Page 1 of 3 

### O P P T P r o p o s e d D r a f t C h a r g e t o E x t e r n a l P e e r R e v i e w e r s f o r t h e r e v i e w o f

t h e T S C A W o r k p l a n C h e m i c a l R i s k A s s e s s m e n t o f T C E

D e c e m b e r 2 0 1 2

OPPT focused its risk assessment on three specific uses of TCE: as a degreaser by workers in

small commercial facilities , as a degreaser by consumers (hobbyists), and as a clear protective coating spray (an art/crafts use) by consumers (hobbyists )

. For all uses, only the inhalation route of exposure was evaluated, and risk estimates for individuals physically nearby by the user of the TCE product (but not using it; called e ither bystanders or non

- users) were also calculated.

General Question on the Risk Assessment Document

Issue 1. The risk assessment is divided into three chapt ers and there are six appendices and three supplemental documents . The first two chapters describe the scoping exercise

EPA used and background information on TCE that sets the stage for the information available and used in the risk assessment. Chapter 3 includes the exposure, hazard and

risk characterization and a se ction on uncertainties for each of the three uses of TCE which

are the focus of this risk assessment. The risk assessment is intended to provide a clear and transparent summary of the Agency’s analysis

.

Question 1

- 1: Please comment on whether the characterization provide s a clear and logical summary of EPA’s analysis

. P lease provide specific suggestions for improving the

document.

Question 1

- 2: Please comment on whether appropriate background information is provided and accurately characterize d

. Please provide any other significant literature, reports, or data that would be useful to complete this characterization

.

Questions on the Exposure Assessment

Issue 2

. Workplace e xposure estimates were developed for adults working as degreasers in

small com mercial settings. These scenarios represent small businesses that use degreaser products/equipment regularly, but not all day during the course of their job. An example would be a garage/car mec hanic business. Readily available data from sources such as the National Emissions Inventory (NEI), Toxics Release Inventory (TRI), and National Occupational Exposure Survey (NOES), other literature sources and assumptions were used to develop the workpla ce exposure assessment.

Question 2

- 1 : Please comment on the approach used, and provide any specific suggestions or recommendations for alternative approaches , models or information that should be considered by the Agency for improving the workplace exposure assessment ; including the bystander/non

- user estimations

.

Issue 3

. Exposure estimates were developed for two different consumer uses : a degreasing product and a clear protective coating spray product. Both products are ae rosol spraysPage 2 of 3 and appear to be available for sale and use by consumers/hobbyists in the US. There were no reliable data regarding the hobbyist scenarios, so OPPT estimated hobbyist exposures using a standard exposure assessment modeling approach (the Consumer Exposure Module [CEM] of the Exposure and Fate Assessment Screening Tool, or E

- FAST).

Question 3

- 1 : Please comment on the approach used and provide any specific suggestions or recommendations for alternative approaches, models, or information ( e.g. , information on duration an d number of user events) that c ould be considered by the agency in developing the exposure assumptions and estimates for the hobbyist degreaser

and clear protective coating spray use s , and for the bystander/non

- user.

Questions on the Hazard Assessment

Issue 4

. Information on the inherent hazards of TCE has been well

- characterized. There

are six major domains of adverse effects (primarily in animal models) following exposure

to TCE: non

- cancer effects on the liver, kidney, nervous system, immune system, reproductive (predominantly male) toxicity, and devel opmental toxicity ; as well as cancer effects on the liver, kidney and the immune system (Non

- Hodgkins Lymphoma, or NHL)

. TCE metabolism is extensive in mammalian systems and different metabolites are likely to be responsible for different toxicity. The 20 11 US EPA Integrated Risk Information System ( IRIS ) assessment for TCE reviewed many human and animal studies. There were 32 endpoints/27studies identified as “candidates” for developing the reference concentration (called the RfC) . Physiologically

- based pharmacokinetic (PBPK) modeling was used by the IRIS program to derive different HEC ( i.e., human equivalent concentration) values

. OPPT report s all of these values, but focused on using only the 12 inhalation studies

. Rather than use a single value to re present hazard, OPPT used the lowest lower bound

HEC 99 – the 99 th percentile predicted HEC concentration

-- f or the effect of concern for

e ach target organ. Furthermore, OPPT distinguished between effects that may occur following acute exposure ( i.e., neurotoxicity and developmental toxicity) versus those that may occur following chronic exposures ( i.e., liver, kidney, immunotoxicity, and male reproductive toxicity and cancer).

Question 4

- 1: Please comment on the strengths and weaknesses of evaluating different endpoints based on exposure durations ( i .e., acute versus chronic).

Question 4

- 2 : Please comment on the strengths and weaknesses of using multiple values for each type of adverse effect

.Page 3 of 3 Questions on the Risk Assessment

Issue 5

. A margin of exposure (MOE) approach was used to evaluate potential non

- cancer risk and the IRIS inhalation unit risk (IUR) was used to evaluate potential cancer risk. The small commercial degreaser workplace risk estimate assumed chronic (daily)

exposures to TCE. The consumer use of both the degreaser and the clear protective coating spray used in the arts/crafts field risk estimates assumed only intermittent ( acute ) exposures to TCE. As part of the risk characterization, there is a discussion of the

unce rtainties surrounding the risk calculations

.

Question 5

- 1 : Please comment on the strengths and weaknesses of the MOE approach

used to estimate the chronic , non

- cancer risk for the workplace exposures; including non

users.

Question 5

- 2 : Please comment on the strengths and weaknesses of the MOE approach used to estimate the acute risk to consumers; including the non

- users. S pecifically, please comment on the decision to limit the analysis to acute exposures without residual

concern between events ( i.e., once/week for users of the clear protective coating spray , and twice/month for degreaser use rs ).