The MiXie software: study of toxicological risks related with a mixture of chemical substances

MiXie is a web based software created by the University of Montreal and the Institut de recherche Robert-Sauvé en Santé et en sécurité du Travail (IRSST, 2014). It is aimed at helping the industrial hygienist for assessing the risks associated with the exposure to a mixture of airborne chemical substances at the workplace. The toxicological effects of more than 600 substances have been listed and categorized into 32 toxicological classes, such as cancer or liver disorder. For example, the toluene can provoke central nervous system disorders, eye disorders, upper respiratory tract irritations and embryonic or fetal disorders. With regards to a work situation, the chemical substances which contribute in the same toxicological classes are grouped into combinations. The mixture exposure index Rm (airborne concentration value divided by limit value) is calculated for the substances included in the combination. On the basis of Rm, the industrial hygienist gets an insight of the risks related with the mixture of substances.
This algorithm has been applied to the mixtures from the COLCHIC database (Vincent & Jeandel, 2001). This database contains more than 900.000 records of air sample analysis realized in French enterprises. More than 700 different substances are identified and more than 48.000 work situations are present. A work situation is a set of measurements of one or more substances, realized in the same enterprise, for the same task and during the same month. In this study, the most recent data (years 2003-2012) from COLCHIC are analyzed by MiXie algorithm. For each work situation, the toxicological effects are identified and the Rm is computed and compared to a threshold of 1, meaning that the risk is high.
On the considered period, 13.452 work situations are present into COLCHIC, only 5.339 are useable bay MiXie because of chemical substances form MiXie differ from chemical substances from COLCHIC. Among these 5.339 work situations, 1.042 presents one or more toxicological class with a high risk. 18% of these risk situations do not present any measurement value superior to the limit value: the risk is directly due to the mixture. Moreover, the situations are sorted by number of toxicological classes with high risk in order to identify situations patterns. It appears that the activity sectors related with waste treatment and composite materials are related with large number of high risk toxicological classes.
The relevance of considering the exposure and the risks related with a mixture of airborne chemical substances was expected but not demonstrated. In this study, the use of Mixie algorithm on historic COLCHIC data empirically shows the need for taking mixture into account. Moreover the examination of work situations allows highlighting where the most important risks are and thus where the prevention messages should be reinforced.