Presentation on theme: "Thermal and Non-thermal Effects of Non-ionizng EMF Henry Lai Department of Bioengineering University of Washington Seattle, WA USA."— Presentation transcript:
Thermal and Non-thermal Effects of Non-ionizng EMF Henry Lai Department of Bioengineering University of Washington Seattle, WA USA
Thermal effects are relatively easy to understand. -microwave cooking -heating causes cellular and physiological changes Non-thermal effects- biological responses not related to heating or increase in temperature. -difficult to prove Do non-thermal effects exist?
Arguments for non-thermal effects: (1)Effects at low intensity (2)Heating effects different from EMF effects (3)Modulations produce different effects at same exposure conditions (4)ELF EMF has biological effects
Microwave pulse hearing effect Auditory system responses to microwave pulses at a threshold of 0.6 J/g/pulse. -thermoelastic effect -micro-thermal effects
The Case of David de Pomerai De Pomerai et al. (Nature 405: , 2000)- reported an increase in a molecular stress response (heat shock gene expression) in worms after exposure to a RFR at a SAR of W/kg.
Dawe, Smith, Thomas, Greedy, Vasic, Gregory, Loader, de Pomerai (2006) A small temperature rise may contribute towards the apparent induction by microwaves of heat shock gene expression in the nematode Caenorhabditis elegans. Bioelectromagnetics 27(2): We conclude that our original interpretation of a non- thermal effect of microwaves cannot be sustained; at least part of the explanation appears to be thermal.
Heating effects different from EMF effects Wachtel (1975) Seaman & Wachtel (78)- activity of neurons insolated abdominal ganglion of Aphysia- heating had opposite effect. de Pomerai (2000, 2003)- needed thermal heating of 3 o C to produce the same effect of a 0.5 o C increase by EMF; EMF enhanced growth and development of C. elegens, whereas heating produced the opposite effects.
But, microwave/RF heating is not the same as heating. RFR energy absorption pattern in the body is not uniform. (Chou, C.K., Guy, A.W., McDougall, J., Lai, H. Specific absorption rate in rats exposed to 2450-MHz microwaves under seven exposure conditions. Bioelectromagnetics 6:73-88, ) It is not possible to simulate RF heating. Even if heat is removed when exposed to RFR, i.e., no significant increase in temperature is detected, thermoregulatory responses are activated which can in turn lead to alterations in other physiological responses.
Modulations produce different effects at same exposure conditions- e.g., frequency, exposure system Frey (1975)-BBB- pulsed field more effective than CW Oscar and Hawkins (1977)-BBB- pulsed field more effective than CW Sanders (1985)-brain metabolism- 500 pps more effective than 250 pps modulation Arber and Lin (1985)-neuron activity- AM increase; CW decrease Lai (1988)-hippocampal acetylcholine-pulsed- CW no effect DAmbrosio (2002)-genetic effect- modulated field- CW no effect Huber (2002)-EEG- modulated field-CW no effect Hoyto (2008)-lipid peroxidation, caspase 3 activity- modulated field- CW no effect Luukkonen (2009)-free radicals-CW- modulated field no effect
Biological effects of ELF EMF are well established. ELF EMF cannot produce significant thermal effect.
Arguments for non-thermal effects: (1)Effects at low intensity (2)Heating effects different from EMF effects (3)Modulations produce different effects at same exposure conditions (4)ELF EMF effects
Is thermal/non-thermal consideration a necessary condition for EMF exposure standard setting?
Is thermal/non-thermal consideration a necessary condition for EMF exposure standard setting? My answer is no. Standards should base on at what level of exposure biological/health effects are observed.
The de Lorge Experiments de Lorge and Ezell (1980) trained rats on an auditory observing- response task. Rats were then irradiated with 1280-MHz or 5620-MHz RFR during performance. Disruption of behavior was observed at SAR of 3.75 W/kg for 1280-MHz and 4.9 W/kg for 5620-MHz. Disruption occurred within minutes of exposure. It is concluded that the rats observing behavior is disrupted at a lower power density at 1.28 than at 5.62 GHz because of deeper penetration of energy at the lower frequency, and because of frequency- dependent differences in anatomic distribution of the absorbed microwave energy.
de Lorge (1984) trained monkeys on the auditory observing- response task. Monkeys were exposed to RFR of 225, 1300, and 5800 MHz. Disruption of performance was observed at 8.1 mW/cm 2 (SAR 3.2 W/kg) for 225-MHz, 57 mW/cm 2 (SAR 7.4 W/kg) for 1300 MHz, and 140 mW/cm 2 (SAR 4.3 W/kg) for 5800 MHz, when body temperature increased by 1 o C. Conclusion: Disruption of behaviour occurred when an animal was exposed at a SAR ~ 4 W/kg (whole body average). Disruption occurred after minutes of exposure and when body temperature increased by 1 o C.
Thomas et al. (1975) tested 5-10 min after 30 min exposure to pulsed 2450-, 2860-, 9600-MHz RFR. DRL response disrupted at 2450-MHz > 2 W/kg, 2860 MHz >2.7 W/kg, 9600-MHz >1.5 W/kg. Schrot et al. (1980) bar press for food after 30 min exposure to pulsed 2800-MHz RFR disrupted at SARs of 0.7 and 1.7 W/kg.
Does RFR produce behavioral effects below 4 W/kg after short-term exposure? YES In many instances, effects on behavior were observed at a SAR less than 4 W/kg. (DeWitt et al.  0.14 W/kg; Gage  3 W/kg; King et al.  2.4 W/kg; Lai et al.  0.6 W/kg; Mitchell et al.  2.3 W/kg; Navakatikian and Tomashevskaya  W/kg; Schrot et al.  0.7 W/kg; Thomas et al.  1.5 to 2.7 W/kg; Wang and Lai  1.2 W/kg).
Effects of long-term exposure DAndrea et al. (1986a) 2450 MHz, 7 hrs/day, 7 days/wk, 14 weeks, 0.7 W/kg- disrupted operant behavior. DAndrea et al. (1986b) 2450 MHz, 7 hrs/day, 7 days/wk, 90 days, 0.14 W/kg- small disruption in operant behavior. 2 The threshold for behavioral and physiological effects of chronic RFR exposure in the rat occurs between 0.5 mW/cm 2 (0.14 W/kg) and 2.5 mW/cm 2 (0.7 W/kg).
Interactions with Other Environmental Factors Example: Kues and Monahan  and Kues et al. [1990; 1992] reported synergistic effects of drugs on corneal endothelium damages and retinal degeneration in the monkey induced by repeated exposure to RFR. They found that application of the drugs timolol and pilocarpine to the eye before RFR exposure could lower the threshold of the RFR effect by 10 folds (from 10 to 1 mW/cm 2 ). There are many reports of EMF interaction with drugs/chemicals, stressors, ionizing radiation, etc.