Occurrence and ecological risk assessment of antibiotic residues in urban wastewater discharged into the coastal environment of the Persian Gulf (the case of Bandar Abbas).

This is the first attempt to detect antibiotic residues released into the Persian Gulf marine environment. In particular, this study quantifies and assesses the ecological risks of amoxicillin (AMX) and azithromycin (AZM) residues in wastewater outfalls from Bandar Abbas, one of the major coastal cities in southern Iran. The wastewater effluent samples were collected from two main wastewater discharging stations, Gursuzan and Suru, between December 2020 and February 2021. High-performance liquid chromatography (HPLC) analysis revealed the average concentration (± 95% CL) of AMX were 460 ± 230.0 µg L-1 and 280 ± 100.6 µg L-1 in Gursuzan and Suru stations. Mean AZM concentrations were also 264 ± 10.59 µg L-1 and 295 ± 89.75 µg L-1 in these stations, respectively. Pooled data indicated that there are 335.17 ± 105.11 and 288.17 ± 37.94 µg of AMX and AZM residues in the wastewater per liter. The values of potential ecological risk, hazard quotient (HQ), were extensively above 10 (AMX: 90,586.5 and AZM: 5541.7) which suggest that these substances have a high health risk for the ecosystem and public. Given that Bandar Abbas wastewater treatment plant (WWTP) outlets are discharged at about 500 to 700 L s-1, the daily maximum potential AMX and AZM released were estimated to be 19.05 (± 0.283) × 103 and 14.74 (± 0.113) × 103 g day-1, respectively (α = 0.05). Our findings show that there is a concerning volume of antibiotic residues released into the northern Persian Gulf, and hence urgent policies and actions are necessary to reduce this pollution.

Source apportionment and health risk assessment of polycyclic aromatic hydrocarbons (PAHs) in the coastal ecosystem of the Brunei Bay, Brunei.

Pollution characteristics and associated ecological risks of PAHs in sediments from Brunei Bay, Brunei were investigated. The concentrations of ∑16 PAHs ranged from 826.7 to 2955.3 µg kg-1, indicating moderate to high level of pollution. Source apportionment of PAHs by molecular isomeric ratios and positive matrix factorization model indicated impact of potential anthropogenic PAH sources including combustion of biomass and fossil fuels. The data indicated relatively no significant ecotoxicological risk for most of PAH compounds. To estimate the individual c-PAH toxicity, the toxic equivalent quantity (c-TEQ) was calculated. Results of the TEQ analysis showed that BaP followed by DBA and BaA are the most carcinogenic of PAHs examined in the study area. The evaluation of human health risk of PAHs revealed that the cancer risk of PAHs for adults and children was higher than the USEPA threshold (<1E-06) and lower than 1E-3, implying low to moderate risk.

The impact assessment of desalination plant discharges on heavy metal pollution in the coastal sediments of the Persian Gulf.

In recent decades the development of desalination plants (DPs) for desalination of seawater has increased dramatically, while little attention has been paid to the effects of this activity on the accumulation of heavy metals (HMs) in the sediments of affected ecosystems. The present study was implemented to evaluate (1) heavy metal accumulation in sediments impacted by DPs discharges, (2) spatial and temporal changes of HMs and the contamination degree by different types of pollution indexes (single and integrated indices), and (3) ecological risk assessment of cadmium (Cd), lead (Pb), zinc (Zn) and copper (Cu) in sediments affected by DPs discharges. A total of 288 sediment samples were collected seasonally at 24 stations from November 2019 to October 2020. Analysis of HMs concentrations in sediments near the desalination plant discharge provided evidence of local contamination. Maximum concentration of Cu and Pb elements were found in sediments near the desalination plant discharge point. Hierarchical cluster analysis revealed clear segregation of stations impacted by desalination plant discharges and away from discharges. The values of PLI index in sediments of all sampling stations were < 1, indicating that there was no metal pollution by this index. The potential ecological risk index (PERI) ranged from 5.33 ± 0.51 to 11.81 ± 4.98 in sampling sediments and were classified as "low potential ecological risk". These results demonstrate that the DPs discharge increased HMs concentrations in the sediments in close proximity to outlets. The necessary and practical regulations and policies regarding the rejection of the DPs discharge and disposal of chemical compounds must be implemented and enforced.

Are the tourist beaches safe for swimming? A case study of health risks of polycyclic aromatic hydrocarbons (PAHs) in tourist beaches of Bushehr City.

The aims of the present research were to evaluate the health risk of long-term exposure to polycyclic aromatic hydrocarbons (PAHs) concerning the human, ecotoxicological risk for marine biota, and identify their possible sources. Surface sediment bioassay samples were collected from 15 stations of tourist beaches surrounding Bushehr City and analyzed using high performance liquid chromatography (HPLC). The results indicated the concentrations of ∑PAH ranged from 193.5 to 725.5 ng g-1 with mean value of 351.1 ± 155.2 ng g-1, which could be considered as moderate level of pollution. Measured levels of PAH in sediments were compared with sediment quality guidelines (SQGs), indicating low to medium ecotoxicological risk on marine organisms. Moreover, mean ERM quotient (M-ERM-Q) and mean PEL quotient (M-PEL-Q) were implemented, demonstrating potentially biological adverse effects. A preliminary evaluation of human health risk using incremental lifetime cancer risk (ILCR) and toxic equivalent quotient (TEQcarc) indicated that PAH-contaminated sediment in some stations of touristic beaches of Bushehr City would induce potential carcinogenic effects especially for children. Composition and diagnostic analysis indicated that PAHs originated from both pyrogenic and petrogenic, with higher portion of incomplete combustion PAHs.

Monitoring of linear alkyl benzenes (LABs) in riverine and estuarine sediments in Malaysia.

The aim of this a pioneering research is to investigate linear alkylbenzenes (LABs) as biomarkers of sewage pollution in sediments collected from four rivers and estuaries of the south and east of Peninsular Malaysia. The sediment samples went through soxhlet extraction, two-step column chromatography purification, fractionation and gas chromatography-mass spectrometry (GC-MS) analysis. Principal component analysis (PCA) with multivariate linear regression (MLR) was used as well for source apportionment of LABs. The results of this study showed that total LAB concentration was 36-1196 ng g-1dw. The internal to external isomer ratios (I/E ratio) of LABs were from 0.56 to 3.12 indicated release of raw sewage and primary and secondary effluents into the environment of south and east of Peninsular Malaysia. Our research supported that continuous monitoring of sewage pollution to limit the environmental pollution in riverine and estuarine ecosystem.

Occurrence and characterization of microplastics in white shrimp, Metapenaeus affinis, living in a habitat highly affected by anthropogenic pressures, northwest Persian Gulf.

Microplastics (MPs) are a modern societal concern and recognized as a growing environmental hazard by careless disposal. This study aimed to assess the MPs content in white shrimp (Metapenaeus affinis) inhabiting in a natural habitat affected by high anthropogenic pressures, and recognize if the shrimp could be a suitable bioindicator for MPs pollution. To assess spatial changes of MPs presence in shrimps, sampling was carried out by a trawl net from 13 stations across the entire Musa Bay. Tissues of shrimps were examined for MPs following floatation, digestion, microscopic observation and identified by Confocal Raman Spectroscopy. MPs were observed in the shrimps of all stations. The average MPs abundance was 1.02 items/g of digestive tissues. About 37% of recorded MPs in M. affinis samples exceeding 500 µm that could be related to surface area and stickiness as notable controls beyond ingestion. The dominant shape of MPs was fiber, followed by film. Five different colors were recorded in tissues of M. affinis samples, and the white/transparent MPs were the most abundant, followed by blue and black. In addition, a wide range of recorded colors of MPs in the study area could suggest a variety of sources of MPs. Confocal Raman Spectroscopy confirmed that polyethylene terephthalate (46%), polypropylene (27%) and polystyrene (27%) were dominant polymers. As the average annually consumption of shrimp in the region is 2.3 g/person/day, therefore each person could consume 857 MPs per year. In conclusion, the results of this research provide a detailed and useful information for a better understanding of MPs contamination in the region and suggest Jinga shrimp as a suitable species for monitoring MPs in marine ecosystems.

Implications of anthropogenic effects on the coastal environment of Northern Persian Gulf, using jinga shrimp (Metapenaeus affinis) as indicator.

The distribution and sources of PAHs in jinga shrimp (Metapenaeus affinis), and human health risks due to consumption was evaluated in collected samples from the Musa Bay, Persian Gulf. The total concentration of PAHs (∑16PAHs) ranged from 10 to 144 µg kg-1 dry weight, indicating low to moderate level of pollution. The PAHs were dominated by three- (41%) and two-ring (38%) compounds. Source identification analyses indicated the PAH pollution mostly originated from petroleum inputs. A preliminary evaluation of human health risk using chronic daily intake, hazard index, benzo[a]pyrene-equivalent (BaPeq) concentration (PEC) as well as the incremental life cancer risk and non-cancer risk assessment suggest low potential health risk for consumers of the Metapenaeus affinis. However, the results indicate minimal risks associated with the intake of PAHs via shrimp consumption, but long-term monitoring is required to evaluate the changes in ecological and human health impacts of contaminants in the region. MAIN FINDING: PAHs in Metapenaeus affinis from Musa bay, which influenced by anthropogenic activities were low to moderate level of pollution. Human health risk indicates low potential health risk for consumers.

Microplastic pollution as a grand challenge in marine research: A closer look at their adverse impacts on the immune and reproductive systems.

Microplastic (MP) pollution of the marine environment is now a growing global concern posing a threat to a variety of species through the ingestion and transfer within food webs. This is considered a potential toxicological threat to marine species due to the chemical additives used to make many plastic products, or the persistent organic pollutants that may accumulate on them while residing in the environment. While the presence of MPs in the marine environment is widely documented, there are no other review articles providing a summary of published effect studies of MPs on the immune and reproductive systems of marine species. This manuscript reviews reproductive and immune-system changes in response to MPs in 7 and 9 species, respectively. Some species such as Mytilus galloprovincialis and oyster Crassostrea gigas were investigated in multiple papers. Most studies have been conducted on invertebrates, and only 3 studies have been performed on vertebrates, with exposure times ranging between 30 min and 60 days. A review of the literature revealed that the most common MPs types studied in relation to adverse impacts on immune system and reproductive success in marine species were polystyrene (PS) and polyethylene (PE). The immune system's responses to MPs exposure varied depending on the species, with altered organismal defense mechanisms and neutrophil function observed in fish and changes in lysosomal membrane stability and apoptotic-like nuclear alterations in phagocytes reported in invertebrate species. Reproductive responses to MPs exposure, varied depending on species, but included significant reduction in gamete and oocyte quality, fecundity, sperm swimming speed, and quality of offspring. The lack of published data means that developing a clear understanding of the impact across taxonomic groups with different feeding and behavioral traits is often difficult. Further work is required to better understand the risk MPs pose to the immune and reproductive systems of marine species in order to fully evaluate the impact these ubiquitous pollutants are having on marine ecosystems and the associated goods and services they provide.

Linear alkylbenzenes in surface sediments of an estuarine and marine environment in peninsular Malaysia.

Linear alkylbenzenes were determined in the surface sediments of Muar River and Pulau Merambong, Peninsular Malaysia. The concentrations ranged from 87.4 ng g-1 to 188.1 ng g-1 and from 67.4 ng g-1 to 98.2 ng g-1 of dry weight, respectively. The composition profiles of LABs were characterized, and sewage treatment levels were identified. The ratios of internal to external isomers (I/E ratios) of the linear alkylbenzenes in Muar River sediments ranged from 1.7 to 2.2, whereas those of Pulau Merambong sediments ranged from 1.6 to 1.7. The calculated LAB ratios indicated that the study areas received primary and secondary sewage effluents. The degradation of linear alkylbenzenes in Muar River ranged from 33% to 43%, and that in Pulau Merambong ranged from 33% to 34%. The higher degradation indices in Muar River are a sign of improvement in wastewater treatment.

Prevention is better than cure: Persian Gulf biodiversity vulnerability to the impacts of desalination plants.

Due to extremely high rates of evaporation and low precipitation in the Persian Gulf, discharges from desalination plants (DPs) can lead to ecological stresses by increasing water temperatures, salinities, and heavy metal concentrations, as well as decreasing dissolved oxygen levels. We discuss the potential ecological impacts of DPs on marine organisms and propose mitigating measures to reduce the problems induced by DPs discharges. The daily capacity of DPs in the Persian Gulf exceeds 11 million m3 per day, which is approximately half of global daily freshwater production; multistage flash distillation (MSF) is the dominant desalination process. Results from field and laboratory studies indicate that there are potentially serious and chronic threats to marine communities following exposure to DP discharges, especially within the zoobenthos, echinodermata, seagrasses, and coral reefs. DP discharges can lead to decreases in sensitive species, plankton abundance, hard substrate epifauna, and growth rates of seagrasses. However, the broad applicability of any one of these impacts is currently hard to scale because of the limited number of studies that have been conducted to assess the ecological impacts of DP discharge on Persian Gulf organisms. Even so, available data suggest that appropriately sited, designed, and operated DPs combined with current developments in impingement and entrainment reduction technology can mitigate many of the negative environmental impacts of DPs.

Seasonal variability of anthropogenic indices of PAHs in sediment from the Kuala Selangor River, west coast Peninsular Malaysia.

Rapid increase in industrialization and urbanization in the west coast of Peninsular Malaysia has led to the intense release of petroleum and products of petroleum into the environment. Surface sediment samples were collected from the Selangor River in the west coast of Peninsular Malaysia during four climatic seasons and analyzed for PAHs and biomarkers (hopanes). Sediments were soxhlet extracted and further purified and fractionated through first and second step column chromatography. A gas chromatography-mass spectrometry (GC-MS) was used for analysis of PAHs and hopanes fractions. The average concentrations of total PAHs ranged from 219.7 to 672.3 ng g-1 dw. The highest concentrations of PAHs were detected at 964.7 ng g-1 dw in station S5 in the mouth of the Selangor River during the wet inter-monsoonal season. Both pyrogenic and petrogenic PAHs were detected in the sediments with a predominance of the former. The composition of hopanes was homogeneous showing that petroleum hydrocarbons share an identical source in the study area. Diagnostic ratios of hopanes indicated that some of the sediment samples carry the crankcase oil signature.

Distribution, source apportionment and health risk assessment of polycyclic aromatic hydrocarbons (PAHs) in intertidal sediment of Asaluyeh, Persian Gulf.

Surface sediment samples were collected from intertidal zone of Asaluyeh, Persian Gulf, to investigate distribution, sources and health risk of sixteen polycyclic aromatic hydrocarbons (PAHs). Total PAH concentrations ranged from 1.8 to 81.2 µg kg-1 dry weight, which can be categorized as low level of pollution. Qualitative and quantitative assessments showed that PAHs originated from both petrogenic and pyrogenic sources with slight pyrogenic dominance. Source apportionment using principal component analysis indicated that the main sources of PAHs were fossil fuel combustion (33.59%), traffic-related PAHs (32.77%), biomass and coal combustion (18.54%) and petrogenic PAHs (9.31%). According to the results from the sediment quality guidelines, mean effects range-median quotient (M-ERM-Q) and benzo[a]pyrene toxic equivalents (BaPeq), low negative ecological risks related to PAH compounds would occur in the intertidal zone of Asaluyeh. The total benzo[a]pyrene (BaP) toxic equivalent quotient (TEQcarc) for carcinogenic compounds ranged from 0.01 to 7 µg kg-1-BaPeq, indicating low carcinogenic risk. The human health risk assessment of PAH compounds via ingestion and dermal pathways suggests low and moderate potential risk to human health, respectively.

Polycyclic aromatic hydrocarbons (PAHs) in sediment and sea urchin (Echinometra mathaei) from the intertidal ecosystem of the northern Persian Gulf: Distribution, sources, and bioavailability.

The distribution, sources and bioavailability of polycyclic aromatic hydrocarbons (PAHs) in sediment and sea urchin (Echinometra mathaei) from the intertidal zone of the northern Persian Gulf were investigated. Total PAH concentrations varied from 12.8 to 81.25 and from 16.7 to 35 µgKg-1 dry weight in sediment and Echinometra mathaei, respectively. The PAH concentrations can be classified as low. Source identification and apportionment using diagnostic ratios and principal component analysis demonstrate that the combustion of fossil fuels, road traffic, combustion of natural gas and biomass, and oil spill could be considered as the main sources of PAH contamination. The first PAH biota-sediment accumulation factors (BSAF) data from sediment to Echinometra mathaei in the intertidal zone of the northern Persian Gulf were calculated, indicating accumulation of both lower and higher molecular weight PAHs, with a preferential accumulation of lower molecular weight PAHs.

Ecotoxicological and Health Risk Assessment of Polycyclic Aromatic Hydrocarbons (PAHs) in Short-Neck Clam (Paphia undulata) and Contaminated Sediments in Malacca Strait, Malaysia.

The distribution, sources, and human health risk assessment of polycyclic aromatic hydrocarbons (PAHs) in surface sediment and the edible tissue of short-neck clam (Paphia undulata) from mudflat ecosystem in the west coast of Malaysia were investigated. The concentrations of ∑16 PAHs varied from 347.05 to 6207.5 and 179.32 to 1657.5 ng g-1 in sediment and short-neck clam samples, respectively. The calculations of mean PEL quotients (mean-PELQs) showed that the ecological risk of PAHs in the sediment samples was low to moderate-high level, whereas the total health risk through ingestion and dermal contact was considerably high. The PAHs biota sediment accumulation factors data for short-neck clam were obtained in this study, indicating a preferential accumulation of lower molecular weight PAHs. The source apportionment of PAHs in sediment using positive matrix factorization model indicated that the highest contribution to the PAHs was from diesel emissions (30.38%) followed by oil and oil derivate and incomplete coal combustion (23.06%), vehicular emissions (16.43%), wood combustion (15.93%), and natural gas combustion (14.2%). A preliminary evaluation of human health risk using chronic daily intake, hazard index, benzo[a]pyrene-equivalent (BaPeq) concentration, and the incremental lifetime cancer risk indicated that PAHs in short-neck clam would induce potential carcinogenic effects in the consumers.

Bioavailability of polycyclic aromatic hydrocarbons (PAHs) to short-neck clam (Paphia undulata) from sediment matrices in mudflat ecosystem of the west coast of Peninsular Malaysia.

The bioaccumulation and bioavailability of polycyclic aromatic hydrocarbons (PAHs) were characterized in sediment and Paphia undulata (short-neck clam) from six mudflat areas in the west coasts of Peninsular Malaysia. The concentrations of total PAHs varied from 357.1 to 6257.1 and 179.9 ± 7.6 to 1657.5 ± 53.9 ng g -1 dry weight in sediment and short-neck clam samples, respectively. PAHs can be classified as moderate to very high level of pollution in sediments and moderate to high level of pollution in short-neck clams. The diagnostic ratios of individual PAHs and principal component analysis indicate both petrogenic and pyrogenic sources with significant dominance of pyrogenic source. The first PAHs biota-sediment accumulation factors and relative biota-sediment accumulation factors data for short-neck clam were obtained in this study, indicating a preferential accumulation of lower molecular weight PAHs. Evaluation of PAH levels in sediments and short-neck clams indicates that short-neck clam could be introduced as a good biomonitor in mudflats. The results also demonstrated that under environmental conditions, the sedimentary load of hydrocarbons appears to be one of the factors controlling their bioavailability to biota.

Evaluation of distribution and sources of sewage molecular marker (LABs) in selected rivers and estuaries of Peninsular Malaysia.

This is the first extensive report on linear alkylbenzenes (LABs) as sewage molecular markers in surface sediments collected from the Perlis, Kedah, Merbok, Prai, and Perak Rivers and Estuaries in the west of Peninsular Malaysia. Sediment samples were extracted, fractionated, and analyzed using gas chromatography mass spectrometry (GC-MS). The concentrations of total LABs ranged from 68 to 154 (Perlis River), 103 to 314 (Kedah River), 242 to 1062 (Merbok River), 1985 to 2910 (Prai River), and 217 to 329 ng g(-1) (Perak River) dry weight (dw). The highest levels of LABs were found at PI3 (Prai Estuary) due to the rapid industrialization and population growth in this region, while the lowest concentrations of LABs were found at PS1 (upstream of Perlis River). The LABs ratio of internal to external isomers (I/E) in this study ranged from 0.56 at KH1 (upstream of Kedah River) to 1.35 at MK3 (Merbok Estuary) indicating that the rivers receive raw sewage and primary treatment effluents in the study area. In general, the results of this paper highlighted the necessity of continuation of water treatment system improvement in Malaysia.

Anthropogenic waste indicators (AWIs), particularly PAHs and LABs, in Malaysian sediments: Application of aquatic environment for identifying anthropogenic pollution.

Polycyclic aromatic hydrocarbons (PAHs) and linear alkylbenzenes (LABs) were used as anthropogenic markers of organic chemical pollution of sediments in the Selangor River, Peninsular Malaysia. This study was conducted on sediment samples from the beginning of the estuary to the upstream river during dry and rainy seasons. The concentrations of Æ©PAHs and Æ©LABs ranged from 203 to 964 and from 23 to 113 ng g(-1) dry weight (dw), respectively. In particular, the Selangor River was found to have higher sedimentary levels of PAHs and LABs during the wet season than in the dry season, which was primarily associated with the intensity of domestic wastewater discharge and high amounts of urban runoff washing the pollutants from the surrounding area. The concentrations of the toxic contaminants were determined according to the Sediment Quality Guidelines (SQGs). The PAH levels in the Selangor River did not exceed the SQGs, for example, the effects range low (ERL) value, indicating that they cannot exert adverse biological effects.

Baseline distribution and sources of linear alkyl benzenes (LABs) in surface sediments from Brunei Bay, Brunei.

Sewage pollution is one of major concerns of coastal and shoreline settlements in Southeast Asia, especially Brunei. The distribution and sources of LABs as sewage molecular markers were evaluated in surface sediments collected from Brunei Bay. The samples were extracted, fractionated and analyzed using gas chromatography- mass spectrometry (GC-MS). LABs concentrations ranged from 7.1 to 41.3 ng g(-1) dry weight (dw) in surficial sediments from Brunei Bay. The study results showed LABs concentrations variably due to the LABs intensity and anthropogenic influence along Brunei Bay in recent years. The ratio of Internal to External isomers (I/E ratio) of LABs in sediment samples from Brunei Bay ranged from 0.56 to 2.17 along Brunei Bay stations, indicating that the study areas were receiving primary and secondary effluents. This is the first study carried out to assess the distribution and sources of LABs in surface sediments from Brunei Bay, Brunei.

Distributions and source apportionment of sediment-associated polycyclic aromatic hydrocarbons (PAHs) and hopanes in rivers and estuaries of Peninsular Malaysia.

In this study, the distributions and sources of sediment-associated polycyclic aromatic hydrocarbons (PAHs) and hopanes in the Malaysian rivers and estuaries were evaluated. The concentrations of 16 USEPA PAHs varied from 225.5 to 293.9 (Perlis River), 195.2 to 481.2 (Kedah River), 791.2 to 1995.4 (Merbok River), 231.2 to 426.7 (Perak River), and 3803.2 to 7442.7 ng g(-1) (Klang River) dry weight. PAHs can be classified as moderate in the Perlis, Kedah, and Perak Rivers, moderate to high in the Merbok River, and high to very high in the Klang River. The comparison of PAHs with sediment quality guidelines (SQGs) indicates that occasionally adverse biological effects may occur from total PAHs, low molecular weight (LMW), and high molecular weight (HMW) PAHs at stations 1, 2, and 3 of the Klang River and from total PAHs at station 2 of the Merbok River. The diagnostic ratios of individual PAHs indicate both petrogenic and pyrogenic origin PAHs with significant dominance of pyrogenic sources in the study areas. The results suggest that Malaysian sediments had hopane ratios (C29/C30) similar to MECO suggesting MECO as a major source of the petroleum hydrocarbons found in the sediments, which is consistent with results reported in previous studies. These findings demonstrate that effective and improved environmental regulations in Malaysia have shifted the source of petroleum hydrocarbons from petrogenic to pyrogenic origin.

Baseline distributions and sources of Polycyclic Aromatic Hydrocarbons (PAHs) in the surface sediments from the Prai and Malacca Rivers, Peninsular Malaysia.

In this study, the surface sediments of the Malacca and Prai Rivers were analyzed to identify the distributions, and sources of Polycyclic Aromatic Hydrocarbons (PAHs). The total PAH concentrations varied from 716 to 1210 and 1102 to 7938 ng g(-1)dw in the sediments of the Malacca and Prai Rivers, respectively. The PAH concentrations can be classified as moderate and high level of pollution in the sediments of the Malacca and Prai Rivers, respectively. The comparison of PAHs with the Sediment Quality Guidelines (SQGs) indicates that the PAHs in the sediments of the Malacca and Prai Rivers may have the potential to cause adverse toxicity effects on the sampled ecosystems. The diagnostic ratios of individual PAHs indicate both petrogenic- and pyrogenic-origin PAHs with dominance of pyrogenic source in both rivers. These findings demonstrate that the environmental regulations in Malaysia have effectively reduced the input of petrogenic petroleum hydrocarbons into rivers.