Document 3QaZoe6oRz5m72xb6En2poEME

ETHYL CORPORATION r e s e a r c h a n d d e v e l o pm e n t d e pa r t m e n t r e s e a r c h l a bo r a t o r ie s - iq o o w e s t e ig h t m il e r o a d F E S N D A X E 20. DETROIT, MICHIGAN January 8, 1959 Dr. R. A. Kehoe College of Medicine University of Cincinnati Cincinnati 19, Ohio ' Dear Dr. Kehoe: Enclosed is a translation of a Swiss article, "The Contamination of Air and Dust by Lead from Gasoline From Cars." I came across the abstract and thought it might be of interest; so we obtained a translation. I thought that you might be interested since for the Swiss, in particular, it reads quite favorably on lead. We will continue to scan publications such as this and where they appear of interest will continue forwarding them to you. With best regards, Sincerely yours, HEH:br Enclosure 1. THE CONTAMINATION OF AIR AND DUST BY LEAD FROM GASOLINE FROM CASS, Hans Preiss Automobiltechnlsche Zeitschrlft, vol. 59, ilO, October 1957 pages 3Ql|.-7. The Eidgenoessische Katerialpruefungsanstalt (EHPA) in Zuerich has been assigned to watch contamination of air and dust by lead-containing products 'rom auto gasolines and particularly in such places where large segments of the population are forced to inhale the exhaust of modern traffic and, also, where certain groups of workers are exposed to the possible effect of lead from fuel such as in garages and gas stations. Analogous investi gations were carried out in places In which, beIddofr&aa2L d o f S * d a e , 1she air was expected to have a higher lead content from industrial u#dof lead and Ihs compounds, such as in welding and installation plants, hearths etc suits of the experiments which were started in 19ij-8 and con tinued with interruptions until 1955 will b8 reported subSquint lywi?*.3.- Lead and its compounds is one of the best known industrial poisons. Strict hygienic laws have been passed to protedt workers of plants operating with lead, such as lead works, pigment and battery factories. These deal in , particular with respiration protection since lead containing poisons mostly enter the body through respiratory passages. Since even difficultly vcli- tilized, Inorganic lead compounds and metallic lead'represent a considerable hazard to the operator, how much larger must be the danger of possible poisoning from relatively easily volatizable, organic lead compounds, such as the tetraethyllead which IS added to gasoline as an anti-knock agent (to be referred to in the following as TEL). This concern with respect to high concentrations of TEL Is actually well founded. In the first few years of industrial production of .pur TEL in the USA a number of poisonings occurred, some even with fatal outcome, until the hazard was reduced by improved installations in -those factories and by proper industrial-hygienic measurements. The disquieting results gained at that time where in many places held against lead-containing gasolines and the use of the latter was forbidden legally in some countries. Switzerland was among those countries .and it was only in 191^-7 that the existing ban was counteracted by a special official legislature. This de cision was prompted by the sharply increasing demand for gasoline in the post war period and by the impossibility to -satisfy '-this demand with lead* free gasolines of sufficient high octane rating. . The still present hygienic considerations were counterbalanced by the fact that in some foreign countries, especially in the USA, cars had been .,,perated with leaded gasolines on a large scale for 2 decades without pro ducing indications of increased lead poisonings o-f the population. However, simultaneous with the official admission of leaded gasoline in Switzerland a committee of experts was selected.which investigated among other aspects - the hygienic effect of the us of leaded gasolines in the operation of cars. This committee assigned the experiment carried out by the EMPA. . ' .- _ ^ `F * Lead in gasoline for cars and its Reaction in the,, engine. The trend in the construction of automobile engine/is towards increasing ly higher compression ratios which at the same increases the demands for the knock characteristics of the fuel* Petroleum chemists have stated that owing .p-i-i-' 'M to the enormously Increased amount of gasoline m a g e in the post war period productions of fuel with sufficient knock characteristics would not be adequate without the addition of anti-knock agents, Among the usual anti knock agents, TEL with its specific effectiveness is by far the best. A gasoline base with inadequate knock characteristics is converted into on -'3th sufficient knock rating by TEL additions in amounts of 0,1 to 1$. On ae other hadSa, to obtain equal results with methylaniline, alcohol or benzenehydrocarbons the additions would have to be hundred to thousand times;::.'.as'".iar : TEL is ad d to carbitrator fuels in the form of a component of the so- called ethyl fluids which are a mixture the composition of which has been changed over a period of time. However, in general it consits .of about 6Q to 65$ TEL and of halogen substituted hydrocarbons. The.following is a typical composition of recent times; TEL ethylene dibromide ethylene dichloride dye solution The predominantly poisonous part of the ethyl fluid, the TEL, is a liquid which in the pure form boils at 183C under 760 Torr and which has a vapor pressure of 1 Torr at normal room temperature. Thus, it is considerably lower as, for example, that of water v^por at the same temperature. It is introduced into the combustion chamber of the Otto motor in gaseous form simultaneous with the gasoline vapors and is burnt there in a homogeneous reaction in the gas phase. In the absence of the halo -hydro carbons the lead from TEL is converted to lead oxide and lead sulfate - the latter from simultaneous combustfcdnof the sulfur hf-gasoline - that is, compounds which are not easily volatilised. These would, therefore, deposit in the cylinder and valves and would cause disturbances. . The simultaneous combustion of ha.lq.-hydrocarbons .liberates chlorine and bromine with which a large portion of-the lead, obtained from the'combustion of TEL, reacts to form lead chloride and bromMe. At the -temperature exist ing during the combustion these compounds are volatil dd are expelled from the cylinder. After the exhaust gases have left the combustion char&er they lire quickly cooled below point of volatility and melting point of the lead couapounds c- vfcained in them. While passing through the complicated path : the erhouc- system the reaction products of the lead are partially der- sited zs solid sediments - often mixed with carbon and-oil cotee - on the - 11s of the tube or the' exhaust pipe; another part finds its way into the lubricating oil arid the remainder la pushed to the outside* . The amount of the lead which remains resp. which is thrown into the air depends in the individual case mostly on the type and conditions of the engine and the exhaust system, on the setting of -the carbin*ator and the mode of operation to me talon only a few of the more important factors. The reports in the literature indicate that the lead expelled into the air varies within the wide limits of 15 to &G$ of the amount added to the lead. A scries of experiments carried out on the same engine or car at the hy draulic brr-1 - or on the rolling tester have shown that even under the same external conditions (equal load and mode of operation) considerable scatter ing of the values for the percentage of exhausted lead is found. 3 This is mainly due to the fact that the time interval'at which the samples were taken was relatively short and that the amounts of lead obtained there by were small. For this reason it was impossible to avoid accidental effects, such as the collection of smaller or larger lead containing particles which had separated from the walls of the exhaust system, the presence or absence of which considerably affected the results of a sample. It has been observed, in general, that smaller amounts of the lead added to the gaollne d M e x - iusted into the air during slower and even mode of operations than during ster and higher engine performance, or respectively during frequent braking following by acceleration. In any case, it did not appear as if the direct meg surments of the lead present in the exhaust would produce reliable data concenrning the lead content of the air of a heavily traveled street.. > . It has been reasoned - based on the lead content determinations of the exhaust gas and mal tipLed by the amount of gasoline used in a certain area - that in certain areas tremendous amounts of poisonous lead- compounds are' necessarily accumulated. Thus, it can be approximated that,for example, in a-town like Zurich 20 tons of lead are annually exhausted into the air. It is, however, erroneous to assume that this least necessarily deposits in the area where it is exhausted into the air. 'IShefdudb extent the lead compounds deposit or remain in the layer of air close to the ground depends on the form arid state of distribution of the exhausted par6IpIntiofelaad compounds and on whether, owing to their small sin, they are removed by possible nitussaiesLLr movements from the spot at which they ara exhausted, are distributed, in space and are diluted to harmless concentrations In the air which is inhaled. | Form and state of distribution of lead compounds in the air. If TEL evaporates during the spilling of gasoline (tanking) or if gaso line is carelessly U3ed as a deeming agent then the lead compound attains Immediately''the vapor form, that is the molecular distribution state, in the air. The-TEL vapor thereby acts like a gas and is -dis.tribut^ Jt&ree- dimensionally in the space by diffusion and air movements where^'tha eon centration of lead - assuming an adequate supply of. fresh ai#'-* drops rapidly to harmless values. - To determine the composition, form and sis of the particles of lead compounds obtained by the reaction o^ the TEL in the engine; exhi%st gases eartheneihafesd of under a load on the rolling tester were collected on i&Meiiijger fan electron microscope and were electrone-optlcal^ examined (fig. 1). In this case, the'exhausted particles appear to be ae- i par&ted. The joining of several single particles to form agglomerates was : occasionally observed in other photographs., but It was only rarely con- splcuous. The electrons diffraction diagrams of the dusts, thus separated ! showed lines for lead halides and lead sulfates. The form of* the logger ' duet particles was-polyhedral. This form is also probable for- the jfcller parts which are present in predominant numbers but It cannot be clearly ; recognised cn the pictures owing to the insufficient resolution of the electron microscope which was used (limit of resolution capacity about limit of ^'visibility1 about 2ro whereby Imp. * lQ-o ma). However, these ' 14- particles have similar measurements in all three space directions and differ markedly from occasionally observed soot which appear under the . electron microscope as disc-like fragments of hexagonal plates with mostly much larger measurements, ^ The particle size of the lead compounds is of particular importance. According to the electrone microspope photographs JLbeyangebM1rwm about -00msand the `visibility limit'. On the basis of statistical considerations and in v i e ^ f the performance ability of the electron's microscope it can be concluded that the predominant number of particles have a granule size of considerably less than 20ra|ju. The lpad compounds in question have edge length* qf the unit cell of their crystalline lattice which range from l4-.lj.9 -to 9*if A* their 'molecular diameter ' probably ranges between 2 and 3 A (IO3 lGqi:v The dimensions of the ma,ioriv7 of tfce varfdHis flying dust pai^tlcles rppproximate the order of magnitude of thefc numbers, This extraorfcLnsgr smallness can be explained on the basis cf --he I 0 that the vapor of the lead compounds are quickly quenched from the homogeneous gas phase below the solidification tempera ture, Therefore, only s minimum of time is available for undisturbed crystallization. h A sedimentation velocity of about 2.10saper seeond for particles with a granule diameter of 1 0 0 m a n d of about 1.10"em per second for particles with a granule diameter .of ri|k is calculated from th.e observed particle sizes bTr assuming an average density of the lead compounds in question of 6.Og/cm-. Or, in other words: particles with a granule si*ze of 100my* re quire 0 minutes in absolutely quAet air to drop a distance of lea, particles of require ?bout 10 days. This sedimentation tendency is completely negligible compared tc the much larger air velocities such as caused by winds and heat, currents. That is, the majority of. the lead particles ex hausted into the atmosphere do not settle but are removed from the place of which they are exhausted and are distributed like a.gas in the air and the free space. It is, therefore, nop to be feared that the lead containing dust present in the air would settle at the place of its creation, but in stead.the.largest.part .la.removed into the free atmosphere just as the exhaust from chimneys or the exhaust from unleaded gasolines. Pig. 1. Electron microscope photograph of the flying dust ob tained from the exhaust of a motor operated with leaded'gasoline. How large is then the actual concentration of lead compounds in the air which is breathed in and which is; a result of the contamination by engine exhaust, and & the natural .air replacement? ' ' .! ' . Lead content in the air It was possible to separate the lead containing dust, in spite of its fineness, for test purposes hlmbst:completely by filtration or-in the high voltage field. The same effect can be achieved with TEL vapors if the TEL containing air is passed through an iodine solution. The effectiveness of these separating methods were clarified and verified in extensive tests. The chemical analytical processing of these samples,which even after prolonged sampling contained only microgram or milligram amounts of lead, were carried out according to well established methods of analytical chemist ry and which will net be further discussed here. A few typical examples of test results obtained in the street air of Zurich are shown in Table 1. The air samples were always sucked in for an hours at the head level on the sidewalk (1 mi.cro.gram ( = 10~g). Than sampling was usually repeated oa the same spot in order to eb^Riahb^idcrr b p n t i t i o s i ' t ; t h e e t a r i n g -shieheds,produced bye the^iccifient of-externalr.eohdi-tons. .iair::2S3Tr^aenta,'-weather etc.). Table 1. Lead content of street air of the city (Zurich). Place of sampling Number of cars per hour Lead as flying dust *1/ g per m3 oiTair Square with circular traffic, center-of town n u u n Street with !t slope Street"tunnel* 200 m long, end of tt Streettunnel, 200 m long, middle of Street between tall row of houses expressway without houses 2ij.0 350 60 600 I4.60 1*0 30 620 290 700 60 10 350 1.3 0.6 0.9 1.7 0. 7 1. 6 i*.9 3.5 k3 18.6 0.6 0.6 0.05 Table 2 shows the lead content of the air of some fully operating garags which are completely equipped to service cars including the tanking of gaso line. The samples were again taken at head level. The duration of sampling amounted to 1 to 6 hours. 6 Table 2. Lead content of the air of garages. Garage ' A B Q p 2 P CII ' Lead as flying dust g r^er m3 of air 21h 3 2.7 1.2 9 .2 6 .6 18.8 20.1 7.5 - .. * * c. - * --- Lead as TEL y, g per mJ of air 12.0 3.7 37.0 2.7 5 .o 20.2 3 5 .lp 10.0 To evluate the hazard of the lead content found in the air of the streets and garages it should be noted that the experience of industrial doctors has shov;n that the tolerance limit of the breathing air of industrial plants - assuming a daily exposure of 8 $ours - amounts to 15'0 j^g of lead per m3 of air. Tills limiting content frr chronic lead poisonings has remained un changed for several years and was again confirmed in 1958 by the Conference of American Government Hygienist'-. The values of the ^ir in Zurich's streets and garages are far below the cited, critical limits. Lead content of the sedimented dust. There are always, coarser dusts present on the surface of the street and in the layer of air adjacent to the street which are capable of settling or which have already settled and which are always stirred up again by currents from tragfic. Since the exhaust gases are expelled into this layer of air it could be concluded that a portion of the finer lead particles be comes attached to the larger particleq and could settle with them. The question arises in connection with fchi&i.whether the layers of dust close to the ground would not become enriched in lead in time. " To clarify this.problem, settled dust samples were collected in 19 different spots - and always in these same spots - in the streets and squares of Zurich in larger and smaller time intervals from 1914-3 to 1955. The lead content of these samples' was determined. The lowest single value was 0.10/5, the highest 7.05 of lead in the dust. The course of the average values of lead content as a function of the time is shown graphically in fig. 2. The diagram contains a second, thinner curve (upper) which repre sents the approximated measurement for the momentary expulsion of lead at .the time of the sampling which was calculated as the product from current amount of cars in Zurich and the average lead content of the gasoline; the latter was obtained from the current controls of the Eidgenossische material prufuhgsanstalt. The two curves show remarkable similarities: they have a slope which is in th. firsttperlcwi* quite steep, but later levels out and they also show definite, tdssadne&d variations-. These can b explained on the basis of ' .7 tlie fact that there is lejtss traffic in the winter and partially also as due to the lefLsseas lead content of the winter gasolines (alcohol containing). The general trend reflects the increase of tlio use of gasoline and, there by, tliat of lead exhaust. The following conclusions of decisive importance can be drawn from the similarity of those two curves: number of cars x lead content in the gasoline % lead content car x lead-, content lead content in the street dust. Fig. 2. Change of the average value of lead content of Zurich's street dust with time and also the momentary lead exhaust (the latter a3 the product of the number of cars and the lead content of gasoline). The lead content of the dust of the soil is not increased. If this were the case the curve representing the lead content in the dust would have a much steeper slope than the curve representing the momentary lead exhaust. Apparently, rain, wind, and street cleaning are able to prevent this and a type of equilibrium is formed between the exhausted lead and the amount of lead present in the soil dust. How should the values of the amounts of lead present in the sedimented ; dusts be evaluated with respect to their poisonous effects? Table 3 will serve to assist in the answering of this question; it shows the lead con tent of the Streets of Zurich during the last sampling period in 195$ and also the settled dust from machine shops and ir|istrial workrooms, the latter ' hciiOldlsglat head level excluding the sweepings from the 1 floor. A comparison of the data represented in table 3 shows that the lead 'content of the street dust is much less than the amounts which are found in the dust of welding shops and work shops as & consequence of like hand; ling of lead and without the interference of leaded gasoline. Finally, the lead content of the street dust is roughly one hundroth of the lead con tent of dusts found in plants which are known' to contain lead hazards. If the lead content of the dusts is assumed to have a relative value1with ; respect to the air in the respective placeg then the following conlusions j| could be drawn; with respect to its lead content the air in garages la |i comparable to that of welding and ^akanice workshops, that is to an air G which for generations has been tolerated -withoutT difficulty and which can be considered as harmless. The lead contents of the street air are oven significantly lower. In order to rcoresent an actual lead hazard the average lead-value.-oi\_the garage-.ai* `would have-torhe:.&&;timesas large arid that of the street air about 100 times as large than was indicated by the measurements which were carried out. Table 3. Comparison of lead content in sedimented dust. ilace of sampling dumber of samples % lead in dust highest lowest value valije avaraj value H --J Streets of Zurich work shops I garages 3 lead hearth 19 15 O2/2 7.0 0.7 2.5 120 Ip.O 18.9 73 1.2 16.1 390 195 3m 1. we wish to express our thanks to the Sidgenoessischen Bleibenzin xCoaission for the permission to publish the present atticId. '