## 1 Introduction  
There are a large number of chemicals commercially available, with over 85,000 listed in the Chemical Substance Inventory of the US EPA [1]. As only about 1000 chemicals have authoritative occupational exposure limits (OELs) referenced in legislation, assessing the hazard and risk posed by the majority of chemicals used in the workplace is challenging for employers and employees alike [2, 3]. Exposure to chemicals and hazardous substances at work also presents a significant disease burden within Canada and elsewhere [4, 5]. As such, in Canada, workplace chemicals are managed through the Workplace HazardousMaterials Information System (WHMIS) which has adopted the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) and is embedded in federal and provincial/territorial legislation. The federal legislation (Hazardous Products Act and its Regulations) addresses the importation and sale of chemicals, while provincial/territorial occupational health and safety OHS legislation addresses the use of chemicals within workplaces. The key elements of WHMIS are classification of chemicals into hazard groups and classes; labelling requirements for packaging; supplier-provided safety data sheets (SDSs) that describe hazard and precautionary information for each chemical and are to be readily available to workers; and WHMIS education and training programs for workers so that they understand the hazards of the chemicals they are using and how to handle these safely [6]. Even though employers have an obligation to assess and manage the health and safety risks arising from hazardous chemicals in the workplace, small- and medium-sized workplaces (SMWs) find this particularly difficult [7; 8]. This is because SMWs often lack the knowledge and resources (human and economic) required to identify and assess chemical risks and to implement preventive measures against hazardous substances [9; 10].  
SMWs lack simple, validated and appropriate tools to evaluate chemical risks [9; 10; 11; 12]. As such, a key ongoing recommendation from the European Agency for Safety and Health at Work has been the need for easy-to-use tools to identify chemical hazards and assess the risks posed by exposure to these chemical agents [3; 7], along with tools that provide guidance on control measures, particularly'substitution' [13]. A number of chemical risk assessment tools have been developed over the years, but despite their availability, basic risk assessment of chemical exposures still represents a major difficulty for SMWs [13].  
To address the ongoing need to support SMWs in undertaking chemical risk assessments, the goal of this project was to develop an easy-to-use electronic tool (called CHAP-Risk, with CHAP = Chemical Hazard Assessment and Prioritization) to help SMWs more easily recognize the hazardous nature of their chemicals and to perform a simple risk assessment of the chemicals based on how the chemicals are used in their workplace. The overall design of CHAP-Risk was guided by the three components of the sound management of chemicals in the workplace as recommended by the ILO, i.e., identification of chemicals and classifications of hazards, determination of potential workplace exposures and risk assessment, and identification and implementation of control measures [14].