Unocal officials, however, said it would be premature to
reach any
conclusions based on the data because there are some questions
about
the way it was gathered and analysed.
Prof Piamsak Menasveta, a marine scientist at Chulalongkorn
University
who carried out the survey on Unocal's behalf, said the
study showed a
significant increase in mercury levels since the last
time he
examined the fish at Unocal's platforms in 1993.
Piamsak was especially concerned with the high mercury
readings
found in cobia fish (plaa chon talae),
which is used in Thailand to make fish balls.
Unocal and Piamsak agreed that the situation has not yet
reached
the crisis stage, but could well do
so unless serious action is taken soon. They also agreed
that more
research is needed.
Total Exploration and Production Thailand is also carrying
out a
study of the fish around its
platforms. General manager Jean-Paul Azalbert said the
study is not
yet finished, adding that Total
has yet to decide whether it will release the results
to the public.
Piamsak expressed concern that there may be other sources
of mercury
contamination in the Gulf as fish
surveyed off Bang Sarae, 40 kilometres west of Map Ta
Phut on the
Eastern Seaboard, have also show high mercury levels.
''The mercury problem in the Gulf of Thailand seems to
be expanding,"
said Piamsak, director of the Aquatic Resources Research
Institute.
This is the third indication that there is mercury contamination
in
the sea off Rayong province.
Researchers found significant quantities of mercury and
cyanide in
the marine sediment while carrying
out an environmental impact assessment for the expansion
of the Map
Ta Phut industrial port.
Nevertheless, authorities recently approved the port's
expansion,
which will include a great deal of dredging work.
Pollution Control Department (PCD) officials have also
reported
rising mercury levels in the water off
Map Ta Phut Industrial Estate. But checks on companies
in the estate
failed to turn up any factory
releasing mercury over the permitted standard of five
parts per
billion (ppb).
Other possible sources for mercury, a dangerous neurotoxin,
include
natural or industrial run-off from
rivers emptying into the Gulf of Thailand, or even natural
seepage
from underground.
One major known source of mercury is the pumping of natural
gas from
underneath the Gulf of Thailand
by US-based Unocal and France-based Total. Both firms
discharge
mercury-contaminated water into the Gulf.
US-based Unocal says it currently releases around 90 kilogrammes
of
mercury into the sea every year
from its gas production operations, while Total says it
has released
around 35 kg of mercury in the three years it has been
operating.
Total eventually plans to pump its contaminated water directly
back
underground, and while Unocal
would like to do the same its underground reservoirs may
not be large enough.
The US-based firm announced last week that a new pollution
control
technology it has tested, called
PDT, could reduce mercury emission levels to around 10
ppb, from a
current average of around 130 ppb.
The technology will cost about Bt25 million to install
at each location.
Unocal currently has eight
platforms which discharge mercury-contaminated water into
the sea.
Piamsak, who has been carrying out fish surveys in the
Gulf since 1979,
said that between 1974 and
1990 mercury levels averaged around 0.1 parts per million
(ppm) -
considered the natural background
level - except for a brief upsurge caused by discharge
from the Asahi
Baking Soda Company in 1976, which was then corrected.
In 1993, Piamsak was hired by Unocal to carry out fish
surveys at its
Erawan, Platong and Funan
platforms, where he found average mercury levels of 0.22
ppm, 0.15 ppm
and .09 ppm, respectively.
Two of the 65 fish examined - or 3 per cent - had mercury
levels
exceeding the human health standard
of 0.5 ppm set by the US Food and Drug Administration
and the
UN Food and Agricultural Organisation (FAO).
Piamsak suggested this standard may actually be too low
for Thais,
who generally have a smaller body
size and eat on average four times as much fish as Europeans.
Unocal then hired an American firm called Battelle to carry
out another
survey, according to Tawatchai
Siripatrachai, Unocal's environmental manager.
It found that the average mercury levels in cobia fish
had gone up from
0.19 ppm in 1979 to 0.35 ppm
in 1993. In grouper, the average went up from 0.09 ppm
to 0.15 ppm.
But in five other species, the
average mercury levels had declined.
The Battelle report - which complained that some important
background
data on the age, size and health
of fish from Piamsak's 1979 study was not available -
concluded that
''there has not been a dramatic
change in mercury levels in Gulf fish between 1979 and
1993".
Piamsak then carried out another survey in 1994 and 1995,
catching 40
to 45 fish at each location.
This time he found that 11.63 per cent of the fish at
Erawan, the oldest
platform, had mercury levels
over the standard. The same was true for 7.5 per cent
of the fish at
Platong and 2.3 per cent of the
fish at Funan, the newest of the platforms studied.
It also turned out that 74 per cent of the fish caught
at Erawan had
mercury readings above 0.1 ppm,
the natural background level. The same was true for 63
per cent of the
fish at Platong and 56 per cent
at Funan. The average mercury levels in fish at all three
platforms
had also risen.
At the same time, Piamsak also surveyed fish at Bang Sarae
to serve
as a control group, assuming the
fish there would be relatively free of mercury. He was
surprised to
find that more than 5 per cent of
the fish there had mercury levels over the standard, too,
and 59 per
cent had higher than historical levels.
Unocal's Tawatchai, however, said he ''could not accept
the data" from
the 1994 to 1995 study. He
claimed that the number of fish sampled was quite small,
meaning that
each fish caught represented around 2 per cent of the
total findings.
Piamsak responded that he would have caught more fish if
he had been
provided with a larger budget and
more resources by Unocal, but asserted that the study
nevertheless
accurately represented the site.
The 1993 Battelle study also collected about the same
number of fish.
''This is the standard number of fish caught in such surveys,
even by
agencies such as the US
Environmental Protection Agency," Piamsak said. ''But
once an alarming
trend is spotted, a bigger study is carried out."
Tawatchai also suggested that Piamsak should not have mixed
together
the results from 1994 and 1995
because there were some differences in the data. Unocal
has now hired
another American firm called Tetra Tech to carry out a
broad environmental
study around the platforms, including health checks on
Unocal workers and a sampling of 100 fish.
Piamsak, who will continue to serve as an adviser for Unocal,
plans to
carry out more surveys around
Bang Sarae. Meanwhile, the PCD is currently undertaking
a study of heavy
metal contamination throughout the Gulf of Thailand.