The recommended limit for I-131 in drinking water was 3 × 10-5 μCi per milliliter (Table 3, page 15). This corresponds to a daily intake limit of 6.6 × 10-2 μCi which, if consumed over an entire year, would result in an estimated dose rate to the thyroid of 0.3 rem per week, or 15 rem per year (Section E, page 12).
In a report issued in 1954, the NCRP (1954) recommended that
… in the course of their normal activities, protective measures be taken to make sure that no minor actually receives radiation at a weekly rate higher than one-tenth the respective permissible weekly doses for the critical organs (page 78).
In 1957, the NCRP issued an addendum to Handbook 59. This addendum repeated the NCRP recommendation for an occupational dose rate limit of 15 rem per year, but the maximum accumulated dose was limited to 5 times the number of years beyond age 18 (NCRP, 1957, paragraph 1, page 2). This addendum also included new recommendations for limiting the genetic dose to the population (paragraph 5, page 3), and stated, in terms of internal emitters, that:
For individuals outside of the controlled area, the maximum permissible concentrations should be one-tenth of those for occupational exposures (paragraph 6, page 3).
The NCRP also recommended:
An average per capita dose limit of 0.5 rem per year for "persons outside of controlled areas, but exposed to radiation from a controlled area" (paragraph 12, page 4).
It should be noted, however, that this dose rate limit was based on the assumption that:
… the total integrated RBE dose received by radiation workers will be small in comparison with the integrated RBE dose of the whole population (paragraph 12, page 4).
In addition, for purposes of controlling potential genetic effects, it was further assumed that:
… persons outside of controlled areas, but exposed to radiation from a controlled area, constitute only a small portion of the whole population.
In 1959, the NCRP issued Handbook 69 (NCRP 1959) which incorporated new data and methods for estimating the dose from internally deposited radionuclides. In the Handbook the NCRP stated its recommendations as follows: