World Aquaculture September 2018

WWW.WA S.ORG • WORLD AQUACULTURE • SEP TEMBER 2018 67 ( C O N T I N U E D O N P A G E 6 8 ) formation of formaldehyde in fish by enzymatic reaction, other biochemical reactions such as oxidation of lipids may also lead to formaldehyde formation, although the amount of formaldehyde produced by those reactions does not cause any harm. Toxic Effects in Humans Formaldehyde is a metabolic product that forms in all cells during the metabolism of amino acids such as serine, glycine, methionine and choline. However, formaldehyde is a highly toxic substance, with human carcinogenicity. Chronic inhalation can result in respiratory symptoms and irritation of eyes, nose and throat (Zhang et al . 2009a). Increased exposure of this chemical can increase the risk of cancers of the pharynx, nasopharynx and brain, as well as dermatitis and allergic reactions. In a study of industrial workers in the USA exposed to formaldehyde, a statistically significant excess of deaths from nasopharyngeal cancer was observed in comparison with the US national population, with statistically significant exposure- response relationships for peak exposure and cumulative exposure (Hauptmann et al. 2004). Ingestion of 30 mL of formalin can cause death in an adult human. Ingestion may cause corrosive injury to the gastrointestinal mucosa with nausea, vomiting, pain, bleeding and perforation. These injuries are most pronounced in the pharyngeal mucosa, epiglottis and esophagus. Systemic effects include metabolic acidosis, central nervous system depression and coma, respiratory distress, renal failure and associated cancer and tumor development (Wooster et al. 2005). Recently, an International Agency for Research on Cancer has classified formaldehyde as a Group 1 carcinogen for humans (IARC 2012). The US Environmental Protection Agency (EPA) proposed maximum daily dose reference (RfD) level of formaldehyde of 0.2 µg/g body weight (Wang et al . 2007). The Italian Ministry of Health proposed maximum formaldehyde level in the cod family of 60 µg/g and in crustaceans of 10 µg/g (Bianchi et al . 2007). Reports of Formalin Presence in Fish Pressure to maintain the utmost freshness puts pressure on producers, processors and marketers to take short-cuts. Reports of formalin detection in fish and shellfish are given in Table 1. Reports summarized in Table 1 indicate that incidence of formalin in fish is mainly observed in Asian countries. Of these, probably Bangladesh suffered most seriously. The Bangladesh Council of Scientific and Industrial Research (BCSIR) has developed a formalin detection kit for fish for field use and quick detection of formalin contamination in fish. In the meantime, Bangladesh has enforced many policies and laws to control formalin contamination in fish and other food items but news of formalin contamination of fish continues to surface. Now, reports of formalin in fish from north-east Indian states bordering Bangladesh such as Tripura, Manipur and Nagaland are also widespread as fish are imported to these areas fromBangladesh legally and illegally. Very recently, the Central Institute of Fisheries Technology (CIFT) located in Cochin, India also developed a formalin detection kit that will be available this year. Different methods are available for detection and quantification of formaldehyde in fish and other foods (Table 2). The spectrophotometric method is the classic detection method and one that continues to be used in many laboratories for research and analysis purposes. The HPLCmethod is very sensitive and accurate but, to protect consumers, it is out of reach or too expensive. The availability of cheap and rapid detection methods in kit formwould be a great help for common use. Solutions to Prevent or Reduce Formalin Contamination of Fish The following solutions may be effective to prevent or reduce formalin contamination in fish: TABLE 2. Various techniques available for formaldehyde detection. Formaldehyde detection method Substances Reference Spectrophotometric Fish Nash 1953, Castell and Smith 1973 Electrochemical biosensor Fish Herschkovitz et al. 2000, Aini et al. 2016 Biosensor Cell-based sensor Korpan et al. 2000 Conductometric enzyme biosensor Aqueous solution Dzadevych et al. 2001 SPMEGC- MS Fish products Bianchi et al. 2007 Chromatography (HPLC) Squid products Li et al. 2007 Colorimetry - Indang et al. 2009 Electronic nose technology Seafood Zhang et al. 2009 HPLC method Food, feed, fish Wahed et al. 2016, Bhowmik et al. 2017 Pressure to maintain the utmost freshness puts pressure on producers, processors and marketers to take short-cuts. Reports of formalin detection in fish and shellfish indicate that incidence of formalin in fish is mainly observed in Asian countries. Of these, probably Bangladesh suffered most seriously. The Bangladesh Council of Scientific and Industrial Research has developed a formalin detection kit for fish for field use and quick detection of formalin contamination in fish. In the meantime, Bangladesh has enforced many policies and laws to control formalin contamination in fish and other food items but news of formalin contamination of fish continues to surface.