Full opinion text
Opinion MOSK, J. Section 1759 of the Public Utilities Code declares that no court except this Supreme Court has jurisdiction to review any order or decision of the Public Utilities Commission (hereafter the commission) or to interfere with the commission in the performance of its duties. Section 2106, however, authorizes an action in superior court for damages caused by any unlawful act of a public utility. In Waters v. Pacific Telephone Co. (1974) 12 Cal.3d 1, 4 [114 Cal.Rptr. 753, 523 P.2d 1161], this court held that “in order to resolve the potential conflict between sections 1759 and 2106, the latter section must be construed as limited to those situations in which an award of damages would not hinder or frustrate the commission’s declared supervisory and regulatory policies.” We granted review in this case to determine whether section 1759 as construed in Waters bars a superior court action for property damage allegedly caused by the electric and magnetic fields arising from powerlines owned and operated by a public utility. We shall conclude that such an action would impermissibly interfere with a broad regulatory policy of the commission on this subject, and hence is barred by section 1759 as construed in Waters. We therefore affirm the judgment of the Court of Appeal so holding. Background “Although ‘electric and magnetic fields’ may sound mysterious or ominous to some people, scientists have had a good understanding of them since the nineteenth century.” (U.S. Cong., Office of Technology Assessment, Biological Effects of Power Frequency Electric and Magnetic Fields (1989) p. 4 (hereafter OTA Report).) To begin with, “Electric and magnetic fields arise from many natural sources. They appear throughout nature and in all living things.” (OTA Rep., supra, at p. 4.) The Earth has a strong magnetic field arising from the rotation of its inner core. Atmospheric forces cause large electric fields at the Earth’s surface during thunderstorm activity. Certain minerals in the Earth’s crust, particularly iron and its compounds, have magnetic properties and give rise to magnetic fields. And at the human level, the body itself is a strong source of internal electric fields: “all cells in the body maintain large natural electric fields across their outer membranes. These naturally occurring fields are at least 100 times more intense than those that can be induced by exposure to common power-frequency fields.” {Id. at p. 1.) Indeed, this phenomenon is essential to life: “cells, especially those in the nervous system, make use of complex electrochemical processes in their normal function.” (Id. at p. 2.) Since the development of commercial and domestic uses of electricity in the last century, many manmade sources of electric and magnetic fields have been added to the foregoing natural sources. They arise primarily from the electric power systems that generate and deliver electricity to factory, office, and home, and from the machinery, appliances, and lighting that electricity operates. The scientific explanation for all electric and magnetic fields, however, is the same. Every constituent of matter has an electric charge, which is either positive or negative. Charges that are alike (two positive or two negative charges) repel each other, while opposite charges (one positive and one negative charge) attract; this is the electric force. The electric force acts along a line between the two charges, and its strength is inversely proportional to the square of the distance between them: e.g., if the distance between the two charges is doubled, the force of attraction or repulsion becomes weaker by a factor of four, decreasing to one-quarter of its original strength. Every charge has an electric field, which is the region of space in which the charge is capable of exerting, at a distance, an electric force of attraction or repulsion on any other charge. The electric field always begins on a positive charge and ends on a negative charge. Like the electric force, the strength of the electric field diminishes with distance from the source of the field. When an electric charge is moving, however, it creates a different and additional force on any other charge in its vicinity, provided the second charge is also moving: this is the magnetic force. Like the electric force, the strength of the magnetic force diminishes with distance. Every moving charge likewise has a magnetic field, which is the region of space in which the charge is capable of exerting, at a distance, a magnetic force on any other moving charge. The magnetic field is more complex than the electric field: for example, the magnetic field does not have a beginning or an end, but forms closed, continuous loops of force around the source of the field. Like the electric field, however, the strength of the magnetic field also diminishes with distance. An electric current is a group of charges moving in the same direction through a wire or other conductor. Voltage is the difference in electric potential that causes the charges to flow through the wire; it is analogous to the pressure in a water pipe before the faucet is opened (e.g., in pounds per square inch), and is measured in volts (V) or, in the case of powerlines, in thousands of volts or kilovolts (kV). Current is the rate at which the charges flow through the wire; it is analogous to the rate at which water flows through a pipe after the faucet is opened (e.g., in gallons per minute), and is measured in amperes. The quantity of power (in watts) that a conducting wire transmits is thus the product of its voltage and its current. Power systems are designed to hold the voltage relatively constant but to meet fluctuating demand by allowing the current to rise and fall. The strength or intensity of an electric field is proportional to its voltage, and is measured in volts per meter or in kilovolts per meter. The strength of a magnetic field is primarily proportional to its current; the most commonly used unit of measurement of the strength of a magnetic field—or more properly, of “magnetic flux density”—is the gauss. Because the gauss is a large unit, such fields are often measured in thousandths of a gauss or milligauss (mG). Electric fields are affected by objects in the environment, especially objects that conduct electricity: some of the field lines will end on charges in the object. For example, buildings, tall fences, and even trees can partially block electric fields arising from nearby powerlines. Magnetic fields, by contrast, pass through most objects and can be blocked only by special shielding materials. Electric and magnetic fields affect conducting objects in the environment by the dual processes of electric and magnetic induction. Such fields cause charges to flow in conducting objects; the resulting currents are said to be induced by the fields. The human body is a conducting object because it contains free electric charges, largely in such fluids as the blood and the lymph. When a human body is in an electric or a magnetic field, therefore, the field induces a current in the body. Electrically induced currents and magnetically induced currents flow in different patterns in the body and the strength of each depends on a variety of factors, but each is far weaker than the body’s natural currents. Naturally occurring electric and magnetic fields, such as the Earth’s magnetic field, are static. Fields arising from powerlines oscillate, because the current in powerlines does not flow steadily in one direction (direct current) but flows alternately first in one direction and then in the other (alternating current). In the United States and Canada, the flow of current in electric powerlines reverses direction 60 times each second: the power is therefore said to have a frequency of 60 cycles per second, or 60 hertz (Hz). In turn, this oscillation causes the electric and magnetic fields arising from the powerlines to likewise reverse their direction 60 times each second; they are therefore said to be 60-hertz fields or power-frequency fields. Sixty-hertz fields are also called extremely low-frequency fields, for the following reason. Such fields are only one form of the energy known as electromagnetic radiation. That energy, which is both natural and manmade in origin, has a wide variety of effects on matter depending on its frequency: the higher the frequency, the shorter the wavelength and the greater the energy. The frequencies of different forms of electromagnetic energy extend over an enormous range, commonly represented as a spectrum. At one end of the electromagnetic spectrum are X-rays and gamma rays, which have extremely high frequencies (1016 Hz to 1025 Hz and above) and hence extremely high energy. Next on the electromagnetic spectrum is ultraviolet light, which has somewhat lower frequencies (1015 Hz to 1016 Hz) and hence somewhat lower energy. Below it is the familiar spectrum of visible light, followed in sequence by infrared waves, microwaves (1 billion Hz to 300 billion Hz), and television and radio waves (500,000 Hz to 1 billion Hz). Although each of these has progressively lower frequencies and energy, even the lowest (AM radio) has a frequency range of 500,000 Hz (500 kHz) to 1.6 million Hz (1600 kHz). Lowest of all on the electromagnetic spectrum are electric and magnetic fields such as those arising from the powerlines in this case. When their frequency of a mere 60 Hz is compared with the frequency of the other forms of electromagnetic energy, it is evident why they are called “extremely low frequency” fields. An important consequence of the low frequency and resulting low energy of electric and magnetic fields is that they are non-ionizing. An atom or molecule is said to be ionized when one or more of its electrons is dislodged by an energetic outside force such as very high-frequency radiation. Gamma rays, X-rays, and high-frequency ultraviolet light are termed ionizing radiation because their energy is so great that they are capable of ionizing atoms or molecules of ordinary matter. When that matter is human tissue, ionization can damage the DNA molecules of the cells, causing mutations and various forms of cancer. “However, the energy carried in 60 Hz fields is much too small to break molecular or chemical bonds.” (Carnegie Mellon Rep., supra, at p. 9, italics in original.) Like visible light, infrared, microwaves, and television and radio waves, electric and magnetic fields are therefore termed non-ionizing radiation. One form of non-ionizing radiation—microwaves—can nevertheless cause biological damage by a different process: microwaves are absorbed by the water present in tissue, and can induce currents strong enough to heat the tissue. But “While 60 Hz fields can also set up currents in tissue, these currents are much weaker. The amount of heat they generate is trivial compared to the natural heat that comes from the cells of the body. There is no reason to believe that health effects can be caused by such minuscule amounts of heat.” (Carnegie Mellon Rep., supra, at p. 9; accord, OTA Rep., supra, at p. 1; DHS Rep., supra, at p. 3.) Because 60 Hz electric and magnetic fields are non-ionizing and cannot cause significant tissue heating, it was long believed they could not have any effect on human health. Beginning in the mid-1970’s, however, laboratory studies on cell cultures showed that these fields can affect certain activities of certain types of cells. Although the results were suggestive, several serious problems remained. First, there was no known mechanism to explain how these extremely weak fields could disturb the much stronger fields arising naturally from human cell activity. Second, disturbances at the cellular level do not necessarily extrapolate to adverse effects on the organism as a whole: the organism can tolerate some disturbances and compensate for others. Biological effects, in short, are not always harmful. Third, the dose-response relationship was unknown. With most environmental hazards, e.g., toxic chemicals, the higher the dose, the greater the response or effect. But this did not appear to be true of electric and magnetic fields: a number of the laboratory studies observed biological effects only in narrow ranges of field strength, frequency, or length of exposure; above and below those ranges there were no effects. Contrary to expectation, therefore, in such cases weaker fields would not necessarily be “safer” than stronger fields. (OTA Rep., supra, at pp. 19-20; Carnegie Mellon Rep., supra, at pp. 21-23; DHS Rep., supra, at p. 6; EPA Q&A, supra, at pp. 3-4.) In addition, beginning in the late 1970’s the results of some epidemiological studies suggested a statistically significant relationship between 60 Hz electric and magnetic fields and certain forms of cancer in certain populations. Again problems arose, however, as the design, execution, and interpretation of these studies were challenged on a number of grounds: e.g., the population samples were small and the types of cancer studied were relatively rare; the field strengths were not measured directly but were indirectly inferred from past proximity to powerlines or from the job titles or descriptions; and the studies did not control for exposure to other known or potential carcinogens. (See generally, OTA Rep., supra, at pp. 57-66; Carnegie Mellon Rep., supra, at pp. 16-18; DHS Rep., supra, at pp. 4-5; EPA Q&A, supra, at p. 2.) In short, by the early 1980’s the question whether powerline electric and magnetic fields pose a danger to health had become a matter of some public concern and a source of growing controversy in the scientific community. The stage was set for intervention by the commission; as will appear, that process began in earnest in 1988. (Pt. IV, post.) Before continuing this history, however, we make two final preliminary points. First, it will be helpful to understand the basic components of the electric power “grid” or system. Powerplant generators deliver electric power to the system at approximately 20 kV. “Step-up” transformers increase that voltage to higher levels for transmission purposes, because the higher the voltage, the less power lost in the wires. The power is then carried long distances over transmission lines at voltages that range between 50 kV and 765 kV. Transmission lines terminate at substations, where “step-down” transformers reduce the voltage for distribution purposes. The power is then carried shorter distances over various types of distribution lines, at various voltages below 50 kV, to the ultimate users. By the time the power is delivered to the residential user, its voltage has been reduced to the household level of 120/240 V. Second, it is important to stress that electric and magnetic fields arise not only from powerlines but also from the distribution and use of that power inside the home, office, or factory. One common source of such fields is the wall and ceiling wiring of the building itself, which delivers the electricity to the individual rooms in which it is used for lighting, heating, or operating appliances. Although the magnetic fields of modem wall and ceiling wiring are small, older wiring “can make significant contributions to the average magnetic field in homes.” (OTA Rep., supra, at p. 15.) Another source, often overlooked, is the “ground currents” that flow through the water pipes, gas lines, or steel framing typically used for grounding the wiring system of the building: “the magnetic fields that they produce can contribute substantially to the overall magnetic field in homes.” (Ibid.) A third common source of electric and magnetic fields is electric equipment and appliances. In the factory, this means all machines and tools powered by electricity—in other words, virtually all industrial machinery in use today. In the office, this means fluorescent light fixtures and all such equipment as computers, video display terminals, printers, copiers, typewriters, and fax machines. In the home, this means television sets, videocassette recorders, compact disc players, radios, table lamps, vacuum cleaners, power tools, portable heaters, electric blankets, electric shavers, hair dryers, clothes washers and dryers, irons, electric ovens and ranges, refrigerators and freezers, as well as toasters, coffeemakers, food processors, and all other small kitchen appliances. “The most intense magnetic fields in the home are found near appliances (particularly those with small motors or transformers such as hairdryers and fluorescent light fixtures).” (OTA Rep., supra, at pp. 14-15.) Although they are probably not the main source of the magnetic background because their fields decrease rapidly with distance and users generally spend only brief periods of time operating such appliances (with the exception of electric blankets and television sets), they are ubiquitous in the modem home. To sum up, “There are electric and magnetic fields wherever there is electric power.” (OTA Rep., supra, at p. 1.) In the typical home, fields of various strengths arise from the wall and ceiling wiring, the ground currents, and all electric machinery, equipment, and appliances: “Keeping fields out of the home would mean keeping any electricity from coming into or being used in the home.” (EPA Q&A, supra, at p. 16, italics added.) And because the sources of electric and magnetic fields inside the home are so numerous, “Occupants of the average household are probably exposed to higher fields from their house wiring and appliances than from the outside wiring,” i.e., from powerlines. (Ibid.) With this background in mind, we turn to the facts of the case at bar. I On December 16, 1993, plaintiffs Martin and Joyce Covalt filed the present action for damages and injunctive relief against San Diego Gas and Electric Company (SDG&E). The complaint alleges that plaintiffs own and occupy a single-family residence in San Clemente, California, and SDG&E owns an easement on the land adjacent to their property. The complaint further alleges that SDG&E runs electric currents through powerlines on that easement which are “in very close proximity to and placed upon plaintiffs’ property, and because of this have continuously omitted [sic] high and unreasonably dangerous levels of electromagnetic radiation onto plaintiffs’ property.” The complaint also alleges that in February 1990 SDG&E “substantially increased the number of Powerlines housed in the easement adjacent to plaintiffs’ property. Such increase in Powerlines dramatically increased the dangerous levels of electromagnetic radiation flowing onto plaintiffs’ property.” The complaint does not specify the voltage of the powerlines in question, nor their number, configuration, and electric and magnetic field levels before and after the 1990 upgrading. In their memorandum of points and authorities filed in support of their return, however, plaintiffs state additional facts taken from a letter sent to them by SDG&E on January 5, 1993, to wit, that prior to July 1990 the SDG&E easement adjacent to their property, dating from 1928, carried two 12 kV distribution circuits (requiring a total of 7 wires) on crossbars mounted on single poles; between February and July 1990 a third 12 kV distribution circuit (requiring 4 wires) was added in response to increased customer demand for power; to accommodate the third circuit, the single poles were replaced by double poles standing 12 feet apart and joined by longer crossbars. Exhibits attached to the SDG&E letter show that before July 1990 the crossbars extended 5 and 6 feet from the center line of the pole towards plaintiffs’ property, and after July 1990 the crossbars extended 8.5 feet from the center line towards plaintiffs’ property. Thus the effect of the reconfiguration was to move portions of the 3 circuits either 2.5 feet or 3.5 feet closer to plaintiffs’ house. The closest point of plaintiffs’ house, however, was 68 feet from the center line of either pole configuration. The SDG&E letter estimated that the average magnetic field level at that point was 5 mG before 1990 and was anticipated to be approximately 8.9 mG in 1993, for an average increase of approximately 3.9 mG. Plaintiffs furnish no figures for the electric field levels at that point. In the same points and authorities plaintiffs state that they purchased the house in question in 1990, but do not specify when in that year they did so; they also state that they have since vacated the house and the property “has been foreclosed upon by the mortgagor.” The remaining factual allegations of the complaint do not pertain to the case at bar. The complaint first alleges five causes of action for personal injury, seeking to recover damages for “medical monitoring” (count 1), intentional infliction of emotional distress (count 2), negligent infliction of emotional distress (count 3), strict product liability (count 4), and negligent product liability (count 5). The complaint next alleges three causes of action for property damage, i.e., trespass (count 6), nuisance (count 7), and inverse condemnation (count 8). Lastly, the complaint alleges a cause of action for injunctive relief, seeking an order requiring SDG&E to “discontinue the admissions [sz'c] of electromagnetic radiation onto or adjacent to plaintiffs’ property.” SDG&E demurred to the complaint on the ground that the court lacks subject-matter jurisdiction (Code Civ. Proc., § 430.10, subd. (a)) because a judgment for plaintiffs on any count would hinder or frustrate a general regulatory policy of the commission and hence the action is barred by section 1759 as construed in Waters v. Pacific Telephone Co., supra, 12 Cal.3d 1, and related cases. SDG&E also demurred on the ground that on each of the counts the complaint failed to state facts sufficient to constitute a cause of action. (Code Civ. Proc., § 430.10, subd. (e).) The demurrer was overruled. SDG&E thereupon filed a petition for writ of prohibition or mandate in the Court of Appeal, seeking an order directing the trial court to sustain the demurrer and dismiss the complaint. The Court of Appeal granted an alternative writ and stayed all proceedings. In its ensuing decision the Court of Appeal correctly observed at the outset that an order overruling a demurrer is not directly appealable but may be reviewed on an appeal from the final judgment (Code Civ. Proc., §§ 9Ó4.1, 906), and that such an appeal is normally presumed to be an adequate remedy at law, thus barring immediate review by extraordinary writ (id., §§ 1086, 1103). The Court of Appeal then held, however, that the case at bar falls within the exception to this rule that has been recognized when the demurrer raises an important question of subject-matter jurisdiction; in that event, courts have held it proper to review the order overruling the demurrer by means of extraordinary writ. (See, e.g., County of Sacramento v. Superior Court (1972) 8 Cal.3d 479, 481 [105 Cal.Rptr. 374, 503 P.2d 1382] [prohibition]; State of California v. Superior Court (1984) 150 Cal.App.3d 848, 853, fn. 4 [197 Cal.Rptr. 914] [mandate]; County of Santa Barbara v. Superior Court (1971) 15 Cal.App.3d 751, 754-755 [93 Cal.Rptr. 406] [prohibition].) The parties do not question this holding. Turning to the merits, the Court of Appeal first addressed the five personal injury causes of action of the complaint. The court observed that in these causes of action plaintiffs do not allege that they have been physically harmed by the electric and magnetic fields arising from SDG&E’s power-lines, but only that they have experienced emotional distress because they fear that in the future they may contract cancer or other serious disease as a result of their exposure to such fields. In these circumstances the Court of Appeal relied on the holding of this court in Potter v. Firestone Tire & Rubber Co. (1993) 6 Cal.4th 965, 997 [25 Cal.Rptr.2d 550, 863 P.2d 795] (hereafter Potter) that “damages for fear of cancer may be recovered only if tiie plaintiff pleads and proves that (1) as a result of the defendant’s negligent breach of a duty owed to the plaintiff, the plaintiff is exposed to a toxic substance which threatens cancer; and (2) the plaintiff’s fear stems from a knowledge, corroborated by reliable medical or scientific opinion, that is more likely than not that the plaintiff will develop the cancer in the future due to the toxic exposure.” (First italics in original, second italics added.) Applying this rule, the Court of Appeal held that plaintiffs failed to plead any facts to meet the second prong of the Potter test, i.e., that “reliable medical or scientific opinion” corroborates their belief that it is probable that they will in fact develop cancer in the future from exposure to the electric and magnetic fields arising from SDG&E’s powerlines. For this reason the court held that the complaint failed to state a cause of action on the personal injury counts. The Court of Appeal then stressed that throughout their briefs plaintiffs concede they are no longer asserting that electric and magnetic fields are in fact harmful: in their return, for example, plaintiffs state that their claims “do not rest upon the assertion that EMF [electric and magnetic fields] is [sic] a scientifically proven health hazard,” and in their accompanying points and authorities plaintiffs acknowledge they “do not claim that medical science has proven that EMF cause cancer and are thus hazardous to human beings.” Rather, as will appear, plaintiffs contend primarily that a public fear of such fields—regardless of whether or not that fear is reasonable or scientifically supported—has diminished the value of their real property. For this reason the Court of Appeal held that plaintiffs cannot amend their complaint to sufficiently plead their causes of action for personal injury; as to those causes of action, therefore, the demurrer should have been sustained without leave to amend. The Court of Appeal then addressed the three property damage causes of action of the complaint. The court began by recognizing the broad powers granted to the commission by Constitution and statute. From section 1759 and Waters v. Pacific Telephone Co., supra, 12 Cal.3d 1, the court drew the rule that if the Covalt action would conflict with a general regulatory policy of the commission regarding powerline electric and magnetic fields, the superior court would lack jurisdiction to proceed. The Court of Appeal then identified such a commission policy, expressed in several of its rulings and culminating in a decision on the specific question issued in 1993. Applying the Waters rule, the court concluded that a judgment on any of the three property damage causes of action would hinder and frustrate that commission policy. The court therefore issued a writ of mandate directing the trial court to vacate its order overruling the demurrer and to enter a new order sustaining the demurrer without leave to amend. We granted review. II “The commission is a state agency of constitutional origin with far-reaching duties, functions and powers. (Cal. Const., art. XII, §§ 1-6.) The Constitution confers broad authority on the commission to regulate utilities, including the power to fix rates, establish rules, hold various types of hearings, award reparation, and establish its own procedures. (Id., §§ 2, 4, 6.) The commission’s powers, however, are not restricted to those expressly mentioned in the Constitution: ‘The Legislature has plenary power, unlimited by the other provisions of this constitution but consistent with this article, to confer additional authority and jurisdiction upon the commission . . . .’ (Cal. Const., art. XII, § 5.)” (Consumers Lobby Against Monopolies v. Public Utilities Com. (1979) 25 Cal.3d 891, 905 [160 Cal.Rptr. 124, 603 P.2d 41], italics added.) Pursuant to this constitutional provision the Legislature enacted, inter alia, the Public Utilities Act. (§ 201 et seq.) That law vests the commission with broad authority to “supervise and regulate every public utility in the State” (§ 701) and grants the commission numerous specific powers for the purpose. Again, however, the commission’s powers are not limited to those expressly conferred on it: the Legislature further authorized the commission to “do all things, whether specifically designated in [the Public Utilities Act] or in addition thereto, which are necessary and convenient” in the exercise of its jurisdiction over public utilities. (Ibid., italics added.) Accordingly, “The commission’s authority has been liberally construed” (Consumers Lobby Against Monopolies v. Public Utilities Com., supra, 25 Cal.3d 891, 905, citing cases), and includes not only administrative but also legislative and judicial powers (People v. Western Air Lines, Inc. (1954) 42 Cal.2d 621, 630 [268 P.2d 723]). The Constitution also confers plenary power on the Legislature to “establish the manner and scope of review of commission action in a court of record” (Cal. Const., art. XII, § 5). Pursuant to this constitutional provision the Legislature enacted article 3 of chapter 9 of the Public Utilities Act, entitled “Judicial Review.” (§ 1756 et seq.) That article prescribes a method of judicial review that is narrow in both “manner and scope.” It is narrow in manner because review of a commission decision may be obtained only by filing a petition for writ of review directly in this court—bypassing the Court of Appeal—within 30 days after the commission denies rehearing or issues a decision on rehearing. (§§ 1756, 1758.) And it is narrow in scope because such review is limited to determining the legal question “whether the commission has regularly pursued its authority” (§ 1757); except when a federal constitutional challenge is raised (§ 1760), the commission’s findings and conclusions on questions of fact—including ultimate facts and determinations of reasonableness and discrimination—“shall be final and shall not be subject to review” (§ 1757). Having thus vested this court with limited jurisdiction to review commission actions, the Legislature then made it clear in section 1759 of the Public Utilities Act that no other court has jurisdiction either to review or suspend the commission’s decisions or to enjoin or otherwise “interfere” with the commission’s performance of its duties: section 1759 declares in relevant part that “No court of this State, except the Supreme Court to the extent specified in this article, shall have jurisdiction to review, reverse, correct, or annul any order or decision of the commission or to suspend or delay the execution or operation thereof, or to enjoin, restrain, or interfere with the commission in the performance of its official duties, . . (Italics added.) In the case at bar we are required once again to reconcile the foregoing provision of section 1759 with another provision of the Public Utilities Act, section 2106. The Legislature enacted section 2106 as part of a different chapter of the act, chapter 11. (§ 2100 et seq.) That chapter, entitled “Violations,” prescribes a wide variety of remedies designed to redress violations of commission decisions committed by public utilities. All but one of these are public remedies prosecuted in the name of the people of the state by commission counsel or by the Attorney General or the appropriate district attorney. (§2101.) They include: orders to common carriers to collect undercharges or unlawful rebates (§ 2100), actions for mandamus or injunction (§§ 2102-2103), actions to recover penalties (§§2104, 2107, 2111, 2115), imposition by the commission of fines with interest (§2107.5), criminal prosecutions (§§2110, 2112, 2114, 2119), and contempt proceedings (§2113). The sole private remedy authorized by chapter 11 is found in section 2106. That section supplements the foregoing public remedies by authorizing the traditional private remedy of an action for damages brought by the injured party in superior or municipal court against any public utility that does any act prohibited—or omits to do any act required—“by the Constitution, any law of this State, or any order or decision of the commission” (§2106). The supplemental nature of this remedy is further shown by the fact that the statute declares that no recovery of such private damages “shall in any manner affect a recovery by the State of the penalties provided in this part or the exercise by the commission of its power to punish for contempt.” (Ibid.) When sections 1759 and 2106 are thus seen in their respective statutory contexts, it is easier to understand how this court reconciled the potential conflict between them in the leading case of Waters v. Pacific Telephone Co., supra, 12 Cal.3d 1 (hereafter Waters). There the plaintiff, a real estate broker, filed an action for damages in superior court against the defendant Pacific Telephone Company (Pacific) pursuant to section 2106. The plaintiff alleged that she had experienced a number of interruptions and failures of telephone service caused by a variety of negligent acts on the part of Pacific, including improper installation and removal of telephones, incompleted calls, and inadequate maintenance. Pacific’s tariff, approved by the commission, limited its liability for interruptions and failures of service caused by acts of ordinary negligence to a credit allowance not exceeding the customer’s total fixed charges for the billing period in question. Pacific moved for partial summary judgment limiting its liability to that amount; the trial court granted the motion, and when the plaintiff waived her right to recover that amount, the court entered a nonsuit for Pacific. This court affirmed the judgment, undertaking for the first time to reconcile sections 1759 and 2106. The court began by stressing the broad supervisory and regulatory powers of the commission. (Waters, supra, 12 Cal.3d 1, 6.) It then observed that the commission was authorized by law to require utilities to file tariffs and to regulate their contents. The court next emphasized that several years earlier the commission had conducted “an extensive investigation of the general question of [the] limitation of liability by telephone utilities, and in its subsequent decision the commission made it clear that the credit allowance device has always been considered to be a rule limiting the utility’s liability.” (Id. at p. 8.) In that decision the commission determined “as a matter of policy” (ibid.) that telephone utilities should be at least partially liable for gross negligence but that the rules limiting liability for ordinary negligence in respect to service were reasonable. Accordingly, the commission required all telephone utilities to incorporate into their tariffs a provision limiting their liability for service interruption to specified credit allowances, and the commission took such limitations into account in exercising its ratemaking functions. (Id. at pp. 8-9.) Addressing the question of statutory construction, this court declared the primacy of section 1759 and the correspondingly limited role of section 2106. The court held that “in order to resolve the potential conflict between sections 1759 and 2106, the latter section must be construed as limited to those situations in which an award of damages would not hinder or frustrate the commission’s declared supervisory and regulatory policies.” (Waters, supra, 12 Cal.3d at p. 4, italics added.) The court reasoned (id. at p. 11) that “Plaintiff maintains that section 2106, in permitting damage actions against utilities for their unlawful acts, authorizes the instant action in spite of the language and policy underlying section 1759. Yet the two sections must be construed in a manner which harmonizes their language and avoids unnecessary conflict. Section 2106 reasonably may be interpreted as authorizing only those actions which would not interfere with or obstruct the commission in carrying out its own policies.” Under the Waters rule, accordingly, an action for damages against a public utility pursuant to section 2106 is barred by section 1759 not only when an award of damages would directly contravene a specific order or decision of the commission, i.e., when it would “reverse, correct, or annul” that order or decision, but also when an award of damages would simply have the effect of undermining a general supervisory or regulatory policy of the commission, i.e., when it would “hinder” or “frustrate” or “interfere with” or “obstruct” that policy. This court applied the foregoing rule to affirm the judgment of nonsuit in Waters, supra, 12 Cal.3d 1, despite the fact that the plaintiff’s action for damages for telephone service interruptions did not directly contravene any order or decision of the commission. Rather, the court reasoned that “It stands undisputed that the commission has approved a general policy of limiting the liability of telephone utilities for ordinary negligence to a specified credit allowance, and has relied upon the validity and effect of that policy in exercising its rate-making functions. [Citation.] It also appears clear that to entertain suits such as plaintiff’s action herein and authorize a substantial recovery from Pacific would thwart the foregoing policy. That being so, the express language of section 1759 [citation] bars plaintiff’s action.” (12 Cal.3d at p. 10, italics added.) The Waters rule may be further understood by considering examples of how it has been applied by our Courts of Appeal. When the bar raised against a private damages action has been a ruling of the commission on a single matter such as its approval of a tariff or a merger, the courts have tended to hold that the action would not “hinder” a “policy” of the commission within the meaning of Waters and hence may proceed. But when the relief sought would have interfered with a broad and continuing supervisory or regulatory program of the commission, the courts have found such a hindrance and barred the action under section 1759. Two pairs of Court of Appeal decisions are illustrative. First, in Cellular Plus, Inc. v. Superior Court (1993) 14 Cal.App.4th 1224 [18 Cal.Rptr.2d 308], a consumer of cellular telephone services filed an action seeking damages for price fixing in violation of the Cartwright Act (Bus. & Prof. Code, § 16700 et seq.) against two cellular telephone service companies. The commission had previously granted both defendant companies certificates of convenience and necessity authorizing them to operate in the geographic area in question, and had approved the rates they proposed to charge. The defendant companies demurred on the ground that the commission has sole jurisdiction over rates charged for cellular telephone service. The trial court sustained the demurrers without leave to amend, but the Court of Appeal granted a writ vacating the order. In the Court of Appeal the defendant companies conceded that the commission’s jurisdiction over rates does not immunize them from a Cartwright Act claim, but argued that such a claim must first be brought before the commission under the “primary jurisdiction” doctrine. (See Farmers Ins. Exchange v. Superior Court (1992) 2 Cal.4th 377 [6 Cal.Rptr.2d 487, 826 P.2d 730].) In rejecting that contention the Court of Appeal stressed that the commission had determined only that the proposed rates of the defendant companies were reasonable, while “Under the Cartwright Act a court does not look at the economic reasonableness of the prices. Rather, a court looks at whether the prices were in fact artificially maintained at a uniform level, whether ‘reasonable’ or not.” (Cellular Plus, Inc. v. Superior Court, supra, 14 Cal.App.4th at p. 1246.) The court then applied the rule of Waters, supra, 12 Cal.3d 1, 4, reasoning that “We cannot conceive how a price fixing claim under the Cartwright Act could ‘hinder or frustrate’ the PUC’s supervisory or regulatory policies. The only apparent policy of the PUC that could be affected is its regulation of rates charged by cellular telephone service providers. However, [plaintiff] does not dispute that the PUC has jurisdiction over rates, nor does it seek any relief requiring the PUC to change any rates it has approved.” (Cellular Plus, Inc. v. Superior Court, supra, 14 Cal.App.4th at p. 1246.) Again, in Stepak v. American Tel. & Tel. Co. (1986) 186 Cal.App.3d 633 [231 Cal.Rptr. 37], a telephone utility (PT&T) applied to the commission for approval of its proposed merger with another utility (see § 854). A minority shareholder of PT&T filed a class action against PT&T alleging breaches of fiduciary duty in connection with the merger. The commission thereafter approved the merger. Citing that approval, PT&T successfully moved to dismiss the shareholder action on the ground that section 1759 deprived the superior court of jurisdiction. The Court of Appeal reversed the judgment under Waters, reasoning that: “We are aware of no ‘declared supervisory and regulatory policies’ (Waters v. Pacific Telephone Co., supra, 12 Cal.3d 1, 4) ever formulated or relied on by the commission on the subject of safeguarding minority investor interests. Applying the Waters test of jurisdiction, we cannot conceive of how the superior court’s award of damages or other relief to wronged minority shareholders would ‘hinder or frustrate’ (ibid.) declared commission policy. Appellant’s class action suit is therefore authorized under section 2106.” (Stepak v. American Tel. & Tel. Co., supra, 186 Cal.App.3d 633, 640-641.) By contrast, in Brian T. v. Pacific Bell (1989) 210 Cal.App.3d 894 [258 Cal.Rptr. 707], the superior court action would have interfered with a broad and continuing policy of the commission, and hence was barred by section 1759. In the early to mid-1980’s telephone utilities began offering “information access services” from numbers bearing the 976 prefix (hereafter 976 services). Concerned by the use of 976 services to disseminate sexually explicit material to minors, Congress prohibited the dissemination of such material generally but provided for a defense if access were restricted to adults. The Federal Communications Commission (FCC) thereafter considered three methods of achieving such a restriction: (1) blocking devices on the customer’s premises, (2) blocking systems at the utility’s central station, and (3) “customer access codes” issued on request to adult subscribers. The FCC ultimately promulgated regulations adopting the third of these methods. In California the commission instituted an investigation into the same problem, acting both on its own motion and in response to a directive from the Legislature. The investigation resulted first in an interim decision adopted in January 1987, in which the commission expressed general approval of the central-station method of blocking sexually explicit messages, but ordered a delay in its implementation pending further study of the other two alternatives. The commission then conducted exhaustive hearings on the latter, and later in 1987 reaffirmed its decision in favor of central-station blocking. In June 1987 a minor listened to sexually explicit messages on a 976 service and then engaged in unlawful sexual contacts with another minor. The parents of both minors filed an action against the telephone company (Pacific Bell) and the businesses that furnished the messages, seeking damages and a preliminary injunction to compel Pacific Bell, inter alia, to make available to its customers screening or blocking devices that would deny minors access to sexually explicit material. The trial court denied the request for a preliminary injunction and granted Pacific Bell’s motion to dismiss the action for lack of jurisdiction. The Court of Appeal affirmed. Addressing the request for an injunction, the court quoted the Waters rule and held that the requested relief would call in effect for commission action modifying its previous decisions regulating the 976 services. Such interference with a commission policy was prohibited by section 1759. (Brian T. v. Pacific Bell, supra, 210 Cal.App.3d 894, 900-901.) The Court of Appeal further held that the trial court lacked jurisdiction to enjoin, in the alternative, violations of Penal Code section 313.1, subdivision (a) (dissemination of harmful matter to minors), reasoning that such relief would amount to a disguised means of compelling Pacific Bell to adopt a particular blocking system—i.e., customer access codes—that the commission had considered but thus far had rejected in developing its policy regulating access by minors to 976 services. (Brian T. v. Pacific Bell, supra, 210 Cal.App.3d at p. 901.) Finally, the Court of Appeal also held that Pacific Bell could not be liable in damages for failing to disconnect subscribers who used the 976 services to disseminate sexually explicit messages, because at the time of the acts alleged in the complaint that remedy had been prohibited by the January 1987 decision of the commission, which approved instead the remedy of blocking such messages on customer request. (Brian T. v. Pacific Bell, supra, 210 Cal.App.3d at pp. 908-909.) Again, in Schell v. Southern Cal. Edison Co. (1988) 204 Cal.App.3d 1039 [251 Cal.Rptr. 667], the superior court action would likewise have interfered with an ongoing commission inquiry into a matter of regulatory policy. Section 739 directs the commission, in exercising its ratemaking functions, to determine a “baseline quantity” of gas and electricity necessary to supply “a significant portion of the reasonable energy needs of the average residential customer” (id., subd. (a)), and to require utilities to establish “baseline rates” for supplying these baseline quantities to residential customers (id., subd. (c)(1)). Section 739.5 directs the commission to require that a “master meter” customer who furnishes gas or electricity through submeters to tenants of “a mobilehome park, apartment building, or similar residential complex” must charge each tenant the same residential rate—including the baseline rate—as would apply if the tenant were receiving the service directly from the utility. (Id., subd. (a).) Pursuant to these mandates, the commission designated baseline quantities of gas and electricity by an interim decision in 1976. In that decision the commission also determined that the term “residential customer” in section 739 included single-family houses, apartments, condominiums, and mobile-homes, but excluded transient trailerparks, hotels and motels, and other places of temporary occupancy such as hospitals and college dormitories. The commission took no position on recreational vehicle parks (hereafter RV parks). As required by the commission, gas and electric utilities undertook to establish rate schedules for master-metered facilities that incorporated the baseline rates structure. One such utility, Southern California Edison Company (Edison), adopted two residential rate schedules for such facilities: a general schedule for multifamily accommodations and a special schedule for mobilehome parks only. In September 1986 the owner of an RV park filed an action against Edison, alleging that his RV park was also a master-metered park with separate submeters for each tenant within the meaning of section 739.5, and hence was also entitled to residential baseline allocations under section 739. For this alleged discrimination the complaint sought damages under section 2106. By an amendment to the complaint the plaintiff added a cause of action for declaratory relief, asking for a ruling whether a person using a recreational vehicle as his residence was a residential customer under section 739 and therefore entitled to baseline allocations. Edison demurred on the grounds, inter alia, that the commission had exclusive jurisdiction and the issues were then pending in proceedings before the commission. The trial court sustained the demurrer without leave to amend, and the Court of Appeal affirmed the judgment of dismissal. The Court of Appeal took judicial notice of three proceedings pending before the commission. In two, owners of other RV parks had asked the commission to order Edison to supply electric service to them under the special rate schedule for mobilehome parks, while a mobilehome association sought an order that a new rate schedule be designed for RV parks only. The Court of Appeal stressed that the two proceedings were awaiting decision by the commission. The third commission proceeding was a recently decided, but not yet final, general rate case brought by Edison. In that decision the commission explicitly refused to apply the special rate schedule for mobilehome parks to RV parks. The commission also concluded that it did not have sufficient evidence to determine whether a new rate schedule should be designed for RV parks only, and therefore ordered Edison to conduct a study of the need for and feasibility of such a schedule, including the development of objective standards for judging and monitoring the status of RV park tenants. Although the plaintiff contended the superior court had jurisdiction under section 2106 because Edison’s refusal to give him the benefit of the mobile-home park rate supported a claim for damages, the Court of Appeal observed that the fundamental issue in the case was the appropriate rate schedule for RV parks. The court then reasoned that “The decision as to whether or not master-metered residential recreational vehicle parks should be charged at the same rate as master-metered mobilehome parks, or at another domestic or commercial rate, is clearly within the exclusive purview of the PUC as part of its continuing jurisdiction over rate making and rate regulation in provision of baseline service to residential customers of the electric and gas corporations.” (Schell v. Southern Cal. Edison Co., supra, 204 Cal.App.3d 1039, 1046.) The court concluded that because it was still an open question in the commission whether the special mobilehome rate schedule applied to RV parks, “for the superior court to undertake to determine this issue would be a usurpation of the PUC’s authority.” (Ibid., fn. omitted.) In addition, the Court of Appeal emphasized that the question of the proper rate schedule for RV parks was pending in the three commission proceedings discussed above. Relying on the rule of Waters, supra, 12 Cal.3d 1, the court held that so long as the matter was before the commission as part of its ongoing inquiry into RV park rate schedules, the superior court had no jurisdiction over the matter pursuant to section 2106. (Schell v. Southern Cal. Edison Co., supra, 204 Cal.App.3d at pp. 1046-1047.) We apply the rule of Waters and its progeny to the case at bar. Ill The first question is whether the commission has the authority to adopt a policy on (1) whether electric and magnetic fields arising from the powerlines of regulated utilities are a public health risk and (2) what action, if any, the utilities should take to minimize that risk. We conclude that it does. First, the commission has broad authority to determine whether the service or equipment of any public utility poses any danger to the health or safety of the public, and if so, to prescribe corrective measures and order them into effect. Every public utility is required to furnish and maintain such “service, instrumentalities, equipment, and facilities ... as are necessary to promote the safety, health, comfort, and convenience of its patrons, employees, and the public.” (§451, italics added.) The Legislature has vested the commission with both general and specific powers to ensure that public utilities comply with that mandate. As noted above, the Legislature has declared that the commission “may do all things” necessary and convenient to supervising and regulating public utilities in this state. (§ 701.) In particular, the commission has comprehensive jurisdiction over questions of public health and safety arising from utility operations. Thus the commission is generally authorized to require every public utility to “construct, maintain, and operate” its “plant, system, equipment, [or] apparatus” in such manner as to “safeguard the health and safety of its employees, . . . customers, and the public . . . .” (§ 768.) To this end, the commission is further empowered to prescribe the installation and use of “appropriate safety or other devices,” and to require every utility to do “any other act which the health or safety of its employees, . . . customers, or the public may demand.” (Ibid.., italics added.) More specifically, the Public Utilities Act provides in relevant part that whenever the commission finds that the “equipment, appliances, facilities, or service of any public utility, or the methods of manufacture, distribution, transmission, storage, or supply employed by it” are “unsafe,” it shall prescribe the equipment, appliances, facilities, or service to be provided or used by the utility, and shall further prescribe “rules for the performance of any service or the furnishing of any commodity” by such utility. (§761.) And whenever the commission finds that the equipment, apparatus, or facilities of any utility should be changed or improved, or new structures be erected, in order to promote the “security” of its employees or the public, it shall order the utility to make such changes or erect such structures. (§ 762.) Second, the commission has equally broad authority over the design and siting of electric powerlines. Its authority over design dates back to the early days of the commission and its predecessor, the California Railroad Commission (CRC). In 1911 the Legislature enacted a statute prescribing mandatory standards for the design and construction of overhead electric lines, poles, and wires. (Stats. 1911, ch. 499, § 1, p. 1037.) In 1915 the Legislature amended the statute by authorizing the CRC to permit certain deviations from those standards, and by adding a new section (§ 8) declaring that the CRC “is hereby instructed to inspect all work which is included in the provisions of this act, and to make such further additions or changes as said commission may deem necessary for the purpose of safety to employees and the general public, . . .” (Stats. 1915, ch. 600, § 4, p. 1063, italics added.) The legislation is now found in sections 8026 to 8038 of the Public Utilities Code. Pursuant to this grant of power, the CRC issued regulations governing overhead electric lines in 1922 (Gen. Order No. 64), in 1928 (Gen. Order No. 64-A), and in 1941 (Gen. Order No. 95). The latter order is still in effect, having been frequently amended since its date of issuance. Its stated purpose is to prescribe uniform requirements for overhead electric line construction in order to “insure adequate service and secure safety” to those who work on such lines and to “the public in general.” (Gen. Order No. 95, rule 11.) The order now comprises over 440 pages of highly detailed specifications for the design, construction, operation, and maintenance of overhead electric lines, including such matters as the number, spacing, material, strength, and shielding of conductor wires, and their minimum clearances from buildings, streets, and railroads. The order also regulates poles and towers, guy wires, insulators, transformers, voltage regulators, warning signs, and numerous other components of powerline design and construction. The commission also has exclusive jurisdiction over the siting of the vast majority of electric powerlines in this state. This jurisdiction flows from the general requirement that every public utility, including every electric utility, must obtain a certificate of public convenience and necessity from the commission before beginning construction of any “line, plant, or system, or of any extension thereof’ (§ 1001). The only exception to this requirement is the limited jurisdiction vested in the State Energy Resources Conservation and Development Commission (Energy Commission). With that exception, the commission retains exclusive jurisdiction over the siting of all other electric powerlines in the state, including all preexisting lines (Pub. Resources Code, §§ 25107, 25501), all lines in the interconnected transmission system (PUC v. Energy Com., supra, 150 Cal.App.3d 437), all primary or radial lines emanating from hydroelectric, wind, or solar photovoltaic powerplants (id. at p. 452; Pub. Resources Code, §§ 25107, 25120), and all lines emanating from out-of-state generating facilities (PUC v. Energy Com., supra, 150 Cal.App.3d at p. 452; Pub. Resources Code, § 25107). IV The next question is whether the commission has exercised the foregoing authority to adopt a policy on powerline electric and magnetic fields. We conclude that it has. Prior to 1988 the commission had addressed the issue of the potential public health effects of such fields only on a case-by-case basis. (See, e.g., San Diego Gas & Electric Co. (1981) Cal.P.U.C. Dec. No. 93785.) In 1988, however, the Legislature initiated a broad inquiry into the subject. It found, inter alia, that “A number of scientific studies are beginning to indicate that electromagnetic fields associated with electrical utility facilities may present a significant cancer risk.” (Stats. 1988, ch. 1551, § 1, subd. (a)(2), p. 5565.) The Legislature then declared its intent to determine by further research “whether exposure to electromagnetic fields caused by electrical utility generating and transmission facilities presents an unreasonable cancer risk, and whether legislation is needed to reduce that risk.” (Id., subd. (b), p. 5566.) To effectuate this intent the Legislature directed the commission and the State Department of Health Services (DHS) to prepare and submit a joint report (1) identifying any cancer or other medical risks found by any study to be associated with powerline electric and magnetic fields, and (2) listing further “high-priority research projects” that need to be undertaken to identify such risks. (Stats. 1988, ch. 1551, § 2, subd. (d)), p. 5566.) The legislation next directed the commission and DHS to jointly conduct the high-priority research projects thus listed, and to submit a further report within three years on the status of that research program and “on recommendations, if any, for legislation to limit exposure to electromagnetic fields.” (Stats. 1988, ch. 1551, § 3, subd. (b), p. 5567.) On September 15, 1989, the commission and DHS presented their first joint report to the Legislature in response to the foregoing statutory directive. (Rep. to Legis. by Cal.P.U.C. & Cal. Dept. Health Services, Potential Health Effects of Electric and Magnetic Fields from Electric Power Facilities (1989) (PUC & DHS Report).) The report summarized the existing studies on the topic and concluded, “the body of scientific evidence for electric and magnetic fields causing a significant health risk is not yet compelling, but it is worrisome.” (Id. at p. B-3.) The report then identified a number of high-priority projects for future research and recommended a series of additional steps, e.g., engineering studies of ways to reduce field exposure if necessary, consideration of a statewide program to measure fields, coordination with research and regulatory programs of other states, and educational outreach. The report next turned to the question whether statewide regulation of powerline electric and magnetic fields would be timely and appropriate. Seven states had adopted standards prescribing maximum allowable field levels in certain circumstances, but the commission and DHS rejected that step for California. Their report explained that “not enough is known yet to conclude whether or not these fields pose a significant health hazard. Setting field standards therefore might amount to addressi