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Michael Hone cutt
Tuesda , June 18, 2019 12:50 PM
Chancellor, Erin
Eth lene o ide ke findings

Hey Erin,
I will go ahead and share our key findings with you, but please hold it close for now. The wording on this is subject to
change in our public comment draft, but the conclusions should not change. The important things are highlighted
below in yellow.
Basically, we plugged the data used to derive the EPA model back into the model to see how many cancers the model
predicts are in the data used to derive the model. Out of
k occupationally exposed workers, developed lymphoid
cancer. When you plug the exposure data back into EPA’s model, it predicts that ,
workers developed cancer, way
higher than the actual . Our model predicts that developed cancer, just slightly higher than the actual . So our
model is more predictive. EPA’s model is over predictive. Though I know NCEA and IRIS will not want to budge off of
their position, it’s kind of hard to argue about the math. It’s pretty straightforward.
Like I said, we’re cleaning up the document and making sure we are precise in our wording, but should have it out for
public comment by the end of next week at the latest.
Best,
Mike

Ke Finding
Ethylene oxide EtO is a chemical with many industrial applications, with particular use as a
sterilant for medical devices.
Because EtO is emitted in Texas and has been determined to be a carcinogen, the TCEQ
undertook a carcinogenic dose response assessment and derivation of an effect screening level for this
chemical.
Review of the EtO literature demonstrated that EtO operates by a direct acting mutagenic
mode of action MOA and suggests that the EtO cancer dose response should be no more than linear
overall with sublinearity expected by both TCEQ and USEPA at endogenous levels and below.
In addition, EtO is produced endogenously, and an ambient air concentration of . ppb would
be required to increase the internal dose endogenous exogenous of EtO by standard deviation.
Therefore, ambient EtO concentrations of less than ppb would not be expected to produce
substantively more risk than endogenously produced EtO.
Consistent with TCEQ guidelines TCEQ
, we reviewed recently derived toxicity factors and
guideline air levels to determine if there is a toxicity factor or guideline air level that is suitable for
adoption by the TCEQ. As such, we reviewed the USEPA’s recently completed Evaluation of the
Inhalation Carcinogenicity of Ethylene Oxide USEPA
. The USEPA derived a unit risk factor URF
of . E per ppb, which corresponds to a in
,
excess cancer risk air concentration of .
ppb.
The human data available for deriving the USEPA’s EtO toxicity factor came from two very high
exposure occupational cohorts UCC and NIOSH that provide no information about the shape of the
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