-~ 25 -
and in Water for Occupational Exposure."
The meaning of a
maximum permissible value is explained by Dunham (1959) in
the following statement:
In a sense a maximum permissible value is similar
to a speed limit.
A speed equal to the speed
limit is not an absolutely safe speed since many
serious accidents occur at lower speeds.
it extremely dangerous
Nor is
to drive at Speeds somewhat
greater than the speed limit.
Neither a recom-
mended maximum permissible dose nor a speed limit
has any particular significance beyond marking the
point at which an advisory group has agreed to draw
the line in recommending a maximum degree of hazard
appropriate under a given set of circumstances.
There are two types of maximum permissible values,
dose and concentration.
The maximum permissible dose is a
limit for exposure to external emitters,
mended value is 0.3 rems per week.
and the recom-
The maximum permissible
concentration (MPC) is a limit for the concentration of
radioisotopes in critical organs of the body.
‘The MPC
values for 240 radioisotopes are given in Handbook 69.