MtBE (Methyl
Tertiary-Butyl Ether) Occurrence in Florida Drinking
Water Systems
MTBE
is a fuel additive that has been in use since 1979 and
was one of the additives recommended by EPA to be used as
a mechanism for air pollution control in 1992 and even
more so in 1995. Primarily, the EPA requirement to use
reformulated gas is limited to those states/regions where
carbon monoxide emission reductions are critical (and
therefore has not been required in Florida). While MTBE
is found in fuels used in Florida, it is not at the
concentrations (approx. 15%) where these EPA requirements
are mandated.
As a
result, the problems seen in other states are not readily
occurring in Florida. This is due primarily to Florida's
geological and hydrogeological conditions (flat and
shallow aquifer) and the low concentrations of MTBE in
Florida Fuels.
Florida
has monitored the concentration of MTBE at petroleum
contaminated sites since Feb. 1990, and has established a
cleanup target level of 50 parts per billion. This level
is based upon organoleptic (odor) conditions and may
change if toxicological information determines the
chemical to be a carcinogen. While MTBE is frequently
found at petroleum contaminated sites, it poses less
problems compared to other states and is not normally a
significant "driver" in cleanup efforts.
Benzene (a known carcinogen) is one of the more abundant
chemicals found at gasoline contaminated sites and has a
cleanup target level of 1 part per billion and typically
controls the cleanup time/effort.
The
Florida Drinking Water Program has investigated the
occurrence and concerns of MtBE contamination in
Florida’s public water systems (PWS). PWSs have been
sampling for this contaminant as an unregulated
contaminant since the early 1990’s. As an unregulated
contaminant it has no established health standard,
referred to as a Maximum Contaminant Level or MCL.
However, EPA has established a level at which it does
present a detectable taste and/or odor. This level is
presented as a range of 20-40 ppb. Past EPA research
indicates that this level is orders of magnitude below
(more stringent) than associated health risks to humans.
This is however based on mice and rat studies on MtBE
noncancer, cancer, reproductive, developmental, neurotoxicity, and mutagenicity effects. In essence the
taste and odor level governs a water’s acceptability to
the consuming public. The PWS section of FDEP pulled all
the sampling data for all systems since 1993. Of the 1000
plus samples in the database only two systems exceeded a
20 ppb level. Those two systems, Three Worlds Camp Resort
(Polk County) with 228 people and Oklawaha Water Works
(Marion County) with 994 people, showed results of 166
ppb (1994) and 104 ppb (1997) respectively. However, both
systems have since resampled (within three months) and
results indicate "no detection".
In
summary, the levels found in Florida indicate that none
of the Drinking Water Systems are experiencing MtBE
contamination at the taste/odor thresholds; and secondly
the odor/taste nature of the contaminant itself makes it
unpalatable at levels that might cause a health concern
based on EPA’s present knowledge of the toxicity of
this contaminant.
MTBE Sampling
Results
The
spreadsheets offered below contain the results of 8,739
MTBE samples taken since November 1, 1993. MTBE was
detected in 428 samples and not detected in 8,311
samples. Detections are easily identified by an entry in
the Result column, and with ** in the PWS ID column.
The
spreadsheets contain the following columns:
PWS
ID (the ID contains the county code, see 'Information
from the Drinking Water Database' for the full
explanation)
NAME
TYPE
(C = Community, P = Nontransient Noncommunity, N =
Transient Noncommunity)
SOURCE
(S = Surface, G = Ground)
SAMPLE
TYPE (C = Check, D = Distribution, E = Composite, N =
Entry Point, P = Plant, Q = Quarterly, R = Raw, S =
Special)
CONTAM
ID (= 2251 for MTBE)
SAMPLE
DATE
REMARKS
