Document ID: EPA-HQ-OAR-2008-0253-0171
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2008-07-10T04:00Z

Neal Fann/RTP/USEPA/US 

07/08/2008 10:21 AM

	

To

Heidi_R._King@omb.eop.gov

cc

Ron Evans/RTP/USEPA/US@EPA, Lydia Wegman/RTP/USEPA/US@EPA, Kathy
Kaufman/RTP/USEPA/US@EPA

Subject

Lead RIA benefits analysis

Heidi,

Two weeks ago we walked through the key improvements to the lead
benefits analysis. I think this conversation was very useful in
clarifying what changes to the analysis we were considering. Among those
issues that we discussed, there are two in particular for which I
thought it would be helpful to further detail our approach.

1. Air: Blood ratios.  As you probably recall, in the proposal RIA we
used a range from 1:2 (value from '78 NAAQS) to 1:7 (Hilts). We used the
1:5 ratio (drawn from NPRM and consistent with results from the urban
case study) to generate our central benefits estimate. To the extent
that the Evidence Calculations consider additional, or different,
air:blood ratios, we would make a conforming change to the RIA. 

2. Non-Air blood lead background levels. As we discussed during the call
last week, there are two baselines that affect the benefits analysis.
The first is the level of ambient air lead, which we expect to decline
over time due to a variety of federal and state rules. This reduces the
air quality increment needed to attain alternate standards, which in
turn reduces estimated benefits relative to a baseline using current
ambient lead.  We've reflected this factor in the analysis. The second
baseline is the non-air background blood level. The non-air blood lead
background level determines the portion of the concentration-response
curve over which there is an incremental change in blood lead--this is
clearly important when the concentration-response curve is non-linear
(as the Lanphear LLL is). We've looked into adjusting the background
levels based on the lead renovation and repair rule and do not believe
that the available data would support such a calculation. Moreover, we
illustrate the influence of the level of non-air blood lead background
on our benefits estimates in our sensitivity analysis and find it to be
small. Instead of projecting this value, we will give more prominence to
the sensitivity analysis as a way of highlighting the influence of this
input.

Please let me know if you have any questions or if you'd like to discuss
these issues further.

Thanks,

Neal

_________________________________

Neal Fann

USEPA

Office of Air Quality Planning & Standards

Air Benefit and Cost Group

C439-02

RTP, NC 27711

voice: (919) 541-0209

fax:     (919) 541-0839