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PRIO – A tool for Risk Reduction of Chemicals

Criteria for assessing whether the substance is a phase-out substance - PBT/vPvB

In principle, an organic substance is regarded as a PBT/vPvB (Persistent, Bioaccumulative and Toxic/very Persistent and very Bioaccumulative) when test data show that the inherent properties of the substance fulfil the criteria for P, B and T (*16) (see Table 1). However, certain flexibility is required in their application for instance in cases where one criterion is marginally not fulfilled but the others are exceeded considerably. This may include for example substances that do not fulfil the P criteria but bioaccumulate significantly and is measured in plants and animals distant from anthropogenic (*17) sources. In addition, a step-by-step assessment should be made to avoid unnecessary animal testing (*18). The PBT/vPvB criteria of the PRIO tool are in agreement with the criteria found in Annex XIII of Reach.

Table 1. PBT/vPvB criteria according to Section 1 Annex XIII, Reach
Criteria PBT  (Persistent,
Bioaccumulating and Toxic)
(very Persistent and very Bioaccumulating)

The degradation half-life of a chemical substance is:
> 60 days in seawater

> 40 days in freshwater

> 180 days in marine sediment

> 120 days freshwater sediment

>120 days in soil

The degradation half-life of a chemical substance is:
> 60 days in seawater,  fresh or estuarine water

> 180 days in marine, fresh or estuarine water sediment


>180 days in soil


The bioconcentration factor (*20) of a chemical substance in aquatic species:

BCF > 2000  L/kg (wet weight)

 The bioconcentration factor (*20) of a chemical substance in aquatic species:

BCF > 5000  L/kg (wet weight)


-The long-term no-observed effect concentration or the effective concentration at 10% inhibition of a substance, NOEC or EC10  < 0,01 mg/L for marine or fresh water organisms (*21)


-The substance meets the criteria: carcinogenic cat. 1A or 1B, germ cell mutagenic cat. 1A or 1B or toxic for reproduction cat. 1A, 1B or 2 according to Regulation  EC No 1272/2008


-There is other evidence of chronic toxicity: substance meeting the criteria: specific target organ toxicity after repeated exposure STOT RE  cat. 1 or 2 according to Regulation EC No 1272/2008

 Not applicable


Table 2. Assessment information according to Section 3.2 Annex XIII, Reach
Assessment of P or vP properties

(a) Results from simulation testing on degradation in surface water;

(b) Results from simulation testing on degradation in soil;

(c) Results from simulation testing on degradation in sediment;

(d) Other information, such as information from field studies or monitoring studies, provided that its suitability and reliability can be reasonably demonstrated.

 Assessment of B or vB properties

(a) Results from a bioconcentration or bioaccumulation study in aquatic species;

(b) Other information on the bioaccumulation potential, such as:

— Results from a bioaccumulation study in terrestrial species;

— Data from scientific analysis of human body fluids or tissues, such as blood, milk, or fat;

— Detection of elevated levels in biota, in particular in endangered species or in vulnerable populations, compared to levels in their surrounding environment;

— Results from a chronic toxicity study on animals;

— Assessment of the toxicokinetic behaviour of the substance;

(c) Information on the ability of the substance to biomagnify in the food chain, where possible expressed by biomagnification factors or trophic magnification factors.

Assessment of T properties

(a) Results from long-term toxicity testing on invertebrates as set out in Section 9.1.5 of Annex IX, Reach;

(b) Results from long-term toxicity testing on fish as set out in Section 9.1.6 of Annex IX, Reach;

(c) Results from growth inhibition study on aquatic plants as set out in in Section 9.1.2 of Annex VII, Reach;

(d) The substance meeting the criteria for classification as carcinogenic in Category 1A or 1B (assigned hazard phrases: H350 or H350i), germ cell mutagenic in Category 1A or 1B (assigned hazard phrase: H340), toxic for reproduction in Category 1A, 1B and/or 2 (assigned hazard phrases: H360, H360F, H360D, H360FD, H360Fd, H360fD, H361, H361f, H361d or H361fd), specific target organ toxic after repeated dose in Category 1 or 2 (assigned hazard phrase: H372 or H373), according to Regulation EC No 1272/2008;

(e) Results from long-term or reproductive toxicity testing with birds as set out in Section 9.6.1 of Annex X, Reach;

(f) Other information provided that its suitability and reliability can be reasonably demonstrated.


Data required to assess whether the criteria for P/vP are fulfilled

There are standardised test methods that have been developed for instance within the International Organisation for Standardisation, ISO,  and the Organisation for Economic Co-operation and Development, OECD, to measure the degradability of organic substances. The route of degradation which in general is of greatest significance is the biological breakdown that takes place when a substance is subjected to microbial activity for example in surface water, sediment or soil (Table 2). Other degradation mechanisms such as hydrolysis and photolysis have to be taken into account in the assessment when this can be shown to be relevant.

In principle, there are three types of tests on biological degradation:

a) Those that measure ready biodegradation (e.g., OECD TG 301 series);

b) Those that measure inherent biodegradation, also called structurally induced or potential degradability (e.g.  test OECD TG 302B).

c) Tests on simulation biodegradation and transformation in surface water, sediment or soil (e.g., OECD TGs 307, 308 and 309). Simulation tests are adequate to assess degradation kinetics, degradation half-lives, information about mineralisation and degradation products (for example, metabolites).

In order to be able to assess whether a substance is a PBT/vPvB substance, it is required that its degradability has been studied in a simulation test where half-life in water, sediment or soil is determined under environmentally relevant conditions. This half-life is then compared with the PRIO criteria for degradability (P or vP) shown in table 1. There are standardised test methods for simulation tests, for example OECD Guideline No. 307 for the testing of aerobic and anaerobic transformation in soil or No. 308 for testing of aerobic and anaerobic transformation in the aquatic sediment systems.

Data required to assess whether the criteria for B/vB are fulfilled

A substance has a potential to bioaccumulate if it is readily accessible for uptake by organisms, and is only slowly metabolised or excreted. How bioaccumulating a substance is is indicated by the bioaccumulation factor (BAF), which is obtained by relating the concentration in the organism at equilibrium to the concentration in the surrounding environment and in food. BAF is often replaced in practice by the bioconcentration factor (BCF), where the concentration in the organism is only related to the concentration in the surrounding environment, which makes it easier to determine experimentally.

In principle, the assessment of the bioaccumulation in the context of the PBT/vPvB assessment is based on measured bioconcentration factors in aquatic organisms. However, there are bioaccumulation studies with terrestrial organisms obtained from established experimental protocols, such as the OECD TG 317 that can be used for the assessment of B and vB properties. These studies are particularly relevant when for example, exposure from sediment or soil is expected to be more relevant than that of the water column.

Data required to assess whether the criteria for T are fulfilled

The toxicity (T) of a substance should, in principle, be assessed on the basis of chronic or long-term ecotoxicity (*22), data ideally covering the reproductive stages. But data from certain toxicity studies on mammals can also be used.

For the assessment of aquatic toxicity, EC10 values are preferred compared to NOEC values for deriving long-term toxicity to marine or fresh water organisms.

The evidence of CMR (carcinogenic, mutagenic or toxic to reproduction) and chronic toxicity specified in tables 1 and 2 does not only refer to substances that are already classified accordingly (i.e. CLP hazard statements H350, H340, H372, H373, H350i, H360 and H361) but also implies an obligation to check whether the criteria for assigning the respective classifications are fulfilled in accordance with the provisions of Annex I to Reach (Section 1.3 Step 3: Classification and Labelling). If any classification criterion leading to the assignment of the mentioned classifications is met, the substance fulfils the T criterion and there is no need to perform any further aquatic studies for T assessment. If data are available for birds these cannot be directly (numerically) compared with the T criterion (see Section 1.1.3 to Annex XIII, Reach). However, reprotoxicity studies or other chronic data on birds, if they exist, should be used in conjunction with other evidence of toxicity as part of a Weight-of-Evidence determination to conclude on the substance toxicity (a NOEC of ≤ 30 mg/kg food in a long term bird study (*23) should in this context be considered as strong indicator for fulfilling the T criterion).

Due to animal welfare concerns, the general scheme of testing is sequentially first P, B and then T (if there are no specific reasons for deviation from that sequence). Furthermore, vertebrate animal testing should be generally minimised by first testing non-vertebrate species if data from invertebrates are equivalent to vertebrate data in the context of the PBT/vPvB-assessment (Guidance on Information Requirements and Chemical Safety, 2014).



1.  Reach Regulation

2. Guidance on Information Requirements and Chemical Safety Assessment. Chapter R.11: PBT/vPvB assessment. European Chemicals Agency, 2014


*16 T not applicable for vPvB substances

*17 Anthropogenic = influenced, created or caused by man

*18 Information is first gathered on the degradability of the substance (P), then on its potential to bioaccumulate (B) and finally on its toxicity (T).

*20 Determined in accordance with OECD (Organisation for Economic Co-operation and Development) TG 305 that uses the following definition: The bioconcentration factor (BCF) at any time during the uptake phase of this accumulation test is the concentration of test substance in/on the fish or specified tissues thereof (Cf as mg/kg) divided by the concentration of the chemical in the surrounding medium (Cw as mg/L). BCF is expressed in L•kg-1. Please note that corrections for growth and/or a standard lipid content are not accounted for.

*21 The chronic NOEC (NO Effect Concentration) of the substance for marine or freshwater organisms is <0.01 mg/l, i.e. the lowest test concentration at which no toxic effects of the substance have been detected in a long-term test is <0.01 mg/l.

The Effect Concentration EC10, is the concentration that causes the measured effect in 10% of organisms. In a survival experiment, EC10 indicates the concentration where 10% of the test animals would die.

*22 Ecotoxicology = The science of environmental toxins

*23 The lowest test concentration in food at which no toxic effects are seen is lower than 30 mg/kg food. Can be determined in for example studies carried out in accordance with OECD Guidelines No. 205 (Avian Dietary toxicity test) and 206 (Avian Reproduction toxicity test).