and they’ve no doubt been widely
cited in the scientific debates about glyphosate. But that doesn’t mean they would make foradmissible general causation opinions. Imagine, for example, that a plaintiff offered Dr.
McDuffie herself as their sole general causation expert. Imagine further that at the expert
disclosure deadline, McDuffie served her 2001 study, describing it as a statement of her“opinions in this matter, and the bases for them.” To survive a Daubert motion, it would not beenough for McDuffie to show that she had reliably conducted a case-control study. Instead, she’dhave to explain why her methods in that study (now functioning as an opinion on generalcausation) were a reliable way to decide, using epidemiological evidence, whether glyphosate
did or didn’t cause NHL.
The same is true here. Obviously, the difference between a meta-analysis and a casecontrol study is that the former purports to synthesize the results of multiple studies. But that
doesn’t mean that a meta-analysis can necessarily stand in for a holistic general causation

objective, reliable scientific undertaking.

8

opinion, especially where the meta-analysis is designed to examine only a subset of the available
data. Just like the McDuffie study could be useful to epidemiologists without being able toprove, by itself, that glyphosate causes cancer, a meta-analysis like Zhang’s might (if performed
reliably) offer a useful addition to the scientific literature without being able to prove anything
about general causation. Perhaps Zhang’s meta-analysis is best understood as a statisticalexperiment designed to see what can be learned by massaging the data in a certain way. As such,perhaps it could be useful to experts in some fashion. But here, the meta-analysis has beenoffered as Bulone’s only opinion about the epidemiological evidence and general causation. Thatmeans Zhang has opened the study up to the types of questions necessary to determine whether it
reliably analyzes that evidence—not just by the standards that govern epidemiological metaanalyses, but by the standards that govern general causation testimony in this litigation.
Zhang’s meta-analysis can’t meet those standards. First, and maybe most fundamentally,
the paper doesn’t seem to offer the necessary conclusion about general causation. Zhang
concludes that there is a “compelling link between exposures to [glyphosate-based herbicides]
and increased risk for NHL.” Zhang Meta-Analysis § 9. Similarly, the study’s key figure, the1.41 meta-risk ratio, is described as underscoring the fact that “exposure to GBHs is associatedwith an increased risk of NHL.” Id. § 6. But saying there is a “compelling link” or an“association” isn’t the same as saying that Roundup is capable of causing NHL in humans—
which is what a plaintiff’s general causation evidence must enable the jury to conclude.5 See
Pretrial Order No. 45 at 2; cf. also Pretrial Order. No. 263 (Dkt. No. 14432) at 2 (excluding a

5

The other paper that Zhang disclosed as a statement of her opinions, which deals with themechanistic evidence on glyphosate, also doesn’t offer an opinion about causation. It concludes:
The totality of evidence from mechanistic studies in human andanimal studies [sic] suggest that glyphosate and its formulations
possess several of the ten key characteristics of carcinogens. . . .
Overall . . . our findings our findings of strong evidence ofglyphosate’s ability to cause genotoxicity, epigenetic alterations,oxidative stress, chronic inflammation, and endocrine disruption,
as well as its demonstrated perturbation of the gut microbiota
outline several avenues implicated in lymphomagenesis.
Zhang Expert Report (Dkt. No. 18113-1) at 65.

9specific causation expert who concluded that “‘it is possible’ glyphosate contributed to” theplaintiff’s NHL).
Second, because the meta-analysis was published in 2019, Zhang can’t offer an up-todate account of the epidemiological evidence on glyphosate and NHL. In the roughly five years
since the meta-analysis was published, further epidemiological studies have come out. Zhang
admitted that if she conducted the meta-analysis today, she would incorporate several of them.
See Hearing Tr. at 104:5–105:21 (“Q: So if you were starting today to do the same study withyour a priori hypothesis, you would use Pahwa instead of McDuffie and De Roos 2003; correct?
. . . A: That’s correct.”); id. at 110:18–111:12 (Zhang admitting that if she were “doing the same
analysis with the same a priori hypothesis,” she would incorporate updated data from threestudies that post-dated her 2019 meta-analysis). It also seems like, if Zhang applied the same
methods today, the more recent data points would tend to reduce her “meta-risk ratio.” See id. at
109:9–23. At any rate, an expert testifying in 2024 couldn’t reliably opine that glyphosate iscarcinogenic if they only considered epidemiological evidence published before 2019.
Finally, the methodological problems described in the preceding section show not onlythat the paper is an unreliable meta-analysis but also that it’s unreliable as a standalone treatmentof the epidemiological evidence. If an expert offering a more conventional Bradford Hill–oriented general causation opinion arbitrarily limited the scope of the data they examined, elided
the distinction between adjusted and unadjusted data, and simply assumed the existence of adose-response relationship, their opinion would be inadmissible. Cf. Pretrial Order No. 288 at 2–
5 (excluding general causation opinion where, among other things, the expert “cherry-picked thefindings of the epidemiology studies, reporting only certain odds ratios—those most favorable tohis ultimate opinion,” and misstated whether the McDuffie and Eriksson studies were adjusted
for other pesticides). The same has to be true here.
To be clear, none of this is to suggest that a well-performed meta-analysis could never
independently support an expert opinion on causation. One could imagine a well-conductedepidemiological meta-analysis that yielded such a high risk-ratio that no further work would be10

necessary to conclude that a particular substance can cause an illness. It’s just that Zhang’s metaanalysis can’t support a finding that Roundup causes NHL, even assuming it makes some sort ofcontribution in the world of epidemiology.6
C
Zhang’s testimony, rather than addressing the problems with her opinion, made it evenless reliable. At the hearing, Zhang struggled to answer basic questions about her meta-analysis
or the handful of studies it incorporated. For example, she couldn’t remember the names of all
six studies that she analyzed. See id. at 48:8–51:17. She couldn’t remember important facts about
how the high-exposure groups were defined in each study. See id. at 51:20–52:20, 55:3–57:20.
She couldn’t remember whether key data points were adjusted or unadjusted. See id. at 93:25–
94:20. She couldn’t remember which studies were used in some of the sensitivity analyses, andshe was therefore unable to explain problems with them that were raised on cross-examination.
See id. at 100:11–102:21. This is clear enough from the transcript of the hearing; it’s even more
obvious from viewing the recording.
Bulone says that Zhang didn’t expect the hearing to get into issues that weren’t raised in
Monsanto’s motion, and that she may have been flustered by a change in the hearing format fromin-person to Zoom. Some allowances can be made for that. But, frankly, nothing can excuse
Zhang’s inability to answer basic and straightforward questions about her own paper and theepidemiological literature about which she is being offered as an expert. Zhang’s lack offamiliarity with her own opinion is itself a basis to exclude her testimony. See Pretrial Order No.
288 at 4 (excluding general causation opinion in part because the expert “was not able to discuss
his report, the literature, or his opinion without reading directly from his notes or being supplied
the answers by counsel through leading questions or displayed exhibits”).
To the extent that Zhang did address the substantive issues described above, her
It’s possible to characterize the problems discussed in this section as issues of “fit” rather thanreliability. See Daubert v. Merrell Dow Pharmaceuticals, Inc. (Daubert II), 43 F.3d 1311, 1315
(9th Cir. 1995); Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579, 597 (1993).
However they’re understood, they require exclusion.
6

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responses were inadequate. Generally speaking, Zhang defended the paper by saying that its
methods had been used in other meta-analyses, that its methodological choices were all madeclear in the paper, that certain limitations were a function of the small body of epidemiologicalevidence, and that the paper’s sensitivity analyses supported its headline “meta-risk ratio”
finding.7 But none of Zhang’s answers responded directly to the question of why, as a
substantive matter, these issues shouldn’t shake confidence in the paper’s methods. See, e.g.,
Hearing Tr. at 65:11–66:23; 71:7–72:8; 82:22–84:22. For example, the fact that the paper clearlystates its selection criteria doesn’t mean that applying them to slice up the epidemiological data
makes for a reliable analysis. In short, Zhang wasn’t able to defend her own study’s methods, letalone explain why it could serve as an independent analysis of the epidemiological evidence.
D
In his supplemental response, Bulone argues that Monsanto is asking the Court toimpermissibly substitute its judgment about the quality of the meta-analysis for the judgment of
the scientific community. He argues that the methods underlying the meta-analysis (including
most of practices discussed above, like mixing adjusted and unadjusted data) are common in
epidemiological meta-analyses. See Plaintiff’s Response to Monsanto’s Supplemental Brief (Dkt.
No. 18351) at 12–20; see also Zhang Declaration (Dkt. No. 18351-2). He says that studies
7

A word on the sensitivity analyses. Pointing to them was the closest that Zhang came to
substantively defending the study’s methods. But in crucial places, the sensitivity analyses end
up reproducing the problems with Zhang’s method rather than resolving them. Consider thesensitivity analysis that examined only the three studies that stratified data by exposure level. See
Zhang Meta-Analysis, Table 6, Row: “High level”. Necessarily, that analysis still mixes
unadjusted data from Eriksson and McDuffie with adjusted data from Andreotti, and it stillleaves out subjects from Andreotti that likely had as much exposure as subjects from McDuffie.
Or consider the analysis that purportedly examined only the studies with adjusted data. The
paper says that it considered four such studies. See id., Table 6, Row: “Adjusted”. But only threeof the studies—De Roos (2003), De Roos (2005), and Hardell—reported adjusted, stratified data.
The fourth study included must have been Eriksson, as Zhang acknowledged. See Hearing Tr. at
100:25–101:1. But that means that either the study authors used the unadjusted high-exposure
data from Eriksson in this meta-analysis (which would make it completely bogus) or they used
Eriksson’s ever/never data (which seems unlikely, because that would be inconsistent with thepaper’s method of selecting the high-exposure groups where available). Either way, thatsensitivity analysis doesn’t do what it claims to do. Zhang was unable to explain this discrepancy
and did not know which data was used in that sensitivity analysis. See id. at 100:11–102:19. The
paper itself doesn’t resolve the confusion, either. See Zhang Meta-Analysis, Table 6, n.7.

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employing such methods are frequently published in peer-reviewed journals, includingprestigious ones. See id. And he argues that Zhang’s meta-analysis has all the standard indicia of
reliability under Daubert: it was published in a peer-reviewed journal, it was produced
independently of litigation, Zhang has been invited to present the paper at various scientificsocieties, and the paper has been cited many times. See id. at 8–12.
These points can’t make the study’s glaring methodological flaws disappear. It’s true thatthe meta-analysis was published in a peer-reviewed journal and prepared before Zhang got
personally involved in any Roundup cases (although the paper seems so results-driven that one
could be forgiven for doubting that its authors were really thinking “independently” of thenationwide litigation). But while those facts are entitled to consideration, they don’t mean thatblind deference to Zhang is appropriate. There are a vast number of peer-reviewed journals out
there. Pre-publication editorial peer review, just by itself, is far from a guarantee of scientificreliability. See Valentine v. Pioneer Chlor Alkali Co., 921 F. Supp. 666, 674–76 (D. Nev. 1996)(distinguishing between “editorial peer review” and “true peer review,” and arguing that thelatter—which includes the scientific reception of an article after publication, efforts to replicate
its findings, etc.—is what’s really important under Daubert).8 Plus, part of the point ofcentralizing cases like these in an MDL is that the Court, over many years, can develop a fluency
in the relevant scientific literature. Where that fluency helps identify serious problems in anexpert opinion, it doesn’t make sense for the Court to ignore them.
Second, the other meta-analyses that Zhang cites, which also use an “a priori hypothesis”
to isolate high-exposure groups in epidemiological studies, don’t help her as much as she would
like. These studies may share some of the basic features of Zhang’s paper, but that isn’t enoughto save a study so riddled with problems. The other papers also aren’t methodologically8

See also Effie Chan, Note, The Brave New World of Daubert: True Peer Review, Editorial Peer
Review, and Scientific Validity, 70 N.Y.U. Law Review 100 (1995); Smith, Peer Review: A
Flawed Process at the Heart of Science and Journals, 99 Journal of the Royal Society of
Medicine 178 (2006) (arguing that there are many shortcomings of pre-publication peer review,
including that it is not a good system for catching errors, is prone to publication bias, and often
operates inconsistently).

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comparable to Zhang’s in important ways. For one thing, all of the cited meta-analyses examinedat least twice as many epidemiological studies as Zhang’s glyphosate meta-analysis, and often
many more. Perhaps if Zhang had a lot more studies to feed into her meta-analysis, she might
have a defensible claim to be roughly capturing “high-exposure” data points. As it is, heranalysis does no such thing.
Finally, Bulone’s arguments do nothing to address the problems with using Zhang’s
meta-analysis as a standalone analysis of the epidemiological evidence. One can’t assume thatpeer reviewers were vetting a study’s ability to play a certain role in an expert opinion, andthere’s no reason to think that was the case here. In short, simply intoning that a paper was peerreviewed and that it was (apparently) produced before the author was thinking about getting
involved in litigation isn’t enough to compensate for methodological problems as glaring as
those described here. And it certainly isn’t enough to show that Zhang’s paper can support a
reliable general causation opinion.
III
Monsanto filed a motion for summary judgment in connection with its motion to exclude
Dr. Braunstein, Bulone’s specific causation expert. See Dkt. No. 17598. That motion mentioned
the necessity of summary judgment in the absence of a specific causation expert. Id. at 9–10. The
absence of an admissible general causation opinion requires the same result, as Bulone’s counsel
conceded. Hearing Tr. at 87:14–25. Accordingly, summary judgment is granted for Monsanto on
the grounds that Bulone lacks any admissible evidence of general causation.

IT IS SO ORDERED.
Dated: June 20, 2024______________________________________
VINCE CHHABRIA
United States District Judge

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