Blood levels of organotin compounds and their relation to fish consumption in Finland

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Abstract

The objective of this study was to measure the concentrations of organotin compounds in the whole blood of Finnish male fishermen (n = 133), their wives (n = 94), and other family members (n = 73), and to investigate their associations with background variables. The concentrations were generally low, less than the limit of quantification (LOQ) for the vast majority of compounds and samples. Of the organotin compounds (mono-, di-, and tributyltin, mono-, di-, and triphenyltin, and dioctyltin), only triphenyltin was detected in more than just a few samples (in 37 of 300 samples, LOQ = 0.04 ng/ml). These were mainly the samples of fishermen (26/37) and their wives (10/37). For statistical analysis, concentrations of triphenyltin were divided into two categories, < LOQ and > LOQ. Of the different background variables, age and fish consumption contributed the most to the triphenyltin concentrations. When age and fish consumption (g/day) were divided into three categories, odds ratios comparing the highest with the lowest category were 3.88 for age (95% CI 1.36–11.09) and 3.48 for fish consumption (1.36–8.94), respectively. Compared with females, males had an odds ratio of 1.51 of having the concentration of triphenyltin > LOQ (0.72–3.14). To the best of our knowledge, this study confirmed for the first time with human samples that fish consumption can be associated with triphenyltin concentration in whole blood.

Introduction

Organotin compounds (OTCs) are a large class of compounds with widely varying properties, and they have been used for many different purposes. Mono- and di-substituted compounds (e.g., monobutyltin (MBT), dibutyltin (DBT), mono-n-octyltin (MOT), and di-n-octyltin (DOT)) are used extensively as heat and light stabilisers in the production of polyvinyl chloride (PVC) polymers and as catalysts in the manufacture of polyurethane and silicone elastomers. Also tri-substituted OTCs, tributyltin (TBT), and triphenyltin (TPhT) compounds have a wide range of uses mostly associated with their strong biocidal activity toward aquatic organisms, such as bacteria, fungi, algae, molluscs, and crustaceans. From the environmental point of view, most attention has been given to widespread TBT and TPhT pollution of waters, sediments, and aquatic biota resulting from their use in antifouling paints in boats and ships. TBT and TPhT are highly toxic to many aquatic species, and the most sensitive endocrine effect, imposex, occurs in some molluscs already at 1 ng/l levels of TBT (Fromme et al., 2005, Hoch, 2001).

A scientific panel of the European Food Safety Authority (EFSA) has assessed the health risks to consumers associated with exposure to OTCs in foodstuffs. Toxicologically relevant endpoints were immunotoxicity, reproductive and developmental toxicity, neurotoxicity, genotoxicity, and carcinogenicity. However, the most critical toxicological endpoint for risk assessment was considered to be immunotoxicity. Due to immunotoxicological similarities, a group Tolerable Daily Intake (TDI) of 250 ng/kg body weight was established for the sum of TBT, DBT, TPhT, and DOT (European Food Safety Authority, 2004). Recent evidence has also shown that TBT induces differentiation of adipocytes in vitro and increases adipose mass in vivo and may thus contribute to obesity (Grun and Blumberg, 2006, Grun et al., 2006, Inadera and Shimomura, 2005). Variable amounts OTCs have been found in many food types like beans, vegetables, fruits, eggs, milk, meat (Marcic et al., 2005, Qunfang et al., 2004), vines (Azenha and Vasconcelos, 2002), drinking water (Sadiki and Williams, 1999), and cookies (Takahashi et al., 1999). The origin of dietary OTCs is considered to be direct or indirect (e.g. through fertilising sludge) contact between different plastics and foodstuffs. Even though these food–plastic contacts may represent a notable route of OTC dietary exposure for humans, our recent Finnish market basket study (Rantakokko et al., 2006), two Japanese studies on the dietary intake of OTCs (Toyoda et al., 2000, Tsuda et al., 1995), a French study on the levels of OTCs in seafood and their health risk implications for high-seafood consumers (Guerin et al., 2007), and a study on farm, dairy, meat, and fish products (Kannan et al., 1995) have shown that fish and fish products are generally the main source of OTCs from ordinary foods. However, detailed information on the levels of OTCs in individual seafood species from Finnish water areas is still quite limited. In a study carried out in the vicinity of twelve cities in Finland, the sum of OTCs (mostly tri-substituted) in pooled pike muscle samples was 1–33 ng cation/g fresh weight in inland fish and 8–141 ng cation/g fresh weight in coastal fish (Mannio et al., 2005). In Finnish costal areas with a high density of shipping, OTC sums up to several hundred ng/g fresh weight in individual pike perch and burbot samples have been measured (Mannio et al., 2005, Vatanen and Niinimäki, 2005). A project aiming to study the OTC concentrations from the most commonly eaten domestic fish species from background and contaminated areas is currently underway.

Globally, the levels of OTCs in human blood samples have been measured only in a few studies. The sum of butyltins in 32 whole blood samples from central Michigan was, on average, 21.3 ng/ml (MBT 8.2 ng/ml, DBT 4.9 ng/ml, and TBT 8.2 ng/ml). MBT, DBT, and TBT were detected in 53%, 81%, and 70% of the samples examined, respectively. In addition to the ingestion of contaminated foodstuffs, butyltin compounds used as stabilisers or as biocides in household articles were regarded as a source (Kannan et al., 1999). Also in the United States, the sum of butyltins in 6 whole blood samples was, on average, 88 ng/ml (MBT 27 ng/ml, DBT 40 ng/ml, and TBT 21 ng/ml). MBT, DBT, and TBT were detected in all samples. A wide variety of butyltin sources, such as those mentioned above, were proposed to explain the unexpectedly high concentrations (Whalen et al., 1999). In Germany, butyltins, octyltins, and TPhT were analysed from the serum of 8 healthy volunteers. In striking contrast to US results, the concentrations of MBT and DBT were below the limit of detection (LOD = 0.02 ng/ml for all OTCs) in every sample, and TBT was only marginally above the LOD in 4 samples. All octyltins were below the LOD in every sample. The average concentration of TPhT was 0.31 ng/ml, and it was present in all samples, making TPhT the most abundant OTC in these samples (Lo et al., 2003).

The aim of this study was to measure OTC whole blood concentrations from a sample of Finnish Baltic Sea fishermen and their families, and to investigate the association with age, gender, and fish consumption. To the best of our knowledge, this is the first report where OT whole blood concentrations have been measured from a population likely to have a high OT exposure. This study is part of a larger Nutrition, Environment and Health study (the Fishermen study), which aims to evaluate the health benefits and risks of high fish consumption in a cohort of Finnish fishermen and their families (http://www.ktl.fi/portal/english/research__people___programs/environmental_health/research/chemicals/research_projects/fishermen/). During the project, whole blood/serum concentrations of many other contaminants, such as PCDD/Fs, PCBs, other groups of POPs, and methyl mercury are measured.

Section snippets

Recruitment, whole blood samples, and food frequency questionnaire

The Fishermen study cohort consists of all Finnish maritime and freshwater area fishermen, their wives, and other family members. The fishermen were identified from the Professional Fishermen Register, whereas the wives and other family members (fishermen's biological children, and biological siblings and their wives and biological children) were identified from the Population Information System of the Population Register Centre. From the original cohort, 133 fishermen, 94 fishermen's wives,

Results

Table 2 summarises the whole blood concentrations of OTCs of the whole study population. TPhT concentration was > LOQ in 37 of the 300 samples (12%), but all the other OTCs were below the LOQ in virtually all samples. In samples with TPhT > LOQ (n = 37), the average concentration was 0.09 ng/ml (2.3  LOQ) and the median concentration was 0.06 ng/ml (1.5  LOQ), respectively. The mean was skewed by the maximum value of 0.56 ng/ml which was more than 3 times higher than the second highest value

Discussion

OTC concentrations in whole blood were generally quite low among the Finnish fishermen, their wives, and other family members. Concentrations were less than the LOQ (0.03–0.72 ng/ml, depending on the compound) for most of the samples. Only TPhT was detected in more than just a few samples (37/300). One aim of this study was to perform an epidemiological investigation of the possible human health effects of OTCs. However, it is for statistical reasons difficult to try to find associations

Acknowledgements

This study was funded by the Academy of Finland (project numbers 107098 and 206950), Yrjö Jahnsson Foundation, and Juho Vainio Foundation. We thank the volunteers and the research staff of the Fishermen study.

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