U.S. Environmental Protection Agency Office of Water Standards & Risk Management Division Washington, DC 20460 Date: July 2013 

# USEPA Correction of the "Comparison of hydrofluorosilicic acid and pharmaceutical sodium fluoride as fluoridating agents—A cost–benefit analysis" by Hirzy et al. (2013)

# Correction Summary

The petitioner cited the results of the cost-benefit analysis in Hirzy et al. (2013) for many of the assertions in the TSCA section 21 petition to prohibit the use of hydrofluorosilicic acid (HFSA) as a water fluoridation agent.
EPA used the assumptions from Hirzy et al. (2013) and did not conduct an independent analysis. Therefore, EPA did not analyze the accuracy of the assumptions/inputs used in the Hirzy et al. (2013) cost-benefit analysis. The only correction that EPA made to the calculation was to divide the lifetime cancer risk by 70 years. Hirzy et al. (2013) assumed that the cancer risk was annualized. As a result, thelifetimecancer cases instead of the cancer casesper yearwere used in the cost-benefit analysis. The corrected cost-benefit analysis favors the use of HFSA over NaF (-$81M/year to -$8M/year) rather than NaF over HFSA, as calculated by Hirzy et al. ($1,011M/year to $6,191M/year).Column C D E F G H 

# Cost-Benefit Analysis for HFSA versus NaF (Hirzy et al. (2013) Case 1)

Arsenic conc (μg/L) Unit risk (μg/L)-1 Population cancer risk Exposed population*Cancer Cases per year (error: lifetime cancer cases) Cancer Treatment Cost per case Formula C*D E*F HFSA 7.8E-02 3.5E-05 2.7E-06 118000000 322 3500000 NaF 8.4E-04 3.5E-05 2.9E-08 118000000 3.5 3500000

Total Annual Health Costs ($ Millions /year) Annual Fluoridation Costs ($ Millions/year) Total Social Cost ($ Millions/year) Net Benefits forNaF compared to HFSA

($Millions/year) Formula G*H/1000000 C+D E15-E16 HFSA 1127 23 1150 1018 NaF 12 120 132

Correction on next page *The number of cancer cases for HFSA (320 vs. 322) and NaF (3.4 vs. 3.5) from Hirzy et al. (2013) are different due to rounding.Column C D E F G H

Arsenic conc (μg/L) Unit risk (μg/L)-1 Lifetime cancer risk *Correction: Annual cancer risk Exposed populationCancer Cases per year Formula C*D E/70 years F*G HFSA 7.8E-02 3.5E-05 2.7E-06 3.9E-08 118000000 4.6 NaF 8.4E-04 3.5E-05 2.9E-08 4.2E-10 118000000 0.05

Cancer Treatment Cost per case Total Annual Health Costs ($Millions/year) Annual Fluoridation Costs ($Millions/year) Total Social Cost ($ Millions/year) Net Benefits forNaF compared to HFSA

($Millions/year) Formula H*C/1000000 D+E F42-F43 HFSA 3500000 16 23 39 -81 NaF 3500000 0.2 120 120 *Correction using Hirzy et al. (2013) assumptions: Divide the lifetime cancer risk (or lifetime cancer cases) by 70 years. 

# OW's Correction to the Hirzy et al. (2013) Case 1 Cost-Benefit Analysis for HFSA versus NaFColumn C D E F G H

Arsenic conc (μg/L) Unit risk (μg/L)-1Population cancer risk Exposed population Cancer Cases per year (error: lifetime cancer cases) Cancer Treatment Cost per case Formula C*D E*F HFSA 4.3E-01 3.5E-05 1.5E-05 118000000 1776 3500000 NaF 8.4E-04 3.5E-05 2.9E-08 118000000 3.5 3500000

Total Annual Health Costs ($ Millions /year) Annual Fluoridation Costs ($ Millions/year) Total Social Cost ($ Millions/year) Net Benefits for NaF compared to HFSA ($Millions/year) Formula G*H/1000000 C+D E15-E16 HFSA 6216 23 6239 6107 NaF 12 120 132 

# Cost-Benefit Analysis for HFSA versus NaF (Hirzy et al. (2013) Case 4)

Correction on next page *The number of cancer cases for HFSA (1800 vs. 1776) and NaF (3.4 vs. 3.5)from Hirzy et al. (2013) are different due to rounding.Column C D E F G H

Arsenic conc (μg/L) Unit risk (μg/L)-1 Lifetime cancer risk *Correction: Annual cancer risk Exposed population Cancer Cases per year Formula C*D E/70 years F*G HFSA 4.3E-01 3.5E-05 1.5E-05 2.2E-07 118000000 25 NaF 8.4E-04 3.5E-05 2.9E-08 4.2E-10 118000000 0.05

Cancer Treatment Cost per case Total Annual Health Costs ($Millions/year) Annual Fluoridation Costs ($Millions/year)Total Social Cost ($ Millions/year)Net Benefits for NaF compared to HFSA ($Millions/year) Formula H*C/1000000 D+E F42-F43 HFSA 3500000 89 23 112 -8 NaF 3500000 0.2 120 120 

# OW's Correction to the Hirzy et al. (2013) Case 4 Cost-Benefit Analysis for HFSA versus NaF *Correction using Hirzy et al. (2013) assumptions: Divide the lifetime cancer risk (or lifetime cancer cases) by 70 years.