Janet M. Gutierrez is manager of the Radiation Janet M. Gutierrez is manager of the Radiation Safety Program at The University of Texas Health Safety Program at The University of Texas Health Science Center at Houston. She is a Certified Science Center at Houston. She is a Certified Health Physicist (CHP) and a Registered Radiation Health Physicist (CHP) and a Registered Radiation Protection Technologist (RRPT). In August 2011, Protection Technologist (RRPT). In August 2011, she received a Doctorate in Public Health from the she received a Doctorate in Public Health from the The University of Texas at Houston School of Public The University of Texas at Houston School of Public Health (UT SPH), and in 2005, she received a M.S. Health (UT SPH), and in 2005, she received a M.S. in Environmental Sciences / Industrial Hygiene from in Environmental Sciences / Industrial Hygiene from UT SPH as well. In 1998, Janet received a B.S. in UT SPH as well. In 1998, Janet received a B.S. in Radiological Health Engineering from Texas A&M Radiological Health Engineering from Texas A&M University in College Station, TX.University in College Station, TX.
Speaker BiographySpeaker Biography
Travis Halphen is a Safety Specialist in the Travis Halphen is a Safety Specialist in the Radiation Safety Program at The University of Radiation Safety Program at The University of Texas Health Science Center at Houston (UTHSC-Texas Health Science Center at Houston (UTHSC-H). He is currently seeking his MPH in H). He is currently seeking his MPH in Environmental Health and Occupational Safety from Environmental Health and Occupational Safety from University of Texas School of Public Health (UT University of Texas School of Public Health (UT SPH) and on May 2006 he received a Bachelors in SPH) and on May 2006 he received a Bachelors in Medical Physics from Louisiana State University. Medical Physics from Louisiana State University. He was Assistant Radiation Safety Officer and Laser He was Assistant Radiation Safety Officer and Laser Safety Officer at Kansas State University from 2006 Safety Officer at Kansas State University from 2006 to 2008 before he ended up at his current position at to 2008 before he ended up at his current position at UTHSC-HUTHSC-H
Ionizing vs. Non-ionizing Ionizing vs. Non-ionizing RadiationRadiation Electromagnetic SpectrumElectromagnetic Spectrum
Radiation is energy transmitted by particles Radiation is energy transmitted by particles or electromagnetic wavesor electromagnetic waves
Radiation can be ionizing or non-ionizingRadiation can be ionizing or non-ionizing
Basic ConceptsBasic Concepts Radiation: energyRadiation: energy Ionizing vs. Non-Ionizing: enough energy to Ionizing vs. Non-Ionizing: enough energy to
eject orbital electrons eject orbital electrons Radioactivity: excess nuclear energyRadioactivity: excess nuclear energy
RadioactivityRadioactivity
Radioactivity is the natural property of certain Radioactivity is the natural property of certain nuclides to spontaneously emit energy, in the nuclides to spontaneously emit energy, in the form of ionizing radiation, in an attempt to form of ionizing radiation, in an attempt to become more stable.become more stable.
Basic ConceptsBasic Concepts
Radionuclide Radionuclide NuclideNuclide Isotopes have the same Z and a different A; Isotopes have the same Z and a different A;
1010C,C,1111C, C, 1212C, C, 1313C, C, 1414C C
Isobars have the same A and a different Z; Isobars have the same A and a different Z; 1414N, N, 1414O; O; 1515N, N, 1515CC
Isomers have the same A and the same Z; Isomers have the same A and the same Z; 99m99mTc, Tc, 9999Tc Tc
Isotones have the same N and a different A; Isotones have the same N and a different A; 1414O,O,1313N,N,1212C,C,1111B,B,1010Be,Be,88Li Li
Basic ConceptsBasic Concepts Types of radiation:Types of radiation:
Neutron: particulate, no Neutron: particulate, no chargecharge
Alpha (Alpha (αα))
Needs at least 7.5 MeV energy to penetrate Needs at least 7.5 MeV energy to penetrate nominal protective layer of skin (7 mg/cmnominal protective layer of skin (7 mg/cm22)) Most Most αα less than this energy, so can not penetrate less than this energy, so can not penetrate
skinskin Range in airRange in air Range (cm) = 0.56E for E< 4 MeVRange (cm) = 0.56E for E< 4 MeV Range (cm) = 1.24E-2.62 for E> 4 MeVRange (cm) = 1.24E-2.62 for E> 4 MeV
Beta (Beta (ββ))
Need at least 70 keV energy for beta to penetrate Need at least 70 keV energy for beta to penetrate nominal protective layer of skinnominal protective layer of skin
ββaveave = 1/3 = 1/3 ββmaxmax
Range in airRange in air Range is ~ 12 ft / MeVRange is ~ 12 ft / MeV
Bremsstrahlung for high energy beta & high Z Bremsstrahlung for high energy beta & high Z material material Ex. P-32 and LeadEx. P-32 and Lead
Gamma (Gamma (γγ))
PhotoelectricPhotoelectric Compton ScatteringCompton Scattering Pair ProductionPair Production
PhotonPhoton X-rayX-ray Gamma rayGamma ray
Neutrons (n)Neutrons (n)
Often expressed in n / cmOften expressed in n / cm22sec (flux)sec (flux) Thermal neutrons = 0.025 eVThermal neutrons = 0.025 eV Slow neutrons = 1 eV – 10 eVSlow neutrons = 1 eV – 10 eV Fast neutrons = 1 MeV – 20 MeVFast neutrons = 1 MeV – 20 MeV Relativistic neutrons = > 20 MeVRelativistic neutrons = > 20 MeV
U-238 & U-235U-238 & U-235
Shielding ExamplesShielding Examples
Shielding for Multiple Types of Shielding for Multiple Types of RadiationRadiation High Energy BetasHigh Energy Betas BremstrahlungBremstrahlung NeutronsNeutrons GammasGammas
UnitsUnits
Activity: Curie (Ci) 3.7 x 10Activity: Curie (Ci) 3.7 x 101010 disintegrations per disintegrations per secondsecond SI: Becquerel 1 dpsSI: Becquerel 1 dps
Absorbed Dose: Rad (Roentgen Absorbed Dose)Absorbed Dose: Rad (Roentgen Absorbed Dose) SI: Gray, 1Gy = 100 RadSI: Gray, 1Gy = 100 Rad
Risk: Rem (Roentgen Equivalent Man), Rad x QFRisk: Rem (Roentgen Equivalent Man), Rad x QF SI: Sievert, 1 Sv = 100 RemSI: Sievert, 1 Sv = 100 Rem
Quality FactorsQuality Factors
Type of Radiation QX-rays and Gamma-rays 1Beta particles 1Neutrons of unknown energy 10High-energy protons 10Alpha particles 20
Half-life - the amount of time required for 1/2 of the original sample to decay
The half-life is constant for each radionuclide and varies due to the nuclear structure.
Half-lifeHalf-life
Radioactive DecayRadioactive Decay
Is the process by which the amount of Is the process by which the amount of activity of a radionuclide diminishes activity of a radionuclide diminishes with time.with time.
Examples:Examples:
Radioactive Decay FormulaRadioactive Decay Formula
VariablesVariables A A Activity at time t Activity at time t AA00 Original Activity Original Activity
t t Time Time Decay ConstantDecay ConstantTT1/21/2 Half Life Half Life
Radioactive Decay: A = ARadioactive Decay: A = Aooee--λλt t
A =A = λλNN λλ = 0.693 / T = 0.693 / T1/21/2
Inverse Square LawInverse Square Law
Shielding I = IShielding I = IooBeBe--t t
22
21
12
d
dII
Annual US Average Dose from Background Radiation was
Total US average dose equivalent = 360 mrem/year
Total exposure Man-made sources
Radon
Internal 11%
Cosmic 8% Terrestrial 6%
Man-Made 18%
55.0%
Medical X-Rays
NuclearMedicine 4%
ConsumerProducts 3%
Other 1%
11%
Annual US Average Dose from Annual US Average Dose from Background Radiation Now is 625 Background Radiation Now is 625 mremmrem
National Average Dose is US is 625 mrem, with medical being the largest type of increase.
Ionization of Gas – Radiation Ionization of Gas – Radiation DetectorDetector A = recombinationA = recombination B = ionizationB = ionization C = proportionalC = proportional D = limited D = limited
proportionalproportional E = Geiger MullerE = Geiger Muller F = continuous F = continuous
dischargedischarge
MonitoringMonitoring
InstrumentationInstrumentation Gas filledGas filled Solid scintillatorSolid scintillator Liquid scintillationLiquid scintillation
MonitoringMonitoring
DosimetersDosimeters Film badges: beta, gamma, x-rayFilm badges: beta, gamma, x-ray
Permanent recordPermanent record Subject to fadingSubject to fading
Thermoluminescent dosimeter (TLD): beta, Thermoluminescent dosimeter (TLD): beta, gamma, x-raygamma, x-ray No permanent recordNo permanent record Can be used for long term useCan be used for long term use
Pocket ion chamber: gamma, x-rayPocket ion chamber: gamma, x-ray Immediate readoutImmediate readout Shock sensitiveShock sensitive
Linear, Linear Quadratic, ThresholdLinear, Linear Quadratic, Threshold
Stochastic and Stochastic and Non-stochastic EffectsNon-stochastic Effects
Stochastic effectsStochastic effects Dose increases the probability of the effectDose increases the probability of the effect No thresholdNo threshold Any exposure has some chance of causing the effectAny exposure has some chance of causing the effect Cancer Cancer
Non-stochastic effectsNon-stochastic effects Dose increases the severity of the effectDose increases the severity of the effect ThresholdThreshold Effects result from collective injury of many cellsEffects result from collective injury of many cells Reddening, cataract, skin burnReddening, cataract, skin burn
Biological EffectsBiological Effects
Assumptions Used for Basis of Radiation Assumptions Used for Basis of Radiation Protection StandardsProtection Standards No Threshold Dose, Risk with Given Dose No Threshold Dose, Risk with Given Dose
Increases With Increasing Dose Received, Acute Increases With Increasing Dose Received, Acute vs. Chronic Exposures Not Considered, i.e. vs. Chronic Exposures Not Considered, i.e. RepairRepair
Biological EffectsBiological Effects
Prenatal ExposuresPrenatal Exposures Law of Bergonie & Tribondeau (1906):Law of Bergonie & Tribondeau (1906):
Cells Tend to be Radiosensitive if They Have Three Cells Tend to be Radiosensitive if They Have Three Properties:Properties:
A) Have a High Division RateA) Have a High Division Rate B) Have a Long Dividing FutureB) Have a Long Dividing Future C) Are of an Unspecialized TypeC) Are of an Unspecialized Type
Most and Least Radiosensitive Most and Least Radiosensitive CellsCellsLow SensitivityLow Sensitivity Mature red blood cellsMature red blood cells
Very High SensitivityVery High Sensitivity Primitive blood cellsPrimitive blood cells
Intestinal epitheliumIntestinal epithelium
SpermatogoniaSpermatogonia
Ovarian follicular cellsOvarian follicular cells
LymphocytesLymphocytes
Acute Radiation SyndromesAcute Radiation Syndromes Occurs if specific portions of body are exposed Occurs if specific portions of body are exposed Not likely unless major organs involvedNot likely unless major organs involved 3 ARS syndromes:3 ARS syndromes:
Hematopoietic (blood/bone marrow)Hematopoietic (blood/bone marrow) 100-700 rad100-700 rad Treatment: transfusions, antibiotics, bone marrowTreatment: transfusions, antibiotics, bone marrow transplanttransplant
Gastrointestinal (intestinal lining)Gastrointestinal (intestinal lining) 500-2500 rad500-2500 rad Death likely if dose >1000 radDeath likely if dose >1000 rad Treatment: make individual comfortableTreatment: make individual comfortable
Central Nervous System (brain)Central Nervous System (brain) 2000 rad or more2000 rad or more Death likely within daysDeath likely within days Treatment: make individual comfortableTreatment: make individual comfortable
LDLD5050 for Humans for Humans
Dose of radiation that would result in 50% Dose of radiation that would result in 50% mortality of in the exposed population within mortality of in the exposed population within 30 days of exposure with NO medical 30 days of exposure with NO medical treatmenttreatment
LDLD5050 for Humans is 300 to 500 rad for Humans is 300 to 500 rad
Risks of Radiation ExposureRisks of Radiation Exposure
Low level (< 10,000 mrem) radiationLow level (< 10,000 mrem) radiation Only health effect: cancer inductionOnly health effect: cancer induction
Average occupational dose to research and Average occupational dose to research and lab medicine personnel: <10 mrem/yrlab medicine personnel: <10 mrem/yr Amount is comparable to:Amount is comparable to:
6 cigarettes/yr6 cigarettes/yr Driving 1,000 milesDriving 1,000 miles Living in a stone or brick home for 2 monthsLiving in a stone or brick home for 2 months
Dose to a particular organ:Dose to a particular organ:ه Internal + External Internal + External ≤≤ 50 rem 50 rem
Exposure LimitsExposure Limits
Committed Effective Dose Equivalent (CEDE)Committed Effective Dose Equivalent (CEDE) Dose to a particular organ or organs with weighting Dose to a particular organ or organs with weighting
factor:factor:ه Internal + External Internal + External ≤≤ 5 rem 5 rem
Deep Dose Equivalent (DDE)Deep Dose Equivalent (DDE) Dose at a depth of Dose at a depth of ≥≥ 1 cm: 1 cm:
ه Internal + External Internal + External ≤≤ 5 rem (Eye 5 rem (Eye ≤≤ 15 rem) 15 rem)
Shallow Dose Equivalent (SDE)Shallow Dose Equivalent (SDE) Dose to skin or extremity:Dose to skin or extremity:
ه External External ≤≤ 50 rem 50 rem
Exposure LimitsExposure Limits
Total Effective Dose Equivalent (TEDE)Total Effective Dose Equivalent (TEDE) Sum of dose from external and internal, including Sum of dose from external and internal, including
weighting:weighting:ه Internal + External Internal + External ≤≤ 5 rem 5 rem
Effective Dose EquivalentEffective Dose Equivalent Dose to organ or organs over one year periodDose to organ or organs over one year period
Total Organ Dose EquivalentTotal Organ Dose Equivalent Dose to organ from both internal and external:Dose to organ from both internal and external:
ه Internal + External Internal + External ≤≤ 50 rem 50 rem Exposure to Fetus (Declared Pregnancy) .5 Exposure to Fetus (Declared Pregnancy) .5
Rem/9 monthsRem/9 months
Other Useful InformationOther Useful Information
6CE rule6CE rule
Efficiency = c/d, usually in percentEfficiency = c/d, usually in percent
Effective half life:Effective half life:
Stay time = dose / dose rateStay time = dose / dose rate
REMEMBER UNITS!REMEMBER UNITS!
br
breff TT
TTT
http://www.icrp.org Internal advisory body for ionizing radiationInternal advisory body for ionizing radiation ICRP Publications (examples)ICRP Publications (examples)
ICRP 84, Pregnancy and medical radiation ICRP 85, Interventional radiology ICRP 86, Accidents in radiotherapy ICRP 87, CT dose management ICRP 93, Digital radiology
National Council on Radiation ProtectionNational Council on Radiation Protectionand Measurementsand Measurements
http://www.ncrponline.orgformulate and widely disseminate information, guidance and formulate and widely disseminate information, guidance and recommendations on radiation protection and measurements which recommendations on radiation protection and measurements which represent the consensus of leading scientific thinking represent the consensus of leading scientific thinking
publication of NCRP materials can make an important contribution publication of NCRP materials can make an important contribution to the public interest.to the public interest.
NCRP 148 – Radiation Protection in Veterinary MedicineNCRP 148 – Radiation Protection in Veterinary Medicine
NCRP 138 – Management of Terrorist Events Involving Radioactive Material*NCRP 138 – Management of Terrorist Events Involving Radioactive Material*
Radiation Practice Radiation Practice ProblemsProblemsIonizing RadiationIonizing Radiation
Radiation Practice ProblemsRadiation Practice Problems
1. Iodine-131 has a radiological half life of 8 1. Iodine-131 has a radiological half life of 8 days. If a source originally contained 25 mCi days. If a source originally contained 25 mCi how much remains after 18 days?how much remains after 18 days?
Radiation Practice ProblemsRadiation Practice Problems
2. Two measurements are taken on an 2. Two measurements are taken on an unknown radiation source. The first was 1.3 unknown radiation source. The first was 1.3 mCi, and the second, taken 15 minutes later, mCi, and the second, taken 15 minutes later, was 0.05 mCi. What is the half life of this was 0.05 mCi. What is the half life of this material?material?
Radiation Practice ProblemsRadiation Practice Problems
3. What is the exposure rate from a 15 Ci 3. What is the exposure rate from a 15 Ci Cs-137 source at a distance of 1 foot? (Cs-Cs-137 source at a distance of 1 foot? (Cs-137 gamma energy 0.662 MeV) How about 137 gamma energy 0.662 MeV) How about 10 feet?10 feet?
Radiation Practice ProblemsRadiation Practice Problems
4. How long can a worker stay 10 feet away 4. How long can a worker stay 10 feet away from a 15 Ci Cs-137 source without from a 15 Ci Cs-137 source without exceeding an administratively established exceeding an administratively established quarterly dose limit of 1250 mrem?quarterly dose limit of 1250 mrem?
Non-ionizing RadiationNon-ionizing Radiation
What is Radiation?What is Radiation?
Radiation is energy transmitted by particles Radiation is energy transmitted by particles or electromagnetic wavesor electromagnetic waves
Radiation can be ionizing or non-ionizingRadiation can be ionizing or non-ionizing
DefinitionDefinition
Non-Ionizing RadiationNon-Ionizing Radiation = Radiation that does not = Radiation that does not cause ionizationcause ionization
In their normal state, atoms are electrically In their normal state, atoms are electrically neutral (no net charge)neutral (no net charge)
# protons = # electrons# protons = # electrons
An atom that has gained or lost electrons is An atom that has gained or lost electrons is called an called an ionion
Positive and negative charges cancel
The Ionization ProcessThe Ionization Process
1.1. An in-coming photon interacts with an An in-coming photon interacts with an orbital electronorbital electron
2.2. The electron is ejected from the atom, and The electron is ejected from the atom, and the atom gains a net positive charge. the atom gains a net positive charge.
Incident photon
Ejected electron
Non-Ionizing RadiationNon-Ionizing Radiation
Non-ionizing radiation is electromagnetic in Non-ionizing radiation is electromagnetic in nature:nature: This means it has characteristics of both waves This means it has characteristics of both waves
and particlesand particles However, non-ionizing radiation behaves primarily However, non-ionizing radiation behaves primarily
as a waveas a wave
Electromagnetic SpectrumElectromagnetic Spectrum
The electromagnetic spectrum covers an entire The electromagnetic spectrum covers an entire range of electromagnetic radiationrange of electromagnetic radiation
Which of these are considered to be non-Which of these are considered to be non-ionizing?ionizing?
Electromagnetic SpectrumElectromagnetic Spectrum
Non-ionizing
Types of Non-Ionizing Types of Non-Ionizing RadiationRadiation
1010-18-18 m m 3x103x102626 Hz Hz 1.24x101.24x101212 eV eV
1010-10-10 m m 3x103x101818 Hz Hz 1.24x101.24x1044 eV eV
1010-6-6 m m 3x103x101414 Hz Hz 1.24 eV1.24 eV
101022 m m 3x103x1066 Hz Hz 1.24x101.24x10-8-8 eV eV
Ultraviolet (UV) LightUltraviolet (UV) Light
Ultraviolet light has a wavelength on the Ultraviolet light has a wavelength on the order of 1-100 nanometers (nm)order of 1-100 nanometers (nm)
This is the shortest wavelength of all non-This is the shortest wavelength of all non-ionizing radiationsionizing radiations
Ultraviolet (UV) LightUltraviolet (UV) Light
Ultraviolet light cannot Ultraviolet light cannot be seen by the human be seen by the human eyeeye
It is divided into 3 It is divided into 3 regions regions UVA (most energetic)UVA (most energetic) UVBUVB UVC (least energetic)UVC (least energetic)
Sources of Ultraviolet LightSources of Ultraviolet Light
UV light is emitted UV light is emitted naturally by the sun naturally by the sun and starsand stars
It is produced artificially It is produced artificially by electric lamps and by electric lamps and light bulbslight bulbs
Is Ultraviolet Light Is Ultraviolet Light Dangerous?Dangerous? All UV light can damage skin and eyesAll UV light can damage skin and eyes Over-exposure can lead to sunburn and Over-exposure can lead to sunburn and
various kinds of cancers, including various kinds of cancers, including melanomasmelanomas
It can also lead to weakening It can also lead to weakening
of the immune systemof the immune system
Is Ultraviolet Light Is Ultraviolet Light Dangerous?Dangerous? UV damage to fibrous UV damage to fibrous
tissue is often described as tissue is often described as “photoaging”“photoaging”
Photoaging makes people Photoaging makes people look older because their look older because their skin looses its tightness and skin looses its tightness and it wrinklesit wrinkles
UV Effects by RegionUV Effects by Region
UV-A (400-300 nm)UV-A (400-300 nm) Pigmentation of skin or suntanPigmentation of skin or suntan
UV-B (320-280 nm)UV-B (320-280 nm) Erythemal regionErythemal region Sunburn of skinSunburn of skin Absorbed by cornea of eye (welder’s flash)Absorbed by cornea of eye (welder’s flash)
UV-C (280-220 nm)UV-C (280-220 nm) Bacterial or germicidal effectBacterial or germicidal effect
Protective MeasuresProtective Measures
Ensure that skin and Ensure that skin and eyes are adequately eyes are adequately protected (sunscreen, protected (sunscreen, sunglasses, clothing)sunglasses, clothing)
Never look directly at a Never look directly at a sourcesource
Operate UV lamps in Operate UV lamps in light-tight conditionslight-tight conditions
Visible LightVisible Light
The wavelength of visible light ranges from The wavelength of visible light ranges from 400-700 nanometers400-700 nanometers
Visible light occupies the smallest segment of Visible light occupies the smallest segment of the electromagnetic spectrumthe electromagnetic spectrum
Visible LightVisible Light
Visible light is Visible light is comprised of various comprised of various colorscolors
The separation of The separation of visible light into its visible light into its different colors is different colors is known as known as dispersiondispersion
Visible LightVisible Light
Each color is characteristic of a different Each color is characteristic of a different wavelengthwavelength
Black vs. WhiteBlack vs. White
Technically speaking, Technically speaking, black and white are not black and white are not colors at allcolors at all
Black is the absence of Black is the absence of colorcolor
White is the White is the combination of all combination of all colorscolors
Visible light health effectsVisible light health effects
The wavelength of infrared light ranges The wavelength of infrared light ranges from 1-100 micronsfrom 1-100 microns
When an object is not quite hot enough to When an object is not quite hot enough to radiate visible light, it will emit most of its radiate visible light, it will emit most of its energy in the infraredenergy in the infrared
Sources of Infrared LightSources of Infrared Light
Any object which has a Any object which has a temperature above temperature above absolute zero radiates absolute zero radiates in the infraredin the infrared
Even objects we think Even objects we think of as being very cold, of as being very cold, such as an ice cube, such as an ice cube, emit infrared lightemit infrared light
Sources of Infrared LightSources of Infrared Light
Even humans and Even humans and animals emit infrared animals emit infrared radiationradiation
Visible Light vs. Infrared Visible Light vs. Infrared LightLight Some animals can “see” in the infraredSome animals can “see” in the infrared These images give an idea of how different These images give an idea of how different
the world would look if we had infrared eyesthe world would look if we had infrared eyes
Is Infrared Light Dangerous?Is Infrared Light Dangerous?
Heating of tissues in the body is the principal Heating of tissues in the body is the principal effect of infrared radiationeffect of infrared radiation
Excessive infrared radiation can result in heat Excessive infrared radiation can result in heat stroke and other similar reactions, especially stroke and other similar reactions, especially in elderly or very young individualsin elderly or very young individuals
IR Effects by RegionIR Effects by Region
IR-A (0.75 – 2.5 nm)IR-A (0.75 – 2.5 nm) Penetrates skin to some extentPenetrates skin to some extent Penetrate eyes to retinaPenetrate eyes to retina
IR-B (2.5 – 5 nm)IR-B (2.5 – 5 nm) Almost completely absorbed by upper layers of Almost completely absorbed by upper layers of
Thermal burns on skin & corneaThermal burns on skin & cornea Cataracts (glass blowers)Cataracts (glass blowers)
Microwave RadiationMicrowave Radiation
The wavelength of microwave radiation The wavelength of microwave radiation ranges from about 10 microns to 1 meterranges from about 10 microns to 1 meter
Microwaves have very low energies and very Microwaves have very low energies and very long wavelengthslong wavelengths
Microwave RadiationMicrowave Radiation
Microwave radiation has Microwave radiation has many uses, including:many uses, including: Cellular phonesCellular phones Highway speed controlHighway speed control Food preparationFood preparation
Limit for Microwave OvensLimit for Microwave Ovens
5 mW/cm5 mW/cm22 at 5 cm from surface at 5 cm from surface http://www.fda.gov/cdrh/radhlth/pdf/mwogdeft.pdf
Is Microwave Radiation Is Microwave Radiation Dangerous?Dangerous? Exposure to very high intensity microwaves Exposure to very high intensity microwaves
can result in heating of tissue and an increase can result in heating of tissue and an increase in body temperature (thermal effects)in body temperature (thermal effects)
At low levels of exposure, the evidence for At low levels of exposure, the evidence for production of harmful effects (non-thermal production of harmful effects (non-thermal effects) is unclear and unproveneffects) is unclear and unproven
Is Microwave Radiation Is Microwave Radiation Dangerous?Dangerous?
Currently, exposure Currently, exposure limits are based on limits are based on preventing only thermal preventing only thermal effectseffects
Further research is Further research is needed in order to learn needed in order to learn more about non-thermal more about non-thermal effectseffects
Radiofrequency (RF) Radiofrequency (RF) RadiationRadiation The wavelength of RF radiation (radiowaves) The wavelength of RF radiation (radiowaves)
is greater than 1 meteris greater than 1 meter
Radiofrequency (RF) Radiofrequency (RF) RadiationRadiation Both microwaves and Both microwaves and
radiowaves are used in radiowaves are used in communicationcommunication
As a result, there is As a result, there is considerable overlap considerable overlap between what is between what is identified as a identified as a radiowave and what is radiowave and what is identified as a identified as a microwavemicrowave
Is RF Radiation Dangerous?Is RF Radiation Dangerous?
As with infrared light and microwave As with infrared light and microwave radiation, the primary health effects of RF radiation, the primary health effects of RF radiation are considered to be thermalradiation are considered to be thermal
RF radiation may penetrate the body and be RF radiation may penetrate the body and be absorbed in deep body organs without the absorbed in deep body organs without the skin effects, which can warn an individual of skin effects, which can warn an individual of dangerdanger
Static Magnetic Field Effects at Levels Below 0.5 Static Magnetic Field Effects at Levels Below 0.5 mTmTand Greater Than 0.5mTand Greater Than 0.5mT
Nuclear Magnetic Resonance Imaging (NMR)
Static Magnetic Fields Static Magnetic Fields IntroductionIntroduction Static Magnetic FieldsStatic Magnetic Fields
Nuclear Magnetic Resonance ImagingNuclear Magnetic Resonance Imaging Increasingly used in Biomedical ResearchIncreasingly used in Biomedical Research
in vivoin vivo analysis analysis effectively displays soft tissue contrasts effectively displays soft tissue contrasts MRI is unobstructed by bone MRI is unobstructed by bone
Safety Concerns with Static Safety Concerns with Static Magnetic FieldsMagnetic Fields Attraction of Loose Attraction of Loose
Medical electronic Medical electronic devicesdevices
NMR Mapping 0.5 mTNMR Mapping 0.5 mT
Issues with Static Issues with Static Magnetic Fields < 0.5 mT:Magnetic Fields < 0.5 mT: Space constraints impacts all involvedSpace constraints impacts all involved Concerns of stopping attention at levels Concerns of stopping attention at levels
Magnetic Field Strength (mT) Effect or Limit _________________________________________ __________________________________________
0.5 Implanted devices ceiling 0.15 - 0.5 Distortion in cathode ray tubes 0.3 Analytical balance 0.3 Unshielded video camera 0.15 Monitor interference 0.1 Image intensifier & scintillation camera 0.001 - 0.1 Electron microscope _________________________________________________________________________________________
Note: Earth’s magnetic field is 0.03 to 0.07 mT
SMF Problems Frequently SMF Problems Frequently OccurredOccurred Screen “jitter”Screen “jitter” Other electronic Other electronic
interferenceinterference Perceive Problem = Perceive Problem =
RiskRisk Dynamic SituationDynamic Situation Can lead to other Can lead to other
problemsproblems
SMF RecommendationsSMF Recommendations
Move “General Public” limit farther backMove “General Public” limit farther back Move equipment to lower field levelsMove equipment to lower field levels Solicit worker concernsSolicit worker concerns Map field strengths to near background levelsMap field strengths to near background levels Routine assessments encouragedRoutine assessments encouraged
SMF Recommendations SMF Recommendations (cont.) (cont.) Area postings / brochuresArea postings / brochures Educate workers about anticipated Educate workers about anticipated
interferencesinterferences
SMF ConclusionSMF Conclusion
Be aware of potential equipment effects Be aware of potential equipment effects below 0.5 mTbelow 0.5 mT
Equipment incompatibilities may result in Equipment incompatibilities may result in personnel management difficultiespersonnel management difficulties
Light travels in waves.Light travels in waves. The electromagnetic spectrum is divided The electromagnetic spectrum is divided
into sections based on wavelength.into sections based on wavelength.
What makes laser light What makes laser light different than conventional different than conventional light?light?Laser light has several unique qualities:Laser light has several unique qualities:
1.1. MonochromaticMonochromatic
2.2. DirectionalDirectional
3.3. CoherentCoherent
But what do these mean?But what do these mean?
Monochromatic LightMonochromatic Light
MonochromaticMonochromatic light is light is light consisting of one light consisting of one wavelength only.wavelength only.
Monochromatic
Polychromatic
Directional LightDirectional Light
DirectionalDirectional light has light has very low divergence.very low divergence.
Conventional light Conventional light spreads in all spreads in all directions, but laser directions, but laser light remains focused.light remains focused.
Directional
Non-Directional
Coherent LightCoherent Light
Coherent lightCoherent light consists consists of waves that are in of waves that are in phase with each other.phase with each other.
Lasing MaterialLasing Material
Lasers contain a medium which is used to Lasers contain a medium which is used to cause the monochromatic effect. There are cause the monochromatic effect. There are several states of lasing mediumseveral states of lasing medium Solid State- Crystal injected “dopant”Solid State- Crystal injected “dopant” Semiconductor- Diode laserSemiconductor- Diode laser Liquid- dye laserLiquid- dye laser Gas- C02 laserGas- C02 laser
Laser ConstructionLaser Construction
Lasing Medium Lasing Medium (gas, liquid, solid, semiconductor)(gas, liquid, solid, semiconductor)
• Determining site boundaries for constructionDetermining site boundaries for construction
IndustrialIndustrial• CuttingCutting
• WeldingWelding
Laser Hazard ClassificationLaser Hazard ClassificationANSI Z136.1-2000 StandardANSI Z136.1-2000 Standard
Class 1 (Exempt)Class 1 (Exempt)• Incapable of producing Incapable of producing
damaging radiation levelsdamaging radiation levels Class 2 (Low power) Class 2 (Low power)
• Eye protection is an Eye protection is an aversion responseaversion response
• Visible (400-700nm)Visible (400-700nm)• CW upper limit is 1mWCW upper limit is 1mW
Laser Hazard ClassificationLaser Hazard ClassificationANSI Z136.1-2000 Standard (con’t)ANSI Z136.1-2000 Standard (con’t)
Class 3 (Medium Power)Class 3 (Medium Power)• Divided into subclasses, 3a and 3bDivided into subclasses, 3a and 3b• Hazardous under direct or specular reflectionHazardous under direct or specular reflection• Non-hazardous under diffuse reflectionNon-hazardous under diffuse reflection• Normally non fire hazardNormally non fire hazard• CW upper limit 0.5 WCW upper limit 0.5 W
Laser Hazard ClassificationLaser Hazard ClassificationANSI Z136.1-2000 Standard (con’t)ANSI Z136.1-2000 Standard (con’t)
Class 4 (High Power)Class 4 (High Power)• Hazardous to eye and skin from direct Hazardous to eye and skin from direct
viewing/contact, specular, and diffuse viewing/contact, specular, and diffuse reflectionsreflections
• Produce non-beam hazardous such as air Produce non-beam hazardous such as air contaminantscontaminants
• Fire hazard Fire hazard
Bio-EffectsBio-Effects
Primary sites of damagePrimary sites of damage eyeseyes skinskin
Laser beam damage can beLaser beam damage can be thermal (heat)thermal (heat) acousticacoustic photochemicalphotochemical
Eye Bio-EffectsEye Bio-Effects
Three different ways for eye exposureThree different ways for eye exposure Retina (visible and Retina (visible and
IR-A)IR-A) Cornea (UV-B, Cornea (UV-B,
UV-C, IR-C)UV-C, IR-C) Lens (UV-A)Lens (UV-A)
Eye Bio-Effects Eye Bio-Effects (con’t)(con’t)
•Visible (400-700 nm)•Possible damage to Retina
Eye Bio-Effects Eye Bio-Effects (con’t)(con’t)
•Near-ultraviolet (100-330 nm)•Possible damage to Cornea
How Often Do Accidents How Often Do Accidents Occur?Occur?
Causative Agent for Accidental Exposure
28%
6% 16%
50%
ExposuredurringalignmentImproper eyewear
Available eyeprotection notusedother
General Laser SafetyGeneral Laser Safety
Wear appropriate protective eyewearWear appropriate protective eyewear Use minimum power/energy required for projectUse minimum power/energy required for project Reduce laser output with shutters/attenuators, if possibleReduce laser output with shutters/attenuators, if possible Terminate laser beam with beam trapTerminate laser beam with beam trap Use diffuse reflective screens, remote viewing systems, etc., Use diffuse reflective screens, remote viewing systems, etc.,
during alignments, if possibleduring alignments, if possible Remove unnecessary objects from vicinity of laserRemove unnecessary objects from vicinity of laser Keep beam path away from eye level (sitting or standing)Keep beam path away from eye level (sitting or standing)
Non-Beam HazardsNon-Beam Hazards
ChemicalChemical Chemical used in dye lasers can be known carcinogens Chemical used in dye lasers can be known carcinogens
or toxic also maybe difficult to disposeor toxic also maybe difficult to dispose OpticalOptical
Plasma radiation can be produced. Similar to welders Plasma radiation can be produced. Similar to welders flashflash
FireFire Class 3b and 4 lasers with high power outputs can Class 3b and 4 lasers with high power outputs can
cause firescause fires ElectricalElectrical
Most common, very high incident in maintenance Most common, very high incident in maintenance
Engineering Control Engineering Control MeasuresMeasures Beam housingsBeam housings
Activation Warning SystemActivation Warning System
ShuttersShutters
Beam Stop or AttenuatorBeam Stop or Attenuator
Remote firing controlsRemote firing controls
InterlocksInterlocks
Administrative Control Administrative Control MeasuresMeasures
GlovesGloves Be wary of neck ties.Be wary of neck ties. Special clothingSpecial clothing
Eyewear must be for the appropriate laser wavelength, attenuate the beam to
safe levels.
Emergency Procedure Emergency Procedure Shut down the laser systemShut down the laser system
Provide for the safety of the personnel, I.e. first aid, Provide for the safety of the personnel, I.e. first aid,
CPR, etc.CPR, etc.
If necessary, contact the fire department If necessary, contact the fire department
Inform the Radiation Safety DivisionInform the Radiation Safety Division Inform the Principal InvestigatorInform the Principal Investigator
DO NOT RESUME USE OF THE LASER SYSTEM WITHOUT APPROVAL DO NOT RESUME USE OF THE LASER SYSTEM WITHOUT APPROVAL
OF THE LASER SAFETY OFFFICEROF THE LASER SAFETY OFFFICER
IrradianceIrradiance
E = Irradiance = W/cm2E = Irradiance = W/cm2 ФФ = total radiation power W = total radiation power W A = areaA = area a = beam diametera = beam diameter r = viewing distancer = viewing distance ΘΘ = beam divergence = beam divergence
