Chapter 5 - Effects of Long-Term Exposure to Radiation

Major Organogenesis

*2nd to 8th week after conception *radiation can cause CNS congenital anomalies at low LET

Fetal Growth stage

*9th week to term *negligible aberration at this stage *damage during this stage may not manifest until later in life, such as behavioral changes, reduced IQ, or cancer.

Breast Cancer

*Age dependent *Linear dose Response *Latent Period 10-40 yrs

Leukemia

*Can be ACUTE or CHRONIC *LYMPHOID or MYELOID *Judged to be Linear and Nonthreshold *Latent Period 4-7 yrs *at risk period 15-20 yrs *BEIR suggest Relative risk, nonlinear dose response relationship *Considerate a rare disease. *Most Frequent observed radiation induced cancer. *No evidence of radiation-induced leukemia in American Radiographers. *Radiation-Induced Leukemia decreases with age.

Skin Carcinoma

*Follows a Threshold dose response *latent period 5-10 yrs *Not present in current Radiology personnel

Osteosarcoma

*Radium Girls 1920's *Linear quadratic dose response relationship

Thyroid Cancer

*Responsible for Approx 12% of radiation induced cancer deaths *Benign or Malignant *Papillary or Follicular *Latent Period for Benign 5-35 yrs *Latent Period for Malignant 10-35 yrs *Linear, Nonthreshold dose response

Genetic Damage

*Studies in Fruit flies in 1927 by Herman Muller 1. no new or unique mutations are produced by radiation. 2. In doses range 25-400R the frequency of mutations was linear with dose 3. the majority of radiation-induced mutations were recessive 4. there were no dose rate or dose fractionation effects on going studies on Mullers research by Russell in 1946 1. radiation is a powerful mutagenic agent 2. the majority of mutations are unhealthy to the organism 3. there are no unique mutations produced by radiation 4. radiation induced genetic damage can occur as the result of a single mutation

Pre-Implantation Stage

*originates with the joining of sper and egg *continues to 9th day when zygote becomes deposited in uterine wall *fertilized egg is rapidly dividing *radiation can cause prenatal death or recovery.

Turner's Syndrome

Endocrine disorder caused by the failure of the ovaries to respond to pituitary hormone stimulation.

Parenchymal

Essential life sustaining cells

Absolute Risk Model

Estimates a continual increase in risk, independent of the age-specific cancer risk at time of exposure; also known as the additive risk model.

Carcinoma

Growth or Tumor

Radium

Half-life 1620 yrs

Limitations on epidemiologic studies include:

. Failure to control experimental group for know carcinogens . Insufficient observation . Using proper control group . Deficient/incorrect health records

Lung Cancer

.Linear nonthreshold

Sources of Data on incidence of radiation-induced cancer:

1. Atomic bomb survivors 2. Medically exposed patients 3. Occupationally Exposed personnel 4. Population that receive high natural background radiation

3 stages of Fetus

1. Pre-Implantation 2. Major Organogenesis 3. Fetal Growth Stage

Genetically Significant Dose (GSD)

An average calculated from the gonadal dose received by the entire population and used to determine the genetic influence of low dose to the whole population

Osteosarcoma

Bone Cancer

BEIR Committee

Committee on the Biological Effects of Ionizing Radiation

Non-stochastic

Deterministic; the severity of the injury increases with the dose, not the chance of it occurring

Ankylosing spondylitis

Immobility of the vertebrae

Myeloid

In Marrow

Lymphoid

In the lymph tissue

Absolute risk dose-response

Linear dose response

Life-Span Shortening and dose

Linear, non-threshold

Papillary

Nipple like protrusion

Benign

Nonprogressive

type of dose-reponse curve for Diagnostic and Occupational Exposures

Nonthreshold linear curve

Relative Risk Formula

Observed cases ------------------ Expected cases

BEIR Committee uses what risk model

Relative risk model

Life-Span Shortening

Studies on animals that received acute and chronic radiation indicated that animals that were chronically irradiated died younger than animals that were not irradiated.

Epidemiology

The Science that examines the incidence, distribution, and control of disease in population

Follicular

cavity

excess risk formula

observed cases - expected cases

Stochastic

occurring randomly in nature; the probability of being affected increases with the dose

progeny

offspring

Dose-Response Curve

predicts cancer risk in human population that have been exposed to low levels of radiation.

Malignant

progressive

radio-carcinogenesis

radiation producing cancer

Acute

rapid and severe

Chronic

slow and progressive

loci

spot, place of origin

Radiation Hormesis

the controversial hypothesis that chronic low doses of ionizing radiation stimulates repair mechanism that protect against disease.

doubling dose

the dose of radiation required per generation to double the spontaneous mutation rate.

Excess risk

the number of excess cases of cancer observed compared with expected spontaneous occurrence.

Neoplasms

tumor