Presentation on theme: "Thermal and Non-thermal Effects of Non-ionizng EMF"— Presentation transcript:
1Thermal and Non-thermal Effects of Non-ionizng EMF Henry LaiDepartment of BioengineeringUniversity of WashingtonSeattle, WAUSA
2Do non-thermal effects exist? Thermal effects are relatively easy to understand.-microwave cooking-heating causes cellular and physiological changesNon-thermal effects- biological responses not related to heating or increase in temperature.-difficult to proveDo non-thermal effects exist?
3Arguments for non-thermal effects: Effects at low intensityHeating effects different from EMF effectsModulations produce different effects atsame exposure conditions(4)ELF EMF has biological effects
5‘Microwave pulse’ hearing effect Auditory system responses to microwavepulses at a threshold of 0.6 mJ/g/pulse.-thermoelastic effect-micro-thermal effects
6The 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.
7Dawe, Smith, Thomas, Greedy, Vasic, Gregory, Loader, de Pomerai (2006) A small temperature rise maycontribute towards the apparent induction by microwaves of heat shock gene expression in the nematode Caenorhabditis elegans. Bioelectromagnetics 27(2):88-97.“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.”
8Heating 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 3oC to produce the same effect of a 0.5oC increase by EMF; EMF enhanced growth and development of C. elegens, whereas heating produced the opposite effects.
9But, 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.
10Modulations produce different effects at same exposure conditions- e.g., frequency, exposure system Frey (1975)-BBB- pulsed field more effective than CWOscar and Hawkins (1977)-BBB- pulsed field more effective than CWSanders (1985)-brain metabolism- 500 pps more effective than 250 pps modulationArber and Lin (1985)-neuron activity- AM increase; CW decreaseLai (1988)-hippocampal acetylcholine-pulsed- CW no effectD’Ambrosio (2002)-genetic effect- modulated field- CW no effectHuber (2002)-EEG- modulated field-CW no effectHoyto (2008)-lipid peroxidation, caspase 3 activity- modulated field- CW no effectLuukkonen (2009)-free radicals-CW- modulated field no effect
11Biological effects of ELF EMF are well established. ELF EMF cannot produce significant thermal effect.
12Arguments for non-thermal effects: Effects at low intensityHeating effects different from EMF effectsModulations produce different effects atsame exposure conditions(4)ELF EMF effects
13Is thermal/non-thermal consideration a necessary condition for EMF exposure standard setting?
14Is 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.
15The 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 rat’s 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.”
16de 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/cm2 (SAR 3.2 W/kg) for 225-MHz, 57 mW/cm2 (SAR 7.4 W/kg) for 1300 MHz, and 140 mW/cm2 (SAR 4.3 W/kg) for 5800 MHz, when body temperature increased by 1oC.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 1oC.
17Thomas 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.
18Does 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).
21Effects of long-term exposure D’Andrea et al. (1986a) 2450 MHz, 7 hrs/day, 7 days/wk, 14 weeks, 0.7 W/kg- disrupted operant behavior.D’Andrea et al. (1986b) MHz, 7 hrs/day, 7 days/wk, 90 days, 0.14 W/kg- small disruption in operant behavior.“The threshold for behavioral and physiological effects of chronic RFR exposure in the rat occurs between 0.5 mW/cm2 (0.14 W/kg) and 2.5 mW/cm2 (0.7 W/kg).”
22Interactions 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/cm2).There are many reports of EMF interaction with drugs/chemicals, stressors, ionizing radiation, etc.