Preliminary Assessment of Total Mercury Content in Sri Lankan Seer Fish Scomberomorus commerson

Abstract

Fish is an important source of food providing valuable nutrients and many health benefits.Unfortunately, consumption of fish contaminated with mercury can expose humans tomercury poisoning. Mercury is a heavy metal pollutant that once released into theenvironment mostly affects aquatic ecosystems as it bioaccumulates and biomagnifies up thefood chain in large fish in higher trophic levels thereby causing serious health concerns forconsumers. Total mercury levels in the muscle tissue have been determined in some SriLankan marine fish of large size such as tuna, shark and sword fish.

This study is a preliminary assessment of total mercury content (TMC) in different tissues ofSri Lankan Seer fish Scomberomorus commerson. The TMC was determined separately inskin, red muscle, and white muscle. Samples were prepared by wet digestion method andanalysed using Atomic Absorption Spectrophotometric technique. Monthly Sampling wascarried out in the year 2012 from March-November. Overall eight fresh specimens ofconsistent length (70-80 cm) and weight class (2.25-2.50 kg) were purchased at randomsellers from the central fish market complex of the Ministry of Fisheries and AquaticResources Development, Peliyagoda.

All total mercury levels were below the international standard of 0.5 μg g-1 (US FDA).Significant variances were observed among the different tissue parts tested (p < 0.05).MeanTMC varied in decreasing order as, white muscle > red muscle > skin. Even though skin iscommonly assumed to contain higher levels of mercury, results from skin were the lowestrecorded in the study. The results reveal that mercury binding is tissue-specific andaccumulates differently in different tissue types. It has been reported that mercury builds upin the muscle tissue and cannot be removed by removing the skin and trimming away fattyareas of the fish.

The estimated weekly intake (EWI) of mercury by average consumers in Sri Lanka wascalculated as 0.0306 μg kg-1 for S. commerson based on the average adult (50 kg) consuming16.57 g day-1 of fish. This is below the provisional tolerable weekly intake of 5 μg kg-1 bodyweight established for total mercury (WHO).

Total mercury levels are dependent on age and consequently length of fish. From thispreliminary study one can conclude that Sri Lankan Seer fish Scomberomorus commersonbelow the 80.0 cm total length is safe from undue contamination of mercury. However furtherextensive sampling is necessary to establish this conclusion.