Document 4akOXXqgkVzvov03w3aK91OY1

.March "22, 1950 Mr. Gordon P. Larson, Director, Air Pollution Control District, County of Los Angeles, 52l Santa Fe Avenue, Los Angeles 58, California. Lear Mr. Larson; J send you, herewith, a memorandum which is essentially an abbre viated version of a letter which I wrote recently to Mr. P. L. McGill on the subject of the significance of lead and hydrobromic acid in the exhaust gas of automobiles. There is mere to the general problem than is indicated here. For example, the matter of the composition of the exhausts of dieselpowered vehicles is quite different. Our interest has centered, however, in the fate of lead and of carbon monoxide introduced into the atmosphere by automobiles of the more common type, using gasoline, and specifically leaded gasoline,a fuel, and it is only on these chases of the problem that we have much information. The important thing for the investigator in this field to hoar in mind, from the aspect of lead, is that lead in the atmosphere is no new or recent phenomenon, and that the increment due to the use of leaded gasoline in automobiles is difficult to Isolate in view of the several known factors, as well as a number cf others of poorly defined origin, that influence the concentration of lead In the air. Moreover, if one excludes; occupational situations, the quantities of lead absorbed from the air by persons in our general population are small as compared to those unavoidably associated with the intake of lead in she food. It would be well to consider care fully the enormous amount of precise information now available on the normal metabolism of load in the human organism, as well as that derived from the study of persons under the conditions cf occupational exposure to lead, before undertaking to arrive at any very striking conclusions concerning the importance of minute quantities of lc?ad in the atmosphere. 1 : Cordially yours, RAX eJ Enc. Robert A. Kehoe, M. D,