RF Biological Effects
- Chapter 8.1
- Studies and Reports
- Electrical Properties of Living Matter
- Thermal Effects of RF Radiation
- Interaction of Fields and Biological Systems
Radiation Natural radiation was the only source of human exposure until the latter part of the nineteenth century when Thomas Edison invented the electric light. Most natural radiation of significance occurs in a small part of the lowermost frequency spectrum (electrostatic to about 5 kHz) and in the uppermost part of the spectrum (above 10 THz or 1013 Hz); man-made radiation dominates 50 Hz to 300 GHz, and accounts for some radiation in the lower and upper spectrum. Most natural radiation below 5 kHz results from lightning. Average rate of global lightning strikes is about 100 bolts per second (cloud to ground and cloud to cloud). Some natural radiation below 5 kHz results from pulsations in the earth's magnetosphere during intense solar storms -- such as when the Aurora over the poles (north and/or south) is active. Radiation is categorized as either non-ionizing or ionizing radiation. Ionizing radiation has enough energy (high enough in frequency) to break atomic bonds by removing one or more electrons (ionization is adding or removing electrons) and creating a charged atomic particle; non-ionizing radiation does not. The higher the frequency (the shorter the wavelength) the greater the energy and ionization.
Studies and Reports Microwave traffic radar has been linked to several adverse health effects by a number of police officers who operated traffic radars (low level microwave radiation) over a long period (hours at a time for years). To date the scientific community cannot establish a mechanism that links traffic radar to adverse health effects (that does not mean one does not exist). Data on traffic radar and health is pitifully scarce. The U.S. Air Force sponsored a study of rats exposed to pulsed microwaves at 24.5 GHz. Note that K band traffic radars operate at around 24.025 - 24.250 GHz (475 - 250 MHz lower); also the study used pulsed microwaves and traffic radar is continuous (not pulsed). The research cost 54 million dollars and was conducted by the University of Washington School of Medicine in Seattle and published in 1984. The study showed a significant increase in malignant tumors and noted affects in the adrenal glands and the entire endocrine system. This investigation suggests the maximum allowable exposure for humans set by the ANSI (American National Standards Institute) and IEEE (Institute of Electrical and Electronic Engineers) are too low; human exposure limits should be more stringent. The London Times reported on 1998 December 31 that Dr. Henry Lai, an expert in non-ionizing radiation and professor at the School of Medicine and College of Engineering at the University of Washington, Seattle, announced that low-level microwave radiation can split DNA molecules in the brains of laboratory mice. DNA is Deoxyribonucleic acid; a complex, usually helical shaped chemical compound that is the substance that makes the organic matter of genes and chromosomes. Splitting DNA molecules in the brain is associated with Alzheimer's and Parkinson's Disease, and cancer. The cellular telephone industry supported Dr. Lai's research grant, but suppressed the report's publication. Electronic Engineering Times reported 2001 June 11 the Air Force Research Laboratory (AFRL) has developed a non lethal antipersonnel millimeter (mm) band "heat ray" intended for use on battle fields or against hostile crowds. A 3 x 3 meter (about 10 x 10 feet) antenna (mounted on a Humvee, aircraft, helicopter, or ship) can be swept across a crowd with a 95 GHz beam that induces heating in the skin. Reports indicate a 2 second burst can heat the skin to 130°F -- inflicting pain with an intense burning sensation. Officials claim the energy only penetrates the top 1/64 inch (0.4 mm) of the skin and is not harmful to internal organs (they have not proved to me the eyes are not vulnerable to damage). Operating range is believed to be around 700 yards (640 meters) to 1090 yards (1000 meters); rain, sea spray, fog, and humidity will reduce range. Possible countermeasures include shielding the energy using very thick clothing, a metallic sheet (aluminum foil), or a metal trash can lid. Many studies on health effects and exposure to electromagnetic fields conducted since 1948 have reached varying and sometimes contradictory conclusions. Much of the early research concentrated on the thermal heating affects of electromagnetic radiation; some later studies indicated reactions to EMF exposure not explained by thermal heating. Experts do not always agree on the levels or types of electromagnetic fields that affect health.
Electrical Properties of Living Matter Living matter exhibits many electric properties as well as generates various, relatively small, electromagnetic fields. Medical doctors use known and well-documented electrical properties of the body to determine health and diagnose problems. This section is a brief sample of some electrical properties of living matter.
- Nerve fibers consist of cylindrical membranes with one conducting fluid
inside another conducting fluid and a potential difference of about 0.1 volts
between the fluids. A pulse causes the membrane between the fluids to
temporarily become more permeable to ions and the voltage drops. A pulse travels
approximately 98 feet per second (30 m/s) or about 67 miles per hour (108 kmh).
- Mechanical energy from bone bending and stress creates weak electrical
potentials (voltages) of a few millivolts across a centimeter and relatively low
- Electrocardiographs (EKGs) measure potential differences (voltages) between
the chest and back to study heart functions. The human heart also has an
electric field near the surface (of the heart) that is between 1 and 10 volts
per meter (V/m).
- Electroencephalographs (EEGs) measure potential differences, on the order of microvolts, in the scalp and are a meager measures of brain functions. EEG patterns (brain waves) are different for every person, similar in twins, and similar for certain brain disorders such as epilepsy, brain tumors, brain damage, encephalitis, systemic diseases (toxemia and diseases of liver and kidneys). When resting but not asleep, the back part of the head will register alpha waves (or alpha rhythms) that have a frequency of 8 to 12 hertz. Beta waves, 18 to 25 hertz, relate to sensory functions and are smaller in magnitude than alpha waves. People in comas have patterns with 1 to 3 hertz rates near the damaged area of the brain. Theta waves are 4 to 7 hertz -- normal in infants and young children but abnormal in adults.
Thermal Effects of RF Radiation Electromagnetic energy is well known to cause thermal heating in living tissue. Microwave ovens use electromagnetic energy to heat and cook food. Microwave ovens (introduced by Raytheon in 1947) are basically magnetron oscillators (a radar transmitter tube/cavity) operating at 2.45 GHz (some models introduced in the late 1990's transmit at 5.8 GHz). The amount of heating that takes place is a function of transmit power and duty cycle (time). Maximum surface heating due to RF exposure of a typical human occurs at frequencies of around 30 to 120 MHz. Tissue heating depends on the frequency of the source and the dielectric constant, water content and thickness of the tissue. The more conductive the tissue the more energy absorbed and heat generated. It requires a relatively large amount of radiation to heat tissue. Radiation levels too low to produce heat may have other effects at a cellular level, although not all experts accept this. Some experts believe most non thermal health effects require much higher field levels compared to thermal heating effects. Fields strong enough to cause heating require hundreds to thousands of watts. Localized heat of about 1 watt per kilogram (0.45 W/lb) can damage tumors. The temperature of the tumor is raised to between 43 and 45 degrees Celsius (109 and 113 degrees Fahrenheit). The FCC allocates frequency bands for medical use that include 13.56, 27.12, 40.68, 915, and 2,450 MHz (some microwave ovens operate at 2.45 GHz); other frequencies have shown better results in some cases. Fields that cause mild heating can promote tissue healing or relax muscles.
Interaction of Fields and Biological Systems Weak RF fields insufficient to cause heating but strong enough to induce peak potentials of 1 to 1.5 millivolts per centimeter (0.10 to 0.15 V/m) can promote healing of broken bones. Experiments have shown osteoporosis, the loss of bone mass, can be halted or reversed by pulsed RF radiation. The shape and timing of pulses is extremely significant, and different, to promote bone healing or affect osteoporosis. Some studies indicate there are reactions to RF exposure not explained by thermal heating. Strong RF fields heat tissue by vibrating molecules of the tissue. Weaker fields can induce electrical currents in or on tissue, the stronger the field the larger the induced current. Electric and magnetic fields can produce weak Lorentz forces that may affect charged particles (ions) on a molecular scale. The Lorentz force is the force on a charged particle in motion due to the presence of an electric and magnetic field, and may boost or inhabit cell chemistries by pumping ions. Listed below is a sample of some observed affects of electromagnetic radiation on living cells. Most if not all effects depend greatly on frequency, modulation, and magnitude of the field.
- split DNA molecules in the brains of laboratory mice
- Peral chain -- randomly suspended particles (such as fat globules
and E. coli bacteria) align with each other in direction of field.
- Non spherical particles (such as E. coli) line up either perpendicular
or parallel to electric field depending on frequency.
- Particle movement.
- Change in natural shape of cells.
- Cell death from membrane damage.
- Fusion of cells.
RF radiation has been linked to biochemical effects, immunological effects, Alzheimer's and Parkinson's Disease, cancer, cataracts, EEG effects and behavioral changes, to name a few. Studies from the old Soviet military suggest that some frequencies and modulations cause behavioral changes in humans. In 1990 the U.S. military was reported to be planning microwave radiation experiments on animals to study behavioral effects. Some health effects seem to take place in small bands or windows of frequencies, modulations, and magnitudes. For example, nerve tissues affected by continuous 60 hertz fields are unaffected by 55 or 65 hertz fields. Some experiments have shown for some narrow frequency bands and specific modulation types; a smaller field affects cells more than a stronger field. Several factors should be considered to determine electromagnetic radiation exposure and include; Field Type -- Frequency and modulation; modulation introduces other frequency components.
Distance from Source -- Field magnitudes change greatly with distance.
Exposure Time -- Exposed to large fields for a short period of time or exposed to small fields for a long period of time.
Also see National Technical Information Service (NTIS) publication number PB95-261350 titled Occupational Exposure of Police Officers to Microwave Radiation from Traffic Radar Devices (available on the Internet -- see Web Links page).
Chapt 8.1 -- RF Biological Effects