Hazard substitution

Hazard substitutions can involve not only changing one chemical for another, but also using the same chemical in a less hazardous form. Substitutions can also be made to processes and equipment. In making a substitution, the hazards of the new material should be considered and monitored, so that a new hazard is not unwittingly introduced, causing "regrettable substitutions". Substitution can also fail as a strategy if the hazardous process or material is reintroduced at a later stage in the design or production phases, or if cost or quality concerns cause a substitution to not be adopted.

Examples

Chemicals

A common substitution is to replace a toxic chemical with a less toxic one. Some examples include replacing the solvent benzene, a carcinogen, with toluene; switching from organic solvents to water-based detergents; and replacing paints containing lead with those containing non-leaded pigments. Dry cleaning can avoid the use of toxic perchloroethylene by using petroleum-based solvents, supercritical carbon dioxide, or wet cleaning techniques. Chemical substitutions are an example of green chemistry.

Chemicals can also be substituted with a different form of the same chemical. In general, inhalation exposure to dusty powders can be reduced by using a slurry or suspension of particles in a liquid solvent instead of a dry powder, or substituting larger particles such as pellets or ingots. Some chemicals, such as nanomaterials, often cannot be eliminated or substituted with conventional materials because their unique properties are necessary to the desired product or process. However, it may be possible to choose properties of the nanoparticle such as size, shape, functionalization, surface charge, solubility, agglomeration, and aggregation state to improve their toxicological properties while retaining the desired functionality.

In 2014, the U.S. National Academies released a recommended decision-making framework for chemical substitutions. The framework maintained health-related metrics used by previous frameworks, including carcinogenicity, mutagenicity, reproductive and developmental toxicity, endocrine disruption, acute and chronic toxicity, dermal and eye irritation, and dermal and respiratory sensitization, and ecotoxicity. It added an emphasis on assessing actual exposure rather than only the inherent hazards of the chemical itself, decision rules for resolving trade-offs among hazards, and consideration of novel data sources on hazards such as simulations. The assessment framework has 13 steps, many of which are unique, such as dedicated steps for scoping and problem formulation, assessing physicochemical properties, broader life-cycle assessment, and research and innovation. The framework also provides guidance on tools and sources for scientific information.

Processes and equipment

Hazards to workers can be reduced by limiting or replacing procedures that may aerosolize toxic materials contained in the item. Examples include limiting agitation procedures such as sonication, or by using a lower-temperature process in chemical reactors to minimize release of materials in exhaust. Substituting a water-jet cutting process instead of mechanical sawing of a solid item also creates less dust.

Equipment can also be substituted, for example using a self-retracting lifeline instead of a fixed rope for fall protection, or packaging materials in smaller containers to prevent lifting injuries. Health effects from noise can be controlled by purchasing or renting less noisy equipment. This topic has been the subject of several Buy Quiet campaigns, and the NIOSH Power Tools Database contains data on sound power, pressure, and vibration levels of many power tools.