AccScience Publishing / AJWEP / Volume 12 / Issue 2 / DOI: 10.3233/AJW-2015-12_2_04
RESEARCH ARTICLE

Assessment of Environmental and Human Health Risk  for Contamination of Heavy Metal in Tilapia Fish  Collected from Langat Basin, Malaysia

Lubna Alam1* Mazlin Bin Mokhtar1 Md. Mahmudul Alam1 Md. Azizul Bari1 Nicholas Kathijotes2 Goh Choo Ta1 Lee Khai Ern1
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1 Institute for Environment and Development (LESTARI) Universiti Kebangsaan Malaysia (UKM), Bangi, 43600, Selangor DE, Malaysia
2 Department of Civil Engineering & Geomatics University of Technology, Cyprus
AJWEP 2015, 12(2), 21–30; https://doi.org/10.3233/AJW-2015-12_2_04
Submitted: 25 September 2014 | Accepted: 26 March 2015 | Published: 1 January 2015
© 2015 by the Author(s). This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution -Noncommercial 4.0 International License (CC-by the license) ( https://creativecommons.org/licenses/by-nc/4.0/ )
Abstract

This investigation quantified spatial variability of heavy metals and followed methods of the U.S.  Environmental Protection Agency (EPA) to estimate the hazard indices as well as cancer risks associated with  consuming fish caught in the waters of the Langat river basin area, Malaysia. The calculation of metal pollution  index (MPI) was carried out to classify the study area according to the level of contamination and the order  of stations from highest to lowest MPI values was Langat river > Cempaka lake > Engineering pond > Pond  B > Pond A > Jugra > Bandar. The level of exposure due to the consumption of each chemical in Tilapia fish  tissue was estimated in an average daily dose equation. The calculated HI ranging from 0.24 to 1.88 indicated  71% stations were in the risk level. Potential carcinogenic risks associated with the ingestion of heavy metals in  Tilapia fish were evaluated probabilistically by performing 10,000 trials for Monte Carlo simulation. Cancer risk  calculations exceeding the U.S. EPA’s acceptable risk level of 1 in 1,000,000 (or 10-6) included Ni (7.3×10-4)  and Cd (2.1×10-6). However, the average carcinogenic risk (2.4×10-4) exceeded the accepted risk level to a great  extent. The recommended daily ingestion rate of Tilapia for Malaysian people inhabiting Langat river basin  area was calculated considering 95th percentile TR value of 10-6 as an acceptable risk where it is revealed that  consumption of Tilapia should be reduced about 67% from the current level to have an acceptable risk of cancer.

Keywords
Risk
HQ
HI
TR
metal
Langat
Conflict of interest
The authors declare they have no competing interests.
References
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Ahdy, H.H.H., Abdallah, A.M.A. and Tayel, F.T. (2007). Assessment of heavy metals and non-essential content of some edible and soft tissue. Egyptian Journal of Aquatic Research, 33: 85-97.

Alam, L. and C.A.R. Mohamed (2011). Natural radionuclide of Po210 in the edible seafood affected by coal-fired power plant industry in kapar coastal area of Malaysia. Environmental Health, 10: 1-10.

Amin, B., Ismail, A., M.S.K, Arshad, A. and C.K. Yap (2005). Heavy metals (Cd, Cu, pH and Zn) concentrations in Telescopium telescopium from Dumai coastal waters, Indonesia. Pertanika Journal of Tropical Agricultural Science, 28: 33-39.

Asplund, L., Svensson, B., Nilsson, A., Eriksson, U., Jansson, B., Jensen, S. et al. (1994). Polychlorinated biphenyls, 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (p,p’-ddt) and 1,1-dichloro-2,2-bis(p-chlorophenyl)-ethylene (p,p’-dde) in human plasma related to fish consumption. Archives of Environmental Health, 49: 477-486.

Bernama (2010). Syabas tutup sementara loji semenyih berikutan pencemaran.

Bhupander, K. and D.P. Mukherjee (2011). Assessment of human health risk for arsenic, copper, nickel, mercury and zinc in fish collected from tropical wetlands in India. Advances in Life Science and Technology, 2: 13-25.

Burger, J., Gochfeld, M., Shukla, T., Jeitner, C., Burke, S., Donio, M. et al. (2007). Heavy metals in pacific cod (Gadus macrocephalus) from the Aleutians: Location, age, size, and risk. Journal of Toxicology and Environmental Health, Part A 70: 1897-1911.

Burger, J. and M. Gochfeld (2009). Perceptions of the risks and benefits of fish consumption: Individual choices to reduce risk and increase health benefits. Environmental Research, 109: 343-349.

Dewailly, E., Ryan, J.J., Laliberté, C., Bruneau, S., Weber, J.P., Gingras, S. et al. (1994). Exposure of remote maritime populations to coplanar PCBs. 102: 205-209.

Díez, S., Delgado, S., Aguilera, I., Astray, J., Pérez-Gómez, B., Torrent, M. et al. (2009). Prenatal and early childhood exposure to mercury and methylmercury in Spain, a high-fish-consumer country. Arch Environ Contam Toxicol, 56: 615-622.

DOE (2006). Malaysia environmental quality report 2006 in Impak, Kuala Lumpur.

EC (2004). Assessment of the dietary exposure to arsenic, cadmium, lead and mercury of the population of the EU member states. (Reports on Tasks for Scientific Cooperation). European Commission.

Han, B.-C., Jeng, W.-L., Hung, T.-C. and M.-S. Jeng (1994). Copper intake and health threat by consuming seafood from copper-contaminated coastal environments in Taiwan. Environmental Toxicology and Chemistry, 13: 775-780.

Han, B.-C., Jeng, W.-L., Hung, T.-C., Ling, Y.-C., Shieh, M.-J. and L.-C. Chien (2000). Estimation of metal and organochlorine pesticide exposures and potential health threat by consumption of oysters in Taiwan. Environmental Pollution, 109: 147-156.

Jang, C.S., Liu, C.W., Lin, K.H., Huang, F.M. and S.W. Wang (2006). Spatial analysis of potential carcinogenic risks associated with ingesting arsenic in aquacultural tilapia (Oreochromis mossambicus) in blackfoot disease hyperendemic areas. Environmental Science & Technology, 40: 1707-1713.

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Khaled, A. (2004). Seasonal concentrations of some heavy metals in muscle tissues of Siganus rivulatus and Sargus sargus fish from El-mex Bay and eastern harbour, Alexandria, Egypt. Egyptian Journal of Aquatic Biology and Fisheries, 8: 65-81.

Laar, C., Fianko, J.R., Akiti, T.T., Osae, S. and A.K. Brimah (2011). Determination of heavy metals in the black-chin tilapia from the Sakumo Lagoon, Ghana. Research Journal of Environmental and Earth Sciences, 3: 8-13.

Liao, C.M. and M.P. Ling (2003). Assessment of human health risks for arsenic bioaccumulation in tilapia (Oreochromis mossambicus) and large-scale mullet (Liza macrolepis) from blackfoot disease area in Taiwan. Arch Environ Contam Toxicol, 45: 264-272.

Lim, T.O., Ding, L.M., Zaki, M., Suleiman, A.B., Fatimah, S., Siti, S. et al. (2000). Distribution of body weight, height and body mass index in a national sample of Malaysian adults. Medical Journal of Malaysia, 55: 108-128.

Liu, C.W., Liang, C.P., Huang, F.M. and Y.M. Hsueh (2006). Assessing the human health risks from exposure of inorganic arsenic through oyster (Crassostrea gigas) consumption in Taiwan. Science of the Total Environment, 361: 57-66.

Liu, C.W., Liang, C.P., Lin, K.H., Jang, C.S., Wang, S.W., Huang, Y.K. et al. (2007). Bioaccumulation of arsenic compounds in aquacultural clams (Meretrix lusoria) and assessment of potential carcinogenic risks to human health by ingestion. Chemosphere, 69: 128-134.

Lushenko, M.A. (2010). A risk assessment for ingestion of toxic chemicals in fish from Imperial beach, California: San Diego State University.

Mallin, M., McIver, M., Fulton, M. and E. Wirth (2011). Elevated levels of metals and organic pollutants in fish and clams in the Cape Fear River watershed. Arch Environ Contam Toxicol, 61: 461-471.

Mansilla-Rivera, I. and C. Rodríguez-Sierra C. (2011). Metal levels in fish captured in Puerto Rico and estimation of risk from fish consumption. Arch Environ Contam Toxicol, 60: 132-144.

Mishra, S., Bhalke, S., Saradhi, I.V., Suseela, B., Tripathi, R.M., Pandit, G.G. et al. (2007). Trace metals and organometals in selected marine species and preliminary risk assessment to human beings in Thane Creek area, Mumbai. Chemosphere, 69: 972-978.

Mohamed, A.F., Yaacob, W.Z.W., Taha, M.R. and A.R. Samsudin (2009). Groundwater and soil vulnerability in the Langat Basin, Malaysia. European Journal of Scientific Research, 27: 628-635.

Mokhtar, M.B., Aris, A.Z., Munusamy, V. and S.M. Praveena (2009). Assessment level of heavy metals in penaeus monodon and oreochromis spp in selected aquaculture ponds of high densities development area. European Journal of Scientific Research, 30: 348-360.

Núria, F.H., Martí, N., Pablo, D.L.I., Diogène, Jorge and L.D. José (2009). Risk assessment of trace elements from consuming local seafood by the population living in the Ebro river basin in Catalonia, Spain. ICMSS09 – Nantes.
OEHHA (2007). Fish. Available: http://www.oehha.ca.gov/fish.html [accessed 16 August 2012].

OEHHA (2011). Adoption of the revised air toxics hot spots program technical support document for cancer potency factors.

OhioEPA (2008). Ecological risk assessment guidance document. Lazarus Government Center, 50 West Town St., Suite 700, Columbus:Division of Environmental Response and Revitalization.

Onsanit, S., Ke, C., Wang, X., Wang, K.-J. and W.-X. Wang (2010). Trace elements in two marine fish cultured in fish cages in Fujian province, China. Environmental Pollution, 158: 1334-1342.

Paquin, R.R., Farley, K., Santore, R.C., Kavvadas, C.D., Mooney, K.G., Winfield, R.P. et al. (2003). Metals in aquatic systems: A review of exposure, bioaccumulation, and toxicity models. Society of Environmental Toxicology and Chemistry (SETAC), Pensacola.

PNSB (2010). 2009 Annual Report. Kuala Lumpur.

Said, K.S., Shuhaimi, M. and A. Kutty (2012). The water quality and metal concentrations of Cempaka Lake, Selangor, Malaysia. In: Management of natural resources, sustainable development and ecological hazards (Brebbia, C.A., Zubir, S.S., eds). WIT Press.

Schmitt, C., Brumbaugh, W., Linder, G. and J.E. Hinck (2006). A screening-level assessment of lead, cadmium, and zinc in fish and crayfish from northeastern Oklahoma, USA. Environmental Geochemistry and Health, 28: 445-471.

Statistic of Agro Food (2010). Statistic of agro food. In press.

Storelli, M.M. (2008). Potential human health risks from metals (Hg, Cd and Pb) and polychlorinated biphenyls (PCBs) via seafood consumption: Estimation of target hazard quotients (THQs) and toxic equivalents (TEQs). Food and Chemical Toxicology, 46: 2782-2788.
 
 
Svensson, B.G., Nilsson, A., Jonsson, E., Schütz, A., Akesson, B. and L. Hagmar (1995). Fish consumption and exposure to persistent organochlorine compounds, mercury, selenium and methylamines among Swedish fishermen. Scandinavian Journal of Work, Environment & Health, 21: 96-105.

Taweel, A., Othman, M.S. and A.K. Ahmad (2011). Heavy metals concentration in different organs of tilapia fish (Oreochromis niloticus) from selected areas of Bangi, Selangor, Malaysia. African Journal of Biotechnology, 10: 11562-11566.

The Star (2006). Environment Part 03/28/2006.

Tu, N.P.C., Ha, N.N., Ikemoto, T., Tuyen, B.C., Tanabe, S. and I. Takeuchi (2008). Regional variations in trace element concentrations in tissues of black tiger shrimp Penaeus monodon (Decapoda: Penaeidae) from South Vietnam. Marine Pollution Bulletin, 57: 858-866.

USEPA (2011). USEPA regional screening level (RSL) summary table. Washington, DC.

USEPA (2012). Fish consumption advisories. Available: http://water.epa.gov/scitech/swguidance/fishshellfish/fishadvisories/index.cfm (accessed 16 August 2012).

USEPA (2000). Guidance for assessing chemical contaminant data for use in fish advisories: Volume 1. In: Fish Sampling and Analysis. 3rd Edition. Office of Science and Technology of Water, Washington:DC EPA 823-B-00-007.

USEPA (2012). Waste and cleanup risk assessment.

Usero, J., González-Regalado, E. and I. Gracia (1997). Trace metals in the bivalve molluscs Ruditapes decussatus and Ruditapes philippinarum from the Atlantic coast of southern Spain. Environment International, 23: 291-298.

Yusof, M.F. (2007). The water crisis in Selangor? – A million population will be affected by ammonia contaminated river Utusan.

Yusuf, M.A. and M. Nordin (2003). River water quality assessment and ecosystem health: Langat river basin, Selangor, Malaysia. In: Rapport, D.J., Lesley, W.L., Rolston, D.E., Nielson, N.O., Quelset, C.O. and Damania, A.D. (eds). Managing for healthy ecosystems. Lewis/CRC Press, Boca Raton, Florida.

Zhou, H.Y., Cheung, R.Y.H., Chan, K.M. and M.H. Wong (1998). Metal concentrations in sediments and tilapia collected from inland waters of Hong Kong. Water Research, 32: 3331-3340.
Adeniyi, A., Yusuf, K. and O. Okedeyi (2008). Assessment of the exposure of two fish species to metals pollution in the ogun river catchments, Ketu, Lagos, Nigeria. Environmental Monitoring and Assessment, 137: 451-458.

Ahdy, H.H.H., Abdallah, A.M.A. and Tayel, F.T. (2007). Assessment of heavy metals and non-essential content of some edible and soft tissue. Egyptian Journal of Aquatic Research, 33: 85-97.

Alam, L. and C.A.R. Mohamed (2011). Natural radionuclide of Po210 in the edible seafood affected by coal-fired power plant industry in kapar coastal area of Malaysia. Environmental Health, 10: 1-10.

Amin, B., Ismail, A., M.S.K, Arshad, A. and C.K. Yap (2005). Heavy metals (Cd, Cu, pH and Zn) concentrations in Telescopium telescopium from Dumai coastal waters, Indonesia. Pertanika Journal of Tropical Agricultural Science, 28: 33-39.

Asplund, L., Svensson, B., Nilsson, A., Eriksson, U., Jansson, B., Jensen, S. et al. (1994). Polychlorinated biphenyls, 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (p,p’-ddt) and 1,1-dichloro-2,2-bis(p-chlorophenyl)-ethylene (p,p’-dde) in human plasma related to fish consumption. Archives of Environmental Health, 49: 477-486.

Bernama (2010). Syabas tutup sementara loji semenyih berikutan pencemaran.

Bhupander, K. and D.P. Mukherjee (2011). Assessment of human health risk for arsenic, copper, nickel, mercury and zinc in fish collected from tropical wetlands in India. Advances in Life Science and Technology, 2: 13-25.

Burger, J., Gochfeld, M., Shukla, T., Jeitner, C., Burke, S., Donio, M. et al. (2007). Heavy metals in pacific cod (Gadus macrocephalus) from the Aleutians: Location, age, size, and risk. Journal of Toxicology and Environmental Health, Part A 70: 1897-1911.

Burger, J. and M. Gochfeld (2009). Perceptions of the risks and benefits of fish consumption: Individual choices to reduce risk and increase health benefits. Environmental Research, 109: 343-349.

Dewailly, E., Ryan, J.J., Laliberté, C., Bruneau, S., Weber, J.P., Gingras, S. et al. (1994). Exposure of remote maritime populations to coplanar PCBs. 102: 205-209.

Díez, S., Delgado, S., Aguilera, I., Astray, J., Pérez-Gómez, B., Torrent, M. et al. (2009). Prenatal and early childhood exposure to mercury and methylmercury in Spain, a high-fish-consumer country. Arch Environ Contam Toxicol, 56: 615-622.

DOE (2006). Malaysia environmental quality report 2006 in Impak, Kuala Lumpur.

EC (2004). Assessment of the dietary exposure to arsenic, cadmium, lead and mercury of the population of the EU member states. (Reports on Tasks for Scientific Cooperation). European Commission.

Han, B.-C., Jeng, W.-L., Hung, T.-C. and M.-S. Jeng (1994). Copper intake and health threat by consuming seafood from copper-contaminated coastal environments in Taiwan. Environmental Toxicology and Chemistry, 13: 775-780.

Han, B.-C., Jeng, W.-L., Hung, T.-C., Ling, Y.-C., Shieh, M.-J. and L.-C. Chien (2000). Estimation of metal and organochlorine pesticide exposures and potential health threat by consumption of oysters in Taiwan. Environmental Pollution, 109: 147-156.

Jang, C.S., Liu, C.W., Lin, K.H., Huang, F.M. and S.W. Wang (2006). Spatial analysis of potential carcinogenic risks associated with ingesting arsenic in aquacultural tilapia (Oreochromis mossambicus) in blackfoot disease hyperendemic areas. Environmental Science & Technology, 40: 1707-1713.

Khairuddin, M.I. and A. Abd Malek (2001). Program pencegahan pencemaran dan peningkatan kualiti air sungai langat. Proceeding simposium penyelidikan lembangan langat 2001., 2002, (Mazlin M, Shaharuddin I, Ahmad Fariz MA, Abdul Hadi HS, Sarah AAGA eds)Lestari, UKM, Bangi.

Khaled, A. (2004). Seasonal concentrations of some heavy metals in muscle tissues of Siganus rivulatus and Sargus sargus fish from El-mex Bay and eastern harbour, Alexandria, Egypt. Egyptian Journal of Aquatic Biology and Fisheries, 8: 65-81.

Laar, C., Fianko, J.R., Akiti, T.T., Osae, S. and A.K. Brimah (2011). Determination of heavy metals in the black-chin tilapia from the Sakumo Lagoon, Ghana. Research Journal of Environmental and Earth Sciences, 3: 8-13.

Liao, C.M. and M.P. Ling (2003). Assessment of human health risks for arsenic bioaccumulation in tilapia (Oreochromis mossambicus) and large-scale mullet (Liza macrolepis) from blackfoot disease area in Taiwan. Arch Environ Contam Toxicol, 45: 264-272.

Lim, T.O., Ding, L.M., Zaki, M., Suleiman, A.B., Fatimah, S., Siti, S. et al. (2000). Distribution of body weight, height and body mass index in a national sample of Malaysian adults. Medical Journal of Malaysia, 55: 108-128.

Liu, C.W., Liang, C.P., Huang, F.M. and Y.M. Hsueh (2006). Assessing the human health risks from exposure of inorganic arsenic through oyster (Crassostrea gigas) consumption in Taiwan. Science of the Total Environment, 361: 57-66.

Liu, C.W., Liang, C.P., Lin, K.H., Jang, C.S., Wang, S.W., Huang, Y.K. et al. (2007). Bioaccumulation of arsenic compounds in aquacultural clams (Meretrix lusoria) and assessment of potential carcinogenic risks to human health by ingestion. Chemosphere, 69: 128-134.

Lushenko, M.A. (2010). A risk assessment for ingestion of toxic chemicals in fish from Imperial beach, California: San Diego State University.

Mallin, M., McIver, M., Fulton, M. and E. Wirth (2011). Elevated levels of metals and organic pollutants in fish and clams in the Cape Fear River watershed. Arch Environ Contam Toxicol, 61: 461-471.

Mansilla-Rivera, I. and C. Rodríguez-Sierra C. (2011). Metal levels in fish captured in Puerto Rico and estimation of risk from fish consumption. Arch Environ Contam Toxicol, 60: 132-144.

Mishra, S., Bhalke, S., Saradhi, I.V., Suseela, B., Tripathi, R.M., Pandit, G.G. et al. (2007). Trace metals and organometals in selected marine species and preliminary risk assessment to human beings in Thane Creek area, Mumbai. Chemosphere, 69: 972-978.

Mohamed, A.F., Yaacob, W.Z.W., Taha, M.R. and A.R. Samsudin (2009). Groundwater and soil vulnerability in the Langat Basin, Malaysia. European Journal of Scientific Research, 27: 628-635.

Mokhtar, M.B., Aris, A.Z., Munusamy, V. and S.M. Praveena (2009). Assessment level of heavy metals in penaeus monodon and oreochromis spp in selected aquaculture ponds of high densities development area. European Journal of Scientific Research, 30: 348-360.

Núria, F.H., Martí, N., Pablo, D.L.I., Diogène, Jorge and L.D. José (2009). Risk assessment of trace elements from consuming local seafood by the population living in the Ebro river basin in Catalonia, Spain. ICMSS09 – Nantes.
OEHHA (2007). Fish. Available: http://www.oehha.ca.gov/fish.html [accessed 16 August 2012].

OEHHA (2011). Adoption of the revised air toxics hot spots program technical support document for cancer potency factors.

OhioEPA (2008). Ecological risk assessment guidance document. Lazarus Government Center, 50 West Town St., Suite 700, Columbus:Division of Environmental Response and Revitalization.

Onsanit, S., Ke, C., Wang, X., Wang, K.-J. and W.-X. Wang (2010). Trace elements in two marine fish cultured in fish cages in Fujian province, China. Environmental Pollution, 158: 1334-1342.

Paquin, R.R., Farley, K., Santore, R.C., Kavvadas, C.D., Mooney, K.G., Winfield, R.P. et al. (2003). Metals in aquatic systems: A review of exposure, bioaccumulation, and toxicity models. Society of Environmental Toxicology and Chemistry (SETAC), Pensacola.

PNSB (2010). 2009 Annual Report. Kuala Lumpur.

Said, K.S., Shuhaimi, M. and A. Kutty (2012). The water quality and metal concentrations of Cempaka Lake, Selangor, Malaysia. In: Management of natural resources, sustainable development and ecological hazards (Brebbia, C.A., Zubir, S.S., eds). WIT Press.

Schmitt, C., Brumbaugh, W., Linder, G. and J.E. Hinck (2006). A screening-level assessment of lead, cadmium, and zinc in fish and crayfish from northeastern Oklahoma, USA. Environmental Geochemistry and Health, 28: 445-471.

Statistic of Agro Food (2010). Statistic of agro food. In press.

Storelli, M.M. (2008). Potential human health risks from metals (Hg, Cd and Pb) and polychlorinated biphenyls (PCBs) via seafood consumption: Estimation of target hazard quotients (THQs) and toxic equivalents (TEQs). Food and Chemical Toxicology, 46: 2782-2788.
 
 
Svensson, B.G., Nilsson, A., Jonsson, E., Schütz, A., Akesson, B. and L. Hagmar (1995). Fish consumption and exposure to persistent organochlorine compounds, mercury, selenium and methylamines among Swedish fishermen. Scandinavian Journal of Work, Environment & Health, 21: 96-105.

Taweel, A., Othman, M.S. and A.K. Ahmad (2011). Heavy metals concentration in different organs of tilapia fish (Oreochromis niloticus) from selected areas of Bangi, Selangor, Malaysia. African Journal of Biotechnology, 10: 11562-11566.

The Star (2006). Environment Part 03/28/2006.

Tu, N.P.C., Ha, N.N., Ikemoto, T., Tuyen, B.C., Tanabe, S. and I. Takeuchi (2008). Regional variations in trace element concentrations in tissues of black tiger shrimp Penaeus monodon (Decapoda: Penaeidae) from South Vietnam. Marine Pollution Bulletin, 57: 858-866.

USEPA (2011). USEPA regional screening level (RSL) summary table. Washington, DC.

USEPA (2012). Fish consumption advisories. Available: http://water.epa.gov/scitech/swguidance/fishshellfish/fishadvisories/index.cfm (accessed 16 August 2012).

USEPA (2000). Guidance for assessing chemical contaminant data for use in fish advisories: Volume 1. In: Fish Sampling and Analysis. 3rd Edition. Office of Science and Technology of Water, Washington:DC EPA 823-B-00-007.

USEPA (2012). Waste and cleanup risk assessment.

Usero, J., González-Regalado, E. and I. Gracia (1997). Trace metals in the bivalve molluscs Ruditapes decussatus and Ruditapes philippinarum from the Atlantic coast of southern Spain. Environment International, 23: 291-298.

Yusof, M.F. (2007). The water crisis in Selangor? – A million population will be affected by ammonia contaminated river Utusan.

Yusuf, M.A. and M. Nordin (2003). River water quality assessment and ecosystem health: Langat river basin, Selangor, Malaysia. In: Rapport, D.J., Lesley, W.L., Rolston, D.E., Nielson, N.O., Quelset, C.O. and Damania, A.D. (eds). Managing for healthy ecosystems. Lewis/CRC Press, Boca Raton, Florida.

Zhou, H.Y., Cheung, R.Y.H., Chan, K.M. and M.H. Wong (1998). Metal concentrations in sediments and tilapia collected from inland waters of Hong Kong. Water Research, 32: 3331-3340.
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