EXECUTIVE SUMMARY AND RECOMMENDATIONS
In 1973-74, Rochester Gas and Electric Company, Niagara Mohawk Power Corporation, and the Power Authority of the State of New York applied to build two 765-kV electric power transmission lines. Public concern about the first U.S. lines of such voltage concern fueled by many articles and a widely read book by Louise B. Young, Power Over People1 -caused the New York State Public Service Commission to convene hearings on the potential health and environmental effects of operating the lines. These hearings served, in effect, as a forum for experts and concerned scientists to discuss the potential effects of very high voltage lines. Testimony, which took place from October 1975 to June 1977, focused on the following general questions:
Although testimony explored these questions, issues remain and some controversies are unsolved. Because the testimony on the technical issues occupied 14,000 pages and because of controversies among expert witnesses, the Department of Energy (DOE) asked SRI International to review the testimony, clarify issues raised, resolve technical questions that remained unanswered, if possible, and to recommend research to resolve data deficiencies.
Many questions raised in the hearings can be answered by credible research programs. Other issues are primarily philosophical, although decision-making bodies such as courts. Congress, or the Environmental Protection Agency (EPA) must frequently take positions on them. The SRI International Project team has not tried to resolve these philosophical questions; rather, team efforts have been exerted in examining the testimony and key exhibits to set forth and clarify these issues.
The Expert Testimony
Audible Noise
Noise from a 765-kV transmission line sounds like humming or buzzing, and is loudest during periods of high corona discharge (that is, air ionization on the surface of the conductor wires). The electric field at the surface of the conductor ionizes the air where water condenses on the conductors. The ionization process produces the noise, and at night a corona glows on the conductor surface. The experts agreed that the noise would not cause physiological damage nor cause any direct physiological effects.
The noise might disturb some people within 250 m (750 ft) on either side of the right-of-way.
How much noise do the lines produce outdoors?
Noise from the lines is highest during rain, snow, and fog.
Energy equivalent noise levels over the year are about 53 dB (the levels would be higher during foul weather, but lower during fair weather) at the edge of the right-of-way (that is, 38 m, or 125 ft, from the center of the transmission line), while on peak noise days the energy equivalent day/night weighted level is 58 dB.2 Transmission line noise near the right-of-way will typically be greater than noise created by the storm activity of rain and wind alone and will be more apparent during fog and snow than during rain. Transmission line noise levels decrease quickly as distance from the line increases, and will disappear into background noise levels at distances of 250 to 300 m (750 to 1000 ft) from the center of the right-of-way3. Even in fair weather, 765-kV lines would produce some noise.
How will these noise levels disturb people?
Outdoors-they will occasionally interfere with understanding speech.
People standing outdoors at the edge of the right-of-way will have some difficulty understanding one another if they are standing more than 2.4 m (8 ft) apart when the transmission line noise is the loudest (that is, in periods of heavy rain or snow). During fair weather, no interference will occur.
Indoors-line noise will sometimes disturb sleep.
Relying on data presented in the hearings, the SRI International project team suggests that residences within 150 m (500 ft) of the center of the right-of-way could have unacceptable indoor noise levels (those steady nighttime noise levels above 35 dB). At 150 m the energy equivalent noise level from the transmission line would be about 35.5 dB. However, it would be necessary for bedroom windows to be open for line noise to interfere with sleep beyond the right-of-way, and only some people would have their sleep disturbed.
If lines pass close to communities, noise complaints may follow.
Based on the testimony, the SRI International team suggests that the noise levels at the edge of the right-of-way appear to be high enough that they may result in some complaints to authorities or threats of legal action. Higher income communities and rural communities appear more likely to voice their complaints than lower income and urban communities.
What is the major controversy in the noise testimony?
Whether the transmission line noise meets suggested EPA guidelines.
High levels of audible noise occur only during foul weather. Such weather is limited to rain, which occurs 3-10% of the time along the right-of-way in New York; fog about 40 of the time; and snow about 5-10% of the time. EPA4 has suggested 55 dB Ldn5 as an upper limit for an acceptable noise environment. Using these guidelines as a starting point, the experts argued about whether to average the noise over 24 hours or over I year. The noise from a 765-kV transmission line is 58 dB Ldn averaged over 24 hours (the maximum 24-hour average), whereas the noise is 53 dB Ldn averaged over 1 year. Unfortunately, the EPA document only suggests averaging times for Ldn measurements, and witnesses debated the EPA's intent in setting the 55 dB Ldn limit.
More recent studies by EPA and others suggest that 765-kV transmission line noise could cause at least sporadic complaints and possible widespread complaints in certain types of communities, if the lines pass close to the community and it has had little exposure to high noise levels.
What questions are left?
How do we best use the noise data?
The question remains of how best to use transmission line noise measurements to predict whether communities will be disturbed by 765-kV transmission line noise. In addition, better data are needed on how houses, particularly house walls with windows, attenuate transmission line noise. The hearings did not consider whether transmission line noise has characteristics (buzzing or crackling) that are particularly annoying.
Effects of Electromagnetic Fields on Biological Systems
The fields are not strong enough to cause excessive tissue heating, the primary hazard from electromagnetic fields. Nevertheless, the main controversy in this area of the hearings is whether or not biological effects are possible from transmission line fields other than unimportant heating. About two-thirds of all the testimony centers on this hotly contested topic. The witnesses concentrated on potential effects from the electric field.
How strong are the fields?
The electric field is about 10 kilovolts per meter (kV/m) at ground level, and the magnetic field is about 0.6 gauss (G).
These are peak fields directly under a 765-kV line. A field of 2500 kV/m will ionize air to cause corona discharge. These fields decrease rapidly as distance from the lines increases, and drop to about 2.5 kV/m at the edge of the right-of-way 38 m (125 ft) from the lines' center. The peak ac magnetic fields at ground level are about 0.6 G with 4000 amperes (A) per conductor and about 0.15 G with 1000 A per conductor. The earth's magnetic field, which is constant, is about 0.5 G. The magnetic fields also decrease rapidly as distance from the lines increases.
Can the disagreement over whether there are biological effects be settled at this time?
Not satisfactorily.
The experiments claimed to support the existence of effects are challenged, with poor experimental design and inadequate statistical treatment of results cited. Effects may nonetheless exist; however, if they do, they are subtle, they are difficult to detect, and they require careful experimentation.
Have electric fields under transmission lines been shown to be hazardous?
No; on the other hand, neither have the fields been shown to be without effect.
It is impossible to demonstrate absolutely that any environmental agent is without effect because an infinite number of experiments on all biological systems would be required. (Only one positive experiment, on the other hand, is required to prove a hazard.) Most of the studies referred to by witnesses in the hearings are not useful for hazard determination, primarily because the effects are as yet poorly understood. For example, although no dose-response relationships between field levels and exposure times have been demonstrated experimentally, such data are necessary for determining whether the fields are hazardous.
Little evidence offered in the hearings indicates that people are adversely affected either at home or at work by electric fields at power line frequencies. This absence of evidence cannot be construed to mean that no effects occur. However, it does imply that if effects take place, they are more subtle than commonly encountered occupational diseases or than diseases resulting from common environmental agents such as urban smog.
What are the difficulties encountered in resolving the question about health and environmental hazards?
It is difficult and expensive to undertake credible experiments.
The experts disagree about whether low-frequency electromagnetic fields cause biological effects at levels under transmission lines. Nor do such disagreements lend themselves to ready settlement; difficult and time consuming effort would be required to perform better experiments than those available to the witnesses. However, those experimental results that seem to have indicated a "stress response" to exposure to low-frequency electromagnetic fields may, in the absence of careful experiments, indicates that biologic systems respond to the fields. The testimony revealed no systematic studies of the threshold of intensity or the duration of exposure required to produce alleged effects. Such systematic studies must be performed before it can be determined whether or not the fields under 765-kV transmission lines present hazards.
The majority of the research discussed in the hearings, because it purports to show effects, creates an impression in the lay reader that effects are there for even the simplest scientific experiment to display. Such is not the case.
Will these field levels affect biological systems?
The experts disagree vehemently.
The witnesses described and examined many claimed effects, including:
Many of the experiments described by witnesses involved electric and/or magnetic fields with strengths much greater or frequencies substantially different than ground level fields under 765-kV lines. Some experts claimed that no effects exist (apart from unimportant heating); others recommended that the likelihood of hazards was sufficient to justify the New York Public Service Commission halting construction of the proposed lines.
Sparks and Currents Received When a Person Touches a Vehicle Parked Under the Lines
Just before a person touches a vehicle parked under a 765-kV transmission line a series of small sparks will be felt, similar to those felt when walking across a carpet on a dry day. When someone firmly contacts a vehicle, a continuous 60-Hz current will flow through the body.
What are the magnitudes of the sparks and currents?
The magnitudes vary considerably.
The maximum theoretically possible (worst case) current is about 7.5 milliamperes) (mA) when a well-grounded person touches a tractor-trailer truck parked under a line with a 12.8 m (42 ft) minimum clearance above the ground. Higher line clearances reduce the current. In addition, smaller vehicles generally result in smaller currents. For the proposed New York lines, which are to have a minimum ground clearance of 15 m (48 ft), the maximum theoretically possible current is about 5 mA when touching a tractor-trailer or a large bus.
Measured currents for actual vehicles are frequently 1 2o or less of the maximum theoretically possible. However, one witness did measure a value in one experiment that was 90% of the theoretical value. Hence, actual currents of 4-5 mA might result if a large vehicle were touched under unusual circumstances (e.g., the vehicle were well-insulated from the earth and the person were in good electrical contact with the earth).
Witnesses disagreed about the theoretical description of the sparks felt when a person touched a vehicle parked under the lines. The energy present in each spark appeared to be the most appropriate indicator of effects. Vehicle voltage can reach well over 1000 V with respect to the ground. A person within a few millimeters of the vehicle discharges the built-up voltage and sparks begin. Spark energies as high as 65 millijoules (mJ) are theoretically possible from touching a tractor-trailer truck parked under a line with a 12 m (42 ft) clearance. However, witnesses argued over what energies would occur in an actual situation. Measured values ranged from less than 0.1 mJ for sedans to more than I mJ for trailer trucks.
What are the effects?
Adults will be startled, but children may be more seriously affected.
Witnesses agreed that adults will occasionally be startled by the currents and sparks they feel when they touch a large vehicle parked under the lines or even at the edge of the right-of-way. The witnesses also agreed that the only danger from the sparks and currents are secondary ones with a person possibly recoiling into moving machinery or falling. However, no statistical description of these possibilities was presented in the hearings, and no cases of such secondary injury to adults were cited in connection with transmission lines.
As levels of current increase, people experience a series of reactions: first, a tingling sensation at the point of contact with currents of 0.5-2.0 mA; then a startle reaction with currents of 1.5 mA and greater (people find currents of 2.0 mA to be objectionable); finally, as the current becomes great enough (the release current) a person is unable to release the current source because of tetany in the arm muscles. The average release current for adult males is 16 mA and for adult females is 10.5 mA, but it may be as low as 5 mA for small children. Greater currents result in respiratory paralysis and finally in ventricular fibrillation. Respiratory paralysis begins at 18-22 mA for adults, and could be as low as 7-8 mA for children.
The physical reaction to electric currents depends on body size, with small children more affected by smaller currents than adults. For the obvious reasons of safety, little research has been done on the reaction of children to electrical currents. The release current for children is thus not known, but the witnesses theorized, based on extrapolation of data on adults, that it may be about 5 mA for small children. It is not known how much amperage above the release current causes respiratory arrest in children. In two recorded cases, children who came in contact with an 8-mA current (which had nothing to do with a transmission line) died. It appears that the S-mA current possible under transmission lines under worst-case conditions is close to the suspected release current for small children.
What is the important unresolved question?
The release current for children.
Clearly, the major gap is uncertainty about what constitutes release currents and currents that induce respiratory arrest in children. Nor is it accurately known how much the current that causes respiratory arrest exceeds the release current. If the two currents differ by only a few milliamperes it becomes possible that currents under 765-kV lines might, indeed, under rare circumstances approach the respiratory arrest current for children.
Effects of Electromagnetic Fields on Cardiac Pacemakers
The fields under 765-kV transmission lines may affect some cardiac pacemakers, although the testimony cited no cases of transmission line interference. In fact, data are limited about pacemaker interference from 6Hz electromagnetic fields and therefore only tentative conclusions are possible.
How do pacemakers respond to electromagnetic interference from transmission lines?
Three responses are possible:
Transmission line fields are too small to cause pacemaker dysfunction-operation at an extreme rate, either fast or slow, or failure to send a pacing signal to the heart for a significant time.
Are any of the three ways the pacemaker may react physically important?
Only intermittent changes in rhythm or rate and reversion to a fixed rate
of pacing are.
Some pacemakers are sensitive to 6Hz interference at voltages of about 0.27 to 3.0 mV on the pacemaker lead to the heart. Sensitivity appears critically dependent on the type of lead, the type and brand of pacemaker, and the position and orientation of the person in relation to the transmission line.
The most sensitive pacemakers might revert to a fixed rate of pacing even beyond the right-of-way-as far as 50 m (150 ft) from the center, under conditions of maximum coupling and a sensitive pacemaker with a unipolar catheter.
Are there any medical implications of the pacemaker's reaction to 765-kV transmission line fields?
None, except for certain individuals.
The exception appears to be for those patients who have coronary artery disease or a serious electrolyte ;imbalance, who experience drug toxicity, or who are subject to ventricular fibrillation. It was claimed in the hearings (although the testimony was stricken because the witness was not a cardiac specialist) that ample evidence indicates that if a pacemaker stimulus occurs during a brief period of hyperexcitability in the heart's electrical cycle, serious disturbances of the heart rhythm may be induced, including rapid heartbeat (ventricular tachycardia), or possibly ventricular fibrillation, which requires immediate medical attention.
The testimony suggests that pacemaker wearers who are likely to be harmed by competition with the pacemaker signal would be unlikely, because of their general health, to be moving about in the vicinity of the lines.
What impedes resolving the major uncertainties remaining about hazards to pacemaker wearers?
Data are lacking.
No definitive answer as to how 765-kV power lines might endanger pacemaker wearers emerged from the testimony. Only a very few pacemakers were tested against 60-Hz voltages, with no indication about how this small sample relates to the population of pacemakers. Nor was it clear whether a pacemaker that entered into competition with an intrinsic heartbeat would endanger the wearer.
Plant Damage from Ozone Produced During Periods of High Corona Discharge
Transmission lines produce relatively little ozone, and possible effects are limited to the vicinity of the right-of-way. Atmospheric diffusion and mixing rapidly reduce the concentrations as the distance from the line increases.
How much ozone is produce?
Very little, compared with other contributing sources such as sunlight or automobiles in urban areas.
The maximum rate of ozone production occurs less than about 0.3% of the time during fog or heavy rain and the minimum rate occurs during fair weather.
How much do ozone concentrations along the right-of-way increase as a result?
The most when it is raining and a calm wind is blowing parallel to the line, and much less during fair weather or more wind.
During fair weather, the maximum concentration increase would be only about 0.25 ppb. Background concentrations vary from 8 ppb to more than 150 ppb. During rain, snow, or hail, the maximum concentration increase would be 7-9 ppb, but background concentrations would peak below about 100 ppb.
Will these increases damage plants along the right-of-way?
No.
No damage to plants from ozone production by transmission lines has been found because the increases are highly variable and small compared with the ozone background. The maximum increases of the 7-9 ppb produced by the lines occur very infrequently and then only during heavy rains accompanied by very slow wind that blows exactly parallel to a long stretch of transmission line [more than 1.5 km (I mile)l. Even under these conditions, roughly 10-hours are required for the concentration to build up to the 7-9 ppb level.
Will increase in ozone concentration from line operation violate air quality standards?
It is unlikely.
The National Ambient Air Quality Standard for ozone is 120 ppb, not to be exceeded as a peak l-hour concentration on more than 1 day per year. The air quality along the proposed New York State right-of-way frequently violates this standard during fair weather when the ozone background is highest. Moisture in the air during foul weather reduces the ozone background so that even the peak addition from the transmission lines would not cause violations of the air quality standard. The atmospheric conditions of a stable wind blowing parallel to a long stretch of line for several hours during heavy rain would be infrequent enough that further violations of the air quality standards, already occurring from other sources, would be unlikely.
What data gaps and unresolved questions about ozone remain?
No new measurements are needed.
Measurements were completed to confirm the primarily theoretical results presented in the hearings. Measurements are difficult owing to the relatively small concentration increases produced by the lines and to the variations in ozone production during weather and in the ozone background.
Recommendations
The SRI International project team recommends the following research:
As can be seen, these recommendations relate to effects caused potentially either by corona discharge (with noise and ozone resulting) or by the electromagnetic fields at ground level (effects on biological systems, on people touching vehicles parked under the lines, and on cardiac pacemakers). The extensive research programs now under way will improve the understanding of corona phenomena and their conclusions should aid in lessening corona, thereby reducing both noise effects and potential ozone effects.
Research that improves the understanding of right-of-way design and that provides technical options for reducing ground level electromagnetic fields will become important if regulatory standards for permitted ground level fields are issued. Options for reducing the ground level fields include:
Trade-offs between costs and environmental benefits will result from implementing any of these options, including increased system cost, increased visual and aesthetic impacts (if tower height were increased) and increased right-of-way width. These trade-offs need systematic exploration.
Issues Not Examined in the New York Hearings
The hearings address several important issues. However, important issues are left unexplored, including:
These issues must also be considered as part of a comprehensive
evaluation of 765-kV and higher voltage transmission lines.
1 L.B Young, Power OVER People, Oxford University Press (New York, 1973).
2 A-weighted levels are indicated throughout. Chapter I defines noise terms.
3 The utilities requested a right-a-way for the 765-kV transmission lines of 76 m (250 ft) in width. As Appendix A indicates, the New York Public Service Commission provisionally ordered the utilities to acquire a 107 m (350 ft) right-of-way that excludes all residences. The term "right-of-way" throughout this report refers to the 76 m (250 ft) right-of-way described in the testimony.
4 Environmental Protection Agency, "Levels of Environmental Noise Requisite to Protect Public Health and Welfare with an Adequate Margin of Safety," EPA 550/9-74-004 (1974).
5 Ldn is an average of noise levels over a 24-hour period (or longer) that weighs nighttime noise more heavily than daytime noise. Chapter I describes noise averaging.
6 This recommendation is also discussed in R.S. Banks, et al., "Public Health and Safety Effects of High-Voltage Overhead Transmission Lines: An Analysis for the Minnesota Environmental Quality Board," Minnesota Department of Public Health (October 1977).
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