MEMORANDUM

To: Halogenated Solvent Docket #  EPA-HQ-OAR-2002-0009

From: Elaine Manning, EPA

Date: October 3, 2008

Re: Reassessment of Non-cancer Hazard Associated with TCE to Support the
Halogenated Solvent Cleaning Rule

This memorandum presents a brief overview of the reassessment of chronic
non-cancer hazard conducted to support the Halogenated Solvent Cleaning
rule.  Non-cancer risks for the 1,080 halogenated solvent cleaning
facilities included in the 2002 National Emissions Inventory (NEI) were
recalculated using an air criterion for trichloroethylene (TCE) obtained
from the New York State Department of Health (NYS DOH, 2006).  A
Microsoft Excel workbook was provided to EPA on September 29, 2008 and
provided a summary of the recalculated chronic non-cancer hazard
estimates.  This memo serves as additional documentation to the
reanalysis.  

For the risk assessment for the Halogenated Solvent Cleaning rule
completed in August 2006, the maximum hazard index (HI) was 0.2, and
there were no facilities with an HI greater than 1.  The highest
facility HI of 0.2 was associated with 1,1,1-trichloroethane (TCA).  

The 2006 risk assessment used a chronic California EPA (CalEPA)
inhalation reference exposure level (REL) for TCE of 600 µg/m3 as the
chronic RfC.  This CalEPA inhalation REL is based on a 1973 study of 19
workers who experienced symptoms of drowsiness, fatigue, headache, and
eye irritation associated with TCE.  CalEPA identified the use of human
exposure data from workers exposed over a period of years as a strength
of the REL; however, the lack of reproductive and developmental toxicity
studies and the lack of a no effect level were identified as major areas
of uncertainty.  

Since promulgation of the Halogenated Solvent Cleaning rule, EPA became
aware of a newer assessment for non-cancer effects of TCE developed by
the NYS DOH.  The NYS DOH states that their air criterion for TCE of 10
µg/m3 based on central nervous system effects, is essentially
equivalent to a United States Environmental Protection Agency’s
chronic reference concentration (RfC) or an Agency for Toxic Substances
and Disease Registry’s chronic minimal risk level (MRL).  In addition
to evaluating a number of studies which look at numerous different
toxicological endpoints, the NYS DOH air criterion relies on a 1993
study which evaluated clinical neurological effects (as measured by
coordination tests) in 99 Danish workers.  For 70 of these workers, the
dominant exposure was TCE, while for 25 of the workers the dominant
exposure was to CFC 113.  Air exposures were extrapolated from
measurements of the urinary metabolite TCA.  Limitations of this study
include some uncertainty about the actual long term exposure levels of
the workers to TCE during their employment, and that 25 of the 99
subjects were exposed primarily to CFC 113.   The NYS DOH assessment is
limited by gaps in the data on developmental effects and immunotoxicity,
and concerns about adequacy of methods for evaluating health risks to
children (limitations it shares with the CalEPA assessment).  

In September 2008, EPA reassessed non-cancer hazard for all facilities
based on the use of the NY air criterion for TCE of 10 µg/m3.  Using
emissions data from EPA’s 2002 NEI database and the Human Exposure
Model (HEM-Screen), human health non-cancer hazards were recalculated
using the new value.  As might be expected, the HIs increased for the
662 (376 scaled-up) total facilities that emit TCE.  There were 10
facilities (6 scaled-up) estimated to have chronic non-cancer HIs
greater than 1.  The maximum HI was estimated to be 7.  A comparison of
results for these facilities may be found in Table 1.

         Table 1: Comparison of Hazard Index Results Across Facilities 

Source ID	Category Sector	Hazard Index	Hazard Index



1999 NEI

NYS DOH	1999 NEI

CalEPA	2002 NEI

NYS DOH	2002 NEI

CalEPA

NEI52497	General	2	.03	7	.1

NEI7348	Narrow Tube	1	.02	2	.04

NEI34658	General	-*	-	2	.03

NEIPA23-2947	Narrow Tube	2	.04	2	.03

NEI48613	General	.8	.01	2	.03

NEI7347	Narrow Tube	.7	.01	2	.03

* Facility not present in 1999 NEI Emission Inventory

Hazard Index values rounded to 1 significant figure



Reference:

California EPA, 1999.  Chronic toxicity summary: Trichloroethylene. 
Office of Environmental Health Hazard Assessment.

Available at:   HYPERLINK
"http://www.oehha.ca.gov/air/chronic_rels/pdf/79016.pdf" 
http://www.oehha.ca.gov/air/chronic_rels/pdf/79016.pdf 

New York State Department of Health (NYS DOH). 2006. Trichloroethene Air
Criteria Document, Final Report. NYS DOH Center for Environmental Health
Bureau of Toxic Substance Assessment. October. Available at:   HYPERLINK
"http://www.health.state.ny.us/environmental/chemicals/trichloroethene/d
ocs/cd_tce.pdf" 
http://www.health.state.ny.us/environmental/chemicals/trichloroethene/do
cs/cd_tce.pdf .

