What is bitumen?
Bitumen is a virtually non-volatile, adhesive and waterproofing material derived from the distillation of crude oil. It is very viscous or almost solid at ambient temperatures.
Is there a difference between bitumen and coal tar?
Absolutely. Coal tar was used for road building and water proofing before being replaced by bitumen after the Second World War. Although similar in appearance, the chemical composition of coal tar is quite different from bitumen.
Bitumen is distilled from crude oil, while coal tar is derived from processing (pyrolisis) of coal at very high temperatures. The different raw material and manufacturing processes are the reasons for the large differences in the chemical composition of the two products as well as the nature of hazard that coal tar presents to the user.
Consequently coal tars are classified as carcinogenic, whereas bitumens are not.
Are there any hazards to the general public from bitumen?
Bitumens in service on for example roads, roofs or pavements are virtually solid and do not present any known health or environmental hazard.
Are there any hazards to workers from the application and use of bitumen?
Bitumen is normally manufactured, stored, transported and handled hot. Hence the most significant hazard is the potential to cause severe burns.
Hot bitumens give off fumes. These can cause respiratory tract or eye irritation. Much scientific research has been carried out to establish that, apart from this irritation, there is no evidence that bitumens are hazardous to worker health. Good temperature control and work practices can prevent or minimise worker exposure to fumes from bitumen.
What research has been conducted into the health effects of bitumen fumes on workers and by whom?
In 2001 IARC (the International Agency for Research on Cancer - a division of the World Health Organisation) published a report of a study that reviewed causes of death (with a focus on cancer) within a group of approximately 80 000 construction workers, including approximately 30 000 asphalt workers. The study reviewed the mortality rates of bitumen workers in seven European countries (Denmark, Finland, France, Germany, the Netherlands, Norway, Sweden) and Israel. The study team looked at a large number of causes of death. These included accidents, suicide, diseases of the circulatory, respiratory or digestive system and a very large number of different types of cancers including lung and respiratory tracts, digestive system, skin cancer and leukaemia.
Overall it was noted that the occurrence of mortality was below what the scientists would expect for the general population, but IARC did detect a small increase in the incidence of lung cancer amongst workers exposed to bitumen fumes.
Since no cause could be associated with the observed slight increase in lung cancer, IARC carried out a follow-up study to investigate the possible causes of the increase. This study was completed in 2009, see below.
Ref: American Journal of Industrial Medicine, Volume 43/N° 1/ January 2003
Does exposure to bitumen fumes lead to lung cancer in humans?
No. The presence of very low concentrations of Polycyclic Aromatic Hydrocarbons (PAH's) in bitumen has raised concerns regarding the potential for health effects in workers exposed to bitumen or to bitumen fumes. Because some PAHs are carcinogenic, a possible cancer risk has been the primary concern.
IARC (the International Agency for Research on Cancer - a division of the World Health Organisation) has completed the second phase of a major epidemiology study to determine whether there is an increased risk of lung cancer to asphalt workers. This study could find no link between exposure to bitumen fumes and lung cancer. The factors identified as the likely contributor to the slightly elevated incidence of cancer were tobacco smoking and previous exposure to coal tar.
These findings support the results of other studies for example the Fraunhofer study (2006).
More details
How can worker exposure to fumes from bitumen be minimised?
Worker exposure can be minimised by the use of good working practices, such as:
- Keeping the temperature of the material as low as practically possible;
- Working in well ventilated conditions (including simple practices e.g. standing upwind of the source of fumes);
- Job rotation around the worksite;
- Use of personal protective equipment, especially in confined spaces.
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