EU science panel sees no need
for more perc testing
for more perc testing
A panel of scientists has given its blessing to the European Union’s risk assessment report for perchloroethylene that says no further testing or
risk reduction measures are needed concerning consumer exposures to perc.
The Scientific Committee of Health and Environmental Risks (SCHER) is an independent body that advises the EU on policy and proposals
concerning public health, consumer safety and the environment. Specifically,
SCHER addresses questions related to chemicals and human exposure to mixtures
of chemicals.
The EU’s risk assessment report, SCHER said, “covers all studies relevant for exposure and hazard assessment” of the solvent. The committee agreed with all the proposed conclusions for
perc, which also call for further measures to reduce occupational exposure
risks and consumer exposure through coin-operated drycleaning machines.
The panel concluded that perc is not mutagenic (i.e., it does not affect genetic
material) under typical conditions of oxidative metabolism and that liver
tumors observed in laboratory mice after exposure to the solvent are not
relevant to an assessment of risks to humans.
Commenting on the report, the Halogenated Solvents Industry Alliance said that mutagenicity is important in the consideration of carcinogenic
potential. HSIA also noted that the mouse liver tumors “have been the basis for quantitative estimates of cancer risk for
perchloroethylene developed by both U.S. and California regulators.”
SCHER said that the occupational exposure assessment considered six different
scenarios for the use of perc with drycleaning as the major application.
Exposure assessment for inhalation was based on measured eight-hour time
weighted averages; short-term peak level exposures were based on modeling. Both
inhalation and dermal exposure assessments are presented as typical values and
as realistic worst-case exposures and both assessments are forwarded into the
risk assessment.
Consumer exposure, mainly related to inhalation exposure of perc from drycleaned
clothes, was also based on measured and modeled data and also reflects exposure
to individuals living or working in the vicinity of drycleaning facilities.
The risk assessment report describes in detail all the toxicity studies
performed with perc, SCHER reported.
Summarizing the mutagenicity studies on perc evaluated in the risk assessment
report, SCHER said most of those that used oxidative activation by cytochrome
P450 gave negative results, suggesting that this pathway in perc
biotransformation does not result in formation of genotoxic metabolites.
One mutagenicity study in mice using specific conditions of high dosage showed a
marginal increase in the frequency of micronuclei in hepatocytes, SCHER noted.
SCHER concluded that these results do not indicate a need for further
mutagenicity testing.
“The small increase in micronucleus frequency may be due to secondary effects
such as cytotoxicity or related to the mode-of-action of perc for liver tumor
induction in mice, which is not considered relevant for humans,” SCHER said.
“Even a positive response in a repeat of this test will not affect the overall
weight-of-evidence conclusion that perc, under conditions of oxidative
biotransformation as occurring in the liver, is not mutagenic.”
On occupational exposures, SCHER said it agrees with the report’s conclusion that realistic worst-case scenarios show a need for limiting the
risks, taking into account risk reduction measures already in place.
But for indirect and combined exposures “there is at present no need for further information and/or testing and for risk
reduction measures beyond those which are being applied already.”
