1

Filed 11/19/13 Consumer Advocay Group v. Poolmaster CA1/4

NOT TO BE PUBLISHED IN OFFICIAL REPORTS

California Rules of Court, rule 8.1115(a), prohibits courts and parties from citing or relying on opinions not certified for 

publication or ordered published, except as specified by rule 8.1115(b). This opinion has not been certified for publication

or ordered published for purposes of rule 8.1115. 

IN THE COURT OF APPEAL OF THE STATE OF CALIFORNIA

FIRST APPELLATE DISTRICT

DIVISION FOUR

CONSUMER ADVOCACY GROUP, 

INC.,

Plaintiff and Appellant,

v.

POOLMASTER, INC., et al.,

Defendants and Respondents.

 A129796, A130903, A131227

 (Alameda County

 Super. Ct. No. RG07331650)

Proposition 65, the Safe Drinking Water and Toxic Enforcement Act of 1986, 

prohibits businesses from knowingly exposing anyone to a chemical “known to the state 

to cause cancer or reproductive toxicity” without a warning. (Health & Safety Code1

§ 25249.6.) A private party may bring an enforcement action against a business that 

violates Proposition 65. (§ 25249.7.)

Plaintiff Consumer Action Group sued various businesses2alleging their products 

(pool water test kits) contained the carcinogen ortho-Tolidine and failed to provide a 

warning label. After two years of litigation, defendants proved to the trial court’s 

satisfaction that their products contained, not ortho-Tolidine, but ortho-Tolidine 

dihydrochloride (the “salt form” of ortho-Tolidine) which is also a chemical “known to

 

1 All undesignated statutory references are to the Health and Safety Code.

2

The parties agree that the defendants remaining at the time of trial were Aqua 

Tri, Chem Lab Products, Inc., Home Depot U.S.A., Inc., Leslie’s Poolmart, Inc., Oreq 

Corporation, Poolmaster, Inc., Pool Water Products, and Valterra Products, Inc. 
2

the state to cause cancer.” The trial court entered judgment in defendants’ favor because 

plaintiff failed to prove that the carcinogen alleged in the complaint (ortho-Tolidine) was 

precisely the same carcinogen that is contained in defendants’ products (ortho-Tolidine 

dihydrochloride). 

We conclude the trial court erred in ruling, as a matter of law, that plaintiff’s 

failure to prove defendants’ products contained ortho-Tolidine was a material failure of 

proof of a Proposition 65 violation. We therefore reverse and remand for further 

proceedings. 

I. BACKGROUND

A. Proposition 65

In 1986, the voters adopted Proposition 65. Among other things, Proposition 65 

prohibits businesses from knowingly exposing consumers to chemicals known by the 

state to cause cancer or reproductive toxicity without a warning. (§ 25249.6.) If, 

however, the business can show the exposure to a carcinogen poses “no significant risk 

assuming lifetime exposure at the level in question,” it is exempt from the warning 

requirement. (§ 25249.10, subd. (c).)

The Governor is required to publish annually an updated list of chemicals that are 

known by the state to cause cancer or reproductive toxicity. (§ 25249.8, subd. (a).) 

These are referred to as “listed chemicals.” (See, e.g., Cal. Code Regs., tit. 27, § 25903 

(b)(2)(A).) Two chemicals that appear on the Governor’s Proposition 65 list are at issue 

here: The first is “3,3’-Dimethylbenzidine (ortho-Tolidine),” which has a Chemical 

Abstract Service (CAS) number of 119-93-7 and was listed in 1988; the second is “3,3-

Dimethylbenzidine dihydrochloride” (ortho-Tolidine dihydrochloride), which has a CAS 

number of 612-82-8 and was listed in 1992. (Cal. Code Regs., tit.27, § 27001.) Ortho-
3

Tolidine dihydrochloride is sometimes referred to as the “salt form” or “dihydrochloride 

form” of ortho-Tolidine.

3

 

A private party may bring an enforcement action against a person who violates 

Proposition 65, subject to certain procedural requirements. (§ 25249.7.) One such 

requirement is that, more than 60 days prior to the filing of an action, the party must send 

a notice of the alleged violation to “the Attorney General and the district attorney, city 

attorney, or prosecutor in whose jurisdiction the violation is alleged to have occurred, and 

to the alleged violator.” (§ 25249.7, subd. (d)(1).) The notice must include, among other 

things: (1) the name, address and telephone number of the person or entity giving notice, 

(2) the name of the alleged violator, (3) the approximate time period during which the 

violation is alleged to have occurred, and (4) “the name of each listed chemical involved 

in the alleged violation.” (Cal. Code Regs., tit. 27, § 25903, subd. (b)(2)(A).) The 

regulation further provides that it “shall not be interpreted to require more than 

reasonably clear information, expressed in terms of common usage and understanding, on 

each of the indicated topics.” (Cal. Code Regs., tit. 27, § 25903, subd. (b)(2).) 

The prelitigation notice is designed to accomplish two things: (1) to give the 

public prosecutor the means to assess whether to intervene on the public’s behalf, and 

(2) to give the target of the notice the opportunity to avoid litigation by settling with the 

plaintiff or by curing any violation. (Consumer Advocacy Group, Inc. v. Kintetsu 

Enterprises of America (2007) 150 Cal.App.4th 953, 963–964 (Kintetsu).)

B. Procedural History

Plaintiff filed two complaints. The first was filed in June 2007, against Oreq 

Corporation, Poolmaster, Inc., Home Depot U.S.A., Inc., and other defendants. The 

second was filed in March 2008 against Aqua Tri, Pool Water Products, Leslie’s 

 

3

 We shall on occasion refer to ortho-Tolidine as OTO or orthotolidine, and to 

ortho-Tolidine dihydrochloride as OTO dihydrochloride or orthotolidine dihydrochloride. 

Ortho-Tolidine is sometimes identified in the scientific literature as “o-tolidine.” 
4

Poolmart, Inc., Valterra Products, Inc., Chem Lab Products and other defendants; it also 

named Oreq Corporation again. The two actions were consolidated. 

For purposes of this appeal, the complaints were essentially identical in alleging 

that defendants manufacture or distribute a consumer product designed to test the 

concentration of chlorine in swimming pool, spa and potable water, and that these 

products contain, and expose users to 3,3’ Dimethylbenzidine (ortho-Tolidine), a 

carcinogen. Plaintiff alleged that ortho-Tolidine “first appeared on the Governor’s 

Proposition 65 list of Chemicals known to cause cancer” on January 1, 1988, and thus 

became subject to Proposition 65 warning requirements 20 months thereafter, pursuant to 

section 25249.9, subdivision (a). 

Plaintiff also alleged that the requisite prelitigation notices were given. With 

respect to the first complaint, the notices were sent on December 12, 2006. The second 

complaint was preceded by notices sent out on various dates, but it appears that each 

defendant was sent two notices, one on June 28, 2007 and another on November 9, 2007.4 

The record contains three of the notices: a December 2006 notice and two November 

2007 notices. The 2006 and 2007 notices are different with respect to the identification 

of the chemicals in question. The 2006 notice states that “[t]he chemical known to the 

State to cause cancer relevant to this Notice is 3,3-Dimethylbenzidine (ortho-Tolidine).” 

The 2007 notices state that the relevant chemicals are “3,3’-Dimethylbenzidine (orthoTolidine) and 3,3’-Dimethylbenzidine dihydrochloride.” 

Defendants’ answers and the parties’ early case management statements are not 

included in the record. It appears, however, that at some point, “based on discovery,” 

defendants took the position that their products did not contain orthotolodine, but rather, 

orthotolidine dihydrochloride. Defendants characterized this as a “different chemical” 

 

4

The first notice of the second complaint was sent to Oreq Corporation on 

October 2, 2007.
5

which, they argued, was not included in the prelitigation notices or the complaint. 

Plaintiff contended that “there is no discernable difference between [ortho-Tolidine] and 

ortho-Tolidine dihydrochloride . . . [because ortho-Tolidine] is just the free base form of 

ortho-Tolidine dihydrochloride and, conversely, ortho-Tolidine dihydrochloride is merely 

the salt form of . . . [ortho-Tolidine].”5

Defendants thereafter requested a bifurcated trial on the issue of “what’s in the 

bottle,” i.e., what is the chemical content of defendants’ products.6 The court ordered a 

“Phase I bifurcated trial” on the “core issue” of whether or not defendants’ products

“contain the chemical 3,3’ Dimethylbenzidine (ortho-Tolidine), CAS No. 119-93-7, first 

appearing on the Proposition 65 List on January 1, 1988.” Although plaintiff has not 

provided to us the portions of the record that explain how the “core issue” came to be 

formulated, the record shows that plaintiff objected to this narrow articulation of the 

issue, arguing that “[d]efendants seek to obstruct the purpose and intent of Proposition 65 

. . . by asking the court to construe the notice requirements in an inappropriate and 

artificially strict manner.” In its pre-trial brief, plaintiff contended that, because 

Proposition 65 is a remedial statute to be construed broadly in favor of its goal of public 

protection, the law did not require plaintiff to identify separately the salt 

(dihydrochloride) form of OTO in addition to OTO in its notice and complaint because 

OTO in one form or another exists in defendants’ products, and both are listed as 

 

5

 In a discovery response to Pentair Water Pools & Spa’s request for documents, 

plaintiff went further, stating “[a]lthough [plaintiff] maintains that there is no discernible 

difference between the two Listed Chemicals, both of which are insidious carcinogens, 

neither [plaintiff’s] complaint nor the 60 Day Notice of Violation upon which it is 

premised allege that [Pentair’s] Product contains [orthotolidine dihydrochloride]. 

[Plaintiff], therefore, has not premised its case on this chemical. It is not material, in 

dispute and not applicable to this case.” Pentair Water Pools & Spa was not a defendant 

in the Phase One trial and defendants objected to the introduction of evidence relating to 

Pentair’s products. 

6

 Defendants’ motion for a bifurcated trial is not in the record; we infer from the 

parties’ December 2008 joint case management statement that such a motion was filed.
6

carcinogenic. According to plaintiff, the question should be whether the notices and 

complaints provided adequate information from which defendants could assess the nature 

of the alleged violation. 

Defendants, on the other hand, focused narrowly on the regulatory requirement

that the prelitigation notice must identify “ ‘the name of each listed chemical involved in 

the alleged violation.’ [Citing] Cal. Code of Regulations . . . Title 27, § 25903(b)(2)(A)4 

(emphasis added)[.]” Defendants argued that both the 60-day notices and the complaints

must “clearly identify the chemical in the consumer product that allegedly triggered a 

warning obligation,” and “[p]ursuant to Prop 65 enforcement requirements, only . . . this 

specific chemical [is] the subject of the lawsuits.” Therefore, defendants concluded, 

plaintiff’s actions must be dismissed because it cannot prove that defendants’ products 

contain the named chemical OTO, rather than OTO dihydrochloride. 

After a two-day trial, the court ruled in defendants’ favor. The court rejected out 

of hand plaintiff’s foundational argument that the statute is a remedial one which must be 

construed broadly. “However laudable serving the policy behind Proposition 65 may 

be,” the court wrote, “it does not alter the burden of proof on the core issue.” After 

reviewing the evidence presented at trial, the court found that plaintiff had failed to prove 

that defendants’ products contained orthotolidine, and that this was a “material failure of 

proof on the part of Plaintiff whereas Defendants presented a more persuasive and 

coherent body of the evidence to the contrary [showing the presence of OTO 

dihydrochloride].” (Emphasis added.) 

Plaintiff appealed from the judgment entered in favor of defendants.7 

 

7

 In these consolidated appeals, plaintiff challenges not only the trial court’s 

finding on the merits, but also the post-trial award of expert witness fees pursuant to 

Code of Civil Procedure section 998, which was based on plaintiff’s failure to accept 

defendants’ pretrial offer to compromise. In their appeal, defendants contend the trial 

court erred in denying their post-trial challenge to the certificate of merit plaintiff 

submitted before filing this action. (§ 25249.7, subd. (h)(2).) Our reversal of the 

underlying judgment renders moot the parties’ appeals on these issues.
7

C. Standard of Review

The selection of the correct standard of review on appeal depends upon the 

question or questions before the court. Defendants argue that “the issue dispositive of 

[plaintiff’s] appeal . . . is whether substantial evidence supports the superior court’s 

finding that the products contained no orthotolidine.” Plaintiff argues there are two 

questions on appeal: (1) whether, in the Proposition 65 context, the term “chemical” 

should be construed broadly to include different iterations of a chemical compound where 

the chemical’s core carcinogenic structure exists in both iterations, and (2) whether the 

trial court erred in determining that plaintiff had not proven that defendants’ products 

contained the carcinogen orthotolidine. 

Stated more generically, the first question posed is whether the trial court erred in 

concluding that because plaintiff failed to prove defendants’ products contained 

orthotolidine, as alleged in the complaint, rather than orthotolidine dihydrochloride as 

proven by defendants, there was a “material failure of proof” warranting dismissal. We 

agree that this question is central to the appeal, and is an issue of law to be reviewed de 

novo. (California Teachers Assn. v. San Diego Community College Dist. (1981) 28 

Cal.3d 692, 699.) 

II. DISCUSSION

A. Defendants’ Contention

Defendants’ contention concerning the requirements for pleading and proof of a 

Proposition 65 violation is brief; we quote it here: “Prelitigation notices and complaints 

must identify exactly the chemical in the consumer product that allegedly triggered a

warning obligation. The Proposition 65 regulations require ‘the name of each listed 

chemical involved in the alleged violation.’ (Cal. Code Regs., tit. 27, § 25903 subd. 

(b)(2)(A)4, emphasis added; see [Kintetsu, supra,] 150 Cal.App.4th 953, 973[).] . . . The 

complaints on which [plaintiff] went to trial were based on [two different] prelitigation 

notices, but charged only orthotolidine as a chemical present in the products without 
8

warning. . . . [¶] [Plaintiff] failed to make a prima facie showing that respondents’ 

products contain orthotolidine.” 

Defendants’ argument conflates two different questions, which are: (1) the 

adequacy of a prelitigation notice, and (2) the requirements for pleading and proving a 

prima facie case under Section 25249.6. We examine each, in turn.

As we have described, the Proposition 65 regulations require a private plaintiff to 

serve a prelitigation notice, and in that notice to identify “[t]he name of each listed 

chemical involved in the alleged violation.” (Cal. Code Regs., tit. 27, § 25903, subd.

(b)(2)(A)4.) The identification of each chemical as to which the plaintiff intends to sue is 

necessary to serve the purposes of the prelitigation notice, which are: (1) to give the 

public prosecutor the means to assess whether to intervene on the public’s behalf, and (2) 

to give the target of the notice the opportunity to avoid litigation by settling with the 

plaintiff or by curing any violation. (Kintetsu, supra, 150 Cal.App.4th at pp. 963–964.) 

Thus, for example, in Kintetsu some of the pre-litigation notices alleged exposure to 

smokeless tobacco and cigars but did not differentiate the chemicals in each product, and 

the record did not show whether the chemicals were the same in both, as argued by the 

plaintiff. Under the circumstances, the court ruled the plaintiff “may proceed only with 

respect to those chemicals contained in the notice [but to] the extent they are the same, no 

need exists to list them twice.” (Id. at p. 972.) Similarly, a private plaintiff would not be 

permitted to identify one chemical in the prelitigation notice, such as toluene, and then to 

sue upon an entirely different or additional chemical, such as dioxin. “Because of their 

different properties, different chemicals raise very different issues in determining whether 

there is a violation.” (Office of Environmental Health Hazard Assessment (OEHHA), 

Final Statement of Reasons: Adopt Section 12903, Notices of Violation, Title 22, 

Division 2, California Code of Regulations [now at tit. 27, § 25903], available online at 

<http://oehha.ca.gov/prop65/law/pdf_zip/903FSR.pdf.> at p. 9. [as of Nov. 1, 2013].)

Defendants, however, take these tenets even further. They argue that 

“[p]relitigation notices and complaints must identify exactly the chemical . . . that 

allegedly triggered a warning obligation.” (Emphasis added.) But the requirement of 
9

exactitude is not found in the regulation or in any authority construing it. What the 

regulation does state is that the notice “shall provide adequate information from which to 

allow the recipient to assess the nature of the alleged violation,” and that its requirements 

“shall not be interpreted to require more than reasonably clear information, expressed in 

terms of common usage and understanding, on each of the indicated topics.” (Cal. Code 

Regs., tit. 27, § 25903, subd. (b)(2).) 

Fortunately, we need not engage in calibrating the level of precision required to 

meet the notice requirement because that is not the question before us. Defendants do not 

claim that the identification of orthotolidine in the notices failed to provide adequate 

information to allow defendants and the attorney general to “assess the nature of the 

alleged violation.” (Cal. Code Regs., tit. 27, § 25903, subd. (b)(2).) Nor do they contend 

that the notice was so deficient that “[n]either settlement nor an official investigation 

[was] likely to result.”8(Yeroushalmi v. Miramar Sheraton (2001) 88 Cal.App.4th 738, 

750.) Defendants’ contention, rather, is that plaintiff did not prove exactly what it pled—

that defendants’ products contain orthotolidine—and therefore their case fails as a matter 

of law. In so arguing, defendants simply import into pleading and proof requirements 

their own strict interpretation of what is required for the prelitigation notice. We disagree 

with this analysis. There is no authority for the proposition that prelitigation notice 

requirements also control the principles of pleading and proof in a Proposition 65 case, 

and, as we explain, we see no reason in such actions to deviate from the general 

principles of pleading and proof applicable to civil cases. 

B. Prima Facie Evidence of Proposition 65 Violation

We start with basic principles pertinent to Proposition 65. 

It is well-established that the purpose and intent of Proposition 65 is to protect the 

public from toxic contamination, and it must be construed broadly to accomplish that 

purpose. (People ex rel. Lungren v. Superior Court (1996) 14 Cal.4th 294, 314–315 

 

8

 We observe that, of the defendants in this appeal, only Home Depot and 

Poolmaster, Inc. did not receive the second set of notices that identified both 

orthotolidine and orthotolidine dihydrochloride. 
10

(Lungren) [“[W]e consider Proposition 65 to be a remedial statute intended to protect the 

public from, among other things, toxic contamination of its drinking water. We construe 

the statute broadly to accomplish that protective purpose.”].) Consequently, our courts 

have uniformly applied a liberal construction when assessing various issues arising under 

Proposition 65. (See, e.g., California Chamber of Commerce v. Brown (2011) 196 

Cal.App.4th 233 [methods for listing chemicals]; Consumer Cause, Inc. v. SmileCare 

(2001) 91 Cal.App.4th 454, 461–462 [exposure to product containing reproductive 

toxin]; As You Sow v. Conbraco Industries (2005) 135 Cal.App.4th 431, 451 (As You 

Sow) [construction of term “ ‘specific medium’ ” in regulation].) 

“Proposition 65 adopts a dual-pronged approach based on protection and 

information. The Act accomplishes these twin objectives by prohibiting any person in the 

course of doing business from knowingly discharging or releasing a listed toxic chemical 

into a source of drinking water (discharge provision) or from knowingly and intentionally 

exposing any individual to such chemicals without first providing a warning (warning 

requirement).” (As You Sow, supra,135 Cal.App.4th at p. 437.) Additionally, the 

statutory scheme “establishes a series of shifting burdens.” (Mateel Environmental 

Justice Foundation v. Edmund A. Gray Co. (2003) 115 Cal.App.4th 8, 18 (Mateel).) 

Thus, in an action to enforce the discharge provision (section 25249.5), “[i]n the first 

instance, a plaintiff must show that a discharge has occurred. Once this burden has been 

met, the defendant may show, inter alia, that the amount of the discharge is not 

significant [pursuant to section 25249.9].” (See ibid.; As You Sow, supra, 135 

Cal.App.4th at p. 437.) By parity of reasoning, in an action to enforce the warning 

requirement (section 25249.6), a plaintiff must show, in the first instance, that a 

defendant’s product exposed individuals to a listed chemical without a warning. Once 

that burden is met, a defendant may prove the warning is not required by showing, inter 

alia, that the level of exposure poses no significant risk, pursuant to section 25249.10. 

We find nothing in the provisions of Proposition 65 or its regulations that requires 

or even suggests that a Proposition 65 claim fails as a matter of law if the chemical 

identified in the complaint is not “exactly” the same chemical contained in defendants’ 
11

products. Nor has our research unearthed any case construing section 25249.5 et seq. 

that imposes any particularized proof standards. We therefore look to the general 

standards of pleading and proof. 

It is a fundamental principle of civil jurisprudence that “[n]o variance between the 

allegation in a pleading and the proof is to be deemed material, unless it has actually 

misled the adverse party to his prejudice in maintaining his action or defense upon the 

merits.” (Code Civ. Proc., § 469; Thrifty-Tel, Inc. v. Bezenek (1996) 46 Cal.App.4th 

1559, 1572.) Thus, the correct question is not whether plaintiff can prove defendants’ 

products contain the precise carcinogen alleged in the complaint, but whether plaintiff 

can prove that defendants’ products exposed individuals to a listed chemical without a 

warning, and did not mislead the defendants to their prejudice as to the nature of their 

claim. Defendants offer no basis for applying a more exacting standard in a Proposition 

65 case, and we can divine no policy reason to set a higher bar. To the contrary, a more 

rigid interpretation of the proof requirements for a Proposition 65 action could well 

frustrate its remedial purpose—protection of the public from toxins—by blocking an 

enforcement action based on a technical dispute as to the precise form of a chemical 

where the difference is not relevant for purposes of a prima facie violation of Proposition 

65. “A court should not adopt a statutory construction that will lead to results contrary to 

the Legislature’s apparent purpose.’ [Citation.]” (Lungren, supra, 14 Cal.4th at p. 305.)

The cases construing Proposition 65 support this commonsense approach. Our 

courts regularly interpret the provisions of the statute and the regulations reasonably, and 

reject attempts by both enforcers and businesses to impose higher proof standards. (See, 

e.g., Mateel, supra, 115 Cal.App.4th at pp. 21–24 [court rejected defendant’s attempt to 

hold a plaintiff to an inappropriate standard of testing for lead]; Baxter Healthcare Corp. 

v. Denton (2004) 120 Cal.App.4th 333, 364–368 (Baxter) [court rejected attempt by 

OEHHA to require alleged violator to prove affirmative defense by clear and convincing 

evidence]; Exxon Mobil Corp. v. Office of Environmental Health Hazard Assessment 

(2009) 169 Cal.App.4th 1264, 1278–1285 [court rejected an attempt by potential 

violators to remove a chemical from the list by applying an overly strict interpretation of 
12

the regulations governing listing]; DiPirro v. Bondo Corp. (2007) 153 Cal.App.4th 150, 

190–192 [court upheld defense where defendant proved no observable effect of chemical 

on 75 to 85 percent of the population, and rejected as “extreme” plaintiff’s proffered 

standard of no effect on “ ‘any consumer’ ”].)

Defendants also assert, without citation to authority, that because plaintiff did not

seek leave to amend the complaints after learning that defendants claimed their products 

contain OTO dihydrochloride (as opposed to OTO), the “issue dispositive of [plaintiff’s] 

appeal” is whether substantial evidence supports the trial court’s finding that plaintiff 

failed to prove that defendants’ products contain OTO. This argument merely restates in 

different procedural terms the trial court’s formulation of the “core issue” to be tried—

whether defendants’ products contain orthotolidine, vel non. But the question raised by 

plaintiffs below and on appeal is whether that formulation is erroneous because it rests on 

too rigid an interpretation of the statute for purposes of proving a Proposition 65 

violation. Rather than addressing that question, defendants assert, without more, that a 

failure to amend means plaintiff must prove exactly what it pled. As has been discussed, 

this is not a correct statement of the law.9 

In sum, we reject defendants’ contention and the trial court’s requirement that a 

Proposition 65 plaintiff must prove that the chemical alleged in the complaint is the exact

chemical in defendants’ products. Rather, a plaintiff can meet its burden if the evidence 

as a whole establishes a violation of the statute, unless there is a material variance 

 

9

 Defendants also cite Consumer Cause, Inc. v. Weider Nutrition Internat., Inc. 

(2001) 92 Cal.App.4th 363 (Weider) for the proposition that “combining a product with 

another chemical [which] may produce a Proposition 65 listed chemical does not require 

a Proposition 65 warning on the product.” That holding is misstated. Weider actually 

holds that a product which itself does not contain a carcinogen does not require a warning 

if it becomes a carcinogen (testosterone) when ingested. (Id. at pp. 369–370.) Weider

has no bearing on the issues before us. 
13

between the pleading and the proof.10 (Code Civ. Proc., § 469.) This standard serves 

both due process requirements and the protective goals of Proposition 65. 

We turn now to a review of the evidence to determine whether plaintiff has 

satisfied this burden.

C. The Evidence at Trial11

As we have stated, the trial court set for hearing the narrow issue of “whether or 

not [defendants’] products contain the chemical [ortho-Tolidine].” Consequently, the 

parties’ evidence related only to that scientific question. 

1. Matters of Agreement 

We begin by summarizing the substantial areas of agreement between the parties.

Defendants’ products are designed to measure the chlorine levels in swimming 

pools and spas. Their manner of use was described by the vice president and a founder of 

one of the defendants: “The vial for testing the chlorine content of pool or spa water is 

filled [with that water] to a level that’s marked on the vial. Then five drops of . . . what 

we commonly called the OTO solution are dropped into the vial, the cap is replaced on 

the vial, the vial is inverted a few times so the mixture is mixed. And there is a color 

 

10

 In stating this conclusion we do not presuppose that plaintiff has proven or will 

be able to prove the other elements of a prima facie Proposition 65 cause of action; we 

address here only the narrow question of whether there was a failure of proof as a matter 

of law because plaintiff did not prove that the chemical in defendants’ products is 

precisely the same chemical alleged in the complaint. 

11

 Courts are sometimes called upon to make decisions about scientific matters, 

such as occurred here, based entirely on adversarial expert opinion. This may not be the 

best, or most accurate manner in which to settle scientific disputes. As we recently 

stated, “[i]t bears contemplating . . . whether the truth about complex, threshold scientific 

issues encompassed within Proposition 65 . . . is best derived by application of the 

substantial evidence rule to the testimony and opinions of dueling experts serving 

partisan commitments.” (People ex rel. Brown v. Tri-Union Seafoods, LLC (2009) 171 

Cal.App.4th 1549, 1573.) We think it would be helpful if the Legislature were to 

authorize the O to adopt an administrative process by which such threshold scientific 

issues might be determined. This process could be imposed as a requirement for 

exhaustion of administrative remedies, or might be optional such that, in the proper case, 

the court could invoke the doctrine of primary jurisdiction. (See, e.g., South Bay 

Creditors Trust v. General Motors Acceptance Corp. (1999) 69 Cal.App.4th 1068.) 
14

comparison between the water [in] the vial and what are called the colored chips on the 

side of the vial. And that gives a reading on the chlorine content of the water and 

whether or not more chlorine is needed.”12

The chemical formula for orthotolidine is C14H16N2 (14 carbon atoms, 16 hydrogen 

atoms, and two nitrogen atoms). Orthotolidine is an “aromatic amine” the elements of 

which are bonded “covalently,” that is, they have very strong bonds. The formula for 

orthotolidine dihydrochloride is C14H16N2.2HCL. Thus, the two formulas are the same, 

except the dihydrochloride form of OTO has an addition of .2HCL. The “.2HCL” 

indicates the presence of hydrochloric acid which has a weak, or “ionic,” bond to the 

orthotolidine molecule. Because of the ionic bond, the .2HCL portion of OTO 

dihydrochloride “dissociates” when the solid form of the dihydrochloride is placed in a 

liquid solution, while the covalently bonded C14H16N2—or orthotolidine—remains intact. 

In an aqueous acidic solution, the hydrogen protons from the HCL or acid attach 

to the orthotolidine in a transitory manner; this is described as moving on and off, or 

“hopping on and off” the orthotolidine molecules very rapidly. The orthotolidine is then 

said to be “protonated.” Therefore, in an acidic aqueous solution, such as in defendants’ 

products (which contain hydrochloric acid), orthotolidine exists in the protonated form. 

The chloride (.2HCL) remains in the solution, but is dissociated from the OTO. 

The frequency of the protonation depends on the pH of the solution. At a highly 

acidic pH of about three the OTO will be protonated almost all of the time; at a more 

basic pH of about six (in plain water) the OTO will not be protonated at all. The result is 

the same whether OTO or OTO dihydrochloride is placed in solution. In defendants’ 

products, which are highly acidic, both will become protonated OTO, meaning that the 

OTO molecules will almost always have hydrogen protons with transient bonds. If, 

however, either OTO or OTO dihydrochloride are placed in a very basic solution, they 

 

12

 Plaintiff alleged in the complaints that consumers using defendants’ products 

“sustained exposure by dermal contact” to the OTO by using a bare thumb or other finger 

rather than the cap to cover the vial containing the pool water and the OTO solution 

before mixing. Plaintiff also alleged, in the second complaint, that “[e]xposure also 

occurs by way of spillage.” 
15

“end up fully as the free base [OTO].” According to defendants’ expert, one can start 

with OTO, convert it to OTO dihydrochloride by placing it in a highly acidic solution, 

and then reconvert it to OTO by making the solution basic. 

Orthotolidine and the dihydrochloride form have different solubility, corrosivity 

and melting points. The dihydrochloride form is more corrosive because it is acidic. The 

hydrochloride is added for the purpose of making OTO highly soluble. The two 

compounds also have “different spectra in NMR”13 and absorb light in the ultraviolet 

spectrum at a different frequencies.14 

2. Matters of Disagreement

a. What is the proper testing method?

The Environmental Protection Agency has approved an analysis known as Method 

8270C to test for the presence of orthotolodine in media (soil, water, etc.).15 According 

to plaintiff’s expert, an analysis of defendants’ products using this method showed the 

presence of orthotolidine. This method does not distinguish between the protonated and 

unprotonated forms of OTO because, during the preparation of the solution for analysis, 

the pH is changed from acid to a base which changes any protonated form of OTO into 

its unprotonated, or neutral, form in order to extract it from the solution for analysis. 

According to plaintiff’s expert this method is the proper one to use to determine the 

presence of OTO because it was designed to identify the presence of OTO in any 

medium, such as water that is acidic or basic, including in defendants’ aqueous acidic 

products. 

 

13

 NMR is Nuclear Magnetic Resonance. 

14

 Plaintiff’s expert explained that protonated aromatic compounds will have a 

different UV spectrum because the protonation affects the electrons that are in the 

molecule. “It’s not a chemical effect. It’s just a charge effect.” 

15 Method 8270C is described in the record as a “gas chromatography/mass 

spectrometry” method “used to determine the concentration of semivolatile organic 

compounds in extracts prepared from many types of solid waste matrices, soils, air 

sampling media and water samples.” 
16

According to defendants’ expert, method 8270C cannot distinguish between 

orthotolidine and OTO dihydrochloride, and therefore was “completely inappropriate” to 

determine which of the two chemicals was present in defendants’ products. Thus, if OTO 

dihydrochloride is present in an acidic solution, the test method, by making the solution 

basic, chemically alters the OTO dihydrochloride and changes it into the free amine 

(orthotolidine). As a result, a test using Method 8270C can show the presence of 

orthotolidine even if the original sample—before the pH was adjusted in preparation for 

extraction—contained only OTO dihydrochloride. 

Plaintiff’s expert explained, however, that altering the pH before extracting the 

OTO does nothing that would not otherwise have occurred naturally. As he explained, 

due to the nature of ionic bonds and applying Le Chatelier’s Principle—by which 

chemical equilibrium will continue to adjust itself after any extraction or dilution 

occurs—“if you just shook the extraction flask up and didn’t adjust the pH and let it sit 

for hours, maybe days . . . this neutral form would be what you end up with in the 

extraction solvent.” He testified that Method 8270C was designed to take the differences 

between OTO and OTO dihydrochloride into account, “[a]nd the pH adjustment just 

makes it faster and more uniform in how it behaves.” 

According to defendant’s expert, NMR and UV spectroscopy were appropriate 

tests for the presence of orthotolidine or OTO dihydrochloride in solution because they 

do not change the nature of the solution. His laboratory tested defendants’ products using 

NMR, and the test results showed the products contained the dihydrochloride form of 

OTO, but none of the free amine (OTO) form at all. Although the experts agreed that the 

molecules in solution shifted very rapidly from the protonated to unprotonated form, 

defendant’s expert testified that at any point in time the amount of the unprotonated 

form—or orthotolidine—was below the detection limit of the NMR experiment. Based 

on theoretical calculations, he estimated the amount of the unprotonated form in solution 

at any point in time was .001 percent of the solution. A second defense expert offered 

similar opinions: that NMR spectroscopy is “uniquely suited to analyze molecules in 

solution[,]” and the NMR tests would have detected the free base form of orthotolidine if 
17

it had been present, but showed only the dihydrochloride form and none of the free base 

form. 

b. Is protonated orthotolidine the same as orthotolidine dihydrochloride?

Another area of dispute was whether the protonated form of orthotolidine—the 

form existing in defendants’ acid solution—is the same chemical as orthotolidine 

dihydrochloride. Plaintiff’s expert testified that orthotolidine dihydrochloride cannot be 

present in an aqueous solution but can only exist in its solid form. He testified that, once 

OTO dihydrochloride is dissolved in solution, it loses its structure, and what remains 

intact is the covalently bonded orthotolidine molecules, having only transitory bonds to 

the HCL protons (i.e., the protonated form of orthotolidine), with chloride atoms present 

in the solution but completely dissociated from the OTO. 

Defendants’ expert, on the other hand, testified that in the acidic environment of 

defendants’ products, the protonated form of OTO is the same as orthotolidine 

dihydrochloride. Even though in its solid form, orthotolidine dihydrochloride did not 

“have protons hopping on and off of it,” the expert opined, it was the same chemical as 

protonated orthotolidine in solution, when protons did “hop on and off the Orthotolidine,” 

because in both the solid form and in solution, the chemical was protonated. They were 

the same compound in different physical forms. In the solid form, he testified, “[t]he 

hydrogens are attached to the nitrogen and the chlorides are nearby,” fixed in position, 

but not attached. In solution, the chlorides are dissociated or “floating around hydrated,” 

with the same number of chlorides as in the solid form. The distance between the

nitrogen and the chlorine would depend on the concentration of the solution.16

Defendant’s expert could not state, however, whether the utility of defendants’ 

products in detecting the amount of chlorine in water would be different depending upon 

 

16

 On this subject, defendant’s second expert provided essentially the same 

opinions: In defendants’ solutions there is no difference between protonated OTO and 

OTO dihydrochloride other than the fact that the distance between the nitrogen and 

chlorides was greater in the solution than in the solid structure. He also agreed that, 

although the chloride atoms remain in solution, they do not remain associated with the 

same OTO molecule but they “hop from one to the other.” 
18

whether it contained OTO or OTO dihydrochloride; he also could not state to what 

degree the addition of the product to the pool water would change the pH of the OTO, but 

agreed it would change toward neutral (unprotonated).17 

In rebuttal, plaintiff’s expert testified that in solution, the chloride and the 

protonated molecules were so far apart that it “conceptually doesn’t really make sense” to 

say the positive and negative charges maintained an ionic association. He disagreed with 

the defendant’s experts, explaining, “you can’t have association and dissociation at the 

same time. When the molecules are put into water the chlorides dissociate completely, 

they’re free to move throughout that solution,” and therefore OTO dihydrochloride 

cannot exist in solution. 

c. No testimony on materiality of differences

There was a total absence of testimony on the subject of whether the differences 

between the two forms of orthotolidine, as described by defendants, would or would not 

have a material impact on the carcinogenicity of defendants’ products for purposes of 

prima facie proof of a Proposition 65 violation. We assume none was offered because the 

trial court’s restrictive formulation of the issue to be tried—the sole question being 

whether the chemical in defendants’ products was orthotolidine—precluded the 

introduction of any such evidence. 18

3. Other Evidence

In addition to the expert testimony, the parties offered the following evidence: 

a. The Governor’s list

Both OTO and OTO dihydrochloride are listed on the Governor’s Proposition 65 

list as carcinogenic. OTO was placed on the list in 1988, based on the opinion of the 

Proposition 65 Scientific Advisory Panel of the California Health and Welfare Agency, 

 

17

 Plaintiff alleged dermal contact occurred after the OTO solution was added to 

the pool water—thus creating a far more basic solution in which, according to both 

experts, the OTO dihydrochloride shifts to OTO. 

18

 When plaintiff’s counsel posed such a question to defendant’s expert (“Does an 

extra proton change the carcinogenicity of Orthotolidine?”), defendants’ counsel objected 

and the objection was sustained. 
19

after reviewing various documents, including the National Toxicology Program’s Fourth 

Annual Report on Carcinogens. (§ 25249.8 subd. (b).) OTO dihydrochloride was placed 

on the Governor’s list in 1992, based upon the lead agency’s conclusion that an 

“authoritative body”—here the National Toxicology Program (NTP)—had formally 

identified OTO dihydrochloride as causing cancer. (§ 25249.8 subd. (b); Cal. Code Regs, 

tit. 27, § 25306.) There is no evidence that the method used by the agency to list a 

particular chemical has any significance. 

The chemicals are listed by name and also by their “CAS” numbers. This refers to 

the Chemical Abstract Service, which was created to “make it easier for chemical 

researchers to find work relating to their own work.” Neither party’s experts assigned 

particular significance to the fact that OTO and OTO dihydrochloride had different CAS 

numbers.19 

b. The NTP Fourth Annual Report on Carcinogens 

This undated report states there is evidence of carcinogenicity of OTO in 

animals.20 It describes the uses of OTO in making dyes, pigments and other products, 

including in swimming pool chlorine test kits. The report states that exposure to OTO 

can be through dermal absorption or ingestion if the test solutions are emptied into the 

pool. The report also describes the amounts of OTO and “its dihydrochloride” that have 

been produced and imported in 1978, 1979 and 1980. 

 

19

 Defendants contend that the CAS numbers are significant because they are used 

by the California Division of Occupational Safety and Health to identify chemicals on its 

Hazardous Substances List and are incorporated into the federal Occupational Safety and 

Health Administration regulations. The fact that the numbers are used, however, does not 

tend to prove anything about whether the assignment of different numbers to two 

compounds is significant. Defendant’s expert testified that the difference in CAS 

numbers “may or may not be trivial.” Plaintiff’s expert testified a chemist would not 

ascribe any significance to the difference. 

20

 The report uses the term “3,3’-dimethylbenzidine (DMB)” rather than 

orthotolidine. 
20

c. The Merck index21

The 2006 version of the Merck Index (Fourteenth Edition), Monograph number 

09514 identifies 3,3’-dimethylbenzidine as “o-Tolidine” and includes “Dihydrochloride” 

as a “Derivative Type” of OTO. 

d. The IARC monograph22

In 1972, the International Agency for Research on Cancer (IARC) issued a 

monograph describing the carcinogenic properties of various chemicals, including “3,3’-

dimethylbenzidine (o-tolidine).” The monograph describes OTO as “a weak base that 

forms salts with HCl . . . etc.,” and states it is used, among other things, for the 

“colorimetric determination of chlorine in air and water.” The IARC report concluded 

there was a “suspicion” of carcinogenicity, but supporting evidence was not available. 

e. The federal occupational standards

In 1978 the National Institute for Occupational Safety and Health (NIOSH) issued 

a report providing “criteria for a recommended standard . . . occupational exposure to oTolidine.” It states that o-tolidine is used, among other things, in tests for chlorine in 

water, and that “the term ‘o-tolidine’ refers to “various physical forms of the compound 

and its salts.” It further states that skin contact with o-tolidine “shall be avoided.” 

Although adherence to specific NIOSH standards is required if OTO is handled or stored 

 

21

 The Merck Index is a reference book that lists a “huge number of chemicals,” 

their properties, their synonyms, their empirical formulas, and illustrations of their 

structures. It is an “authoritative” and reliable source. 

22

 The Monographs program is described in this way on the IARC website: “The 

IARC Governing Council adopted a resolution concerning the role of IARC in providing 

government authorities with expert, independent, scientific opinion on environmental 

carcinogenesis. As one means to that end, the Governing Council recommended that 

IARC should prepare monographs on the evaluation of carcinogenic risk of chemicals to 

man, which became the initial title of the series. [¶] . . . [¶] Through the Monographs

programme, IARC seeks to identify the causes of human cancer.” 

<http://monographs.iarc.fr/ENG/Preamble/currenta1background0706.php.>
21

in sealed containers, those standards do not apply to users of “test kits containing otolidine.”

f. The Office of Environmental Health Hazard Assessment report23

In 2002, OEHHA published a report setting “No Significant Risk Levels (NSRLS) 

For the Proposition 65 Carcinogens 3,3’-Dimethylbenzidine and 3,3’-Dimethylbenzidine 

Dihydrochloride.” The report reviewed various studies and their findings, assessing the 

results of tests conducted with OTO and with OTO dihydrochloride as a group. The 

OEHHA concluded that the cancer potencies (“mg/kg-day”) of OTO and OTO 

dihydrochloride are, respectively, 16 and 12, and their NSRLs are, respectively, 0.044 

and 0.059 “μg/day.”

24

 These estimates were derived from a 1991 NTP test in which male 

rats were exposed to OTO dihydrochloride via drinking water. “The cancer potency 

estimate obtained from studies of [OTO dihydrochloride] was used as the basis for 

[OTO] cancer potency after adjusting for differences in molecular weight.” 

g. Defendants’ product labels and recipes

The defendants’ products are uniformly labeled as containing orthotolidine or 

OTO, not orthotolidine dihydrochloride.25 The record also includes what appear to be 

defendants’ recipes for “OTO” or “OTO #1 Solution” the ingredients for which are 

 

23

 The OEHHA is the lead agency charged with implementing Proposition 65. 

(§ 25249.12; Cal. Code Regs., tit. 27, § 25102, subd. (o).) Among other things, it is 

authorized to determine “whether a level of exposure to a chemical known to the state to 

cause cancer poses no significant risk.” (Cal. Code Regs., tit. 27, § 25701 et seq.) These 

determinations are referred to as “No Significant Risk Levels” or “NSRLs.” (See, e.g., 

Baxter, supra, 120 Cal.App.4th at p. 358.) 

24

 A “μg” is a microgram, one millionth of a gram, or one thousandth of a 

milligram. (McGraw-Hill Dictionary of Scientific and Technical Terms (4th ed. 1989), 

p. 1195.)

25

 An employee and officer of one of the defendants testified that “the label 

doesn’t signify the chemical components of the product.” He admitted, however, that the 

label also indicates that the product contains hydrochloric acid. 
22

deionized water, orthotolidine powder and hydrochloric acid.26 There is also a Material 

Safety Data Sheet for the product called “Aqua Chem OTO” which is described as 

“Ortho-tolidine dihydrochloride solution” and identifies the ingredients as Hydrochloric 

acid and Orthotolidine. 

D. Analysis

The trial court ruled that plaintiff did not prove defendants’ products contained 

orthotolidine because defendants “presented a more persuasive and coherent body of 

evidence” showing that the chemical was orthotolidine dihydrochloride. We agree with 

defendants that this finding is supported by substantial evidence. This fact, however, is 

not dispositive. The question remains whether this was a “material failure of proof” of 

the alleged violation of Proposition 65. 

The evidence at trial indisputably demonstrates that defendants’ products contain a

“listed chemical.” Yet it took two years of litigation, including a two-day trial with 

contested expert opinions before the question “what’s in the bottle?” could be answered. 

This is not surprising, given that defendants themselves labeled their products as 

containing orthotolidine, and the evidence at trial showed the two chemicals are more 

similar than they are different: Orthotolidine dihydrochloride is the “salt form” or “the 

dihydrochloride form” of orthotolidine; both have the same core chemical structure, 

which remains intact in solution; both become “protonated orthotolidine” when in a 

highly acidic solution, such as found in defendants’ products; both can be converted 

from protonated to unprotonated—according to defendants—simply by changing the pH 

of the solution in which they are placed; and both chemicals are carcinogens. 

Significantly, OEHHA estimated the cancer properties and NSRLs for both forms of 

orthotolidine in a single report, setting the cancer potency estimate for OTO based on a 

 

26

 In one recipe, “O-Tolidine powder” is combined with hydrochloric acid; this is 

left to sit for three days, and creates an “acid mix.” The acid mix is added to distilled 

water and more hydrochloric acid to create the solution. According to defendant’s expert 

this means that OTO has been converted to OTO dihydrochloride before adding it to the 

other ingredients. 
23

study of OTO dihydrochloride. Thus, the agency tasked with enforcing Proposition 65 

appears to treat the two forms of orthotolidine as the same carcinogen and it assigned to 

them different NSRLs based solely on their differences in molecular weight. 

These nuanced distinctions between orthotolidine and its dihydrochloride, coupled 

with defendants’ own evidence that its products contain a listed chemical, demonstrate 

there was not a “material failure of proof” for purposes of Proposition 65. But due to the 

trial court’s restrictive formulation of the dispositive issue—do defendants’ products 

contain orthotolidine?—the question whether there was a material variance between 

pleading and proof did not and could not arise. Wholly absent from the trial court’s 

expression of the “core issue” was whether the distinction between orthotolidine and its 

dihydrochloride was meaningful either for purposes of Proposition 65 or for purposes of 

defendants’ due process rights. Indeed, the court expressly rejected plaintiff’s argument 

that Proposition 65, as a remedial statute, necessitated more liberality in testing the 

sufficiency of plaintiff’s proof; it concluded, instead, that plaintiff’s burden was to prove 

that defendants’ products contained orthotolidine, and if it could not, defendants were 

entitled to judgment. The court’s formula left no room to consider whether plaintiff’s 

proof was or was not a material variance from its pleading.

27

As we have explained, to be material, a variance must have misled defendants to 

their prejudice in maintaining their defense on the merits, or put another way, “ ‘misled 

[them] as to the real issues of fact involved in the case.’ ” (Frazier v. Yor-Way Market, 

Inc. (1960) 185 Cal.App.2d 390, 399; Code Civ. Proc., § 469.) We cannot say on this 

record and in the first instance whether defendants were misled to their prejudice by 

plaintiff’s allegations. We must therefore remand the matter so the parties will have the 

opportunity to present argument, and any relevant evidence, that the proof was or was not 

 

27

 The court also tacitly rejected plaintiff’s request that it be allowed to show, 

before the case is dismissed, that “in . . . terms of their carcinogenicity and the applicable 

(NSRL), there is absolutely no difference between OTO and Protonated . . . OTO” and 

that “the form of OTO consumers are exposed to is Unprotonated OTO” when 

defendants’ products are used for their intended purposes.
24

a material variance from the pleading, in the context of Proposition 65 and its remedial 

purposes.

28

 

III. DISPOSITION

The judgment is reversed, and the matter is remanded for proceedings consistent 

with this opinion. The post-judgment orders are vacated.

_________________________

Rivera, J.

We concur:

_________________________

Ruvolo, P.J.

_________________________

Humes, J.

 

28

 During argument in the trial court, defendants’ counsel demonstrated his 

appreciation for the fact that the identification of a chemical needs its Proposition 65 

context in order to be meaningful. As he explained, the differences in the two forms of 

orthotolidine “will become very important in phase two of the trial . . . because in that 

phase of the trial, defendants will be using these differences to establish that there is in 

fact no significant risk to consumers from exposure to this chemical as alleged in the 

complaint or from even the dihydrochloride as [the exposure is] alleged in the 

complaint.” Thus, defendants themselves suggest, without necessarily conceding, that 

the differences between the chemicals relate more to the affirmative defenses described in 

Section 25249.10 than to the proof, in the first instance, of a violation. But as we have 

stated, the parties must be given the opportunity to present argument and any evidence 

needed for that analysis.