Topic 2 - Regulatory Agencies

Radiation Protection Standards

• Dangers of X rays & radium quickly recognized
• 1928 ICRP formed by the International Society of Radiology
• NCRP founded 1929 (as advisory committee on X-ray and Radium protection)

Evolution of Dose Standards

• Early years - based on skin reddening
  • monthly limit: 1/100th of amount that would cause erythema in acute exposure
• Roentgen defined in 1930s
  • old limit was 600 R
• ICRP / NCRP adopted 0.02 / 0.01 R as daily “tolerance” dose for workers

Limits for Occupational Exposure

• Initial limits were for workers & external radiation
• Limits on internal emitters began in 1920
• Benchmarks before WWII
  • 0.1 R/d whole-body
  • 0.1 mCi (3.78 kBq) as maximum body burden of 226Ra
• These standards set basis for safe handling of radiation at the start of atomic energy program
• Early standards were adapted to address other unstudied radiations (like neutrons) encountered during the war effort
• Concept of biological effectiveness (rep, rem) added
• Rising concern about possible stochastic (e.g., cancer, genetic) effects resulted in lowering of dose to 0.3 rem/wk
• 1956 - ICRP recommended gonadal & blood-forming organ limit of 5 rem/y
• Also restricted accumulated dose to 5 (N-18)
• Limited exposure before age 18
• Limited dose to 3 rem/13 weeks
• 1977 next change - limit of 5 rem/y; no lifetime limit
• Other changes: method used to calculate dose (1977)
  • old method: critical organ (~15 rem) & whole body
  • new method: considered differences in radiosensitivity of organs (tissue weighting factors)
• Consequence: some difficulty in comparing old and new doses

Limits for Exposure of General Public

• Public dose not really considered until 1950s
• General practice to set public limit below occupational levels
• Concept of “no-threshold” for risks demanded no exposure without expectation of benefit (FRC 1960)
• ALARA concept also introduced

Radiation Standards for the Public

• 1955, ICRP, 1/10 of occupational levels
• 1977, ICRP, public dose limited to 0.1 rem/yr, sometimes 0.5
• applied to intended release of radioactive materials
• EPA recently recommended (then rescinded) limiting dose from contaminated sites to 15 mrem (NRC - 25 mrem)

Environmental Radiation Standards

• NCRP (indoor radon)
• FAO (radionuclides in food)
• EPA (air emissions)
• NRC

Radiation Protection Standards

• Changes in Concepts of Standard Setting
  • old standards adequate
  • new standards consider ALARA, BAT, acceptable risks
• How Modern Protection Standards are Established
  • Gather scientific data (NAS/NRC, ICRP, NCRP, UNSCEAR, etc)
  • Fight a lot
  • Do what’s politically expedient
• Organizations involved in establishing and implementing standards
  • NRC
  • EPA
  • FDA
  • States
  • Municipalities
  • DOT
  • International Agencies
  • Others

Summary

• Standards have evolved in response to:
  • Increased understanding of radiation response
  • Public & political pressures
  • No “major” shift in standards (in U.S.) since 1950s
    • “minor” calculational change
• Several categories of standards
  • Occupational
  • Public
  • Environmental
  • Remediated sites
  • Decommissioned sites
• Many Agencies involved in process
• Inconsistencies abound
  • Within agencies
  • Between agencies
• Standards are continuing to evolve