1,3-Butadiene: update of current knowledge and assessment of exposure in the working environment

Outline of reasons and objectives
Setting occupational exposure limit values for chemical pollutants is an essential tool in preventing chemical risks. Butadiene, the third most used Carcinogenic-Mutagenic-Reprotoxic (CMR) substance in France, is one of the substances for which the ANSES (French Agency for Food, Environmental and Occupational Health & Safety) has conducted expertise and appraisal work in order to propose a limit value. At national level in France, the data on exposure to butadiene lacks documentation and cannot be extended to all of the players potentially involved in using and handling butadiene. To mitigate this lack of information and to contribute to knowledge on this substance, this industry study was conducted with the aims of:
identifying the sectors of activity in which butadiene is involved;
taking an inventory of the modes of use of the substance; and
assessing the prevention practices implemented on the sites, in particular by appraising the exposure profiles relative to the limit value that could be proposed.

Approach
Three main steps were conducted to collect this information:
identifying the various players coming into contact with the substance while incorporating the various steps of the life cycle of butadiene; this approach consisted in compiling the available data, in interrogating the exposure databanks and in talking to the experts from the industrial fields and from occupational safety and health;
collecting the information on how butadiene is used and on the prevention measures put in place on the sites; this step results from interventions in companies and from a survey by email; and
using and interpreting the collected data.

Main results
Two types of potentially involved player appear: the main sectors of activity (production and use of butadiene, in particular in manufacturing polymers) and the secondary sectors (handling polymers manufactured with butadiene, use/handling of Liquefied Petroleum Gas (LPG) and use of butadiene for purposes other than polymer production).
After the interventions and the survey, it transpired that 305 sites from among the respondents were potentially involved in using or in working in the presence of butadiene, representing over 4 million metric tons of used/handled material. 12% of those sites implement chemical risk assessment approaches, and less than 50% of the ones that do such assessments record the results in the single document. After statistical adjustment of the results, it is estimated that 1,500 sites in France are concerned by the butadiene risk, representing 32,000 potentially exposed employees.

Discussion
This study emphasises that the risk factors related to use/handling of butadiene are taken into account to contrasting extents that depend on the players (primary and secondary sectors) and that are correlated with the potential levels of exposure of the employees:
less than 10% of the sites belonging to the main sectors present the exposure levels that are, a priori, the highest; those sites account for 30% of the employees exposed, and all of them implement chemical risk assessment approaches;
more than 90% of the sites in the secondary sectors have the levels of exposure that are, a priori, the lowest; those sites account for over 70% of the employees exposed, and 4% of them conduct chemical risk assessment approaches.
This study also bears witness to the importance of the form and of the content of the prevention messages to be put across, it being necessary for such messages to be appropriate to the activities of the players (main and secondary ones) and to their needs. Prospects such as conducting a national campaign of measurements of butadiene and developing new sampling/analysis methods should be considered in order to enrich the butadiene exposure profiles.