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# OAR Box 1111 Prepped byRyan Dugan



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Preliminar yStaf f Conclusion s an d Recommendation s o nth e Secondar yStandar d Th e availabl e laborator yand fiel d dat a indicat e tha t a t concentra tion s a t o r belo wthos e foun d i ncertai nhig hlea d environments , lea d can : 1 ) affec t certai nplant s (e.g. , inhibitio no f photosynthesis , reduced growth , change s i ncomposition) , microbe s (e.g. , reduce d abundance) , and fis h(e.g. , neurologica l changes) ; an d 2 ) alte r th e compositio no f microbia l communitie s an d inhibi t invertebrat e activit yresultin g i n delaye d decomposition , reduced nutrien t supply , and altere d soi l propertie s (e.g. , lowe r organi c content) . Wit hrespec t t o domesti c animal s and wildlife , a qualitativ e assessmen t o f th e availabl e fiel d studie s an d anima l toxicologica l dat a suggest s tha t animal s ma yb e a s susceptibl e t o th e effect s o f lea d a s humans . Th e availabl e dat a als o rais e concer nabou t th e continuin g accumulatio n o f lea d i nth e soi l reservoi r tha t function s a s a finit e sin k o f undefine d capacity . Du e t o th e persistenc e o f lea d i nth e environment , suc haccumula

tion s ar e expecte d t o continu e a s lon g a s input s excee d outputs . Thus , eve na t relativel ylo wdepositio nrate s lea d coul d affec t th e ecosyste m ove r th e long-term . Th e availabl e dat a ar e limited , however , and d o no t permi t an y definitiv e finding s wit hrespec t t o concentration-respons e function s associate d wit hth e observe d effect s o r provid e clea r quantitativ e relationship s betwee nconcentration s o f lea d i nth e natura l habita t an d biologicall y availabl e lead . Dat a ar e no t availabl e t o determin e quantitativ e relationship s betwee nambien t concentration s o f lea d an d effect s i nth e biot a o f terrestria l and aquati c ecosystems . Thes e limite d dat a d o suggest , however , tha tP. 3

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effect s o f lea d o nthes e ecosystem s ca nb e significant , althoug hpoorl y defined , particularl ywit hrespec t t o thei r long-ter mimplications . Th e effect s o f lea d o necosystem s ar e probabl ymor e closel yrelate d t o th e depositio nand long-ter maccumulatio no f lea d tha nt o curren t ambien t ai r qualit ylevels . Thi s suggest s tha t a secondar ystandar d fo r lea d i nth e for mo f a depositio nrat e ma yb e mor e appropriat e tha non e expresse d a s a nairborn e concentratio nlevel . Suc ha depositio nstandar d i s conceptuall yappealin g becaus e i t coul d b e a mor e effectiv e metho d t o provid e protectio nagains t th e welfar e impact s o f lead . It s applicatio n a t thi s tim e i s constrained , however , b ypractica l consideration s suc ha s th e absenc e o f sufficien t dat a t o develo p appropriat e depositio ntarget s and th e lac k o f reliabl e method s fo r measurin g bot hwe t and dr ydeposition . Althoug hquantitativ e relationship s ar e no t wel l enoug hdevelope d t o specif yth e mos t appropriat e secondar ystandard , th e ke yquestio ni s whethe r th e rang e o f alternativ e ai r qualit ylevel s discusse d i nSectio nVI I woul d provid e adequat e welfar e protection . Whil e thi s questio ncanno t b e answere d definitively , al l bu t on e o f th e ai r qualit ylevel s discusse d i nSectio n VI I woul d likel yreduc e curren t ambien t lea d loading . Thes e reductions , couple d wit hreduction s achieve d b yth e continue d phase-dow no f lea d i n gasolin e (gasolin e consumptio naccount s fo r 85-90 % o f tota l airborn e lea d emissions) , woul d likel ymitigat e th e potentia l risk s o f lead-induce d ecosyste meffect s occurrin g i nmos t area s o f th e country . I nurba ncenters , alon g roadsides , and i nth e immediat e vicinit yo f majo r poin t source s tha t hav e experience d a long-term , historica l accumulatio no f lead , and wher e th e natura l soi l sink s fo r lea d ma yb e approachin g o r hav e exceede d thei r capacit yt o bin d lead , th e mor e sensitiv e component s o f th e ecosyste m (e.g. , soi l microbes ) ma yremai na t som e ris k tha t i s difficul t t o quantif yP. 4

a t present . Th e leve l o f th e primar ystandar d chose nfro mai r qualit y range s discusse d i nSectio nVI I could , however , provid e adequat e protectio n fro mambient-relate d exposure s fo r most , i f no t al l mammal s bot hdomesti c an d wild . Therefore , give nth e availabl e dat a alon g wit hthei r majo r uncertainties , th e staf f recommend s tha t consideratio nb e give nt o makin g th e secondar ystandar d equivalen t t o th e primar ystandar d i nal l respects .