Distribution of organochlorine pesticides and heavy metal residues in fish and shellfish from Calicut region, Kerala, India

Abstract

Fish collected from five different locations from the Calicut region, India were analysed for the levels of organochlorine pesticides (OCPs) and heavy metal (HM) residues in order to elucidate the status of these chemical contaminants in fish and shellfish meant for human consumption. The highest concentrations of OCPs detected in the edible portion of fish were 10.47, 70.57 and 28.35 ng g⁻¹ wet weight, in marine, brackish water and freshwater, respectively. BHC and heptachlor epoxide formed the major share of OCPs in the marine fish while BHCs contributed to the major share in the freshwater and brackish water fish. The DDT (sum of DDT and its metabolites) ranged from 0.05 to 8 ng g⁻¹ in the samples irrespective of the habitat. Among the HMs, Cu, Zn, Mn and Cr were present in the samples irrespective of the place of collection. About 22% of the samples from the freshwater area contained marginally higher lead content above the legal limit of 0.2–0.4 μg g⁻¹. The Cr content ranged from 0.1 to 1.1 μg g⁻¹ in the fish with marginally higher content in the fish from freshwater and marine regions (0.55–1.1 μg g⁻¹). Mercury was detected in the samples (55%) from marine habitat only. The concentrations of OCPs and HMs in the samples, in general, were below the maximum residual level recommended by various organizations.

Introduction

OCPs are ubiquitous and persistent pollutants due to bioaccumulation in the food chain either as such or as their metabolites, thus causing concern on the animals at the top of the food chain. Though many persistent OCPs are restricted or banned in developed countries, they are still produced and used to a large extent in developing counties. Agriculture and health sector are the major consumers of pesticides in India. About 145 pesticides were registered in India in the mid nineties and the production was approximately 85 000 metric tons (Gupta, 2004). Aldrin, BHC, chlordane, endrin heptachlor and dieldrine are included in the list as banned pesticides and DDT and lindane are included in the list of pesticides restricted for use in India by the Central insecticides Board and Registration committee.

Even though India occupies fourth position in terms of fish production, the per capita consumption of fish in India is only 4.8 kg year⁻¹ (http://www.st.nmfs.gov/st1/fus/us04/08perita2004.pdf). India exports shrimp and fish to the world market and majority of the population along the coastal regions consume fish.

Presence of OCPs in water and sediments has been extensively studied (Haynes and Johnson, 2000, Haynes et al., 2000, Guruge and Tanabe, 2001, Fillmann et al., 2002, Doong et al., 2002). Monitoring of fish and shellfish serves as an important indicator of the water ecosystem (Fairey et al., 1997) where there is a vertical transport of OCP leading to accumulation in the benthic organisms (de Brito et al., 2002). Presence of some of the forbidden pesticides in shrimp at critical concentrations and the drastic metabolic changes related to its bioaccumulation in the tissue have been reported by Harrison et al. (1996). Reports are available in plenty indicating the presence of OCP in a variety of commercial fish species in many countries (Itawa et al., 1993, Kannan et al., 1995, Grobler et al., 1996, Pastor et al., 1996, Fairey et al., 1997, Anon, 1998, Spiric and Saisic, 1998, Chan et al., 1999, Monirith et al., 1999, Cleeman et al., 2000, Zhulidov et al., 2000, Jabbar et al., 2001). Compared to this only few reports are available on the presence of pesticide residues in fish from Indian waters (Radhakrishnan et al., 1986, Radhakrishnan and Antony, 1989, Radhakrishnan, 1994a, Das et al., 2002, Karuppiah et al., 2005).

Heavy metals from natural and anthropogenic sources continuously enter the aquatic ecosystem where they pose serious threat because of their toxicity, long persistence, bioaccumulation and biomagnification in the food chain (Papagiannis et al., 2004). Increased industrialization and agricultural activities contribute to their increased levels in the natural waters (Tarras-Wahlberg et al., 2001). Fish being at the higher level of the food chain accumulate large quantities of these xenobiotics and the accumulation depends up on the intake and the elimination from the body (Karadede et al., 2004). However, the accumulation of heavy metals in fish and other aquatic lives is of great importance to man as fish is consumed by a large section of the population. Heavy metal accumulation in different species depends on the feeding habits (Amundsen et al., 1997, Romeoa et al., 1999), size and length of the fish (Al-Yousuf et al., 2000) and more particularly their habitat (Canli and Atli, 2003). Among the different aquatic lives clams and mussels accumulate large quantities of heavy metals due to their habitat and feeding habits.

Reports on heavy metal contamination in fish (Chan, 1995, Edwards et al., 2000, Kucuksezgin et al., 2002, Watanabe and Tanabe, 2003) oysters and clams (Lakshmanan, 1988, Radhakrishnan, 1994b, Trocine and Trefry, 1996, Senthilnathan and Balasubramanian, 1998), seals (Watanabe et al., 2002), whale (Law et al., 1997, Mendez et al., 2002) and fish products (Voegborlo et al., 1999) are available in plenty indicating a wide variation in the level of these toxicants in the organisms which could be attributed to many factors. Therefore it is very important that a carefully planned documentation taking in to account the possible variables is essential for generating a reliable database on the levels of these toxicants in aquatic organisms. For elucidating the present status of chemical contaminants viz., OCPs and HM in fish and shellfish of commercial importance, samples were collected from different habitats from the Calicut region, Kerala, India.