Category: Background Radiation

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27 Mar 2024
Airplane flight crew character design. Pilot and stewardess flat vector illustration
Background Radiation, Health Effects, Ionizing Radiation, Radiation Safety Versant Physics 0 comment

Flight Crews and Radiation Exposure

Flight crews are among the occupational groups most exposed to ionizing radiation, with an average annual effective dose surpassing that of other radiation-exposed workers in the United States, excluding astronauts.1 This elevated exposure is primarily due to the high levels of cosmic radiation encountered at flight altitudes, which can pose significant health risks to pilots and cabin crew members.2 In this blog post, we’ll explore the nature of cosmic radiation, its potential health effects, current exposure levels for aircrews, as well as the guidelines and regulations in place to ensure their safety.

What Is Cosmic Ionizing Radiation?

As we’ve touched on in a previous blog, cosmic ionizing radiation–or simply cosmic radiation–originates from beyond Earth’s atmosphere. Additionally, it consists of two main components: galactic cosmic radiation (GCR) and solar particle events (SPEs).3,4

Galactic Cosmic Radiation

GCR is a constant background radiation that permeates interstellar space, originating from distant stars and galaxies. It is composed primarily of high-energy protons (85%) and alpha particles (14%). There is also a small fraction of heavier nuclei (1%) ranging from lithium to iron and beyond. These particles span a wide energy range, and as a result some reach extremely high energies capable of penetrating deep into the Earth’s atmosphere and passing through aircraft shielding.5

Solar Particle Events (Solar Flares)

Solar particle events, on the other hand, are sporadic bursts of intense radiation associated with solar flares and coronal mass ejections. During an SPE, the Sun ejects a large number of high-energy protons and other particles that can reach Earth within hours to days. While less frequent than GCR, SPEs can dramatically increase radiation exposure for flight crews, particularly those on polar routes where the Earth’s magnetic field provides less protection.6,7

At higher altitudes, such as those typically encountered during air travel, the Earth’s atmosphere provides less shielding against cosmic radiation, resulting in increased exposure for flight crews and passengers.

Several studies that have investigated the difference in cosmic ray levels at various altitudes versus ground level found that the dose rate of cosmic radiation at a cruising altitude of 30,000 feet was approximately 10 times higher than at sea level.

The specific increase in cosmic ray exposure at higher altitudes is influenced by several factors, including the solar cycle (solar maximum vs. solar minimum), geomagnetic field strength, and also the path of the flight (polar routes are exposed to higher levels of cosmic rays). For example, during periods of high solar activity (solar maximum), the increased solar wind can actually shield the Earth from some cosmic rays, slightly reducing the exposure at high altitudes. Conversely, during a solar minimum, the cosmic ray intensity can be higher.

Estimates of the number of hours that have to be flown in order to receive an effective dose of 1 mSv at 30,000 feet are 510 hours at a latitude of 30o South and 1,330 hours at the equator.8

Health Effects and Uncertainties

The health risks associated with radiation exposure are generally well-documented. Prolonged exposure to high levels of radiation can increase the risk of cancer, cataracts, as well as other adverse health effects.  However, quantifying the specific risks associated with the chronic low-dose radiation experienced by flight crews remains a challenge.

The World Health Organization’s International Agency for Research on Cancer (IARC) acknowledges that ionizing radiation causes cancer in humans and is also associated with reproductive problems. However, when it comes to cosmic ionizing radiation, several uncertainties remain:

  1. Cancer Risk: Most radiation health studies have focused on groups exposed to much higher doses from different types of radiation (such as atomic bomb survivors or patients receiving radiation therapy).9 Due to this, the specific link between cosmic ionizing radiation and cancer risk is not yet fully understood.
  2. Reproductive Health: Miscarriages and birth defects related to cosmic radiation exposure are still not definitively established.10

Despite the limitations of current research, several studies have suggested that flight crews may have a higher incidence of certain cancers compared to the general population. These include breast cancer, melanoma, as well as non-melanoma skin cancers.11,12 However, the causal link between cosmic radiation exposure and these increased risks has not been definitively established. Other factors, such as lifestyle and genetic predisposition, may also play a role.13

Exposure Levels for Flight Crews

Recent dose and risk assessments by a wide variety of investigators have demonstrated the need to dedicate further attempts to quantify potential radiation exposure.14 The National Council on Radiation Protection and Measurements (NCRP) reports an average annual effective dose of 3.07 mSv for flight crews; most of this exposure comes from natural radiation:

  • Estimates of annual aircrew cosmic radiation exposure range from 0.2 to 5 millisieverts (mSv) per year depending on factors such as flight routes, altitude, and solar activity.
  • Solar particle events occur less frequently, but during events, exposure levels can increase substantially and potentially lead to higher doses over short periods.

Guidelines and Regulations

While there are no official dose limits specifically for aircrew in the United States, national and international guidelines provide context:

  • International Commission on Radiological Protection (ICRP): Recognizes aircrew as radiation-exposed workers. They also recommend an effective dose limit of 20 mSv per year averaged over 5 years (totaling 100 mSv in 5 years) for radiation workers. However, for the general public, the recommended limit is 1 mSv per year.15
  • Pregnant Aircrew: The ICRP recommends a dose limit of 1 mSv throughout pregnancy.16

Current regulations aim to limit radiation exposure for flight crews, but there is room for improvement. The International Commission on Radiological Protection (ICRP) sets guidelines for radiation protection and also includes dose limits for occupational exposure. However, these guidelines may not adequately address the unique challenges faced by flight crews. To improve current radiation safety regulations for aircrews, a multi-faceted approach is necessary. This should include:

Improved Monitoring and Data Collection

Implementing advanced radiation monitoring systems on aircraft in addition to encouraging the use of personal dosimeters by flight crews can provide more accurate and comprehensive data on exposure levels17. This information can help refine risk assessments as well as guide the development of more effective protection strategies.

Aircraft Shielding and Design

Continued research into advanced shielding materials in addition to aircraft design modifications can help reduce the radiation dose received by flight crews and passengers18. This may also involve the use of novel composite materials or the incorporation of additional shielding in critical areas of the aircraft.

Route Optimization and Flight Planning

By carefully planning flight routes and altitudes, airlines can minimize exposure to cosmic radiation, particularly during solar particle events19. This may also involve rerouting flights to lower latitudes or reducing flight time at higher altitudes when necessary.

Education and Awareness Programs

Providing flight crews with comprehensive information about the risks of cosmic radiation exposure in addition to the importance of proper protection measures can empower them to make informed decisions about their health and safety20. This should include training on the use of personal protective equipment, such as dosimeters, as well as guidelines for managing exposure during pregnancy.

Regulatory Harmonization and Enforcement

Strengthening international collaboration to harmonize radiation protection standards for flight crews in addition to ensuring consistent implementation and enforcement of these standards across the aviation industry can help create a safer working environment for all aircrews2121.

Conclusion

Although no regulations officially set dose limits, radiation exposure is still a concern to be evaluated for airplane flight crews due to their occupational exposure to cosmic radiation. While the specific health risks associated with this chronic low-dose exposure remain uncertain, continued efforts are essential ensure a safe working environment. By implementing measures such as personal dosimetry devices, increased monitoring, staff training, and encouraging airplane manufacturers to consider shielding and design modifications, airlines can better protect their flight crews. Ensuring a safer career for every radiation worker will require time, dedication, and collaboration. However, the benefits for the health and safety of all industries, including aircrews, make it a worthwhile endeavor.

Versant Physics is a full-service medical physics and radiation safety consulting company based in Kalamazoo, MI. Contact us for all of your regulatory, radiation safety, and personnel dosimetry needs.

Sources

  1. Friedberg, W., & Copeland, K. (2003). What aircrews should know about their occupational exposure to ionizing radiation. Oklahoma City, OK: Civil Aerospace Medical Institute, Federal Aviation Administration. ↩︎
  2. United Nations Scientific Committee on the Effects of Atomic Radiation. (2008). Sources and effects of ionizing radiation: UNSCEAR 2008 report to the General Assembly, with scientific annexes. New York: United Nations. ↩︎
  3. Validation of modelling the radiation exposure due to solar particle events at aircraft altitudes. Radiation Protection Dosimetry, Volume 131, Issue 1, August 2008, Pages 51–58. https://doi.org/10.1093/rpd/ncn238 ↩︎
  4. Wilson, J. W., Townsend, L. W., Schimmerling, W., Khandelwal, G. S., Khan, F., Nealy, J. E.,  & Norbury, J. W. (1991). Transport methods and interactions for space radiations. NASA Reference Publication, 1257 ↩︎
  5. O’Sullivan, D. Exposure to galactic cosmic radiation and solar energetic particles. Radiat Prot Dosimetry. 2007;125(1-4):407-11. https://pubmed.ncbi.nlm.nih.gov/17846031/ ↩︎
  6. Turner, R. E. (2007). Solar particle events from a risk management perspective. Radiation Protection Dosimetry, 127(1-4), 534-538. ↩︎
  7. Lantos, P., & Fuller, N. (2003). History of the solar particle event radiation doses on-board aeroplanes using a semi-empirical model and Concorde measurements. Radiation Protection Dosimetry, 104(3), 199-210. ↩︎
  8. Cosmic Radiation Exposure for Casual Flyers and Aircrew, https://www.arpansa.gov.au/understanding-radiation/radiation-sources/more-radiation-sources/flying-and-health ↩︎
  9. National Research Council. (2006). Health risks from exposure to low levels of ionizing radiation: BEIR VII phase 2 (Vol. 7). National Academies Press. ↩︎
  10. CDC – Aircrew Safety and Health – Cosmic Ionizing Radiation – NIOSH Workplace Safety & Health Topics. Centers for Disease Control and Prevention. Published 2019. https://www.cdc.gov/niosh/topics/aircrew/cosmicionizingradiation.html ↩︎
  11. Pukkala, E., Aspholm, R., Auvinen, A., Eliasch, H., Gundestrup, M., Haldorsen, T., & Tveten, U. (2003). Cancer incidence among 10,211 airline pilots: a Nordic study. Aviation, Space, and Environmental Medicine, 74(7), 699-706. ↩︎
  12. Rafnsson, V., Hrafnkelsson, J., & Tulinius, H. (2000). Incidence of cancer among commercial airline pilots. Occupational and Environmental Medicine, 57(3), 175-179. ↩︎
  13. Hammer, G. P., Blettner, M., & Zeeb, H. (2009). Epidemiological studies of cancer in aircrew. Radiation Protection Dosimetry, 136(4), 232-239. ↩︎
  14. Olumuyiwa A. Occupational Radiation Exposures in Aviation: Air Traffic Safety Systems Considerations. International Journal of Aviation, Aeronautics, and Aerospace. Published online 2020. doi:https://doi.org/10.15394/ijaaa.2020.1476 ↩︎
  15. International Commission on Radiological Protection. (2007). The 2007 recommendations of the International Commission on Radiological Protection. Annals of the ICRP, 37(2-4), 1-332. ↩︎
  16. International Commission on Radiological Protection. (2000). Pregnancy and medical radiation. Annals of the ICRP, 30(1), iii-viii, 1-43. ↩︎
  17. Bartlett, D. T. (2004). Radiation protection aspects of the cosmic radiation exposure of aircraft crew. Radiation Protection Dosimetry, 109(4), 349-355. ↩︎
  18. Wilson, J. W., Miller, J., Konradi, A., & Cucinotta, F. A. (1997). Shielding strategies for human space exploration. NASA Conference Publication, 3360. ↩︎
  19. Copeland, K. (2014). Cosmic radiation and commercial air travel. Radiation Protection Dosimetry, 162(3), 351-357. ↩︎
  20. International Civil Aviation Organization. (2012). Manual of Civil Aviation Medicine. https://www.icao.int/publications/Documents/8984_cons_en.pdf ↩︎
  21. International Atomic Energy Agency: Cosmic radiation exposure of aircrew and space crew. https://www.iaea.org/sites/default/files/20/11/rasa-cosmic.pdf ↩︎
05 Jan 2022
Consumer Products, Health Effects, Non-ionizing radiation, NORM Versant Physics 0 comment

Top 3 Consumer Products that Contain Radioactive Materials

Radioactive materials are present in our natural environment and in man-made products we use every day. Such consumer products are defined as “a device or manufactured item into which radionuclides have deliberately been incorporated or produced by activation, or which generates ionizing radiation, and which can be sold or made available to members of the public without special surveillance or regulatory control after sale.”

Many devices that use WiFi or Bluetooth technology or connect to cell phone towers emit radio waves, also known as electromagnetic radiation (EMF).

This may concern consumers who are worried about the negative health effects associated with “radioactive materials” and “radiation.” However, in most cases, these materials we interact with are safe and pose no danger to our health.

Below we guide you through three common consumer products the average person uses or engages with regularly, discuss how the radioactive materials they contain work, and determine the health risk they pose to you and your family.

Cell Phones

Cell phones have become an integral part of daily modern life. We depend on them for communication, connection, and as a source of entertainment. However, their permanent presence and increased usage have raised concerns over the years that cell phones can cause negative health effects to humans, including brain tumors and hearing loss.

pile of cell phones

Do cell phones emit radiation?

Cell phones are not consumer products that contain radioactive materials. However, they communicate by transmitting EMF, a type of non-ionizing radiation at the low-energy end of the electromagnetic spectrum in the 100kHz to 300GHz frequency range.

RFs are widely used in communication technologies such as cell phones, Wi-Fi, radio, and TV. They are also found in MRI equipment, from natural sources like outer space, and in the microwave oven sitting on your kitchen counter.

Are there health risks?

Decades of research on RF radiation have concluded that exposure to this frequency has minimal health effects. Due to their frequency, RF radiation can be absorbed by the human body. In large amounts, this can produce heat, which has the potential to cause burns or tissue damage.

Numerous short-term studies have taken place on the link between cancer rates and cell phone usage. Small, individual studies have found slight associations between cell phones and cancer of the salivary glands, as well as a possible increase in the risk of gliomas. In 2011, the International Agency for Research on Cancer evaluated these studies and concluded that there is limited or inadequate evidence of carcinogenicity. Longer-term studies may need to be conducted to accurately determine the level of cancer risk associated with cell phones.

Those uncomfortable with incurring any level of risk can take steps to limit their cell phone usage by purchasing a hands-free headset or utilizing the speakerphone function when making calls.

Smoke Detectors

Most smoke detectors in the United States are ionization smoke alarms, which contain a small amount of the man-made radioactive element called americium-241.

how smoke alarms work

Why is radioactive material present?

Ionization smoke alarms are more responsive to flaming fires. The radioactive material present in the smoke alarm rests between two electrically charged plates which ionize the air and causes a current between them. Smoke entering the chamber disrupts the flow of ions, reducing the current and thereby activating the alarm.

Are there health risks?

Smoke detectors pose little to no health risk to human beings. The amount of americium-241 present is minimal, wrapped in gold foil, and shielded by the plastic case and stainless steel. These protective measures prevent easy tampering rather than limiting radiation exposure. However, there is no risk of significant exposure as long as these sources are contained in the detector housing.

Granite Countertops

Like many natural materials found on Earth, granite, a type of durable stone used in construction and home décor, contains small amounts of radioactivity.

Granite is a consumer product that contains a small amount of natural radioactive material.

Does granite emit radiation?

Trace elements of uranium, thorium, and radium can show up in slabs of granite. When these elements are present, they decay into radon. According to the EPA, radon released from granite materials can be released over the lifetime of its use but is typically diluted by ventilation.

Are there health risks?

It is extremely unlikely that the radiation emitted from granite countertops in your home would increase radiation doses above normal background levels. The radon released from granite is a significantly lower concern when compared with radon which originates in the soil and can build up inside the home. This type of radon is the second leading cause of lung cancer in the United States and should be tested for on a regular basis.

Conclusion: Are Consumer Products That Contain Radioactive Materials or Emit Radition Unsafe?

It is true that some common consumer products contain trace amounts of naturally occurring radioactive materials or emit non-ionizing radiation. However, this does not mean they are dangerous or pose a health risk to humans. In fact, in products like ionizing smoke detectors, the presence of radioactive material is crucial for keeping humans safe.

Further Reading:

Radiation Safety for Consumer Products, Specific Safety Guide No. SSG-36

10 Sep 2021
Ore mining
NORM Versant Physics 0 comment

What is Naturally Occurring Radioactive Material?

Naturally Occurring Radioactive Materials (NORM) are just that: materials of natural origin that contain radioactive materials. NORM is found in rock formations, soil, and sand that come out of the Earth’s crust and mantle. This includes elements like radium, uranium, thorium, and potassium, as well as their decay products radium and radon. Many of these elements show up in concentrated areas, like uranium ore bodies, which are then mined for human use.

The Environmental Protection Agency (EPA) defines NORM as “materials that contain any of the primordial radionuclides or radioactive elements… that are undisturbed as a result of human activity.”

Cosmogenic NORM, or cosmic radiation produced by cosmic rays interacting with the Earth’s atmosphere, affects frequent flyers and those who live at higher altitudes.

Learn more about background radiation in our blog post here.

According to the IAEA, the activity concentrations of the radionuclides found in these places are generally low and not considered to be a risk to human health and safety.

Technologically Enhanced Naturally Occurring Radioactive Materials (TENORM)

Human activities such as extraction and processing can expose, disturb, or concentrate NORM. Bringing natural resources from below the ground—in a solid, liquid, gas, or sludge form—and introducing it to the surface brings up the materials that contain radionuclides. When something like this happens, NORM is classified as Technologically Enhanced Naturally Occurring Radioactive Materials or TENORM.

pile of raw coal

It can also concentrate it in some cases. For example, coal-ash, a byproduct of burning coal, contains a higher concentration of NORM than it did when it was mined from the ground. As ash only accounts for about 10% of the weight of unburned coal, the resulting NORM is 10x that of the plant’s coal fuel.

Industries that generate TENORM include:

  • Mining (hard rock/metal, rare earths, uranium, copper, alumina)
  • Energy (oil and gas, coal, fracking)
  • Water treatment (drinking water, wastewater, fish hatcheries)
  • Consumer products (fertilizer, cigarettes, granite countertops, bricks/building materials)
  • Recycling

Region and geology are major factors in the amount of radioactivity and materials such processes can introduce into the environment. When these materials are exposed or concentrated because of industrial processes, humans are exposed to the ionizing radiation they give off. This can result in potential health risks including cancer.

Regulating NORM/TENORM

Radiation levels from NORM are not considered hazardous in the United States.  Therefore, it is not regulated at the federal level.

TENORM is also not regulated by the federal government or the Nuclear Regulatory Commission. It is up to individual states if and how they choose to regulate generation and disposal. Currently, there are 37 Agreement States which regulate NORM within their borders. There is little consistency among different industries and countries regarding NORM. Contact your state’s radiation management branch for more information.

How to Minimize TENORM Exposure

From a radiation safety perspective, some precautions can be taken by professionals and the public to ensure minimal exposure to these radioactive materials. The level of exercised caution ultimately depends on the type of TENORM present. In general, TENORM should be handled only by individuals familiar with radiation safety practices and hazardous industrial substances. Other steps to take include:

  • Implementing a radiation safety program
  • Using appropriate shielding, HEPA filters, and personal protective equipment as necessary
  • Minimizing time spent around TENORM
  • Avoiding eating or drinking around TENORM
  • Minimizing activities like cutting or grinding which can generate dust containing TENORM
  • Properly disposing of TENORM-contaminated waste
15 Jun 2021
Background Radiation, Health Effects Versant Physics 0 comment

The Truth About Background Radiation

Background radiation is all around us, and always has been. That idea can be a frightening concept at face value, but the truth is background radiation is natural, normal, and expected.

Most natural background sources of radiation fall into one of three categories:

Cosmic Radiation

Think of this as steady waves of external radiation being sent from the sun and stars in space to Earth. This type of radiation occurs naturally and introduces extremely low levels of radiation to the average person. The amount (or dose) of cosmic radiation one receives can depend on weather and atmospheric conditions, the Earth’s magnetic field, and differences in elevation. For example, people who live at higher altitudes like Denver, Colorado are exposed to slightly more cosmic radiation than people who live in lower altitudes, such as New Orleans, Louisiana or Miami, Florida. Furthermore, the farther north or south one is from the equator results in a higher dose of cosmic radiation due to the way the Earth’s magnetic field deflects cosmic radiation toward the North and South poles.

silver airplane flying above orange clouds

Air travel can also expose individuals to low levels of cosmic radiation. The received dose is similarly dependent on altitude, latitude, and the duration of the flight. A coast-to-coast flight in the United States would expose an individual to approximately 3.5 mrem. For comparison, a typical medical procedure involving radiation, such as a chest X-ray, exposes an individual to 10 mrem, and the average American receives a total radiation dose of 540 mrem each year.

In general, a person’s average dose from cosmic radiation in the United States is small, making up only 6% of their total annual dose.

Terrestrial Radiation

Terrestrial radiation is the portion of natural background radiation that is emitted by naturally occurring radioactive materials on earth, and it is responsible for approximately 3% of the average person’s annual received dose. The physical earth, including soil and sedimentary and igneous rock, contains common elements like uranium, thorium, and radium. These naturally occurring radioactive materials, which have existed as part of the earth’s crust since the earth was formed, are released into the water, vegetation, and the atmosphere as they breakdown at different rates. People are largely exposed to the resulting emitted radiation through their skin.

Radon:

diagram of radon gas infiltrating a house

Perhaps the most significant form of terrestrial radiation is that which is inhaled. When the naturally occurring radioactive element uranium (found in the earth’s crust, underwater caves, and seawater) decays it can change into a scentless, invisible gas called radon. All the air we breathe contains trace amounts of radon, and it is responsible for the largest portion of background radiation dose that the average American receives in a year. Outdoors, this radioactive gas disperses rapidly and does not pose any health risk to human beings. A build-up of radon gas indoors, however, can potentially increase the risk of lung cancer over time, which is why it is important to test homes and workplaces for radon on a regular basis. Smoking, especially near or inside the home, can amplify the risk of cancer when coupled with radon exposure.

The average person can expect to receive 42% of their annual radiation dose from radon.

Internal Radiation

Background radiation can also be received through ingestion. Some common foods contain small amounts of radioactive elements that do not pose a radiation risk to the person ingesting them. The most common example is the banana. This delicious, nutritious fruit contains naturally high levels of potassium which helps muscles contract, keeps your heartbeat regular, and offsets the harmful effects of sodium on blood pressure. A tiny portion of potassium is also naturally radioactive. A single banana emits 0.01 mrem, which is received internally by the person eating it. According to the EPA, a person would have to eat 100 bananas to receive the same amount of radiation exposure naturally received each day from the environment. (It should be noted that this naturally occurring radiation is not the same thing as food irradiation, which is a process used by humans to kill bacteria, molds, and pests to prevent foodborne illnesses and spoilage.) Overall, the levels of natural radionuclides found in our food and water are low and considered safe for human consumption by regulatory bodies.

Most surprisingly for some is the fact that other humans are also a source of exposure to one another. From birth, people have internal radiation in the form of radioactive potassium-40, lead-210, and carbon-14. These elements reside in our blood and bones. As previously noted, humans also ingest traces of naturally occurring radioactive material found in our food and water. When our bodies metabolize the non-radioactive and radioactive forms of potassium and other elements, they then contain small amounts of radiation which can act as exposures to others.

Man-Made Radiation Exposure

A more familiar source of radiation exposure to many is man-made radiation, such as procedures using X-Rays and radiation therapy to treat cancer. According to the Health Physics Society, approximately 42% of annual dose comes from man-made radiation. This percentage includes medical procedures, household products like smoke detectors, and small quantities of normal discharges from nuclear and coal power plants.

Learn more about the health effects of man-made ionizing radiation in our blog post here.

Conclusion

Natural background radiation has always been a part of life on earth, and it always will be. It is important to understand that this is not something to be feared. Low levels of ionizing radiation from naturally occurring sources such as space, the ground beneath our feet, and even some of the food we eat are not dangerous and do not pose a direct health risk to ourselves or our loved ones.

For more information, visit the Health Physics Society webpage, epa.gov, or the International Atomic Energy Agency.

Note: Visit our regulatory page to learn how Versant Physics’ board-certified Internal Dose Specialists, Medical Physicists, and Health Physicists, can assist with your radiation safety program needs.

Additional Sources:

https://www.nrc.gov/about-nrc/radiation/around-us/sources/nat-bg-sources.html

https://www.cdc.gov/nceh/radiation/air_travel.html

NCRP Report 160

NCRP Report 184

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