(a) For the purpose of this section, a ``working level'' is defined
as any combination of radon daughters in 1 liter of air which will
result in the ultimate emission of 1.3 x 105 million electron
volts of potential alpha energy. The numerical value of the ``working
level'' is derived from the alpha energy released by the total decay of
short-lived radon daughter products in equilibrium with 100 pico-curies
of radon 222 per liter of air. A working level month is defined as the
exposure received by a worker breathing air at one working level
concentration for 4\1/3\ weeks of 40 hours each.
(b)(1) Occupational exposure to radon daughters in mines shall be
controlled so that no individual will receive an exposure of more than 2
working level months in any calendar quarter and no more than 4 working
level months in any calendar year. Actual exposures shall be kept as far
below these values as practicable.
(2) In enforcing this section, the Director of the Bureau of Labor
Standards may at any stage approve variations in individual cases from
the limitation set forth in paragraph (b)(1) of this section to comply
with the requirements of the Act upon a showing to the satisfaction of
the Director by an employer having a mine with conditions resulting in
an exposure of more than 4 working level months but not more than 12
working level months in any 12 consecutive months that (i) under the
particular facts and circumstances involved the working conditions of
the employees so exposed are such that their health and safety are
protected, and (ii) the employer has a bona fide plan to reduce the
levels of exposure to those specified in paragraph (b)(1) of this
section as soon as practicable, but in no event later than January 1,
1971.
(3) Whenever a variation under paragraph (b)(2) of this section is
sought, a request therefor should be submitted in writing to the
Director of the Bureau of Labor Standards, U.S. Department of Labor,
Washington, DC 20210, within 90 days following the end of the calendar
quarter or year, as the case may be.
(c)(1) For uranium mines, records of environmental concentrations in
the occupied parts of the mine, and of the time spent in each area by
each person involved in underground work shall be established and
maintained. These records shall be in sufficient detail to permit
calculations of the exposures, in units of working level months, of the
individuals and shall be available for inspection by the Secretary of
Labor or his authorized agents.
(2) For other than uranium mines and for surface workers in all
mines, paragraph (c)(1) of this section will be applicable: Provided,
however, That if no environmental sample shows a concentration greater
than 0.33 working level in any occupied part of the mine, the
maintenance of individual occupancy records and the calculation of
individual exposures will not be required.
(d)(1) At the request of an employee (or former employee) a report
of the employee's exposure to radiation as shown in records maintained
by the employer pursuant to paragraph (c) of this section, shall be
furnished to him. The report shall be in writing and contain the
following statement:
This report is furnished to you under the provisions of the U.S.
Department of Labor, Radiation Safety and Health Standards (41 CFR 50-
204.36). You should preserve this report for future reference.
(2) The former employee's request should include appropriate
identifying data, such as social security number and dates and locations
of employment.
