Toxicological evaluation and limit values for
Methyl-tertiary-butyl ether (MTBE), Formaldehyde, Glutaraldehyde, Furfural
5. Regulations, limit values
Ambient air
Denmark (C-value): 1 mg/m3 (Larsen 1993).
Drinking water
Denmark: 125 µg/l (Larsen 1993).
EPA-proposal for health advisory for lifetime exposure: 20-200 µg/l (IPCS 1996).
Soil
-
OELs
Denmark: -
Sweden: 50 ppm (180 mg/m3) (Wibowo 1994).
ACGIH, USA: 40 ppm (144 mg/m3) (ACGIH 1996)
Classification
MTBE is not adopted on the List of Chemical Substances (Annex 1).
IARC/WHO
-
US-EPA
A human reference concentration of 3 mg/m3 was derived for MTBE based on a
NOAEL of 1453 mg/m3. The exposure level were converted to average continuous
exposure level and a total uncertainty factor of 100 was used to account for intraspecies
differences, interspecies extrapolation and lack of data (IRIS 1996).
Others
The Secretary´s Scientific Advisory Board on Toxic Air Pollutants, North Carolina
examined in 1994 the scientific evidence for the carcinogenicity of MTBE. At the time of
the conclusion the data from the oral study with rats was not available, however, the
board concluded that there is "some evidence" for carcinogenicity which
corresponded to category "C" in the EPA system as a possible human carcinogen.
Using the U.S.EPA multistage model for carcinogens on the data from inhalation exposure to
experimental animals a human 10-5 lifetime risk was calculated to an average
MTBE exposure level in the range of 0.04-0.64 mg/m3. However, it was stated
that normally the quantification of risk should not be performed for category C substances
(Lucier et al. 1995).
Rudo (1995) recommended on behalf of the Environmental Epidemiology Section, North
Carolina to classify MTBE in EPA category B2 as a probable human carcinogen as he
evaluated all the carcinogenicity studies including the oral rat study. |