Remembering the Harmful Effects of Ionizing Radiation

Remembering the Harmful Effects of Ionizing Radiation

Harmful Effects from Ionizing Radiation Known Since the Beginning

Scientists have known for a very long time now that exposure to ionizing radiation can have harmful effects in humans.  Awareness first manifested itself by radiation burns on the early experimenters who paid dearly for their work.  Fortunately, modern radioactive devices employ many well engineered safety measures to prevent this from ever happening when used properly.  Radiation induced injuries are relatively rare anymore which is a very good thing.  But it can also result in a lack of full appreciation for what damage can occur if ignored.  This article serves as a reminder of how harmful and painful radiation burns can be if we don’t take all safety precautions and procedures seriously.

The early pioneers investigating radioactivity in the late 1800’s and early 1900’s were not aware of the harmful effects until radiation burns began manifesting themselves.  Radiation burns were first noted in 1896, within just one month after Roentgen’s announcement of the discovery of what he called x-rays.  Within a year or two it became widely known that those working with x-ray devices had to take some precautions.

Early experimenters with natural radioactive sources were not immune from harmful effects and also received burns.  Most notable was Henri Becquerel who burned himself by carrying a sample of radium in his pocket.  The famous Marie Currie and her husband Pierre also received radiation burns on their skin from their work with radium and are believed to have also developed leukemia.  While Pierre was tragically killed relatively early and was largely spared long term suffering, Marie’s lifetime exposure resulted in a great deal of pain that she had to endure, especially to her hands.

By 1905 it was also known that excessive exposure to radiation could cause cancer.  Repeated large doses to the hands of workers frequently caused fatal skin cancer.  Many of the early medical radiologists either died of skin cancer or had to have their fingers or hands amputated. 

Immediate and Long-Term Effects of Ionizing Radiation

Very large doses of radiation can cause harmful health effects within just hours or weeks.  Such effects are called prompt effects because they appear relatively soon after the exposure.  The prompt effects result in radiation burns to the skin as well as radiation sickness, which can be fatal.

Other effects that manifest themselves years later are called delayed effects.  Cancer and genetic effects in offspring are examples of delayed effects

Radiation Burns

A radiation burn is not a temperature induced injury as the name would suggest; however, the cell damage appears in identical fashion; hence the name.  The severity of the cellular damage by ionizing radiation increases with dosage.  Lower one-time doses enable the body to heal itself over time.  As the dose levels increase, additional medical attention will be required to assist in recovery.  Eventually you reach a dose level where the damage becomes so great death becomes inevitable.  The chart below presents the prompt effects of one-time doses at increasing dose levels.

Effects to One-Shot Doses

600 rem

Radiation cell damage is equivalent to a first-degree heat burn or mild sunburn.  Within a few hours reddening occurs and often disappears over the next few days as the body does its healing work (assuming no further exposures occur). 

1000 rem

Results in serious tissue damage like a second-degree heat burn.  The initial inflammation is followed by swelling and tenderness.  Blisters will form within 1-3 weeks and break open leaving raw, painful wounds susceptible to infection.  Hands exposed to these dose levels become stiff and finger motion is often painful.  After several months the visible damage may heal but there will be some permanent damage to the surrounding tissue and make it more susceptible to injury in the future.

2000-3000 rem

An injury resembling a scalding or chemical burn is caused.  Medical treatment is immediately needed.  The injury may not heal without surgical removal of the exposed tissue.  Damage to blood vessels also occurs.  Future medical problems can be expected as this area will be more susceptible to pain, lower resistance to injury and reopening of the wound.

> 3000 rem

When more than 3000 rems are received at one time the tissue is completely killed and must be surgically removed. 

Prolonged Dose Effects

A radiation dose between 5000 to 10,000 rems received gradually over a period of several weeks will result in a chronic irritation, inflammation, dryness, and itching of the skin.  Once this condition has developed, it seldom heals completely.  Open sores may erupt and the regenerative and recuperative powers of the body are greatly reduced.  Malignant skin cancer occurs in a large percentage of these cases.

Severe Radiation Burn Cases

Back Pocket Carry

In 1979 a man found a 28-curie iridium radiography source that had accidently been left at the jobsite by a radiographer.  Not being a radiation worker or understanding what the material was he picked it up and put it in his back pocket for about 45 minutes. 

About an hour after the exposure he became nauseated, at 6 hours he noticed a burning feeling and a reddening of his right buttock.  The burning and reddening got worse and after 2 days went to a doctor.  The doctor not knowing what he was dealing with assumed the skin irritation was most likely caused by an insect bite.  But the burn got worse and worse until it became a large open sore.  After 17 days, the man was hospitalized and it took another three days of persistent questioning by doctors before they realized that he had a radiation burn.  By this time the man had an open wound about 4 inches in diameter and 1 inch deep.  Figure 1 shows the wound 31 days after the incident. 

It was later calculated that the radiation dose to the man’s right buttock exceeded 20,000 rems.  At a tissue depth of about 3 inches the dose still exceeded 1000 rems. 

To treat the burn, doctors surgically removed the dead tissue and a thick piece of skin from his thigh was sewn to close the wound, see Figure 2.  Six months later, the skin flap edge was not healing so at 10 months a second skin flap was sewn on.  At 19 months, the wound was still not healed, see figure 3 & 4, and further constructive surgery would be needed.  Two years after the accident, the man still walks with a limp and experiences pain where he was burned.

Figure 1
Figure 2
Figure 3
Figure 4

Front Pocket Carry

A similar incident occurred to a man in Argentina who placed a highly radioactive source in his front packet.  The front pocket location placed the source too close to his arteries that carried blood to his legs.  The arteries disintegrated because of the radiation damage and both legs had to be amputated.

Fatality Cases

Construction Watchman

The previous two cases were about those who survived, but there are also very sad fatalities that have been recorded.  In March of 1962 a construction watchman in Mexico was given a 5-curie Co-60 source for safekeeping by his employer.  Not understanding what he had, he took it home for safe-keeping where he, his wife, mother-in-law, son, and daughter were all exposed over a period of several months.  The employer retrieved the source in late July.  The damage was done, and one-by-one, members of his family began dying beginning in April and ending in Oct of that year.  Only the watchman survived because he was away so much of the time working.   

Scrap Yard in India

An incident in India more recently occurred whereby a university abandoned irradiator was taken to a metal scrap yard by individuals who had no idea what the device was.  The scrap yard placed the irradiator next to their worker bunk house.  A few days later several men became sick and at least one died. 

Conclusion

Fortunately, severe cases like those presented herein are rare.  Never-the-less, accidents and moments of forgetfulness do still occur.  Maintaining diligence is something Radiation Safety Officers and all those who work with or around radiation sources and devices cannot afford to ignore. 

The stealth properties of radiation make us vulnerable and so we each need to practice and follow procedures very carefully to avoid incidents of any kind.  It’s too easy to take safety for granted or to ignore when it comes to radiation exposure.  It’s much easier to think and act safely when climbing a ladder high above the ground.  It’s quite another mindset that is needed when you cannot see, smell, hear, taste or feel the impending danger.   Its stealthy nature all too often lure us into a false sense of security or a relaxed state of mind that typically exists at the beginning of any radiation incident.

While the incidents shown here are severe in nature, less severe exposures can still impact the quality of our lives, and we need to remember that too.  Sometimes we need a good dose of reality of what has already happened to others to fully appreciate the dangerous nature of the materials that are all about us in the industrial world.  Remembering the very real-life tragedies of others along with training and repeat training will hopefully keep your radiation safety program on guard at all times and in all places. 

Radiation safety should never be an after-thought, or just another item added to an already long list of duties.  It needs to be taken very, very seriously.  Let the tragic lessons of others be ever present on your mind as you strive to protect your fellow workers, friends and family.  Ionizing radiation is an excellent servant to mankind when contained and properly used and highly destructive and lethal when not carefully watched over and used properly. 

 

A Watered-Down Perspective to Radiation Measurement Units

A Watered-Down Perspective to Radiation Measurement Units

Relating Radiation Measurement Units to Water

If I were attempting to explain radiation measurement units to something even a child could understand, I would liken it to water which I feel really works well as a metaphor.  In many ways one can draw simple analogies using water to relate it to radiation. 

After completing my previous article Simplified Radiation Measurement for Radiation Safety Officers, I felt I had broken the subject down to its simplest form, but then I had this inspiration to relate water to radiation.  As ridiculous as it first sounds, in my mind, it worked surprisingly well.

In the previous article I had developed a chart that presents a great overview or map of the various radiation measurement units along with a more detailed explanation of each.  I have included the same chart below to use as a baseline reference for the water analogies I put forth. 

I hope this helps  those struggling to understand radiation measurement units more readily.  Here goes….

Physical Properties

Radiation is a physical property like water that requires different forms of measurement to describe it and to enable its use for our protection.  Water is measured by weight, volume, flow rate, temperature, pressure, acidity etc.  Similarly, radiation uses Roentgen, Rad, REM, Sieverts, etc.

Different Measurement Standards

Radiation measurements are described by different measurement systems, primarily US and International.  In the US we measure water volume in terms of gallons, whereas  internationally they use the  metric system and liters. So you’ll find two standards used interchangeably. 

Radiation Measurement Chart

Click to see larger image

Water Correlation to Radiation Measurement Units

Radiation measurements use different terms to describe the energy, rate, and accumulation in a very similar fashion to water. Here’s how the two relate:

Stationary Water Droplet

A droplet is a tiny measure of water.  If we forget the hydrogen/oxygen chemistry and science behind all its different forms and just call the droplet the base unit we could easily relate it to the Roentgen, which is a measure of energy in a volume of air.  

Streaming Water Droplets

If we take droplets dropping from an eye dropper, rain falling from the sky, or water flowing in a stream, it would represent different levels of our exposure to water droplets.  Water streaming from a hose represents one rate of exposure, rainfall another, and a raging stream another.  Likewise, radiation Exposure Rate is defined in units that enable us to better understand how much radiation we are receiving or are exposed to.  The US unit for exposure to radiation is described as Roentgens per hour (R/h).

Accumulated Water Droplets

As the water droplets accumulate you might receive enough to fill a glass of water, a small pond, or a lake.  The accumulated quantity referred to in radiation is called Dose.  The unit of dose in the US is called a RAD.

Accumulation of Water Droplet Energies

If water is hitting you with a greater force, the accumulated damage to you will be greater than if it were only trickling in for the same overall volume of water.  With radiation, there are different types of radiation, some more forceful than others so the dose type Equivalent Dose (rem) is used to adjust for the added energetic effects.

Water Droplet Absorption Properties

Water is absorbed differently by different materials.  Steel is largely impervious to water absorption, but a sponge will absorb many times its own weight.  Human absorption/effects/damage by radiation varies by the tissue type.  So to accurately describe the effective impact to each type of tissue a weighting factor is applied that results in an Effective Dose (Sv) measurement.

Methods of Measurement

Measurements of water and radiation fall into two categories, detectable and calculated.  It’s important to realize that most measurement units are not directly measurable and need to be calculated.  Here’s how the two relate.

Detectable

The easiest way to measure the quantity of water droplets is visually count drops as they individually come out of an eye dropper.  If we wanted to do this in a more automated fashion without using any of our human senses, we could use a microphone and an electronic counter that listened for each droplet splashing into a container of water and register the number of times droplets fell (counts).  Since radiation is not detectable to human senses, we use an electronic counter like a Geiger counter.  These rad meters are outfitted with a detector that collect counts every time it senses an interaction with radiation. 

Calculated

Some measurements are simply not possible using man-made sensors so they require a representative sample or an indirect measurement as a starting basis.  From that initial measurement, various factors and formulae are applied to derive various units of measurement.  A good example is determining the waterfall from a rainstorm or other periods of time.  A small water gauge in the form of a tube opened to the sky above collects a volume of water as it rains.  By measuring how many inches (or fractions of an inch) that is received, you can calculate the water collection in terms of inches/hour, inches/storm, millimeters/day, cc/month etc. 

If you wanted to know how much water was streaming inside a ditch, you could begin by measuring the flow rate directly using a flow type instrument.  Then by calculating the cross-sectional area of the ditch and multiplying it with the flow rate you arrive at a volumetric streaming rate of gallons/sec, acre-feet/min etc.  Radiation measurement units work in similar fashion whereby you can receive a rudimentary count measurement using a rad meter, that can then be applied to a series of factors and formulas to derive the desired measurement. 

Conclusion

I hope this brief article helps you to better understand the fundamentals of radiation measurement units.  To learn more be sure to also read these two articles:

 

Simplifying Radiation Measurement for Radiation Safety Officers

Simplifying Radiation Measurement for Radiation Safety Officers

Simplifying Radiation Measurement

Radiation measurement is a complex subject overall, but when working with nuclear gauges in industrial environments it can be simplified.  The purpose of this article to is give Radiation Safety Officers and Authorized Users who are new to the subject of Radiation and its measurement in industrial applications a simple overview to the extent possible.

There are many internet articles, scientific papers, and college level text books that cover radiation units and measurement very thoroughly, but sometimes it’s nice, even refreshing, to just get the basics so we can perform our jobs better.

If you’re one of those who don’t want to become physics professors, scientists, or experts on radiation measurement but prefer to just get a handle on the subject, this article is for you. 

Why are Radiation Measurement Units So Confusing?

To radiation neophytes, the subject of radiation measurement units can be a confusing topic.  All too often this topic is explained by taking you through complex set of physics, energy conversions, and mathematical formulas that only make this subject even more esoteric and confusing.

Resources

The confusion is not merely a function of physics and mathematics but is also be attributed to the evolving science and history of this subject.  Ever since Willhelm Roentgen first discovered X-rays in 1895 and the Roentgen unit was first established in 1902, the science has continued to evolve with refined definitions and added measurement units.  This refinement continues even today as we become more and more knowledgeable and continue our quest for absolute measurement certainty.

A second component of confusion is the duality of units with the US and the International community.  This is not any different than many other forms of measurement.  The International Commission of Radiation Units (ICRU) has established a set of standards to bring about world-wide uniformity, but here in the US, we cling on to past units and definitions as far as we can.  Overcoming past traditions, the huge number of perfectly functioning rad meters utilizing older measurement units that are still in use, and perhaps some of the American Revolutionary Independency all contribute to the US slow uptake to the newer measurement standards.

A third element adding to the confusion is the fact that most measurement units are not actually directly measurable.  What you say?  Yes, this means that many of the radiation measurement types are calculated values derived only after radiation detection events are collected by a rad meter.  For example, you cannot detect the REM or Sieverts of dose received by the lens of an eye; it has to be calculated based upon a number of factors once the radiation measurement by a rad meter like a Geiger counter has been made.

Added to this is a sub-level of added confusion whereby manufacturers of such instruments have purposefully ignored measurement technicalities in an effort to simplify radiation understanding for non-scientific users, extend the applications of a given instrument configuration, and indirectly sell more instruments.   To measurement purists, this is almost inexcusable, but tradition, economics, ignorance, and simplicity remain a formidable force yet to be overcome.

Comprehending all these factors and correctly applying all the physics and accompanying formulas are what Health Physicists are educated and trained to do.  But for the rest of us who do not have four or more years of study on this subject, there has to be a simpler way.  This article attempts to expose you (pun intended) to all the nuances in one simple elegant way.

 

Radiation Fundamentals

Here are a few fundamentals you need to understand before moving on.  You may wish to also read our blog  entitled: What is Radiation to gain a quick and better understanding as well. 

Radiation
Is energy emanating from unstable atoms as they seek to reach equilibrium of its charges
Ionizing Radiation
Radiation is divided into lower energy and higher energy classifications. The higher end of the energy spectrum causes ionization interaction with matter that can alter matter structure.
Ionizing Radiation Properties - Part 1
Ionizing radiation strips electrons from atoms it interacts with causing atomic level changes to materials. The extent of material change depends on the material type and the accumulative amount of energy the material interacted with.
Ionizing Radiation Properties - Part 2
Radiation interaction and potential damage to living tissue varies for different types of tissue. This is significant to Radiation Safety Officers because the regulations differentiate between a conservative whole body radiation dose and more specific doses to skin, body extremities (hands and feet), lens of the eye and our organs.
Ionizing Radiation Properties - 3
Ionization interaction with materials including air causes the original x-ray or gamma radiation energy level to lose its strength the further it travels away from its originating source.
Previous
Next

Understanding Measurement Types

Like any other physical property, it can be measured in multiple ways.  Radiation is similar and can be broken down by classification, category, method, and type.  The chart in Figure 1 below provides a convenient overview that shows how these radiation measurement units all fit in relationship to each other.   It’s quite a broad view, but I believe it gives a beginner a full perspective or map that places everything in their proper order and relationship.  This map in combination with the explanations that follow should provide you with an adequate foundation. 

Figure 1

The Three Basic Categories of Ionizing Radiation

Activity

Activity measures the energy being emitted from unstable atoms until they reach equilibrium like other non-radioactive elements.  The activity levels vary by the type of radionuclide and the amount of material present.  The activity level is an important measurement to assess the amount of radioactive material being sold or just found.  It’s also the key measurement for any contamination that might be found or is present on persons, objects or the surrounding area.  Finally, it’s used to see if the activity level requires immediate corrective action to ensure safety of all involved.  

Exposure

Over exposure to harmful rays is no good independent of whether you’re talking sun rays, x-rays, or gamma rays.  So knowing your exposure to these radiations anytime you enter into an environment with either known or unknown ionizing radiation is key to any radiation safety program.  Exposure type measurements determine the rate at which irradiation is impacting you.  The purpose of these measurements is to ensure work areas are below regulatory limits so accumulative doses are never exceeded.  When working in higher exposure rate areas, it also establishes how long one can safely remain in the radiation field before having to leave. 

Dose

The harmful effects of radiation exposure are pretty well known and are ultimately attributed to radiation dose values. Bombardment by higher energy, ionizing radiation over elapsed time causes fundamental changes to a materials structure.  When the material is living tissue, it can damage or even kill it if over-exposed.  Regulations are all keyed to annual dosage limits that have large built-in safety factors.   

Radiation dose is not uniform across all radiation types and materials.  Radiation dosage effects vary depending upon the radiation type and the material receiving the dose so they must be measured and noted separately. 

All doses are initially calculated by taking the exposure rate in air (which is all that radiation detectors can really measure), and multiplying it by the exposure time to arrive at a general-purpose dose value called Absorbed Dose.  In living tissue, not all radiations are equivalent; alpha producing radiations, for example, contribute 20 times more dose damage than gamma and x-rays.  So, multiplying your Absorbed Dose by 20 then gives you an appropriate Equivalent Dose.  Absorbed Dose effects on living tissue also varies by tissue type, so applying an appropriate dose factor for each type of tissue is required to arrive at what is known as the Effective Dose.

The Two Methods of Measuring Ionizing Radiation

Given all the measurement types and categories, it may be somewhat surprising that there really are only two measurement methods: Direct Measurement and Calculated.  It may also be surprising that the majority of measurement types all fall into the latter category.  I suspect most incorrectly believe that rad meter direct measurements tell the whole story and once you know how to read a rad meter, you’re good to go.  But fundamentally, that simply is not so, it’s just the beginning.  Here’s why….

Direct Measurement

Direct Measurement is the method whereby one acquires a radiation reading “DIRECTLY” from a radiation meter.  For simplicity sake, I am going to restrict the foregoing explanation to simple Geiger counters that are dominantly used throughout industry. 

All radiation meters function basically the same in that they electronically view the interaction of radiation within the detector medium and count the separate interactions.  There are several types of detector sensing materials each with their own set of  unique characteristics.   As such, not all radiation detectors are equal; each will have their sensitivities, advantages, and disadvantages.

Rad meters are inherently radiation unit agnostic, in that they natively can only report the number of interactions counted within their small detector volume per unit of time.  That’s all they see and know.  Thus natively, they can only report the raw counts per minute or raw counts per second.  They have no idea what type of radiation they are counting, the energy level, isotope, the  originating source activity, nor how far away or what direction the source is.  In other words, all the details you really want to measure cannot be inherently be obtained without additional knowledge.  Hence beyond raw counts, all radiation measurements need to be calculated.

Calculated

Having established that gross counting radiation meters fundamentally only acquire relative count values based upon their inherent interaction characteristics, we recognize that in order to obtain meaningful radiation measurements more intelligence needs to be factored in. 

The factors required will be different for each type of measurement type but always begin with the known detection characteristics of the specific detector used, the overall system detection efficiency, time of measurement, exposure level and time, and where possible the radiation isotope, energy, and distance to the source.

For Geiger counters that display readings beyond other than just counts, which most do, many of these factors have to be assumed.  The most common assumption is that the energy is close to Cs-137 gamma energy of 660 keV. 


Radiation Measurement Units Definitions

DETECTED

The raw counts acquired by the radiation meter either as a count rate or accumulated counts over a given period of time.

ACTIVITY

Refers to the amount of ionizing radiation released by a material. Whether it emits alpha or beta particles, gamma rays, x-rays, or neutrons, a quantity of radioactive material is expressed in terms of its radioactivity (or simply its activity). This represents how many atoms in the material decay in a given time period.

EXPOSURE RATE

Describes the amount of radiation traveling through the air. Many types of radiation monitors measure exposure. The units for exposure are the Roentgen (R, U.S. unit) and coulomb/kilogram (C/kg, international unit). The Roentgen was officially retired by the international community a long time ago but refuses to die in the US.

ABSORBED DOSE

Describes the amount of radiation absorbed by an object or person. The unit for absorbed dose is the rad (U.S. unit) or the gray (Gy, international unit). One gray is equal to 100 rads.

EQUIVALENT DOSE

A measure of the biological damage to living tissue as a result of radiation exposure. Also known as the " biological dose," the dose equivalent is calculated as the product of absorbed dose in tissue multiplied by a quality factor and then sometimes multiplied by other necessary modifying factors at the location of interest. The dose equivalent is expressed numerically in rems or sieverts (Sv)

EFFECTIVE DOSE

Describes the amount of radiation absorbed by person, adjusted to account for the type of radiation received and the effect on particular organs. The unit used for effective dose is rem (U.S. unit) or sievert (Sv, international unit).

Fractional Units of Measurement Often Necessary

Many of the base radiation measurement units described above represent very large amounts of radiation.  It therefore becomes necessary quite often to describe these in fractional terms or scientific formats as presented in the table below.

Fractional Units
Prefix Symbol Scientific Notation Fractional Value Examples
milli m 10e-3 one thousandth mR, mR/h, mSv
micro u 10e-6 one millionth uR, uR/h, uSv
nano n 10e-9 one billionth nR, nSv

Practical Radiation Measurement Values

Here are some measurement values to better understand the environment we live in and the dose impact to our bodies:

Backgrounds

Average background exposure rates:             10 uR/h     (0.1 uSv/h)

Daily dose (using exposure rates above):      240 urem  (2.4 uSv)

Yearly dose (using exposure rates above):     88 mrem   (0.88 mSv)

Flying

Transatlantic Airplane Flight:                            7 mrem     (0.07 mSv)

European Airline Crew Annual Limit:              2 rem        (20 mSv)

6 month flight on Int. Space Station:             7.5 rem     (75 mSv)

180 days transit to Mars:                                     13.3 rem   (133 mSv)

Medical

Chest X-ray:                                                              6 mrem      (0.06 mSv)

Panoramic Dental X-ray:                                     9 mrem     (.09 mSv)

Mammogram:                                                        70 mrem   (0.7 mSv)

Full Body CT Scan                                                  1 rem         (10 mSv)

Regulatory

Annual Public Dose Limit:                                100 mrem (1 mSv)

US Annual Rad Worker Occupational Dose Limit:      5 rem (50 mSv)

Body Effects

Radiation Effects when doses occur in short period:

  • Dose causing symptoms:     40 mrem  (0.4 Sv)
  • Letha Dose (50% death):      400 rem ( 4 Sv)
  • Certain death:                           800 rem    ( 8 Sv)

Conclusion

Believe it or not we have hardly scratched the surface when it comes to radiation measurement units.  The chart in Figure 1 should prove helpful anytime you need to cross reference units and standards, or better understand what type of dose is being measured or referenced.  If you’re interested in an even simpler explanation, see our other blog Watered-Down Perspective to Radiation Measurement Units.

Radiation measurement becomes very exciting when you have a Geiger meter in hand and have different radio-isotopes available for lab experimentation.  Watching the meter behavior to invisible rays and particles streaming from different isotopes, source activities, and varying distances can be a lot of fun and put you in touch with the invisible realm of radiation and its ability to be measured.  When measuring contamination, or calculating doses for given exposure rates you also get a better understanding of the different dose types and how they relate to the activities you counted with  your rad meter. 

Radiation Measurement Units make a lot of sense once you take just a little time to grasp it.  Like any other measurement units, there’s a lot of history and science behind them, but we need not understand all of that to benefit from the measurements.