Bioelectromagnetics 13:395-400 (1992)
Effects of a 30 kV/m, 60 Hz Electric Field on the Social Behavior of Baboons: A Crossover Experiment Stephen Phillip Easley, Anthony M. Coelho, Jr., and Walter R. Rogers Behavioral Medicine Laboratory, Southwest Foundation for Biomedical Research, San Antonio (S. P.E., A. M.C.) and Department of Biosciences and Bioengineering, Southwest Research Institute, San Antonio, Texas (W. R.R.) Using a crossover experimental design, we evaluated our earlier findings that exposure to a 30 kV/m, 60 Hz electric field for 12 hours per day, 7 days per week for 6 weeks produced significant changes in the performance rates of social behaviors among young adult male baboons. In the crossover experiment, the former control group was exposed to a 30 kV/ m, 60 Hz electric field for 3 weeks. Only an extremely small, incidental magnetic field was generated by the exposure apparatus. We found that electric-field exposure again produced increases in the performance rates that index Passive Affinity, Tension, and Stereotypy. These findings, combined with results from our other electric-field experiments, indicate that exposure to strong electric fields, in the absence of associated magnetic fields, consistently produces effects that are expressed as increases in rates of performance of social behaviors in young adult male baboons. 0 1992 Wiley-Liss, Inc.
Key words: EMF, electric field bioeffects, baboon social behavior
INTRODUCTION
Data collected in the last two decades have related exposure to 60 Hz electric and magnetic fields (EMF) to numerous biological effects [Coelho et al., 1991; Easley et al., 19911. For example, there is growing concern that EMF bioeffects may involve brain and behavior. As a means of assessing the basis for this concern, we began a series of experiments using the quantitative measurement of the social behavior of baboons as a dependent variable for the assessment of the effects of electric field exposure [Coelho et al., 1991; Easley et al., 19911.
Received for review October 8, 1991; revision received April 3, 1992. Address reprint requests to Dr. Stephen P. Easley, Ph.D., Behavioral Biology Division, New Mexico Regional Primate Research Laboratory, Holloman AFB, NM 883 10. 0 1992 Wiley-Liss, Inc.
396
Easley et al.
We reported [Coelho et al., 19911 on an experiment in which one group of eight male baboons was exposed to a 30 kV/m electric field for 12 hours per day, 7 days per week for 6 weeks, while a second group of eight male baboons was maintained in a sham-exposed, control condition. Performance rates of six categories of social behavior and four categories of non-social behavior were used as criteria for comparing exposed and unexposed subjects and for comparing each group over three 6 week experimental time periods (Pre-Exposure, Exposure, and Post-Exposure). This 30 kV/m experiment was the first demonstration that electric field exposure could significantly alter nonhuman primate social behavior, specifically the mean performance rates of Passive Affinity, Tension, and Stereotypy behavior in adult male baboons who served as animal model surrogates of human exposure. The exposed group showed dramatic and significant increases in performance rates of the affected behavior categories during the exposure period, while the control group did not exhibit significant increases in performance rates. Immediately following the Post-Exposure period, at the conclusion of the 30 kV/m experiment, we further validated our findings by means of a crossover experiment. In the crossover experiment the former control group was exposed to a 30 kV/m, 60 Hz electric field for 3 weeks, and the former exposed group became the new control group. This design permitted us to compare behavioral performance both within and between groups. Our intent was to determine whether the electricfield exposure effects observed in the main 30 kV/m experiment would be seen in a second group of previously unexposed animals. MATERIALS AND METHODS
The two-sided, mirror image design of the experimental facility, which housed an independently functioning transformer and exposure apparatus on each side, permitted us to perform a crossover experiment. During the crossover experiment, the control (East) group from the main 30 kV/m experiment became the exposed group in the crossover, while the exposed (West) group from the main 30 kV/m experiment became the control group in the crossover. This was possible because the the social behavior of the previously exposed subjects (West group) had returned to normal baseline levels during the Post-Exposure period of the main experiment. In the crossover experiment, we exposed the East group of eight male baboons to a 60 Hz electric field (E-field) of 30 kV/m intensity (12 hours per day, 7 days per week) for 3 weeks, while the West group of eight animals was maintained in a shamexposure (control) condition. Only extremely low, incidental levels of magnetic field were generated by the apparatus used in this experiment [Coelho et al., 19911. Other than the reversal of control and exposed groups, and the duration of the exposure ( 3 weeks vs. 6 weeks), all procedures were identical for both experiments. As a basis for comparison, we used the Post-Exposure period of the main 30 kV/m experiment as the no-exposure Baseline for the crossover experiment. Facility Design
Descriptions of the exposure facility, its operating characteristics, and electric field quality control have been presented elsewhere [Cory et al., 1987; Coelho et al., 19911.Quality control of electric field characteristics and facility operations at Southwest Research Institute (SwRI) was monitored by a joint committee consisting of staff from
Electric Field Exposure and Social Behavior
397
the United States Department of Energy (DOE), the National Bureau of Standards, the Central Research Institute of the Electric Power Industry (CRIEPI) of Japan, and an independent consultant, W/L Associates, under contract to DOE. Experimental Subjects
There were 16 male baboons (Papio cynocephalus anubis) used in this experiment. All subjects were members of a single birth cohort and were 5 to 6 years of age (young adults) at the time they were assigned to the experiment [Coelho et al., 19911.Water and commercial primate diet were available to the animals ad libitum. Data Analysis
We measured the performance rates of the three categories of behavior (Passive Affinity, Tension, and Stereotypy) that were significantly affected by electricfield exposure in the main 30 kV/m experiment, using methods described previously by Coelho et al. [ 19911. We tested between-group differences in group performance rate means for each period of each of the three behavioral categories by two-sample t tests. Within-group comparisons between baseline and exposure periods were made by paired-comparison t tests. As in the main 30 kV/m experiment, the significance level was set at P < 0.05 (two-tailed). RESULTS
Results of the crossover experiment are presented in Figure 1. We have also included the results of the main 30 kV/m experiment for comparative purposes. The performance rates of the control (West) group exhibited little change from the Baseline to the Crossover exposure period, and none of the within-group changes in the control (West) group were statistically significant (Table 1, Fig. 1) from Baseline to the Crossover exposure period. During the Crossover exposure period, the exposed (East) group exhibited increased performance rates of all three criterion behaviors. Passive Affinity showed statistically significant between-group differences during Crossover exposure. Comparing within-group Baseline values to Crossover exposure values, the exposed (East) group exhibited a highly significant, 208% increase in the performance rate of Passive Affinity behaviors during electric field exposure (Table 1, Fig. 1). Tension increased by 40% and Stereotypy increased by 75% from Baseline to the Crossover exposure period. Although these increases were large, Tension and Stereotypy did not attain statistically significant between-group differences during Crossover exposure, nor did they exhibit statistically significant within-group changes over time as they had done in the main experiment (Table 1, Fig. 1). DISCUSSION
We previously reported that 6 weeks of exposure to both 30 kV/m and 60 kV/ m electric fields produced significant changes in the social behavior of young adult male baboons [Coelho et al., 1991; Easley et al., 19911. The crossover experiment described in this paper confirmed that 3 weeks of exposure to a 30 kV/m, 60 Hz electric field also produces i.ncreases in the rate of performance of the three criterion behaviors.
398
Easley et al.
24
1
Passive Afflnlty
6-
Tenaion
EeUGrap
4-
West Group
-E-fioldEapown
5.
m
.\
4-
:::::: ::.: :.:,:. .:.:
\
3.
2.
T
P < 0.05
1 1.
28
-
24
-
Stereotypy I
20-
16-
12-
8.
0
Pro-ErpOOUro
EXpOlUn
Maln 30 kVlm Expwlmont
POI1-Enpoaum
cmuovr
-
Buellno
f
EnpOSW.
f
CroBsover 30 kVlm Exporlnwnl
Fig. 1
Electric Field Exposure and Social Behavior
399
TABLE 1. Paired-Comparison t Test Values (t) and Significance Values (P)from Comparison of Mean Performance Rates During the Baseline Period With Mean Performance Rates During the Crossover Exposure Period, for each Group Separately* ~~~
East group Passive affinity Tension Stereotypy
t -1 1.84 -1.13 -2.1 1
West group P
t
0.00
- 1.69
0.30 0.07
0.98 0.91
P 0.13 0.36 0.30
*Only the East group was exposed.
Passive Affinity demonstrated statistically significant between-group and withingroup changes in response to electric field exposure. The measured within-group increase was greater than the within-group increase measured for this behavior category in the main 30 kV/m experiment [Coelho et al., 19911. When the previously unexposed East group was exposed to the 30 kV/m electric field during the Crossover, the baboons exhibited substantial increases in performance rates of Tension and Stereotypy behaviors, although the differences did not attain statistical significance, as they had in our other experiments. The difference between our previous studies [Coelho et al., 1991; Easley et al., 19911 and the current study in the length of E-field exposure may be reflected in the measured rates of Tension and Stereotypy behaviors during Crossover, i.e., longer exposures may have produced significant effects in these two behavior categories. We have suggested that these behavioral responses to E-field exposure could be the result of perception of the field and/or a direct effect on the central nervous system [Coelho et al., 1991; Easley et al., 19911.At present there are no data available to address or resolve that issue. Nevertheless, the clear alteration of social behavior patterns demonstrated in our three experiments suggests that exposure to E-fields affects central nervous system function by some as yet unknown mechanism. At present there are insufficient data to assess whether or not such disruptions are deleterious bioeffects resulting from exposure to strong, 60 Hz electric fields. ACKNOWLEDGMENTS
This research was sponsored jointly by the Office of Energy Management of the United States DOE and CRIEPI of Japan, and was conducted as contract DEACOI-80-RA50219. We would like to thank Dr. G.T. Moore, Dr. J.L. Orr, Dr. W.R. Rogers, Dr. L.L. Taylor, Mr. J.H. Lucas, and Mr. H.D. Smith for their assistance. We also acknowledge the comments and suggestions on the manuscript provided by members of the staff of CRIEPI. SwRI and SFBR are accredited by the American Association for Accreditation of Laboratory Animal Care and are in compliance with the requirements of the Animal Welfare Act.
Fig. 1. Means and standard errors for A) Passive Affinity, B) Tension, and C) Stereotypy behaviors, by experimental periods. The West group was exposed to the E-field during the first exposure period and the East group was exposed to the E-field during the second exposure period, as indicated by shaded boxes. Statistically significant between-group differences are indicated by P < 0.05.
400
Easley et al.
REFERENCES Coelho AM Jr, Easley SP, Rogers WR (1991): Effects of exposure to 30-kV/m, 60-Hz electric fields on the social behavior of baboons. Bioelectromagnetics 12: 117-135. Cory WE, Barsun HF, Lucas JH, Polonis JJ, Rogers WR (1987): High intensity 60-Hz electric exposure facility for nonhuman primates. In Anderson LE, Kelman BJ and Weigel RJ (eds): “Interaction of Biological Systems With Static and ELF Electric and Magnetic Fields. Proceedings of the 23rd Hanford Life Sciences Symposium.” Richland, WA: Pacific Northwest Laboratory, pp 101-1 10. Easley SP, Coelho AM Jr, Rogers WR (1991): Effects of exposure to 60-kV/m, 60-Hz electric fields on the social behavior of baboons. Bioelectrornagnetics 12:361-375.
Effects of a 30 kV/m, 60 Hz Electric Field on the Social Behavior of Baboons: A Crossover Experiment Stephen Phillip Easley, Anthony M. Coelho, Jr., and Walter R. Rogers Behavioral Medicine Laboratory, Southwest Foundation for Biomedical Research, San Antonio (S. P.E., A. M.C.) and Department of Biosciences and Bioengineering, Southwest Research Institute, San Antonio, Texas (W. R.R.) Using a crossover experimental design, we evaluated our earlier findings that exposure to a 30 kV/m, 60 Hz electric field for 12 hours per day, 7 days per week for 6 weeks produced significant changes in the performance rates of social behaviors among young adult male baboons. In the crossover experiment, the former control group was exposed to a 30 kV/ m, 60 Hz electric field for 3 weeks. Only an extremely small, incidental magnetic field was generated by the exposure apparatus. We found that electric-field exposure again produced increases in the performance rates that index Passive Affinity, Tension, and Stereotypy. These findings, combined with results from our other electric-field experiments, indicate that exposure to strong electric fields, in the absence of associated magnetic fields, consistently produces effects that are expressed as increases in rates of performance of social behaviors in young adult male baboons. 0 1992 Wiley-Liss, Inc.
Key words: EMF, electric field bioeffects, baboon social behavior
INTRODUCTION
Data collected in the last two decades have related exposure to 60 Hz electric and magnetic fields (EMF) to numerous biological effects [Coelho et al., 1991; Easley et al., 19911. For example, there is growing concern that EMF bioeffects may involve brain and behavior. As a means of assessing the basis for this concern, we began a series of experiments using the quantitative measurement of the social behavior of baboons as a dependent variable for the assessment of the effects of electric field exposure [Coelho et al., 1991; Easley et al., 19911.
Received for review October 8, 1991; revision received April 3, 1992. Address reprint requests to Dr. Stephen P. Easley, Ph.D., Behavioral Biology Division, New Mexico Regional Primate Research Laboratory, Holloman AFB, NM 883 10. 0 1992 Wiley-Liss, Inc.
396
Easley et al.
We reported [Coelho et al., 19911 on an experiment in which one group of eight male baboons was exposed to a 30 kV/m electric field for 12 hours per day, 7 days per week for 6 weeks, while a second group of eight male baboons was maintained in a sham-exposed, control condition. Performance rates of six categories of social behavior and four categories of non-social behavior were used as criteria for comparing exposed and unexposed subjects and for comparing each group over three 6 week experimental time periods (Pre-Exposure, Exposure, and Post-Exposure). This 30 kV/m experiment was the first demonstration that electric field exposure could significantly alter nonhuman primate social behavior, specifically the mean performance rates of Passive Affinity, Tension, and Stereotypy behavior in adult male baboons who served as animal model surrogates of human exposure. The exposed group showed dramatic and significant increases in performance rates of the affected behavior categories during the exposure period, while the control group did not exhibit significant increases in performance rates. Immediately following the Post-Exposure period, at the conclusion of the 30 kV/m experiment, we further validated our findings by means of a crossover experiment. In the crossover experiment the former control group was exposed to a 30 kV/m, 60 Hz electric field for 3 weeks, and the former exposed group became the new control group. This design permitted us to compare behavioral performance both within and between groups. Our intent was to determine whether the electricfield exposure effects observed in the main 30 kV/m experiment would be seen in a second group of previously unexposed animals. MATERIALS AND METHODS
The two-sided, mirror image design of the experimental facility, which housed an independently functioning transformer and exposure apparatus on each side, permitted us to perform a crossover experiment. During the crossover experiment, the control (East) group from the main 30 kV/m experiment became the exposed group in the crossover, while the exposed (West) group from the main 30 kV/m experiment became the control group in the crossover. This was possible because the the social behavior of the previously exposed subjects (West group) had returned to normal baseline levels during the Post-Exposure period of the main experiment. In the crossover experiment, we exposed the East group of eight male baboons to a 60 Hz electric field (E-field) of 30 kV/m intensity (12 hours per day, 7 days per week) for 3 weeks, while the West group of eight animals was maintained in a shamexposure (control) condition. Only extremely low, incidental levels of magnetic field were generated by the apparatus used in this experiment [Coelho et al., 19911. Other than the reversal of control and exposed groups, and the duration of the exposure ( 3 weeks vs. 6 weeks), all procedures were identical for both experiments. As a basis for comparison, we used the Post-Exposure period of the main 30 kV/m experiment as the no-exposure Baseline for the crossover experiment. Facility Design
Descriptions of the exposure facility, its operating characteristics, and electric field quality control have been presented elsewhere [Cory et al., 1987; Coelho et al., 19911.Quality control of electric field characteristics and facility operations at Southwest Research Institute (SwRI) was monitored by a joint committee consisting of staff from
Electric Field Exposure and Social Behavior
397
the United States Department of Energy (DOE), the National Bureau of Standards, the Central Research Institute of the Electric Power Industry (CRIEPI) of Japan, and an independent consultant, W/L Associates, under contract to DOE. Experimental Subjects
There were 16 male baboons (Papio cynocephalus anubis) used in this experiment. All subjects were members of a single birth cohort and were 5 to 6 years of age (young adults) at the time they were assigned to the experiment [Coelho et al., 19911.Water and commercial primate diet were available to the animals ad libitum. Data Analysis
We measured the performance rates of the three categories of behavior (Passive Affinity, Tension, and Stereotypy) that were significantly affected by electricfield exposure in the main 30 kV/m experiment, using methods described previously by Coelho et al. [ 19911. We tested between-group differences in group performance rate means for each period of each of the three behavioral categories by two-sample t tests. Within-group comparisons between baseline and exposure periods were made by paired-comparison t tests. As in the main 30 kV/m experiment, the significance level was set at P < 0.05 (two-tailed). RESULTS
Results of the crossover experiment are presented in Figure 1. We have also included the results of the main 30 kV/m experiment for comparative purposes. The performance rates of the control (West) group exhibited little change from the Baseline to the Crossover exposure period, and none of the within-group changes in the control (West) group were statistically significant (Table 1, Fig. 1) from Baseline to the Crossover exposure period. During the Crossover exposure period, the exposed (East) group exhibited increased performance rates of all three criterion behaviors. Passive Affinity showed statistically significant between-group differences during Crossover exposure. Comparing within-group Baseline values to Crossover exposure values, the exposed (East) group exhibited a highly significant, 208% increase in the performance rate of Passive Affinity behaviors during electric field exposure (Table 1, Fig. 1). Tension increased by 40% and Stereotypy increased by 75% from Baseline to the Crossover exposure period. Although these increases were large, Tension and Stereotypy did not attain statistically significant between-group differences during Crossover exposure, nor did they exhibit statistically significant within-group changes over time as they had done in the main experiment (Table 1, Fig. 1). DISCUSSION
We previously reported that 6 weeks of exposure to both 30 kV/m and 60 kV/ m electric fields produced significant changes in the social behavior of young adult male baboons [Coelho et al., 1991; Easley et al., 19911. The crossover experiment described in this paper confirmed that 3 weeks of exposure to a 30 kV/m, 60 Hz electric field also produces i.ncreases in the rate of performance of the three criterion behaviors.
398
Easley et al.
24
1
Passive Afflnlty
6-
Tenaion
EeUGrap
4-
West Group
-E-fioldEapown
5.
m
.\
4-
:::::: ::.: :.:,:. .:.:
\
3.
2.
T
P < 0.05
1 1.
28
-
24
-
Stereotypy I
20-
16-
12-
8.
0
Pro-ErpOOUro
EXpOlUn
Maln 30 kVlm Expwlmont
POI1-Enpoaum
cmuovr
-
Buellno
f
EnpOSW.
f
CroBsover 30 kVlm Exporlnwnl
Fig. 1
Electric Field Exposure and Social Behavior
399
TABLE 1. Paired-Comparison t Test Values (t) and Significance Values (P)from Comparison of Mean Performance Rates During the Baseline Period With Mean Performance Rates During the Crossover Exposure Period, for each Group Separately* ~~~
East group Passive affinity Tension Stereotypy
t -1 1.84 -1.13 -2.1 1
West group P
t
0.00
- 1.69
0.30 0.07
0.98 0.91
P 0.13 0.36 0.30
*Only the East group was exposed.
Passive Affinity demonstrated statistically significant between-group and withingroup changes in response to electric field exposure. The measured within-group increase was greater than the within-group increase measured for this behavior category in the main 30 kV/m experiment [Coelho et al., 19911. When the previously unexposed East group was exposed to the 30 kV/m electric field during the Crossover, the baboons exhibited substantial increases in performance rates of Tension and Stereotypy behaviors, although the differences did not attain statistical significance, as they had in our other experiments. The difference between our previous studies [Coelho et al., 1991; Easley et al., 19911 and the current study in the length of E-field exposure may be reflected in the measured rates of Tension and Stereotypy behaviors during Crossover, i.e., longer exposures may have produced significant effects in these two behavior categories. We have suggested that these behavioral responses to E-field exposure could be the result of perception of the field and/or a direct effect on the central nervous system [Coelho et al., 1991; Easley et al., 19911.At present there are no data available to address or resolve that issue. Nevertheless, the clear alteration of social behavior patterns demonstrated in our three experiments suggests that exposure to E-fields affects central nervous system function by some as yet unknown mechanism. At present there are insufficient data to assess whether or not such disruptions are deleterious bioeffects resulting from exposure to strong, 60 Hz electric fields. ACKNOWLEDGMENTS
This research was sponsored jointly by the Office of Energy Management of the United States DOE and CRIEPI of Japan, and was conducted as contract DEACOI-80-RA50219. We would like to thank Dr. G.T. Moore, Dr. J.L. Orr, Dr. W.R. Rogers, Dr. L.L. Taylor, Mr. J.H. Lucas, and Mr. H.D. Smith for their assistance. We also acknowledge the comments and suggestions on the manuscript provided by members of the staff of CRIEPI. SwRI and SFBR are accredited by the American Association for Accreditation of Laboratory Animal Care and are in compliance with the requirements of the Animal Welfare Act.
Fig. 1. Means and standard errors for A) Passive Affinity, B) Tension, and C) Stereotypy behaviors, by experimental periods. The West group was exposed to the E-field during the first exposure period and the East group was exposed to the E-field during the second exposure period, as indicated by shaded boxes. Statistically significant between-group differences are indicated by P < 0.05.
400
Easley et al.
REFERENCES Coelho AM Jr, Easley SP, Rogers WR (1991): Effects of exposure to 30-kV/m, 60-Hz electric fields on the social behavior of baboons. Bioelectromagnetics 12: 117-135. Cory WE, Barsun HF, Lucas JH, Polonis JJ, Rogers WR (1987): High intensity 60-Hz electric exposure facility for nonhuman primates. In Anderson LE, Kelman BJ and Weigel RJ (eds): “Interaction of Biological Systems With Static and ELF Electric and Magnetic Fields. Proceedings of the 23rd Hanford Life Sciences Symposium.” Richland, WA: Pacific Northwest Laboratory, pp 101-1 10. Easley SP, Coelho AM Jr, Rogers WR (1991): Effects of exposure to 60-kV/m, 60-Hz electric fields on the social behavior of baboons. Bioelectrornagnetics 12:361-375.
