r
reasonable values for these factors and the various weekly
doses into the formula, we get:
P = 0-8 [0:60 + (0-2) (0-37) +- (0-3) (1:18) + In]
+ 0-2 (0-60 + 0-37 4+ 1-18] = 1-25 + 0-8 I, mr./woek
Since we have determined that the indoor total y-levels
average 0-7 of the outdoor levels in these areas, we find
that:
Tk20-5 17, + 0-4/7, = 0-66 mr./week
Substituting this in the above expression for P, we get:
P = 1-8 mr./week
This result is not strongly dependent on the particular
2
mr./week (HAST)
ion expos ure
estimates ag g fi
Yy Laborat
funcforth
ti
e comSL) est4imates
England aren{HA
€ eig
eXa
ht
mined
Ste hs
is cele
:
doubt
one that the
dosimet er
nalysis of the
varrious
contri
.
us conte
aye
Tl
» P, utilizi
als,
we
butions
Y Sources
“anN write the followjng
Sadn + Ln) + Sto (I
e+ Ly + Ty)
ney time fa
ctors
heivel
‘t
1
y,2
and $Y 4ndfor indoor and
$s, aro
w
e vanes an
d residences
f
ion,
e
§ ubstit
itut
utiing
values assumed for the various factors in the above
equation.
It is quite consistent with the similarly
calculated Health and Safety Laboratory population
exposure estimates, and much lower than the dosimeter
results. The mean contribution from building materials
to population exposure would have to be close to 2 mr./
week to validate the dosimeter data, which is considerably
higher than the measured values for the total indoor
y-dose rate in most of the 160 residences wherescintillation
detector readings were made. Even without such evidence,
it seems to be an unreasonably high value to assign to
mean, regional indoor radiation-levels produced by radioactivity in building materials. For it implies total indoor
y-doses averaging approximately 3 mr./week, whereas thé
scattered data given in the 1962 United Nations report}*®
indicate that readings of 1 mr./week are typical of normal
situations in wood or brick houses.
Tho results of both surveys indicate that the range of
population exposure to environmental radiation is quite
narrow throughout the regions studied. It follows that
northern New England does not provide a good ‘laboratory’ for the study of the effect on large human populations
of differences in long-term environmental radiation
exposure. Of much greater significance is the correlation
between the two entirely independent and undoubtedly
somewhat imprecise techniques for estimating these
exposure-levels. This correlation can be at least partially —
understood as a consequence of the relatively high degree
of uniformity in radiation-levels observed within each
area. Under such fortunate conditions, the method of using
a fow hundred field measurements to infer the total radiation profile has yielded apparently realistic values for
population exposure, for which the Harvard dosimeter
data provide strong qualitative support. Spiers e¢ al.?, in
their discussion of the extensive population investigation
in Scotland, have already indicated some of the difficulties
involved in obtaining and interpreting data of this type.
But it can be concluded from the work recorded here that
9