**7. Tolerable intake**

The PLI value more than 1 can be categorized as polluted whereas less than 1 indicates no

Lying in the second trophic level in the aquatic ecosystem, shellfish species have long been known to accumulate both essential and nonessential metals. Many researchers have reported the potentiality of using mollusks, especially mussel and oyster species, as bio-indicators or bio-markers for monitoring the metals contamination of the aquatic system (**Figure 8**). Beside as a bio-marker for marine pollution studies, mollusks species also been used in ecotoxicology and toxicity studies. Individual bio-monitors respond differently to different sources of bioavailable chemical elements for example, in the solution, in sediments, or in foods. To gain a complete picture of total metals bioavailability in a marine habitat, it is necessary, therefore, to use a correct bio-monitor that can reflect the element bioavailability in all available sources [52]. Such comparative use of different bio-monitors should allow the identification of the

Living organisms in aquatic environment can transport pollutants and contaminants into, within, and out of the marine aquatic ecosystem. These organisms can ingest the pollutants via water and food, and inhale them as they breathe and feed [54]. Once in the body, some contaminants pass quickly while others can be retained for long periods and accumulate in body tissues, particularly fatty tissues [55]. Some of the chemical elements that show the greatest bioaccumulation are those that do not dissolve in water, but instead dissolve in fats and oils (i.e., mercury and PCBs). In some cases, the accumulation of pollutants is intensified in carnivorous animals high in the food chain, ranging from big organism such as fishes and to

**Figure 8.** Some examples of organism commonly used for environmental biomonitoring study. Photo by Ong Meng

pollution at the study area [50, 51].

**6. Aquatic organisms as biomarker**

36 Wetlands Management - Assessing Risk and Sustainable Solutions

particular source of the contaminant elements [53].

human [56].

Chuan.

Beside fishes, shellfish such as oysters and mussels are an important source of dietary protein in coastal communities. Depending on consumer, those shellfish can be "swallowed" or masticated normally, increasing the surface contact between food and digestive fluids. The consumer will consume whole soft part of the shellfish (**Figure 9**); therefore, in the pollution study which relates to human health, the metals content is examined in toto or shellfish flesh.

To safeguard public health, who consumes these organisms, maximum acceptable concentrations of toxic contaminants have been established in various countries. As a result, there is a specific legislation for shellfish, which establishes the maximum allowed concentration for metals (**Table 2**).

**Figure 9.** Oyster in toto tissue use for metals study in relation to human health. Photo by Ong Meng Chuan.


**Table 2.** Maximum permissible levels (expressed in mg/kg wet weight) of metals in shellfish from different countries or regions.

International scientific committees such as the Joint FAO/WHO Expert Committee on Food Additives (JECFA), regional scientific committees such as the European Union and national regulatory agencies generally use the safety factor approach for establishing acceptable of tolerable intakes of substances that exhibit thresholds of the toxicity of contaminants. JECFA derives tolerable intakes, expressed on either daily or weekly basis, for contaminants [66]. Lead, Cd, As, and Hg are not removed rapidly from human body and for this category of pollutants, provisional tolerable weekly intakes (PTWIs) are calculated and expressed on a weekly basis because the pollutant may accumulate within the human body over a period of time [67]. The term tolerable is used because it signifies permissibility rather than acceptability for the pollutants intake unavoidably associated with the consumption.

**Notes/thanks/other declarations**

**Author details**

Ong Meng Chuan<sup>1</sup>

Malaysia

**References**

**77**(2):93-98

2009;**407**(17):4902-4915

Landforms. 1991;**16**(5):427-445

change-in-50-years/

Nerus, Terengganu, Malaysia

that provide us the facilities to run our research project.

\*Address all correspondence to: ong@umt.edu.my

in Marine Biology. 2001;**40**:81-251

Marine Pollution Bulletin. 1973;**4**(4):59-61

\* and Kamaruzzaman Yunus<sup>2</sup>

Thanks to School of Marine and Environmental Sciences, Universiti Malaysia Terengganu

Metals Pollution in Tropical Wetlands http://dx.doi.org/10.5772/intechopen.82153 39

1 School of Marine and Environmental Sciences, Universiti Malaysia Terengganu, Kuala

[1] Kathiresan K, Bingham BL. Biology of mangroves and mangrove ecosystems. Advances

[3] Perkins EJ, Gilchrist JRS, Abbott OJ, Halcrotv W. Trace metals in Solway Firth sediments.

[4] Munafò M, Cecchi G, Baiocco F, Mancini L. River pollution from non-point sources: A new simplified method of assessment. Journal of Environmental Management. 2005;

[5] Schaffner M, Bader HP, Scheidegger R. Modeling the contribution of point sources and non-point sources to Thachin River water pollution. Science of the Total Environment.

[6] Available from: https://technofaq.org/posts/2017/07/thoughts-on-the-future-of-gis-what-will-

[7] Bloemer HL, Needham SE, Steyaert LT. Operational satellite data assessment for drought/ disaster early spring in Africal Comments on GIS requirements. In: Symposium of Remote Sensing for Resources Development and Environmental Management. 1986. pp. 561-568 [8] Carrara A, Cardinali M, Detti R, Guzzeti F, Pasqui V, Reichenbach P. GIS techniques and statistical models in evaluating landslide hazard. Earth Surface Processes and

2 Kulliyyah of Science, International Islamic University Malaysia, Kuantan, Pahang,

[2] Available from: http://www.hydro-industries.co.uk/case-studies.htm?id=10
