The European Medicines Agency (EMA) has released brand new guidance for manufacturers of veterinary products containing substances with the potential to accumulate both inside and outside of an animal.

EMA's 25 July Guidance on the assessment of persistent, bioaccumulate and toxic (PBT) or very persistent and very bioaccumulate (vPvB) substances in veterinary medicine applies is intended to "provide an assessment strategy" for conducting environmental testing of the products.

The substances are extremely hazardous, in particular because of difficulties determining what constitutes a "safe" dose, EU regulators write. In addition, due to their lengthy half-life they can linger in environmental settings, being absorbed by plants, animals and-eventually-humans as well.

"Persistent, bioaccumulative and toxic or very persistent and very bioaccumulative are combinations of substance properties which give substances the potential to accumulate in remote environments which is difficult to reverse as cessation of emission will not immediately result in a reduction in chemical concentration due to long half-life," EMA explained. The compounds are also characterized by their safety risks, which include "secondary poisoning and extreme toxicity," among other safety hazards, the agency explained.

EMA's guidance asks sponsors to assess the product's impact in animals, how it eventually leaves the animal, how it degrades in the environment and what factors influence its degradation, its toxicity and its bioaccumulative properties. Sponsors will also be required to conduct separate assessments for terrestrial animals and aquatic animals, EMA said.

The guidance goes into effect on 1 February 2013.

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EMA - Guidance on the assessment of persistent, bioaccumulative and toxic (PBT) or very persistent and very bioaccumulative (vPvB) substances in veterinary medicine