do display screens give out harmful radiation factory

In this post, I’m going to tell you how computer monitors emit EMF radiation, how much they emit, how you can test this, and what you can do about it.

(Just a quick note before we move on. I would love for you to take just a minute and check out Nicolas Pineault’s groundbreaking E-book “A Non-Tinfoil Guide To EMFs.” It is the most entertaining and informative book on EMF radiation you’ll ever read, I promise.)

There are primarily three types of radiation sources that a computer monitor is likely to have, UV light radiation, x-ray radiation, and EMF radiation. Which radiation, and how much they emit, will depend largely on the monitor. Let’s talk a little bit about each kind.

There are basically two categories of monitors: cathode-ray tubes, and the flat-screen monitors that you see today, which are typically either LED or LCD based screens.

Prior to about 2001, almost all monitors were using cathode-ray tube (CRT) technology to power the screens. However, these types of monitors generate, and leak, small amounts of highly dangerous X-Ray Radiation. Although this had been recognized since the 60’s as being dangerous, it was not until the late 1990’s that manufacturers really fell under scrutiny for continuing to make a knowingly dangerous product.

This led to the manufacturing of Light Emitting Diode (LED) and liquid crystal display (LCD), which is what I used for nearly all modern monitors (and televisions)

Exposure to x-radiation is obviously extremely harmful and is an unfortunate bi-product of older style cathode ray tube (CRT) type monitors. The electronics in these old monitors generated extremely high voltages that would often result in x-ray radiation.

Although x-radiation that you could receive from one of these older style CRT monitors is dangerous and harmful, it is much less than you would receive from a medical x-ray machine or the x-ray at the dentist. This is the reason that they have you wear led vests to protect your body from the radiation.

Later versions of CRT monitors were slightly safer, as manufacturers began to take steps to reduce this x-ray radiation by adding lead to the cathode ray tube, which helped to cut down on this issue.

The EMF meter that the gentleman is using in this video is the older version of the Trifield meter, the company now has the new TriField TF2 (read my review), but we’ll talk about that a bit more down below in the section about measuring computer monitor radiation.

Ultraviolet light (UV) is much less harmful than x-ray radiation, but high amounts over a long period of time can still certainly cause harm. Some monitors actually have a fluorescent lamp that is part of the illumination. When the ultraviolet light strikes a white phosphor, the visible light that you see is created, but it has the side effect of sometimes leaking ultraviolet light out.

Luckily they make screen protectors for computer monitors that not only block 100% of the UV light but also help to filter out blue lights that can cause computer vision syndrome (CVS) from longterm exposure to computer monitors.

The EMF Radiation from your computer monitor will be relatively small and come from circuitry in the back of the unit. As you can see from the video above when he is testing an LCD monitor, there is still a noticeable amount of EMF radiation, but you have to be quite close.

This amount of radiation is enough to cause damage over time. In fact, a study showed that the radiation emitted from a monitor was enough to destabilize the oxidant/antioxidant balance in the cornea’s of rats over even a small amount of time.

The Long Island Power Authority did a study where they measured the average EMF radiation from many home appliances. Although they did not specifically test LCD or led computer monitors, they did test led and LCD televisions. Here are the numbers they came up with at the following distances:

As you can see, there is quite a large amount of EMF radiation at VERY close distances, but if you sit at least three feet away from the screen, you will not much need to worry about EMF radiation exposure. Be sure that you don’t sit so far away that you strain your eyes, but do keep at least 3 feet between you and the screen.

This applies to almost anything that you want to test, but you first need to start by getting a high-quality EMF meter. I personally use, and love, the new TriField TF2 (read my review). It is super easy to use, incredibly accurate, and measures every kind of EMF radiation, which you’ll realize is really important. If you need to start with a lower cost version I also like the Meterk (read my review).

Getting a good EMF meter is one of the absolute best things you can do if you care about the dangers of EMF radiation. Whether it’s figuring out how much radiation your Smart Meter is emitting, or testing to see if your microwave is leaking radiation, or comparing cell phone radiation, having a good EMF meter is the first step in knowing what the problem is, and knowing if your solutions are working.

Now, to test the radiation from a computer monitor, start by turning the monitor off, and getting a baseline reading near it. Then, turn the monitor on and give it a few seconds to boot up.

Start from about 5 feet away, and slowly move towards the monitor with your meter. Take notes of the radiation levels at different distances and note how it exponentially increases as you get within a few inches.

First of all, computer monitors do emit a relatively small amount of EMF radiation at reasonable distances. So the absolute best thing you can do is keep at least a reasonable distance (3 feet or more) between you and the monitor whenever possible.

They don’t seem to make a good shield for computer monitors that are actually intended to block EMF radiation, but they do make this window film that you can pick up on Amazon, that you could cut to fit the size of your monitor if you really wanted to reduce the amount of radiation you’re exposing yourself to.

Although it won’t block radiation, if you are staring at a computer or tv quite a bit during your day, you should consider picking up a pair of glasses that block the blue light rays. This will help protect your eyes from long term exposure.

According to the American Academy of Ophthalmology (AAO), "there is no convincing scientific evidence that computer video display terminals (VDTs) are harmful to the eyes."  The common complaints of eye discomfort and fatigue are associated with ergonomic factors such as distance from the person to the monitor, monitor height and brightness, etc.

I have a colleague who is pregnant and who types at a computer. How much radiation does her baby receive at a typical computer? Is there a lead shield that she could wear? Like an apron?

Regulations of the US Department of Health and Human Services require manufacturers to test computer monitor emissions for radiation and to label them attesting to the fact that they have been found to meet the standards of Title 21 of the Code of Federal Regulations. You should be able to find this label on the rear of the computer monitor or the computer processor. Health studies of pregnant women who work with VDTs have not found harmful effects on the women or on their children. Heavy lead aprons or other shields are not considered necessary for units that meet the x-ray emission standards of 21 CFR. Such shields may actually be counterproductive from an ergonomic point of view.

Radiation emissions from VDTs (for example, television sets and computer monitors) are regulated by the US Food and Drug Administration (FDA) and manufacturers are required to test and label these products.  Regulations limit radiation emissions from electronic products to levels considered safe.

I have heard a lot of answers about the ill effects of computer radiation but almost all that I have read claim no certainty in their answers. Has there been any valid and indisputable answer to this?

This means that if there are health risks they are too small or of a kind that have not been detected by current methods. Scientists often say that they "cannot disprove a negative," meaning that it is not logically possible to prove that something does not exist. This is because the list of things to be disproved can be endless, and the type and level of sensitivity of the tests that are used can always be improved upon.

I"m getting a computer for my child and would like to know which type of monitor/computer is safest in terms of the different types of radiation that exist. I was told years ago that the flat screens had a different, yet worse, type of radiation. Are there two types of radiation, and is this type worse?

All television receivers (including computer monitors), regardless of type, must meet a mandatory federal performance standard so any x-ray emissions, if they exist at all, must be at very low levels.  I am unaware of two types of radiation, unless you categorize the visible light which you see on the television screen as one type, which is, in fact an electromagnetic radiation; You can also consider radiowaves, which are also electromagnetic radiation. Both of these types of radiation are nonionizing and generally considered safe unless one is exposed to very intense levels.

All television receivers (including computer monitors), regardless of type, must meet a mandatory federal performance standard so any x-ray emissions, if they exist at all, must be at very low levels. The key point is that the emission standard is for "any point on the external surface" which means whether someone is in front of, to the side of, or behind the display or receiver, he/she is protected against any potential emissions of the display to the same degree.

My mom worries about the effects of computer radiation. She says that I am putting my health at risk by being on my PC more than four hours a day. Is this true?

The radiation emission from any computer is RF (radiofrequency) waves. There is no proof that these are harmful unless the intensity is high enough to warm tissue (like a microwave oven). You are not putting yourself at risk (from radiation) by being on your computer more than four hours a day.

My grandchildren often sit with their laptop computers in their laps. Is there any danger to their health and reproductive organs from low-level radiation that may be reaching them?

The only measurable radiation emission from a laptop computer is radio waves. We are constantly exposed to such radiation from all directions and multiple sources, including radio and TV signals, electronic appliances, etc. Current data indicate that these are not harmful to our health. There is, however, quite a bit of heat generated within the laptop while it is on. It is for this reason manufacturers recommend against extended periods of use with the computer on your lap.

The information posted on this web page is intended as general reference information only. Specific facts and circumstances may affect the applicability of concepts, materials, and information described herein. The information provided is not a substitute for professional advice and should not be relied upon in the absence of such professional advice. To the best of our knowledge, answers are correct at the time they are posted. Be advised that over time, requirements could change, new data could be made available, and Internet links could change, affecting the correctness of the answers. Answers are the professional opinions of the expert responding to each question; they do not necessarily represent the position of the Health Physics Society.

Since the advent of modern flat-panel screens, the vast majority of computer monitors have few, if any, radiation safety issues. The older technology used with vintage monitors, however, does have a potential for emitting certain types of harmful radiation, though manufacturers were aware of the risks and designed them to be safe. Overall, radiation safety issues from monitors are very minor and easily mitigated.

Monitor Types Computer monitors have used two basic types of technology: traditional cathode-ray tubes and more modern flat-screen designs. Before 2000, most computer equipment makers produced CRT-based monitors. These create images by sending a high-voltage beam of electrons in a vacuum tube to a phosphor screen, causing it to glow. The high voltage generates weak forms of radiation, a fact manufacturers have recognized since color TVs became widespread in the 1960s. Flat-screen monitors, by contrast, dispense with the CRT, creating images using a finely detailed grid of liquid crystals. Inside a flat-screen monitor, a bright lamp produces white light, which the liquid crystals filter into a broad range of colors. Although this technology uses low voltages, some of the lamps used produce mild radiation.

Radiation Types The radiation that comes from computer monitors takes the form of X-rays and ultraviolet light. This is not the same radiation normally associated with radioactive materials such as uranium, although it is associated with long-term exposure risks to living things. Of the two radiation types, X-rays are more harmful as they have more energy. Where monitor designs have the potential to produce X-rays or UV, the manufacturer adds materials that block the radiation, greatly reducing the safety issue.

X-Rays Traditional CRT-based monitors use high voltages that generate X-rays. The voltages used in black-and-white monitors is much lower than that found in color models, so X-rays are an issue only for the latter type. X-rays from a computer monitor are much weaker than those produced in a medical X-ray, as the operating voltage is lower and the radiation is a side effect, not the intended purpose of the design. CRT manufacturers solved the X-ray problem by adding lead to the glass picture-tube material.

Ultraviolet Although ultraviolet light is less harmful than X-rays, high levels of UV can burn skin and even cause blindness. Some flat-panel computer displays employ a fluorescent lamp as a bright light source. In the lamp, ultraviolet light strikes a white phosphor, creating visible light, but a small amount of the UV also escapes. In most LCD monitor designs, a layer of plastic absorbs the UV, minimizing the safety risk. Some flat-screen computer monitors use light-emitting diodes in place of fluorescent lighting, eliminating the UV problem completely.

Smoke detectors: most smoke detectors available for home use contain americium-241, a radioactive element. Unless tampered with, smoke detectors pose little to no health risk; a smoke detector’s ability to save lives far outweighs the health risks from the radioactive materials. For more information on smoke detectors, visit Americium in Ionization Smoke Detectors.

Clocks and watches: some luminous watches and clocks contain a small quantity of hydrogen-3 (tritium) or promethium-147. Older watches and clocks (made before 1970) may contain radium-226 paint on dials and numbers to make them visible in the dark. Avoid opening these items because the radium could flake off and be ingested or inhaled. Learn more about tritium and radium on the Radionuclides webpage.

Older camera lenses: some camera lenses from the 1950s-1970s incorporated thorium into the glass, allowing for a high refractive index while maintaining a low dispersion. The health risk from using older camera lenses is low; the radiation received when using a thoriated lens camera is approximately equal to natural background.

Gas lantern mantles: older, and some imported, gas lantern mantles generate light by heating thorium (primarily thorium-232). Unless gas lantern mantels are used as the primary light source, radiation exposure from thorium lantern mantles is not considered to have significant health impacts.

Televisions and monitors: Flat-screen televisions and monitors (e.g., LCD, OLED, plasma) do not use cathode ray tubes (CRTs) and therefore do not produce ionizing radiation. Older televisions and computer monitors that contain CRTs may emit x-rays. X-ray emissions from CRT monitors are not recognized as a significant health risk.

Sun lamps and tanning salons: the ultraviolet rays from sun lamps and tanning salons are as damaging to skin as the ultraviolet rays of the sun. In fact, warning labels are required which begin "DANGER—Ultraviolet radiation". You can learn more about performance standards for these devices from the Food and Drug Administration (FDA).

Glass: glassware, especially antique glassware with a yellow or greenish color, can contain easily detectable quantities of uranium. Such uranium-containing glass is often referred to as canary or vaseline glass. In part, collectors like uranium glass for the attractive glow that is produced when the glass is exposed to a black light. Even ordinary glass can contain high-enough levels of potassium-40 or thorium-232 to be detectable with a survey instrument. However, the radiation received when using glassware – even canary or vaseline glass – is unlikely to exceed background radiation levels.

Fertilizer: Commercial fertilizers are designed to provide varying levels of potassium, phosphorous, and nitrogen to support plant growth. Such fertilizers can be measurably radioactive for two reasons: potassium is naturally radioactive, and the phosphorous can be derived from phosphate ore that contains elevated levels of uranium. Learn more about Radioactive Material From Fertilizer Production.

EXIT signs: Some EXIT signs contain the radioactive gas called tritium, allowing them to glow in the dark without electricity or batteries. The tritium used in EXIT signs gives off low-level beta radiation, causing a light-emitting compound to glow. Tritium EXIT signs do not pose a direct health hazard, as the beta radiation can be stopped by a sheet of paper or clothing. However, tritium EXIT signs must not be disposed of in normal trash. For more information on tritium EXIT signs, see the Nuclear Regulatory Commission’s page on tritium EXIT signs.

No, but their older counterparts, Cathode Ray Tube (CRT) monitors, do give off a small amount of radiation. The streams of electrons hitting the phosphor in the screen produce X-rays, but these are way below harmful levels.

Everybody knows by now that electronic devices with displays like cell phones and computers give off radiation and people have been looking for ways to reduce their exposure. A NASA study is claimed to report that some plants absorb this harmful radiation and protect the user. Cactus in particular were very efficient at absorbing radiation.

Cactus is well known as an efficient absorber of radioactive waves, thanks to an in-depth study done by NASA. It is especially useful for absorbing the radiation that is produced by computers.

Cactus also absorbs the radiation that may be coming from nearby cell phone towers, so it is truly a plant that protects you from a wide range of radiation.

When you hear a story such as this, it is very useful to break it down into components. In order for a cactus to protect you from radiation coming from a computer several things need to be true.

However, light is not the radiation that is of concern here. People are concerned about electromagnetic (EM) energy, but the claims for cactus protection never seem to mention EM radiation. I suspect the authors making the claims don’t understand different forms of radiation.

400 to 800 THz electromagnetic radiation. This is the visible light given off by the laptop’s screen that makes it possible for you to see what the computer is displaying. Yes, ordinary visible light is a form of radiation.

10 to 100 THz electromagnetic radiation. This is the infrared radiation given off by all parts of the laptop due to their temperature, through the everyday process of thermal emission.

5 GHz or 2.4 GHz electromagnetic radiation. These are the radio waves given off by the WIFI antenna in the laptop, which are used to connect to a wireless network.

2.4 GHz electromagnetic radiation. These are the radio waves given off by the Bluetooth antenna in the laptop, which are used to connect wirelessly to peripheral devices such as a cordless mouse.

Nuclear radiation including gamma rays. This is the nuclear radiation emitted through the natural radioactive decay of atomic isotopes in the computer’s materials.

This chart compares different sources of ionization radiation. A year of exposure from your computer CRT (this is the old large monitor) is 1/5 that of a dental X-ray, and 1/40 as much as a flight from LA to New York. The natural potassium in your body will give you a dose 400 times as much as that CRT. Today’s flat screens produce even less radiation.

Yes, but then most things will absorb EM radiation, especially things that contain water. An aquarium would work better than a cactus. A cup of coffee also works.

EM radiation travels in a straight line, just like light. The amount of radiation also follows the inverse square law that says doubling the distance from the emitting object will lower the radiation to 1/4. A simple way to reduce radiation from your computer is to move farther away from it. That is why a cell phone in your back pocket is not nearly as much of a concern as one held next to your brain, and why a laptop on the desk is much safer than one on your lap.

The other way to reduce radiation is to block it. Put something between you and the computer. If you hold a big piece of cardboard between you and the computer you will be exposed to less radiation. Holding a cactus between you and the computer has a similar effect.

Putting a cactus beside your computer has no effect since it does not block the radiation reaching you. If it’s not blocking the visible light from the screen it’s also not blocking EM radiation.

So a cactus works, provided you hide the screen with it. But then how do you see the screen? In practical terms a cactus does not reduce radiation from a computer.

This conclusion is based on what we know about this type of radiation, which is quite a bit. But if you still have some doubts, this video will show you a simple test; measuring EM radiation from a computer with and without a plant.

Cactus are not the only plant that is claimed to reduce radiation, but all of the comments above regarding cactus also apply to these other plants. They don’t work either.

I looked hard and long for a NASA study that looked at cactus and radiation from a computing device, and found nothing. One site did reference the NASA study that looked at a plants ability to absorb chemicals from the air, and somehow leaped from this to a discussion about plants that reduce radiation, but at least they did include the reference they were using. I suspect this is what other authors have also done. If you find such a study, please let me know in the comments below.

Since 1998, the International Commission on Non-Ionizing Radiation Protection (ICNIRP) has maintained that no evidence of adverse biological effects of RFR exist, other than tissue heating at exposures above prescribed thresholds (6).

Although Karipidis et al. (12) and Nilsson et al. (13) found no evidence of an increased incidence of gliomas in recent years in Australia and Sweden, respectively, Karipidis et al. (12) only reported on brain tumor data for ages 20–59 and Nilsson et al. (13) failed to include data for high grade glioma. In contrast, others have reported evidence that increases in specific types of brain tumors seen in laboratory studies are occurring in Britain and the US:The incidence of neuro-epithelial brain cancers has significantly increased in all children, adolescent, and young adult age groupings from birth to 24 years in the United States (14, 15).

Epidemiological evidence was subsequently reviewed and incorporated in a meta-analysis by Röösli et al. (19). They concluded that overall, epidemiological evidence does not suggest increased brain or salivary gland tumor risk with mobile phone (MP) use, although the authors admitted that some uncertainty remains regarding long latency periods (>15 years), rare brain tumor subtypes, and MP usage during childhood. Of concern is that these analyses included cohort studies with poor exposure classification (20).

In the interim, three large-scale toxicological (animal carcinogenicity) studies support the human evidence, as do modeling, cellular and DNA studies identifying vulnerable sub-groups of the population.

A study by Italy"s Ramazzini Institute has evaluated lifespan environmental exposure of rodents to RFR, as generated by 1.8 GHz GSM antennae of cell phone radio base stations. Although the exposures were 60 to 6,000 times lower than those in the NTP study, statistically significant increases in Schwannomas of the heart in male rodents exposed to the highest dose, and Schwann-cell hyperplasia in the heart in male and female rodents were observed (30). A non-statistically significant increase in malignant glial tumors in female rodents also was detected. These findings with far field exposure to RFR are consistent with and reinforce the results of the NTP study on near field exposure. Both reported an increase in the incidence of tumors of the brain and heart in RFR-exposed Sprague-Dawley rats, which are tumors of the same histological type as those observed in some epidemiological studies on cell phone users.

Further, in a 2015 animal carcinogenicity study, tumor promotion by exposure of mice to RFR at levels below exposure limits for humans was demonstrated (31). Co-carcinogenicity of RFR was also demonstrated by Soffritti and Giuliani (32) who examined both power-line frequency magnetic fields as well as 1.8 GHz modulated RFR. They found that exposure to Sinusoidal-50 Hz Magnetic Field (S-50 Hz MF) combined with acute exposure to gamma radiation or to chronic administration of formaldehyde in drinking water induced a significantly increased incidence of malignant tumors in male and female Sprague Dawley rats. In the same report, preliminary results indicate higher incidence of malignant Schwannoma of the heart after exposure to RFR in male rats. Given the ubiquity of many of these co-carcinogens, this provides further evidence to support the recommendation to reduce the public"s exposure to RFR to as low as is reasonably achievable.

Finally, a case series highlights potential cancer risk from cell phones carried close to the body. West et al. (33) reported four “extraordinary” multifocal breast cancers that arose directly under the antennae of the cell phones habitually carried within the bra, on the sternal side of the breast (the opposite of the norm). We note that case reports can point to major unrecognized hazards and avenues for further investigation, although they do not usually provide direct causal evidence.

Since 1998, the International Commission on Non-Ionizing Radiation Protection (ICNIRP) has maintained that no evidence of adverse biological effects of RFR exist, other than tissue heating at exposures above prescribed thresholds (6).

Although Karipidis et al. (12) and Nilsson et al. (13) found no evidence of an increased incidence of gliomas in recent years in Australia and Sweden, respectively, Karipidis et al. (12) only reported on brain tumor data for ages 20–59 and Nilsson et al. (13) failed to include data for high grade glioma. In contrast, others have reported evidence that increases in specific types of brain tumors seen in laboratory studies are occurring in Britain and the US:The incidence of neuro-epithelial brain cancers has significantly increased in all children, adolescent, and young adult age groupings from birth to 24 years in the United States (14, 15).

Epidemiological evidence was subsequently reviewed and incorporated in a meta-analysis by Röösli et al. (19). They concluded that overall, epidemiological evidence does not suggest increased brain or salivary gland tumor risk with mobile phone (MP) use, although the authors admitted that some uncertainty remains regarding long latency periods (>15 years), rare brain tumor subtypes, and MP usage during childhood. Of concern is that these analyses included cohort studies with poor exposure classification (20).

In the interim, three large-scale toxicological (animal carcinogenicity) studies support the human evidence, as do modeling, cellular and DNA studies identifying vulnerable sub-groups of the population.

A study by Italy"s Ramazzini Institute has evaluated lifespan environmental exposure of rodents to RFR, as generated by 1.8 GHz GSM antennae of cell phone radio base stations. Although the exposures were 60 to 6,000 times lower than those in the NTP study, statistically significant increases in Schwannomas of the heart in male rodents exposed to the highest dose, and Schwann-cell hyperplasia in the heart in male and female rodents were observed (30). A non-statistically significant increase in malignant glial tumors in female rodents also was detected. These findings with far field exposure to RFR are consistent with and reinforce the results of the NTP study on near field exposure. Both reported an increase in the incidence of tumors of the brain and heart in RFR-exposed Sprague-Dawley rats, which are tumors of the same histological type as those observed in some epidemiological studies on cell phone users.

Further, in a 2015 animal carcinogenicity study, tumor promotion by exposure of mice to RFR at levels below exposure limits for humans was demonstrated (31). Co-carcinogenicity of RFR was also demonstrated by Soffritti and Giuliani (32) who examined both power-line frequency magnetic fields as well as 1.8 GHz modulated RFR. They found that exposure to Sinusoidal-50 Hz Magnetic Field (S-50 Hz MF) combined with acute exposure to gamma radiation or to chronic administration of formaldehyde in drinking water induced a significantly increased incidence of malignant tumors in male and female Sprague Dawley rats. In the same report, preliminary results indicate higher incidence of malignant Schwannoma of the heart after exposure to RFR in male rats. Given the ubiquity of many of these co-carcinogens, this provides further evidence to support the recommendation to reduce the public"s exposure to RFR to as low as is reasonably achievable.

Finally, a case series highlights potential cancer risk from cell phones carried close to the body. West et al. (33) reported four “extraordinary” multifocal breast cancers that arose directly under the antennae of the cell phones habitually carried within the bra, on the sternal side of the breast (the opposite of the norm). We note that case reports can point to major unrecognized hazards and avenues for further investigation, although they do not usually provide direct causal evidence.

Contrary to public perception, nuclear power accidents have caused very few fatalities and the use of nuclear energy does not expose members of the public to significant radiation levels.

The socio-economic and psychological impacts of radiation fears in the aftermath of nuclear accidents have caused considerable harm amongst exposed and non-exposed populations.

Radiation plays a key role in modern life, be it the use of nuclear medicine, space exploration or electricity generation. Radiation constantly surrounds us as a result of naturally occurring radioactive elements in, for example, the soil, the air and the human body. As a result of many decades of research, the health impacts of radiation are very well-understood. In a 2016 report the United Nations Environment Programme (UNEP) noted:

“We know more about the sources and effects of exposure to [ionizing] radiation than to almost any other hazardous agent, and the scientific community is constantly updating and analysing its knowledge... The sources of radiation causing the greatest exposure of the general public are not necessarily those that attract the most attention."

At its most fundamental level, radioactivity is a question of energy, and the desire for unstable elements to become stable. By releasing radiation, elements go from one energy state to another which, eventually, will result in an element no longer being radioactive. There is a distinction to be drawn between radioactivity on the one hand, and radioactive elements on the other. Radioactivity is the process of releasing energy, either by particles (α, β) or high-energy photons (γ, X-ray).

Radiation particularly associated with nuclear medicine and the use of nuclear energy, along with X-rays, is "ionizing" radiation, which means that the radiation has sufficient energy to interact with matter, especially the human body, and produce ions, i.e. it can eject an electron from an atom. This interaction between ionizing radiation and living tissue can cause damage.

X-rays from a high-voltage discharge were discovered in 1895, and radioactivity from the decay of particular isotopes was discovered in 1896. Many scientists then undertook study of these, and especially their medical applications. This led to the identification of different kinds of radiation from the decay of atomic nuclei, and understanding of the nature of the atom. Neutrons were identified in 1932, and in 1939 atomic fission was discovered by irradiating uranium with neutrons. This led on to harnessing the energy released by fission.

Nuclear radiation arises from hundreds of different kinds of unstable atoms. The energy of each kind of radiation is measured in electron volts (eV). The principal kinds of ionizing radiation are:

The alpha particles’ large size, relatively speaking, and high energy are key to understanding their health impacts. When inside the human body, alpha particles can cause damage to the cells and to DNA as their size makes it more likely that it will interact with matter. If the dose is too high for repairs to be made satisfactorily, there is a potential increase in the risk of getting cancer later in life.

Beta (β) particles are electrons with high energy. Beta particles are 1/8000th the size of an alpha particle, which means that it can travel further before being stopped, but a sheet of aluminium foil is enough to stop beta particles. Equally, its small size results in its ionising power being considerably smaller than that of alpha particles (by about 10 times). This stems from the fact that the human body (and all matter more generally) is mainly made up of ‘empty’ space. The smaller the particle, the lower the risk of it colliding with parts of the atom which, in turn, lowers the risk of damage.

These are high-energy electromagnetic waves much the same as X-rays. They are emitted in many radioactive decays and may be very penetrating, so require more substantial shielding. The energy of gamma rays depends on the particular source. Gamma rays are the main hazard to people dealing with sealed radioactive materials used, for example, in industrial gauges and radiotherapy machines. Radiation dose badges are worn by workers in exposed situations to monitor exposure. All of us receive about 0.5-1 mSv per year of gamma radiation from rocks, and in some places, much more. Gamma activity in a substance (e.g. rock) can be measured with a scintillometer or Geiger counter.

X-rays are also electromagnetic waves and ionizing, virtually identical to gamma rays, but not nuclear in origin. They are produced in a vacuum tube where an electron beam from a cathode is fired at target material comprising an anode, so are produced on demand rather than by inexorable physical processes. (However the effect of this radiation does not depend on its origin but on its energy. X-rays are produced with a wide range of energy levels depending on their application.)

Cosmic radiation consists of very energetic particles, mostly high-energy protons, which bombard the Earth from outer space. They comprise about one-tenth of natural background exposure at sea level, and more at high altitudes.

Neutrons are uncharged particles mostly released by nuclear fission (the splitting of atoms in a nuclear reactor), and hence are seldom encountered outside the core of a nuclear reactor.* Thus they are not normally a problem outside nuclear plants. Fast neutrons can be very destructive to human tissue. Neutrons are the only type of radiation which can make other, non-radioactive materials, become radioactive.

In order to quantify how much radiation we are exposed to in our daily lives and to assess potential health impacts as a result, it is necessary to establish a unit of measurement. The basic unit of radiation dose absorbed in tissue is the gray (Gy), where one gray represents the deposition of one joule of energy per kilogram of tissue.

However, since neutrons and alpha particles cause more damage per gray than gamma or beta radiation, another unit, the sievert (Sv) is used in setting radiological protection standards. This weighted unit of measurement takes into account biological effects of different types of radiation and indicates the equivalent dose. One gray of beta or gamma radiation has one sievert of biological effect, one gray of alpha particles has 20 Sv effect and one gray of neutrons is equivalent to around 10 Sv (depending on their energy). Since the sievert is a relatively large value, dose to humans is normally measured in millisieverts (mSv), one-thousandth of a sievert.

Note that Sv and Gy measurements are accumulated over time, whereas damage (or effect) depends on the actual dose rate, e.g. mSv per day or year, Gy per day in radiotherapy.

The becquerel (Bq) is a unit or measure of actual radioactivity in material (as distinct from the radiation it emits, or the human dose from that), with reference to the number of nuclear disintegrations per second (1 Bq = 1 disintegration/sec). Quantities of radioactive material are commonly estimated by measuring the amount of intrinsic radioactivity in becquerels – one Bq of radioactive material is that amount which has an average of one disintegration per second, i.e. an activity of 1 Bq. This may be spread through a very large mass.

N.B. Though the intrinsic radioactivity is the same, the radiation dose received by someone handling a kilogram of high-grade uranium ore will be much greater than for the same exposure to a kilogram of separated uranium, since the ore contains a number of short-lived decay products, while the uranium has a very long half-life.

Since there is radioactivity in many foodstuffs, there has been a whimsical suggestion that the Banana Equivalent Dose from eating one banana be adopted for popular reference. This is about 0.0001 mSv.

Radiation can arise from human activities or from natural sources. Most radiation exposure is from natural sources. These include: radioactivity in rocks and soil of the Earth"s crust; radon, a radioactive gas given out by many volcanic rocks and uranium ore; and cosmic radiation. The human environment has always been radioactive and accounts for up to 85% of the annual human radiation dose.

Radiation arising from human activities typically accounts for up to 20% of the public"s exposure every year as global average. In the USA by 2006 it averaged about half of the total. This radiation is no different from natural radiation except that it can be controlled. X-rays and other medical procedures account for most exposure from this quarter. Less than 1% of exposure is due to the fallout from past testing of nuclear weapons or the generation of electricity in nuclear, as well as coal and geothermal, power plants.

Backscatter X-ray scanners being introduced for airport security will gives exposure of up to 5 microsieverts (μSv), compared with 5 μSv on a short flight and 30 μSv on a long intercontinental flight across the equator, or more at higher latitudes – by a factor of 2 or 3. Aircrew can receive up to about 5 mSv/yr from their hours in the air, while frequent flyers can score a similar incrementc. On average, nuclear power workers receive a lower annual radiation dose than flight crew, and frequent flyers in 250 hours would receive 1 mSv.

The maximum annual dose allowed for radiation workers is 20 mSv/yr, though in practice, doses are usually kept well below this level. In comparison, the average dose received by the public from nuclear power is 0.0002 mSv/yr, which is of the order of 10,000 times smaller than the total yearly dose received by the public from background radiation.

Naturally occurring background radiation is the main source of exposure for most people, and provides some perspective on radiation exposure from nuclear energy. Much of it comes from primordial radionuclides in the Earth’s crust, and materials from it. Potasssium-40, uranium-238 and thorium-232 with their decay products are the main source.

The average dose received by all of us from background radiation is around 2.4 mSv/yr, which can vary depending on the geology and altitude where people live – ranging between 1 and 10 mSv/yr, but can be more than 50 mSv/yr. The highest known level of background radiation affecting a substantial population is in Kerala and Madras states in India where some 140,000 people receive doses which average over 15 millisievert per year from gamma radiation, in addition to a similar dose from radon. Comparable levels occur in Brazil and Sudan, with average exposures up to about 40 mSv/yr to many people. (The highest level of natural background radiation recorded is on a Brazilian beach: 800 mSv/yr, but people don’t live there.)

Several places are known in Iran, India and Europe where natural background radiation gives an annual dose of more than 100 mSv to people and up to 260 mSv (at Ramsar in Iran, where some 200,000 people are exposed to more than 10 mSv/yr). Lifetime doses from natural radiation range up to several thousand millisievert. However, there is no evidence of increased cancers or other health problems arising from these high natural levels. People living in Colorado and Wyoming have twice the annual dose as those in Los Angeles, but have lower cancer rates. Misasa hot springs in western Honshu, a Japan Heritage site, attracts people due to having high levels of radium (up to 550 Bq/L), with health effects long claimed, and in a 1992 study the local residents’ cancer death rate was half the Japan average.* (Japan J.Cancer Res. 83,1-5, Jan 1992) A study on 3000 residents living in an area with 60 Bq/m3 radon (about ten times normal average) showed no health difference. Hot springs in China have levels reaching 3270 Bq/L radon-222 (Liaoning sanatorium), 2720 Bq/L (Tanghe hot spring) and 230 Bq/L (Puxzhe hot spring), though associated exposure from airborne radon are low**.

* The waters are promoted as boosting the body’s immunity and natural healing power, while helping to relieve bronchitis and diabetes symptoms, as well as beautifying the skin. Drinking the water is also said to have antioxidant effects. (These claims are not known to be endorsed by any public health authority.)

Radon is a naturally occurring radioactive gas resulting from the decay of uranium-238, which concentrates in enclosed spaces such as buildings and underground mines, particularly in early uranium mines where it sometimes became a significant hazard before the problem was understood and controlled by increased ventilation. Radon has decay products that are short-lived alpha emitters and deposit on surfaces in the respiratory tract during the passage of breathing air. At high radon levels, this can cause an increased risk of lung cancer, particularly for smokers. (Smoking itself has a very much greater lung cancer effect than radon.) People everywhere are typically exposed to around 0.2 mSv/yr, and often up to 3 mSv/yr, due to radon (mainly from inhalation in their homes) without apparent ill-effectd. Where deemed necessary, radon levels in buildings and mines can be controlled by ventilation, and measures can be taken in new constructions to prevent radon from entering buildings.

However, radon levels of up to 3700 Bq/m3 in some dwellings at Ramsar in Iran have no evident ill-effect. Here, a study (Mortazavi et al, 2005) showed that the highest lung cancer mortality rate was where radon levels were normal, and the lowest rate was where radon concentrations in dwellings were highest. The ICRP recommends keeping workplace radon levels below 300 Bq/m3, equivalent to about 10 mSv/yr. Above this, workers should be considered as occupationally exposed, and subject to the same monitoring as nuclear industry workers. The normal indoor radon concentration ranges from 10 to 100 Bq/m3, but may naturally reach 10,000 Bq/m3, according to UNEP.

Some of the ultraviolet (UV) radiation from the sun is considered ionizing radiation, and provides a starting point in considering its effects. Sunlight UV is important in producing vitamin D in humans, but too much exposure produces sunburn and, potentially, skin cancer. Skin tissue is damaged, and that damage to DNA may not be repaired properly, so that over time, cancer develops and may be fatal. Adaptation from repeated low exposure can decrease vulnerability. But exposure to sunlight is quite properly sought after in moderation, and not widely feared.

Our knowledge of the effects of shorter-wavelength ionizing radiation from atomic nuclei derives primarily from groups of people who have received high doses. The main difference from UV radiation is that beta, gamma and X-rays can penetrate the skin. The risk associated with large doses of this ionizing radiation is relatively well established. However, the effects, and any risks associated with doses under about 200 mSv, are less obvious because of the large underlying incidence of cancer caused by other factors. Radiation protection standards assume that any dose of radiation, no matter how small, involves a possible risk to human health. However, at low levels of exposure, the body"s natural mechanisms usually repair radiation damage to DNA in cells soon after it occurs (see following section on low-level radiation), whereas high-level irradiation overwhelms those repair mechanisms and is harmful. Dose rate is as important as overall dose.

The UN Scientific Commission on the Effects of Atomic Radiation (UNSCEAR) currently uses the term low doseto mean absorbed levels below 100 mGy but greater than 10 mGy, and the term very low dosefor any levels below 10 mGy. High absorbed dose is defined as more than about 1000 mGy. For beta and gamma radiation, these figures can be taken as mSv equivalent dose.

Former routine limit for nuclear industry employees, now maximum allowable for a single year in most countries (average to be 20 mSv/yr max). It is also the dose rate which arises from natural background levels in several places in Iran, India and Europe.

Lowest annual level at which increase in cancer risk is evident (UNSCEAR). Above this, the probability of cancer occurrence (rather than the severity) is assumed to increase with dose. No harm has been demonstrated below this dose.

Natural background level at Ramsar in Iran, with no identified health effects (Some exposures reach 700 mSv/yr). Maximum allowable annual dose in emergency situations in Japan (NRA).

Assumed to be likely to cause a fatal cancer many years later in about 5 of every 100 persons exposed to it (i.e. if the normal incidence of fatal cancer were 25%, this dose would increase it to 30%).

Threshold for causing (temporary) radiation sickness (Acute Radiation Syndrome) such as nausea and decreased white blood cell count, but not death. Above this, severity of illness increases with dose.

Would kill about half those receiving it as whole body dose within a month. (However, this is only twice a typical daily therapeutic dose applied to a very small area of the body over 4 to 6 weeks or so to kill malignant cells in cancer treatment.)

The main expert body on radiation effects is the UN Scientific Commission on the Effects of Atomic Radiation (UNSCEAR), set up in 1955 and reporting to the UN General Assembly. It involves scientists from over 20 countries and publishes its findings in major reports. The UNSCEAR 2006 report dealt broadly with the Effects of Ionizing Radiation. Another valuable report, titled Low-level Radiation and its Implications for Fukushima Recovery, was published in June 2012 by the American Nuclear Society.

In 2012 UNSCEAR reported to the UN General Assembly on radiation effects. It had been asked in 2007 "to clarify further the assessment of potential harm owing to chronic low-level exposures among large populations and also the attributability of health effects" to radiation exposure. It said that while some effects from high acute doses were clear, others including hereditary effects in human populations were not, and could not be attributed to exposure, and that this was especially true at low levels. "In general, increases in the incidence of health effects in populations cannot be attributed reliably to chronic exposure to radiation at levels that are typical of the global average background levels of radiation." Furthermore, multiplying very low doses by large numbers of individuals does not give a meaningful result regarding health effects. UNSCEAR also addressed uncertainties in risk estimation relating to cancer, particularly the extrapolations from high-dose to low-dose exposures and from acute to chronic and fractionated exposures. Earlier (1958) UNSCEAR data for leukaemia incidence among Hiroshima survivors suggested a threshold of about 400 mSv for harmful effects.

Epidemiological studies continue on the survivors of the atomic bombing of Hiroshima and Nagasaki, involving some 76,000 people exposed at levels ranging up to more than 5,000 mSv. These have shown that radiation is the likely cause of several hundred deaths from cancer, in addition to the normal incidence found in any populationf. From this data the International Commission on Radiological Protection (ICRP) and others estimate the fatal cancer risk as 5% per sievert exposure for a population of all ages – so one person in 100 exposed to 200 mSv could be expected to develop a fatal cancer some years later. In Western countries, about a quarter of people die from cancers, with smoking, dietary factors, genetic factors and strong sunlight being among the main causes. About 40% of people are expected to develop cancer during their lifetime even in the absence of radiation exposure beyond normal background levels. Radiation is a weak carcinogen, but undue exposure can certainly increase health risks.

About 60 years ago it was discovered that ionizing radiation could induce genetic mutations in fruit flies. Intensive study since then has shown that radiation can similarly induce mutations in plants and test animals. However there is no evidence of inherited genetic damage to humans from radiation, even as a result of the large doses received by atomic bomb survivors in Japan.

In a plant or animal cell the material (DNA) which carries genetic information necessary to cell development, maintenance and division is the critical target for radiation. Much of the damage to DNA is repairable, but in a small proportion of cells the DNA is permanently altered. This may result in death of the cell or development of a cancer, or in the case of cells forming gonad tissue, alterations which continue as genetic changes in subsequent generations. Most such mutational changes are deleterious; very few can be expected to result in improvements.

The relatively low levels of radiation allowed for members of the public and for workers in the nuclear industry are such that any increase in genetic effects due to nuclear power will be imperceptible and almost certainly non-existent. Radiation exposure levels are set so as to prevent tissue damage and minimize the risk of cancer. Experimental evidence indicates that cancers are more likely than inherited genetic damage.

Some 75,000 children born of parents who survived high radiation doses at Hiroshima and Nagasaki in 1945 have been the subject of intensive examination. This study confirms that no increase in genetic abnormalities in human populations is likely as a result of even quite high doses of radiation. Similarly, no genetic effects are evident as a result of the Chernobyl accident.

Life on Earth commenced and developed when the environment was certainly subject to several times as much radioactivity as it is now, so radiation is not a new phenomenon. If there is no dramatic increase in people"s general radiation exposure, there is no evidence that health or genetic effects from radiation could ever become significant.

The health effects of exposure both to radiation and to chemical cancer-inducing agents or toxins must be considered in relation to time. There is cause for concern not only about the effects on people presently living, but also about the cumulative effects that actions today might have over many generations.

Some radioactive materials decay to safe levels within days, weeks or a few years, while others maintain their radiotoxicity for a long time. While cancer-inducing and other toxins can also remain harmful for long periods, some (e.g. heavy metals such as mercury, cadmium and lead) maintain their toxicity forever. The essential task for those in government and industry is to prevent excessive amounts of such toxins harming people, now or in the future. Standards are set in the light of research on environmental pathways by which people might ultimately be affected.

The so-called linear no-threshold (LNT) model assumes that the demonstrated relationships between radiation dose and adverse effects at high levels of exposure also applies to low levels and provides the (deliberately conservative) basis of occupational health and other radiation protection standards.

The ICRP recommends that the LNT model should be assumed for the purpose of optimising radiation protection practices, but that it should not be used for estimating the health effects of exposures to small radiation doses received by large numbers of people over long periods of time. At low levels of exposure, the body"s natural mechanism repairs radiation and other damage to cells soon after it occurs, as with exposure to other external agents at low levels.

A November 2009 technical report from the Electric Power Research Institute in USA drew upon more than 200 peer-reviewed publications on effects of low-level radiation and concluded that the effects of low dose-rate radiation are different and that "the risks due to [those effects] may be over-estimated" by the linear hypothesis1. "From an epidemiological perspective, individual radiation doses of less than 100 mSv in a single exposure are too small to allow detection of any statistically significant excess cancers in the presence of naturally occurring cancers. The doses received by nuclear power plant workers fall into this category because exposure is accumulated over many years, with an average annual dose about 100 times less than 100 mSv". It quoted the US Nuclear Regulatory Commission that "since 1983, the US nuclear industry has monitored more than 100,000 radiation workers each year, and no workers have been exposed to more than 50 mSv in a year since 1989." A 2012 Massachusetts Institute of Technology study2 exposing mice to low-dose rate radiation for an extended period showed no signs of DNA damage, though a control group receiving the same dose acutely did show damage.

There is some in vitroevidence of a beneficial effect from low-level radiation (up to about 10 mSv/yr), a phenomenon which is called hormesis. This effect may arise as a result of an adaptive response by the body"s cells, in a similar way to physical exercise, where small and moderate amounts have a positive effect, whereas too much would have detrimental effects. In the case of carcinogens such as ionizing radiation, the beneficial effect would be seen both in a lower incidence of cancer and a resistance to the effects of higher doses. However, there is considerable uncertainty whether there is a hormetic effect in relation to radiation and, if such an effect actually exists, how large it would be. There is currently no conclusive in vivo evidence to support hormesis. Further research is under way and the debate around the actual health effects of low-dose radiation continues. Meanwhile standards for radiation exposure continue to be deliberately conservative.

In the USA, The Low-Dose Radiation Research Act of 2015 calls for an assessment of the current status of US and international low-dose radiation research. It also directs the National Academy of Sciences to “formulate overall scientific goals for the future of low-dose radiation research in the United States” and to develop a long-term research agenda to address those goals. The Act arises from a letter from a group of health physicists who pointed out that the limited understanding of low-dose health risks impairs the nation’s decision-making capabilities, whether in responding to radiological events involving large populations such as the 2011 Fukushima accident or in areas such as the rapid increase in radiation-based medical procedures, the cleanup of radioactive contamination from legacy sites and the expansion of civilian nuclear energy.

The main effects arising from the exposure to low-level radiation, especially following nuclear accidents, are not from the radiation itself, but are psychosocial in nature. Following the Chernobyl and Fukushima Daiichi accidents, there were sharp increases in a range of negative mental health impacts, including stress, anxiety, and depression. Substance abuse and increased rates of suicide have also been reported amongst certain populations. After the Chernobyl accident, pregnant women in some parts of Europe sought to terminate their pregnancies, despite there being no risk to the foetus as any radiation dose would be far below those required to cause any harm. The fear of radiation also affects government decisions which might have detrimental impacts. Following the Fukushima Daiichi accident, the Japanese government"s decision to evacuate vulnerable people in a hurried manner, and maintaining these evacuations, played a significant role in the deaths of more than 2200 people, whereas the radiation levels were too low to cause any fatalities. Furthermore, concerns about low doses of radiation from CT scans and X-rays may lead to suffering and deaths from avoided or delayed diagnosis. In addition, the therapeutic benefits of nuclear medicine greatly outweigh any harm that might come from the radiation exposure involved.

In most countries the current maximum permissible dose to radiation workers is 20 mSv per year averaged over five years, with a maximum of 50 mSv in any one year. This is over and above background exposure, and excludes medical exposure. The value originates from the International Commission on Radiological Protection (ICRP), and is coupled with the requirement to keep exposure as low as reasonably achievable (ALARA) – taking into account social and economic factors.

Radiation protection at uranium mining operations and in the rest of the nuclear fuel cycle is tightly regulated, and levels of exposure are monitored.

Shielding. Barriers of lead, concrete or water give good protection from high levels of penetrating radiation such as gamma rays. Intensely radioactive materials are therefore often stored or handled under water, or by remote control in rooms constructed of thick concrete or lined with lead.

Containment. Highly radioactive materials are confined and kept out of the workplace and environment. Nuclear reactors operate within closed systems with multiple barriers which keep the radioactive materials contained.

UNEP notes: “While the release of radon in underground uranium mines makes a substantial contribution to occupational exposure on the part of the nuclear industry, the annual average effective dose to a worker in the nuclear industry overall has decreased from 4.4 mSv in the 1970s to about 1 mSv today. However, the annual average effective dose to a coal miner is still about 2.4 mSv and for other miners about 3 mSv." The mining figures are probably for underground situations.

About 23 million workers worldwide are monitored for radiation exposure, and about 10 million of these are exposed to artificial sources, mostly in the medical sector where the annual dose averages 0.5 mSv.

Radiation protection standards are based on the conservative assumption that the risk is directly proportional to the dose, even at the lowest levels, though there is no actual evidence of harm at low levels, below about 100 mSv as short-term dose. However, the standard assumption – the linear no-threshold (LNT) model – discounts the contribution of any such thresholds and is recommended for practical radiation protection purposes only, such as setting allowable levels of radiation exposure of individuals.

LNT was first accepted by the International Commission on Radiological Protection (ICRP) in 1955, when scientific knowledge of radiation effects was less, and then in 1959 by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) as a philosophical basis for radiological protection at low doses, stating outright that “Linearity has been assumed primarily for purposes of simplicity, and there may or may not be a threshold dose”. (Above 100 mSv acute dose there is some scientific evidence for linearity in dose-effect.) From 1934 to 1955 a tolerance dose limit of 680 mSv/yr was recommended by the ICRP, and no evidence of harm from this – either cancer or genetic – had been documented.

The LNT hypothesis cannot properly be used for predicting the consequences of an actual exposure to low levels of radiation and it has no proper role in low-dose risk assessment. For example, LNT suggests that, if the dose is halved from a high level where effects have been observed, there will be half the effect, and so on. This would be very misleading if applied to a large group of people exposed to trivial levels of radiation and even at levels higher than trivial it could lead to inappropriate actions to avert the doses.

Much of the evidence which has led to today"s standards derives from the atomic bomb survivors in 1945, who were exposed to high doses incurred in a very short time. In setting occupational risk estimates, some allowance has been made for the body"s ability to repair damage from small e