Hazard substitution
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Hazard substitution is a hazard control strategy in which a material or process is replaced with another that is less hazardous. Substitution is the second most effective of the five members of the
hierarchy of hazard controls Hierarchy of hazard control is a system used in industry to minimize or eliminate exposure to hazards.
in protecting workers, after elimination. Substitution and elimination are most effective early in the design process, when they may be inexpensive and simple to implement, while for an existing process they may require major changes in equipment and procedures. The concept of
prevention through design Prevention through design (PtD), also called safety by design usually in Europe, is the concept of applying methods to minimize occupational hazards early in the design process, with an emphasis on optimizing employee health and safety throughou ...
emphasizes integrating the more effective control methods such as elimination and substitution early in the design phase. 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 A solvent (s) (from the Latin '' solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a solution. A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid. Water is a solvent for ...
benzene Benzene is an organic chemical compound with the molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atoms, ...
, a
carcinogen A carcinogen is any substance, radionuclide, or radiation that promotes carcinogenesis (the formation of cancer). This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes. Several radioactive substan ...
, with
toluene Toluene (), also known as toluol (), is a substituted aromatic hydrocarbon. It is a colorless, water-insoluble liquid with the smell associated with paint thinners. It is a mono-substituted benzene derivative, consisting of a methyl group (CH3) at ...
; switching from organic solvents to water-based
detergent A detergent is a surfactant or a mixture of surfactants with cleansing properties when in dilute solutions. There are a large variety of detergents, a common family being the alkylbenzene sulfonates, which are soap-like compounds that are more ...
s; and replacing paints containing
lead Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...
with those containing non-leaded pigments.
Dry cleaning Dry cleaning is any cleaning process for clothing and textiles using a solvent other than water. Dry cleaning still involves liquid, but clothes are instead soaked in a water-free liquid solvent. Tetrachloroethylene (perchloroethylene), known in ...
can avoid the use of toxic
perchloroethylene Tetrachloroethylene, also known under the systematic name tetrachloroethene, or perchloroethylene, and many other names (and abbreviations such as "perc" or "PERC", and "PCE"), is a chlorocarbon with the formula Cl2C=CCl2 . It is a colorless liq ...
by using
petroleum Petroleum, also known as crude oil, or simply oil, is a naturally occurring yellowish-black liquid mixture of mainly hydrocarbons, and is found in geological formations. The name ''petroleum'' covers both naturally occurring unprocessed crud ...
-based solvents,
supercritical carbon dioxide Supercritical carbon dioxide (s) is a fluid state of carbon dioxide where it is held at or above its critical temperature and critical pressure. Carbon dioxide usually behaves as a gas in air at standard temperature and pressure (STP), or as ...
, or
wet cleaning Wet cleaning refers to methods of professional cleaning that, in contrast to traditional dry cleaning, avoids the use of chemical solvents, the most common of which is tetrachloroethylene (commonly called perchloroethylene or "perc"). Environment ...
techniques. Chemical substitutions are an example of
green chemistry Green chemistry, also called sustainable chemistry, is an area of chemistry and chemical engineering focused on the design of products and processes that minimize or eliminate the use and generation of hazardous substances. While environmental che ...
. Chemicals can also be substituted with a different form of the same chemical. In general, inhalation exposure to
dusty Dusty may refer to: Places in the United States * Dusty, New Mexico, an unincorporated community * Dusty, Washington, an unincorporated community * Dusty Glacier, Washington People * Dusty (given name) * Dusty (nickname) * Slim Dusty, Austra ...
powders can be reduced by using a
slurry A slurry is a mixture of denser solids suspended in liquid, usually water. The most common use of slurry is as a means of transporting solids or separating minerals, the liquid being a carrier that is pumped on a device such as a centrifugal pu ...
or
suspension Suspension or suspended may refer to: Science and engineering * Suspension (topology), in mathematics * Suspension (dynamical systems), in mathematics * Suspension of a ring, in mathematics * Suspension (chemistry), small solid particles suspend ...
of particles in a liquid solvent instead of a dry powder, or substituting larger particles such as pellets or
ingot An ingot is a piece of relatively pure material, usually metal, that is cast into a shape suitable for further processing. In steelmaking, it is the first step among semi-finished casting products. Ingots usually require a second procedure of sh ...
s. Some chemicals, such as
nanomaterials * Nanomaterials describe, in principle, materials of which a single unit is sized (in at least one dimension) between 1 and 100 nm (the usual definition of nanoscale). Nanomaterials research takes a materials science-based approach to nan ...
, 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 Size in general is the Magnitude (mathematics), magnitude or dimensions of a thing. More specifically, ''geometrical size'' (or ''spatial size'') can refer to linear dimensions (length, width, height, diameter, perimeter), area, or volume ...
,
shape A shape or figure is a graphics, graphical representation of an object or its external boundary, outline, or external Surface (mathematics), surface, as opposed to other properties such as color, Surface texture, texture, or material type. A pl ...
, functionalization,
surface charge Surface charge is a two-dimensional surface with non-zero electric charge. These electric charges are constrained on this 2-D surface, and surface charge density, measured in coulombs per square meter (C•m−2), is used to describe the charge di ...
,
solubility In chemistry, solubility is the ability of a substance, the solute, to form a solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form such a solution. The extent of the solubil ...
,
agglomeration Agglomeration may refer to: * Urban agglomeration, in standard English * Megalopolis, in Chinese English, as defined in China's ''Standard for basic terminology of urban planning'' (GB/T 50280—98). Also known as " city cluster". * Economies of ag ...
, and aggregation state to improve their toxicological properties while retaining the desired functionality. In 2014, the U.S.
National Academies A national academy is an organizational body, usually operating with state financial support and approval, that co-ordinates scholarly research activities and standards for academic disciplines, most frequently in the sciences but also the humanit ...
released a recommended decision-making framework for chemical substitutions. The framework maintained health-related metrics used by previous frameworks, including
carcinogen A carcinogen is any substance, radionuclide, or radiation that promotes carcinogenesis (the formation of cancer). This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes. Several radioactive substan ...
icity,
mutagen In genetics, a mutagen is a physical or chemical agent that permanently changes nucleic acid, genetic material, usually DNA, in an organism and thus increases the frequency of mutations above the natural background level. As many mutations can ca ...
icity,
reproductive The reproductive system of an organism, also known as the genital system, is the biological system made up of all the anatomical organs involved in sexual reproduction. Many non-living substances such as fluids, hormones, and pheromones are als ...
and
developmental toxicity Development of the human body is the process of growth to maturity. The process begins with fertilization, where an egg released from the ovary of a female is penetrated by a sperm cell from a male. The resulting zygote develops through m ...
,
endocrine disruption Endocrine disruptors, sometimes also referred to as hormonally active agents, endocrine disrupting chemicals, or endocrine disrupting compounds are chemicals that can interfere with endocrine (or hormonal) systems. These disruptions can cause c ...
,
acute Acute may refer to: Science and technology * Acute angle ** Acute triangle ** Acute, a leaf shape in the glossary of leaf morphology * Acute (medicine), a disease that it is of short duration and of recent onset. ** Acute toxicity, the adverse eff ...
and
chronic toxicity Chronic toxicity, the development of adverse effects as a result of long term exposure to a contaminant or other stressor, is an important aspect of aquatic toxicology. Adverse effects associated with chronic toxicity can be directly lethal but are ...
,
dermal The dermis or corium is a layer of skin between the epidermis (with which it makes up the cutis) and subcutaneous tissues, that primarily consists of dense irregular connective tissue and cushions the body from stress and strain. It is divided ...
and eye irritation, and dermal and respiratory
sensitization Sensitization is a non-associative learning process in which repeated administration of a stimulus results in the progressive amplification of a response. Sensitization often is characterized by an enhancement of response to a whole class of stim ...
, and
ecotoxicity Ecotoxicity, the subject of study in the field of ecotoxicology (a portmanteau of ecology and toxicology), refers to the biological, chemical or physical stressors that affect ecosystems. Such stressors could occur in the natural environment at ...
. 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 A simulation is the imitation of the operation of a real-world process or system over time. Simulations require the use of models; the model represents the key characteristics or behaviors of the selected system or process, whereas the s ...
. The assessment framework has 13 steps, many of which are unique, such as dedicated steps for scoping and problem formulation, assessing
physicochemical Physical chemistry is the study of macroscopic and microscopic phenomena in chemical systems in terms of the principles, practices, and concepts of physics such as motion, energy, force, time, thermodynamics, quantum chemistry, statistical mecha ...
properties, broader
life-cycle assessment Life cycle assessment or LCA (also known as life cycle analysis) is a methodology for assessing environmental impacts associated with all the stages of the Product lifecycle, life cycle of a commercial product, Process lifecycle, process, or ...
, 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 A sonicator at the Weizmann Institute of Science during sonicationSonication is the act of applying sound energy to agitate particles in a sample, for various purposes such as the extraction of multiple compounds from plants, microalgae and seawe ...
, or by using a lower-temperature process in
chemical reactor A chemical reactor is an enclosed volume in which a chemical reaction takes place. In chemical engineering, it is generally understood to be a process vessel used to carry out a chemical reaction, which is one of the classic unit operations in chem ...
s 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 Noise health effects are the physical and psychological health consequences of regular exposure to consistent elevated sound levels. Noise from traffic, in particular, is considered by the World Health Organization to be one of the worst environm ...
can be controlled by purchasing or renting less noisy equipment. This topic has been the subject of several
Buy Quiet Buy Quiet is an American health and safety initiative to select and purchase the lowest noise emitting power tools and machinery in order to reduce occupational and community noise exposure. Buy Quiet Programs are examples of noise control strategi ...
campaigns, and the
NIOSH Power Tools Database The NIOSH Power Tools Database contains sound power levels, sound pressure levels, and vibrations data for a variety of common power tools that have been tested by researchers. Data are collected for both the unloaded and loaded use of power tools ...
contains data on sound power, pressure, and vibration levels of many power tools.


Regrettable substitutions

A regrettable substitution occurs when a material or process believed to be less hazardous turns out to have an unexpected hazard. One well-known example occurred when
dichloromethane Dichloromethane (DCM or methylene chloride, methylene bichloride) is an organochlorine compound with the formula . This colorless, volatile liquid with a chloroform-like, sweet odour is widely used as a solvent. Although it is not miscible with ...
was phased out as a
brake cleaner Brake cleaner, often also called '' parts cleaner'', is a mostly colorless cleaning agent, mainly used for cleaning the brake disks, the engine compartment and underfloor of motor vehicles. An important feature is that the brake cleaner leaves n ...
due to its environmental effects, but its replacement ''n''-hexane was subsequently found to be
neurotoxic Neurotoxicity is a form of toxicity in which a biological, chemical, or physical agent produces an adverse effect on the structure or function of the central and/or peripheral nervous system. It occurs when exposure to a substance – specificall ...
. Often the substances being replaced have well-studied hazards, but the alternatives may have little or no toxicity data, making alternatives assessments difficult. Often, chemicals with no toxicity data are considered preferable since they do not prompt such concerns as a California Proposition 65 warning. Another type of regrettable substitution involves shifting the burden of a hazard to another party. One example is that the potent neurotoxin
acrylamide Acrylamide (or acrylic amide) is an organic compound with the chemical formula CH2=CHC(O)NH2. It is a white odorless solid, soluble in water and several organic solvents. From the chemistry perspective, acrylamide is a vinyl-substituted primary ...
can be replaced with the safer ''N''-vinyl formamide, but the synthesis of the latter requires use of the highly toxic
hydrogen cyanide Hydrogen cyanide, sometimes called prussic acid, is a chemical compound with the formula HCN and structure . It is a colorless, extremely poisonous, and flammable liquid that boils slightly above room temperature, at . HCN is produced on an ...
, increasing the hazards to workers in the manufacturing firm. In performing an
alternatives assessment Alternatives assessment or alternatives analysis is a problem-solving approach used in environmental design, technology, and policy. It aims to minimize environmental harm by comparing multiple potential solutions in the context of a specific proble ...
, including the effects over the entire
product lifecycle In industry, Product Lifecycle Management (PLM) is the process of managing the entire lifecycle of a product from its inception through the engineering, design and manufacture, as well as the service and disposal of manufactured products. PL ...
as part of a
life-cycle assessment Life cycle assessment or LCA (also known as life cycle analysis) is a methodology for assessing environmental impacts associated with all the stages of the Product lifecycle, life cycle of a commercial product, Process lifecycle, process, or ...
can mitigate this.


References

{{Underwater diving, divsaf Industrial hygiene Safety engineering Risk analysis