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The present study aimed to confirm the use of the byssus (BYS) of the green-lipped mussel Perna viridis as a biomonitoring biopolymer for zinc (Zn) by comparing it to copper (Cu) and cadmium (Cd) pollution in coastal waters under experimental field conditions, based on the transplantation of caged mussels between polluted and unpolluted sites in the Straits of Johore (SOJ). Four important evidential points were found in the present study. First, the 34 field-collected populations with BYS/total soft tissue (TST) ratios > 1 indicated that the BYS was a more sensitive, concentrative, and accumulative biopolymer for the three metals than TST. Significant ( p < 0.05) and positive correlations between BYS and TST in terms of the levels of the three metals were observed. Second, the data obtained in the present study were well-supported by the interspecific comparison, which indicated that the BYS of P. viridis was a significantly better biomonitoring biopolymer for the identification of coastal areas exposed to Zn, Cd, and Cu pollution and played the role of an excretion route of metal wastes. Third, the higher positive correlation coefficients for the metals between the BYS sedimentary geochemical fractions than the TST sedimentary geochemical fractions indicated that the BYS was more reflective of metal bioavailability and contamination in coastal waters. Fourth, and most importantly, the field-based cage transplantation study clearly indicated the accumulation and elimination of the three metals by the BYS in both polluted and unpolluted sites in the Straits of Johore. In sum, the BYS of P. viridis was confirmed as a better biopolymer than TST for Zn, as well as Cd and Cu, bioavailability and contamination in tropical coastal waters.

This study aimed to evaluate the ecological-health risks of potentially toxic metals in the surface sediments on the Klang mangrove ecosystem and assessed the phytoremediation potential of Avicennia officinalis collected from the area. The results showed that the concentrations (mg/kg dry weight) of Cu, Ni, Pb and Zn in the surface sediments ranged between 5.30−63.8, 14.2−32.7, 30.3−62.3, and 46.4−269, respectively. The ecological risk values of the surface sediments indicated that Ni, Pb and Zn were all classified as ‘low potential ecological risk’, while the Cu ecological risk ranged between ‘low potential ecological risk’ and ‘considerable potential ecological risk’. For the health risks on the sediments, all of the values of hazard index for Cu, Ni, Pb and Zn, based on a combination of three pathways, indicated < 1.00, showing that the four metals are non-carcinogenic. Based on the bioconcentration factor values, it can be concluded that the lamina has better potential as a phytoremediator of essential Cu, Zn and Fe. In contrast, midrib plus petiole has better potential as a phytoremediator of non-essential Pb and Ni. To mitigate the threats to the Klang mangrove ecosystem, the information offered in the present study can be employed in the monitoring and provision of the ecological-health risks of potentially toxic metals in the Klang mangrove ecosystem. Hence, the present findings can be employed for developing a water-energy-food framework for managing the Klang mangrove ecosystem.

Human health risk and phytoremediation of potentially toxic metals (PTMs) in the edible vegetables have been widely discussed recently. This study aimed to determine the concentrations of four PTMs, namely Cd, Fe, Ni, and Zn) in Amaranthus viridis (leaves, stems, and roots) collected from 11 sampling sites in Peninsular Malaysia and to assess their human health risk (HHR). In general, the metal levels followed the order: roots > stems > leaves. The metal concentrations (µg/g) in the leaves of A. viridis ranged from 0.45 to 2.18 dry weight (dw) (0.05−0.26 wet weight (ww)), 74.8 to 535 dw (8.97−64.2 ww), 2.02 to 7.45 dw (0.24−0.89 ww), and 65.2 to 521 dw (7.83−62.6 ww), for Cd, Fe, Ni, and Zn, respectively. The positive relationships between the metals, the plant parts, and the geochemical factions of their habitat topsoils indicated the potential of A. viridis as a good biomonitor of Cd, Fe, and Ni pollution. With most of the values of the bioconcentration factor (BCF) > 1.0 and the transfer factor (TF) > 1.0, A. viridis was a very promising phytoextraction agent of Ni and Zn. Additionally, with most of the values of BCF > 1.0 and TF < 1.0, A. viridis was a very promising phytostabiliser of Cd and Fe. With respect to HHR, the target hazard quotients (THQ) for Cd, Fe, Pb, and Zn in the leaves of A. viridis were all below 1.00, indicating there were no non-carcinogenic risks of the four metals to consumers, including children and adults. Nevertheless, routine monitoring of PTMs in Amaranthus farms is much needed.

Human exposure to highly nickel (Ni)-polluted environments through oral ingestion pathways may cause various pathological effects. This biomonitoring study aimed to assess the human health risk of potentially toxic Ni in 19 species of marine fishes from Setiu (Terengganu) and two popular seafood molluscs (mangrove snail Cerithidea obtusa and cockle Anadara granosa ) from the coastal area of Peninsular Malaysia. The Ni levels of the three seafood types were found below the maximum permissible limit for Ni. The Ni target hazard quotient values of all seafood were lower than 1.00 for average and high-level (AHL) Malaysian consumers, indicating no Ni's non-carcinogenic risk of seafood consumption. It was also found that the calculated values of estimated weekly intake were below than established provisional tolerable weekly intake of Ni for both AHL consumers. It can be concluded that both the AHL consumption of seafood would not pose adverse effects of Ni to the consumers. This study provided a scientific basis for the food safety assessment of Ni and suggestions for risk management of potentially toxic Ni of seafood consumption in Malaysia.

Human activities due to different land uses are being studied widely in many countries. This study aimed to determine the ecological risks and human health risk assessments (HHRA) of Cd, Pb, Ni, Cu, and Zn in the topsoils of six land uses in Peninsular Malaysia. The ranges of the potentially toxic metals (PTMs) in the soils (mg/kg, dry weight) of this study were 0.24-12.43 for Cd (mean: 1.94), 4.66-2363 for Cu (mean: 228), 2576-116,344 for Fe (mean: 32,618), 2.38-75.67 for Ni (mean: 16.04), 7.22-969 for Pb (mean: 115) and 11.03-3820 for Zn (mean: 512). For the ecological risk assessments, the potential ecological risk index (PERI) for single metals indicated that the severity of pollution of the five metals decreased in the following sequence: Cd > Cu > Pb > Zn > Ni. It was found that industry, landfill, rubbish heap, and mining areas were categorized as "very high ecological risk". For HHRA, the land uses of industry, landfill and rubbish heap were found to have higher hazard quotient (HQ) values for the three pathways (with the order: ingestion > dermal contact > inhalation ingestion) of the five metals for children and adults, when compared to the mining, plantation, and residential areas. The values for both the non-carcinogenic (Cd, Cu, Ni, and Zn), and carcinogenic risks (CR) for inhalation (Cd and Ni) obtained for children and adults in this study showed no serious adverse health impacts on their health. However, of public concern, the hazard index (HI), for Pb of children at the landfill (L-3) and the rubbish heap (RH-3) sites exceeded 1.0, indicating non-carcinogenic risk (NCR) for children. Therefore, these PERI and HHRA results provided fundamental data for PTMs pollution mitigation and environmental management in areas of different land uses in Peninsular Malaysia.

The ASEAN-5 countries (Malaysia, Indonesia, Thailand, Philippines, and Vietnam) of the Association of Southeast Asian Nations as a group is an ever-increasing major economy developmental hub in Asia besides having wealthy natural resources. However, heavy metal (HM) pollution in the region is of increasing environmental and public concern. This study aimed to review and compile the concentrations of Cu, Pb, and Zn in the aquatic sediments of the ASEAN-5 countries published in the literature from 1981 to February 2021. The mean values of Cu, Pb, and Zn in aquatic sediments were elevated and localized in high human activity sites and compared to the earth's upper continental crust and reference values. Based on 176 reports from 113 publications, the ranges of concentrations (mg/kg dry weight) were 0.09-3080 for Cu, 0.37-4950 for Zn, and 0.07-2666 for Pb. The ecological risk (ER) values ranged from 0.02-1077 for Cu, 0.01-95.2 for Zn, and 0.02-784 for Pb. All reports (100%) showed the Zn ER values were categorized as being between 'low potential ecological risk' and 'considerable potential ecological risk'. Almost all Cu ER values (97.7%) also showed similar ranges of the above two risk categories except for a few reports. The highest Cu level (3080 mg/kg dry weight) was reported from a mine-tailing spill in Marinduque Island of the Philippines with 'very high ecological risk'. In addition, drainage sediments in the western part of Peninsular Malaysia were categorized as Cu 'high potential ecological risk'. Almost all reports (96%) showed Pb ER values categorized as between 'low potential ecological risk' and 'moderate potential ecological risk' except for a few reports. Six reports showed Pb ER values of 'considerable potential ecological risk', while one report from Semarang (Indonesia) showed Pb ER of 'very high ecological risk' (Pb level of 2666 mg/kg dry weight). For the ingestion and dermal contact pathways for sediments from the ASEAN-5 countries, all non-carcinogenic risk (NCR) values (HI values 1.0) for Cu, Pb, and Zn reflected no NCR. The ER and human health risk assessment of Cu, Pb, and Zn were compared in an integrative and accurate manner after we reassessed the HM data mentioned in the literature. The synthesis carried out in this review provided the basis for us to consider Cu, Pb, and Zn as being of localized elevated levels. This provided evidence for the ASEAN-5 group of countries to be considered as being a new socio-economic corridor. Beyond any reasonable doubt, an ever-increasing anthropogenic input of HMs is to be expected to a certain degree. We believe that this paper provides the most fundamental useful baseline data for the future management and sustainable development of the aquatic ecosystems in the region. Lastly, we claim that this review is currently the most up-to-date review on this topic in the literature.