I join in part III of the Discussion portion of the majority opinion and concur with the conclusions reached in parts I and II but not the reasoning behind them.
*436By 2009, both the South Coast Air Quality Management District (AQMD) and California’s State Air Resources Board (CARB) were in the process of formulating regulations to reduce ozone-causing emissions by limiting the amount of volatile organic compounds in paint thinners and multipurpose solvents.1
On March 6, 2009, the AQMD adopted “Rule 1143,” which required manufacturers of paint thinners and multipurpose solvents to limit the amount of volatile organic compounds in those products to 300 grams per liter by January 1, 2010, and 25 grams per liter by January 1, 2011.2 The primary way to achieve these limits is to replace volatile organic compounds with acetone.
As required by the California Environmental Quality Act (CEQA; Pub. Resources Code, § 21000 et seq.), the AQMD prepared and certified an environmental assessment before adopting Rule 1143, in which it considered, among other things, the increased risk of fire posed if manufacturers were to begin replacing volatile organic compounds in solvents and thinners with compounds that posed a greater risk of fire. (Acetone has a low flashpoint, meaning it catches fire easily.)3 The environmental assessment concluded that the increased fire risk resulting from implementation of Rule 1143 would be insignificant. However, at a public hearing held by the AQMD’s governing board, Chief Steve Bunting of the Newport Beach Fire Department commented that the flashpoint of acetone was “a big red flag” for fire department personnel. (Postadoption, this concern was echoed by the Office of the State Fire Marshall.) The governing board nevertheless approved the AQMD’s environmental assessment and adopted Rule 1143.
On April 1, 2009, appellant W.M. Barr & Company, Inc., a manufacturer of thinners and solvents, filed a CEQA lawsuit against the AQMD, alleging the AQMD’s environmental assessment did not adequately address the increased fire risk posed by acetone.
While the lawsuit was pending, AQMD staff met with the State Fire Marshal’s office, local fire officials, and CARB staff to address concerns regarding the fire risks posed by use of acetone in thinners and solvents. The fire officials were not concerned about use of acetone per se, as some solvents and thinners already contain acetone or other flammable materials. But those *437are sold under names that reflect their primary components—for example “Klean Strip Acetone,” “Klean Strip Toluene,” and “Klean Strip Xylene.” The fire officials were concerned that the principal display panels on products sold under general names such as “paint thinner,” “multi-purpose solvent,” “clean-up solvent,” or “paint clean-up” would not reflect the increased fire risk presented by products reformulated to comply with Rule 1143.4 The fire officials were concerned that when those products were reformulated to contain acetone, the display panels would remain unchanged, and consumers accustomed to using the products would not bother to read new warning labels on the back of the container.
In light of this concern, the AQMD and CARB worked with the fire marshal’s office and Chief Bunting to develop additional labeling requirements for solvent and thinner products with general names.
Meanwhile, the trial court found the AQMD’s environmental assessment failed adequately to address the potential increased fire hazard presented by substitution of acetone for mineral spirits in paint thinner. On April 1, 2010, the court ordered the AQMD to rescind Rule 1143’s 25 grams per liter limit pending further CEQA review. The court left in place the interim 300 grams per liter limit.
The AQMD rescinded the 25 grams per liter limit in Rule 1143 on June 4, 2010, then readopted it on July 9, 2010, with a new warning label requirement. It also filed a supplemental environmental assessment. The new label requirement was actually a prohibition: No “flammable” or “extremely flammable” thinner or multipurpose solvent could be sold if the name on the principal display panel was generic, i.e., “paint thinner,” “multi-purpose solvent,” “clean-up solvent,” or “paint clean-up.” This prohibition did not apply to any product that included on the principal display panel, in a font size as large as, or larger than, the largest font size of any other words on the panel, the common name of the chemical compound that renders the product flammable, e.g., “acetone” or “methyl acetate.” The prohibition also did not apply where a “hang tag” or sticker attached to the container displayed either of the following statements: “Formulated to meet low VOC limits: see warning label” or “Formulated to meet low VOC limits with [Acetone, Methyl Acetate, etc.]” Alternatively, a manufacturer would be permitted to label its product genetically if the above language was included on the principal display panel in a font size as large as, or larger than, the largest font size of the generic name. Finally, products that otherwise met CARB labeling requirements specified in title 17 of the California Code of *438Regulations, section 94512, subdivision (e), were exempt from the prohibition against generic labeling.5
CARB staff, Chief Bunting, and State Fire Marshal staff all agreed these new warning requirements reduced the risk of acetone-related injuries to insignificance.
In August 2010, one month after the AQMD readopted Rule 1143, CARB adopted its own solvent and thinner regulations. Under CARB’s regulations, manufacturers of paint thinners and multipurpose solvents were required to limit the amount of volatile organic compounds in those products to 30 percent by weight by December 31, 2010, and 3 percent by weight by December 1, 2013. (Cal. Code Regs., tit. 17, § 94509.)6 The CARB labeling requirements were similar to the AQMD’s requirements: A thinner or solvent could not be designated genetically as “paint thinner” or “multipurpose solvent” on the principal display panel unless the label or an attached hang tag stated the product was reformulated to meet VOC limits or the principal display panel “displayed], in both English and Spanish and a font size as large as, or larger than, the font size of all other words on the panel, the common name of the chemical compound (e.g., ‘Acetone,’ ‘Methyl acetate,’ etc.)” that renders the product flammable. (Cal. Code Regs., tit. 17, § 94512, subd. (e).)
On July 15, 2010, Barr filed a second lawsuit challenging Rule 1143 as amended. It alleged the AQMD’s supplemental environmental assessment was inadequate because the fire hazards presented by Rule 1143 were *439mitigated only by new labeling requirements that were themselves preempted by the Federal Hazardous Substances Act (FHSA). It also alleged Rule 1143’s volatile organic compound limits were preempted by CARB’s pre-2009 consumer product regulations pertaining to general purpose cleaners.
After a hearing, the trial court denied Barr’s petition. It found substantial evidence supported the AQMD’s conclusion that Rule 1143 would not result in significant fire hazard impacts, Rule 1143 was not preempted by federal or state law, and the AQMD’s supplemental environmental assessment was adequate.
A. Federal Preemption
The majority concludes the Rule 1143 labeling requirements are not preempted by the FHSA because they do not require manufacturers to add language to a product label that varies from language prescribed by the FHSA. I agree Rule 1143 is not preempted by the FHSA, but for different reasons.
The FHSA prohibits “introduction or delivery for introduction into interstate commerce of any misbranded hazardous substance.” (15 U.S.C. 1263(a).) A “misbranded hazardous substance” is any hazardous substance that fails to bear a label stating, prominently and in conspicuous and legible type: (1) the name and place of business of the manufacturer; (2) the common or usual name or the chemical name of the hazardous substance; (3) the signal word “DANGER” on substances that are extremely flammable; (4) the signal word “WARNING” or “CAUTION” on all other hazardous substances; (5) an affirmative statement of the principal hazard, such as “Flammable,” “Combustible,” “Vapor Harmful,” “Causes Bums,” “Absorbed Through Skin,” or similar “wording descriptive of the hazard”; (6) precautionary measures describing the action to be followed or avoided; (7) instruction, when necessary or appropriate, for first-aid treatment; (8) instructions for handling and storage of packages that require special care in handling or storage; and (9) the statement “Keep out of the reach of children” or its equivalent. (15 U.S.C. 1261(p).)7
*440This labeling requirement preempts any nonidentical state cautionary labeling requirement “designed to protect against the same risk of . . . injury.” (15 U.S.C. 1261, note (b)(1)(A).) Thus, if a state regulation mandates a label that is more elaborate than or different from the one required by the FHSA and its regulations, the state regulation is preempted. (Moss v. Parks Corp. (4th Cir. 1993) 985 F.2d 736, 740.)
No conflict exists between the FHSA and Rule 1143.
Rule 1143 can be satisfied several different ways. Most easily, a manufacturer could discontinue its practice of genetically naming its products. Nothing in the FHSA requires that manufacturers be permitted to give generic names to hazardous products. Alternatively, a manufacturer could satisfy Rule 1143 by putting the common name of a product’s chief hazardous chemical (e.g., “acetone” or “ethyl acetate”) on the container’s principal display panel in a font as large as that of the generic product name. This requirement is substantially identical to that imposed by 15 U.S.C. 1261, which requires that the label set forth the common or usual name of the product’s hazardous substance.
A manufacturer could also satisfy Rule 1143 by putting the following language on the container’s primary display panel or on an attached sticker or hang tag: “Formulated to meet low VOC limits; see warnings on label.” The first clause (“formulated to meet low VOC limits”) satisfies the FHSA’s requirement that the label bear “wording descriptive of the hazard.” The second clause (“see warnings on label”) does no more than direct the user to the warning label, and is thus permissible either as a handling instruction or as an extension of the FHSA-regulated warning label.
Barr contends this language is preempted by the FHSA because it is not identical to warning language the act specifically prescribes. The argument is without merit because the FHSA prescribes no specific language for flammable products other than the words “warning” or “caution.” The FHSA permits any other “wording descriptive of the hazard,” any language setting forth instructions for handling, storage and first aid treatment and precautionary measures to be followed or avoided, and any language equivalent to the *441statement “ ‘[k]eep out of the reach of children.’ ” (15 U.S.C. § 1261(p).) (See People ex rel. Lungren v. Cotter & Co. (1997) 53 Cal.App.4th 1373, 1385-1386 [62 Cal.Rptr.2d 368] [FHSA sets forth only a general duty to inform users and purchasers of potentially dangerous items].)
In short, the FHSA does not preempt Rule 1143 simply because no conflict between the two exists.
B. State Preemption—Regulation of General Purpose Cleaners
Neither is Rule 1143 preempted by CARB’s regulations pertaining to general purpose cleaners. Barr argues Rule 1143’s definition of paint thinners is so broad that it could include general purpose cleaners as defined by CARB in California Code of Regulations, title 17, section 94508. It argues any regulation of paint thinners by the AQMD would thus be preempted by CARB’s general purpose cleaner regulations, which were adopted in 1994. The argument is without merit.
CARB defines 159 consumer products in California Code of Regulations, title 17, section 94508. Some of the products are identified by their chemical compositions.8 Others are defined by their uses. For example, “paint thinner” is defined as “any liquid product used for reducing the viscosity of coating compositions or components . . . .” (Cal. Code Regs., tit. 17, § 94508, subd. (a)(113).) Yet other products are categorized by their labeling. “General purpose cleaner” is defined as “a product labeled to clean a variety of hard surfaces. ‘General Purpose Cleaner’ includes, but is not limited to, products designed or labeled for general floor cleaning, kitchen, countertop, or sink cleaning, and cleaners designed or labeled to be used on a variety of hard surfaces such as stovetops, cooktops, or microwaves.’ ” (Id., subd. (a)(70).) “Multi-purpose solvent” is defined as “any liquid product designed or labeled to be used for dispersing, dissolving, or removing contaminants or other organic materials.” (Id., at subd. (a)(104)(B).)
Regulations for consumer products defined in California Code of Regulations, title 17, section 94508 are set forth in California Code of Regulations, title 17, section 94509.
Barr finds identity between paint thinners and general purpose cleaners by way of an inference it draws from the different way Rule 1143 treats paint *442thinners and multipurpose solvents. Rule 1143 defines “consumer multipurpose solvents” in pertinent part as “any liquid products designed or labeled to be used for dispersing or dissolving or removing contaminants or other organic materials for personal, family, household, or institutional use . . . [¶] . . . ‘Multi-purpose Solvents’ . . . do not include any products making any representation that the product may be used as, or is suitable for use as a consumer product which qualifies under another definition in California Code of Regulations Title 17, § 94508 . . . .” (Italics added.) Rule 1143 defines “consumer paint thinners” in pertinent part as “any liquid products used for reducing the viscosity of coating compositions or components for personal, family, household, or institutional use . . . .” Barr argues that whereas Rule 1143 expressly excludes from its definition of multipurpose solvent any contaminant-dissolving liquid that is labeled as also having other uses, it contains no similar limitation regarding paint thinners. Absence of such a limitation can only mean the AQMD intended to embrace other consumer products within the definition of paint thinners. Barr does not expressly identify on appeal what other product from the California Code of Regulations, title 17, section 94508 list would be suitable for reducing paint viscosity and also qualify as a general purpose cleaner, but suggested below that its “Klean-Strip Methyl Ethyl Ketone” and “Klene Strip Xylol Xylene” “could” fit the bill.
I am not persuaded Barr has drawn a valid inference from Rule 1143’s disparate treatment of thinners and solvents or, even if it has, that the inference supports its argument that the AQMD’s paint thinner regulations are preempted by CARB’s general purpose cleaner regulations.
AQMD could have had several reasons for treating thinners and solvents differently. Rule 1143 defines multipurpose solvent in terms of its design and label, while paint thinner is defined in terms only of its use. Whether or not this distinction makes any practical difference, it at least furnishes a reasonable basis for the AQMD’s refusal to add a label-based limitation to its paint thinner definition. AQMD could also have opted not to issue a label-based exemption for thinners for the reason it gives on appeal; If it did so, manufacturers could evade the regulations simply by relabeling their thinners. More substantively, the AQMD may have concluded that the danger of adopting overbroad regulations required it to insert limiting language as to multipurpose solvents, a relatively broad class of products, but not to paint thinners, a relatively narrower class. In any event, nothing in the record compels the conclusion that the AQMD intended to regulate nonthinners.
At any rate, Barr fails to identify any particular product that would fall under Rule 1143’s definition of paint thinners and also be regulated as a general purpose cleaner. Barr suggested below that its Klean-Strip Methyl *443Ethyl Ketone and Klene Strip Xylol Xylene “could” qualify as both thinners and multipurpose cleaners, but it does not attempt to support the suggestion on appeal. Neither does it identify any actual conflict between Rule 1143 and preexisting CARB standards.
I would conclude based on the lack of an actual conflict between Rule 1143 and the general purpose cleaner regulation set forth in California Code of Regulations, title 17, section 94509 that the latter does not preempt the former.
C. State Preemption—CARB’s Regulation of Thinners and Solvents
The majority reaches the same result by concluding that first-adopted regional' regulations preempt later-adopted state regulations. The conclusion is unnecessary because Barr does not contend otherwise. Barr contends only that preexisting CARB regulations—those pertaining to general purpose cleaners—preempt Rule 1143. As I discuss above, they do not.
Even had the parties engaged the issue, I would conclude that portions of Rule 1143 are preempted by the CARB regulations pertaining to thinners and multipurpose solvents.
First, an actual conflict exists between the two sets of regulations. Although the volatile organic compound limits for thinners and solvents they set forth are essentially the same, CARB’s final limit does not go into effect until December 31, 2013, three years later than Rule 1143’s final limit, and CARB’s rule contains a three-year sell-through period, compared with the one-year sell-through period permitted by Rule 1143. Second, specifically under subdivision (f) of Health and Safety Code section 41712 and also under well-settled law, CARB’s regulations preempt contrary regulations set forth in Rule 1143. (See Sherwin-Williams Co. v. City of Los Angeles (1993) 4 Cal.4th 893, 897 [16 Cal.Rptr.2d 215, 844 P.2d 534] [“ ‘If otherwise valid local legislation conflicts with state law, it is preempted by such law and is void.’ [Citations.]”].)
The majority’s contrary conclusion, that the CARB regulation is preempted by Rule 1143, is based on a reading of subdivision (f) of Health and Safety Code section 41712 (section 41712), which provides: “A district shall adopt no regulation pertaining to disinfectants, nor any regulation pertaining to a consumer product that is different than any regulation adopted by the state *444board for that purpose.” AQMD argues this language refers only to regulations already adopted by CARB, because otherwise the Legislature would have stated that a district shall not “adopt or enforce” regulations that conflict with state regulations.
This reading is reasonable but not compelling, and it would contravene precedent, thwart regulatory uniformity, and upend the primacy given by the Legislature to CARB. A point in favor of the reading is that the statutory language does say a district may not “adopt” a rule different from the board’s rule. It does not say the district may not “adopt or continue in effect” or “adopt or enforce.” (See, e.g., 15 U.S.C.A. (2008) foll. § 1261, Notes, Effect Upon Federal and State Law (b)(1)(A); Health & Saf. Code, § 41712, subd. (i)(1).)
The point against the majority’s conclusion is that it would lead to a patchwork of regulations based on which agency adopts a particular regulation first. In California there are five air quality management districts and dozens of air pollution control districts, one for each county not already included in an air quality management district. (Health & Saf. Code, §§ 40002, 40100, 40200, 40410, 40960, 41210, 41300.) The word “district” in section 41712 refers to any of these. (Health & Saf. Code, § 39025.) Under AQMD’s construction of section 41712, a nationwide manufacturer would have to navigate not only 51 sets of regulations for a particular product (one for each state plus the federal regulations), but also the regulations of dozens of air pollution control districts in California alone, and it would have to know when each district’s regulation was adopted so it could determine whether the district’s or state’s regulations controlled. This, I submit, is an undesirable result.
The Legislature sometimes agrees. In subdivision (i)(1) of Health and Safety Code section 41712 the Legislature stated its intent was “that air pollution control standards affecting the formulation of aerosol paints and limiting the emissions of volatile organic compounds resulting from the use of aerosol paints be set solely by the state board to ensure uniform standards applicable on a statewide basis.” (Ibid.) Although this statement of intent expressly pertains only to volatile organic compounds emitted from aerosol paints, I would be chary to conclude the Legislature intended that regulation of the same compounds emitted from other sources not be uniform. On the other hand, this is exactly the case with aerosol adhesives, as to which the Legislature has specifically stated that districts are free to issue regulations setting standards for volatile organic compound emissions that are more *445stringent than state standards; (Id., subd. (h)(3).) But the Legislature has never affirmatively stated that district regulations should preempt state regulations simply because they were adopted first.
I therefore agree with the court’s judgment but cannot agree with its reasoning.
A multipurpose solvent is a chemical used to clean grease and oil from machinery and tools.
Rule 1143 contained a one-year sell-through period, during which noncompliant products could be sold for up to one year beyond the effective date of each limit.
Contrary to common perception, the volatile organic compounds in paint thinner and multipurpose solvents do not catch fire easily.
Examples of such products are “Klean Strip Paint Thinner,” “Klean Strip Paint Clean-Up,” and “Recochem Solvent.”
Subdivision (e) of California Code of Regulations, title 17, section 94512 provides, in pertinent part:
“(1) [E]ffective December 31, 2010, until December 31, 2015, no person shall sell, supply, offer for sale, or manufacture for use in California any ‘Flammable’ or ‘Extremely Flammable’ Multi-purpose Solvent or Paint Thinner named, on the Principle Display Panel as ‘Paint Thinner,’ ‘Multi-purpose Solvent,’ ‘Clean-up Solvent,’ or ‘Paint Clean-up.’
“(2) Section 94512(e)(1) does not apply to products that meet either of the following criteria:
“(A) Products which include an attached ‘hang tag,’ sticker, or contrasting square or rectangular area on the Principle Display Panel that displays, at a minimum, the following statements in a font size as large as, or larger than, the ‘signal word’ (i.e., ‘DANGER,’ ‘WARNING,’ or ‘CAUTION’) as specified in title 16, Code of Federal Regulations, section 1500.121:
“ ‘Formulated to meet California VOC limits; see warnings on label; Vea las advertencias en la etiqueta, formulado complacientes con leyes de California’ or
“(B) Products where the Principle Display Panel displays, in both English and Spanish and a font size as large as, or larger than, the font size of all other words on the panel, the common name of the chemical compound (e.g., ‘Acetone,’ ‘Methyl acetate,’ etc.) that results in the product meeting the criteria for ‘Flammable’ or ‘Extremely Flammable.’ ”
Although CARB’s and the AQMD’s limits are expressed in different types of measurement, the AQMD represents they are equivalent.
15 U.S.C. 1261(p) provides in pertinent part: “The term ‘misbranded hazardous substance’ means a hazardous substance . . . intended ... for use in the household ... if such substance . . . fails to bear a label [¶] “(1) which states conspicuously (A) the name and place of business of the manufacturer, packer, distributor or seller; (B) the common or usual name or the chemical name (if there be no common or usual name) of the hazardous substance or of each component which contributes substantially to its hazard, unless the Commission by regulation permits or requires the use of a recognized generic name; (C) the signal word ‘DANGER’ on substances which are extremely flammable, corrosive, or highly toxic; (D) the signal word ‘WARNING’ or ‘CAUTION’ on all other hazardous substances; (E) an affirmative statement of the principal hazard or hazards, such as ‘Flammable,’ ‘Combustible,’ ‘Vapor *440Harmful,’ ‘Causes Bums,’ ‘Absorbed Through Skin,’ or similar wording descriptive of the hazard; (F) precautionary measures describing the action to be followed or avoided . . . ; (G) instruction, when necessary or appropriate, for first-aid treatment; (H) the word ‘poison’ for any hazardous substance which is defined as ‘highly toxic’ by subsection (h); (I) instructions for handling and storage of packages which require special care in handling or storage; and (J) the statement (i) ‘Keep out of the reach of children’ or its practical equivalent..., and [Ü “(2) on which any statements required under subparagraph (1) of this paragraph are located prominently and are in the English language in conspicuous and legible type in contrast by typography, layout, or color with other printed matter on the label.”
For example, “Alkylphenol Ethoxylate” is defined as “a nonionic surface active agent (surfactant) compound composed of an alkyl chain that contains at least eight carbon atoms and a polyethoxylate chain attached to a benzene ring.” (Cal. Code Regs., tit. 17, § 94508, subd. (a)(8).)