1 

### Charge Questions for the Peer Review of the draft Workplan R isk A ssessment
for Methylene Chloride (DCM)

August 2013

OPPT focus e d its risk assessment on the use of DCM in paint stripping. T here are human health

concerns for both cancer and non

- cancer effects with DCM use

- applicatio n

. Only the inhalation route of exposure was evaluated and risk estimates were calculated for consumers and workers using DCM

- based paint strippers. Risks also were estimated for individuals physically near the

residential u ser and who are not using the DCM

- based product ( also referred as called bystanders

or non

- users).

General Q uestion on the R isk A ssessment Document

Issue 1. Th is r i sk ass e s s me n t i s d iv id e d in t o t h r e e c h a p ter s with eight a pp e nd i ce s. Th e f

i r st tw o c h a p ter s d e s cr ib e t h e s c o pin g e x erc i se E P A u s e d a n d b a c k g r o un d

i n f o r m a t i on on DCM t h at s et s t h e s t age f or t h e in f o r m a t i on ava il a b le a n d u s e d i n th e

r i sk ass e ss me n t

. C h a p te r 3 in c lud e s t h e e x p os u re , h a z a r d assessment a nd r i sk

c h a r a ct e r i z a t i on a n d a s ect i on on un cert a in t i e s of the r i s k ass e ss m e n t

. Th e r i sk

ass e ss me n t i s in te nd e d t o p r ov id e a c l e ar a nd tr a n s p a re n t s u mm a r y o f t h e A g e n c y ’ s

a n a l ys i s.

Question 1

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

. P lease provide specific suggestions for improving

the clarity and transparency of the risk assessment document.

Question 1

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

. Please provide any ot her relevant literature, reports, or data that would be useful to support the risk assessment

.

Questions on the E xposure A ssessment

Issue 2 : Wo r kpl a c e e x p os u r e e s t i m a t e s w er e de v e l o p e d f or a dul t s using DCM

- based paint strippers

. EPA found l imited published data for DCM air concentrations in workplace settings during use of DCM

- based paint strippers. These data were used for estimating occupational inhalation exposures.

Question 2

- 1 Pl ea se c o mm e nt on t he a pp r o ac h u s e d, a nd p r ov i de a n y sp e c i f i c sug g e s ti ons

or r ec o mm e n d a ti ons f or a lt er n a ti ve a p p r o ac h e s, m o d e l s or i n f o r m a ti on th a t shou l d be

c ons i d ere d b y t he A g e n c y f or im p r ov i n g its assessment of DCM w o r kp l a c e e x posu r e s
, including specific citations (if available) of other data sources characterizing occupational

inhalation exposures,

Issue 3. Inhalation exposures f rom consumer uses of DCM

- based paint stripp ers were estimated using the EPA’s Multi

- Chamber Concentrations and Exposure Model (MCCEM). EPA conducted a sensitivity analysis of selected model parameters to identify2 critical parameters essential to the modeling approach used to estimate inhalation exposures. This analysis guided the selection of exposure scenarios and provided the most sensitive input parameters for generating central ten dency and upper

- end DCM air

concentration s

.

Question 3

- 1

. Pl ea se c o mm e nt on t he a pp r o ac h u s e d a nd p r ov i de a n y s p e ci f i c sug g e s ti ons

or r ec o mm e n d a ti ons f or a lt er n a ti ve a p p r o ac h e s, m o d e l s, or i n f o r m a ti on t h a t should be

c ons i d e r e d b y t he A g e n c y i n d e v e l op i ng t h e e x posu r e a ssu m p ti ons a nd e s tim a t e s f or t he

consumer use of DCM

- based paint strippers a nd f or t he b y s t a nd e r / non

- us e rs (e.g., children, women of childbearing age). As part of the review, please comment on the strengths and weaknesses of the evaluation of different exposure scenarios and the choice

of assumptions/ input parameters for generating central tendency and upper

- end DCM air

concentrations.

Questions on the Hazard Assessment

Issue 4. T h e inh ere n t h a z a r d s of DCM h a ve b ee n w e ll c h a r a ct e r i ze d . EPA used a range of

acute or chronic human health hazard values to evaluate potential non

- cancer risks in workplace and consumer settings . For instance, EPA used the point of departures (PODs)

from the Cal ifornia EPA ’s reference exposure level ( Cal EPA REL) and the Spacecraft Maximum Allowable Concentration (SMAC) to evaluate potential acute risk s for residential users and bystanders/non

- users (e.g., children and women of childbearing age)

. H armful concentrations of DCM , leading to death, have been reported in enclosed

environments where DCM

- based paint strippers were used during bathroom tub refinishing projects. Based on this concern, EPA also included the acute exposure guideline levels (AEGLs) in the analysis to determine if DCM air concentrations would be exceeding the AEGL thresholds for disability (AEGL

- 2) and lethality (AEGL

- 3)

. EPA’s Integrated Risk Information System (IRIS) program has recently d eveloped reference concentration (RfC) and inhalation unit ris k (IUR) values for DCM . Th is assessment used

the POD from the EPA’s IRIS RfC to evaluate chronic non

- cancer risks. The EPA’s IRIS

IUR w as used to evaluate cancer risks in this assessment

.

Question 4

- 1

. Please comment on EPA’s use of the acute PODs that were identified

from the technical documents supporting the Cal EPA REL, SMAC and AEGL derivations. As part of the review, please provide your input on the appropriateness of the approach, including its underlying assumptions

, strengths and weakness es

. P lease

p rovide a n y s p e ci f i c sug g e s ti ons or r ec o mm e n d a ti ons f or a lt er n a ti ve a p p r o ac h e s t h a t
sh ou l d be c ons i d e r e d b y t he A g e n c y i n characterizing the acute inhalation risks. P lease provide relevant data or documentation and rationale for including other studies and endpoints for consideration

.

Q u e s t ion 4

- 2 : Please comment on EPA’s choice of PODs and IUR for evaluating the

non

- cancer and cancer risks

, respectively for chronic exposures to DCM

- based paint strippers. As part of the review, provide your input on the appropriateness of the approach , including its underlying assumptions, strengths and weaknesses. Please3 provide a n y s p e ci f i c sug g e s ti ons or r ec o mm e n d a ti ons f or a lt er n a ti ve a p p r o ac h e s t h a t
sh ou l d be c ons i d e r e d b y t he A g e n c y i n characterizing the chronic inhalation risks to

workers. P lease provide relevant data or documentation and rationale for including other studies and endpoints for consideration

.

Questions on the Risk Assessment

Issue 5. T he margin of exposure ( MOE) is the ratio of the hazard value to the exposure.

The MOE approach used the PODs identified in the Cal EPA REL and SMAC to evaluate potential acute risks in residential users and b y s t a nd e r s / non

- us e rs (e.g., children, women of childbearing age). Benchmark MOEs of 60 and 10 were used to determine acute risks

based on the uncertainty analysis conducted in the Cal EPA REL and SMAC assessment s, respectively. H azard quotients (HQs) were used to evaluate potential acute risks in residential settings by comparing the AEGL values with the acute exposure estimates. HQs greater than 1 were interpreted as a potential acute risk . For chronic occupational risks, t he POD from the EPA’s IRIS RfC was chosen as the basis fo r the non

- cancer MOE

calculations . A benchmark MOE of 30 was used to interpret chronic risks for workers based on the uncertainty analysis in the EPA’s DCM IRIS assessment

. The EPA’s IRIS

IUR was used to evaluate potential chronic risks to cancer endpoints for the worker exposure scenarios

. The r i sk c h a r a c t er i z a t i o n also provides a di s c u ss i on o f t h e

un cert a in t i e s s u rr o und i n g t h e r i sk c a l c u la t i o n s.

Q u e s t ion 5

- 1: Pl ea se c o mm e nt on t he assumptions

, s t re n g t hs a nd wea kn e s s e s of t he

M OE and HQ a pp r o a c hes us e d t o e s tim a t e t he ac u t e non

- cancer r i sks t o consumers of

DCM

- based products, i n c l ud i ng bystanders/ non

- u s er s (e.g., children, women of childbearing age) . Please also comment on the selection of composite uncertainty factors

that were used as benchmark MOEs to determine the acute risk s

.

Q u e s t ion 5

- 2: Pl ea se c o mm e nt on t he assumptions

, s t re n g t hs a nd wea kn e s s e s of t he

M OE a pp r o a c h us e d to e stim a te t he c h r o n i c non

- ca n ce r r i sks f or w o r kp l a c e e x posu re s

. Please also comment on the selection of composite uncertainty factors that were used as

benchmark MOEs to determine the chronic risk s

.

Q u e s t ion 5

- 3: Pl ea se c o mm e nt on t he assumptions

, s t re n g t hs a nd wea kn e s s e s of t he

cancer estimation risk approach us e d f or t he w o r kp l a c e e x posu re s.

Question 5

- 4 : Please comment on whether the risk assessment document has adequately described the uncertainties and data limitations in the methodology used to

assess risks to allow the EPA to reduce risks to human health from DCM . Please comment on whether this information is presented in a transparent manner.