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Interim report of the HELCOM CORESET project

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4.26. Acetylcholinesterase (AChE)<br />

General information<br />

General properties<br />

The analysis <strong>of</strong> acetylcholinesterase (AChE; EC 3.1.1.7) activity and its inhibition in marine organisms has<br />

been shown to be a highly suitable method for assessing exposure to neurotoxic contaminants in aquatic<br />

environments. AChE activity method is applicable to a wide range <strong>of</strong> species and has <strong>the</strong> advantage <strong>of</strong><br />

detecting and quantifying exposure to neurotoxic substances without a detailed knowledge <strong>of</strong> <strong>the</strong> contaminants<br />

present. AChE activity is a typical biomarker that can be used in in vitro bioassays and fi eld applications.<br />

Main impacts on <strong>the</strong> environment and human health<br />

AChE has traditionally been used as a specifi c biomarker <strong>of</strong> exposure to organophosphate and carbamate<br />

pesticides. More recently, its responsiveness has been demonstrated to various o<strong>the</strong>r groups <strong>of</strong> chemicals<br />

present in <strong>the</strong> marine environment including heavy metals, detergents and hydrocarbons. Its usefulness as<br />

a general indicator <strong>of</strong> pollution stress in mussels from <strong>the</strong> Baltic Sea has been shown within <strong>the</strong> EU-BEEP<br />

<strong>project</strong>. AChE inhibition mostly agreed well with <strong>the</strong> studied pollution gradients, especially in mussels. Seasonal<br />

differences in activity were notable in fl ounder, eelpout and mussels, possibly resulting from variations<br />

in <strong>the</strong> occurrence <strong>of</strong> affecting substances (e.g., pesticides from river input or run-<strong>of</strong>f from agricultural<br />

sources) during <strong>the</strong> year. Additional fi eld studies and laboratory experiments showed that AChE in Baltic<br />

mussels is infl uenced by temperature and salinity, while also salinity has an effect on <strong>the</strong> uptake (and <strong>the</strong>refore<br />

on toxicity) <strong>of</strong> substances (Lehtonen et al. 2006).<br />

Status <strong>of</strong> a compound on international priority lists and o<strong>the</strong>r policy relevance<br />

OSPAR pre-CEMP, MED POL Phase IV (2º Tier).<br />

ICES SGIMC has recommended AChE in molluscs as biomarker to be included into <strong>the</strong> OSPAR Coordinated<br />

Environmental Monitoring Programme (pre-CEMP).<br />

AChE has been adopted by UNEP as part <strong>of</strong> <strong>the</strong> second tier <strong>of</strong> techniques for assessing harmful impact in<br />

<strong>the</strong> Mediterranean Pollution programme (MEDPOL Phase IV).<br />

GES boundaries and matrix<br />

The existence <strong>of</strong> extremely low thresholds for induction <strong>of</strong> inhibitory effects on AChE suggests that detection<br />

is possible after exposure to low concentrations <strong>of</strong> insecticides (0.1 to 1 μgl-1; ICES 2010).<br />

Standardisation <strong>of</strong> <strong>the</strong> sampling strategy and regular intercalibration exercises on specifi c organisms are still<br />

necessary before using AChE in routine pollution monitoring.<br />

No formal quality assurance programmes are currently run within <strong>the</strong> BEQUALM programme but one major<br />

intercalibration exercise was carried out during <strong>the</strong> BEEP <strong>project</strong>.<br />

Baseline levels <strong>of</strong> AChE in different marine species have been estimated from results derived from in <strong>the</strong><br />

Atlantic Ocean, <strong>the</strong> Mediterranean and <strong>the</strong> Baltic Sea (Table 4.6; ICES 2010) and ongoing studies within<br />

Bonus+ BEAST.<br />

Generally it has been accepted that 20% reduction in AChE activity in fi sh and invertebrates indicates<br />

exposure to neurotoxic compounds. Depression in AChE activity more than 20% up to 50% indicates sublethal<br />

impact. In <strong>the</strong> fi eld, several species have baseline AChE activities within <strong>the</strong> same order <strong>of</strong> magnitude<br />

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