‘indicate that if the general public were
during the day to 26 ug/m® at night,
exposed to dust levels in excess of
Cape Kumukahi the nephelometer measure-
1 mg/m, the public health problem from
ment was 9, 2 ug/m>,
the dust alone might be enormous,
of data is available for Mauna Loa Observa-
The
At
The greatest amount
reasonableness of the upper limit value
tory.
of 1 mg/m* is also demonstrated by data
3 ug/m°*, and the nephelometer measure-
which indicate that nonurban ambient air
ments varied from 1.7 yug/ m®? at night to
mass concentrations this high are usually,
‘ associated with conditions described as
Here, the NASN measurement was
6.5 yg/m* during the day. Additional
measurements made by the USAEC Health
and Safety Laboratory {HASL) were
dust storms!®?9,
Measurements of ambient air mass
3 ug/m°,
It is of interest in the present
loading can be used to further define a
context that Simpson7* made the following
reasonable estimate for predictive pur-
comment concerning the HASL measure-
poses,
ments: “The HASL filter samples contain
The National Air Surveillance
Network (NASN) has reported suchresults
substantial dust (3-5 ug/ m°? of air sampled)
for several years,
because oi the fact that the filter was
Data”? for 1966 show
that there were 217 urban and 30 nonurban
located less than one meter above the
stations reporting,
ground surface near areas with substantial
The annual arithmetic
average for the urban stations ranged
personnel activity at the observatory site. "
from 33 (St. Petersburg, Florida) to
Thus, while this method of measurement
254 ue/m? (Steubenville, Ohio), witha
may not have coincided with Simpson! s
mean arithmetic average for all 217
interest, it does indicate that ambient
stations of 102 ug/m>,
air mass loadings may be very low on
For the nonurban
stations, the range was irom 9 (White
sucn remote islands even when consider-
Pine County, Nevada) to 79 ug/ m°> (Curry
able human activity is occurring nearby.
’ County, Oregon), with a mean arithmetic
On the basis of the above data, it
average for all 30 stations of 38 ug/ m?>,
would appear reasonable to use a value of
No data in this report are available for
100 pe/m® as an average ambientair
nonurban locations on small islands simi-
mass loading for predictive purposes.
lar to the Enewetak group; perhaps the
Indications are that this value should be
closest analog is the urban station at
quite conservative for the Enewetak
Honolulu, Hawaii, which had an annua!
Islands, and therefore allows room for
arithmetic average of 35 ug/m?,
the uncertainty involved because the people
More pertinent, but limited, data have
recently been pubiisned for the island of
Hawaii’ 1, 22
locations:
Data are given for three
Mauna Loa Observatory
themselves may generate a significant
fraction of the total aerosol.
Therefore,
they may be expusec to higher particulate
concentrations than would be measured by
located at a height of 3400 m, Cape
a stationary sampler,
Kumukahi, andthe city of Hilo,
data for Hilo (for an unspecified period)
Supporting evidence that 100 ug/m" is
a reasonable value to use for predictive
are given as 18 ug/m°>, and nephelometer
purposes is provided by the National
measurements varied from 18 ug; m?
Ambient Air Quality Standards*°,
NASN
114-25
Here