Document DDJJ71ok8jDOgqeYoYJJob4ga

have on the overall level of lead In urban air one can examine separately the three possible avenues by which lead from gasoline can reach the air and compare the effects of the two compounds: 1. Particulate Lead in Exhaust Gas -<* liegardless of its form organic lead in gasoline is burned during combustion to the same inorganic products. Therefore it can be seen that the nature of the lead alkyl used will not influence the amount or ch aracter of the exhaust products if the same concentration of lead is present in the fuel. 2, Organic Lead From Spilled Gasoline -- The volatility of different organic lead compounds will affect the relative rates at which gasoline and its contained organic lead compound will evaporate. How ever In the case of gasoline spills th ese different evaporation rates will not affect the total amount of Fb ultimately tran sferred to the air since all of the gasoline and all of the contained lead compounds will eventually v ap o r ise . 3. Vapor Losses During Fuel Handling and Tran sfer -- In this type of situation such as with vapors displaced daring tank fillings an in crease in the volatility of the organic lead compound will In crease the amount of lead which reach es the air . However even in the case where fuel vapors are displaced during automobile tank filling* studies have shown that an appreciable part of the hydrocarbon is lost in droplet form in which case lead compound volatility would have no effect on the ulti mate quantity of Pb vaporised. Nevertheless if one con siders the losses to be entirely vapor* an examination of the quantities involved indicates that this in creased amount of lead is likely to have little overall sign ifi cance. Th is is because* even with TML a large portion of the light fraction s of a gasoline must have evaporated before an appreciable D r. K. A . Kehoe 2 ** Ja n u ary 5 I 960 fraction of the contained TML. has vaporised. For example, daring the vaporisation of the fir st 10% of a gasoline* only approximately 3% of the contained TML. vaporises. This is a conservative value based on distilla tion conditions* in which the relative amount of lead vaporized is greater than under conditions of air evaporation. We can estimate the quantities of Pb which would be involved in vapor lo sse s by making use of data compiled and distributed by the Los Angeles Air Pollution Control District. According to data released in July* 1959* 5.329*000 gallons of gasoline were consumed daily in Los Angeles. The hydrocarbon lo sse s chargeable to marketing operations were estimated at 90 tons per day* which represented 0.5% of the gasoline used, if we assum e this to be entirely vapor loss* in which case differences in lead alkyl volatility would have the greatest effect* the overall lead vaporiza tion could be estimated as follows: The fir st 0 .5% of a gasoline to vaporize would carry with it no more than 0.15% of the contained TML. b. The 5820. OO0 gallons of gasoline consumed per day would contain 33 900 lb. Pb (based on the equivalent of an average 2.8 ml TEL per gallon). 1 ^ c. 0.15% of the 33. 900 lb. Pb would represen t a loss of only v 51 lb. Pb. as compared to the simultaneous loss of 90 . ><:. . JL 0: ' tons or iS0. 000 lb, of gasoline. *" On the b asis of thee considerations* a change from TEL to TML could not m aterially affect the overall lead level of a community. The in crease . \ could, therefore* not exceed a fraction of 1%. Furth ermore, since TEL ' ,Jand TML both are compounds which are readily decomposed by sunlight. . it is unlikely that vapors of either compound could per sist for long in the at m osph er e. A comparison of the physical properties of TEL and TML follows: TEL For m u la (0 2H5)4Pi> Molecular Wt. 323.45 Percent Pb 64. 06 Density at 20* C 1*652 Vapor P r essu r e, JaftHg. 20' c 0. 25 60''C 4.0 100'>c 32 TML (CH3)4P& 267.35 77.51 1.995 26 155 560 0003013