Document ID: EPA-HQ-OAR-2008-0253-0155
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2008-07-01T04:00Z

Memo to the Lead RIA Docket: Supplemental IQ Gain Calculations Using Two
Additional Concentration-Response Functions

In this memo we calculate changes in IQ decrements using two alternative
concentration-response functions that are found in table 5-4 of the Lead
RIA:

Lanphear et al. 2005 Log-Linear with low-exposure linearization (LLL),
based on concurrent blood lead metric

The median value of the slopes of the “set of studies with shallower
slopes”

For each standard alternative considered in Chapter 5 of the RIA, we use
the above functions to calculate changes in IQ gains and the associated
monetized benefits. Tables 1 and 2 present results using each function.
Figure 1 compares the estimated change in IQ points using these two
functions above as well as the log-linear Lanphear et al. 2005 function
based on lifetime blood lead (see page 5-24). 

Table 1. Number of IQ points gained and Monetary Benefits (in Millions
of 2006$) in 2020: Lanphear et al. 2005 LLL (based on concurrent blood
lead metric)

Standard Alternative	IQ Points Gained	Estimated Net Present Value of IQ
Points Gained*

3% Discount Rate	7% Discount Rate

0.5 Second Maximum Monthly Mean	97,000	$850--$1,200	$110--$210

0.3 Second Maximum Monthly Mean	180,000	$1,600--$2,200	$190--$380

0.2 Second Maximum Monthly Mean	250,000	$2,200--$3,200	$270--$540

0.1 Second Maximum Monthly Mean	390,000	$3,500--$4,900	$430--$850

0.05 Second Maximum Monthly Mean	620,000	$5,400--$7,700	$680--$1,300

*Lower end of range calculated using Schwartz (1994b) estimate; upper
end calculated using Salkever (1995) estimate.

** Results reflect the use a 2002 derived non-air background blood lead
applied to analysis year of 2020. To the extent that state and federal
interventions such as the Renovation and Repair Rule (EPA, 2008c) reduce
future non-air blood lead levels, the estimate of IQ change above may be
overstated. 



Table 2. Number of IQ points gained and Monetary Benefits (in Millions
of 2006$) in 2020: The median value of the slopes of the “set of
studies with shallower slopes”

Standard Alternative	IQ Points Gained	Estimated Net Present Value of IQ
Points Gained*

3% Discount Rate	7% Discount Rate

0.5 Second Maximum Monthly Mean	150,000	$1,400--$1,900	$170--$330

0.3 Second Maximum Monthly Mean	220,000	$1,900--$2,700	$240--$470

0.2 Second Maximum Monthly Mean	270,000	$2,400--$3,400	$290--$580

0.1 Second Maximum Monthly Mean	350,000	$3,100--$4,400	$380--$760

0.05 Second Maximum Monthly Mean	460,000	$4,000--$5,800	$500--$990

*Lower end of range calculated using Schwartz (1994b) estimate; upper
end calculated using Salkever (1995) estimate.

** Results reflect the use a 2002 derived non-air background blood lead
applied to analysis year of 2020. To the extent that state and federal
interventions such as the Renovation and Repair Rule (EPA, 2008c) reduce
future non-air blood lead levels, the estimate of IQ change above may be
overstated. 

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