Hereditary Radiation Risks (and Fertility Radiation Risks)

Male and Female hereditary radiation risks and fertility radiation risks are important for all medical professionals to understand especially radiologic technologists, radiographers, and radiologists.

For a detailed illustrated guide see:
https://howradiologyworks.com/fertili...

Radiation risks to germline cells (sperm and ova) include reduced fertility, and hereditary risks of increased mutation rate. These effects are dependent on the radiation dose: (males) [0.15-0.5 Gy] reduced sperm count, [0.5-6 Gy] temporary sterility, [greater 6 Gy] permanent sterility, and (females) [2-12 Gy depending on age] causes permanent sterility. Hereditary risks of increased mutations have been demonstrated in animal models but data with humans in insufficient.

Chapters
00:00. Intro
01:27. Mutations and Hereditary Radiation Effects
02:40. Male Fertility Risks with Radiation
04:15. Female Sterility from radiation (Female Fertility)
05:45. Animal experiments for Hereditary Effects of radiation
07:13. Human risk model Hereditary Radiation
08:30. No direct evidence for human heritable effects
09:20. Gestational effects (coming attractions)

Males
If the dose is relatively large, radiation can cause fertility issues as well. In men, if the radiation dose is around 6 Gy, it can cause permanent loss of fertility (i.e. sterility). In the case of dose levels from 0.5 Gy, up to 6 Gy, there will be a period of temporary sterility. The temporary sterility will be delayed from the time when the radiation dose is received, as sperm cells are constantly being regenerated. The delay is about 6 weeks between the moment when dose is given and when sterile period occurs. It then can take from ~10 months – 20 months for the sperm count to return to its highest level.

At lower radiation doses (0.15 Gy – 0.5 Gy) there can be a reduction in the sperm count. In this case there is not full sterility but there can be a reduction in fertility due to the lower sperm count.

In men the hormones and libido are unaffected by radiation as the hormones do not originate from the same location as the sperm cells.

Unfortunately, much of the information on radiation effects for spermatogenesis (sperm generation) came from a University of Washington study during the years 1963-1968 where 200 inmates at the Washington State Penitentiary received relatively high levels of radiation without medical benefit. This type of study would not be approved today.

Females
If the radiation exposure occurs to a rather young female, it can take up to 12 Gy to cause the sterility. However, for older women who are close to menopause radiation dose of 2 Gy can lead to permanent sterility.

Woman will experience all the same symptoms of going through menopause as the ovaries produce the hormones oestrogen and progesterone. As mentioned above this is in contrast to men where the hormone levels will not be affected by the radiation.


Animal Experiments
The first experiments of hereditary effects were done in fruit flies. Hermann Muller received the Nobel prize in 1946 for the discovery of mutations due to radiation. The experiments were done relatively easily because of large number of fruit flies that can be studied and their relatively short lifespan.

Different mutations that occurred were eye color changes from red to white and the doubling dose was 0.05 Gy to 1.5 Gy depending on the situation.

William and Liane Russel were pivotal in carrying out the so-called “mouse house” studies where roughly a quarter million mice were included in a given study and 7 million mice over all of the studies from 1947-2009.

In mutant mice different colors appeared at a higher rate when exposed to radiation. The doubling dose for mice was about 1 Gy (there was a dependence on the dose rate, i.e how quickly the dose was given and 1 Gy was for the relatively lower dose rate conditions).

Human Risk Assessment
There is not sufficient data to determine if there are hereditary risks at the low radiation doses of diagnostic x-ray and CT scanning. A quotation from the BEIR-VII (Biological Effects of Ionizing Radiation) summary on this, “However, there is no direct evidence of increased risk of non-cancer diseases at low doses, and data are inadequate to quantify this risk if it exists.”

An additional quote from the full text of an earlier version, BEIR-V is “Due to lack of increase in human heritable effects resulting from radiation exposure the estimates of genetic risks in humans are based primarily on experimental data obtained with laboratory animals.”

A hybrid model has been used in practice to attempt to estimate the potential hereditary risk. This model takes as assumptions the mutation rate in the regular population, and uses experimental data from animal models to estimate the impact of radiation via the doubling dose data (doubling dose 1Gy from mouse data).