Decrzemr 1992 81EPA Questions And Answers About

I.LACKGROUJND1.4.1.1.What are EMFs?There are many unanswered questions raised by theresearch done so far. There. have been both positiveand negative studies. We are not sure if EMFexposure adversely affects human health. Morecareful and extensive study of EMFs is needed.SEEMFs"is a shorthand term for "electric andmagnetic fields" or "electromagnetic fields."Electric and magnetic fields may occur alone or incombination and are a form of non-ionizingradiation. Examples of non-ionizing radiationinclude microwaves, visible light, and someultraviolet radiation. The American electric powersystem operates at 60 hertz (Hz). This means thatthe electric charges (current) flowing in the systemchanges direction 60 times a second. Althoughelectric and magnetic fields from 60 Hz exposuresare not considered "radiation" for various technicalreasons, they are still called "non-ionizingradiation".I.2.Since 1979, some studies of human populations,called epidemiology studies, suggest a potentialrelationship between exposure to EMPs and certaincancers. Unfortunately, there are manyuncertainties surrounding this information. Forexample, most of the epidemiological studies havevery limited information on what types of exposurewere experienced by the people in the studies. Theobserved increase in cancer was more pronouncedfor what are called "surrogates" or "indirect"estimates of EMF exposure than for electric andmagnetic fields measured using meters.' You mayhave heard about "wiring codes." Coding orcharacterizing houses according to the types ofnearby power lines has been one method to estimateEMF exposure in these studies. This is a"surrogate" of exposure.What are the sources of EMFs?Electric fields are produced by the presence ofelectrical charges, and magnetic fields areproduced by the movement of those charges.Electricity flowing in a wire or being used in an- pliance creates electric and magnetic fields. AllW wer lines and electrical appliances that drawcurrent have electric and magnetic fields aroundthem.1.3.What can EMFs do to me?The fact that disease incidence is correlated withsurrogate indexes for magnetic field exposure but'not with direct measurements, could be explained ineach of three ways or combination of these ways: a)the fields were different in the past, during the onsetof disease; than those measured later during thestudy; b) the wrong component or attribute of thefields was measured; and/or c) some other crucialfactor may be present which is unknowingly part ofwhat is being defined by the surrogate measure ofexposure. That factor could be some feature of theEMF exposure or something else altogether, such asa chemical exposure or differences in lifestyle.Are EMIFs like X-rays?No. X-rays, microwaves and other radio waves,and the electric and magnetic fields from powerlines and and electrically powered appliances areall part of the electromagnetic spectrum. ButX-rays are a form of electromagnetic radiationwith high levels of energy. This energy issufficient to dislodge electrons from atoms that thex-ray strikes; a process called ionization which canresult in cancer. EMFs, microwaves and othersimilar types of electric and magnetic fields do notionize atoms because of their lower energy levels.Some laboratory studies have shown that extremelylow frequency (ELF) electric and magnetic fieldscan affect various activities of cells. The laboratorystudies on biological effects also are uncertain. Forexample, many of the positive results have onlybeen found in one laboratory. Usually, before a22 December 1992

result is accepted as proof by scientists, it has beenseen by several different investigators.Because of the way appliances are made, they havethe potential to have very high localized fields, butthen the fields decrease rapidly with distance. Forexample, typical magnetic field strengths not nearan appliance are 0.1 to 4 milligauss (mG), but thefield from an electric can opener can be 20,000 mGat 3 centimeters (approximately 1 inch) from theappliance. At 30 centimeters (approximately 1foot), appliance fields are usually around 1000 timeslower. For the can opener mentioned above, thelevel would probably be around 20 milligauss.Additionally, it is not clear whether some of thebiological effects seen in laboratory studies of cellswould be harmful effects if they also occurred inpeople or whether they are minor changes that ourbodies-could adjust to.The bottom line is that there is no establishedcause and effect relationship between EMFexposure and cancer or other disease. For thisreason, we can't define a hazardous level of EMFexposure.When you stand under a power line, you are alreadyat least 20 feet or more away from the line,depending on its height above ground. Under atypical 230 kilovolt transmission line the magneticfield is probably less than 120 milligauss. Incontrast, if you move about 100 feet away from theline, the magnetic field is probably about 15milligauss, and if you are 300 feet away from theline, the magnetic field is probably less than 2milligauss.It is known that one type of magnetic field canhave beneficial health effects. One treatment usedby doctors to help heal broken bones that are nothealing-nornally, is to expose the area for a fewminutes a day to a specific type of magnetic field.This apparently affects the body's capability forhealing bone.I.5.How do I reduce my exposure?e electric fields can be easily shielded,fields are much more difficult to shield.ectric fields are shielded to some degree byalmost eveiything such as trees, bushes, walls, andso forth. Magnetic fields can be reduced byenclosing the source in certain types of metal suchas something called Mu metal which is a specialalloy. The fields are still present, but the metalhas the capability to contain them. This approachto reducing field levels is not practical for manysources, including power lines. (Some gadgetshave recently appeared on the market, such asbuttons,.peis, etc., claiming to shield one fromfields; it is almost certain that these do not work.)Magnetic field intensity can also be reduced byplacing wires close together so that the field fromone wire cancels the field from the other. This isnow-being done in new designs for electricblankets. To some degree the same thing can bedone for power lines, but for safety and reliabilityasons power lines have minimum requiredFrom these examples, we can see that distancefrom the source of the magnetic or electric field cansubstantially reduce exposure.1.6.What is a gauss?The gauss is a unit for the strength of a magneticfield, also known as magnetic flux density. Arelated unit used internationally for magnetic fluxdensity is the tesla. One tesla is equal to 10,000gauss. Magnetic flux density is measured in termsof lines of force per unit area. Remember thepatterns that were generated by iron filings on apiece of paper which was placed over a magnet?These patterns are field lines. .'We normally speakof magnetic fields in terms of thousandths of agauss or milligauss, abbreviated "mG."I.7.What Is a safe level?We don't know if EMF exposure is harmful (asidefrom the concern for electric shocks and burns forextreme exposure). We don't know if certain levelsof EMFs are safer or less safe than other levels.3December 1992

With most chemicals, we assume exposure athigher levels is worse than less exposure at lowerlevels. This may or may hot be true for EMFspalso. More research is required to identify doseresponse relationships. There is some evidencefrom laboratory studies that suggests that theremay be "windows" for effects. That means thatbiological effects are observed at some frequenciesand intensities but not at others. Also, we do notknow if continuous exposure to a given fieldintensity causes a biological effect, or if repeatedlyentering and exiting of the field causes effects.There is no number to which we can point and say'That is a safe or hazardous level of EMFexposure."I.8.magnetic field has usually dropped below 2 mG. Inthe case of an electric can opener, the magneticfield is probably below 2 mG approximately 3 feetaway.1.10. Why isn't the federal government setting astandard for EMF levels? Why have somestates set standards?Several states have established standards for electricand/or magnetic fields at the edge of the right ofway for power lines, usually transmission lines.These standards either have been on the books for awhile, and are based on older scientific information,or were set more recently to establish levels ofexposure that should not be exceeded. Thestandards were intended to keep field levels fromgoing any higher, because of the existinguncertainty about health risks.Is it true that levels below 2 milligauss(mG) are safe? Is there a standard?We do not yet know what if any magnetic fieldlevels are safe or unsafe. Th3 level of 2 mG is anarbitrary value used in some epidemiologicalstudies to place people in broad exposurecategories. Some other level could have been-used. But, because no dose/response relationshipyet been determined for EMFs, we cannotstablish a level which would be considered safeor unsafe.I.11.Yes, there are natural sources. The earth has amagnetic field that is approximately 500 milligauss.The earth's magnetic field is relatively constant,meaning that it does not change very much withtime, unlike power lines. There are electromagneticfields associated with thunderstorms. Lightning is asource of EMFs. Some animals like sense naturalelectric and magnetic fields. Our bodies alsoproduce electrical fields that make our nervoussystems and hearts work. These internal electricfields are fairly high.As a result, neither the EPA nor any other federalregulatory agency has established a standard forEMIs.I.9.Are there natural sources of EMFs? Arethey lEke the fields created by power lines?Can these cause health effects?What is a safe distance from a magneticfield source?Since we do not know if EMF exposure isharmful, we don't know what intensity of field issafe' or unsafe. In turn, we cannot say what is asafe distance. A related question is, "At whatdistance is the strength of the field indiscerniblefrom the background field levels?" It depends onthe source of the magnetic field and the what thebackground field level is. Background magneticfields usually range from 0.1 to 4.0 illigaussG). In the case of most high voltage powers, at 300 feet from the center span, theBatteries and some electrical systems also havefields that do not change with time; these are calledstatic or DC fields. DC stands for direct current.In contrasts, fields from most electrical powersystems and appliances vary in time and so arecalled time-varying fields or AC fields. AC standsfor alternating current. Electric power systems inthe United States operate at 60 Hz which cycles 60times per second.Se4December 1992

11.MEASUREMENTSenvironmental and computer magazines. Thesefirms will perform EMP measurements usually for 200 - 300. Alternatively, you can buy your ownmeter for 75 and up. These meters usually comewith instructions.YI.1.Do I need to get ENMF measurements?That's up to you. EPA neither recommends nordiscourages people from obtaining fieldmeasurements. You may decide to have EMFmeasurements made if you want to satisfy personalquestions, concerns, or curiosity about EMIFexposures.1I.2.How do I get my house or schoolmeasured?Depending on where you live, your local powercompany may offer to conduct field measurementsaround your home. Additionally, your stateHealth Department or State Department ofEnvironmental Protection may also be able toprovide you with field measurements or refer youto consulting firms that conduct electric andgnetic field measurements. Consulting firmsPy also be found through advertisements inDoes EPA recommend measurementcontractors?No. EPA does not recommend or endorse privatecompanies and contractors. EPA does not have aproficiency program - like the one for radon testingfirms - to measure the qualifications of contractorswho conduct electric and magnetic fieldmeasurements. Therefore, we cannot endorse orcomment on the qualifications of any contractor.The state of California is developing a list of firmsmaking ENM measurements. But the state is notrecommending or certifying these firms. To obtainthe list when it is completed, call (415) 540-2669 orwrite to the Special Epidemiology Studies Program,California Department of Health Services, 2151Berkeley Way, Room 704, Berkeley, CA 94704.What will EMF measurements tell me?Magnetic and electric field measurements will nottell you whether or not your exposure is harmfulor puts you at an increased risk, but they mayallow you to tell how your home compares to the"average" home. You should be aware that themeters typically used for home measurements canonly tell you "average field strength" in milligaussunits, at the time the measurements are performed.Even these measurements will vary over timebased on many factors, such as which appliancesare being used. EMF laboratory studies show thathkiological effects may depend on one or more ofany aspects of exposure. like frequency, intensity,oientation of the field, duration, transient orintermittent current,voltage spikes. Scientistsstill do not know what aspects of exposure, if any,are important. We therefore hove no. way ofestablishing either a safe or unsafe level. On thebasis of available scientific data, there is no wayof interpreting the health significance of EMFmeasurements.IL3.11.4.I1.5.Can I trust the measurements made by theutility?Yes. Utilities should have the expertise and properequipment to make accurate measurements. Thereis no reason to believe that the utility is trying tomislead you by providing you with false readings.Since we do not understand very much about thepossible health effects of EMFs or what levels, ifany, might be hazardous, there is no reason for theutility to give you false results. It is important toremember that readings will vary depending onfactors such as the time of day the measurementswere taken. The differences in readings usuallyreflect how much electricity is being used by thepower system and other things, like what appliancesare being used.II.6.My neighbors had EMFs around theirhouse measured. Is my house the same?Probably not. Measurements in the house are oftenaffected by many sources of magnetic fields5sDecember 1992

including electrical appliances or power systemcomponents (transmission or distribution lines,transformers, or house wiring). Fields are evenroduced by "ground currents" flowing in waterpipes. EMFs decreases quickly with distance fromthe source. A power line or other source close toyour neighbor's house may generate a measurablefield there but levels at your house may be verydifferent.magazines. Similar advertisements can also befound in scientific equipment journals, as well asnewsletters such as Microwave News, EMT Healthand Safety Digest and journals such as IEEESpectrumMicrowave News also maintains a directory ofcompanies which sell or rent magnetic field meters.We can send you a copy of that list, or you mayobtain a copy of this directory by sending a letterrequesting the "Gaussmeter Table" and a selfaddressed stamped envelope and 1.00 for shippingand handling to:Microwave NewsP.O. Box 1799Grand Central StationNew York, NY 10163EMPs can also be generated by many sources inaddition to power lines such as small appliances,hot water heaters, auxiliary power generators, andhousehold wiring. Since the presence of variouskinds of appliances varies from house to house, sodo EMF levels. Therefore, EMF levels in yourneighbor's house may be very different from thosein your own house.11.7.II.9.Can I make my own EMfmeasurements?EPA does not recommend any specific supplier,manufacturer, or type of measurement equipment.Yes, but be sure to learn how to makemeasurements properly. Before using anyinstruments, you should educate yourself on thee and degree of sensitivity, accuracy, and properwreration of the meter. This information can beprovided by the manufacturer. You could alsofollow recommendations from trade associationson how to measure fields. Table 1 includes somesources of measurement protocols.11.10. How much do meters cost?the simplest or best?Which one isPrices for meters range between 75 and 650.Companies may rent meters for between 60 and 100 per week. Electric and magnetic fields arethree dimensional. Each dimension is called an"axis" (the plural is "axes"). To properly measurea magnetic field all three axes of the field should bemeasured-- horizontal (front), horizontal (side) andvertical. "Single-axis" meters measure only oneaxis at a time and must be rotated until it is alignedwith the field. A three-axis meter can get anaccurate measurement no matter how it is orientedin the field, and they measure all three axes at thesame time. Single-axis meters are generally thecheapest; while three-axis meters which display anintegrated measurement (all three axes) are moreMost simple magnetic field meters only readaverage field intensity, given in milligauss (mG).Measurements can vary with time, space, andpower load on the electrical system. Some metersonly measure magnetic fields. Some metersmeasure both electric and magnetic fields.Remember

Electric and magnetic fields may occur alone or in combination and are a form of non-ionizing radiation. Examples of non-ionizing radiation include microwaves, visible light, and some ultraviolet radiation. The American electric power system operates at 60 hertz (Hz). This means that the