"Richard Hornung" <Richard.Hornung@cchmc.org> 

05/01/2007 10:34 AM

	

To

Zachary Pekar/RTP/USEPA/US@EPA

cc

"Bruce Lanphear" <Bruce.Lanphear@cchmc.org>, Jee-Young
Kim/RTP/USEPA/US@EPA, Dennis Kotchmar/RTP/USEPA/US@EPA, Deirdre
Murphy/RTP/USEPA/US@EPA, David Svendsgaard/RTP/USEPA/US@EPA

Subject

Re: Fw: Question regarding the Lanphear et al., 2005 study









Zach

 

The variable that I believe you are referring to is the average blood Pb
from 6 months of age to the last blood Pb measurement before the IQ test
was administered. The minimum value is 1.43 ug/dL, the value that most
closely corresponds to the concurrent blood Pb is 2.0 ug/dL (3 values
are less than this value), while the 1st percentile is 2.5 ug/dL. We did
not produce a plot using this blood Pb index, so we were not concerned
with which lowest value we would use, but any of these 3 values would be
acceptable in a log-linear model.

 

Hope that helps.

 

Rick

 

Professor of Environmental Health

Director, Biostatistics & Data Management Core

Div. of Gen. & Community Pediatrics

CCHMC

3333 Burnet Ave

Mail Location 7035

Cincinnati OH 45229-3039

513-636-1948

Fax: 513-636-4402

>>> <Pekar.Zachary@epamail.epa.gov> 4/26/2007 3:59 PM >>>

Dr. Hornung,

We appreciate your assistance in providing clarification regarding

Figures 3 and 4 of the Lanphear et al 2005 paper.  We are in the process

of placing the information in our docket, and are writing to confirm

that the beginning of the log-linear functions in these figures begin at

1.0 ug/dL, with the reasoning for this being that 1.0 is essentially the

lowest value for concurrent lead index. Although there are 3 or 4

slightly lower values in the entire database (n=1333), the authors

decided that 1.0 was the minimum Pb value that they were comfortable

using with the log-linear model since the intercept goes to infinity as

PB moves toward zero.

In addition, would you identify for us the corresponding value for the

lifetime average blood lead metric (i.e., the lowest measured value in

the Lanphear 2005 study pooled dataset for the lifetime average metric -

the value analogous to the 1.0 ug/dL value provided for the concurrent

metric)?

Thank you,

Zach

Zachary Pekar, Ph.D.

Ambient Standards Group

Office of Air and Radiation, USEPA

(919)541-3704

pekar.zachary@epa.gov

                                                                        

             "Richard                                                   

             Hornung"                                                   

             <Richard.Hornung                                        To 

             @cchmc.org>              David                             

                                      Svendsgaard/RTP/USEPA/US@EPA      

             04/24/2007 05:15                                        cc 

             PM                       Jee-Young Kim/RTP/USEPA/US@EPA,   

                                      Dennis Kotchmar/RTP/USEPA/US@EPA, 

                                      Deirdre Murphy/RTP/USEPA/US@EPA,  

                                      Zachary Pekar/RTP/USEPA/US@EPA    

                                                                Subject 

                                      Re: Fw: Question regarding the    

                                      Lanphear et al., 2005 study       

                                                                        

                                                                        

                                                                        

                                                                        

                                                                        

                                                                        

The plot begins at 1.0 ug/dL since this is essentially the lowest value

for concurrent lead index. There are 3 or 4 slightly lower values in the

entire database (n=1333), but we decided that 1.0 was the minimum Pb

value that we were comfortable using with the log-linear model since the

intercept goes to infinity as PB moves toward zero.

Rick

Professor of Environmental Health

Director, Biostatistics & Data Management Core

Div. of Gen. & Community Pediatrics

CCHMC

3333 Burnet Ave

Mail Location 7035

Cincinnati OH 45229-3039

513-636-1948

Fax: 513-636-4402

>>> <Svendsgaard.David@epamail.epa.gov> 4/23/2007 2:04 PM >>>

Hello Richard,

One of my Colleagues has a question for you.

David J Svendsgaard, PhD

Biostatistician

EPA/ORD/NCEA/RTP, Mail Drop B-243-01

Research Triangle Park, NC 27711

Phone (919) 541-4186

Fax (919) 541-1818

             Zachary

             Pekar/RTP/USEPA/

             US                                                      To

                                      David

             04/17/2007 04:15         Svendsgaard/RTP/USEPA/US@EPA

             PM                                                      cc

                                      Deirdre Murphy/RTP/USEPA/US@EPA,

                                      Jee-Young Kim/RTP/USEPA/US@EPA

                                                                Subject

                                      Question regarding the Lanphear

                                      et al., 2005 study

David,

If you would forward the following question to Dr. Hornung.

Figures 3 and 4 in the Lanphear et. al., 2005 article show the

log-linear function extending down to a blood lead level in the vicinity

of 1 ug/dL. The functions in both figures are not shown to extend below

that blood lead level. I had two questions related to these figures: (a)

what is the specific blood lead level to which the figures extend down

to and (b) what is the conceptual or theoretical basis for using this

specific point of departure in the figures? In looking at the figures, I

thought it might be the lower extent of measured blood lead levels in

the pooled population (~1.0 ug/dL), but I was not sure. Thanks,

zach

Zachary Pekar, Ph.D.

Ambient Standards Group

Office of Air and Radiation, USEPA

(919)541-3704

pekar.zachary@epa.gov

