EALs and why we need them

EALs are thresholds for environmental risks to air quality and set as a concentration in ambient air. The threshold is determined from available scientific evidence and set at levels to ensure that harm to human health and the environment is unlikely.

Air emissions risk assessments associated with applications for environmental permits require permit applicants to use air-dispersion modelling tools to predict likely ground-level concentrations of air pollutants emitted from a prospective process. The aim of the permitting process is to ensure that the predicted process contributions are minimised.

Amine-based Carbon Capture is a relatively new process. Therefore, we need nationally agreed environmental standards for several likely substances emitted to air from the process. The substances given in Table 1, have been identified by industry as being most likely to be used or produced by the Carbon Capture process. They have been prioritised by the Environment Agency in terms of significance and relative toxicological hazard for EAL derivation. The substances include primary, secondary, and tertiary amines and  or their breakdown and transformation products.

Although EALs do not carry a statutory basis, they are a benchmark for harm. They are needed to make sure we have the right level of protection in place for public health from air emissions from the sites which we regulate.

How EALs are used in environmental risk assessments

Our methodology for assessing the impact of emissions to air from the sites we regulate is summarized in our air emissions risk assessment for your environmental permit guidance.

Based on the nature of the release and the type of sensitive receptors nearby, operators need to assess the impact of their emissions to air against the relevant environmental standards:

• Air Quality Standards Regulations 2010 Limit Values
• Air Quality Standards Regulations 2010 Target Values
• UK Air Quality Strategy Objectives
• Critical levels and critical loads for protected conservation areas

If no other standards are available, then the EALs developed by the Environment Agency will apply.

The proposed substances and by-products of amine degradation

The amine-based carbon-capture process, currently being proposed for use with well-established industries, is a designated activity under the Environmental Permitting Regulations 2016.

The Environment Agency has conducted discussions with industry and trade associations, and across government departments, to identify the most common or likely amines and related by-products to be emitted by this industrial process. From these discussions, we identified 6 primary amine solvents and 9 reaction by-products, as listed in Table 1. None of these substances or by-products have existing EALs, as the substances are new to regulation. Based on available toxicological information, we were able to derive EALs for 7 of these substances, shown in Table 2.

Table 1:

How we have derived the new EALs

In deriving the proposed new EALs, we applied the Environment Agency hazard characterisation method summarised in our 2012 consultation document. The approach is described in Appendix 1, which presents a short summary of the EAL derivation for each substance considered, in the form of individual dossiers. You can also find the methodology used in the EAL consultation document 2012.

Note that in the original 2012 consultation we opted to use an excess lifetime cancer risk of 1 in 1 million. However, following a further review of the methodology, and having regard for the derivation of statutory air quality limits, we opted to apply the 1 in 100,000 excess lifetime cancer risk in the derivation of new EALs. We consulted on this change in the first phase of EAL updates in 2021.

For some of the substances considered in this review, in particular the amine derivative products, limited toxicological information is available. This is principally due to their novel nature and lack of prior use. We therefore could not apply our published methodology to the development of EALs for these compounds. In section 3.2 below, we present potential alternative approaches for such situations. 

The new substances

Proposed EALs

Table 2 lists the substances for which new EALs are proposed, together with the derived EALs, for both short-term and long-term averaging times using the Environment Agency hazard characterisation method. “Short-term” means an hourly averaging time (1 hour mean) and “long-term” means an annual averaging time (annual mean) unless stated otherwise.

Depending on the toxicity of a pollutant, both a short and long-term EAL may be appropriate, reflecting adverse effects to health over different exposure periods. However, there is a practical limit on the value of a short-term EAL, if the long-term EAL or statutory value is not to be exceeded. The short-term EAL is therefore not provided for some substances. More details on long and short-term EAL values are provided in Appendix 1.

Table 2: Proposed new substance EALs

Methodologies for the derivation of EALs with minimal data available

There are currently many amines and amine derivatives for which a reliable EAL has not been developed. For those substances where an EAL has not been derived due to a lack of toxicological data we expect operators to derive an appropriate EAL value applying one of the following methodologies:

• “read-across” – this is a formal and accepted toxicological assessment process, applying EAL information available on compounds with similar structures and similar chemistry to the substance being considered 
• there is limited information on many of the N-amine breakdown products – in this case scientific evidence suggests you can use a proxy value, based on the EAL for the “worst-case” (most toxic) representative from a chemical group (for example, compare each nitrosamine with an EAL for N-nitrosodimethylamine (NDMA), for which we have a derived EAL)
• derive a proxy “group” value using the “worst-case” representative from a chemical group (for example, compare all nitrosamines with an EAL for NDMA)

The EAL derivation process to be applied to each individual chemical will depend on the availability of information on similar chemicals or associated chemical groups. The given methods only apply when there is a lack of toxicological data, otherwise the Hazard Characterisation method will apply.

If none of these options are feasible for the derivation of an EAL for an amine compound with insufficient toxicological data, we may ask operators to consider the use of an alternative chemical, for which an EAL can be identified.

We recognise that the use of a proxy value or “read across” approach will not provide the same level of certainty on the toxicity of a given compound as our hazard characterisation method, and therefore the potential will remain for health hazard. We are therefore looking for your comments and views on these proposed alternative approaches.

Future EAL developments

Carbon Capture using amine chemicals is a new industrial process which is likely to be subject to ongoing developments. As such, there may be new alternative substances proposed for usage in the future as primary solvents, also resulting in new by-products. Many of these substances will be likely to lack comprehensive toxicological data to achieve the development of an EAL. In such in cases, the techniques described including, read across or chemical proxy, may need to be applied to achieve a worst case scenario for such substances

The companies applying CCS technology will be expected to use either existing EALs, develop their own EALs using our published methodology, or apply the appropriate proxy value or read-across method, for solvents or by-products that will be emitted.

Financial implications

We appreciate that there may be initial costs to establish the scientific background to the EALs for substances to be used in your process.

We are therefore asking stakeholders to provide any evidence of potential costs for EAL derivation or application, if possible. We want to understand the financial impacts of developing or implementing new EALs on individual industries or facilities.