Polycyclic Aromatic Hydrocarbons in Sediment and Health Risk of Fish, Crab and Shrimp Around Atlas Cove, Nigeria

Background. Polycyclic aromatic hydrocarbons (PAHs) are toxic contaminants and pose health risks to humans and the ecosystem due to their persistence in the environment. Objectives. This study determined the concentrations of PAHs in sediment, two species of fish (Drepane africana and Pomadasys jubelini), crabs (Callinectes amnicola) and shrimps (Penaeus notialis) around the Atlas Cove jetty, Lagos, Nigeria. Methods. Polycyclic aromatic hydrocarbons were extracted from fish, shrimp, and crabs that were purchased from local fishermen. Sediments were collected at five locations impacted by ship movement and cargo offloading around the Atlas Cove jetty during the period of June to August 2016, using standard methods. Potential toxicity of PAHs in the sediments on the surrounding aquatic organisms was assessed. The PAHs were analyzed using gas chromatography-mass spectrometry. Human health risk assessment was calculated from biota using dietary daily intake and carcinogenic potencies of individual PAH concentrations. Results. A total of 17 PAH congeners were detected in sediment samples and ten were detected in biota samples. Concentrations of total PAHs obtained in sediment and fish samples ranged from 2.15 - 36.46 mg/kg and 11.89 - 71.06 mg/kg, respectively. The total PAHs concentration pattern follow the order of P. notialis > C. amnicola > P. jubelini (whole) > D. africana (whole) > D. africana (fillet) > P. jubelini (fillet) > sediment. Concentrations of total PAHs were higher in whole fish than in fillet samples (muscle) in both fish species. High values of PAHs were recorded in the dietary intake (0.10 - 2.33 mg/kg body weight/day) of the organisms. Toxic equivalent quotient values (0.01 to 0.10 mg/kg) were observed to be higher than the screening values (0.0014 to 0.0599 mg/kg). In the muscle of Drepane africana and Pomadasys jubelini, splitting and atrophy of the muscle bundles were observed. Conclusions. The concentrations of PAHs in analyzed sediment and organisms were higher than the maximum permissible limit of the United State Environmental Protection Agency (USEPA). Most of the detected PAHs were of petrogenic origin, which is an indication that anthropogenic activities were influencing PAH concentrations. Competing Interests. The authors declare no competing financial interests.


Introduction
Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in the environment and cause adverse environmental effects. The exploration and exploitation of crude oil and gas resources are a major source of PAHs. Even though improved technologies have been introduced in the petroleum industry, accidents continue to occur, resulting in hydrocarbon pollution of the environment (both land and water) in most oil producing countries, including Nigeria. 1 Oil from the petroleum industry enters the aquatic environment through gas flaring, disposal of used lubrication oils, washings from oil tanks, leakage from marine vessels, erosion and run off from crude oil polluted lands, refinery effluents, and ruptures from poorly maintained flow lines/ installations. Leakage of oil into the environment could be due to sabotage or maintenance and engineering errors. Upon entry into the aquatic environment, the fraction either mixes with water or sinks into the sediment, causing severe damage to benthic organisms. Hydrocarbon pollution impacts fish, crustaceans and mollusks with objectionable odor or flavor, reducing their market value and acceptability. 1 Major routes of PAH exposure in fish are ingestion of contaminated food and diffusion of water across their gills and skin. 2 The lipophilic nature and high chemical stability of PAHs make it easier to penetrate biological membranes and accumulate in the fatty tissues of organisms following their uptake. Polycyclic aromatic hydrocarbons have been reported to be readily absorbed by fish and other aquatic organisms on Research exposure to contaminated materials, thereby reaching elevated levels over that of the surrounding medium. 2 The bioaccumulation pattern of PAHs vary in aquatic organisms depending on the trophic levels they occupy, however, the organic PAHs physiological burden is dependent on the biotransformative effect of the organisms. 3 Macrobenthic invertebrates (shrimps, crayfish, mollusks and crabs) are an important and integral part of the aquatic ecosystem and thus reflect any negative effects caused by pollution in the community structure which can affect trophic relationships. 4 Fish have been reported to be the most sensitive living organism to trace concentrations of toxicants in aquatic habitats. 5 Shrimps, crabs and fishes are therefore good indicators of pollution in coastal waters and have been used extensively for environmental monitoring. 6 Polycyclic aromatic hydrocarbons are classified into two main groups, low and high molecular weights, based on their physical and biological properties and number of fused aromatic rings contained in their structure. Light or low molecular weight (LMW) PAHs consist of 2-3 aromatic rings, and heavy or high molecular weight (HMW) PAHs consist of 4-6 rings. 7, 8 The HMW PAHs are more persistent and recalcitrant (less readily bio-degraded by indigenous microorganisms) than LMW PAHs and can persist in an aqueous environment and bioaccumulate in aquatic organisms like fish and shrimps, and are more carcinogenic. 9 The LMW PAHs, although less carcinogenic, also pose toxic risks to many aquatic organisms. 10 The stability and distribution of PAHs in the natural environment is influenced by the chemical structure, chemical configuration and physical and chemical properties of the aromatic rings. 8, 11 The spectrum of PAHs in the water ecosystem, including water, fish, and sediment can provide some information about their emission source. Higher concentrations of LMW PAHs (e.g., acenaphthene, fluorene) are usually related to naturally occurring PAHs, either of petrogenic or pyrogenic origin, while PAHs emitted from combustion processes (pyrolytic origin) often contain elevated concentrations of HMW (e.g., phenanthrene, fluoranthene, pyrene) and fewer LMW PAHs. 11 Polycyclic aromatic hydrocarbons have received attention due to their potential negative effects on human and ecosystem health. Adverse effects of PAHs have also been observed in marine organisms, which include impairment in growth and development, growth reduction, endocrine alteration, malformations of embryo and larvae and DNA damage. [12][13][14] Aquatic foods are high in nutritive value and thus highly desirable due to their contribution of highquality protein and low fat content. This attracts consumers to these foods due to their health benefits in addition to their widespread availability and relatively low price, although exposures to toxic chemicals have been a concerning issue for years. In Nigerian markets, fish are one of the most common aquatic organisms available for consumption and reportedly provide over 60% of protein intake. 15 Food consumption has been identified as an important pathway of human exposure to many contaminants, including PAHs. Therefore, PAH contamination of widely consumed fish species among the populace may have serious health implications as some of these aquatic organisms are caught in water polluted by hydrocarbons. 16 The objectives of the present study are to determine the concentration of PAHs in sediment samples and in two commercially important fish species, Drepane africana and Pomadasys jubelini, crabs, and shrimps around the Atlas Cove jetty. Additionally, the present study aims to assess the health risk associated with the consumption of fish species and shellfish in the study area.

Methods
The study was carried out around the Atlas Cove jetty (Figure 1), which is an offloading and storage depot for imported refined oil prior to distribution to other depots. Oil spillage has been reported in the process of operations in Commodore channel. The channel is approximately 10 m deep at the entrance, 12-15 m deep inward, 0.5 -1 km wide, and 10 km long. It is tidal, and water from the Atlantic Ocean moves in during high tides and recedes during low tides. Turbulence is very high due to its proximity to the Atlantic Ocean. In addition to oil-related activities that go on around the jetty, it is well known

Sample identification
Two species of fishes were identified as Pomadasys jubelini, (common name: grunter) ( Figure 2) and Drepane africana, (local name: akaraba) ( Figure  3). The crab was identified to be the male species of Callinectes amnicola, (common name: marine blue crab) (Figure 4), the shrimp was identified as Penaeus notialis, (common name: pink shrimp) ( Figure 5). The sampled fish, shrimp, and crab were identified as either demersal, benthopelagic or pelagic species.
Olayinka et al   Research analyses were further sieved through 0.5-mm mesh sieve and stored in foil papers until extraction was performed. The fish samples were allowed to thaw, the scales were removed and washed with running water and then distilled water before dissecting and removing the flesh and other parts which were put in sample bottles. Samples included fillets containing only fleshy parts and whole fish, including bone, fleshy parts and organs. The fish samples were weighed using an analytical weighing balance (wet weight) and homogenized with anhydrous sodium sulphate in a mortar with pestle. The mixture was labeled and wrapped in aluminum foil. It was left till the next day to cake, prior to extraction.

Reference standards
Standard mix solutions of the United State Environmental Protection Agency's (USEPA) 16 priority PAHs, each at 100 μg/L in dichloromethane, were purchased from Sigma-Aldrich (St. Louis, MO, USA). The surrogate standard was a mixture containing naphthalene-d 8 (N-d 8 ), acenaphthene-d 10 (Ace-d 10 ), phenanthrene-d 10 (Phen-d 10 ), chrysene-d 12 (Ch-d 12 ) and perylene-d 12 (Per-d 12 ), which was added to the samples before extraction and used as internal standards for quantification. Stock solutions were used to prepare working standard solutions for calibration and spiking experiments.

Extraction procedure for PAHs in sediment and aquatic organisms
Polycyclic aromatic hydrocarbons in sediment samples were extracted using a Soxhlet extraction according to the method described by the Association of Official Analytical Chemists. 21 Five (5) g of each sediment sample was weighed and 5 g of anhydrous sodium sulphate was added to each sample. The samples were placed in a cellulose thimble and extracted for 16 to 24 hours using 150 ml of dichloromethane in a Soxhlet extractor. The extract was concentrated by evaporation overnight in a fume cupboard and covered with a perforated aluminum foil. Polycyclic aromatic hydrocarbons in the biota samples were determined according to the method of USEPA 3540C. 22 A total of 5 g of each species of shrimp, crab and fish samples that had been previously homogenized with anhydrous sodium sulfate were poured into 100 ml beakers and 40 ml of n-hexane and dichloromethane (1:1 vol/vol) was used as an extracting solvent. The beaker with the content was placed on a magnetic stirrer and shaken for about 25 minutes. The extract was decanted into a clean conical flask, then 20 ml of fresh solvent was added, and the process repeated. The extracts were combined and filtered through a small glass funnel containing a layer of anhydrous sodium sulphate over a plug of glass wool into a receiving conical flask. The extracts were concentrated by allowing to stand overnight in a fume cupboard and covered with perforated aluminum foil.
Sample clean-up was carried out for both sediment and biota using USEPA Method 3630C. 23 A 600 × 19 mm clean up column was prepared. The hole was blocked with glass wool, 3 g of activated silica gel (60 mesh) was added and the column was topped with sodium sulfate. The column was rinsed by eluting with 20 ml n-hexane and discarded. The concentrated extract was loaded onto the prepared column and eluted with 50 ml n-hexane. The eluates were then concentrated to 1 ml using a rotary evaporator under a gentle stream of pure nitrogen. One (1) ml of the extract was then transferred into a well labeled vial and stored at 4°C prior to gas chromatograph mass spectrometry analysis.

Instrumental and analytical conditions
Analyses of PAHs were performed for both sediment and biota samples using a gas chromatograph mass spectrometer with selected ion monitoring (Shimadzu QP 2010 gas chromatograph mass spectrometry equipped with AOC 5000 auto injector). The column used was a Varian Factor Four fused silica capillary column (30 m × 0.25 mm × 0.25 µm film thickness) for separating target analytes. Helium was used as the carrier gas at a flow rate of 1.

Quality control
The blanks were treated the same way as the samples. Sediment and biota samples were spiked. These fortified matrices were used as calibration standards, and the range of concentrations added to both sediment and biota matrices were used to produce the calibration curves of 20 -100 mgkg -1 . The surrogate internal standards were added to the spiked sediment and biota samples at 100 mgkg -1 . The response factors were then calculated using the response obtained from desorption of a standard solution containing 40 mgkg -1 of the 16 PAHs of interest and 100 mgkg -1 of each internal standard. Spiked samples were extracted and analyzed. Recovery Research yields were 75 -110% and limit of detection for individual PAHs ranged from 0.02 to 30.00 mgkg -1 in sediment and biota with a signal to noise ratio of three (3) and limit of quantization of signal to noise ratio of ten (10).

Human health risk assessment
Toxicological risks associated with PAH concentrations in the biota samples were assessed through comparison of the observed concentrations with regulatory limits and guidelines.

Potential human health risk
To assess human health risks from exposure to PAHs through consumption of possibly contaminated biota samples (dietary intake), the dietary daily intake concentrations of PAH's from consumption of contaminated shrimps, crabs and fish species were determined. The dietary daily intake of PAHs in contaminated biota samples were assessed for the adult population using Equations 1, 2 and 3. The daily intake of PAHs from the biota samples was calculated by multiplying the respective PAH concentration in each sample by the consumption rate of an average weight adult (70 kg).

Equation 5
: where, B(A)Pteq is the carcinogenic potencies of individual PAHs and C i is the PAH concentration.
The screening value (SV) was calculated as shown in Equation 6, and then compared with the estimated TEQ value to assess the health risk of PAHs associated with consumption of the biota samples. The screening value is referred to as the threshold concentration of chemicals in edible tissue(s) that is of potential risk to consumers. It was calculated using the formula of Nozar et al. 5
*Body weight of 70 kg applies to the adult population. 15

Histopathological examination
The fish samples were dissected to remove the target organs, while the shrimps and crabs were dissected to obtain the fleshy parts. The gills, fillet, liver of fish and the fleshy parts of the crab and shrimp were put in a separate well labeled bottle, fixed in 5% formalin for at least 48 hours and transferred into a sampling bottle rack. Tissue processing for the histopathological analyses was done according to standard methods. 26 The tissues were removed from the fixative, and samples were rinsed in tap water for 5 minutes, and dehydrated in ascending ethanol concentrations (70%, 80% and 90% alcohol) for a minimum of 2 minutes each. The dehydrated tissues were cleaned in a wax miscible agent (xylene) for 2 minutes and then embedded in paraffin.

Tissue sectioning and staining
The fish tissues were then cut into sections approximately 5 μm thick from the block using a rotary microtome (Yamato Kohki, serial no: 75010JO). The cut samples were dried in a hot air oven to remove moisture and each section was mounted on a glass slide. The sections were de-waxed in a wax-miscible agent and rehydrated through descending concentrations of ethanol (90%, 80% and 70% alcohol) for at least 2 minutes each. The sections were then stained with hematoxylin and eosin, after which the tissues were placed in hematoxylin solution for 3 minutes and aqueous eosin for 3 minutes, mounted on a

Table 2 -Percentage Composition of LMW and HMW of Total PAHs Detected in Sediment Samples
Research slide and covered with cover slip and labeled. 27 The tissues were examined, and their microphotographs were taken using a digital binocular compound LED microscope (model MD827S30L series).

Statistical analysis
The obtained data were subjected to descriptive statistics and analysis of variance. The significant treatment means were separated using Duncan's multiple range tests using the Statistical Package for the Social Sciences software (SPSS) version 19.0.

Results
Concentrations of PAHs in sediment samples are presented in Table 1   In the present study, 80% of PAHs had 2-3 rings, 20% had 4-rings, and no PAHs with 5-6 rings were detected in Drepane africana and Pomadasys jubelini samples (Table 4).

Polycyclic aromatic hydrocarbon concentrations in Callinectes amnicola (blue marine crab) and Penaeus notialis (pink shrimp)
Concentrations of PAHs in Callinectes amnicola and Penaeus notialis samples are presented in Table 5. A total of 9 PAHs were detected in C. amnicola, while 10 PAH congeners (naphthalene, 1-methylnaphthalene, 2-methylnaphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, anthracene, pyrene, fluoranthene) were detected in P. notialis. All of the LMW PAHs tested for were present except for fluorene, which was not detected in crab. The highest concentration was found in naphthalene and lowest concentration was found in acenaphthylene. 29 The percentage composition pattern of PAHs detected in the samples by the number of rings is shown in Table 6.

Health risk assessment
The estimated dietary intake values of total PAHs for fillet and whole fish were 1.55 and 2.33 mg/kg body weight/day, respectively. The fish consumption rate was set at 0.0685 kg/ day from the annual per capita fish consumption of 25 kg for Nigeria. 15 The values obtained in this study exceeded the values reported for fish samples from Degele community, Sapele, Nigeria which was reported to  Table 7.

Dietary intake of polycyclic aromatic hydrocarbons from Callinectes amnicola and Penaeus notialis
The estimated dietary intake values of total PAHs for crab and pink shrimp were 0.10 and 1.56 mg/kg body, respectively.

Carcinogenic potency of individual polycyclic aromatic hydrocarbons and toxic equivalent quotient
The carcinogenic potencies of individual PAHs and TEQ values are presented in

Screening value
The SV was evaluated to assess the health risks posed by PAHs to humans from consuming the sampled organisms. The screening value is defined as the threshold concentration of chemicals in edible tissue that is of potential public health concern. 16, 32 An estimated SV of 0.0599, 0.0044 and 0.0014 mg/kg was obtained for crab, shrimp and fish samples, respectively. The resulting TEQ values obtained for the sampled biota exceeded the screening values ( Figure 6).

Histopathological examination
In the present study, the major changes observed in the gills of Drepane africana and Pomadasys jubelini were hypertrophy of the primary lamellae and hyperplasia of the secondary lamellae. Shortening and fusion of the secondary lamellae were observed in Drepane africana, while hyperplasia of the epithelial cells was observed in Pomadasys jubelini. In the muscle of Drepane africana and Pomadasys jubelini, splitting and atrophy of the muscle bundles were observed, while necrosis of the muscle bundles was seen in Pomadasys jubelini only (Figures 7a-c). Splitting of the muscle myofibrils was observed in shrimp only, while splitting and atrophy of the muscle bundles were observed in the muscles of shrimp and crab (Figures  8a-b and 9). Changes observed in the liver of Drepane africana and Pomadasys jubelini included necrosis, hepatopancreas and cellular degeneration (Figure 10a-d).

Discussion
The predominance of LMW and HMW PAHs in the sediments reflects the presence of significant combustion products from pyrolytic processes and/or petrogenic sources. 33, 34 The preponderance of LMW and HMW PAHs in the sediments indicates the presence of significant combustion products from pyrolytic processes and/ or petrogenic sources. 33,34 A sediment quality guideline of 1000 ng/g dry weight total PAHs was designed to protect estuarine fish against several important health effects. 35   Research ERL values. Table 9 indicates a high probability of risk for organisms that live in sampling locations 1 and 5. Naphthalene, acenaphthene, and fluoranthene exceeded the ERL values, but were within ERM values in both sampling locations, indicating a mild toxic effect. Anthracene exceeded the ERL and ERM values at sampling locations 1 and 5, but was within ERM value at sampling location 5. Anthracene, phenanthrene, pyrene and fluoranthene were below ERL values in sampling location 4. Anthracene, fluorene, phenanthrene, acenaphthylene and pyrene in sampling location 1 and pyrene and benzo(a)pyrene in sampling location 5 exceeded ERM values, suggesting that adverse biological effects such as cancer, reproductive and physiological disorder may occur in fish and mammals. 40
The predominance of LMW PAHs as compared to HMW PAHs in the fish samples reflects the presence of significant petrogenic processes. 33, 34 The analysis showed that a total of 10 PAHs (8 of which are among the 16 PAHs prioritized by the USEPA) were present in the fish sample. The concentration of PAHs in fish was higher than the water column; this could be due to the fact that PAHs are more readily absorbed by fish than other aquatic organisms on exposure to contaminated materials, thus attaining elevated levels compared to those in the surrounding medium. 6 The trend for the less carcinogenic LMW PAHs and the more carcinogenic HMW PAHs in Pomadasys jubeli was similar to that observed in Drepane africana presented above. The concentration of total PAHs was lower in the whole fish and fillet of both fish species compared to that of crab and shrimp in the present study. This may be because fish have been reported to have physiological mechanism(s) of rapid PAH biotransformation or depuration and could be influenced by various factors, such as chemical exposure route and time, lipid content of tissues, environmental factors, exposure to multiple contaminants, and differences in species, age, sex, and health conditions of the test animals. 28 The biotransformation of hydrophobiccontaining substances in fish is a major determinant of its toxicity, distribution and excretability. 6   include bioconcentration from water across their gills, skin and ingestion of PAH-contaminated particulate matter along with food, as PAHs readily adsorb onto particulate organic matter especially soil sediments. 15 The concentrations of contaminants such as PAHs in fish reflect the state of contamination of the environment. 43 The observed concentrations of total PAHs in fish in this study indicate high levels of PAHs contamination around the Atlas Cove jetty.

Polycyclic aromatic hydrocarbon concentrations in Callinectes amnicola (blue marine crab)
Crabs have been reported to have high lipid contents and this increases the chance of absorbing more hydrocarbon molecules, especially those that are not easily degraded or eliminated. The higher concentration of PAHs observed in the present study may be due to the proximity of the sampling points to the Atlas Cove jetty or the movement of ships along the waterways which may serve as a source of pollution. However, PAH concentrations were lower than the values (101.10 -151.49 µg/g) reported for crabs (Callinectes sapidus) obtained from the coastal area of Ondo State, Nigeria. 29 The higher levels of PAHs in shrimps are presumably due to food chain bioaccumulation and can be harmful to human health. The concentration of PAHs in crab and shrimp were significant and may have wide environmental implications, affecting bioconcentration in their tissues due to their inability to metabolize PAHs efficiently. The relatively higher concentrations of total PAHs in tissues of shellfish than fish showed the bioaccumulative potency of PAHs by the studied organisms. It may also be due to the fact that shrimps and crabs live directly on and forage in the sediments, whereas fish live up in the water column. Several aquatic organisms such as bivalves, crabs, and shrimps have been reported to bioaccumulate and bioconcentrate organic pollutants in their target organs at levels higher than background concentrations. 44,45 Therefore, they are excellent bioaccumulators of organic and inorganic pollutants. Higher concentrations of total PAHs in banana shrimp and blue crab were compared to Drepane punctata and Pomadasys kaakan, which had lower concentrations of PAHs. 5

Health risk assessment
The consumption of Drepane africana at the rate of 68 g/day may induce adverse health effects over time in consumers.

Dietary intake of polycyclic aromatic hydrocarbons from Pomadasys jubelini
The estimated dietary intake values Olayinka et al

Histopathological examination
Histopathological biomarkers are sensitive indicators of subcellular stress in organisms exposed to a range of pollutants over short and long periods of time. 50 Changes caused by toxic substances can be observed in the gills, such as an increase in pollutant blood diffusion distance as a means for protection. 50 Fusion of secondary lamellae, which is a result of hyperplasia, brings about a reduction in free gas exchange, thus affecting the general health of the fish. Hypertrophy of the primary lamellae is the enlarging or increase in size of the organ in response to a stressor in the environment. This observation is similar to a report of a high incidence of hyperplasia in Clarias gariepinus and Oreochromis niloticus reported from the Sanyati basin in Lake Kariba, Zimbabwe, as well as hyperplasia in the gills of two species of sturgeons. 50, 51 This result is an indication that the fish have been exposed to stressors. Gills are sensitive organs which are easily damaged by numerous pollutants, even at low concentrations. Gills have been reported to perform various vital functions (respiration, osmoregulation, acid-base balance).
Gills have a large surface area in contact with the external environment and are particularly sensitive to chemical and physical changes of the aquatic environment, thereby being a target organ in fish for pollutants carried by water. 51,52 Changes in the structures of these organs as well as in the vital functions performed by the gills were observed due to toxic substances present in the aquatic environment. 53 The severity of damage depends on the concentration of toxicants and the period of exposure. With prolonged exposure, these lesions could lead to fish mortality. The observed separation of muscle bundles may be due to the initial stimulus of hexachlorocyclohexane, which can induce hyperactivity and excitability in animals, leading to a release of lactic acid and subsequent muscular fatigue. The atrophy observed in the muscle bundles may be due to the exposure to various contaminants. 54 A study detected changes in muscle tissue of grass carp (Ctenopharyngodon idella) as swelling and necrosis of muscle bundles due to the effect of rice herbicides. 55 Another  Research study documented physiological disturbances and morphological damage in the muscle tissue of freshwater fish Hoplias malabaricus collected from Ponta Lake in southern Brazil due to bioaccumulation of chlorinated pesticides and PCBs. 56 Degeneration of muscle bundles with aggregation of inflammatory cells between them and focal areas of necrosis were observed by Gingerich. 57 The findings of the present study agreed with these previous reports.
The liver is the largest organ in the body and performs several important physiological functions. 58 Although every tissue has some ability to metabolize chemicals, the liver is the major organ of metabolism or transformation of toxins, making it a target organ that is highly affected by toxins in the system. Necrosis is the death of cells in a tissue or organ caused by disease or injury or as a result of exposure to harmful or toxic contaminants. The necrotic cells are shrunk, and their intercellular attachments are broken. 58 Vascular dilation may be responsible for the cellular degeneration and necrosis in the liver. When the liver is damaged, excessive blood flows into the liver, blocking the sinusoids. Oxygen deficiency as a result of gill degeneration is the most common cause of cellular degeneration in the liver (Figures 9a-d). 59 The results of this study agreed with previous reports on the effects of different pollutants on fish liver. 54,60

Conclusions
In the present study, low and high molecular weights PAHs were present in the sediment samples. The concentration of total PAHs in the sediment samples exceeded safe limits, suggesting that the aquatic organisms around Atlas Cove may pose serious human health and environmental risks. The high ratio of LMW PAHs as compared to HMW PAHs suggests that PAH contamination around Atlas Cove may be of natural origin. The concentration of total PAHs in biota samples indicated that PAH contamination from Atlas Cove was relatively high (with dominance of the low molecular weight PAHs). The high concentration of total PAHs present in the organisms indicated that the compounds have bioaccumulated in their tissues and organs over a period of time. The calculated TEQ values were higher than the screening values, indicating potential health effects. Histopathological examination revealed that both fish and shellfish were exposed to high concentrations of PAHs which brought about changes in morphologic structure of these organs, necrosis of the muscle bundles and cellular degeneration.