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Sri Lankan chemical issues
Need of an action for heavy metal contamination in Negombo lagoon

Need of an action for heavy metal contamination in Negombo lagoon

Gathered by: Chalani Rubesinghe

  • Introduction
  • The heavy metal contamination and their consequences in brief
  • Situation in the Negombo lagoon, Sri Lanka
  • The requirement of a policy
  • References 


Heavy metals by definition are the metals that have a density of more than 5g/cm3. There are about 60 heavy metals discovered so far. In trace levels, while some of them have a nutritional value such as Copper, Zinc, Manganese, Nickel, Chromium and Iron. The same can turn toxic in higher concentrations (eg. Copper, Zinc, Manganese) 5, 13. Some like lead, cadmium and mercury can course toxicity even in trace levels of contamination.5

Literature reveals number of studies that have been carried out in Sri Lanka with regard to the heavy metal contamination7-9, 12-14, 16-20. The review on environmental pollution in Sri Lanka summarizes the different paths of heavy metal contamination and their effects on human with reference to several research studies16. The water quality analysis of Sri Lanka revealed the state of pollution in twelve selected water bodies including Kelani River, Kelani estuary, Negombo lagoon, Bolgoda Lake, Koggala lagoon, Kotmale reservoir, Kala wewa and Rajangana tank, Kandy Lake, Meda ela, Hamilton canal and Hikkaduwa marine sanctuary20.

Although studies reveal of certain adverse situations and possibilities of growing such a threat in the Negombo lagoon, there has never been a follow-up on the matter. In 1991, Mercury has been detected in water samples of the lagoon in a level of 20. In 2008 this level of mercury detected in sediments collected from Negombo lagoon was between 0.6- 0.75ppm12. It shows a large increase in the level with respect to only mercury. Therefore the best will be to pay attention on this matter before it reaches the toxic levels to human and create another case like “Minamata disease” in Japan.  This report thereby will be an effort on dragging the attention of relevant parties on one of the largest water bodies in Sri Lanka with a threat of human contamination through fish consumption.

The heavy metal contamination and their consequences in brief

The heavy metal contamination has been a problem for human since the time of civilization; history suggests that lead poisoning must have affected the collision of the Rome Empire1. The case of Minamata disease in Japan which produced nearly 10 000 victims  of mercury poisoning2, the incident of Love canal in America3 and furthermore Bhopal: the Union Carbide gas leak, Chernobyl: Russian nuclear power plant explosion, Seveso: Italian dioxin crisis. The 1952 London smog disaster, Major oil spills of the 20th and 21st century, The Baia Mare cyanide spill, The European BSE crisis, Spanish waste water spill and The Three Mile Island near nuclear disaster are  famous cases of tragic ends of heavy metal contamination coursed by anthropogenic environmental pollution3.

In talking about the disasters, it will be worth to aware on effects of heavy metals on human body. The table 1 indicates the toxicity of few heavy metals and their consequences with the level of exposure.

In addition various small-scale studies are continuously monitoring the heavy metal contamination in water bodies, soil and sediments6, air and food items.

Table 1: Most Commonly Encountered Metals and Their Toxicity4

Metal Acute Chronic Toxic Concentration
Arsenic Nausea, vomiting,

“rice-water” diarrhea,


painful neuropathy


hypopigmentation/ hyperkeratosis,

cancer: lung, bladder, skin, encephalopathy

24-h urine:

≥50 µg/L urine, or

100 µg/g creatinine

Bismuth Renal failure; acute tubular necrosis Diffuse myoclonic encephalopathy No clear reference standard
Cadmium Pneumonitis (oxide fumes) Proteinuria, lung cancer, osteomalacia Proteinuria and/or ≥15 µg/ g creatinine
Chromium GI hemorrhage, hemolysis, acute renal failure (Cr6+ ingestion) Pulmonary fibrosis, lung cancer (inhalation) No clear reference standard
Cobalt Beer drinker’s (dilated) cardiomyopathy Pneumoconiosis (inhaled); goiter Normal excretion:

0.1-1.2 µg/L (serum)
0.1-2.2 µg/L (urine)

Copper Blue vomitus, GI irritation/ hemorrhage, hemolysis, MODS (ingested); MFF (inhaled) vineyard sprayer’s lung (inhaled); Wilson disease (hepatic and basal ganglia degeneration) Normal excretion:

25 µg/24 h (urine)

Iron Vomiting, GI hemorrhage, cardiac depression, metabolic acidosis Hepatic cirrhosis Nontoxic: < 300 µg/dL Severe: >500 µg/dL
Lead Nausea, vomiting, encephalopathy (headache, seizures, ataxia, obtundation) Encephalopathy, anemia, abdominal pain, nephropathy, foot-drop/ wrist-drop Pediatric: symptoms or [Pb] ≥45 µ/dL (blood); Adult: symptoms or [Pb] ≥70 µ/dL[1]
Manganese MFF (inhaled) Parkinson-like syndrome,

respiratory, neuropsychiatric[2]

No clear reference standard
Mercury Elemental (inhaled): fever, vomiting, diarrhea, ALI;

Inorganic salts (ingestion): caustic gastroenteritis

Nausea, metallic taste, gingivo-stomatitis, tremor, neurasthenia, nephrotic syndrome; hypersensitivity (Pink disease) Background exposure “normal” limits:

10 µg/L (whole blood); 20 µg/L (24-h urine)

Nickel Dermatitis; nickel carbonyl: myocarditis, ALI, encephalopathy Occupational (inhaled): pulmonary fibrosis, reduced sperm count, nasopharyngeal tumors Excessive exposure:

≥8 µg/L (blood)

Severe poisoning:

≥500 µg/L (8-h urine)

Selenium Caustic burns, pneumonitis, hypotension Brittle hair and nails, red skin, paresthesia, hemiplegia Mild toxicity: [Se] >1mg/L (serum); Serious: >2 mg/L
Silver Very high doses: hemorrhage, bone marrow suppression, pulmonary edema, hepatorenal necrosis Argyria: blue-grey discoloration of skin, nails, mucosae Asymptomatic workers have meant [Ag] of 11 µg/L (serum) and 2.6 µg/L (spot urine)
Thallium Early: Vomiting, diarrhea, painful neuropathy, coma, autonomic instability, MODS Late findings: Alopecia, Mees lines, residual neurologic symptoms Toxic: >3 µg/L (blood)
Zinc[3] MFF (oxide fumes); vomiting, diarrhea, abdominal pain (ingestion) Copper deficiency: anemia, neurologic degeneration, osteoporosis Normal range:

0.6-1.1 mg/L (plasma)

10-14 mg/L (red cells)

Situation in the Negombo lagoon, Sri Lanka

Negombo lagoon is one of the largest lagoon environment located in the western Sri Lanka. With an area nearly 3 164 ha (31.64 km²) this lagoon supports vast number of fishing families20.

The literature reveals on the contamination with regard to several heavy metals in the area. Being the receiver of several freshwater bodies that pass through the industrial zones like Dandugam oya, Ja-Ela, Hamilton canal and the Dutch canal, this lagoon collects a large sum of pollutants.

Table 2: Metal levels recorded by Indrajith et al., 2008 and GCEC ,1991 for Negombo lagoon

Pb Cu Cd Cr Hg
1991  Not measured 0.01 0.01 <0.01 <0.02
2008 10.78 11.24 0.08 41.49 0.75

The people living around the lagoon are mostly fishermen and their families, which are engaged in fishing activities.  It was found that their unawareness on hazardous chemicals expose them to various harmful chemicals. The best example was that they throw used CFL and fluorescent bulbs in to the lagoon. On one hand this is dangerous for fishermen who operate brush piles that often walk in the lagoon and also are harmful in the sense of mercury contamination.

It was revealed that often fishermen find fish from large to small-sized, with melting muscles. Some dead and some alive. Sometimes the cooked fish smells crude oil and the curry appears with oil layer on top, even when they were cooked without gills or gut content. According to the explanation of Dr. Krishnarajah, a senior lecturer in zoology, Open University of Sri Lanka, this is due to accumulation of sulfur in the adipose tissues of fish. A simple solution can be engaged such as, first boil the fish, throw out that water and then cook the meat. Still this may not remove the heavy metals accumulated in the fish. Therefore these issues should be given attention before the fish from Negombo lagoon being rejected.

For these people have been associated with lagoon fishery and eating fish for years they may not change the habit of eating fish. Thus the best solution lies in the site recovery. Either scientific research should focus on removal of heavy metals in water bodies including sediments or on proper mechanism of removing heavy metals from fish muscles as parts like liver and gills are often removed when cooked. The science community should get together in bringing out and implementation of solutions. Purification mechanisms, possible cleaning techniques for surrounding pollutant sources, promoting natural cleaners will be the best solutions to save people from the possible threats of not only mercury but also other pollution sources as well.

figure1Figure 1: Levels of selected heavy metals detected in Etroplus suratensis

According to table 2, it is seen that even though the levels of metals are significantly law in water, the detected levels in fish (Figure 1) are higher. This is due to the bio accumulation. The metals are gradually deposited in body tissues of fish. Further it shows that fish liver accumulates the highest amount of metals than gills or muscles. Similar situation can be observed in Ambassis commersoni (Katilla) in figure 2. All these metals are transferred to the predator fish and accumulated in higher amounts. The human being at the top of the food chain accumulates and suffocates from all these chemicals.

figure2Figure 2: Levels of selected heavy metals detected in Ambassis commersoni

Experiments of all kind prove that lagoon is contaminated. It was recorded That Koraliya or Etroplus suratensis in Negombo lagoon can contain 0.1 mgkg-1 of fish consumed only the muscle part12. In 2000, the US National Research council established a “reference doses of 1000 micro grams per kilogram of hair”21. Families of the fishermen are the regular consumers of fish. Often they consume all three meals throughout the week except on Sundays. Unlike the people around the country, who consumes mostly marine or lake fish from different parts of the country, these families consume fish that are seasonally abundant in the lagoon that caught by the fishermen. For a person who consumes all meals of fish supposing he consumes only Korali even if he eats 100g per meal he consumes nearly 2kg per week thus ingest nearly 0.2mg/kg-1 of Hg.  This way it will not take 5 weeks for a person to ingest 1.0mg/kg-1 of mercury into his body.  Even if we consider the meals of consumption to half the value per week, it will only take 2.5 months for a person to ingest this amount of mercury which has no value as nutrition inside the body. Yet harms the nerves system of the fetus in a pregnant women and an ordinary human21.

While one part of the country is being attacked by heavy metal contamination (probably due to pesticide contamination) the others can be affected from fish contamination. This raises the question whether we are waiting till we recover another critical situation like CKDue (Chronicle Kidney Disease due to unknown ethical) to take an action on fish in the Negombo lagoon.

In addition to the pollution of water bodies by pesticides, it was found that broken pesticides bottles are used in bakery fireplaces which are a possible method of contamination of bakery items with vaporizing chemicals.

Once released to the environment, not only the water but also the sediments can be contaminated. This sediment then passes through the fish to human mostly initiating from grazers and bottom feeders. Human consumption of these fish ingests a certain amount and consumption of predatory fish multiplies the amount of any heavy metal or pollutant contaminated on these fish.

In Sri Lanka, though there are studies carried out by various scientists on heavy metal contamination and their consequences, they do not communicate to the general public. Thus the people around lagoon are unaware of the threat they are vulnerable to.

CEJ (Center for Environmental Justice) in their conversations with general public in the area has found that the community around the lagoon is totally unaware of heavy metal contamination.

“I am the first fishermen in this area; I see that the lagoon is now polluted by the effluents from garments and hotels but we cannot change the habit of eating fish” Juwan seeya of Thalahena, Negombo.

“I have often observed fish with melting muscles, they are small to large fish floating dead and sometimes it’s a  pain to see them swimming with a side of the fish being melted” Berty Perera of Pitipana, Negombo.

“All the gutters are opened to the lagoon, even when government supplies the septic tanks, people do not bother to fix them. All the factories that repair engines release effluent water to the lagoon” Marcus Anthony, Pitipana south, Negombo.

Though they know the lagoon is polluted by effluents of garments, factories and the boats operated in the lagoon, it is not enough knowledge for them to take any action on that. Though they are aware of that oil has been washed to the lagoon thus cooked fish taste oil, the bulbs been thrown away could cause damage to fishermen, they are not bothered to act on these matters. According to all the research data, these people are exposed to the heavy metal contamination through fish and all its consequences.

The requirement of a policy

In the words of a Negombo lagoon vicinity resident, Ramesh Keerithisinghe of Dalupotha, Negombo;

“As I believe the rules and regulations have not been complied by any of the fishing boats that go to catch fish. In fact they dispose all their oily residues plus plastic and other garbage directly over the side. This consequently pollutes the water in the lagoon and the fish get poisoned. Other than the prescribed scenario, lot of untreated gutters have been directed to the lagoon as anybody who walks pass can witness all of them goes into the water. So my suggestions are to;

  • Implement the current rules to practice, which would avoid the damage made by the fishing boats, trawlers etc.
  • The gutters must be reroute through treatment plants prior to discharge into the water, so authorities should wake up and take strict action against those who violate the rules.

If above two points will be addressed most of the detriment and future disaster could be avoided”.

Thus, in order to prevent possibilities of a future tragedy the policy level attention is required in the fields of;

  • Monitoring the standards of fishing vassals operated and it’s effluents to the lagoon.
  • Pre-treatment to oil contaminated water/ ballast water should made compulsory.
  • All the effluent systems to the canals should be monitored and shall fined
  • Authorities shall be forced to take immediate actions on cleaning up the lagoon and implementing a proper and practical waste management system in the lagoon area.


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