Smart meters and human health

Summary

Electrical utilities are deploying residential meters that transmit data to operate the network, using wireless communication in the radiofrequency (RF) range or Power Line Carrier technology (PLC) in the intermediate frequency range (30-100 kHz). On average, the duration of transmission is a few minutes per day. Smart meters do not change in a significant way a resident’s exposure to radiofrequency electromagnetic fields (RF-EMF).

Possible short-term and long-term health issues of RF-EMF have been studied extensively over the last decades. Tissue heating is the only recognized effect for the frequencies used by RF smart meters (electrostimulation for those used by PLC smart meters). RF-EMF exposure close to smart meters is many orders of magnitude lower than recommended limits and is too weak to have any measurable effect on the human body or any effect on human health. The use of smart meters is safe.

1. Introduction

Over the last decades, new generations of radiofrequency meters for transmitting electricity or gas consumption data have been installed in many countries. Smart meters have become a new source of exposure to radiofrequency electromagnetic fields (RF-EMF) within the homes and the deployment of this new technology has raised concerns among some people about potential health risks. Many have objected to their installation with their service provider and have used legal remedies to protect themselves.

This report aims to assess the health risks related to the presence of these smart meters in a residential environment.

2. Electromagnetic radiation

Radiofrequency electromagnetic fields (RF-EMF) (also called radiofrequency radiation) are electromagnetic waves just like infrared radiation, visible light, ultraviolet radiation, X-rays, and gamma rays. Electromagnetic waves travel at the same speed of approximately 300,000 km per second. A wave is defined by its frequency and its wavelength. There is a direct and inverse relationship between the frequency (expressed as cycles per second or Hertz) and the wavelength (measured in meters). The higher the frequency, the smaller the wavelength.

The higher the frequency, the higher the wave’s energy. Light is also granular or corpuscular: it comes in the form of photons, which are grains or packets of energy (quantum of energy). This energy is measured in electron volts (eV). Ionization requires an energy of about 10 eV. The energy level is decisive in understanding electromagnetic waves' effects on matter and on the human body.

RF-EMF effects on the human body have been studied for over one hundred years. These effects are well characterized, and national and international public health authorities have recommended safe exposure limits which are revised periodically.

Figure 1 shows, in decreasing order of energy, the names commonly used to designate electromagnetic waves and their corresponding effect on the human body.

Thus, gamma rays have the highest frequencies, the shortest wavelength, and the highest level of energy. Gamma rays, X-rays, and ultraviolet radiation have enough energy to cause instant chemical damage in living cells. This damage leads to multiple consequences among which short-term effects like a rapid inflammatory response (sunburn caused by ultraviolet radiation) or long-term effects as an increased risk of cancer. Some of the damage is repaired by body cells but damage builds up over time.

Visible light’s level of energy is not sufficient to produce cellular damage but is sufficient to stimulate the eye retina’s photoreceptors and allow vision. Blue light is the more energetic and red is the less energetic.

Infrared radiation and radiofrequency radiation do not have enough energy to affect matter. At a frequency of 900 MHz, the energy of the photon is 3.6 x 10^-6 eV which is about six orders of magnitude lower than the energy needed to ionize matter. Therefore, the energy is only transferred by way of heat. Even if the number of photons emitted per unit of time is increased (for example by increasing the power of an antenna), none of these photons will be able to affect matter, only heat production will be increased.

At extremely low frequencies, heat is no more the main effect on the body but rather the electric current that both electric and magnetic fields generate in the body.   

3. Radiofrequency smart meters

3.1.   Radiofrequency emissions from the smart meter

RF-EMF emitted by smart meters have been well characterized in many countries including Canada, Australia, Great Britain, France, and the United States [1-6]. Smart meters are equipped with one or more antennae allowing communication outside the home with the utility but also inside the home with other devices. Output power varies from one manufacturer to another and is typically about 250 to 500 mW for the 900 MHz transmission and generally less than 15 mW at 2.4 GHz to avoid interference with other common devices operating at this frequency within the home.  The 900 MHz frequency band is used to communicate with a local receiver outside the home whereas the 2.4 GHz is mostly used to communicate within the home. The power levels of smart meters are comparable to other common sources of our modern environment like mobile phones, wi-fi, and portable computers.

Unlike the main sources of RF-EMF in the environment like radio, television, and base stations, smart meters do not emit continuously. They only transmit for very short intervals. The duty cycle (i.e., the proportion of time the meter emits RF-EMF) is typically a few minutes per day. The duty cycle varies from one meter to another depending on its location in the mesh network. Laboratory measurements and home measurements have shown that the typical duty cycle of an electric smart meter is 0.1 to 0.2% and very rarely exceeds 1%.

The relevant value for assessing effects on the human body is the average power obtained by multiplying the power by the duty cycle. As an example, a smart meter with an output power of 0.5 W and a duty cycle of 0.2% produces an average power of 0.001 W. At 2.4 GHz, a typical output power of 0.01 W with the same duty cycle produces an average power of 0.000 02 W. To simplify, we can say that the average power of a smart meter lies between 0.02 mW to 1 mW.

To put this power into context, it should be recalled that the basal metabolism of the human body corresponds to a power of about 90 W in a 70 kg adult at rest. During a light effort, such as a normal walk, the power generated by the human body is 250 to 300 W. Thus, in a completely unrealistic scenario in which all the power of a smart meter antenna (up to 1 W) was absorbed by the human body, the heat deposited in the body would be negligible and without any measurable physiological effects.

3.2. Intensity of RF-EMF emitted by a smart meter.

The intensity of radiation at a given location is measured in watts per square meter (W/m²). This unit is technically called "power density". The radiation intensity decreases rapidly as one moves away from the source: when the distance doubles, the intensity decreases four times. The radiation pattern is generally asymmetrical, the emission being stronger in front of the device than behind.

Many studies have reported the average power density at various distances in front of smart meters. The reported intensities at one meter are in the range of 1 to 50 microwatts per square meter (µW/m²). To put these values in context, table I provides a few references.

3.3. Recommended exposure limits for RF-EMF

The International Commission on Non-Ionizing Radiation Protection (ICNIRP) recommends exposure limits for the public and workers. As a precaution, the limit for workers is set at a level 10 times lower than that which could lead to an increase in body temperature. For the public, an additional safety factor of 5 is applied.

The recommended limit for the public is 4.5 W/m² at 900 MHz and 10 W/m² at 2.4 GHz [7]. The limit is lower at 900 MHz to consider the fact that the absorption of energy by the body is more efficient at lower frequencies. 

The typical level of exposure one meter in front of a smart meter is 5 to 6 orders of magnitude less than the recommended limit for the public. These levels are far too low to have a measurable thermal effect on the human body.

4. Smart meters using PLC technology

The PLC technology consists of using the electrical network to propagate the signals by conduction in low-voltage electrical cables. Therefore, smart meters using this technology are not radio transmitters. However, they may be equipped with a radiofrequency module that communicates within the homes using the 2.4 GHz frequency, like the other types of smart meters described in this paper.

The signal sent by conduction in electrical cables uses frequencies in the range of 30 kHz to 100 kHz. The signal produces an electric field and a magnetic field of the same frequencies near the meter as any electrical device. At these frequencies, both fields must be considered separately and there are limits to be respected to prevent electrical stimulation.   The exposure limit values in force for this frequency band recommended by the International Commission on Non-Ionizing Radiation Commission [8] are 83 V/m and 27 µT.

PLC meters are being used in France. The French National Frequency Agency [9] has characterized the levels of electric field and magnetic field at the operating frequencies of the smart meters in use. At 20 cm from the surface, the intensity of the electric field component was of the same order of magnitude with or without PLC signals (0.8 vs 0.86 V/m) and about 100 times lower than the exposure limit.  The intensity of the magnetic field measured at the same distance (20 cm) showed a maximum of 0.8 x 10^-3 µT which is about 100,000 times below the exposure limit. At a distance greater than 1 meter, the electric field and the magnetic field are barely measurable, reaching the very low background levels produced by the meter itself (without PLC) and other electrical devices in the home. 

5. The search for biological effects other than thermal

For more than fifty years, studies have been conducted to detect possible non-thermal effects of RF-EMF. This research has intensified since the advent of mobile phones, mainly because, for the first time, the user's level of exposure far exceeded common levels found in the urban environment.

The RF-EMF emitted by mobile phones is not sufficient to cause heat perception, but the intensity of exposure on the surface of the head is about 5000 times higher than the ambient level measured in urban areas. Numerous experimental studies have been carried out at the cellular level (in vitro studies) as well as in animals and humans.  The extremely widespread use of mobile phones in the population for more than 30 years has also made it possible to study the potential long-term effects, particularly the risk of cancer.

Experimental studies are generally conducted at the highest possible exposure levels that can be achieved without inducing any significant thermal effects.  Epidemiological studies focus on mobile phone users since user exposure, as mentioned above, is relatively high.

Two areas of research were particularly examined: effects on the central nervous system and the risk of cancer.

5.1. Effects on the central nervous system

Most experimental studies in humans have used mobile phones at maximum power (about 1 W) placed a few centimeters from the head, which corresponds to intensities in the range of 1 to 10 W/m² for the scalp and the part of the brain exposed on the same side (corresponding to a specific absorption rate of 1 to 2 W/kg).

Experimental studies in human volunteers subjected to double-blind controlled laboratory tests have shown that these exposure levels (1 to 10 W/m²) are not perceptible to the subject and do not reproduce the symptoms sometimes claimed by some mobile phone users. These studies did not reveal any neurotoxic effects.

Several experimental studies have explored the potential effects of RF-EMF on specific neurophysiological functions. Some of them have reported neurophysiological or psychometric effects, particularly on the permeability of the blood-brain barrier, evoked potentials, electroencephalogram, brain blood flow rates, neuronal metabolic activity, and reaction time. However, due to the small magnitude of these effects, and especially the difficulty of reproducing them from one laboratory to another, these data are not yet conclusive [10-13]. Several studies are currently underway to assess these hypotheses.

5.2. The issue of hypersensitivity to electromagnetic fields

Some people say they are hypersensitive to electromagnetic fields. These people attribute symptoms to electromagnetic fields in their environment for which no precise medical diagnosis has been made.

The symptoms reported vary widely from person to person and are unspecific symptoms that can result from multiple medical conditions, psychosomatic disorders, and simple functional disorders.

Nevertheless, several hundred individuals who feel that they are hypersensitive have participated in provocation studies conducted in a controlled experimental situation. The results are largely convergent: subjects were unable to distinguish between actual and simulated exposure sessions and their symptoms were not different in the presence or absence of electromagnetic fields.  In addition, no changes in basic physiological functions (pulse, respiratory rate, blood pressure, temperature) could be detected. The biological tests remained normal. The presumed existence of hypersensitivity to electromagnetic fields is not currently based on any conclusive scientific or medical data [14] and for this reason, it is not a recognized medical diagnosis. Nevertheless, the symptoms felt, and the suffering of these patients are very real. The correct diagnosis remains to be established and could be different from one person to another.  It appears that a somatic symptomatology disorder based on a mistaken belief that the symptoms are caused by an environmental factor may be in play.

5.3. RF-EMF and cancer risk

The assessment of RF-EMF carcinogenicity has progressed significantly over the past 20 years. Nearly 200 epidemiological studies have been published on the subject, mainly among mobile phone users.  Brain cancers have been the most studied, but also several other cancers, in particular cancers of the salivary glands which are located close to the antenna.

5.3.1. Epidemiological studies

The most relevant observations are studies that have examined the evolution of brain cancer incidence over the past 30 years in populations. Given the very high proportion of users worldwide, the relatively high level of exposure of tissues near the antenna of the mobile phone (skin; salivary glands; brain), and the duration of exposure (more than 30 years in some countries), even a small increase in cancer risk would have measurably increased the incidence.  However, to date, brain cancer incidence has remained stable in most countries where such studies have been conducted [15-17]. This is good evidence of the absence of significant risk.

As for case-control epidemiological studies, the results do not allow to conclude that there is an increased risk of cancer. Some studies have reported positive statistical associations without being able to confirm a causal relationship. One of the largest studies (Interphone Study [18]) conducted by the International Agency for Research on Cancer (IARC) involving more than 5000 cases of brain cancer from 13 different countries showed, as the main result, a significant decrease of nearly 20% in brain cancer risk among mobile phone users.  However, in the same study, an increased risk was calculated in a subgroup of individuals who reported cumulative use of more than 1640 hours. In response to these equivocal results, IARC has classified RF-EMF as "possibly carcinogenic to humans". Since then, many studies have been published and the results do not support these initial findings [19]. Overall, most studies do not report an increased risk of cancer among mobile phone users.

5.3.2. Long-term experimental studies in animals

More than thirty long-term experimental studies in animals have been completed and the results are largely negative. Some studies have reported increases in cancer at specific sites, but these results are inconsistent [20]. The absence of a clear carcinogenic effect in animals is an important result because these studies are known for their very high sensitivity to detect carcinogenic effects.

5.3.3. Cellular studies (in vitro)

Cellular-scale studies have not demonstrated a plausible mechanism by which normal cells could be transformed into cancer cells by the action of RF-EMF. As mentioned above, radiofrequency energy is too low to break chemical bonds between atoms and molecules as do, for example, ultraviolet radiation, X-rays, and gamma rays. The energy of RF-EMF is lower than that of infrared radiation for which, even at high exposure (500 W/m²), no carcinogenic effects have been observed.

Overall, the data acquired to date suggest that there is no carcinogenic risk up to long-term exposure levels of a few W/m². This is an exposure level thousands of times higher than those measured near a smart meter.

5.4. Summary of the state of evidence on the health effects

Despite a considerable international research effort, no effects other than thermal could be clearly demonstrated for exposure levels of a few W/m² or less [7]. Some effects have been reported in several studies, but these effects are small in magnitude and difficult to reproduce from one experiment to the next. Research has not identified a mechanism of action that could lead to a particular physiological or pathological effect. To date, no symptoms or clinical signs can be reasonably attributed to RF-EMF levels that remain below recommended limits.   

As for the frequency range of 10 to 100 kHz associated with PLC technology, the electric and magnetic field exposure levels are very low and unlikely to cause any short-term or long-term biological or health effects. 

5.5. Special case of persons wearing implanted pacemakers or defibrillators

A study conducted by Hydro-Québec in Canada tested the ability of smart meters to interfere with the normal functioning of pacemakers and defibrillators [21]. Five different Medtronic models were placed at 10 cm from a smart meter and the pulse rate of the meter was artificially increased to three pulses per second. No interference was observed.

There is no study published about the interference of cardiac implants with smart meters using PLC technology. However, PLC technology uses the same frequency range as induction cooking. Induction cooking emits higher fields. In a study conducted in a hospital in France, 60 patients with pacemakers were tested using an induction cooker in different configurations including low and high power [22]. The maximum magnetic field in the 20-50 kHz range at the level of the pacemaker was 2.01 µT, which is higher than the 8 x 10^-3 µT measured at 20 cm of the smart meter [9]. No interference was observed.

6. Conclusion

The RF-EMF emitted by smart meters is a negligible source among all those already present in the environment, such as radio, television, and mobile phone networks. Despite intensive research over the last decades, no effects below the exposure limits have been identified. The RF-EMF intensity emitted by the smart meters is several orders of magnitude lower than the exposure limits. The level of exposure close to the meter is far too low to have any effect on human physiology and health.

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• Contact Author : M. PLANTE