"King, Heidi R." <Heidi_R._King@omb.eop.gov> 

04/18/2008 03:00 PM

	

To

Lydia Wegman/RTP/USEPA/US@EPA

cc

Tricia Crabtree/RTP/USEPA/US@EPA, Karen Martin/RTP/USEPA/US@EPA, Zachary
Pekar/RTP/USEPA/US@EPA, Deirdre Murphy/RTP/USEPA/US@EPA

Subject

RE: Description of air-to-blood ratio derivation in the Pb NAAQS Risk
Assessment









Thank you; I will share this to the interagency group

heidi 

-----Original Message-----

From: Wegman.Lydia@epamail.epa.gov [mailto:Wegman.Lydia@epamail.epa.gov]

Sent: Friday, April 18, 2008 3:01 PM

To: King, Heidi R.

Cc: Crabtree.Tricia@epamail.epa.gov; martin.karen@epa.gov;

Pekar.Zachary@epamail.epa.gov; murphy.deirdre@epa.gov

Subject: Fw: Description of air-to-blood ratio derivation in the Pb

NAAQS Risk Assessment

Heidi,

Attached is the information you requested about the discussion of

air-to-blood ratios in the risk assessment.  Please let me know if you

have any questions.

Lydia

----- Forwarded by Lydia Wegman/RTP/USEPA/US on 04/18/2008 02:49 PM

-----

                                                                        

             Zachary                                                    

             Pekar/RTP/USEPA/                                           

             US                                                      To 

                                      Lydia Wegman/RTP/USEPA/US@EPA     

             04/18/2008 11:01                                        cc 

             AM                       Karen Martin/RTP/USEPA/US@EPA,    

                                      Deirdre Murphy/RTP/USEPA/US@EPA   

                                                                Subject 

                                      Description of air-to-blood ratio 

                                      derivation in the Pb NAAQS Risk   

                                      Assessment                        

                                                                        

                                                                        

                                                                        

                                                                        

                                                                        

                                                                        

Lydia - here are the sections of the Risk Assessment document (Volume I

- see link at end of e-mail) that describe the two approaches (and

associated results) that we used to derive air-to-blood ratios based on

the results of blood Pb modeling for the risk analysis. I had promised

to get these to OMB during yesterday's discussion of the RIA so they

could review the two approaches and see if they had any follow-up

questions.

- 3.5.2.2 Evaluation of model-derived outdoor air Pb-to-blood Pb ratios:

this describes the derivation of ratios based on a comparison of the

ambient air Pb levels for a given scenario run and the associated

recent-air related blood Pb estimates

- 5.2.5.2 Performance Evaluation of Modeled Blood Pb Levels: this

section discusses an alternate method for deriving ratios, where we

compare (a) differences in the total blood Pb levels between two

adjacent standard level runs (for the same case study) to (b) the

difference in ambient air Pb levels between these two standards. This

approach is generally more in-line with how ratios are derived in the

literature (i.e., when blood Pb levels for children in to different

locations are compared against differences in ambient air Pb levels for

those two locations).

Here is the link to Volume I of the Risk Assessment Report:

http://www.epa.gov/ttn/naaqs/standards/pb/data/20071101_pb_ra_body.pdf

I hope this is helpful.

zach

Zachary Pekar, Ph.D.

Ambient Standards Group

Office of Air and Radiation, USEPA

(919)541-3704

pekar.zachary@epa.gov

