Bien jurídico protegido

4.4.1.

Whole mixture approach

Step 1 _{– Characterisation of the whole mixture}

In line with the problem formulation and analysis plan, characterise the whole mixture based on what is known about its source, origin, kinetics and composition. If exposure data are not available for the mixture of concern, are there data for a similar mixture that can be used? If the mixture can be reliably quantified by using just one or a few components as marker substances, then list the concentration ratios for these along with an estimate of their variability as components of the whole mixture. By using marker substance(s) in this way, it must be known or assumed that the mixture composition does not change, e.g. by environmental degradation or during processing of food or feed. In all cases, the mixture composition should be stable (within certain boundaries indicated by the concept of ‘sufficiently similar’) for the whole mixture approach to be reliable.

Step 2 _{– Assembling the chemical occurrence (concentration) data}

Assemble chemical occurrence (concentration) data for the mixture of concern which may be estimates from predictive models, or measured data in the relevant samples. If appropriate, consider the analytical method(s) used and assess the extent to which the method allows quantification of the whole mixture or marker substances described at step 1. When specific occurrence data are not available, consider using usage levels or data from the whole mixture with similar sources, use patterns, environmental fate or toxicokinetics or physicochemical properties.

Step 3 – Combining occurrence data and consumption data

Combine occurrence data with the consumption data to estimate exposure using the same tools and assumptions as are used for a single chemical substance. This step is generally not required in ecological risk assessment as consumption data are usually not available and environmental concentration is taken as a metric for exposure.

Step 4 _{– Report exposure data}

Summarise the exposure results, associated assumptions, uncertainties and consequences for risk characterisation. In case of uncertainty because of limitations in the data or the analytical method used, provide comparative data and/or a rationale for consideration by (eco)toxicologists, who may wish to propose an additional assessment factor in the risk characterisation (especially for lower tiers, as a method to ascertain the characteristic of lower-tier conservatism).

If any of the individual chemical components of the whole mixture is subject to an existing risk assessment and/or legal restriction as noted in the problem formulation, it may also be appropriate to estimate exposure to that chemical substance(s) from all sources and describe the contribution coming from the whole mixture under assessment.

4.4.2.

Component-based approach

Figure6summarises the steps of exposure assessment using the component-based approach. Step 1 – Components of the assessment group

According to the problem formulation, analysis plan and input from (eco)toxicologists, list the chemicals in the assessment group(s) depending on the criteria used for grouping (exposure-based or hazard-based, etc., with the option of treating all chemicals as if in one group as a lowest-tier grouping method). Consult (eco)toxicologists to obtain information on relative potencies of the individual components of the assessment group (see guidance in Section 5), if available, and to understand the timeframe that is required for those chemicals which could potentially elicit combined toxicity.

Step 2 _{– Assembling chemical occurrence data}

Assemble occurrence data considering plausibility of the individual components to co-occur, taking into account advice from (eco)toxicologists on the relevant timescale (see Step 1). When estimating acute toxicity use only data sources that provide information on the co-occurrence of components of the assessment group within a narrow timescale (e.g. a single eating occasion or a single environmental release). If occurrence data are not available for all components of the assessment group in all of the samples analysed, evaluate ratios and correlations between components with the available dataset and decide if the missing data can be imputed.

Consider the precision and accuracy of the analytical method(s) used for each component and the consequence of the detection limits for the exposure estimates. When necessary, apply appropriate corrections, assumptions or methods for left-censored data.

If occurrence data for individual components are available and relative potencies were provided by (eco)toxicologists (e.g. RPFs, see Step 1) potency-adjusted concentrations can be calculated.

Step 3 _{– Combine occurrence and consumption data}

Combine occurrence data for all components with consumption data, taking into account advice from (eco)toxicologists on the relevant timescale (see Step 1), and estimate exposure using suitable tools depending on data availability and the selected approach for risk characterisation. When the toxicological potencies of the individual components are sufficiently understood and reliable factors have been identified by toxicologists (e.g. RPFs, see Step 1) calculate potency-adjusted exposure.

This step is generally not required in ecological risk assessments as consumption data are usually not available and environmental concentrations are taken as proxies for exposure.

Step 4 _{– Report exposure data}

Summarise the exposure results, associated assumptions, uncertainties and consequences for risk characterisation. Report the aggregated exposure estimates for the whole assessment group indicating the contribution of each individual component and each source, as this can help risk managers and guide the collection of new data and/or providing a mitigation plan.

If any of the individual chemical components of the assessment group is subject to an existing risk assessment and/or legal restriction as noted in the problem formulation, it may also be appropriate to estimate exposure to that chemical substance(s) from all sources and describe the contribution coming from the group of multiple chemicals under assessment.