WTC environmental health assessment draft, May 2002

NYC 9/11 Public Portal Document

Dioxin

Tier Action Dioxin (settled dust) Dioxin (indoor air)

Level Basis Level Basis

I Aggressive >70 ng/m^ Risk=b3.scd >0.03 ng/m" Risk“bascd cleaning. If levels screening level screening level persist, take for residential for residential additional action to 5Cttmg-fE=e4^ setting (E-04 x reduce exposure. tO T-yO 70 ng/nr 0.03 ng/m’ represents a represents a 1X10 “ risk 1X10-“ risk estimate for a li estimate for a 1 year exposure year exposure

n Maintain 70 ng/m‘ to 2 2 ng/m2 is risk- 0.03 ng/m' to e:0eiTig/m3-re recommended ng/m^ (or based screening 0.001 ng/m’ (or Risk“ based cleaning methods. background) level for background) screening level Consider additional residential forrcsldentiai monitoring setting sctting-f&=e4-x Wr) 2 ng/m'.2 0.001 ng/m’ represents a represents a 1X10“ risk' 1X10“ risk estimate for a 30 estimate for a year exposure 30 year exposure

ffl No further action <2 ng/m^ (or Deteimiuation of <0.001 rig/ni’ Determination background) local background (or background) of-Rjcal Level could also background be set at that; Level could found in also be set at background, or that found in unaffected, areas, background, or so that no unaffected, increase in risk areas, so that due to dioxin no increase in- would be .I risk due to expected. dioxin would be expected.

The inputs to the dose equations were based on the exposure assumptions that NYSDOH used in assessing office buildings in Binghamton, NY, and the proposed cancer slope factor for dioxin. In addition, the Tier 1 and III benchmarks equate to a lifetime exposure level which is

8

CONFIDENTIAL, CITY_21MC100_003423796 SUBJECT TO PROTECTIVE ORDER NO. 2, SEPT. 2008

NYC-WTC_000176167