At 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 nephelomcter measure- 1 mg/m°, the public healta problem from ment was 9,2 ug/m>, The the dust alone might be enormous, The greatest amount of date is available for Mauna Loa Observa-~ 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 ug/ m? at night to mass concentrations this high are usually. 6.5 ug/m? during the day, associated with conditions described as measurements made by the USAEC Health dust storms !819. and Safety Laboratory (HASL) were Measurements of ambient air mass Here, the NASN measurement was 3 ug/m?, Additional It is of interest in the present loading can be used to further define a context that Simpson?" made the following reasonable estimate for predictive pur- comment concerning the HASL measure- poses, ments: The National Air Surveillance "The HASL filter samples contain Network (NASN) has reported suchresults substantial dust (3-5 ug/ m° of air sampled) for several years, because of 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 ug/m® (Steubenville, Ohio), with a may not have coincided with Simpson's mean arithmetic average for al} 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 from 9 (White such 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 ug/m® as an average ambient air 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, Islands, and therefore allows room for Hawali, which had an annual arithmetic average of 35 ug/m>. the uncertainty involved because the people More pertinent, but limited, data have themselves may generate a significant fraction of the total aerosol. Hawaii the 1, 22 . locations: Data are given for three Mauna Loa Observatory located at a height of 3400 m, Cape Kumukahi, and the city of Hilo. NASN bee Ca recently been published for the island of Thercfore, . may be GNposed to higher particulate eons sar a to: concentraiions than would be measured by a stationary sampler, Supporting evidence that 100 wim? is data for Hilo (for an unspecified period) a reasonable value to use for predictive are given as 18 ug/ my and nephelometer purposes is provided by the National . , 3 measurements varied from 18 upgim Ambient vir Quality Standards” . Here