Levels of PCDD/PCDF and congeners profile
Tables
1,
2,
3 show the concentrations of PCDD/PCDF congeners in the fish and shellfish samples. The concentrations of PCDD/PCDF congeners were presented as levels of WHO-TEQ (pg/g) that contributed to the PCDD/PCDF toxicity. The concentrations of PCDD/PCDF in the samples between T1 and T2 were almost similar, except for Japanese threadfin bream (T1 = 0.18 pg/g; T2 = 0.73 pg/g) and grey eel-catfish (T1 = 0.90 pg/g; T2 = 1.57 pg/g). The exception may indicate the sporadic occurrences of these contaminants that may be due to unpredictable pollutants or spoilage events along the Straits of Malacca.
Table 1
Congeners of PCDD/PCDF in fish and shellfish samples from trip 1 (T1) and trip 2 (T2) of northern region
2,3,7,8-TCDF* | ND* | 0.01 | ND | ND | ND | ND | 0.01 | ND | ND | ND | ND | ND | ND | ND | 0.01 | 0.61 | ND | ND |
2,3,7,8-TCDD* | 0.02 | 0.02 | 0.02 | 0.02 | 0.01 | 0.02 | 0.02 | 0.02 | 0.02 | 0.02 | 0.01 | 0.02 | 0.01 | 0.02 | 0.04 | 0.02 | 0.01 | 0.02 |
1,2,3,7,8-PeCDF* | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND |
2,3,4,7,8-PeCDF | 0.02 | 0.02 | 0.02 | 0.02 | 0.01 | 0.02 | 0.01 | 0.02 | 0.01 | 0.02 | 0.01 | 0.02 | ND | 0.02 | 0.01 | 0.02 | ND | 0.02 |
1,2,3,7,8-PeCDD* | 0.07 | 0.10 | 0.05 | 0.06 | 0.02 | 0.09 | 0.08 | 0.06 | 0.11 | 0.05 | 0.08 | 0.05 | 0.10 | 0.05 | 0.11 | 0.06 | 0.12 | 0.05 |
1,2,3,4,7,8-HxCDF* | ND | ND | 0.01 | 0.01 | ND | 0.01 | ND | 0.01 | ND | 0.01 | ND | 0.01 | ND | 0.01 | ND | 0.01 | ND | 0.01 |
1,2,3,6,7,8-HxCDF | ND | ND | 0.01 | 0.01 | ND | 0.01 | ND | 0.01 | ND | 0.01 | ND | 0.01 | ND | 0.01 | ND | 0.01 | ND | 0.01 |
2,3,4,6,7,8-HxCDF* | ND | ND | 0.01 | 0.01 | ND | 0.01 | ND | 0.01 | ND | 0.01 | ND | 0.01 | ND | 0.01 | ND | 0.01 | ND | 0.01 |
1,2,3,7,8,9-HxCDF | ND | ND | 0.01 | 0.01 | ND | 0.01 | ND | 0.01 | ND | 0.01 | ND | 0.01 | ND | 0.01 | ND | 0.01 | ND | 0.01 |
1,2,3,4,7,8-HxCDD* | 0.01 | ND | 0.01 | 0.01 | ND | 0.01 | ND | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | ND | 0.01 | ND | 0.01 | 0.01 | 0.01 |
1,2,3,6,7,8-HxCDD | 0.01 | ND | 0.01 | 0.01 | ND | 0.01 | ND | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | ND | 0.01 | ND | 0.01 | ND | 0.01 |
1,2,3,7,8,9-HxCDD | ND | 0.01 | 0.01 | 0.01 | ND | 0.01 | ND | 0.01 | ND | 0.01 | ND | 0.01 | ND | 0.01 | ND | 0.01 | ND | 0.01 |
1,2,3,4,6,7,8-HpCDF* | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND |
1,2,3,4,7,8,9-HpCDF | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND |
1,2,3,4,6,7,8-HpCDD* | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | 0.01 | ND | ND | ND | ND |
OCDF* | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND |
OCDD* | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND |
Total | 0.13 | 0.16 | 0.16 | 0.17 | 0.04 | 0.20 | 0.12 | 0.17 | 0.16 | 0.16 | 0.12 | 0.16 | 0.11 | 0.17 | 0.17 | 0.78 | 0.14 | 0.16 |
Table 2
Congeners of PCDD/PCDF in fish and shellfish samples from trip 1 (T1) and trip 2 (T2) of middle region
2,3,7,8-TCDF | 0.01 | 0.02 | ND | 0.02 | ND | ND | ND | 0.02 | ND | ND | ND | ND | ND | 0.01 | ND | ND | 0.01 | ND |
2,3,7,8-TCDD | 0.05 | 0.07 | 0.03 | 0.05 | 0.02 | 0.02 | 0.02 | 0.05 | 0.02 | 0.02 | 0.02 | 0.02 | 0.02 | 0.06 | 0.02 | 0.03 | 0.07 | 0.04 |
1,2,3,7,8-PeCDF | ND* | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND |
2,3,4,7,8-PeCDF | 0.03 | 0.05 | 0.04 | 0.03 | 0.02 | 0.02 | 0.02 | 0.03 | 0.02 | 0.02 | 0.02 | 0.02 | 0.02 | 0.02 | 0.02 | 0.02 | 0.02 | 0.02 |
1,2,3,7,8-PeCDD | 0.22 | 0.20 | 0.13 | 0.09 | 0.06 | 0.12 | 0.07 | 0.09 | 0.05 | 0.05 | 0.09 | 0.13 | 0.05 | 0.12 | 0.05 | 0.05 | 0.09 | 0.10 |
1,2,3,4,7,8-HxCDF | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 |
1,2,3,6,7,8-HxCDF | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 |
2,3,4,6,7,8-HxCDF | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 |
1,2,3,7,8,9-HxCDF | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 |
1,2,3,4,7,8-HxCDD | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 |
1,2,3,6,7,8-HxCDD | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 |
1,2,3,7,8,9-HxCDD | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 |
1,2,3,4,6,7,8-HpCDF | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND |
1,2,3,4,7,8,9-HpCDF | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND |
1,2,3,4,6,7,8-HpCDD | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | 0.01 | ND | ND | 0.01 | ND |
OCDF | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND |
OCDD | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND |
Total | 0.38 | 0.41 | 0.27 | 0.26 | 0.17 | 0.23 | 0.18 | 0.26 | 0.16 | 0.16 | 0.20 | 0.24 | 0.16 | 0.29 | 0.16 | 0.17 | 0.27 | 0.23 |
Table 3
Congeners of PCDD/PCDF in fish and shellfish samples from trip 1 (T1) and trip 2 (T2) of southern region
2,3,7,8-TCDF | 0.01 | 0.01 | 0.01 | ND | 0.02 | ND | ND | 0.01 | ND | ND | ND | ND |
2,3,7,8-TCDD | 0.04 | 0.02 | 0.04 | 0.02 | 0.04 | 0.02 | 0.06 | 0.11 | 0.02 | 0.02 | 0.04 | 0.04 |
1,2,3,7,8-PeCDF | ND* | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND |
2,3,4,7,8-PeCDF | 0.02 | 0.02 | 0.04 | 0.02 | 0.05 | 0.02 | 0.03 | 0.07 | 0.02 | 0.02 | 0.02 | 0.02 |
1,2,3,7,8-PeCDD | 0.07 | 0.05 | 0.27 | 0.10 | 0.22 | 0.13 | 0.54 | 1.04 | 0.05 | 0.07 | 0.15 | 0.19 |
1,2,3,4,7,8-HxCDF | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 |
1,2,3,6,7,8-HxCDF | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 |
2,3,4,6,7,8-HxCDF | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 |
1,2,3,7,8,9-HxCDF | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 |
1,2,3,4,7,8-HxCDD | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.05 | 0.06 | 0.01 | 0.01 | 0.01 | 0.01 |
1,2,3,6,7,8-HxCDD | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.09 | 0.11 | 0.01 | 0.01 | 0.01 | 0.01 |
1,2,3,7,8,9-HxCDD | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.08 | 0.10 | 0.01 | 0.01 | 0.01 | 0.01 |
1,2,3,4,6,7,8-HpCDF | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND |
1,2,3,4,7,8,9-HpCDF | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND |
1,2,3,4,6,7,8-HpCDD | ND | ND | ND | ND | ND | ND | 0.02 | 0.03 | ND | ND | ND | ND |
OCDF | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND |
OCDD | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND |
Total | 0.21 | 0.17 | 0.43 | 0.21 | 0.40 | 0.24 | 0.91 | 1.57 | 0.16 | 0.18 | 0.28 | 0.32 |
Among the 17 congeners of PCDD/PCDF determined, 1,2,3,7,8-PeCDD was the most abundant congener found in all samples, which ranged between 0.02 and 1.04 pg WHO-TEQ/g FW compared with the other congeners. The results were in agreement with the data reported previously [
22], where 1,2,3,7,8-PeCDD contributed to 21-78 % of the WHO-TEQ. Similar findings were also reported previously, where the 1,2,3,7,8-PeCDD congener contributed to about 31 % of the WHO-TEQ [
23]. According to WHO, 1,2,3,7,8-PeCDD has TEF value of 1.0 [
18]. Additionally, 2,3,7,8-TCDD has TEF value of 1.0. It was classified as the Group 1 carcinogen (human carcinogen) by the WHO’s International Agency for Research on Cancer in 1997.
The congeners, 2,3,7,8-TCDD detected in all studied samples ranged from 0.01 to 0.11 pg WHO TEQ/g FW. The mean concentration of 2,3,7,8-TCDD congener (0.02 pg WHO-TEQ/g FW) in the Malaysian seafood samples determined previously was within the range of the concentration found in this study. In addition, the congeners including 1,2,3,4,6,7,8-HpCDF, 1,2,3,4,7,8,9-HpCDF, OCDF and OCDD were not detected in any of the samples. One of the reasons is these congeners are poorly absorbed by the digestive tract of fish and shellfish, where the degree of chlorination in these congeners are higher compared with that of the other congeners [
23,
24].
The types of fish that contained the highest WHO-TEQ levels were Japanese threadfin bream, large-scale tongue sole, fourfinger threadfin, Malabar red snapper, cockles, sixbar grouper and grey eel-catfish. The results showed that the highest concentrations of 2,3,7,8-TCDD, 1,2,3,7,8-PeCDD and 1,2,3,4,7,8-HxCDD were detected in grey eel-catfish samples obtained from the southern region (Table
3). Among all samples, Malabar red snapper had the highest concentration of 2,3,4,7,8-PeCDF congener (0.05 pg WHO_TEQ/g FW) from the middle region during T1’s sample collection. Based on the results obtained, the congener profiles are species-dependent. The results could have also been influenced by biological (metabolism, age and trophic level) and environmental factors (habitat, geography and seasonal variation) [
23,
25].
Congener 2,3,4,7,8-PeCDF has shown to be responsible for about 70 % of the dioxin toxicity, and it has been identified as an important causative agent in Yusho disease [
26]. The 2,3,4,7,8-PeCDF is also reported to be the second most potent and toxic congener after 2,3,7,8-TCDD [
20]. Similar pattern of the congener profile of the seafood sample was reported previously [
27], in which the largest contribution to the PCDD/PCDF toxicity was from 2,3,4,7,8-PeCDF, 2,3,7,8-TCDF, 1,2,3,7,8-PeCDD and 2,3,7,8-TCDD.
In this study, four main congeners were detected in all seafood samples. The levels of all congeners in the seafood samples were below 1 pg WHO-TEQ/g FW with some exception. The presence of specific PCDD/PCDF congeners in certain seafood samples could be related to industrial activities nearby the sea where the fish and shellfish samples were collected. Since the fish and shellfish samples collected along the Strait of Malacca have indicated some contamination with PCDD/PCDF congeners, the relevant authority in Malaysia recommended to monitor disposal of waste from factories nearby the Straits.
The concentrations of PCDD/PCDF (WHO-TEQ) in the fish and shellfish samples obtained from different regions along the Straits are presented in Table
4. The results showed that grey eel-catfish (southern region), Japanese threadfin bream (northern region) and Malabar red snapper (middle region) contained the highest PCDD/PCDF concentrations, with concentrations of 1.24, 0.46 and 0.36 pg WHO-TEQ/g FW, respectively. On the other hand, fourfinger threadfin bream from the northern region had the lowest PCDD/PCDF concentrations at 0.12 pg/g FW, respectively. A high WHO-TEQ was determined for grey eel-catfish because it is the most affected species that exhibits the highest total PCDD/PCDF at 1.24 ± 0.47 pg WHO-TEQ/g FW compared with other samples. Among the fish and shellfish samples of different regions, no significant differences were found for the WHO-TEQ levels of all types of the samples, which could be due to the fact that sea creatures freely move along the Straits of Malacca.
Table 4
Total PCDD/PCDF in fish and shellfish along the Straits of Malacca by regions
Hardtail scad | 0.17 ± 0.01 | 0.27 ± 0.01 | 0.32 ± 0.17 | 1.9 | 0.360 |
Spanish mackerel | - | - | 0.32 ± 0.15 | 4.4 | - |
Grey eel-catfish | - | - | 1.24 ± 0.47 | 5.7 | - |
Dorab wolf-herring | - | - | 0.19 ± 0.04 | 3.7 | - |
Fourfinger threadfin | 0.12 ± 0.08 | 0.2 ± 0.04 | - | 2.5 | 0.473 |
Indian mackerel | 0.15 ± 0.01 | 0.22 ± 0.07 | - | 3.5 | 0.316 |
Japanese threadfin bream | 0.48 ± 0.41 | - | - | 2.3 | - |
Long-tailed butterfly ray | 0.14 ± 0.02 | 0.16 ± 0.01 | - | 1.1 | 0.333 |
Sixbar grouper | 0.15 ± 0.01 | 0.23 ± 0.09 | - | 2.9 | 0.429 |
Silver pomfret | 0.15 ± 0.02 | - | - | 3.7 | - |
Large-scale tongue sole | 0.16 ± 0.03 | - | - | 0.8 | - |
Malabar red snapper | - | 0.40± 0.02 | - | 5.5 | - |
Cockles | - | 0.25 ± 0.02 | - | 3.0 | - |
Prawn | - | 0.22 ± 0.03 | 0.30 ± 0.04 | 1.3 | 0.117 |
Cuttlefish | 0.14 ± 0.01 | 0.17 ± 0.01 | 0.17 ± 0.02 | 2.6 | 0.604 |
Our previous study [
28] demonstrated that the levels of total dioxin and furan in these species of fish and shellfish from the Straits of Malacca were high. The results also showed that grey eel-catfish obtained from the southern region of the Straits of Malacca during trip 2 had the highest level of total PCDD/PCDF (1.57 pg WHO-TEQ/g FW) compared with other seafood samples. In this study, the WHO-TEQ level (1.24 pg/g FW) for grey eel-catfish was similar to the result reported previously. One possible explanation for the high WHO-TEQ level could be that grey eel-catfish ingested these toxic substances during food intake from the muddy ocean floor. On the other hand, the total PCDDs/PCDFs (pg WHO-TEQ/g FW) for fish fillet samples of Indian mackerel (0.10), silver pomfret (0.13), grey eel-catfish (1.23), hardtail scad (0.12) and Spanish mackerel (0.18) as reported by Azrina
et al. [
29] are lower than the WHO-TEQ levels determined in this study (Table
4). Conversely, we found the total PCDD/PCDF in the fish and shellfish samples ranged between 4.6 and 21.8 pg WHO-TEQ/g fat. Therefore, it is important to monitor the levels of PCDD/PCDF in the seafood samples obtained from the Straits of Malacca on a regular basis.
A recent study in Malaysia reported that the mean levels of PCDD/PCDF in eight types of seafood (tilapia, grouper, pomfret, barramundi, horse mackerel, snapper, prawn and cuttlefish) ranged from 0.16 to 0.17 pg WHO-TEQ/g FW [
23]. The results were much lower than the concentrations of PCDD/PCDF of the same species determined in this study. It could be due to the homogenous edible portions of the sample analysed as a group of seafood that were not determined according to individual species. As reported in another study, the total PCDD/PCDF in fish and shellfish samples from Catalan market, Spain, ranged from 0.11 to 0.66 pg WHO-TEQ/g FW [
30]. The results obtained from this study showed that the seafood samples obtained from the West Coast of Peninsular Malaysia along the Straits contained higher concentrations of PCDD/PCDF than the samples from the coastal areas of Japan. However, Moon and Ok [
31] reported that the concentrations of PCDD/PCDF in 40 types of seafood samples from Korean coastal area ranged from 0.02 to 4.39 pg WHO-TEQ/g FW. The TEQ values recorded by Moon and Ok [
31] were higher than the TEQ values found in our study. Based on the wet weight of the samples, all these findings revealed the total PCDD/PCDF detected.
On the other hand, the concentrations of PCDD/PCDF in aquatic food obtained from the local market in China ranged from 0.9 to 15317 pg WHO-TEQ/g fat [
32]. Based on a previous study, meat and poultry from Belgium have TEQ levels (PCDDs/PCDFs) ranging from trace to 7.82 pg WHO-TEQ/g fat [
33]. The results showed that horse meat has the highest total PCDD/PCDF (7.82 pg WHO-TEQ/g fat), followed by eggs (2.76 pg/g), beef and mutton (1.56 and 1.55 pg/g). Also, pork and chicken meat contained the lowest WHO-TEQ levels, 0.17 and 0.35 pg/g fat, respectively. This finding demonstrates that pork and chicken meat contain lower total PCDD/PCDF than the fish and shellfish samples.
The safe level of PCDD/PCDF in food is about 1 pg WHO-TEQ/g fat [
17]. Therefore, seafood samples from the Straits of Malacca are not safe for consumption as the total PCDD/PCDF was higher than 1 pg WHO-TEQ/g fat. In addition to food products, a high total PCDD/PCDF/PCB (13 pg WHO-TEQ/g fat) was also found in the breast milk of mothers who lived in the northern region of Peninsular Malaysia nearby the Strait of Malacca [
34]. The TEQs in the breast milk of mothers ranged from 3.0 to 24.0 pg WHO-TEQ/g fat. One possible reason for the high TEQ of mother breast milk is these mothers have consumed contaminated meat and seafood.
The rapid growth of agricultural and industrial sectors, as well as urbanisation on the west coast of Peninsular Malaysia, are among the contributors of these POP [
35]. The northern, middle and southern regions of the west coast have different stages of development and industrialisation, which might have contributed to the release of PCDD/PCDF to the environment [
36]. The smoke emitted from the human activities contains PCDD or PCDF, which increase the levels of PCDD/PCDF in the seawater.
Dietary intake and PCDD/PCDF exposure
The percentages of fish and shellfish consumption among the respondents are presented in Table
6. The seafood consumption data were collected based on daily, weekly and monthly basis using a food frequency questionnaire. The information was limited to only the frequency of consumption of specific seafood caught along the Straits of Malacca where the sample was obtained. As shown in Table
6, 15 types of fish and shellfish were considered for the seafood intake section in the questionnaire. The percentages of fish and shellfish intake were calculated based on a daily basis. The results showed that prawn (11.8 %) was the most frequently consumed seafood among the respondents, followed by fourfinger threadfin (6.5 %) and Indian mackerel (6.5 %). Indian mackerel and prawn were also found to be highly consumed by the respondents on a weekly basis, accounting for about 59.1 % and 52.7 % of intake, respectively. Meanwhile, on a monthly basis, long-tail butterfly ray (44.1 %), cuttlefish (44.1 %) and hardtail scad (40.9 %) were the major seafood consumed.
Table 6
The percentage fish and shellfish consumed by respondents
Hardtail scad | - | 26.9 | 40.9 |
Spanish mackerel | 1.1 | 18.3 | 36.6 |
Grey eel-catfish | - | 30.1 | 27.9 |
Dorab wolf-herring | 2.2 | 11.8 | 13.9 |
Fourfinger threadfin | 6.5 | 36.6 | 25.8 |
Indian mackerel | 6.5 | 59.1 | 18.3 |
Japanese threadfin bream | 1.1 | 6.5 | 13.9 |
Long-tailed butterfly ray | - | 37.6 | 44.1 |
Sixbar grouper | 2.2 | 10.8 | 16.1 |
Silver pomfret | - | 30.1 | 35.5 |
Large-scale tongue sole | 4.3 | 39.8 | 31.2 |
Malabar red snapper | 1.1 | 16.1 | 22.6 |
Cockles | 4.3 | 21.5 | 38.7 |
Prawn | 11.8 | 52.7 | 29.0 |
Cuttlefish | 4.3 | 21.5 | 44.1 |
Average intakes of a specific type of fish or shellfish, as well as total fish intake by the respondents, are presented in Table
7. The amount of large-scale tongue sole fillet consumed by the respondents was the highest among all seafood samples, with a value of 44.06 ± 97.10 g/person/day. The amounts of fish and shellfish consumed by the respondents ranged from 2.02 ± 0.87 to 44.06 ± 10.07 g/person/day. The amounts of seafood consumption reported in this study are much lower than the amounts reported in the Food Consumption Statistics of Malaysia 2003 [
38], of which the estimated mean intake of seafood for Malaysian population is 60.67 g/day and 75.59 g/day for rural areas.
Table 7
Average seafood consumption (ASC) of fish/shellfish and PCDD/PCDF exposure among fishermen and family members
Hardtail scad | 19.13 ± 3.89 | 0.12 ± 0.03 |
Spanish mackerel | 13.02 ± 2.98 | 0.07 ± 0.02 |
Grey eel-catfish | 6.71 ± 1.12 | 0.16 ± 0.03 |
Dorab wolf-herring | 10.14 ± 3.30 | 0.03 ± 0.01 |
Fourfinger threadfin | 17.31 ± 4.72 | 0.05 ± 0.01 |
Indian mackerel | 20.87 ± 3.15 | 0.07 ± 0.01 |
Japanese threadfin bream | 2.02 ± 0.87 | 0.02 ± 0.01 |
Long-tailed butterfly ray | 22.64 ± 3.09 | 0.06 ± 0.01 |
Sixbar grouper | 4.46 ± 1.46 | 0.02 ± 0.01 |
Silver pomfret | 8.95 ± 1.46 | 0.02 ± 0.00 |
Large-scale tongue sole | 44.06 ± 10.07 | 0.13 ± 0.30 |
Malabar red snapper | 7.60 ± 2.05 | 0.04 ± 0.01 |
Cockles | 2.64 ± 0.58 | 0.01 ± 0.00 |
Prawn | 12.14 ± 2.09 | 0.05 ± 0.01 |
Cuttlefish | 11.78 ± 3.80 | 0.03 ± 0.01 |
Previously, a high intake of fish and seafood products among Malaysian has been reported at 103.7 g/day [
23]. The study has also included other fishery products. However, it focuses on the consumption of 15 types of fish and shellfish among the respondents. The intake of seafood by respondents depended on the availability of these fish and shellfish; therefore, not all types of the seafood were considered. The estimated value of marine fish sources for the general population stated in the Food Consumption Statistics of Malaysia, 2003 [
38] does not indicate the consumption of particular types of fish or shellfish. Therefore, the result obtained can be used as a guideline for consumption of selected fish and shellfish among the fishing community in the middle region of the east coast of Peninsular Malaysia.
Table
7 shows the average PCDD/PCDF exposure (pg WHO-TEQ/kg BW/day) of the respondents. The PCDD/PCDF concentration of each sample was used to calculate the average PCDD/PCDF exposure (pg WHO-TEQ/kg BW/day). The highest average exposure to total PCDD/PCDF (pg WHO-TEQ/kg BW/day) among the respondents was attributed to grey eel-catfish (0.16), followed by hardtail scad (0.12) and large-scale tongue sole (0.13). Total PCDD/PCDF exposures from consumption of fish and shellfish among the respondents ranged from 0.01 to 0.16 pg WHO-TEQ/kg BW/day. In Malaysia, seafood and seafood products have contributed to PCDD/PCDF exposure at 0.41 pg WHO-TEQ/kg BW/day [
23], which is higher than the exposure among the respondents in this study. The high level of PCDD/PCDF exposure is mainly due to the consumption of fish, shellfish and also other seafood products such as canned sardine, canned crab meat, fish ball, tempura seafood, crab stick and others that are contaminated with PCDD/PCDF. In this study, the dietary exposure to PCDD/PCDF from seafood intake among the respondents was low. It is because the ASC only covered daily intake of selected fish and shellfish species among the fishermen. The PCDD/PCDF exposure among the respondents was much lower than the exposure reported by studies from Egypt (4.06-6.38 pg TEQ/kg BW/day) [
39], China (1.36 pg TEQ/kg BW/day) [
40] and Spain (1.17 pg TEQ/kg BW/day) [
41].
The results obtained from this study could represent the safety level of PCDD/PCDF in the 15 types of fish and shellfish from the Straits of Malacca. Previous research revealed that the levels of PCDD/PCDF in the serum lipid profile of fishermen were within the range of 70-200 pg WHO-TEQ/g lipid, with high consumption of Baltic fish and shellfish [
42]. The study also reported that the fishermen who consumed low to moderate amounts of Baltic seafood have 30-140 pg WHO-TEQ/g lipid detected in the serum. Therefore, increased consumption of seafood has contributed to a high exposure of PCDD/PCDF.
Among the 93 respondents, 23 of them detected having skin disease by a dermatologist. The types of skin disease detected are reported in Table
8. Besides the exposure to PCDD/PCDF, some of the skin diseases could be caused by other factors, such as sun exposure [
43] and microbial infection [
44]. The occurrence of skin diseases was high among fishermen because they worked in the environmental conditions that promote exposure to contaminants [
45]. Except for hyperpigmentation, the other types of skin disease were not related to PCDD/PCDF poisoning. There was also no chloracne case detected in this study. Skin diseases occur due to high and mostly accidental intakes of PCDD/PCDF. Therefore, skin disorders could not be expected among the respondents.
Table 8
Type of skin disease among fishermen and family members
Occurrence | | |
No | 70 | 75.0 |
Yes | 23 | 25.0 |
Types | | |
Eczema | 7 | 7.6 |
Tinea versicolor (Tinea) | 4 | 4.3 |
Psoriasis | 3 | 3.2 |
Hyperpigmentation | 2 | 2.2 |
Tinea cruris/ corporis (Ringworm) | 2 | 2.2 |
Acne vulgaris | 1 | 1.1 |
Seborrheic capitis (Dandruff) | 1 | 1.1 |
Tinea corporis (Ringworm) | 1 | 1.1 |
Toe-web intertrigo | 1 | 1.1 |
Sebaceous cyst | 1 | 1.1 |
Seborrhoeic wart | 0 | 0 |
Favre-Racouchot syndrome | 0 | 0 |
Hyperpigmentation | | |
Skin (trunk) | 1 | 1.1 |
Mucosa (cheek and gum) | 1 | 1.1 |
Chloracne and hyperpigmentation are the two most common types of skin disease related to PCDD/PCDF exposure to humans. The study merely focused on skin diseases related to PCDD/PCDF exposure among the respondents. As shown in Table
8, two respondents (2.2 %) were found to have hyperpigmentation. Only one of them had skin hyperpigmentation, whereas the other had hyperpigmentation on the mucosa (gum and buccal mucosa). It is highly unlikely that this localised hyperpigmentation is caused by dioxins/furans exposure or toxicity. All cases of dioxin/furan-related hyperpigmentation reported a severe, generalised darkening of skin and abnormal pigmentation, with almost the entire body surface area involved [
25]. Ideally blood levels of dioxins/furans or congeners in these two fishermen should be measured, which would confirm the relationship of the skin changes and dioxins/furans toxicity. However, the hyperpigmentation detected among the respondents could be due to extreme exposure to sunlight while fishing [
43]. Based on their fish intake assessed using FFQ, both of the respondents had low PCDD/PCDF exposure. The first and second respondents who were diagnosed with hyperpigmentation consumed 8.63 and 13.61 g of fish per day, respectively. The exposures to PCDD/PCDF for both of them were 0.04 and 0.06 pg WHO-TEQ/kg BW/day, respectively. The low level of exposure reaffirms the finding that the skin hyperpigmentation is unrelated to PCDD/PCDF. Also, the exposure was below the recommended level (1 pg TEQ/kg BW/day) [
16].
Sociodemographic characteristics and lifestyles could be the main factors for hyperpigmentation of the skin. The low exposure to PCDD/PCDF for the two respondents shows that dioxin and furan toxicity was not the cause of skin hyperpigmentation. Sunlight exposure seems to be the only cause of hyperpigmentation. On the contrary, the members of a Spanish family (father, mother and six children) developed chloracne and hyperpigmentation due to ingestion of olive oil contaminated with PCDD/PCDF [
46]. The level of PCDD/PCDF detected in the chloracneigenic oil from Spain was 1590 pg WHO-TEQ/g oil, where the levels of exposure to these contaminants among the family member ranged from 620 to 1500 pg WHO-TEQ/kg BW/day. Hyperpigmentation and acne-like eruptions have also been documented in the “Yusho” incidence in Japan. The incidence was caused by ingestion of Japanese rice oil containing PCB and PCDF at the exposure level of <400 ppm [
25].
The results obtained from this study revealed that the low PCDD/PCDF exposure among the respondents indicates the skin diseases cannot be contributed by PCDD/PCDF toxicity. Based on the previous literature, a high level of exposure is required to cause skin toxicity (chloracne and hyperpigmentation) [
47]. Based on a follow-up study reported by Guo
et al. [
48], the subjects who had emitted to hospital were estimated to have consumed about 3.8 mg of PCDFs. The amounts of PCDD/PCDF ingested by the respondents were estimated to be more than 2000 times lower than the reported case.
Exposure to PCDD/PCDF through intake of fish and shellfish is considered one of the risk factors for skin toxicity. Although blood samples were not taken from the respondents, the information obtained based on the questionnaire, as well as the skin examination by the dermatologist, could provide some hints on the possible contribution of dietary fish and shellfish to skin diseases related to PCDD/PCDF toxicity. The information is very important in the future as guidelines to the authority and public, as well as research scientists, for further investigation of PCDD/PCDF exposure among the fishing community since this group is more likely to be affected by environmental pollutants. Additionally, this study will provide baseline data to the stakeholders in Malaysian fishery industry. The data can also be used as a guideline to determine whether the levels of PCDD/PCDF in local marine fish and shellfish are below the recommended levels [
17].