Final answer:
The average annual gonadal equivalent dose for those of childbearing age is not given, but the worldwide average exposure from natural sources is about 3 mSv per year. The risk of genetic defects is about one-third the risk of cancer deaths due to radiation. Typical exposure levels fall into the low dose category based on the linear hypothesis for radiation risk assessment.
Step-by-step explanation:
The average annual gonadal equivalent dose for individuals of childbearing age is not explicitly given in the provided references. However, we can deduce some information about the typical dose people receive. The average background radiation dose from all natural and artificial sources varies by region. For example, sources suggest that the world-wide average radiation exposure from natural sources is about 3 mSv (or 300 mrem) per year, which includes cosmic rays and radon. Specific data from the airline industry shows they have an average exposure of 2 mSv per year due to increased cosmic radiation exposure at higher altitudes during flights.
According to the linear hypothesis, the risk of low doses of radiation, which are typical of background exposure, is directly proportional to the risk observed at high doses. This suggests that while effects of low doses are not readily observed, there's an assumed consistent increase in risk with increasing dose. For gonadal equivalent doses specifically, it is understood that any ionizing radiation exposure has the potential to cause genetic defects and cancer, with estimates of genetic defects being approximately one-third that for cancer.
For realistic context, note that the annual whole-body doses of 0.1 Sv or less are considered low, while those of 0.1 to 1 Sv are moderate, and those above 1 Sv are considered high doses. Going by this, the average background dose received, at around 3 mSv, is well within the low dose category. While this background radiation data does not directly answer the question regarding gonadal equivalent dose, it does provide some context for what can be considered typical exposure levels.