The construction industry is dominated by small- and medium-sized enterprises (SMEs) who lack full time safety and health staff. In the US and NL for instance, about 80% of the construction companies are SMEs with fewer than 10 employees [12,13] and in Great Britain (GB) they account for 73% of the industry's fatalities [14]. As is true with general industry, the accident and occupational disease rates are often twice as high among SMEs, compared with large enterprises [15]. The construction industry is highly competitive and work is typically awarded to the lowest bidder. Construction worksites are by their nature temporary, and typically involve multiple contractors and subcontractors each present for only a portion of the project. These and other attributes contribute to hazards and complicate national safety and health enforcement efforts. The end result is that poor occupational safety, health and hygiene (OSHH) protection and enforcement shift disproportionate human and economic costs to the construction worker, their families and communities [16]. Globally, construction employers commonly utilize immigrant workers. These employees typically speak non-native languages, may have low literacy skills resulting in many languages being spoken on a worksite, and may have general communication issues between employers and employees that go beyond language and literacy [17]. Small employers often do the same job as their employees and are without time to search for prevention, risk assessment, and control information. As construction industry management is often output-oriented, as long as quality, time, and cost criteria are met, little thought is given to ensure protective measures are used and followed. Often employees decide how the job is done. Therefore, 'solutions initiatives' are best aimed at employee and employer [16].

It is unrealistic to expect most SME employers to distinguish among separate OSHH fields. Small construction employers have been shown to view OSHH risks as the responsibility of employees instead of something integrated into their company management systems [4]. Few understand accident prevention or detailed hazard awareness, often with controls unavailable or opting for the cheapest control measure [18,19]. Regulatory enforcement of control measure use is weakest with construction SMEs, and nearly non-existent in most countries for accident and MSD prevention [16,19,20]. Effective enforcement as a means of promoting control solutions use requires intense and sustained efforts that is unlikely to occur given limited resources and expertise. Consequently, more effective approaches will involve better mechanisms for reaching SMEs with holistic solutions to industry challenges, rather than a reliance on enforcement and punitive strategies.

Construction hazards have received considerable attention over the last two decades. Researchers internationally have examined hazards, consequences, and costs and developed numerous interventions and tailored controls [6,11,16,19,21,22]. Construction has also grown as a specialty practice area for OSHH professionals. Although injury and fatality rates have become relatively flat over the last two decades for larger firms, injury rates remain high for SME construction firms. Numerous research needs remain and transfer of research from peer-reviewed journals to construction practice, and between countries, has been slow. There is increasing recognition that implementation of evidence-based public health interventions of all types is hampered by the near total absence of systems and infrastructure for marketing and distributing information to end users [23]. Many countries are getting more involved with transfer, ranging from developing "Research to Practice" programs in the US, to improved packaging of technical guidance in GB, to industry in NL. Increasingly, research programs are attempting to develop more comprehensive approaches to transfer research findings to practice.

Respirable quartz dust (silica) provides an excellent example of these gaps and challenges. Silicosis in construction has been an issue for decades and preventative methods are well known to OSHH professionals [24]. Awareness of silica hazards among SME contractors has lagged behind awareness of injury hazards. Silica as a recognized hazard in NL began getting attention in the early 1990s [25]. Despite several initiatives taken to reduce silica exposure in construction, inconsistent application of control measures has led to early signs of silicosis in newer construction workers [26,27]. Since then, the Dutch government and the sector jointly invested approximately 16 million euro for developing and implementing measures to reduce silica exposure [28]. In 2007, however, Dutch Labor Inspectorate inspections showed only 30% of the construction companies take measures against dust at high exposure levels [22], a figure which is exactly the same as it was before this investment [26]. In NL, therefore, one can conclude that the investment has not led to implementation of more control measures, so far.

Increasingly important is focusing on preventive and control methods for common work-related hazards [29]. In shifting the focus to 'prevention', it is vital to transfer information comprehensibly, so workers and employers can understand the hazards and risks, how they apply, and how to use the control measures properly [30,31]. To significantly affect injury and illness rates in the construction industry, a consistent and coordinated message must present a simplified method for ensuring risk assessment, risk prioritization, and workable solutions readily available to workers. Given the similarity of construction hazards and control implementation problems across different countries, a strong case can be made for increased global collaboration and better utilization of limited resources.

We describe the least complex approach as 'universal precautions' because it involves using a basic control in every situation involving a particular hazard. The term is commonly used in occupational health to describe the use of hand and face personal protective equipment (PPE) in health care with all patients to avoid contacting bloodborne pathogens and other bodily fluids. An example of a common universal precaution in construction is the use of hardhats and steel-toed shoes by all site workers. These precautions are universal because they are implemented on every worksite regardless of work scope or tasks performed. Universal precautions also include other types of measures higher in the control hierarchy, such as machinery guarding, requirements for ladders, prohibited activities, safe traffic routes, equipment maintenance, residual current devices, and requirements for extracted or emission-suppressed tools. The approach is widely used for safety hazards, both in guidance and regulations.

The US Occupational Safety and Health Administration (OSHA) appear to concur with universal precaution terminology in a "Quick Card" for construction PPE. The single-page Quick Card also covers very basic information on selection, use, and care for prescribed PPE. Construction universal precautions listed are PPE for the: eye, face, foot, hand, head, and hearing protection. Simple guidance from the GB Health and Safety Executive (HSE) expands on this model: "The absolutely essential health and safety toolkit for the smaller construction contractor". This sets out checklists for many of construction hazards, presenting short, simplified, and standardized controls by industry sector.

A universal precautions model represents a simple binary approach: when or wherever the hazard is present the same control approach is used. The simplicity of this approach is a major strength. It is the easiest to communicate to employers and employees. It serves to create a baseline of holistic construction rules that every employee should be trained on and aware of, before entering a construction site. It works well with easily recognized hazards. Disadvantages of universal precautions may arise when this approach is applied to complex hazards because the approach may result in overprotection and perceived burden in some cases and under-protection in others. While this may not be a significant issue for low cost controls such as hard hats, it is more challenging for more costly controls. While universal precaution approaches should always be considered, they may not be suitable for complex hazards ranging in severity based on site-specific factors.

CB is a medium-complexity approach to evaluation and control of hazards. It involves a structured evaluation of tasks, operations, or work settings. It does not involve quantitative exposure assessment, utilizing operation-specific objective information such as quantities of materials used, exposure properties of substances handled, and nature or duration of tasks. CB originated in the pharmaceutical industry for use as an alternative approach for controlling chemical exposures in the absence of occupational exposure limits and from European systems linking exposure to control systems [31]. It relies on decision rules derived from prior quantitative studies of various exposure factors. CB allows users to make meaningful inferences about likely exposures and controls needed to reduce them. Thus it represents qualitative risk assessment and risk management approaches. CB groups workplace hazards into four or five stratified risk 'bands', identifying commensurate control measures. Such risk assessment is necessarily generic, so the bands used should apply precautionary assumptions. While OSHH professionals have viewed CB and simplification as a lesser option to quantitative methods, recent application of CB to nanomaterial exposure control has altered that view significantly [31,34,35]. An important application for CB is where uncertainty is high, such as when exposure limits do not exist but substances can be reliably grouped based on similarity to better studied substances. Or when tasks vary in nature, setting and duration, as is often the case in the construction industry.

Development and validation of CB has accelerated internationally, resulting in occupational risk management models being built upon CB principles [31,36,37]. Most CB 'toolkits' are national initiatives to control SME employees' exposures to chemicals, especially substances without exposure limits. CB strategies have also expanded recently to ergonomics and injury prevention [31]. CB publications have helped increase control use by providing an evidence-based alternative to quantitative exposure assessment. CB efforts have helped emphasize the need to increase control implementation for SMEs. Although researchers and OSHH practitioners have long worked hard to communicate solutions, even through the late 1990s literature was inconsistent in reporting intervention effectiveness and good practice [38].

Increasing global need has expanded the popular definition of CB as a risk assessment-banding-control model to include "task-to-control" approaches focused on controls needed for specific tasks. Since 2000, national and international collaborations facilitated through the World Health Organization (WHO) and the International Labor Organization (ILO) have been a major driver. These global organizations have provided significant impetus to CB, backing an array of initiatives to prevent work-related injury and illness wherever OSHH expertise is lacking [30]. US NIOSH highlights construction sector attributes, such as pre-job planning for preventing and managing construction hazards, suggesting that CB approaches could fit well [31]. Researchers commonly use construction task-based exposure models to evaluate and understand the episodic, highly variable exposures associated with construction activities, and develop work practice and control solutions. While construction is a definitive multidisciplinary activity, such research and solutions tend to not be easily accessible for the worker. OSHH expertise available to SMEs is lacking: meanwhile, regulatory standards and guidance call specific practices and control measures for defined tasks. To date, no set of tools has been developed for construction contractors; although many "task-based" control measures exist and align with CB concepts. To address variability needs, the CB model divides into two subcategories: task-to-control (T2C) and risk assessment.

The T2C approach organizes control recommendations by task, rather than by level of risk. PPE may also be recommended for those controls not sufficiently reducing exposures. Standardizing tasks afford multidisciplinary perspectives across the OSHH professions. Although standardizing construction industry tasks is a substantial challenge, there are both common tasks and task components that can meet this expectation. In GB, the Control of Substances Hazardous to Health (COSHH) Regulations were not well understood by SME employers who lacked OSHH expertise, prompting requests for simplified approaches to compliance. This led to 'COSHH essentials', a CB toolkit combining hazards of chemicals or products, and potential exposure, to identify appropriate control measures via 'Control Guidance Sheets' (CGS). Strengths of the T2C model include addressing risks, for a variety of hazards, by identifying established standardized control solutions for individual tasks. Limitations include potential for excessive or insufficient control that standard approaches present. This is particularly true for construction tasks with substantial variability and a heavy reliance on PPE rather than the well-established hierarchy of controls.

A limited selection of CB toolkits are available that could help the construction sector. The Risk-to-Control model utilizes a Risk Level (RL) matrix approach, utilizing qualitative risk assessment techniques. Parameters for defined tasks determine the RL. This RL approach assists in ensuring control measures are sufficient to control risks. Strengths of this approach are that controls are stratified commensurate to risk, it follows the hierarchy of control, and it promotes the potential for substitution. The strengths and limitations of CB toolkits, as well as the different types of toolkits from various countries, have been well described [31,36,61].

While 'COSHH essentials' could be utilized as a construction RL approach, its applications are limited because the focus is the fixed workplace. 'COSHH essentials' and the comparable Einfaches Massnahmenkonzept Gefahrstoffe (EMKG) toolkit from Bundesanstalt für Arbeitsschutz und Arbeitsmedizin (BAuA) have been evaluated for adequacy of its recommended control for tasks in SMEs requiring solvent-based components and may also be useful for tasks using large quantities of dry materials, such as construction-related powders and dusts [62-64]. Previous evaluation of the 'COSHH essentials' determined strengths of the toolkit for solid substances such as powder and dusts, however there was a potential for exposure underestimation for small quantities of volatile liquids over large surfaces such as glue in a carpenter shop [62]. Recent evaluation of CB against quantitative data sets with solvents and in carpentry-related production show excellent control of exposures below established limits, however a probabilistic model shows CB does not guarantee compliance except for volatile liquids in closed systems and solids with local exhaust ventilation [63]. In addition, CB limitations in construction could include some many hot processes, gases, and spray applications.

The premier RL approach is 'Stoffenmanager Construction', developed as a pilot to control silica dust exposures for plasterers and tilers [65]. Its concept is that risk assessment and advice should be based on quantitative exposure assessments wherever possible and modeled calculation should only be applied when there were no exposure data. Stoffenmanager for control of exposure to silica dust has three risk assessment routes, depending on the data available. The program determines which route to use:

Route 1 uses quantitative exposure data as well as quantitative data about the effectiveness of control measures. It calculates an exposure factor (EF), a reduction factor (RF) and a remaining exposure factor for each task

The expert model approach represents the traditional approach whereby an employer utilizes an OSHH professional to evaluate site specific hazards, recommend controls, and manage a safety and health program or system to insure effective implementation. This conventional approach is commonly seen as the 'gold standard'. Strengths are obvious as expert derived prescriptive solutions effectively follow the established hierarchy of controls and are the standard of OSHH professions. This approach provides the highest confidence that hazards are properly evaluated and controlled, especially for highly complex hazards. OSHH professionals are expected to know about research describing exposures and control effectiveness from professional journals and learning about developments via professional conferences. OSHH professional employment by construction employers also helps to institutionalize and integrate OSHH at the organization level and into other key business areas such as design and procurement. The major limitation of this approach is that most SMEs do not employ OSHH professionals as they are expensive and in many parts of the world are rare or non-existent. OSHH professionals also tend to specialize, thus requiring multiple consultants. While the expert-driven model will always be critical for large employers and complex hazards, limitations of this approach have fuelled interest by governments and international organizations in developing CB approaches that provide meaningful alternatives for SMEs.

Over the last few years CB has expanded into wider OSHH fields, beyond substances and chemical products. These are termed 'toolkits': a 'toolbox' may contain several toolkits [31]. Toolkits use the CB approach of 'banding' for assigning the risk of a given hazard to one of several - typically four - levels. Expert models use quantitative risk assessment methods to stratify the risk and define the boundaries between strata. They use data to assign the efficacy of control measures into bands. International collaborations are developing toolkits as 'preventive' measures for OSHH experts and non-experts alike. Toolkits should guide non-professionals, and inform professionals. International CB workshops have promoted CB expansion, research, and publications. They have been a focal point for original applications of simplified risk banding and control approaches for silica exposure, ergonomics, and safety [31,36] and have led to this international collaborative opportunity. Construction industry risk banding requires identifying the right safety solutions across OSHH disciplines to achieve injury and illness prevention. Assigning a band to a project, just as for tasks, is a practical approach to identify and reduce risks relating to work-related accidents and disease.

Construction stakeholders under NIOSH assembled a National Construction Agenda. The agenda provides a framework upon which to develop and promote a construction toolbox, including intermediate goals that build upon task-based control measures, and moves towards pre-job planning, awareness training, competent person training, and CB use. However, interest of US researchers and practitioners in CB construction applications has not led to the development of a toolbox for use by 'duty holders' - employers, designers and contractors. A variety of applications, generally falling under the rubric of "task-based" approaches or toolkits, align with CB risk banding concepts. For example, construction researchers recognized early on that "task-based sampling" was most appropriate for understanding and controlling exposures with construction activities [21,66,67]. Multiple opportunities to utilize risk-based CB strategies in the construction industry exist.

Safety science has qualitative and semi-quantitative tools to assess risks [68,69]. Risk is seen as a numeric variable. Simplistically, it combines an adverse effect (or its severity) with a probability of that consequence. Probabilities and consequences are classified into groups and provided with a value. Simple multiplication of values for probability and consequence produce a risk score, used to compare one risk with another for prioritization. An exposure/frequency estimate of hazard and probability of specified consequences for scenarios are compared [69]. Other variations of these tools can include the numbers exposed or the degree to which risk can be controlled via 'relative ranking'. The RL model most often used is divided into four categories, with determination by frequency and severity of hazard. This RL approach has been used recently for an occupational hygiene qualitative risk assessment to control nanoparticle material exposure [35] and as part of a Risk Level Based Management System (RLBMS). The RLBMS is a risk-based occupational risk management model, designed to focus OSHH resources on the highest workplace risks. This model is also auditable, so it fits OSHH management systems and national regulatory oversight [37].

The RLBMS model is an appropriate framework for bringing together the control-focused research and solutionsbased approaches [37]. RLBMS has shown consistency in integrating multiple solutions across the OSHH professions utilizing an RL delineation of hazards and commensurate controls. Strengths include the use of qualitative risk assessment to achieve regulatory compliance and standardizing a wide variety of tasks. Trades and tasks of the construction industry are more limited, especially for SMEs. RLBMS and solutions-based toolkits offer simple identification and control measures that can fit into a single toolbox. It requires identifying OSHH risks and risk reduction steps for each project phase. The RLBMS approach provides a step-by-step mechanism for creating this toolbox. It takes control solutions from research and good practice, organized within simple project-based and task-based formats. This simple format requires a toolkit structure layered by level of complexity of control solutions. Also necessary is addressing the National Construction Agenda (stakeholders' consensus) to secure pre-job planning to ensure the appropriate level of worksite supervisor training to identify controls matching task-related OSHH risks. This requires a project-specific RL. Therefore, within this framework design proposal we first provide a method to obtain a project specific RL and then present the layered toolkit structure by control levels (CL).

In addressing the need for a project specific RL, Table 1 presents a concept for a PJHA checklist establishing a project-specific band by RL. The table is based on the research-derived hazards inherent to construction trades. Its purpose is to score the hazards within a given construction project. The 'severity checklist' contains common chemical, physical and safety hazards determined independently from specific tasks. The 'probability checklist' determines 'exposure': the project scale, duration, number of workers, overall dustiness, and overall 'potential energy' estimate for project completion. This estimate is based on the concept: higher inherent potential energy yield higher adverse outcome risk from its release. Silica exposures are higher from grinding versus manual breaking; metal fume exposures are higher from torch cutting than mechanical cutting. More energy can lead to more noise; more energy is used in manual handling then with dollies, than utilizing machinery. Higher energy equipment has more severe consequences in the event of electric shock, or heavy equipment failure. Work at height or in trenches implies a potential energy released through a fall. Responses to 'severity' and 'probability' should avoid consideration of control measures.

Scores for PJHA severity and probability are each individually added. Each score is then found, within a given range, based on a 4 × 4 matrix (Fig. 1). Their intersection determines the RL for the construction project and is the first step in this Construction Toolbox design. The RL identifies the level of training and expertise to match the inherent project's risk at the earliest stage [4]. The RL also indicates the degree of expertise needed for project pre-planning. The next step for the project lead is to identify each of the tasks performed on the jobsite. Securing the appropriate control measures per task is performed using the solutions-based models identified above prior to work commencement. The PJHA RL outcome assists in identifying when control measures for specific tasks require higher expertise then the project lead possesses. As the RL is determined independently from tasks, higher expertise must be obtained for the task or a substitution for a lower risk task approach can be made.

The 'toolbox approach' takes into account the 'mentoring relationship' that is (or should be) present in construction trades. An inexperienced apprentice is teamed with an experienced craftsman as mentor, to develop the skills - the knowledge base - of the craft. This process can ensure both competence and an understanding of the craft's OSHH dimensions. Skilled workers are differentiated from apprentices by 'card-carrying' status, certifying 'skill-of-the-craft'. Many European countries and US states require, or are working to require, card-carrying construction trade workers on jobsites, ensuring they possess the skill-of-the-craft to perform their work to codes and regulations. In GB, the Sector Skills Council promotes OSHH skills for construction employees. Defining 'levels of training' in the Construction Toolbox meets this concept. An apprentice may attain 'Basic Craft Skills' with a minimum of training under a mentor, working to skill-based 'Hazard Awareness' by trade at the card-carrying level. In the US, OSHA regulations require higher level training to become 'Competent Persons', to oversee specific activities with inherently higher risk, fitting regulatory requirements discussed above. RL4 work requires 'Expert Training', to assist in understanding and controlling multiple risks.

The key boundary is between RL2 and RL3 - workers will need to be able recognize:

When work is, and is not, within their skill-of-the-craft and

With a project specific RL determined, the final step is to assist the jobsite manager in accessing control solutions utilizing a layered toolkit structure (Fig. 2).

Each layer reflects a CL in this manner:

CL1 is the universal precautions model. This level deals with the general hazards at the workplace such as tripping and falling as well as head, foot, hand, ear, and body protection. These hazards apply worldwide to everybody at the construction site and everybody at the construction site must have knowledge of these and follow worksite controls identified.

Planning the project prior to initiating work will require the determination of appropriate CLs for each standardized task. Task-related control measures are selected from available options at the specified CL. As indicated above, these are research and solutions-based resources. The advantage of such a layered model is that CL1 and probably CL2 can be filled on a worldwide uniform scale. Knowledge, instruments, factsheets and checklists are all available at these levels. When tasks are at higher levels of risk, such control measures normally need tailoring to project tasks. The CL helps identify the degree of tailoring and type of help necessary for complex situations. Designations CL3 and CL4 mean that workers need help with control measures from a Competent Person or an OSHH specialist. CL3 and CL4 are intentionally aligned in this manner to ensure the provision of effective control measures, and their sustained and correct use.

The availability and usefulness of a Construction Toolbox will require:

A web-based format for standardized tasks and related CLs that is continually updated,

Sharing control solutions and lessons learned, e.g. post on website, require CGSs that include:

Checklists for control measures and barriers, and

The utility of CB toolkits to deliver effective control advice to SMEs through CGSs has been shown through existing review and critique publications, however the gaps in field studies remain and further research is necessary for the issues specific to the construction industry [36,74,75]. These toolkits also require testing of formats to optimize, for users, 'drill-down' for access to control advice based on tasks that they recognize. Tasks should include variables such as those in Table 1, e.g. duration, other workers' proximity, the variety of controls that might be available. 'Drill-downs' produce CGSs that include task summary and generic control measures and/or barriers, or specific CGSs as necessary for tasks. Web-based 'drill-down' actively linked to the Construction Toolbox have potential for currency, updating and real-time translations. This would enhance the risk management aspect, communicate hazard-to-control to the worker, and offer field-based advice to others in a participatory format. The PJHA can also be similarly useful. For SMEs, each question can be linked to a brief explanation and additional resources links as they determine the CL, task-by-task. The SME manager can begin to consider all opportunities for hazard or task substitution, and selecting task parameters to reduce the overall expertise required. Users and experts can score online resources such as CGSs and CL-based solutions for utility, simplicity, and effectiveness as feedback, for evaluation. SMEs can also get Construction Toolboxes on CD by trade, having 'drill-down' format, but no web-based benefits.

In seeking to address these issues, the intent is to remain global in scope. However, many of the current control solutions are skewed toward a few countries [74]. The United Nations' Globally Harmonized System of Classification and Labelling of Chemicals (GHS) is well suited for offering a needed global consistency in the international identification of chemicals. The GHS is a system for standardizing and harmonizing the classification and labeling of chemicals which would be beneficial in addressing chemical exposures in construction as there is a clear correspondence between European risk phrases and GHS classifications for use in CB toolkits [31,36,74,75]. There are often national research gaps, so international research and literature requires locating and consideration. In economically developing countries the number of OSHH professionals and technicians need substantial growth [74,75]. The Construction Toolbox can become a foundation for training OSHH experts and technicians in construction in university programs, and spreading expertise through train-the-trainer campaigns. Developed countries can also use such campaigns, with exchange of successful control information where language barriers exist [75]. The process can work best internationally when key aspects of the CL approaches in the CGS are communicated largely through pictorial formats, to minimize the need for translation and standardizing the control expectations [74]. For example, the HSE is developing a short series of simple icons as an 'employee checklist'. But this whole context is reliant on a Construction Toolbox existence, acceptance, dissemination, and use. Therefore, the authors would advocate that ILO or WHO set up an international working group to collect and order existing information and to make this readily available (e.g., internet or booklets). In this manner, as experts are lacking in many developing countries, an initial goal to 'pick the low-hanging fruit' would be a solid step in right direction [74]. If all countries implemented simple, practical strategies to prevent accidents, it would be possible to eliminate 83% of safety-related deaths and 74% of accidents annually [76].