EPA interim final report on WTC background study, April 2003

NYC 9/11 Public Portal Document

Table 6. Dioxin

Tier Action Dioxin (settled dust) Dioxin (indoor air) Level Basis Level Basis I Aggressive >120 ng/m^ 120 ng/m^ >0.03 ng/m’ 0.03 ng/m^ cleaning. If levels represents a represents a persist, take 1x10"* risk IxlO'^risk additional action to estimate for a 1 estimate for a 1 reduce exposure. year exposure year exposure n Maintain 120 ng/m^ to 4 ng/m^ 0.03 ng/m’ to 0.001 ng/m’ recommended 4 ng/m^ (or represents a 0.001 ng/m’ (or represents a cleaning methods. background) 1x10"* risk background) IxlO'^risk Consider additional estimate for a 30 estimate for a monitoring year exposure 30 year exposure m No further action <4 ng/m^ (or Level could also <0.001 ng/m^ Level could background) be set at that (or background) also be set at found in that found in background, or background, or unaffected, areas, imaffected, so that no areas, so that increase in risk no increase in due to dioxin risk due to would be dioxin would expected. be expected.

Toxicity criteria for dioxin:

Oral Slope Factor = 1.0 E 06 (mg/kg/day) ’ [EPA, 2001]

(Inhalation cancer risk was calculated by route-to- route extrapolation of oral Slope Factor)

The table above reflects the proposed cancer Slope Factor for 2,3,7,8 TCDD and the toxicity equivalence (TEQ) paradigm for carcinogenic dioxin/furan congeners present in EPA’s draft dioxin reassessment [EPA, 2001]. An equivalent table reflecting the previous IRIS-verified cancer Slope Factor for 2,3,7,8 TCDD would be represented by multiplying all listed values by a factor of six.

The methodology for estimating dose from wipe sampling data (see Appendix D) is consistent with the approach NYSDOH used in assessing office buildings in Binghamton, with modifications made to input parameters to reflect residential rather than occupational exposure. In addition, the Tier HI benchmark equates to a lifetime exposure level which is approximately one tenth of that which results from current dietary intake of dioxin (65 pg/d). It is thus

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