Document 4JkrY1QXZmEKLo6MKooRoaQJa

M edicai Research Division Esso Re se a r ch a n d En g i n e e r i n g Co m p a n y DATE: b/ k/ 60 REPORT: MRD-8-60 MR.8M.60 MEMORANDUM 0N COMPARISON BETWEEN AIR POLLUTION LEVELS CAUSED BY CARS OPERATING ON TML AND TEL GASOLINES COMPANY CONFIDENTIAL 1. Summary As part of the over-all evaluation of tetramethyl lead antiknock additive (TML), the lead content of the air around foreign-make cars operating on tvo fuels containing identical quantities of lead as TML or TEL was studied. This was an exploratory air pollution evaluation done during the period February through March i960. The data vere obtained simultaneously on the same makes and models of cars during the same driving cycle. This permitted a direct comparison between TML- and TEL-induced lead contamination in the air. Statistical treatment of the data showed no significant difference between the atmospheric lead levels obtained from either TML- or TEL-containing gasoline. II. General Discussion Both inorganic and organic lead compounds have a high order of toxicity. The recommended MAC for lead in air is 0.2 mg/cu.m., with no distinction made between inorganic and organic lead. To evaluate any incremental lead exposures created by the more volatile TML, as compared with TEL, a sampling program was set up in conjunction with the Products Research Division durability tests on the TML antiknock additive. The following were sampled: (l) exhaust gases, (2) air directly above the engine with the hood closed, (3 ) in-car air at the driver's seat at breath ing zone height, and ( h ) air in the general area, four feet behind the car at breathing zone height. Four pairs of foreign cars were used in the test. These are listed in Table 1. .-s4; r ' 1 r - 2- Table 1 Make Model Engine Location English Ford Volksvagen Renault Fiat Anglia Sedan Dauphine 1200 front rear rear front The cars were operated on the MAD units at the Esso Research Center in accordance with a schedule developed by the Products Research Division (see memo dated 1/11/60, P. J. Clarke to G. S. Tobias, Products Research File 3797, Ref. No. 6012836). A. Sampling Procedure The sampler was designed to separate organic from inorganic lead, thus permitting the determination of both forms of lead in the air sampled. This equipment is shown in Figure 1. Figure 1 SAMPLING EQUIMENT USED - 3- The sampling scheme is simply to meter the total flow with some suit able device, like the rotameter shown. The particulate matter in the air, containing inorganic lead, is filtered on molecular sieve filter paper in a filter holder assembly. The air then bubbles through a collecting solution in an impinger designed for a maximum flow of 1^ liters per minute. This impinger contains a solution of KI-I2 which is a highly efficient medium for capturing organic lead vapor. The air stream is then passed through glasswool and activated charcoal in separate traps to protect the pump from the corrosive effects of iodine vapor carryover. In practice, when sampling the exhaust gases, condensation in the rotameter made accurate flow measurement difficult. In its place, a 10 liter per minute critical nozzle was placed between the collection devices and the pump. Sample times were varied from ten minutes to over two hours, primarily to collect enough organic lead for accurate analysis. For high flow rates, or where condensation is not a problem, the rotameter is more desirable than the critical orifice, mainly because of its lower pressure loss. The exhaust samples were obtained from stacks located near the cars. The exhaust from each car was directed into an oversized flexible duct which was connected to the base of a stack. Lead contents found in the stack may not truly represent lead concentration in the exhaust gas because of deposition and dilution in the connecting system, but they serve as good approximations for the purpose of this study. B. Analytical Procedure Inorganic lead on the filter paper was analyzed by the Analytical Division using the colorimetric method ATC-920.0k2T. Organic lead in the liquid collection medium was analyzed by a color imetric procedure developed by Snyder, et all. III. Observations and Conclusions Samples were taken at random intervals in the routine operating cycle. In Tables 2, 3, and U, adjacent data in the TEL and TML columns, under each sample location heading, were obtained simultaneously - 1+ - Engine Location *Sstimated Engine Location Table 2 ORGANIC LEAD, microg/cu.m Front Rear Exhaust Gas TML TEL 80* 8o 920 1+80 80 60 151+0 1+30 57 670 100 530 530 Air Under Hood TML TEL 27 80 31 21 9 15 27 1+0 31 120 13 27 Breathing Zone Driversi Seat ++' Behind Car TML TEL TML TEL 11 6 k 2 9 /8 93 8 (6 6 \ Table 3 INORGANIC LEAD, microg/cu.m Exhaust Gas TML TEL Front - 1870 1+270 21+00 1720 2670 1+130 6620 Rear 8190 3^0 1+300 3980 1330 3100 Air Under Hood TML TEL 37 8 13 63 20 17 90 18 50 57 Breathing Zone Drivers Seat 1+' Behind Car TML TEL TML TEL 96 6 22 7 / 6 3 \ 35 20 / 12 ll+ f/ 10 6 V \ Engine Location Table 1+ TOTAL LEAD, microg/cu.m Exhaust Gas TML TEL Front 1950 1+350 3320 2200 2750 1+190 8l60 Rear 8620 1+110 U83O 1+037 11+30 3630 Air Under Hood TML TEL 30 87 39 3*+ 15 18 1+7 57 121 138 63 81+ Breathing Zone Drivers Seat 1+' Behind Car TML TEL TML TEL 107 12 26 ll+ / 8 7 1 1+1+ 113 %f 20 22 ) 16 12 1 \ - 5- Comparison of absolute levels obtained within each sub-grouping (e.g., exhaust-front engine) was not possible because of (l) the wide difference in variance between the TML and TEL data within each sub-grouping, and (2) the limited number of data points. It is believed that high levels obtained within each sub-group cannot be discounted in an attempt to normalize the data. Culling of these peaks might lead to erroneous con clusions. Many more test points would be necessary to accurately define the model if in fact this is felt to be necessary. Grouping of all the data for testing as a population of TML or TEL values was then done. The frequency distribution of the aggregate data for both TML and TEL gasolines was highly skewed toward the higher concentrations This is to be expected since no concentration can fall below 0 and much of the data is near this lower limit. On logarithmic frequency distribution plotting paper, the data gave similar S-shaped curves. A plot of the deciles from the S-shaped curves versus the normal deviates at these deciles was the technique used to compare the two distributions. They differed only by about 0.1 standard deviation. With such similarity in the distributions of the aggregate data, it is appropriate to use a non-parametric evaluation of the data. The sampling design and technique employed tended to eliminate car oper ation as a variable because of a fact that samples were taken during identical operating cycles for both cars. With this approach in mind, the best measure of whether or not the TML-fueled cars were producing more air pollution would be a differential analysis of the tables shown above. That is, one should consider the differences between TML-produced values and the TEL levels, and not the absolute values obtained. The composite table below shows these differential levels: Table 5 ____________ DIFFERENTIAL LEAD, microg/cu.m_________ (Lead in Air from TML Fuel Minus that from TEL Fuel) Engine Location __________ Breathing .Zone________ Exhaust Gas_______ Under Hood Drivers Seat 4* Behind Car Org. Inorg. Total Org. Inorg. Total Org. Inorg. Total Org. Inorg. Total Front 0* - 800 - 800 -53 -4 20 140 160 10 -5 -620 -4220 -4840 - 6 3 Rear 373 570 0 4210 2110 1200 4583 -13 3 2680 -89 72 1200 -14 -7 -57 5 5 -3 - 3 -2 -10 -,17 -21 90 15 3 95 12 (-84 1 -) 0 ( 15 -69 _p _0 44 Estimated KB 0003056- - 6- Non-parametric rank and sign tests of the differential lead generated (see Table 5) for organic, inorganic and total lead concentration in the air were done. These tests showed no significant increase in the air pollution caused by TML-leaded gasoline over that from TEL-leaded gasoline. The fact that no significant difference appears between the atmospheric concentrations from TML and TEL gasolines is not surprising in view of the experimental set-up at the MAD units in the Esso Research Center. Hie fuel is piped directly to the cars on the unit eliminating tank-filling loss and possible spillage. Blowby, discharged unburned fuel and carburetor loss are other possible means by which lead can be released into the air. These are not believed to be significant, however, for the reasons given below. As a result, it is to be expected that the lead in the fuel supplied will be exhausted on the basis of lead content in the fuel and not on the lead volatility. In blowby some of the lead in the gasoline dissolves in the crankcase oil. With the more volatile TML more of this lead could escape by subsequent evaporation. Tests done in conjunction with this study by Products Research Division have borne this out. Crankcase oil from TML-fueled cars had lower lead content than oil from TEL-fueled cars. In terms of air pollution, however, the difference in lead discharged should be small. The unburned fuel in the blowby and in the exhaust should approximate the composition of the fuel fed. Carburetor evaporation loss should be small in the foreign cars tested. These cars have small carburetor bowls and at the low ambient temperatures existing during the test program little evaporation should occur. Thus the quantitative lead emissions from cars studied in this program should be practically similar for both TML and TEL fuels. This has been confirmed by the preliminary data collected in the study. In the case of an area where gasoline can evaporate and the vapors can concentrate in the air, like a fueling garage, the higher volatility of the TML gasoline will probably produce higher levels of organic lead in the air. This, in fact, has been proven to be true by Cholak2 in studies in a California garage wherein the taxi fleet using the garage was serviced alternately with the same leaded quantities of TEL and then TML gasolines. The particulate lead concentration remained about the same while the organic lead in the air increased about three times. In conclusion, the general atmosphere should show little or no significant difference in the air pollution levels created by TML versus TEL gasoline. However, occupational exposure should be checked in locations wherein ^ 0003 057 - 7the higher volatility of TML could increase the organic lead concentra tion in air. Such areas and activities would include garages, gasoline storage tank cleaning, gasoline loading racks, service stations, and congested traffic. IV. References 1. Snyder, L. J., Barnes, W. R., Tokos, J. V.: Determination of Lead in Air. Anal. Chem. 20(8):772-776 (August 1 9 ^ T 2. Cholak, J. and Kehoe, R. A . : A Report of an Investigation of the Potential Hazards of Exposures to Lead Associated with the Handling and Use of Gasoline Containing an Anti-knock Fluid in which Tetra methyl Lead is Substituted for Tetraethyl Lead. The Kettering Labor atory, Cincinnati, Ohio (November 10, 1959) Confidential Report. t RICHARD S. BRIEF MEDICAL RESEARCH DIVISION ESSO RESEARCH AND ENGINEERING COMPANY LINDEN, NEW JERSEY 0003058