Organotin levels in seafood and its implications for health risk in high-seafood consumers

Abstract

Fish and fishery products are considered as the main source of organotin compounds (OTC). Unfortunately, little national contamination data is available to assess food exposure of organotins from French consumers. To provide a more accurate estimate of risks to human health, the butyltin, phenyltin and octyltin compounds sampling in four French coastal areas were measured in 159 composite samples (96 fresh and frozen fish, 28 mollusks, 14 crustaceans, 1 echinoderm, 11 canned foods, 4 smoked fish, 5 prepared seafood-based dishes) by capillary gas chromatography coupled with a microwave induced plasma atomic-emission spectrometer (CGC–MIP-AES). In these samples, butyltins were usually predominant and the range of the contamination levels was generally below those of earlier studies (fish: mean 5.6; min–max 1.1–23 μg/kg; fishery products: mean 6; min–max 0.8–14 μg/kg). Fish, especially tuna, salmon, mackerel, saithe/coalfish and cod were largely the main contributors (38%) to the total organotin exposure. With the supplementary contribution of great scallop, surimi, squid and oysters, the exposure exceeded 50% in all. However, the utmost OTC exposure was lesser than 47% of the provisional tolerable weekly intake [EFSA (European Food Safety Agency). Opinion of the Scientific Panel on Contaminants in the food chain on a request from the Commission to assess the health risks to consumers associated with exposure to organotins in foodstuffs. (Question N°EFSA-Q-2003-110). The EFSA Journal, 102, 1–119, 2004. http://www.efsa.eu.int]. Nobody would exceed this limit. Finally, as this study has some limitations and since some other sources and health effects have not been clearly evaluated, it appears rational from public health and environmental viewpoints to continue to reduce the OTC levels in the environment.

Introduction

Occupational exposure represents the greatest exposure to organotin compounds (OTC). Food, especially fish and fishery products is considered to be the main sources. The main species are likely to be tri-substituted compounds (tributyltin TBT and triphenyltin TPT), which have been used extensively as biocides in wood preservatives, in antifouling paints for boats and as pesticides (ATSDR (Agency for Toxic Substances and Disease Registry), 2003, EFSA (European Food Safety Agency), 2004, Duft et al., 2005, AFSSA (Agence Française de Sécurité Sanitaire des Aliments), 2006). Mono- and di-substituted are generally used in mixtures in various amounts as polyvinyl-chlorides stabilizers (PVC). TBT compounds are on the list of priority substances in the field of water policy (EC, 2001). Antifouling paints have been restricted in many countries because of the recognized adverse effects of these compounds on both humans and aquatic ecosystems. Regulation 782/2003/EC bans the application of OTC on ships as from 7/1/2003 and to eliminate their presence on ships from 1/1/2008 (EC, 2003). Nevertheless, because these compounds are persistent in the environment and tend to accumulate through the food chain (Duft et al., 2005), reservoir sources may continue to contribute substantially to human exposure of these compounds for a long time.

Recently, many toxicological evaluations were published (WHO-IPCS, 1999a, WHO-IPCS, 1999b, WHO-IPCS, 2001, WHO-IPCS, 2006, ATSDR (Agency for Toxic Substances and Disease Registry), 2003, EC, 2004, EFSA (European Food Safety Agency), 2004, AFSSA (Agence Française de Sécurité Sanitaire des Aliments), 2006). A no observed adverse effect level (NOAEL) for immunotoxicity of 0.025 mg/kg bw/day was identified for TBT oxide from chronic feeding studies in rats (Vos et al., 1990, Cooke et al., 2004, Tryphonas et al., 2004). An oral reference dose (RfD), a guidance value for oral exposure, and an intermediate-duration oral minima risk level (MRL) of 0.0003 mg/kg/day for tributyltin oxide have been successively derived (US EPA, 1997; WHO-IPCS, 1999b, ATSDR (Agency for Toxic Substances and Disease Registry), 2003). An uncertainty factor of 100 was applied to the NOAEL (10 for animal to human extrapolation and 10 for human variability). Because tributyltin (TBT), dibutyltin (DBT), triphenyltin (TPT) and dioctyltin (DOT) exert their immunotoxic effects by similar mode of action and potency, it seemed reasonable to establish a group tolerable daily intake (TDI) for these OTC (EFSA (European Food Safety Agency), 2004, EC, 2004). In the absence of specific studies on combined effects it seemed justified to consider the immunotoxic effects of these compounds as additive. By applying a safety factor of 100, a group TDI of 0.25 μg/kg bw for TBT, DBT, TPT and DOT compounds was established (based on TBT oxide molecular mass, this group TDI is 0.1 μg/kg bw when expressed as Sn content or 0.27 μg/kg bw when expressed as TBT chloride). This group TDI seemed relevant by the AFSSA experts (AFSSA, 2006).

Even though some studies have recently estimated OTC exposure from ingestion of especially fish and shellfish (Cardwell et al., 1999, Kannan et al., 1995, Keithly et al., 1999, WHO-IPCS, 2001, Belfroid et al., 2000, SCOOP task 3.2.13, 2003, EFSA (European Food Safety Agency), 2004, OT-SAFE, 2004, Tesfalidet, 2004, Lee et al., 2005, FSA (Food Safety Agency), 2005, AFSSA (Agence Française de Sécurité Sanitaire des Aliments), 2006, Comprendo (Comparative Research on Endocrine Disrupters), 2006), the amount and percent of exposure from food in the French population has not been characterized well.

The aim of the present study is to compensate for this current situation. The food sample size is largely higher than in earlier studies and above all more representative of French high-consumers, as well as the consumption survey used to cross these occurrence data to estimate the exposure is much more accurate than those previously used. For the first time, this paper characterizes specifically the French population's OTC exposure of male and female adults (18–64 years), seniors (+ 65 years) and women of child-bearing age (18–44 years) from seafood.