Elimination of trichloroethylene in asphalt quality control laboratories




General Section



Cleaning agent



Product category

laboratory chemicals


Trichloroethylene is used in quality control laboratories to determine the amount of bitumen in asphalt mixtures. Bitumen is a hazardous substance whose elimination or substitution by a less dangerous chemical is a health and safety priority. The elimination of trichloroethylene from the process is carried out through a small muffle furnace that burns the asphalt mix at the temperature of evaporation for bitumen. This procedure facilitates the calculation of bitumen percentage in the mix based on the weight difference.

Substituted substances


CAS No. 79-01-6 EC No. 201-167-4 Index No. 602-027-00-9

Chemical group

Organochlorid-Verbindung, halogenierte aliphatische Kohlenwasserstoffe

Classification: hazard statements

H350 May cause cancer
H341 Suspected of causing genetic defects
H336 May cause drowsiness or dizziness
H315 Causes skin irritation
H319 Causes serious eye irritation
H412 Harmful to aquatic life with long lasting effects

Other adverse effects

Der Stoff ist: ein 2A Karzinogen (IARC); neurotoxisch Kat. 4 (Vela et al.) wie der Datenbank der nach SUBSPORT-Kriterien gefährlichen Stoffe zu entnehmen ist.

Reason substitution


Other type of alternative

Muffle furnace

Hazard Assessment

» Check the Substance Database according to SUBSPORT Screening Criteria (SDSC)

Description of Substitution

Introduction The case described was reported in quality control laboratories of the regional Industry Department (Castille and Leon) whose activity includes testing construction materials for quality and specific characteristics. Samples are collected at construction sites, roads and tested in physical and chemical laboratories. One of tests consisted in gravimetric analysis of the amount of bitumen is asphalt samples. This type of test requires the use of trichloroethylene. Most tests are carried out in summer (May-October) at a rate of 4 or 5 tests per day. In winter (November-April) the frequency of tests drops to one every two weeks. Workers are exposed for 15 minutes during each test, which usually lasts one hour and is carried out in cabinets with air extraction where workers do not have to be present. Exposure to trichloroethylene occurs during the pouring of bitumen from the distiller to the centrifuge through a sieve and the subsequent washing the walls of sieves with trichloroethylene. The assessments carried out by the preventive service of the Department of Industry in Burgos showed that indicators of exposure to trichloroethylene exceeded threshold values. The preventive service recommended a series of measures as the substitution of trichloroethylene or the modification of the process it was used in. The assessments, the recommended preventive measures, along with the results of medical tests, carried out on different employees showing traces of trichloroethylene by-products, raised concerns and alarm among workers. These concerns led the health and safety rep to contact the regional trade union advisory service. Description of procedure or technology (including pre-/post-processing) Introduced changes did not imply the substitution of trichloroethylene by a different chemical, but the substitution of the testing method. The change consisted in using incineration furnaces to carry out the tests. With this measure trichloroethylene is no longer necessary in the process. A muffle furnace is used to determine the amount of bitumen in asphalt mixes. The muffle furnace burns the asphalt mix at 500-600ºC (evaporation temperature for bitumen). This practice makes possible the calculation of bitumen percentage in the mix based on the weight difference. The emission of volatile organic gases is avoided using an active carbon filter, a simple and reusable method. The method proves quite reliable and it is used by laboratories of the Ministry of Industry (in compliance with the existing regulation NLT 384 /2000). Trichloroethylene was not fully eliminated from the laboratory since it is still used for partial verifications. Way of application: e.g. spraying, dipping, open/closed system etc. Risk management measures (technical, organizational and personal) Risk reduction by alternative: Human health: e.g. more/less safety measures e.g. technical/operational/personal protection measures The use of trichloroethylene and its wastes were eliminated along with the health risks they implied. Risk reduction by alternative: Environment: e.g. waste reduced/increased The use of trichloroethylene and its wastes were eliminated along with the environmental risks they implied.

Case/substitution evaluation

Comments There is no evidence of the muffle furnace clean emissions, only distributor declaration. But it is true that the muffle furnace has an emissions filter. Analytic standards that promote the use of hazardous chemicals should be replaced in the legislation by new and safer standards. This is the case for standards of determination of bitumen in asphalt mixtures. The oldest one implied the use of trichloroethylene, though there is another in use that doesn’t need hazardous chemicals but an oven. Before changing the process, other measures of exposure control were attempted but the best proven measure was to remove the use of the solvent changing the process. This change was so successful that many other analysis laboratories switch to the incineration oven. Advantage or Disadvantage of alternative


Advantage/disadvantage to conventional process

Technical requirements

Reduzierung der Exposition gegenüber gefährlichen Chemikalien.



The measure was implemented in 9 quality control regional facilities (Castille and Leon). The time of technical tests was reduced from 1 hour to 25 minutes.


Trichloroethylene was not fully eliminated from the laboratories since it is still necessary for partial verifications.

Additional comments
As a temporary preventive measure before the installation of furnaces, the Regional Department of Industry provided laboratory employees with individual airline respirators.
These devices did not have the expected effect and proved uncomfortable and difficult to handle for workers. Users complained that the air supply could be cut off if the air tube could coil up. Air pumps did not produce enough pressure. Another inconvenience of this system was the existence of only one set of equipment for all the laboratory staff which added to the lack of adequate training to use it. This preventive measure failed and workers went back to gas masks.

Operational expenses




Enterprise using the alternative

Laboratorios de Control de Calidad de la Consejería de Fomento de Castilla y León

Type of information supplier




Further information


Date, reviewed

February 27, 2020