Document o9LZww83QLb1OE87jwmoGpYeR

f' ! > V ! * , ,, /! V \ ' > | 1 ` NOTES ON THE DETERMINATION OF L3AD IN THE ATMOSPHERE.- \f TBTREBTHYL LEAD. . The following brief'comments are made in relation to the method described in a 7; report from Abadan (Development Report No. 8501). ;::- Despite the preliminary test of the method described in the report, it is be- lieved that the absorption of tetraethyl lead vapour from the atmosphere by means ' of T.Y.O. would be incomplete under the conditions prevailing in the P.O.D. It has been shown that the use of similar solvents (kerosene, mineral oil) for this pur pose is reasonably satisfactory only when the concentration of tetraethyl lead vapounr in the air is quite high, and that the efficiency ,of the absorption drops off sharply .' as the lead concentration in the air diminished. For this reason the use of ahrabsorbing medium which reacts promptly with-tetraethyl lead (one containing bromine or iodine), is recommended as being necessary. The estimation of the lead extracted from the air by the absorbent can be car ried out by anyone of several methods with satisfactory accuracy provided the quan- ; tities of lead to be -dealt with are within the range of the sensitivity of the in dividual method chosen. The analytical error associated with the use of the A.S.T.M. method D 526-39T as outlined in the report from Abadan is appreciable, and can be reduced to practical insignificance only by the collection of a sample that will con tain quantities of lead of the order of several mgms. In general, the quantities of lead dealt with in the report appear to have been sufficient to justify the use of this analytical method. It is believed, however, that the results given in the report tend to err somewhat on the low side. The analytical error would be quite small as compared with that resulting from the use of the spmewhat inefficient method of extracting tetraethyl lead from the air. For the reasons given above, it seems probable that the conditions with respect- to lead exposure in the can-filling section of the P.O.D. were somewhat more severe than the data indicate. This conclusion is especially justified in connection with' , the analytical results given in the Second Interim Report (D.R.No.8620). It seems certain that any type of increased ventilation ivould have reduced the lead concen- . tration (as well as the concentration of petrol vapours) in the atmosphere of the filling section. However, the data in Table 1 (D.R.8620) cannot be relied upon : :f Implicitly for the following reasons:-(l) The air samples were comparatively small; (2) The quantities of lead found Were outside the-range of sensitivity of the anal- ; ytical method; and (3) In all probability the extraction of the tetraethyl lead vapour from the air was incomplete. Moreover, it would seem that there would be significant variations in the lead content of the atmosphere at different times and\ in different parts of the filling section unless the ventilation had been designed in such a manner as to remove 'the,vapors from the building by picking them up at their ,7 point of origin. ... The method for the collection and determination of tetraethyl lead as outlined ; in the memorandum of Dr. Cassells dated 16th July 1943 can be expedited to yield satis factory results. The efficiency of the absorption of t.e.l.from the air is high for even quite low concentration, wnile the analytical procedure is sufficiently accurate for the purpose. ` . Robert A. Kehoe, M.D. October 1943. HE 0010146