EFSA opinion on okadaic acid marine biotoxins

EFSA was asked by the European Commission (EC) to assess the current European Union (EU) limits for various marine biotoxins in relation to human health and the methods of analysis used to detect these toxins. This is the first in a series of nine opinions on the various biotoxins and it addresses one group , okadaic acid (OA) and related toxins that together form the group of OA-toxins.

EFSA’s CONTAM Panel[1] has assessed the available data and identified for OA-group toxins a level at which most consumers, even those eating a large portion of shellfish, would be unlikely to get shellfish poisoning. The Panel has also highlighted shortcomings in current animal testing methods and made recommendations for future work on alternative methods.

OA-group toxins are usually produced by a type of plankton in the sea. These toxins can contaminate shellfish, notably bivalve molluscs such as oysters, mussels, scallops, and clams. Contaminated shellfish may cause diarrhetic shellfish poisoning (DSP). DSP can also be caused by other toxins, not only OA-toxins.

OA-group toxins levels are monitored in Europe. Food businesses must ensure that bivalve molluscs placed on the market for human consumption do not exceed the current European regulatory limit of 160 µg[2] of OA equivalents / kilogram shellfish meat.

By looking at the available human and other toxicological data, EFSA’s CONTAM Panel decided to establish an acute reference dose (ARfD) for OA-group toxins, given their acute toxicity [3]. The ARfD was identified by studying available evidence on the lowest levels at which the toxins led to human illness[4] and by applying an uncertainty factor [5]. This resulted in an ARfD of 0.3 µg OA equivalents / kilogram bodyweight.

The Panel noted that the dietary exposure of a 60 kg adult consuming a large[6] portion of shellfish meat (400g) contaminated at the current EU regulatory limit would exceed the ARfD by approximately 3-fold and is close to the lowest level at which the toxins could lead to illness. This intake would be expected to have an effect on susceptible consumers. To avoid exceeding the Panel’s ARfD a 400g portion of shellfish would need to contain no more than 45 µg OA equivalent /kg shellfish meat. This work will help inform the judgement of risk managers on acceptable levels of exposure to OA-group toxins to help protect people against the risk of food poisoning.

The Panel also considered the current methods of analysis. Tests involving mice and rats are currently the officially prescribed reference methods in the EU for identifying OA-group toxins. The Panel concluded that both methods have shortcomings such as limited capability to detect OA-group toxins at the current EU regulatory limit or below that. Alternative biomolecular and chemical methods have the greatest potential to replace the animal tests and to detect OA-group toxins below the current EU regulatory limit. However, according to EU legislation alternative methods have to be validated following internationally recognised protocols. The Panel noted that validation by interlaboratory trials should be a long-term objective.

The Panel made a series of recommendations, for example to improve Member States (MS) reporting systems and sampling procedures; and to strengthen databases held on shellfish consumption. The need for further toxicological data was highlighted, as were recommendations on methods of analysis. The opinion and recommendations will help inform further thinking about methods of analysis at European level by the EC and MS.

[1] The Scientific Panel on Contaminants in the Food Chain
[2] µg: a micrograms, one millionth of a part of a gram
[3] An ARfD is the amount of a substance that can be consumed over a short period of time without any appreciable health risk for consumers.
[4] The lowest observed adverse effect level (LOAEL)
[5] This calculation extrapolates to a level at which effects would not be seen, the no observed adverse effect level (NOAEL)
[6] A main course where all the meat is shellfish, eg a large bowl of mussels