Lydia Wegman/RTP/USEPA/US 

05/01/2008 09:31 AM

	

To

hking@omb.eop.gov

cc

Tricia Crabtree/RTP/USEPA/US@EPA, Karen Martin/RTP/USEPA/US@EPA, Deirdre
Murphy/RTP/USEPA/US@EPA, Charlotte Bertrand/DC/USEPA/US@EPA, Mike
Clark/DC/USEPA/US@EPA, David Orlin/DC/USEPA/US@EPA

Subject

Fw: Re: air-to-blood ratio section









Heidi, 

 

I talked to Karen about the issues you raised on the air to blood ratio
discussion.  The gist of her response is as follows:

We do not state or infer that it is EPA's view that the science-based
support for a ratio of 1:7 is "equivalently robust" to the science-based
support for any of the other ratios in the range of 1:3 to 1:7.  If
further description of our views on the relative science support for
various ratios is desired, I would say that we have the most confidence
in ratios in the range of 1:4 to 1:6.

Also, as we discussed, we agree with the edits suggested below on point
#2.

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

 From: "King, Heidi R." [Heidi_R._King@omb.eop.gov] 

 Sent: 05/01/2008 12:16 AM AST 

 To: Lydia Wegman; "Fraas, Arthur G." <Arthur_G._Fraas@omb.eop.gov> 

 Cc: Tricia Crabtree; Karen Martin; Robert Meyers; Jason Burnett 

 Subject: RE: air-to-blood ratio section

Lydia,

Thank you for this draft.  Two comments:

1.  We failed to note additional or clarified support for the higher
ratios.  We remain somewhat uncomfortable with characterizing the
science-based support for a ratio of 1:7 as equivalently robust to the
science-based support for standards ranging up to 1:6.  I believe
we’ll pick up the conversation in the morning.

2.  Questions regarding “reanalysis” and “potentially” on p 4:

 

More recently, a study of changes in children’s blood Pb levels
associated with reduced Pb emissions and associated air concentrations
near a Pb smelter in Canada (for children through age six in age)
reports a ratio of 1:6 and reanalysis  << Did the Agency mean to say
additional analysis ??  Our conversation had not left me with the
impression that the Hilts dataset has been reanalyzed by the Agency >>
of the data by EPA for the initial time period of the study resulted in
a ratio of 1:7 (CD, pp. 3-23 to 3-24; Hilts, 2003). [1]   Ambient air
and blood Pb levels associated with the Hilts (2003) study range from
1.1 to 0.03 µg/m 3 , and associated population mean blood Pb levels
range from 11.5 to 4.7 µg/dL, which are lower than levels associated
with the older studies cited in the 1986 Criteria Document (USEPA,
1986). 

Sources of uncertainty  potentially  << The sentence reads well without
“potentially”.  I believe these uncertainties are not potentially
related; they were identified by the author as related >> related to
air-to-blood ratios obtained from Hilts (2003) study have been
identified.  

 

 

Best regards,

 

heidi

 

 

 

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

Sent:  Wednesday, April 30, 2008 11:25 PM 

To:  King, Heidi R.; Fraas, Arthur G. 

Cc:  Crabtree.Tricia@epamail.epa.gov; Martin.Karen@epamail.epa.gov;
Meyers.Robert@epamail.epa.gov; Burnett.Jason@epamail.epa.gov 

Subject:  Fw: air-to-blood ratio section

 

 

-----Forwarded by Lydia Wegman/RTP/USEPA/US on 04/30/2008 11:24PM -----

To: Wegman Lydia@EPA

From: Karen Martin/RTP/USEPA/US

Date: 04/30/2008 10:28PM

Subject: air-to-blood ratio section

Karen Martin, Ph.D.

Office of Air Quality Planning and Standards

U.S. EPA (C504-06)

Research Triangle Park, NC 27711

phone:  (919) 541-5274

fax:  (919) 541-0237

martin.karen@epa.gov 

 

[1]  This study considered changes in ambient air Pb levels and
associated blood Pb levels over a five-year period which included
closure of an older Pb smelter and subsequent opening of a newer
facility in 1997 and a temporary (3 month) shutdown of all smelting
activity in the summer of 2001. The author observed that the
air-to-blood ratio for children in the area over the full period was
approximately 1:6. The author noted limitations in the dataset
associated with exposures in the second time period, after the temporary
shutdown of the facility in 2001, including sampling of a different age
group at that time and a shorter time period (3 months) at these lower
ambient air Pb levels prior to collection of blood Pb levels.
Consequently, EPA calculated an alternate air-to-blood Pb ratio based on
consideration for ambient air Pb and blood Pb reductions in the first
time period (after opening of the new facility in 1997).   

