# Ov er view of Final MA TSAppr opria te and Necessary (A & N) Finding Nov ember 1, 2011

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# Structur e of A & N Finding
• Introduction (will be added, not in the curr en t in te ra ge ncy re view dr aft) • Summary of A &N finding as r eported in the pr eamble t o the pr oposed rule • Pe er r eview of national - scale Hg risk analy sis (Hg Risk TSD) • Re visions to the Hg Risk TSD and r esults • Pe er r eview of the nickel and chr omium risk c ase s tudies • Re visions to the non - Hg HAP inhalation risk c ase s tudies and r esults • Re sponse to public commen ts • Af firmation of the A & N finding
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## Summary of A &N Finding: It is appr opriat e to r egulat e Haz ar dous Air P ollut an ts

(HAP) fr om U .S. E GUs • Hg and non - Hg HAP emissions ar e haz ar dous to public health, and U .S. EGU emissions cause and/or contribute to these haz ar ds • Hg and some non - Hg HAP ar e haz ar dous to the en vironment • U. S. EGUs are the largest domestic source of Hg , HCl , and HF emissions in the U .S., and a significant sour ce of other HAP emissions • Hg emissions from individual EGUs causes e xc ess local deposition dir ectly Hg emissions om individual EGUs causes e local deposition dir around the EGU that w ould not be r educed by r egional emission re ductions, r equiring contr ols at all U .S. EGU sources that emit Hg • Hg emissions from EGUs contribute to future risk because Hg is persistent in the en vironment , and Hg can be r e - emitted from pr evious deposition • Dela ying re gula tion alr eady r esulted in hundr eds of additional tons of Hg being emitted to the en vironment • Ef fe ctiv e controls for Hg and non - Hg HAP ar e a va ilable fo r U .S. EGU sour ces 3

## Summary of A &N Finding It is necessary t o r egulat e HAP fr om U .S. E GUs • Hg emissions from EGUs remaining in 2016 s till pose a haz ar d to public health and the en vironment in the absence of r egula tions under Section 112 tha t w ould be r equir ed to be implemented attha t time • U. S. EGU emissions of Hg after imposition of the r equir ements of the CAA ar e project ed to be 29 tons per year in 2016, the same as the lev el of Hg emitted toda y • EGUs are the largest source of Hg in the U .S. and thus contribute to the risk associated with e xposur e t o MeHg • EGUs are the largest source of Hg in the U .S. and thus contribute to the risk associated with e xposur e t o MeHg • We cannot be certain that the identified cancer risks att ributable to EGUs will be addr essed thr ough imposition of the r equir ements of the CAA, • The en vironmental haz ar ds posed by acidification will not be fully addr essed through imposition of the CAA • Re gula tion under section 112 is the only w ayto ensure that HAP emissions re ductions that ha ve been achiev ed since 2005 re main permanent • Dir ect control of Hg emissions affecting U .S. deposition is only possible thr ough re gula tion of U .S. emissions; we are unable to contr ol global emissions dir ectly 4

## Risk R esults Supporting the A & N Finding as

Pr esen te d in the Pr oposal • National sc ale Hg risk analy sis

– 12% of modeled w atersheds re ceiv e enough Hg from EGU emissions alone to cause a public health haz ar d, ev en without taking into account Hg deposition fr om other sour ces.

– In 22% of modeled w atersheds, Hg fr om EGUs added with Hg from other emission sour ces causes a public health haz ar d, and EGUs ar e re sponsible for a significant amount of that Hg (mor e than 5%).

– In total, up to 28% of modeled U .S . wate rs heds ha ve popula tions that In total, up to 28% of modeled U tions that ar e at risk from Hg emitted by U .S. EGUs • Non - Hg HAP inhalation risk c ase studies

– 4 out of 16 case s tudy EGUs ha ve es timated risks of gr eater than 1 in a million

– Highes t risk for oil - fir ed unit w as 10 in 1 million, driv en by nickel emissions

– Highes t risk for coal - fir ed unit w as 8 in 1 million, driv en by chr omium six emissions

– Non - cancer risks were all small, with haz ar d inde x v alues less than 1 5

# Pe er R eview of the Hg Risk TSD • P eer r eview w as conduct ed in accor dance with OMB’ s Final Information Quality Bulletin for P eer Re view • 22 - member SAB peer r eview panel, including members r epr esen ting 16 academic ins titutions, 4s tate h ealth or en vir onmen ta l agencies, 1 fe deral agency

, and 1 utility indus try orga niz at ion • Public meetings held in June, Augus t, and Sept ember

, final lette r issued Sept ember 29 6

# General Findings of the SAB R eview • SAB report was generally supportiv e r eg ar ding the methods and data used:

– SAB concluded that EP A’ s risk assessment wa s an “objective, r easonable, and credible det ermination of the pot ential for a public health haz ar d fr om Hg emitte d fr om U .S. E GUs”

– SAB also “r eg ar ds the design of the risk assessment as suit able for its int ended purpose, to inform decision - making r eg ar ding an ‘appr opriate and necessary finding ’ for r egulation of haz ar dous air pollut ants fr om coal and oil - fir ed E GUs” • The review noted that “ The SAB finds the curr ent dr aft document deficient, however

, because of its lack of tr anspar ency in describing key analytical methods and findings.” Thus, SAB support is contingent on significant revisions to the TSD to impr ove the clarity and pr esentation of methods, results, and uncertainties • Thr ee general themes of r ecommendations were

– Impr ove clarity of TSD in t erms of methods and pr esent ation of r esults

– Expand discussion of sour ces of variability and uncert ainty

– De - emphasiz e IQ loss as an endpoint in the TSD 7

# Re sponse t o SAB R ecommenda tions • Re vised TSD addresses all of the rec ommendations fr om the SAB • Major responses:

– Impr oved over all clarity and compr ehensiv eness of the TSD

– Clarified focus on w atersheds with popula tions potentially at risk

– IQ analysis has been mov ed t o an appendix

– Expanded discussion of fish tissue da ta, and added additional data for ke y states

– Ex amined sensitivity of results to alternativ e fish tissue Hg amined sensitivity of results to alternativ fish tissue concentr at ion percentiles

– Expanded discussion of uncertainty r elated to fish consumption r ates

– Included additional information about the number of w atersheds exc luded due to screening criteria fo r source populations

– Enhanced discussion of assumption of linear r elationship between changes in Hg deposition and changes in fish tissue Hg concentr at ions atthe w atershed level

– Expanded tables of sour ces of v ariability and uncertainty 8

# Re vised Hg TSD Risk R esults • Re visions to quan tit ative r esults r eflect 3 r ec ommendations fr om the SAB:

– Added 824 additional waters heds based on fish tissue Hg sample dat a obt ained fr om s tate s and the National Listing of Fish Advisories, for a t ot al of 3,141 wat ersheds, a 33% increase

– Applied a 0.95 adjustment fact or t o acc oun t for the fraction of to ta l fish Hg that is MeHg

– Included all water sheds with fish samples that meet the filt ering crit eria in representing pot en tial risk s for high fish c onsuming – Included all water sheds with fish samples that meet the filt ering crit eria in representing pot en tial risk s for high fish c onsuming fe male populations 

### • 99 th 

### per cen tile c onsumption rate : number of watersheds with populations poten tially at risk incr eased fr om 672 to 917 (36%). P er cen t of watersheds incr eased fr om 28 to 29%. • 95 th 

### per cen tile c onsumption rate : P er cen t of watersheds with populations poten tially at risk incr eased fr om 22 to 24%. 9

# Re vised Hg TSD Sensitivity Analy ses (comparisons with r evised primary r esults) • Excluding s tate s with the pot en tial fo r his to ric al loadings of Hg fr om non - air sour ces re sult ed in an incr ease in the per cen t of w ate rs heds with populations pot en tially at risk from 29 t o 33 per cen t • Including only w ate rs heds in the t op 25 th 

### per cen tile of U. S. E GU deposition r esult ed in an incr ease in the GU deposition r in an incr ease in the per cen t of w ate rs heds with populations pot en tially at risk from 29 t o 30 per cen t • Using the 50 th 

### ins te ad of the 75 th 

### per cen tile of fish tissue Hg c oncen trations at each w ate rs hed re sult ed in a decr ease in the per cen t of w ate rs heds with populations pot en tially at risk from 29 t o 26 per cen t 10

## Pe er Re view of Appr oach for Es timating Nickel

and Chr omium Cancer Risk s • Pe er r eview focused on appr oaches and r ationale t o derive inhalation ca ncer risk s fr om chr omium and nickel fr om E GUs • Lette r peer - review pr ocess, 3 independen t e xt ernal peer r eviewers representing government, ac ademic, and priv ate sectors • Re viewers c ommen ts on chr omium

– consider ed he xava lent chr omium as the species likely to be driving cancer risks consider ed he xava lent chr omium as the species likely to be driving cancer risks

– EP A’ s use of a ve ra ge of r ange of speciation data as reasonable when no specific specia tion da ta

– Agr eed that there is high uncertainty associated with v ariability in the speciation data a va ilable for chromium • Re viewer co mmen ts on nickel

– Agr eed that nickel compounds ar e car cinogenic as a group

– One reviewer recommended evaluation of additional speciation liter at ur e tha t sug gests low levels of sulfidic nickel emitted from EGUs 11

# Re sponse t o Chr omium and Nickel

Pe er R eview • EP A r eviewed additional s tudies on chr omium speciation and determined that mor e r ecen t speciation dat a is unlikely to reduce uncert ain ty of chr omium speciation, and that co nfidence in default speciation pr ofiles is low • EP A tr ea ts all nickel c ompounds as car cinogenic as a gr oup

– EP A decided t o use 100 per cent of the curr en t IRIS URE fo r A decided t o use 100 per of the curr t IRIS URE nickel subsulfide , rather than assuming that 65 per cent of the to ta l mass of emitte d nickel migh t be nickel subsulfide , as used in previous analyses

– EP A also c onsider s it reasonable t o use a v alue that is 50 per cent of the IRIS URE fo r nickel subsulfide fo r pr oviding an estimate of the lower end of a plausible r ang e of c ancer pot ency v alues for different mixtures of nickel c ompounds
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# Re vised Non - Hg Case Study Re sults • EP A also received public c ommen ts on the non - Hg c ase s tudies, including a risk assessmen t pr epared by EPRI • In response t o the peer r eview and public c ommen ts revisions were made t o the emissions estimat es, disper sion modeling, and risk charact eriz ation

– Keyc hanges include changes in emissions, changes in s tack par ameters for some facilities, use of updated v ersions of the dispersion model, and use of 100 per cent of the IRIS URE for nickel sion model, and use of 100 cent of the IRIS URE for nick subsulfide • Number of c ase study facilities with c ancer risk s gr eater than 1 in 1 million increased fr om 4 t o 6 out of 16 c ase study facilities

– 4 of the 6 were coal - fir ed units

– 2 case s tudies had risks driv en by oil - fir ed units • Highest c ancer risk for the oil - fired facility increased fr om 10 t o 20 in a million, driven by nickel emissions • Highest c ancer risk for the c oal - fired facilities decreased fr om 8 t o 5 in a million, driven by he xava len t chr omium emissions 13

# Re sponse to Commen ts • Re ceiv ed co mmen ts on leg al, t echnical, and policy aspects of the A &N finding • Orga niz ation of section:

– Commen ts on leg al aspects of the finding

– Commen ts on t echnical analy ses

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# Commen t Ca te go ries for Leg al Aspects
• His to ry of Section 112(n)(1)(a) • Definition of t erms “ appr opriat e” and “necessary ” • Re gulation of all HAP • Consideration of health and en vironmen ta l effects Consideration of c os ts • Consider • Consideration of CAA r equir emen ts in making necessary finding • Lis ting of U .S. EG U under Section 112 • The 2000 finding
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## Commen t Cat egories fo r T echnic al and P olicy Aspects • Modeling of Hg emissions – global and U .S. • Hg deposition modeling and analysis of e xc ess loc al deposition • Hg risk analysis

– Assumed linear r elationship between changes in Hg deposition and fish tissue Hg concentr at ions

– Fish consumption r ates and fish tissue Hg concentr at ions

– Cooking loss adjus tment fact or

– Beha vior of subsis tence fishing populations

– Fish consumption r ates

– MeHg refer ence dose and Hg health effects s tudies • Non - Hg HAP inhalation c ancer risk c ase s tudies

– Non - Hg HAP emissions

– Nickel and chr omium risk

– Alternative analysis of risk by EPRI • Eco syste m impacts relat ed t o acid g ases, e.g. HCl 16

# Af

firma tion of the A & N Finding • Hg

– The per cent of modeled w atersheds with populations pot entially at risk has incr eased fr om 28 to 29 per cent in the r evised risk assessment, and

– The r evised analysis includes 36 per cent mor e w atersheds covering a much larger part of the U .S.

– We conclude that the finding that emissions of Hg fr om U .S. E GUs ar e a haz ar d to public health is affirmed by the r evised risk analysis • Non - Hg HAP

– The lifetime cancer risk for the oil - fir ed E GU facility has incr eased fr om 10 to 20 in a million

– The number of coal - fir ed E GU facilities with cancer risks gr eat er than one in a million has incr eased fr om thr ee to five

– The highest risk coal - fir ed facility still has cancer risks of five in a million, which is gr eat er than the one in a million benchmark

– We conclude that the finding that emissions of non - Hg HAP fr om U .S. E GUs ar e a haz ar d to public health is affirmed by the r evised case studies • These r evised analyses, along with the other unchanged elements of the finding from the pr oposal, lead EP A to affirm its finding that it r emains appr opriate and necessary to regulate coal - and oil - fir ed EGUs under CAA section 112, and the inclusion of coal - and oil - fir ed E GUs on the section 112(c) list of source categories regulated under CAA section 112. 17