We are asked in this appeal to decide whether the board of health of Barnstable (board) has the authority to issue a municipal regulation prohibiting smoking “in all food service establishments, lounges and bars.” We hold that it does.

1. Background. We summarize the relevant facts from the uncontested documentary materials in the record. In 1995, the board began considering whether to impose regulations curbing the harmful effects of environmental tobacco smoke (ETS). After several public hearings and consideration of the issue between 1995 and 1996, the board adopted a regulation prohibiting smoking in public places, excluding restaurants and bars. Sometime in the latter part of 1997, the board began considering the possibility of regulating ETS in restaurants and bars. To this end, between 1997 and the spring of 1999, the board held several public meetings, reviewed studies on ETS, contacted environmental health authorities on the issue, and consulted with local restaurant businesses. Following these efforts, the board concluded “only two options would adequately protect public health: 1) either a complete ban on smoking in restaurants and bars; or 2) allowing restaurants and bars to construct enclosed smoking areas.”

The board drafted a proposed regulation prohibiting smoking in restaurants and bars except in limited, separately enclosed and ventilated seating areas. When the local restaurant industry indicated at a public hearing that it opposed the concept of separate smoking areas, the board redrafted the proposed regulation to impose the current absolute ban on smoking “in all food[*219] service establishments, lounges and bars.”^[4] Following a public hearing on the proposed ban, the board, pursuant to G. L. c. Ill, § 31, adopted the regulation on February 10, 2000. Prior to the regulation’s effective date (April 3, 2000), Tri-Nel Management, Inc., doing business as The Windjammer Lounge, and certain named investors, stockholders, employees, and operators of the business (plaintiffs) sought a preliminary injunction in the Superior Court, requesting the court to enjoin enforcement of the regulation.^[5] Denying the plaintiffs’ request for a preliminary injunction, a Superior Court judge determined that (1) the plaintiffs had failed to demonstrate a reasonable likelihood of success on the merits; (2) the plaintiffs also failed to show irreparable harm; and (3) issuance of the injunction would not serve the public interest. The plaintiffs appealed. We granted the plaintiffs’ application for direct appellate review.

2. Discussion. To succeed in an action for a preliminary injunction, a plaintiff must show (1) a likelihood of success on the merits; (2) that irreparable harm will result from denial of the injunction; and (3) that, in light of the plaintiff’s likelihood of success on the merits, the risk of irreparable harm to the plaintiff outweighs the potential harm to the defendant in granting the injunction. Packaging Indus. Group, Inc. v. Cheney, 380 Mass. 609, 617 (1980). When, as here, a party seeks to enjoin governmental action, the court also considers whether the relief sought will adversely affect the public. Commonwealth v. Mass. CRINC, 392 Mass. 79, 89 (1984), and cases cited. Biotti v. Selectmen of Manchester, 25 Mass. App. Ct. 637, 640 (1988). In reviewing an order on a preliminary injunction, we must determine whether the judge abused his discretion. Because no testimony was taken in the Superior Court hearing there is no credibility or factual issue on which we would defer to the judge. Packaging Indus. Group, Inc. v. Cheney, supra at 615-616.

We note initially that “in the absence of a contrary statutory direction, a court reviewing a regulation is not concerned with[*220] whether there was substantial evidence in a record before the agency, but rather . . . whether, based solely on the record made in court, the adoption of the agency regulation was illegal, arbitrary, or capricious” (emphasis supplied). Massachusetts State Pharmaceutical Ass’n v. Rate Setting Comm’n, 387 Mass. 122, 126 (1982). Accordingly, it is the record of the preliminary injunction proceeding with which we are concerned.

The plaintiffs present several arguments supporting their claim of a likelihood of success on the merits. They contend that the board’s regulation exceeds the authority granted by G. L. c. 111, § 31. We disagree. General Laws c. Ill, § 31, authorizes local boards of health to “make reasonable health regulations.” G. L. c. 111, § 31. We have previously recognized that the “statutory language itself is the principle source of insight into the legislative purpose.” Hoffman v. Howmedica, Inc., 373 Mass. 32, 37 (1977). Through the plain language of G. L. c. 111, § 31, the Legislature has delegated to boards of health the power to adopt reasonable health regulations.

The plaintiffs next argue that the board’s regulation is not reasonable because the amount of ETS exposure at restaurants and bars would not be sufficient to cause adverse health effects in general. In deciding whether a health regulation adopted under G. L. c. 111, § 31, is reasonable, this court accords the regulation the same deference granted to a legislative enactment. Druzik v. Board of Health of Haverhill, 324 Mass. 129, 138 (1949). Health regulations have a strong presumption of validity, and, when assessing a regulation’s “reasonableness,” all rational presumptions are made in favor of the validity of the regulation. Id. A court may invalidate the regulation only when there is no rational relation between the regulation and its stated public health purpose. Id. at 138-139. Hamel v. Board of Health of Edgartown, 40 Mass. App. Ct. 420, 423 (1996).^[6]

Reviewing the record in this case, we note that the plaintiffs did not offer any evidence in support of their contention that the ill effects of ETS exposure will not result from only limited contact. By contrast, the board has placed in the record four reports interpreting and summarizing scientific studies that identify ETS exposure as a cause of numerous negative health[*221] effects.^[7] Further, given the subject matter, the board’s expertise and experience in this area is given great deference by our courts. Massachusetts Inst. of Tech. v. Department of Pub. Utils., 425 Mass. 856, 867-868 (1997). Given the absence of any evidence from the plaintiffs, the scientific studies on the ill effects of ETS exposure generally, and the board’s expertise in this subject matter, we conclude that the board’s regulation is within the standard of reasonableness. Druzik v. Board of Health of Haverhill, supra at 138.

The plaintiffs also maintain that G. L. c. 111, § 31, limits the authority of boards of health to adopt regulations to specific subject matters enumerated in other sections of G. L. c. 111. For this proposition, the plaintiffs cite our decision in Commonwealth v. Drew, 208 Mass. 493 (1911). The Drew opinion, however, was issued in 1911, approximately nine years before[*222] the enactment of G. L. c. 111, § 31, and interpreted a different statute, Rev. L. c. 75, § 65 (1902), which gave more limited power to boards of health. Compare Commonwealth v. Drew, supra at 495 (analyzing Rev. L. c. 75, § 65 [1902]), with St. 1920, c. 591, § 17, enacting predecessor to G. L. c. 111, § 31, as amended by St. 1937, c. 285.^[8] Section 31 was “passed as legislation of broad and general scope . . . which is ‘not subject to the limitations of earlier rule mating powers of boards of health.’ ” Board of Health of Woburn v. Sousa, 338 Mass. 547, 551-552 (1959), quoting Brielman v. Commissioner of Pub. Health of Pittsfield, 301 Mass. 407, 409 (1938). We have said that, when the Legislature enacted G. L. c. 111, § 31, it created “a comprehensive, separate, additional source of authority for health regulations.” Board of Health of Woburn v. Sousa, supra at 550. Since the enactment of G. L. c. 111, § 31, we have repeatedly observed that this statute has granted boards of health plenary power to issue reasonable, general health regulations. Independence Park, Inc. v. Board of Health of Barnstable, 403 Mass. All, 480 (1988). United Reis Homes, Inc. v. Planning Bd. of Natick, 359 Mass. 621, 623 (1971). Moreover, we have previously recognized the ill effects of tobacco use, particularly when it involves minors, as a legitimate municipal health concern justifying municipal regulation of tobacco products. Patton v. Marlborough, 415 Mass. 750, 751-752 (1993) (upholding board of health regulation limiting operation of cigarette vending machines to certain locations where access by minors prohibited). Take Five Vending, Ltd. v. Provincetown, 415 Mass. 741, 748-749 (1993) (upholding bylaw forbidding sale of cigarettes from vending machines).

The plaintiffs further argue that the board’s regulation conflicts with existing legislation dealing with the same subject matter. They contend that existing legislation indicates legisla[*223] tive intent to preclude or preempt municipalities from acting in this area and that the enforcement of the regulation would frustrate the legislative purpose of these statutes, in violation of the Home Rule Amendment, art. 89, § 6, of the Amendments to the Massachusetts Constitution.^[9] The plaintiffs’ reference to the Home Rule Amendment is misplaced. When the Legislature enacted the Home Rule Amendment, it granted municipalities broad powers that the local governments did not hold prior to the amendment. See Board of Appeals of Hanover v. Housing Appeals Comm, in the Dep’t of Community Affairs, 363 Mass. 339, 358 (1973) (“The Home Rule Amendment grants cities and towns independent municipal powers which they did not previously inherently possess”). The Legislature restricted this grant of power by authorizing municipalities to exercise the power only to the extent that it “is not inconsistent with the constitution or laws enacted by the general court.” Art. 89, § 6.

The plaintiffs contend that the board’s regulation conflicts with the Legislature’s existing statutory regulation of tobacco products. Citing G. L. c. 270, § 22, as indicative of legislative intent to protect restaurants against regulations that prohibit smoking, the plaintiffs maintain that the regulation is in “direct conflict” with the provisions of that statute. In assessing whether a reasonable health regulation is inconsistent with a State statute, we will afford the local board “ ‘considerable latitude,’ requiring a ‘sharp conflict’ between the [regulation] and the statute before invalidating the [regulation].” Take Five Vending, Ltd. v. Provincetown, supra at 744, quoting Bloom v. Worcester, 363 Mass. 136, 154 (1973). See Patton v. Marlborough, supra at 751-752 (same conflict analysis applies to regulations promulgated by boards of health). “Such a conflict ‘appears when either the legislative intent to preclude local action is clear, or, absent plain expression of such intent, the purpose of the statute cannot be achieved in the face of the local [regulation].’ ” Take Five Vending, Ltd. v. Provincetown, supra at 744, quoting Grace v. Brookline, 379 Mass. 43, 54 (1979).

General Laws c. 270, § 22, inserted by St. 1987, c. 759, § 3,[*224] prohibits smoking in court houses, schools, colleges, universities, museums, libraries, trains, airplanes, waiting areas of airports or health care facilities, any public building, and other various locations, except in a limited area specifically designated as a smoking area. Section 22 also restricts smoking in restaurants as follows:

“No person shall smoke in any restaurant with a seating capacity of seventy-five or more persons, except in an area which has been specifically designated as a smoking area. In such case, smoking may be permitted in an area or areas that have been specifically designated by notice or sign, only if nonsmoking areas of sufficient size and capacity are available to accommodate nonsmokers. Smoking and nonsmoking areas in any restaurant need not be separated by walls, partitions or other physical barriers; provided, however, that nonsmoking areas in any part of a restaurant, as provided herein, shall be no less than two hundred square feet of floor space.”

When the Legislature enacted St. 1987, c. 759, it provided that nothing in the act prevented municipalities from regulating smoking more strictly in public places: “Nothing in this act shall be construed to permit smoking in any area in which smoking is or may hereafter be prohibited by law including, without limiting the generality of the foregoing, any other provision of the law or ordinance or by-law or any fire, health or safety regulation.” St. 1987, c. 759, § 5.

Thus, § 5 specifically authorizes municipalities to impose additional regulation on areas covered by the statute. In addition, the statutory language of G. L. c. 270, § 22, itself defeats an assertion of preemption. See Hoffman v. Howmedica, Inc., 373 Mass. 32, 37 (1977) (“statutory language itself is the principal source of insight into the legislative purpose”).^[10] General Laws c. 270, § 22, sets forth minimum Statewide restrictions on[*225] smoking in restaurants to protect and accommodate the nonsmoking public. The board’s ban placing additional restrictions on smoking furthers, rather than frustrates, this intent. Accordingly, the board’s regulation does not conflict with G. L. c. 270, § 22. ‘

The plaintiffs’ next contention is that the Legislature’s delegation of regulatory authority to local boards of health in G. L. c. Ill, § 31, violates art. 30 of the Massachusetts Declaration of Rights, which provides for governmental separation of powers. “The doctrine of separation of powers encompasses the general principle that the Legislature cannot delegate the power to make laws.” Construction Indus, of Mass. v. Commissioner of Labor & Indus., 406 Mass. 162, 171 (1989). Whether a particular delegation of power is proper is “a question of degree.” Id. See Opinion of the Justices, 328 Mass. 674, 676 (1952) (“principle that legislative power cannot be delegated is not . . . applied in all instances with absolute literal inflexibility”). In reviewing a claim of improper delegation of legislative power, we consider: “(1) Did the Legislature delegate the making of fundamental policy decisions, rather than just the implementation of legislatively determined policy; (2) does the act provide adequate direction for implementation, either in the form of statutory standards or, if the [local authority] is to develop the standards, sufficient guidance to enable [it] to do so; and (3) does the act provide safeguards such that abuses of discretion can be controlled?” Construction Indus, of Mass. v. Commissioner of Labor & Indus., supra, quoting Chelmsford Trailer Park, Inc. v. Chelmsford, 393 Mass. 186, 190 (1984).

The board’s regulation satisfies these standards. First, the Legislature has made the policy decision that public health matters affecting local communities may be the subject of reasonable municipal regulations. G. L. c. 111, § 31. The appropriateness of this delegation is rooted in the legal history of this[*226] Commonwealth. See Baker v. Boston, 12 Pick. 184, 192-193 (1831) (noting validity of power held by municipalities to preserve “public health”); Brodbine v. Revere, 182 Mass. 598, 601 (1903) (noting validity of legislation delegating regulatory authority on public health matters to local boards of health “has long been recognized”). Further, with specific regard to ETS regulation, the Legislature has already made the determination that smoking should be prohibited or regulated in certain public locations, including restaurants, see G. L. c. 270, § 22, and has explicitly left municipalities, and their boards of health, the power to implement stricter regulations on smoking in public places. See St. 1987, c. 759, § 5.

Second, in view of the long-standing tradition of municipal regulation of local health matters, the Legislature has provided appropriate guidance for the implementation of regulations by requiring that they address the “health” of the community and that they be “reasonable.” Chelmsford Trailer Park, Inc. v. Chelmsford, supra at 190 (“Legislature may delegate to a board ... the details of a policy adopted by the Legislature”). Bay State Harness Horse Racing & Breeding Ass’n v. State Racing Comm’n, 342 Mass. 694, 699 (1961) (although statute furnished “few specific standards,” delegation valid where general standards of “public interest, convenience, and necessity” could be implied). Burnham v. Board of Appeals of Gloucester, 333 Mass. 114, 118 (1955), and cases cited (degree of certainty with which standards for exercise of discretion are set up depends on subject matter and circumstances). In regard to the third consideration, these limitations on content and reasonableness sufficiently demarcate the boundaries of regulatory discretion so that the act provides safeguards to control abuses of discretion. Parties who believe that a board’s regulation has exceeded proper boundaries may seek judicial review of the regulation, pursuant to an action for declaratory relief. G. L. c. 231 A.^[11]

Finally, the plaintiffs assert that the board’s regulation violates the town’s charter. Section 1-3 of the charter, entitled “Division of Powers,” declares “[a]ll legislative powers of the town shall be exercised by a town council.” The charter further provides,[*227] however: “Except as otherwise provided by law or by the charter, all powers of the town shall be vested in the town council which shall provide for their exercise and for the performance of all duties and obligation [sic\ imposed on the town by law” (emphasis added). Charter of the Town of Barn-stable § 2-3. In 1991, the Barnstable town council adopted an administrative code, which the charter defines as “a written description of the administrative organization of town offices, departments and multiple member bodies. The administrative code shall state the . . . general powers and duties of each town office department and multiple member body.” § 9-4(a). The code provides that “regulatory” standing committees have “legal authority to promulgate rules and regulations, decide individual cases and enact policy.” Barnstable Administrative Code § 1.09(b). Section 16 of the code establishes the board as a standing committee, defining the board as “an advisory and regulatory committee of the Town.” Barnstable Administrative Code §§ 16.01-16.02.^[12] Accordingly, the town council, much like the Legislature, has delegated regulatory authority to the board to preserve and protect the town’s public health.^[13] For the foregoing reasons, we conclude that the Superior Court judge properly ruled that the plaintiffs failed to demonstrate a likelihood of success on the merits.

That the plaintiffs failed to establish a likelihood of success on the merits of their claim is sufficient to deny injunctive relief. We note that the plaintiffs also failed to show irreparable harm and that they failed to show that issuance of the injunction would serve the public interest. The plaintiffs have argued in their application for a preliminary injunction that the smoking ban would interfere with existing customer relationships and cause a loss of business income. Economic harm alone,[*228] however, will not suffice as irreparable harm unless “the loss threatens the very existence of the movant’s business.” Hull Mun. Lighting Plant v. Massachusetts Mun. Wholesale Elec. Co., 399 Mass. 640, 643 (1987). There is no suggestion to that effect. The only evidence on this issue consisted of two statistical studies offered by the board showing that smoking restrictions in restaurants and bars had little to no effect on restaurant revenues. A 1997 study by the Center for Health Economics Research entitled, Effect of Local Smoke-Free Restaurant Policies on Restaurant Revenue in Massachusetts,^[14] reported preliminary findings that “[t]here is no support for the hypothesis that restaurant smoking restrictions reduced restaurant receipts.”^[15] Finally, in light of the scientific support linking ETS to adverse health effects, the Superior Court judge properly determined that the issuance of an injunction would not serve the public interest.

The Superior Court order denying the plaintiffs’ request for a preliminary injunction is affirmed.

So ordered.

Justice Abrams participated in the deliberation on this case, but retired before the opinion was issued.