Radiation methods of sterilization MCQs With Answer

Radiation methods of sterilization MCQs With Answer provide B.Pharm students a focused and practical way to master sterilization by gamma rays, electron beam (e-beam) and X‑rays. This introduction covers mechanisms of microbial inactivation, dose concepts (kGy, D10), sterility assurance level (SAL), dosimetry techniques, material compatibility and ISO standards like ISO 11137. Keywords: radiation sterilization, gamma irradiation, electron beam, X‑ray sterilization, dosimetry, D10 value, sterility assurance level, sterilization validation, cobalt‑60. Clear understanding of these topics helps pharmacists design, validate and troubleshoot radiation sterilization for pharmaceuticals and medical devices. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. What is the primary mechanism by which ionizing radiation sterilizes microorganisms?

• Thermal denaturation of proteins
• Generation of free radicals causing DNA and cellular damage
• Desiccation of cells
• Disruption of cell membranes by detergents

Correct Answer: Generation of free radicals causing DNA and cellular damage

Q2. Which unit is used to express absorbed dose in radiation sterilization?

• Sievert (Sv)
• Gray (Gy)
• Roentgen (R)
• Curies (Ci)

Correct Answer: Gray (Gy)

Q3. What dose is commonly cited as a standard sterilization dose for many medical devices?

• 2.5 Gy
• 25 kGy
• 250 Gy
• 250 kGy

Correct Answer: 25 kGy

Q4. The D10 value represents:

• The dose required to sterilize 1,000 items
• The dose that reduces microbial population by 10%
• The dose that reduces microbial population by 90%
• The dose that increases microbial growth by 10%

Correct Answer: The dose that reduces microbial population by 90%

Q5. Which of the following radiation sources is commonly used for industrial gamma sterilization?

• Cobalt‑60
• Uranium pellets
• Radium‑226
• Plutonium‑239

Correct Answer: Cobalt‑60

Q6. Compared to gamma rays and X‑rays, electron beam (e‑beam) irradiation is characterized by:

• Greater penetration depth
• Lower penetration but higher dose rate
• No production of free radicals
• Longer exposure times for the same dose

Correct Answer: Lower penetration but higher dose rate

Q7. Which dosimeter is commonly used for routine dose verification in radiation sterilization?

• Fricke dosimeter
• Thermoluminescent dosimeter (TLD)
• Geiger‑Müller counter
• Photographic plate

Correct Answer: Thermoluminescent dosimeter (TLD)

Q8. ISO 11137 is an international standard related to:

• Validation of steam sterilization
• Validation and routine control of radiation sterilization processes
• Packaging regulations for food
• Testing of antimicrobial preservatives

Correct Answer: Validation and routine control of radiation sterilization processes

Q9. Which free radical is most responsible for indirect DNA damage during water radiolysis?

• Hydrogen peroxide (H2O2)
• Hydroxyl radical (•OH)
• Superoxide anion (O2•−)
• Nitric oxide (NO•)

Correct Answer: Hydroxyl radical (•OH)

Q10. Sterility Assurance Level (SAL) of 10^-6 means:

• One in a million chance a unit is non‑sterile
• Six surviving organisms per item
• One unit in ten is sterile
• Six log reduction is required

Correct Answer: One in a million chance a unit is non‑sterile

Q11. Which parameter describes the uniformity of dose within a product load?

• D10 value
• DUR (Dose Uniformity Ratio)
• Activity in curies
• Sterility Assurance Level

Correct Answer: DUR (Dose Uniformity Ratio)

Q12. Alanine dosimeters are preferred because they:

• Are inexpensive but unstable
• Provide high precision and are stable for long‑term readout
• Detect only gamma rays
• Change color visibly to indicate dose

Correct Answer: Provide high precision and are stable for long‑term readout

Q13. Which organism is commonly used for biological indicators in radiation sterilization validation?

• Geobacillus stearothermophilus
• Bacillus pumilus or Bacillus subtilis spores
• Escherichia coli
• Saccharomyces cerevisiae

Correct Answer: Bacillus pumilus or Bacillus subtilis spores

Q14. X‑ray sterilization is produced by:

• Direct decay of cobalt‑60
• Accelerating electrons onto a metal target
• Thermal excitation of atoms
• Chemical reactions in packaging

Correct Answer: Accelerating electrons onto a metal target

Q15. Which statement about radiolysis of pharmaceuticals is true?

• Radiolysis only affects aqueous solutions
• Radiation can cause degradation, requiring compatibility studies
• All drugs become more potent after irradiation
• Plastic containers prevent any radiolytic effects

Correct Answer: Radiation can cause degradation, requiring compatibility studies

Q16. The Gray (Gy) is defined as:

• Amount of radiation that produces one ion pair
• One joule of energy absorbed per kilogram of matter
• One Curie of activity per liter
• Dose rate measured per minute

Correct Answer: One joule of energy absorbed per kilogram of matter

Q17. Which packaging property is most important for gamma sterilization?

• Transparency to visible light
• Permeability to oxygen
• Radiation stability and adequate barrier properties
• Magnetic susceptibility

Correct Answer: Radiation stability and adequate barrier properties

Q18. Which method is used to determine the biological reduction caused by a given radiation dose in validation?

• DUR mapping
• Bioburden estimate and D10 determination
• Fricke chemical test only
• Visual inspection of product

Correct Answer: Bioburden estimate and D10 determination

Q19. Which of the following is a chemical dosimeter used for measuring absorbed dose?

• Fricke dosimeter (ferrous sulfate)
• Thermocouple
• Gas chromatograph
• Optical microscope

Correct Answer: Fricke dosimeter (ferrous sulfate)

Q20. Which radiation type typically requires the shortest exposure time for equivalent surface sterilization?

• Gamma rays
• Electron beam (e‑beam)
• X‑rays
• Ultraviolet light

Correct Answer: Electron beam (e‑beam)

Q21. Which factor does NOT directly affect radiation sterilization efficacy?

• Initial bioburden
• Packaging density and thickness
• Ambient humidity during shipment after irradiation
• Dose delivered

Correct Answer: Ambient humidity during shipment after irradiation

Q22. Dose mapping in a product load is performed to:

• Measure microbial growth
• Determine minimum and maximum doses received within load
• Change the chemical structure of the product
• Calibrate the electrical supply

Correct Answer: Determine minimum and maximum doses received within load

Q23. Which organism has unusually high resistance to ionizing radiation?

• Deinococcus radiodurans
• Staphylococcus aureus
• Pseudomonas aeruginosa
• Clostridium tetani

Correct Answer: Deinococcus radiodurans

Q24. What is a major advantage of radiation sterilization over ethylene oxide sterilization?

• No effect on any packaging materials
• It does not require long aeration times to remove toxic residues
• Lower capital cost
• Works only on liquids

Correct Answer: It does not require long aeration times to remove toxic residues

Q25. Which metric quantifies the dose required to achieve a specified SAL based on bioburden?

• Activity in becquerels
• Validation dose or sterilization dose determination
• Optical density at 600 nm
• Minimum inhibitory concentration

Correct Answer: Validation dose or sterilization dose determination

Q26. Radiochromic films are useful as dosimeters because they:

• Require complex chemical readout
• Change color proportionally to absorbed dose and are easy to read
• Only respond to alpha particles
• Evaporate after irradiation

Correct Answer: Change color proportionally to absorbed dose and are easy to read

Q27. Which statement about electron beam sterilization is true?

• It uses radionuclide decay like cobalt‑60
• It achieves deep penetration in very dense loads
• It is ideal for surface and near‑surface sterilization due to limited penetration
• It cannot be used for packaged products

Correct Answer: It is ideal for surface and near‑surface sterilization due to limited penetration

Q28. A high Dose Uniformity Ratio (DUR) indicates:

• Good uniformity of dose across the load
• Poor uniformity with large dose variation
• Dose is identical at all points
• No need for dosimetry

Correct Answer: Poor uniformity with large dose variation

Q29. Which regulatory document would you consult for radiation sterilization of medical devices?

• ICH Q1A
• ISO 11137
• USP General chapters on microbiology only
• Pharmacopoeia monographs for tablets

Correct Answer: ISO 11137

Q30. What is the effect of dose rate on microbial inactivation for a given total dose?

• Higher dose rates always reduce efficacy
• Dose rate can influence repair during irradiation, but total dose is primary determinant
• Dose rate has no biological effect
• Lower dose rates always produce more radical species

Correct Answer: Dose rate can influence repair during irradiation, but total dose is primary determinant

Q31. Which chemical change is commonly observed in polymers after irradiation?

• Complete melting at room temperature
• Crosslinking or chain scission depending on polymer type
• Conversion to metal
• Spontaneous combustion

Correct Answer: Crosslinking or chain scission depending on polymer type

Q32. For liquid pharmaceuticals, a key concern during irradiation is:

• Loss of container transparency only
• Radiolytic degradation of active pharmaceutical ingredients and formation of by‑products
• Inability to penetrate plastics
• Generating magnetic fields

Correct Answer: Radiolytic degradation of active pharmaceutical ingredients and formation of by‑products

Q33. Which is a common approach to set a sterilization dose when bioburden is low?

• Use a fixed universal 10 kGy dose
• Bioburden‑based dose setting per ISO 11137
• No validation required
• Always use ethylene oxide instead

Correct Answer: Bioburden‑based dose setting per ISO 11137

Q34. Which analytical method can be used to detect radiolytic degradation products?

• High‑performance liquid chromatography (HPLC)
• Only visual inspection
• Thermogravimetric analysis exclusively
• Paper pH indicator

Correct Answer: High‑performance liquid chromatography (HPLC)

Q35. Which statement about cobalt‑60 sources is correct?

• Cobalt‑60 emits beta particles only
• Cobalt‑60 emits high‑energy gamma photons used for deep penetration sterilization
• Cobalt‑60 decays into uranium
• Cobalt‑60 is produced by X‑ray machines

Correct Answer: Cobalt‑60 emits high‑energy gamma photons used for deep penetration sterilization

Q36. What is the role of routine dosimetry in a radiation sterilization facility?

• To monitor environmental temperature only
• To verify that the planned dose was delivered to loads during routine processing
• To sterilize the product
• To replace biological indicators

Correct Answer: To verify that the planned dose was delivered to loads during routine processing

Q37. Which factor increases the resistance of microorganisms to radiation?

• Being in a hydrated state
• Being in a dry, spore form with protective proteins
• Presence of oxygen radicals
• Low initial bioburden

Correct Answer: Being in a dry, spore form with protective proteins

Q38. Which method can reduce radiolytic damage to sensitive pharmaceuticals during irradiation?

• Removing oxygen by nitrogen sparging or vacuum packaging
• Increasing storage temperature during irradiation
• Exposing product to sunlight immediately after irradiation
• Using glass packaging only

Correct Answer: Removing oxygen by nitrogen sparging or vacuum packaging

Q39. Which of the following is a limitation of electron beam sterilization?

• High radioactive waste generation
• Limited penetration depth into dense or thick loads
• Very slow processing times
• Inability to sterilize surfaces

Correct Answer: Limited penetration depth into dense or thick loads

Q40. What does “substantiation of dose” in ISO 11137 refer to?

• Providing evidence that a chosen dose achieves the required SAL for specific product configuration
• Manufacturing a radioactive source
• Measuring product weight changes after irradiation
• Testing only packaging materials

Correct Answer: Providing evidence that a chosen dose achieves the required SAL for specific product configuration

Q41. Which analytical indicator would be suitable to monitor oxidative radiolysis in aqueous formulations?

• Measurement of peroxide formation (e.g., H2O2)
• Visual turbidity only
• Colorimeter for plastics
• Magnetic resonance imaging

Correct Answer: Measurement of peroxide formation (e.g., H2O2)

Q42. Which packaging material is generally most susceptible to radiation‑induced oxidative degradation?

• Polyethylene
• Stainless steel
• Glass
• Ceramic

Correct Answer: Polyethylene

Q43. What does a biological indicator typically contain for radiation sterilization validation?

• Vegetative bacterial cells in liquid
• Defined population of resistant bacterial spores on a carrier
• Viral particles only
• Fungal hyphae

Correct Answer: Defined population of resistant bacterial spores on a carrier

Q44. Which parameter must be minimized to achieve predictable sterilization in a radiation chamber?

• Dose Uniformity Ratio (DUR)
• Shelf life
• Cost of packaging
• Room lighting

Correct Answer: Dose Uniformity Ratio (DUR)

Q45. Which is true regarding radiation sterilization of bulk pharmaceutical powders?

• Powders are immune to radiolytic changes
• Particle size and density affect dose penetration and must be evaluated
• Only liquids can be irradiated
• All powders require 100 kGy

Correct Answer: Particle size and density affect dose penetration and must be evaluated

Q46. Which phenomenon can reduce the effective dose delivered to organisms inside a dense product?

• Shadowing or self‑shielding by product mass
• Increased oxygen concentration
• Lower humidity
• Faster conveyor speed

Correct Answer: Shadowing or self‑shielding by product mass

Q47. Which step is essential before routine radiation sterilization of a new product?

• Assuming 25 kGy is always sufficient
• Conducting validation including bioburden, D10, dose setting and dose mapping
• Shipping product without testing
• Only testing packaging seal strength

Correct Answer: Conducting validation including bioburden, D10, dose setting and dose mapping

Q48. Radiation causes breaks in DNA strands; which type of break is most lethal to microbes?

• Single‑strand break easily repaired
• Double‑strand break difficult to repair and often lethal
• Base oxidation only
• Minor groove binding

Correct Answer: Double‑strand break difficult to repair and often lethal

Q49. Which monitoring approach provides direct evidence of microbial inactivation after irradiation?

• Chemical dosimeter only
• Biological indicator survival testing
• Measuring humidity in the chamber
• Checking package color

Correct Answer: Biological indicator survival testing

Q50. For regulatory compliance, documentation of a radiation sterilization process should include:

• Only production dates
• Validation reports, dose setting, dosimetry data, bioburden and routine control procedures
• Marketing materials
• Employee names only

Correct Answer: Validation reports, dose setting, dosimetry data, bioburden and routine control procedures

G S Sachin

I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.

Mail- Sachin@pharmacyfreak.com