Benefits and cost of regulating mercury

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Hi All,

Benefits and cost of regulating mercury levels are discussed.

Science, Vol 310, Issue 5749, 777-779 , 4 November 2005

Costs and Benefits of Regulating Mercury

Dirk Zeller, Booth; Response Ted Gayer, W. Hahn

Letters

Costs and Benefits of Regulating Mercury

Mercury is known to have detrimental effects on human health (1), so it is

surprising to read that it may not be worthwhile to regulate mercury releases

from

U.S. power plants ( " Regulating mercury: what's at stake? " , T. Gayer, R. W. Hahn,

Letters, 8 July, p. 244). Although there is legitimate debate about the cost of

implementation and the choice of emission reduction approach, we feel that the

estimated benefits of emission reduction of $100 million accrued over 15 years

have

been grossly understated by Gayer and Hahn.

Their proposed benefit was based on a study of willingness-to-pay for chelation

therapy to reduce lead in children. However, lowering levels of lead by

chelation

has not been demonstrated to improve cognition (2). Similarly, although

chelation

therapy may remove methyl- and ethylmercury, it cannot reverse central nervous

system damage (3), implying that prenatal mercury exposure leads to lifelong

lost

benefits, irrespective of money spent on removing the causal agent from the body

after the damage has been done.

Thus, an approach based on lifelong losses in income better estimates the

benefits

of reducing mercury emissions (4). This approach attributes subsequent losses in

lifelong earnings as a result of lower IQ to the loss in a child's IQ from

prenatal

methylmercury exposure. The estimated lifelong losses in income for all U.S.

children affected in the year 2000 was $1.3 billion per year (range: $0.1 to

$6.5

billion), which would lead to a $15.9-billion loss in income (range: $1.2 to

$79.9

billion, discounted at a rate of 3% per annum) over the 15-year period

considered by

Gayer and Hahn. Therefore, by only considering the loss of earnings due to

exposure

to mercury generated by U.S. power plants, lowering prenatal exposure by

reducing

emissions may have considerable economic benefits, likely exceeding the

estimated

costs of $4 billion to $19 billion.

Response

In our study, we estimated the costs and benefits of the U.S. Environmental

Protection Agency's (EPA) power plant mercury regulation. To estimate the

benefits

of mercury reduction, we considered each link in the pathway, including the

reduction of emissions from U.S. power plants; reductions in mercury deposition;

reductions of methylmercury in U.S. freshwater and marine fish; reductions of

methylmercury consumption from U.S. fish by U.S. residents; reductions of

methylmercury in U.S. women of childbearing age; and IQ improvements in U.S.

children. For each link, we used the best available evidence and, if anything,

tended to err on the side of overstating benefits. Only at the end did we

monetize

estimates of iQ improvements, based on a study of parental willingness to pay

for IQ

increases through chelation.

Zeller and Booth contend that our estimate of the benefits of mercury reduction

is

" grossly understated " based on their claim that our estimate of the value of an

IQ

point is flawed. They cite a study by Trasande et al. (1) claiming that benefits

of

mercury reduction are $1.3 billion per year. Unfortunately, they are comparing

apples with oranges. The $1.3 billion estimate (1) is for the benefits of

eliminating all U.S. power plant mercury emissions. Zeller and Booth apply this

annual measure of complete elimination of power plant mercury emissions to each

year

from 2005 to 2020. It is incorrect to compare the costs of EPA's regulation that

eliminates a fraction of the power plant emissions to the benefits of

eliminating

all power plant emissions of mercury (which would cost considerably more to

achieve).

Zeller and Booth suggest that the monetized benefits we use for IQ may be

understated. We agree that the willingness-topay numbers for IQ may understate

the

benefits of iQ. The value of an IQ point suggested by Trasande et al. (1) is

about

an order of magnitude greater than our est imate. However, as we noted in our

Let

ter, using their estimate does not change our finding that the costs of the

regulation are likely to exceed benefits.

Zeller and Booth's claim of mercury's detrimental effects might be overstated.

They

cite Grandjean et al.'s study (2) of the Faroe Islands to support their claim

that

the detrimental effects of mercury are " known. " They do not mention a study of

the

Seychelles (3) that did not find evidence of such a link and a study in New

Zealand

(4) that found mixed evidence. Even Grandjean et al. (2) found mixed results for

the

relationship between mercury and IQ scores. Nonetheless, we used conservative

estimates of the IQ-mercury relationship even when they are not statistically

different from zero.

We think that policy-makers should design regulations for controlling mercury

emissions so that expected benefits exceed expected costs. The current approach

fails that test.

Al Pater, PhD; email: old542000@...

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