PAHs in asphalt: 50 and 500 mg/kg thresholds, recycling and waste routes
Values of 50 and 500 mg/kg of dry matter are frequently cited for PAHs in reclaimed asphalt, but they do not have the same meaning in every context. This page explains how to use them without treating technical guidance as a general rule for waste classification.
To obtain an analytical result, see BJL Laboratoires' PAH testing service for asphalt.
Why are there several PAH thresholds?
The management of asphalt depends on the question being considered: acceptance at a facility, hot recycling, cold recycling, recovery as an alternative material or waste classification. A single value cannot therefore be applied to every situation.
The laboratory result must be assessed against the regulation or guidance applicable to the project, the characteristics of the material and the conditions of the intended waste or recovery route.
The threshold of 50 mg/kg of dry matter
Cerema states that 50 mg/kg of dry matter is an important reference value for PAHs in the context of the acceptance of certain road wastes and the recycling of reclaimed asphalt. This value also appears in technical documents relating to alternative materials in the asphalt family.
For hot bituminous mixtures, recent technical guidance includes the absence of asbestos and a concentration of 16 PAHs less than or equal to 50 mg/kg among the environmental conditions to be checked.
What does the value of 500 mg/kg mean?
The value of 500 mg/kg does not mean that a material with a concentration between 50 and 500 mg/kg is automatically permitted in any recycling process. Cerema guidance on the environmental acceptability of alternative materials provides for a value of up to 500 mg/kg in the specific case of cold recycling for the relevant use.
This distinction should be made clear in project documents: 500 mg/kg is a value associated with a defined technical scenario, not a general authorisation for reuse.
Simplified interpretation table
| PAH result | Possible technical interpretation | Precaution |
|---|---|---|
| ≤ 50 mg/kg DM | Value compatible with several recovery or recycling scenarios, subject to the other criteria | Check asbestos, hydrocarbons, intended use, homogeneity and the requirements of the proposed route |
| > 50 to 500 mg/kg DM | May fall within specific scenarios, particularly certain cold recycling applications | Do not extrapolate to hot recycling or any other route |
| > 500 mg/kg DM | The value exceeds the cold recycling scenario cited in the relevant guidance | An appropriate waste management assessment is required; classification cannot be inferred from this value alone |
Why not state “> 500 mg/kg = hazardous waste”?
Because this statement is legally too simplistic. Hazardous waste classification is based on the applicable classification rules and may require consideration of several substances, hazardous properties, concentrations and composition data. A sum of 16 PAHs is not automatically equivalent to the concentration of a single carcinogenic substance.
The purpose of PAH testing is to provide reliable analytical data. Waste classification and selection of the appropriate route must take account of the regulatory framework and the criteria of the intended route.
PAHs and hot recycling
Hot recycling involves reheating reclaimed asphalt. Technical recommendations for this type of recycling impose specific environmental requirements, particularly concerning asbestos and PAH concentrations. The 50 mg/kg threshold is a key value in this context.
PAHs and cold recycling
Cold processes avoid reheating the reclaimed asphalt. Projects and technical guidance have examined their suitability for materials with PAH concentrations between 50 and 500 mg/kg of dry matter. Use of such a solution nevertheless requires compliance with the process's permitted field of application and the project's technical specifications.
PAHs and French inert waste landfill facilities (ISDI)
Acceptance at an inert waste landfill facility depends on the regulatory criteria applicable to admitted waste. Cerema refers to a limit value of 50 mg/kg of dry waste for PAHs in the context it describes. However, the acceptability of a batch is never determined by a single parameter: other analyses, the nature of the waste and the facility's acceptance conditions must also be checked.
PAHs, asbestos and pre-construction characterisation
For road asphalt, asbestos must be addressed alongside chemical characterisation. BJL's currently published conditions require a prior asbestos test report before PAH testing is carried out. If asbestos is confirmed, PAH testing is not performed.
See asbestos and PAH testing of asphalt.
Which information should be provided to the receiving facility?
- identification and origin of the batch;
- description of the materials and relevant layers;
- PAH test report;
- asbestos test result where required;
- other parameters required by the proposed route;
- estimated volume or tonnage and intended destination.
Frequently asked questions
Is 50 mg/kg an absolute hazardous-waste threshold?
No. It is a value used in several acceptance and recycling reference documents. On its own, it does not constitute a general boundary between hazardous and non-hazardous waste.
Can material between 50 and 500 mg/kg be recycled?
Some reference documents provide for cold recycling scenarios within this range. The scope of the guidance and the actual intended route must be checked.
Can a laboratory decide the final destination?
The laboratory provides the analytical results. The waste holder is responsible for the management decision, taking account of the regulatory framework, intended use and acceptance criteria of the receiving facility.
Do you need analysis of the 16 PAHs?
BJL Laboratoires analyses PAHs in waste bituminous asphalt by GC-MS in accordance with NF EN 17503 under its Cofrac accreditation scope.