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7. DISCUSS ION 7.1 Introduction As a res u l t of the C l ean Air Amendment s of 1 9 7 0 , automot ive and rela ted manufac turers - both within and out s id e the Uni t ed S tates - have embarked upon res earch , development , and manufac turing programs d e s i gned to mee t the newly es tab l i shed emi s s ion s tandard s for l ight  duty mo tor vehicles . As ob served in the January 1 9 7 2 report o f this C omm i t tee , it i s unfortunate that the aut omob i l e indus t ry did no t s eri ous ly undertake s uch a program on its own vol i t ion unti l i t was s ub  j ec ted to governmental pres sure . A r e l ative ly mod e s t inves tment , over the pas t d ecade , in deve lopmental programs related to emi s s ion c ontro l c ould have prec luded the c r i s i s that now prevai l s in the indus try and the nat ion . The current crash programs o f the maj or manu fac turers have turned out to be expens ive and , in retros p e c t , not wel l p l anned . Nevertheles s , the almo s t wor ld -wide e f fort to achieve the fed  eral emis s ion s t andards s e t for th e l ight -duty motor vehic l e s in the Uni ted S tates has produc ed a s igni ficant rate of progres s toward meet ing the requirements of the C l ean Air Amendments o f 1 9 7 0 . I t i s the very pace o f that progres s that comp l icates j udgment today concerning the mos t appropriate course o f ac t i on wi th respect to attainment o f the s tandard s required by that law . As d i s c us s ed in ear l i er parts o f thi s repor t , s everal sys tems have b een shown capab le o f attaining emi s s ion c ert i fi cation in 1 9 75 mod e l year cars . Among the s e are the d ie s e l ( d i s cus s ed in S ec t i on 6 . 1 ) and the three sys t ems d i s cus s ed in S ec tion 3 . 2 ( the c onvent i onal eng ine with mod ification and oxidation catalys t , the Wankel with a thermal reac tor , and the carbureted three-valve s trati fied - charge engine) . Whi le continued progres s can be expec ted in d eve lopment o f a l l thes e sys tems , they do not pos s e s s equal ly d e s irab l e charac t eri s t ics . - 1 13 - Digitized byGoogle
S everal control sys tems in ear ly states o f d evelopment have met the 1 9 7 6 s t andard s at low mi leage . S ome o f the s e repres ent fur  ther d evelopment o f sys tems d es igned for c erti fication and manufac ture in mod e l year 1 9 75 . O ther s are relatively new and their u l t imat e manu fac t ure wi l l require energetic commi tment by the indus try to further d evelop approaches that have been purs ued only in smal ler companies and at relat ive ly low leve l s o f effort . One sys t em promi s es t o be ac  ceptab l e in use for the full 5 0 , 000 mi les . Durab i l i ty and other per  formance data are already ava i l ab l e for that sys t em . The fut ure per  formanc e and acceptab i l i ty o f other sys tems - especially tho s e current ly being d eveloped by the princ ipal manufac t urers - remain in doubt . In the fo llowing d i s c us sion , we sha l l briefly compare thos e sys tems that warrant cons ideration for certi fication and produc tion in mod el year 1 97 6 . 7.2 Dual -Cata lys t Sys tem To date , the belated res earch and d eve lopment programs o f the maj or automob i l e manu fac turers have been devo t ed almo s t entirely t o the development and incorpora tion o f s uch minimal modi fications t o the basic spark- igni tion , interna l - combus t ion engine as may be requi red t o achi eve c er t i fication in 1 9 7 5 and 1976 . Thi s s ituation i s a res ult o f t h e shor t t ime between pas s age o f the Ac t and the scheduled d a t e o f i t s enforcement , and t h e des ire o f t h e manufac turers both to protect their inves tment s in the int ernal-comb u s t ion engine and to uti l i ze their vas t experienc e with thi s eng ine . The modi fications mad e t o achieve emis  s ion l eve l s requi red by the 1973 federal s tandard s repres ent j us t such continued development of the convent ional engines of previous years . To achieve the further reduct i ons c a l led for by the 1975 and 19 7 6 s tand ard s , mo s t maj or manufac turers current ly plan to us e cata lys ts in the exhaus t s tream to promote both oxidation o f carbon monox  id e and hydrocarbons and chemical reduct ion o f NO ⢠The CMVE believes X that engines equipped wi th oxidation catalys t s wi l l be abl e t o meet - 1 14 - Digitized byGoogle
the certi fication requirements for model year 1 9 75 . At this t ime , no experimental engine modi f ied to inc lude the dual-catalys t sys tem has exhib ited the durab i lity required to achieve complianc e with the 1 9 7 6 s tandard s . Nevertheles s , a s s uming a cont inuat ion o f the intensity o f the c urrent effort , extrapolation o f the rate o f recent progres s sug ges t s that catalys t s with the durab i l ity required by the 1976 s t and ard s wi l l be developed . But it cannot b e s tated wi th certainty that such d eve lopments wi ll occur in time for 1976 production of automob i les . Al though American manufac turers and o thers evident ly wi l l be ab le to produce catalys t -equipped vehicles capable o f certi fication for the 1975 model year , and even pos s ib ly capable of 1 9 7 6 certi fica tion , comp liance wi th the c ertification procedure , of i t s e l f , may not cons t i tute indication of sati s fac tory p erformance of cataly s t -equipped vehicles in ac tual cus tomer u s e . As d i s cus sed in S ect ion 4 . 2 , the divers e cond i t ions to be undergone by the engine and control systems during 5 0 , 000 mi les o f cus tomer use are far more s trenuous than tho s e undergone during certi ficati on . These more s trenuous cond i t ions may result in s igni ficant damage to a catalys t . In view o f the performance his tory o f catalytic sys tems obs erved to date on experimental vehic l e s , under l aboratory condit ions , there i s concern that there may b e frequent cataly s t fai lure under condit ions o f ac t ual us e we l l b efore a s chedul ed 25 , 000 -mi l e rep lacement . Admi tted ly , there has no t b een actual cus tomer- l ike experience wi th catalyt ic sys t ems that have met the 1975 or 1 9 7 6 certi fication requirement s , and the s e concerns may b e overdrawn . Furthermore , fai l  ure i n s ervic e o f cars properly maintained and used wi ll cal l into operation S e c t ion 207 (c) o f the Ac t , by whi ch the manufacturer can b e forced b y EPA to remedy the deficiency at his own expens e . Obvious ly , this concern would b e re lieved by ei ther the expec ted early develop  ment o f cataly s t s d emons trab ly more rugged and durab l e than tho s e tes ted to date , or by d emons trated s a t i s factory p er fo rmance , in condi tions s imilar to cus tomer use , o f thos e cataly s t s now under inve s tigation . - 1 15 - Digitized byGoogle
Only one manu fac turer has c ommenced such t e s t s with a few cars equipped wi th a s ing le -catalyst system that have me t the 1975 s t andard s . Final j udgment of the ac tual p erformance of such sys t ems mus t awai t experi - ence . 7.3 Al ternative s to the Dual -Catalys t Appr oach In view of the fact that the dual -catalyst approach to a non po l lu t ing aut omob i l e power p l ant may not lead to a t ruly s a t i s fac tory long - term s o lut ion to the environmental prob lem , it i s encouraging to not e that promis ing alternative sys tems are und er int ens ive inves tiga t ion . Al though s ome are only in the earlies t s tages o f development , o thers are more advanc ed and p romi s e to achieve 1 9 75 emi s s ions c ert i  fication when ut i l i zed on sma l l er engines . Thes e inc lud e the carbu reted three-valve s trati fied - charge engine , the mod i fied d i e s e l , and the Wanke l wi th thermal reac tor . Each of these al t ernat ive sy s tems i s des cribed below . 7.3.1 Carbureted Three -Valve S trati fied-Charge Engine Pro totype compac t cars equipped wi th the carbure ted three- valve s t rati fied -charge engine have met the 1 9 75 s t andard s for 5 0 , 000 mi les . Three t e s t s on vehi c l es equipped wi th an advanced version o f this sys tem show average l ow-mi leage emis s i ons o f 0 . 25 grams per mi l e HC , 2 . 5 0 grams per mile CO , and 0 . 43 grams per mi le NO ( see Tab le 3 - 1 1 ) . X Thi s sys t em should be capab le o f certi ficat ion on sma l l cars in time for model year 1976 produc tion , and with an adequate margin of s a fety for each o f the three contaminant s . Thi s approach should a l s o be ap p l i c ab le to larger engines , but s uffic ient experience is not yet avai l  ab le for evaluation . A s ubs tant ial degree o f c onfidence can b e placed in the e s t i  mat i on that the emis s ions per formance o f thi s engine i n use wi l l be qui t e c lo s e to i t s performanc e during c erti fication . The maintenanc e - 116 - Digitized byGoogle
required on the carburet ed s trat i fied - charge engine should b e no greater than that required on a c onventional 1973 engine . In fuel econ omy , thi s engine i s comparab l e with a 1972 engine and much sup erior to a dua l - catalys t - equipped 1 9 7 6 engine . 7.3.2 D ie s e l Engines Emis s ions achieved by a current d i es e l -powered veh i c l e are 0 . 15 , 2 . 5 , and 1 . 65 g /mile for HC , CO , and NO , respec tive ly , and thi s eng ine X i s certi fiab l e for 1975 produc t ion . Further improvement s are pos s i b l e , but much innovative engineering work mus t s t i l l b e done before the d i e s e l can meet the 1 9 7 6 s tandard s . Limited produc t ion of ad equately improved vehic l e s might be pos s ib l e by 1980 . S ince the diesel would provide a s igni ficant fue l economy , even compared with 1 97 2 engines , further d evelopment of the d i e s e l warrant s encouragement . 7.3.3 Wankel Engines As shown in Tabl e 3 - 7 , the Wankel engine with thermal reac tor on a compac t car has met the 1975 s tandard s wi th NO leve l s of about X 1 g /mile for 5 0 , 000 miles , but wi th a fuel penal ty o f about 3 0 percent compared with a 1 9 7 3 equivalent pis ton engine . The use o f EGR and richer carburetion can probab ly fur ther reduce NO level s , but at the X cos t o f even greater fuel consumption , and even so it i s not yet cer- tain that the 1 9 7 6 s tandard for NO can b e achieved . X D urabi lity performanc e o f the Wankel engine with thermal re ac tor on a compac t car has been shown t o be superior to that o f the dual -catalys t sys tem . However , temperatures experienced by the reac  tor during operation in the hand s o f the pub lic should be somewhat higher during c ertain driving mod e s , and d urab i l i ty under such cond i  t ions has n o t been e s tab l ished . - 117 - Digitized byGoogle
7 . 3 .4 Catalytic Sys tems with Feedback Contro l A sys tem with three-way cataly s t and feedback contro l ( s ee S ec ti on 3 . 6 ) promises improvement over the dual -cataly s t system . How ever , adequate durab i l i ty data wi th respec t to b o th the cataly s t and the oxygen s ensor are not avai l ab le to make meaningful es timates o f t h e per formance o f s uch sys t ems ei ther during cert i fication or i n us e . Feedback control o f a dual -cataly s t sys tem would b e expec ted to increas e the l i fe of the catalys t , reduce emis s ions , and s igni fi c ant ly improve fuel economy . At this writ ing , such a sys t em i s not availab l e but may be capab l e of d eve lopment , though p erhap s not in time for produc t i on in quant i ty in 1976 . 7 .4 Interim S tandard s According t o the work s tatement agreed to by the EPA and the National Academy of S ciences , " S hould the Contrac tor conc lud e that the attainment of emi s s ion s t andard s on the s chedule provided by Sec t ion 202 (b) ( l ) of the C lean Air Ac t is not techno logi cal ly feasib l e , the Contractor sha l l specifically det ermine techno l ogical ly feasible interim emi s s ion levels to as s i s t the Admini s trator in exercis ing h i s respons ibi l ities under Sec tion 2 02 (b) (5 ) o f the Act . " However , the cons iderations that mus t enter into the determina tion of optimal tech  no logically feas ib le int erim s tandard s are so comp l ex and carry s o many imp l i cations that , a s exp lained below , i t i s inadvis ab l e and in appropriate for thi s C ommi ttee to recommend a spec i fic set of interim l eve l s at th is t ime . I t i s not yet pos s ib l e to make a definit ive predic tion with respec t to which engine sys t ems wi l l achi eve certi fication for 1 976 . The mo s t likely cand idate i s the carbureted s tratified -charge sys t em on sma ller engine s . I t i s probab le that others , part icularly the dual  catalys t sys tem , wi l l a l s o qualify at that time . I t i s conceivab l e - 118 - Digitized byGoogle
that the proj ec t ed automob i l e product i on for 1976 can be achi eved only by a mix of engines , some certi fiab le and s ome (probab ly larger engines ) no t qui t e cert ifiab l e . However , whi l e i t i s premat ure to j udge the i s sue at thi s time , a rat iona l e may later be requi red for upward ad  j us tment o f one or more of the s t and ards to permit produc tion o f a s uf ficient number of vehic les of var ious s i zes in 1 9 7 6 . Examinat ion o f pos s ib l e int erim s tandard s for the three po l lu tant s i s comp licated by the fact that the t echno logi cal ly fea s ib l e l eve l s o f t h e three po l lutants are int erd ependent . For s everal o f the sys t ems d i s c us s ed , further d ecreas es in NO can be achieved , for exam- x p l e by greater relianc e upon EGR , b ut only by accepting higher l evel s o f CO and HC . Thus , before selection o f a particular s e t o f interim level s as achievab l e , answers wi l l b e required to such que s t ions as : I s i t more important t o reduce NO emi s s ions than CO or HC? Or vice X vers a? Further , compac t cars are capab le o f lower emi s s i ons than are s t andard or large cars wi th s imi lar c ontrol sys t ems , whi le cons uming les s fue l . What emphas i s should be p l aced on s igni ficant ly d i f ferent l eve l s of fuel consumpt ion that are a s s ociated wi th the various c ontro l sys t ems and vehicle s i z es and the sub s tant ial pos s ib le impac t on total petroleum requirement s? The Commi t t ee made no a t t empt to reso lve the s e and re lated ques tions , as j udgment s regard ing these mat t ers were deemed t o b e be yond the scope o f the s t udy commi s s ioned to the Acad emy and d e l ineated by the EPA-Academy contrac t . Thus , at thi s t ime , the Commi t t ee find s i t inadvi sab le t o recommend a speci fic s e t o f int erim s t andard s . 7.5 E f fects of a Delay in Enforcement on Total Automobi l e Emi s s ions To i l lus trate the e f fec t s of various delays in imp lement ing the emis sions s t andard s , should this be found neces sary , a computer mode l was used to calculate total au tomo tive emis s ions in a typical metro pol itan area for the years from 1 9 6 0 to 2000 . Thi s mod e l accounted - 119 - Digitized byGoogle
for fac tors s uch as vehic l e age d i s tribut i on among a l l automob i l e s , the decrea s e in vehic le mi les driven per y ear p er car as veh i c l e age increas es , the pred i c t ed nationwide growth in vehic le popu lation each year , the emis s ion reduc tion achieved through crankcase blowby and evaporative- lo s s contro l , the e f fect o f federal exhaus t - emi s s ion s tan d ard s , and deteriorat ion of emis s ion control s wi th mileage . Vehic l e age d i s tribut ion was t aken from a nat ional average automob i le popula t ion , which is a reasonab l e d i s tribut ion for many large urban areas . Urban driving was a s s umed in the model , and average emis s ions for urban d riving were used . The s e emi s s ions values were obt ained from record s for 1 9 7 2 and older mode l-year cars . Fo r cars bui l t or to b e bui l t a fter the 1972 mode l year , the emis s ions val ues were based on various imp l e mentat ion p lans . Figures 7 . 1 , 7 . 2 , and 7 . 3 show the variations in emi s s ions o f HC , CO , and N O , respec t ively ; the s e curves are norma l i z ed agains t the X max�um for each contaminant . Four cases are repres ented in each set o f curves : 1. S tandard s maintained at the 1 9 7 3 l eve l s ind efini tely . 2. 1975 and 1 9 7 6 s tand ard s impl emented and met on s chedul e . 3. 1975 and 1 9 7 6 s tandard s each d e l ayed one year -  the maximum a l lowab le under the law . 4. 1 9 7 3 s t andard s maintained through 1 9 7 6 model year and 1 9 7 6 s tandard s imp lement ed in 1 9 7 7 mod e l year . The �p l ementation o f emi s s ions contro l s s ince 1 9 6 8 has already caus ed an appreciab le red uc t ion in annu al emi s s ions o f HC and CO , but l i t t l e reduction in NO ⢠Fed eral s t and ard s for mode l year 1 973 cars X cal l for d ecreases o f approximately 80 perc en t for hydrocarbons , - 120 - Digitized byGoogle
F I G U R E 7. 1 E M I SS I O N S O F H Y D ROCA R BO N S B Y AUTOM O B I LES I N U R BAN A R EAS w � <{ a: z 0 c;; (/) � 0.6 w � ..... ::> � N ..... X <{ � � 0.4 0 z 0 Standards maintained at 1 973 levels indefin itely � u <{ 1 973 standards maintained through 1 976 model year a: and 1 976 standards implemented in 1 97 7 model year � 0.2 0 1 975 and 1 976 standards each delayed one year ca· - N. CD a_ o- '< 1 975 and 1 976 standards met on schedule CJ 0 �---------------- � --� L- ----------�-----------------L----------------� 0 1 960 1 970 1 973 1 980 1 990 2000 YEAR � ,...._ rv
F I G U R E 7.2 E M I SS I O N S OF CA R B ON M O N OX I D E B Y AUTO M O B I LES I N U R BAN A R E AS 1 .0 � w 0.8 0: z 0 (/) (/) :E w 0.6 :E Standards maintained at 1 973 ::> levels indefin itely :E 1-' N N X 4: :E 1 973 standards maintained through 1 976 model year LL 0.4 and 1 976 standards implemented in 1 97 7 model year 0 z 0 1 975 and 1 976 standards each delayed one year � (.) 4: 1 975 and 1 976 standards met on schedule 0: LL 0.2 0 <6" ;::+ N. CD Q. rr '< 0 �----------------�--��----------�-------------- �-----------------J C) -- 1 960 1 970 1 973 1 980 1 990 2000 0 YEAR & ,...._ (\)
F I G U R E 7.3 E M I SS I ONS O F O X I D ES O F N I T R O G E N B Y AUTOM OB I L ES I N U R BAN A R EAS 1 .0 w 0.8 1- <{ a: z 0 Standards maintained at 1 973 levels indefin itely (j) (/) � 0. 6 w ..... N � ::> � w X 1 973 standards mai ntained through 1 976 model year <{ and 1 976 standards implemented in 1 977 model year � 0 .4 ( F or N ox . same as delayi ng 1 975 and 1 976 standards one year) u. 0 z 0 1 975 and 1 976 standards met on schedule 1- (.) <{ a: 0. 2 0 u. <6" ;::+ N. CD Q. rr '< C) 0 � -- -- � --------� 7 0--- �L ---- � -------98 0 --------------���--------------� --- 0 1 96- 0 -- 19 � 1 9 73 1 1 990 2� & ,...._ YEAR (\)
70 p ercent for carbon monoxide , and 5 0 percent for oxides of ni trogen , a l l meas ured in relation to the uncontrol led emi s s ions o f pre - 1 9 6 8 vehic les . A s s een i n t h e curves , were 1973 s tandard s t o remain in forc e , tot a l emis s i ons o f hyd rocarbons and carbon monoxide would c ont inue to d e c l ine for s ome years , as would that o f NO ⢠Prepond erant ly , the s e X e f fect s reflect the removal from s ervice o f o lder , uncontro l led , or l e s s -we l l -contro l led automob i les . 7.6 Implementation o f 1975 and 1 9 7 6 S tandard s and Related Matters O f two promis ing cand idates for cert i fication and produc tion in 1 9 75 and 1976 - the d ua l -cataly s t system and the carbureted s trati fied  charge engine - only the former is p lann e d for manufact ure o n a scale commensurat e with expected requirement s in tho s e years . Even if durab l e cataly s t s became availab l e , t h e dual- catalyst sys tem wou ld s ti l l have s everal undes irable charac teri s t ic s , the more important o f which are l i s t ed below . 1. The dual-catalys t sys t em i s expec ted t o have poor fue l economy . Improvement s in fue l economy could be ob tained by the use o f proper feedback contro l mechani sms , but thes e are unl ikely to become ava i l  ab le for produc tion i n 1 9 7 5 o r even 1 9 7 6 . 2. Dua l -catalys t sys t ems wil l have a higher ini t ial cos t , b e more d i fficult to maint ain , and b e les s durab l e . 3. Manufac ture o f vehicles equipped with s ing l e - or dual -catalys t systems in large numbers b e fore sufficient experienc e wi th thes e devi c es under ac tual divers e consumer us e is precarious . - 1 24 - Digitized byGoogle
Independent o f whe ther each car mus t p eriodical ly pa s s inspec tion or whether the manufacturer i s repeatedly comp e l led to exerc i s e the recal l pro vi s ions o f the Ac t ; i f a large frac tion o f a l l cars markedly exceed s t h e emis s ions s t andard s , the entire rat ionale o f thi s pro c edure b ecomes s u spec t . 4. The 1973 c las s vehic l es when convert ed to 1975 - 7 6 systems can be expec t ed t o b e more d i fficult t o s tar t , thus was ting s ome fuel and increas ing emis  s ion o f pol lutant s (al though i t should b e po s s ib l e to mitigate this s i t uat ion b y future technical improvement s ) . The circums tances rec ounted above - the probab l e c erti fi  ab i l i ty o f the carbureted s trat ified -charge engine under both 1 9 7 5 and 1 9 7 6 s t andards b ut i t s relat ively l imi ted p l anned production , particularly in 1975 , and the considerab l e promi s e o f other , a s yet incomp l e tely d eveloped sy s tems - make j udgment c onc erning an op timal national approach to deci s i on conc erning the s cheduled implement ation o f the 1 9 75 / 1976 s tandard s extraord inari ly comp l ex - prec i se ly becaus e the entire res earch and devel opment aspec t o f this s i tuation i s very much in flux and changing rapidly . Some members o f CMVE are c oncerned that s trict enforc ement o f the provi s ions o f the Ac t might , b y forc ing adoption of the contro l sys tem firs t to be d eve l oped and certi fied , d e feat the goal o f the earl ies t po s s ib l e attainment o f comp l ianc e by the mo s t general ly d e s i rab le means . These members o f CMVE b e l i eve that , onc e having embarked upon large- scale product ion of the catalys t -dependent control sys t ems , s everal y ears wou ld elap s e before maj o r manu fac turers would al ter course in favor o f produc ing more general ly satis fac tory vehi c l es . This wou ld happen , i t i s thought , becaus e i t would b e c ons i s t ent wi th - 125 - Digitized byGoogle
the trad i tion of the industry o f s lowly improving t echno logy already in use rather than swi tch to a s i gni ficant ly new and d i f ferent t ech  no logy not yet t ried on a mas s scale . Further , there i s c oncern that exi s t ing market mechani sms would not s uffice to accel erate conversion to a sub s tant ial ly d i fferent techno logy at a pac e cons i s t ent wi th the overal l national interes t . A minori ty view within the CMVE s t ates that : (a) only rigor ous en forcement of the Act wi l l as sure the pace of continued progres s toward the goals o f the Ac t ; (b) by the time 1975 cars are placed in produc t i on , the catalys t s used in catalys t -d ependent sys tems may prove d ecided ly more reli ab l e than are tho s e now availab l e ; ( c ) there is no as surance that the addit ional d evelopment t ime wou ld not s imp ly b e employed b y the maj o r manufacturers for further development o f the p res ent sys tems ; and (d) the p res ence on the market of even a small number o f alt ernat ive control sys tems that are more reliable , cheaper , and accompani ed by a l es s er fue l pena l ty , i f any , would cons t itute an ef fec tive market d evi c e , which , wi thout other intervent ion , would as  s ure changeover by the maj or manu fac turers at an acceptab l e pace , par ticular ly if the recal l provis ions of the Ac t are enforced as warrant ed . The maj ori ty vi ew o f CMVE s ugge s t s that , on balance , i t may b e prudent f o r EPA to c ons ider a delay i n t h e imposition o f 1 975 and 1 9 7 6 s t and ard s , but n o longer than that provided for in the Ac t . I t i s thought that thi s would provide the manu facturers an opportunity t o cons ider and imp l ement alt ernative and , quite pos s ib ly , more generally s a t i s fac t ory techno logies wi th which t o attain the goals o f the Act . In th is vi ew , as shown in S ec tion 7 . 5 , such an ac tion would no t result in an unacceptab l e deceleration in reduc t i on o f aut omotive emi s s ions . In i t s work , CMVE became aware o f a cont inuing cont roversy c onc erning the s tringency o f exi s t ing emis s ion s t and ard s . S trongly held d i f ferenc es of interes t s and views surround a l l the maj or factors that a f fect the s election of aut omotive emis s ion s tandard s : th e - 126 - Digitized by Coogle
health e f fec t s o f ind ividual p o l lutant s , their relat ion to amb ient concentrations , the relat ionship o f total emi s s ions to primary and s e condary amb i ent pollutant l evels , the contribut ion o f automob i l e usage t o t o t a l emi s s ions , and the pos s ib l e relat ive reductions in emis s i ons from s tationary and mob i l e s ources . S ome o f the i s s ues pos ed by the s e consi derations are reso lvabl e only by further s c i ent i  fic res earch ; al l wi l l require the at t ent ion o f o ffi c i a l s concerned with p o l lution control . The s e matt ers are s o complex and import ant that the Commi t t ee s trong ly urges an early and thorough reexamination by Congres s , EPA , and the Ac ademy o f a l l aspec t s o f motor veh i c l e p o l lution s t andard s es tab l ished in the C lean Air Amendments of 1 9 7 0 - - their premi s e s , underlying as s ump t i ons , the goals that were set , and the interp lay among the three pol lutant s d eal t with speci fical ly in the Ac t . In the l ight of the material deve loped in i t s s t udy , CMVE believes that s uch a reexamination wou ld be extremely val uab l e in relating motor vehi c l e emis s ion c ontrol t o the many i s s ues rel evant to a s ound nat i onal environmental pol icy . - 127 - Digitized byGoogle
