Abstract: A critical review of the levels of persistence organic chemicals in Malaysian waters from 1980 to 2002. This review concentrated on the detection several toxic substances by groups of scientists in the marine environment, evaluated their quantities and provides estimates of their potential danger for the health of both marine life and humans. The compounds include polycyclic aromatic hydrocarbons, tributyl-tin and pesticides. In summary, the levels of some persistent organic chemicals is lower compared with other Southeast Asia countries and the levels in this region still at the medium level compared with more urbanized and industrialized regions in the West. Nevertheless, continuous monitoring and investigations on the level of the persistent organic chemicals are needed in Malaysia. Transboundary pollution potential should be taken as an important consideration in any development project especially in Southeast Asia.
THE MELACCA STRAITS
The Melacca Straits are bordered by four countries; Malaysia, Thailand, Indonesia and Singapore. However, the navigational channel passes through the territorial seas of Malaysia, Indonesia and Singapore (Chua et al., 2000). The Straits of Melacca is located between the East coast of Sumatra Island in Indonesia and the West coast of Peninsular Malaysia and is linked with the Straits of Singapore at its South-east end (Fig. 1 ). The straits is bordered on the North-west by a line from Ujong Baka (5°40’N, 95°26’E) which is the North western tip of Sumatera Island, Indonesia, to Laem Phro Chao (7°45’N, 104°20’E), the South extremity of Ko Phukit Island, Thailand and on the South-east by a line from Tahan (Mountain) Datok (1°20’E, 104°20’N) and Tanjung Pergam (1°10’E, 104°20’N) (Hamzah and Basiron, 1997).
SOUTH CHINA SEA
Covering an area of 3.8 million square kilometers (Fig. 1 ), the South China Sea which includes the Gulf of Thailand and Tonkin is a marginal sea surrounded by land with access to it between West Malaysia and Indonesia at the Kalimantan Straits in the Southwest and the Philippines and Taiwan at the Luzon Straits to the Northeast (Morton and Blackmore, 2001). Countries that have major influence on the claims to the sea include China, Malaysia, the Philippines and Vietnam, although Thailand, Indonesia and Taiwan have also exerted some claims.
| Fig. 1: | Map of Straits of Melacca and South China Sea |
The South China Sea has significant islands including Hainan in the Northwest, Palawan in the Southeast and hundreds of smaller islands, atolls, submerged reefs and banks. The island groups of the South China Sea are all disputed and sovereignty is claimed over them by a number of countries. Conflict has arisen over them in recent years caused by perceived national rights. Disputed boundaries in the South China Sea include areas in the Gulf of Tonkin between Vietnam and China and the Spratly islands off the coast of Sabah between Malaysia, China and the Philippines, which it is estimated to posses six billion barrels of oil (Morton and Blackmore, 2001). With vast mineral resources as well as fisheries resources, it is no surprise that the South China Sea is a hotbed area for overlapping sovereignty claims.
MARINE POLLUTION
For close to 30 years, most academics studying the phenomena of marine pollution have adhered to a definition developed by a UN body, the Group of Experts on the Scientific Aspects of Marine Pollution (GESAMP) (Anonymous, 1997), who define it as the introduction of man, directly or indirectly, of substances or energy into the marine environment (including estuaries) resulting in such deleterious effects as harm to living resources, hazard to human health, hindrance to marine activities including fishing, impairment of quality for use of sea-water and reduction of amenities (Graya and Bewersb, 1996; ; Chua et al., 2000; Islam and Tanaka, 2004).
The definition has two important qualities. Firstly, it is an action oriented. Marine pollution is conceptualized as a human activity, thereby omitting all natural activities that could potentially have damaging effects on the ocean eco-system. So, for example, earth quakes or volcanic eruptions that emanate from the ocean floor and subsequently damage or change already existing ocean eco-systems would not be considered pollution. Secondly, the definition is amenable to measurement. Marine pollution is harmful and its danger can be identified in a variety of ways. For example, it is easy to see the deleterious effects that oil spills have on the sea birds and mammals that happen to run into them. Scientists likewise can readily identify various toxic substances found in the marine environment, measure their quantities and provide estimates of their potential danger for the health of both marine life and humans.
Hydrocarbons
A hydrocarbon is an organic chemical compound that is comprised only of
carbon (C) and hydrogen (H) atoms. Many oils, fats, waxes, solvents and paraffin
are either hydrocarbons or contain large hydrocarbon sub-units. Hydrocarbons
are natural chemical compounds made up of carbon and hydrogen (Peachey,
2003).
All hydrocarbons fall under one of the three following categories depends on their carbons bonding. That is saturated hydrocarbons, unsaturated hydrocarbons and polycyclic aromatic hydrocarbons. The least dangerous is saturated hydrocarbons because they have no double, triple or aromatic bonds between carbons. Unsaturated hydrocarbons have at least one double or triple bond between carbons and the most lethal is Polycyclic Aromatic Hydrocarbons (PAHs). They have at least one aromatic ring of carbons (Zakaria et al., 2002; Young et al., 2004).
PAHs are the type of hydrocarbons that are causing major problems (Peachey, 2003). Sources of PAHs include oil spills, road run off and burning wood and coal. They are mutagenic (causes body mutations), morphogenic (causes deformities), carcinogenic (causes cancer) and teratogenic (causes fetal mutations) (Zakaria et al., 2002; Pufulete et al., 2004). The fact alone that we expose ourselves daily to these chemicals when we know how dangerous they are is amazing, but the fact that we are killing our planets wildlife through our carelessness is catastrophic.
The impact of oil pollution on the ecology of coastal and marine ecosystems is particularly destructive following massive oil spills caused by maritime accidents (Chua et al., 2000; Yamamoto et al., 2003). However, gas exchange between the water and the atmosphere is decreased by oil remaining on the surface of the water, with the possible result of oxygen depletion in enclosed bays where surface wave action is minimal (Hawkins et al., 2002). Coral death results from smothering when submerged oil directly adheres to coral surfaces and oil slicks affect sea birds and other marine animals (Furness and Camphuysen, 1997).
Tributyl-tin (TBT)
Organotin compounds have developed into an important commodity since the
1960 with antifouling TBT paints having brought large financial savings in the
shipping industry (Sudaryanto et al., 2004).
On the other hand, TBT is so toxic that it had adverse affects on non-target
organisms such as oysters and gastropods (Kan-Atireklap
et al., 1997; Hsia and Liu, 2003). It is
also well documented that TBT can be accumulated to a high level by some marine
vertebrates, including fish, fish eating birds and marine mammals such as dolphins.
These adverse effects have prompted a restriction of TBT usage in many countries
e.g., USA, France, Switzerland, New Zealand and Japan (Morton
and Blackmore, 2001).
Pesticides
A pesticide is any substance or mixture of substances intended for preventing,
destroying, repelling or mitigating any pest (Barakat, 2004).
Though often misunderstood to refer only to insecticides, the term pesticide
also applies to herbicides, fungicides and various other substances used to
control pests. Under United States law, a pesticide is also any substance or
mixture of substances intended for use as a plant regulator, defoliant, or desiccant
(United State Environmental Protection Agency) (Charnley
and Patterson, 2003).
The use of agriculture chemicals is the main cause of pesticide pollution in the marine environment. It is estimated that in East Sumatera alone about 3780 t of insecticides, 110 t of fungicides, 291 t of rodenticides and 22 t of herbicides are used annually (Chua et al., 2000). It is inevitable that some of these chemicals are leached to rivers and to coastal and estuarine environments finally ending up in the marine sediments.
Nutrients
Nutrient source in the marine environment can be broadly categorized into:
point sources, which are domestic sewage effluent including human and household
waste and urban waste water, industrial discharges, including detergents and
shipping discharges of sewage and grey water (Nixon et
al. 2001). Secondly, diffuse sources which are: agriculture run-off
includes inputs of inorganic fertilizers, slurry and silage that contaminate
watercourses and transported into the sea via rivers, natural background inputs
including rock weathering, lightening, soil leaching and dead/decaying organic
matter and deposition of atmospheric nitrogen oxides from burnt fossil fuels
can contribute to the nitrogen budget of oceans (Billen
et al., 1999).
The relative contribution of each source varies over time according to land use, climate, technology, national and international regulations. There is also variation between coastal waters due to their associated dispersion rates. Whilst nutrients are essential for life in the oceans, there is growing concern over the accelerated nutrient enrichment of coastal waters as a result of human activities, known as cultural eutrophication. The adverse impacts on water quality threaten the ecology and use of the marine environment. Cultural eutrophication is considered to be one of the fundamental causes of the increased occurrence of algal blooms-an explosion in the growth of marine phytoplankton (Grizzetti et al., 2003).
DETECTION OF VARIOUS ORGANIC CHEMICALS IN MALAYSIAN WATERS
The major areas of study/survey are shown in Fig. 2.
Hydrocarbons
Early studies on hydrocarbon in the Straits of Melacca began with Phang
et al. (1980) which found concentrations of between 10 to 120 ppb
of petroleum hydrocarbon in the coastal waters off Penang. In 1989, two studies
in the near shore (Law and Veellu, 1989) and offshore
(Law and Yeong, 1989) waters of Port Dickson analyzing
water and sediments found concentration of between 2.52 to 73.34 ppb (mean of
32.24 ppb) and 14.69 to 150.28 ppb (mean of 66.71 ppb) of hydrocarbon in the
water samples from nearshore and offshore stations respectively.
| Fig. 2: | Areas of detection of persistent organic chemicals in Malaysian waters. 1: Yang et al. (1998), 2: Kan-Atireklap et al. (1997), 3: Hossain et al. (1999) and Sivalingam et al. (1982), 4: Law and Ravinthar (1989), Law and Yeong (1989) and Moradi et al. (1999), 5: Law and Rahimi (1986), Law and Zulkifli (1987), 6: Law (1990) and 7: Law and Libis (1988) |
For sediment samples, the concentrations found were between 2.1 to 70.4 ppm for nearshore stations and 21.73 to 77.06 ppm for offshore stations, respectively. This would indicate that the offshore waters are more polluted than the near shore areas in Port Dickson.
Studies by Zakaria et al. (2002) on the distribution of PAHs in sediments from rivers and estuaries in Malaysia (sampling was conducted in the West coast of peninsular Malaysia and the Straits of Melacca) found concentration of PAHs (3-7 rings) ranging between 4 to 924 ppb. The study also identified two major routes of petrogenic PAH pollution input into the aquatic environment which is (1) spillage and dumping of waste crankcase oil and (2) leakage of crankcase oils from vehicles onto road surface subsequently washed out by street runoff.
Hydrocarbon studies in the South China Sea was conducted in the coastal waters off Terengganu by Law and Rahimi (1986), coastal waters off Pahang by Law and Zulkifli (1987), Sarawak coastal waters by Law and Libis (1988) and Coastal waters off Sabah by Law (1990). The results are shown in Table 1 .
In the South China Sea, studies on dibenzothiophene which is a heterocyclic sulfur polynuclear aromatic compound by Yang et al. (1998) on sediments from 22 different sampling sites found the concentrations ranging from 11 to 66 ppb dry sediment in all sampling locations. Present study also found that the concentration were higher in nearshore sediment samples where the probable source pathways include terrestrial runoff, crude oil pollution and input from airborne particulates formed from combustion process. It is interesting to note that some of the stations are located adjacent to the coastal waters of Sarawak and Sabah thus, the researcher indirectly implies that the probable source pathway of the pollution is from East Malaysia.
Tributyl-tin (TBT)
Reports and studies on the contamination of butyltin compounds in the Melacca
Straits and the South China Sea are few and far apart. In Thailand, a study
by Kan-Atireklap et al. (1997) on green mussel
(Perna viridis) conducted in the Gulf of Thailand (which is a part of
the South China Sea) and the Andaman Sea (adjacent to the Straits of Melacca)
indicated that butyltin contamination was widespread, particularly in high boating
areas and in coastal aquaculture facilities (Table 2). The
concentration of butyltin compounds (BTs) ranges from <3-45 ppb for monobutyltin
(MBT), 1-80 ppb for dibutyltin (DBT) and 3-680 ppb for TBT.
Pesticides
Organochloride compounds were widely used in rapidly developing countries
in South East Asia for agriculture, pest control and for public health purposes.
From one of the earliest study in the Straits of Melacca by Sivalingam
et al. (1982), pp’-DDE pollution in mussel tissue from six stations
on the Penang Island ranged from 3.7 to 17.4 ppb (dry weight basis) and a concentration
of 7.11 to 8.12 ppb dry weight basis found in mussels from three stations in
Singapore (Table 3). The same study also detected 99.9 to
599.9 ppb (dry weight basis) and between 139.8 to 256.4 ppb of polychlorinated
biphenyls (PCBs) in green mussel samples from Penang and Singapore, respectively.
Present study also found that no other organic chlorinated hydrocarbon compounds
were detectable in the marine bivalve at either location. The researchers concluded
that tropical features result in high rate of degradation, purification or geographical
separation of these compounds rendering them undetectable.
In Thailand, a study by Kan-Atireklap et al. (1997) on green mussel (Perna viridis) conducted in the Gulf of Thailand and the Andaman Sea indicated that organochloride contamination was widespread, particularly in coastal aquaculture facilities (Table 3).
| Table 1: | Detection of hydrocarbons in Malaysian waters from 1980 to 2002 |
| Table 2: | Tributyl-tin (TBT) detection in green mussel in Thailand waters |
Among the organochloride residues examined, dichlorodiphenyltrichloroethane compounds (DDTs) were found to be the highest (1.2-38 ppb), followed by PCBs (0.01-20 ppb), chlordane compounds (CHLs) (0.25-5.9 ppb), hexachlorocyclohexane (HCHs) (<0.01-0.33 ppb) and hexachlorobenzene (HCB) (<0.01-0.12 ppb) (Table 3).
| Table 3: | Detection of pesticides in Malaysian waters from 1982 to 2000 |
DISCUSSION
The existing environmental issues and potential environment threats demand serious conditions. The pollution levels detected in studies compiled for this paper indicate that pollution will play a major role in the in the future and pollution management in the Straits of Melacca and South China Sea must be address. Although, pollution figures are still within limits, we must ensure that the resources will be taken care of for the future generations. Management of the Straits of Melacca and South China Sea resources has to address four main problem areas: (1) minimizing pollution; (2) enforcement of regulations for controlling pollution from all sources; (3) oil spill prevention and control and (4) marine environment protection, rehabilitation and compensation for damages.
From the studies reviewed, it can be said that the level of persistent organic chemicals in the Malaysian waters are still at the acceptable level and comparable to results in other Southeast Asia countries. It must be noted though that there studies reviewed were from the early 80’s so they may not actually reflect the current situation in the Malaysian coastal waters. Today, it is believe that the level of persistent organic chemicals in Malaysia and Southeast Asia water had been increased because of the rapid population growth and urbanization. From the studies reviewed it may be conclude that the majority of persistent organic chemicals pollution that occurs in Malaysia and this region waters originates from urbanization (sewage waters, industrial), agricultural activities (nutrients, pesticide and sediment) and transporting (boating and shipping). According to Anonymous (1990), the primary sources of marine pollution are found on the land, causing pollution in coastal fishing areas.
Hydrocarbons
Present review clearly shows that the main hydrocarbons detected in
Malaysia waters are mainly Polycyclic Aromatic Hydrocarbons (PAH). The
results show there are higher concentration of PAHs in the urbanization
and industrialized locations. Petrogenic input (used crankcase oil and
input from street dust and traffic sources) is a major control on the
PAHs contamination in Malaysia and it maybe concluded that the Malaysian
aquatic environments have been more heavily impacted by petrogenic input
than have those of the industrialized countries. The concentrations of
hydrocarbons are widely range from urban rivers to open ocean. From the
study reviewed clearly showed that concentrations of hydrocarbons in environmental
samples (sediments, waters and mussels) collected near major townships
are generally higher than those rural samples.
One of major threats of hydrocarbons pollution in Malaysia waters comes from oil spilling from offshore oil production and shipping. Moradi (1994) stated that the single largest contributor of oil spill from transportation activities has been identified to be from tanker operations associated with ballasting the tanks for the return voyage from ports of discharge. It may conclude that the hydrocarbons concentration mainly PAHs in Malaysia waters is still low- moderate compared with other more industrialized areas of the world (developed countries) such as United States, Canada, Europe, Australia and Japan (Zakaria et al., 2002).
However, more documented hydrocarbons research needed in this region because the concentrations and distributions of hydrocarbons maybe influenced by the climatic characteristics (dilution by the rainstorm). Therefore, the mixing and magnitude of sources and transport mechanisms of hydrocarbons in Malaysia and Southeast Asia maybe different as compared to other regions found at higher latitudes (Zakaria et al., 2002).
Tributyl-tin (TBT)
There is still lack of information and documented research on TBT pollution
in Malaysia and Southeast Asian countries. It is believed that the level of
TBT pollution in this region waters has been increased because an increasing
of waters activities such as fisheries, boating and shipping activities. TBT
is toxic at nanogram per liter level (Champ and Seligman,
1996). It may be concluded that shipping and boating is the main source
of TBT pollution in this region especially in coastal aquaculture facilities
and high boating areas. In these facilities, TBT was used as antifouling agent
in paints applied on boats and fish net, lumber preservatives and slimicides
in cooling system. TBT based antifouling paints are still being used on larger
vessels especially commercial vessels which consume about 75% of total TBT used
as antifouling paints (Kan-Atireklap et al., 1997).
More research is needed in this area to know current situation of this pollution.
Pesticides
Relatively high levels of pesticides found in the agricultural and urbanization
area in Malaysia and Southeast Asia especially organochlorine pesticides. DDT
is one of the most organochlorine pesticides used in this region since 1950.
DDT has been extensively used as malaria repellent and as an agricultural pesticides
until the use has been successfully limited and was finally banned for all applications
in 1994 (Anonymous, 1997). In spite of this, persistent
organochlorine pesticides are still circulating in Malaysia and Southeast Asia
ecosystem that are simultaneously being exposed to increasing pollution loads
resulting from rapid population growth, urbanization and agroindustrial development.
Some research has been conducted on organochlorine pesticides in Malaysia and
Thailand from 1982 to 2000 showed that various concentration of organochlorine
pesticides and its metabolites have been found in various environmental and
biological samples. The concentration of DDT in Malaysia coastal waters is still
low-medium, ranging from 0-2.2 ppb in 1999 compared to Thailand and other Southeast
Asia country. It appears that concentration of DDT declined in Southeast Asia
coastal waters after the restriction introduced. However, Chan
et al. (1999) reported worring fact of DDT and DDE levels were high
in certain isolated areas of South China Sea suggesting either illegal dumping
or local industrial use.
| Table 4: | Nutrient detection in Malaysia waters from 1990-2002 |
Concentrations of heptachlor were relatively low in comparison to overseas data ranging from <0.131`4 ppb (Hossain et al., 1999) -1.26 ppb (Wood et al., 1999). The detection of some organochlorine pesticides isomers (Table 3) in some locations may suggest usage of those pesticides in Malaysia. However it may be concluded that the level of pesticides in Malaysia waters in the present study was much lower than other Asian countries such as India and Indonesia.
The spatial differences in pesticides residue levels in some of environmental samples collected from several locations along coastal waters of Malaysia suggested that pesticides especially organochlorine pesticides were widely used in Malaysia. Although an organochlorine pesticide such as DDT was banned in Malaysia, their current sources still remain in the aquatic environment. When compared to other data, residues level of organochlorine pesticides and some others pesticides in Malaysia’s marine environment have been declining.
Nutrients
Generally the level of orthophosphate in Straits of Melacca were low ranging
from 0.06-0.72 μM between 1990-2000 (Table 4). Low orthophosphate
levels were found in the surface water and then increased rapidly with increasing
depth (Tengku Rozaini, 1999). There was no distinct variation
of ammonium, nitrite and nitrate level in Straits of Melacca. However, further
studies to trace the source and the impact of this rich nutrients and the impact
of this rich nutrients on ecological of the Straits of Melacca.
CONCLUSION
In summation, level of some Persistent Organic Chemicals (POCs) is still low compared with other Southeast Asia countries and the level of Persistent Organic Chemicals (POCs) in this region still at the medium level compared with more urbanized and industrialized region in the world. However, continuous monitoring and investigations on the level and of the Persistent Organic Chemicals (POCs) are needed in Malaysia. Transboundary pollution potential should be taken as an important consideration in any development project especially in Southeast Asia.