"Life on earth has developed with an ever present background of radiation. It is not something new, invented by the wit of man: radiation has always been there."
Eric J Hall, Professor of Radiology,
College of Physicians and Surgeons,
Columbia University, New York
Read the instructions below and begin your investigation of the biological effects of radiation by identifying the different sources of radiation and their dosage effects. Answer the questions, according to your instructor's directions, to demonstrate your understanding of the biological effects of radiation.
You are about to begin an Envirohealth WebQuest. Instructions will appear in red and questions to be answered in black. Read the directions carefully before going to any sites. Look at the questions that are to be answered from the information at a site and use the questions as objectives to direct your reading and examination of any pages. Toggle back and forth between the specified sites and these pages. Your instructor will explain to you how they wish your data displayed for grading.Radiation takes many forms. The usual connotation of the word is something released by radioactive substances and associated with nuclear power plants and bombs. The truth of the matter is quite different, as this EnviroHealth WebQuest will make clear.
After you have learned about the biological effects of radiation you will prepare a 15 slide Power Point presentation that will be submitted to your instructor for evaluation. The presentation will be judged using a rubric. You may be asked to present the slides for your classmates during your regular instructional period.
Let's begin! Click the green heading above each section of questions below. It will take you to your destination.
1. Check the boxes next to the different forms of radiation that are found in our environment:
2. The strength of the radiation increases as the frequency of the wave forms increase.
3. When the biological effects of radiation are at issue, ultraviolet and ionizing radiation become the major causes of damage in living tissue.
4. Ionizing radiation is sort of a "double-edged sword." It can damage tissue at certain energy levels, but when controlled it can accomplish which of the following: (Check all that apply)
5. Background radiation is always present in our environment, and remains at the same level no matter where it is found.
6. According to the bar graph displaying the average doses from natural radiation sources, which of the following countries are among the four highest for dosage levels?
So, it's apparent that humans, as well as everything else on planet earth is being dosed with varying amounts of radiation from varying sources. The biological effects of this radiation has become a special concern as our use of radioactive materials has increased. The constant presence of radiation may be a surprise to you, but the fact is that science has only known about its existence for over a century. However, our understanding of its biological effects have come more slowly. We are trying to standardize the measurement of the dosages and the tissue effects it produces. The next part of our investigation will take you to the Lawrence Livermore National Laboratory site to assess how our exposure to radiation is currently measured.
Click in the green link below. When you arrive at the site, scroll down the page until you find the Tools for Assessment heading. Read the introductory information and then go to Biodosimetry where you will find the data to answer the questions below.
7. The goal of biodosimetry is to quantify how an exposure is distributed within an organism when the exposure is known or, when the exposure is not known, to "back in" to the dose from observation of the organism.
8. Biodosimetry involves establishing a dose-response relationship or following the dose as it is distributed throughout an organism.
9. Dose measurements cannot be made directly, such as by measuring the radiant energy emitted with a whole-body counter, but they must be done indirectly by measuring the dose's biological effects.
10. The biological parameters most often relied on to measure the effects of radiation are (Check all that apply)
11. Chromosome painting using fluorescence in situ hybridization (FISH) is a technique developed at Livermore for studying chromosomal changes in cells.
12. Accelerator mass spectrometry (AMS) is used to detect a variety of isotopes at very low concentrations. Its sensitivity is typically a million times greater than that of conventional mass spectrometry.
13. Biokinetic models are also used to project a worker's internal dose for up to 50 years after an intake.
14. Livermore's Atmospheric Release Advisory Capability (ARAC),
You now have learned how radiation is measured in biological systems. The FISH procedure described how to test for the effect of radiation on chromosomes and the type of damage that shows radiation as the culprit. We still have not seen the type of medical disorder that results from the radiation exposure. The next section of this WebQuest will address that issue.
However, there is something we must learn before we consider the effect of different doses of radiation on biological systems. It is important to attempt to understand the units used for measuring radiation and how they correlate to damage and death in these systems.
Unfortunately, this is not a simple thing to explain. The measurement of ionizing radiation takes many forms and the units that have emerged to describe dosage are difficult to put in everyday terms. The problem comes in attempting to use a source, or form, of energy that is familiar enough to be recognizably analogous to some equivalent amount of radiation.
For example, a calorie is the amount of heat necessary to raise the temperature of 1 ml. of water 1 degree Celsius. One can relate to heating water, so at least there is a connection between the measurement unit and what it represents.Let's press on despite these difficulties and see what can be understood. Several sites will be used to transmit the dosage unit information. After having visited, read and digested this data you will be asked to compose a Brief Constructed Response (BCR) explaining what you have learned. Instructions will be forthcoming for the writing assignment after the reading and thinking segment of this exercise.
Before going on to our WebQuest, read the information that follows and use it as a starting point. It begins the explanation of units used to measure radiation dosages.
The unit of dose is the gray (abbreviated Gy) which represents the absorption of an average of one joule (equivalent to 1 watt of electrical energy) of energy per kilogram of mass in the target material. This new unit has officially replaced the rad, an older unit (but still seen a lot in the radiation literature). One gray equals 100 rads. Absorbed Dose was originally measured for x-rays and gamma radiation but has been extended to describe protons and other heavy particle ionizing radiation. When used in predicting biological damage, a further distinction must be made as to the "quality" of the radiation.The biological effects of heavy particle ionizing radiation are approximately proportional to what is called Absorbed Dose (or simply dose). This is measured with instruments which detect the average energy deposited inside a small test volume.
Although the Absorbed Dose of some radiation may be measured, another level of consideration must be made before the biological effects of this radiation can be predicted. The problem is that although two different types of heavy charged particle may deposit the same average energy in a test sample, living cells and tissues do not necessarily respond in the same way to these two radiations. This distinction is made via the concept of Relative Biological Effectiveness (RBE) which is a measure of how damaging a given type of particle is when compared to an equivalent dose of x-rays. The Quality Factor of a given type of radiation is determined in the following way: A group of RBE measurements are made using a variety of cells and/or tissue (these experiments aren't cheap to perform and the number that are done is driven by the overall interest in the radiation being studied). Basically, the RBE is determined by comparing the damage of the radiation to the cells/tissue of interest to that with an equal dose of gammas or xrays. Once the RBE data are in hand, a commitee of radiation experts meets and considers all the available data and then assigns a Quality Factor to the radiation. This may seem a bit unusual to those used to hard formulas or well-defined procedures.
For example, the RBE of alpha particles has been determined (by committee) to be 20 (apparently not very dependent on the energy of these particles). This means that 1 Gy of alphas is equivalent to 20 Gy of gammas/xrays. Another way to say this is to use a new unit, the sievert (Sv) which measures Dose Equivalent (the old unit is the rem; 1 sievert = 100 rem). Thus 1 Gy absorbed dose of alpha particles is 20 Sv dose equivalent. The sievert is the unit used in NASA's radiation limits for humans in Low Earth Orbit.
So, do you have a grasp of the units that measure radiation? Basically, there are grays, rads, Absorbed Dose, Relative Biological Dose, Quality Factor and a sievert. Not exactly transparent, is it? There must be some other explanation for these units that's more understandable, or how can one write a BCR explaining them?
Click in the green link below. When you arrive at the site, read the information and use the outline below to organize the data for the Biological Effects of Ionizing Radiation BCR . Write the essay to a layman. Take the technical aspects of quantitative dosages and translate them into qualitative explanations of dosage and effect. This is not a simple assignment, so take your time and discuss your ideas with a partner before you begin writing.
Outline Each listed phrase should rate a concise sentence , or two, in the BCR
-Types and effects of non-ionizing radiation- Types and effects of ionizing radiation
- The three ways of measuring ionizing radiation
a. rad doseb. Radiation Biological Effectiveness (RBE) and rem dose
c. Per capita dose
-Sources of radiation exposure
-Biological effects by dosage level
-Summarize
It's your turn now. The title of the BCR is Biological Effects of Ionizing Radiation. Use the scrolling window below, or open a word processing document and put your BCR there. Your instructor will specify which process to use. Good luck!
Click in the green link below. When you arrive at the site scroll down the page until you find the Biological Effects of Radiation heading. Read the information and answer the questions below. Keep in mind your final assignment for this activity. You will prepare a 15-slide Power Point presentation on the biological affects of radiation that will be submitted to your instructor for evaluation.
Biological Effects of Radiation
15. The biological effects of radiation on living cells may result in three outcomes:
16. The associations between radiation exposure and the development of cancer are mostly based on populations that have been exposed to low level radiation.
17. Cancers caused by radiation are difficult to detect because they have long latency periods, as do other cancers, and are difficult to discriminate from other environmentally induced cancers.
18. The effect of being exposed to radiation varies according to dose. Which two of the following outcomes reflect cellular responses to high dose radiation?
19. The effect of being exposed to radiation varies according to dose. Which two of the following outcomes reflect cellular responses to low dose radiation?
20. Determining what a lethal dose of radiation would be is extremely difficult and is affected by which of the following? (Check all that apply)
21. Genetic effects and the development of cancer are the primary health concerns attributed to radiation exposure.
22. Genetic effects are five times more likely to occur after radiation exposure rather than cancer.
23. Although radiation-induced genetic effects have been observed in laboratory animals (given very high doses of radiation), no evidence of genetic effects has been observed among the children born to atomic bomb survivors from Hiroshima and Nagasaki.
We've reached the end of The Biological Effects of Radiation WebQuest. You have taken quite a path to arrive here. It certainly appears that the effects of radiation on biological systems is both difficult to measure and to predict. It seems obvious to people, in a general sense, that radiation causes damage, but the nature and degree of the damage are not easy to determine. There appears to be much here that is hard to nail down.
However, the knowledge you have acquired must now be put to use to construct a Power Point Presentation. Resources were supplied for you and can be used to create your slides. There are more links provided at the bottom of this Web page.
Your instructor will provide you with directions and particulars as you begin your task. Consider your audience and provide them with the most accurate and meaningful information that is available.
Web BibliographyIonizing RadiationAssessing Exposure to Radiation
Fact Sheet on the Biological Effects of Radiation
Biological Effects of Radiation
Radiation and Long Term Space Flight
The Biological Effects of Nuclear Radiation