Substitution means replacing hazardous chemicals with safer alternatives. It is at the top of the hierarchy of control measures applied to substances. Substitution, however, does not only apply to chemicals, it has been a general legal provision for over two decades (Directive 89/391/EEC) . Newer chemical legislation, such as Regulation No 1907/2006 (REACH)  enhances the need to substitute hazardous substances. Tools useful for substitution are available as well as shared knowledge to help in the process.
Substitution, in this article, refers to the replacement of hazardous chemicals by safer substances, but also by other type of measures: technological and organisational measures, and product revision.
Substitution of hazardous chemicals is a way to transpose into chemical risk management the general principle of ‘replacing the dangerous by non-dangerous or less dangerous’, as stated in the Directive 89/391/EEC (Framework Directive) .
According to the Chemical Agents Directive 98/24/EC  ‘substitution should be by preference undertaken’. Substitution of hazardous substances and mixtures with less hazardous alternatives is a basic principle of any good chemical risks management and legal requirement according to workplace legislation. Some substances are restricted to certain uses or their use requires an authorisation . Substitution is a basic principle of any good chemical risks managementgood chemical risk management. It is also a legal requirement, like in the Carcinogens and Mutagens Directive 2004/37/EC , which stipulates that carcinogens and mutagens shall be substituted.
The Carcinogens and Mutagens Directive 2004/37/EC  stipulates that carcinogens and mutagens shall be substituted. Substitution has to be applied for the most hazardous substances: the substances of very high concern (SVHC). According to REACH (see also: REACH effects/impact on workplaces) these are substances that are carcinogenic, mutagenic and toxic to reproduction (CMR)(see also: Carcinogenic, mutagenic, reprotoxic (CMR) substances); persistent, bioaccumulative and toxic (PBT), very persistent and very bioaccumulative (vPvB) or substances of equivalent level of concern, like the endocrine disruptors.
REACH states that when applying for the authorisation of substances of very high concern the registrant has to provide an analysis of the alternatives, considering their risks and the technical and economic feasibility. If suitable alternatives are available, a substitution plan, including a timetable of the applicant’s proposed actions, has to be submitted. The obligations mentioned above have to be observed and treated as priorities. However, less hazardous substances may also be replaced, since substitution is a general recommendation of the chemicals legislation .Paying proper attention to observing priorities should not exclude initiatives to substitute chemicals that are not SVHC. The legal provisions place substitution at the top of the hierarchy of control measures . Several such hierarchy models exist (see also: Hierarchy of controls applied to dangerous substances). Some place substitution at the very top of the hierarchy, others put elimination ahead of it. Since legislation states that substitution can also be done by replacing a chemical with a process (making the hazardous substance unnecessary), elimination can be considered a form of substitution. There are also differences between hierarchy models regarding the level below substitution: technical controls (or process measures). Some of them consider substitution also includes measures that instead of avoiding a hazardous substance, just dilute it or reduce its potential for generating emissions.
In this article, substitution means replacement with a safer alternative, whether this is a substance, a mixture/material, or a process. It does not include measures that just reduce exposure while still using the hazardous substance, even if at lower concentrations/quantities or in forms which are less likely to become airborne (e.g. by using paste instead of powder).
The alternative process may include, besides technological processes re-organising of the work process or procedures, as well as product revision. This is in line with the definition used by Lohse & Lissner: ‘The replacement of hazardous substances in products and processes by less hazardous or non-hazardous substances or by achieving an equivalent functionality via technological or organizational measures’ .
For example (categorization is just formal) substitution may be done by:
- Using different and safer substance(s) instead of the initial one (substitution by substance/s or material), e.g. glycerol acetate as an alternative to phthalate plasticisers in coatings;
- Using a technological alternative instead of the initial substance (substitution by process), e.g. deep freezing instead of formaldehyde for preserving biological samples;
- Using an organisational measure as replacement for a hazardous substance (substitution by procedure), e.g. replacing mercury switches in some X Ray machines with manual adjustment by the operator;
- Changing the product so that the substance is no longer needed (substitution by re-design). A known example is eliminating adhesives by redesigning product shapes so they can be assembled manually (by click).
Regardless of its type, substitution should really make a positive difference for health and safety. Shifting hazards (e.g. from chemical to physical), or using inappropriate control measures for the alternative, may lead to situations in which the overall risk is higher than before substitution. Confusing the lack of data on certain hazards with the absence of those hazards could also make substitution ineffective. While substitution examples may be transferrable, there would be a need to assess them on a case by case basis, taking the specific conditions of the workplace, company and work procedures into account, as well as the conditions arising during maintenance and in the case of foreseeable accidents. There cannot be a “generic" approach to substitution.
As well as being a legal requirement, substitution can also be done voluntarily. Many companies have lists of substances that are banned or restricted in their products or activities (‘grey or black lists’). Some of these substances are not (yet) restricted by law.
Though this article refers to substitution of hazardous chemicals, hazardous processes, like those mentioned in the Carcinogens and Mutagens Directive , should also be considered for substitution. For example, strong acid mists are according to some sources  but they are not classified as carcinogens in the EU harmonized system  (see also: Labelling of chemicals). However they are included in a process classified as carcinogenic in the EU :’strong acid process in the manufacture of isopropyl alcohol’. So, here too, companies have a legal obligation to look for safer alternatives.
Legal banning or restricting of a substance has proven to be one of the strongest drivers for substitution. Faced with the impossibility to produce, distribute, use or import/export a substance, interested parties have found one or more substitutes . REACH is expected to have a significant influence in this respect when substances are included as candidates for restriction and authorisation. Workplace experience and epidemiological information can promote such restrictions (an example would be the acid mists as mentioned above).
Stakeholder requirements may support substitution. Whether internal (workers, OSH specialists, trade unions) or external (NGOs, sector organisations, financiers, mass-media) they may put pressure to stop working with hazardous substances and find safer alternatives.
Cost cutting may be achieved by reducing expenditure caused by workers’ ill-health, and on end-of-pipe measures like neutralisation of emissions and wastes. Substitution has the advantage of addressing the root cause of the problem. It may change the working process to the point of reducing or even making redundant some protective measures. Also, alternatives may be (or become) cheaper than the initial substances.
Competitive advantage: placing a new, safer substance on the market before competitors may have immediate economical benefits for the company, and promote further developments.
Creating a responsible and modern image for the company by demonstrating care for workers, clients and the environment, improves credibility. On the other hand, pretending to care (e.g. by ‘window dressing’ or ‘greenwashing’) will rapidly deteriorate the image and confidence, first internally and eventually externally.
Technical progress may lead to safer alternatives and improved methods for testing their properties and their effects on health and the environment.
Common barriers to implementing substitution are economical (direct and indirect costs), technological, performance (technical requirements, client expectations) , lack of knowledge on dangerous properties of alternatives, lack of enforcement (inefficient control from authorities), lack of motivation (no incentives, reduced public interest) and awareness (ignoring hazards, unknown costs of not substituting), fear of change.
Substitution may be an isolated event in a company or it may be part of a more systematic approach or policy at company/sector or local/regional level.
It should be integrated in the general policies and plans of companies, making good use of existing knowledge within the companies (see also: Learning from incidents and accidents) and of the relations with external stakeholders (partners, authorities, shareholders, supply chain, clients).
Making substitution part of the preventive culture (see also: Towards an occupational safety and health culture) of the company helps to identify problems earlier - spotting opportunities, acting in a coherent way and gaining broader support.
Multidisciplinary teams are generally needed, depending on the nature and complexity of the substitution. Such teams should include preventive services and occupational physicians, technical personnel, and workers representatives.
Workers have to be informed, encouraged and involved in identifying possible substitutions and discussing the appropriateness of their implementation, as well as when putting them into practice. The fact that substitution is a change (sometimes an innovation) may be stimulating in some cases, but in others it will challenge companies’ and workers´ capacities to adapt, to change mindsets, and to control things while under development. Information exchange along the supply chain or at sector level can promote substitution initiatives and share practical experience .
The right timing for substitution is influenced by the availability and the costs of substitution. Big companies can afford to make a competitive advantage of putting on the market or using a new and safer alternative, even while prices are still high. Small companies might need to wait for prices to go down.
A critical issue the is the current state of knowledge on the long-term effects of substances. In some notorious cases, like asbestos, (see also: Asbestos) chemicals were proven unsafe after many years of intensive use. Such cases make it hard to decide on implementing alternatives, especially when they are not supported by long-term epidemiological studies. Constant improvement of laboratory tests and modelling methods are expected to provide more reliable data and in shorter time. A precautionary approach is recommended, and substitution by unknown substances should be avoided until clarification is forthcoming, in particular if the current risk is low and may not justify such a step.
A risk assessment (see also: Occupational safety and health risk assessment methodologies) for the alternative should determine if risk is reduced, and what protective measures are required. An alternative will rarely be the safest for all hazard endpoints. Decision on what alternative to adopt should consider which hazard is more likely to generate high risks levels, and which one the company is better able to control. As well as chemical risks , other risks should also be considered that could impact negatively on health and safety (e.g. risk of fire and explosion risks). The impact on the main working processes and on auxiliary activities like maintenance should be considered, as well as the consequences of possible accidents. Working procedures, protective and preventive measures already in place may need to be amended or supplemented. Companies could develop purchasing procedures to select for safer chemicals and products as they become available.
The principle of substitution to avoid chemicals of high concern can also be applied to the design of new products or processes, which is a preferable preventive approach.
The following steps are general and indicative, and can be adjusted, if appropriate, to bring about the desired result:
- Organising a working group
Insure appropriate representation of workers and employers, and integrate all required expertise. Include those directly involved in using/producing the substance (technicians, workers). Make a work plan with well-defined roles for all stages. Take measures to ensure an efficient information flow between the group, the rest of the company and its stakeholders. Maintain a collaborative, open–minded atmosphere.
- Defining the problem
List the substances to be substituted. Be clear on why you make these choices. Prioritise substitution according to legal provisions, company policy and stakeholder perspective. Define the function that a substance has and how it is integrated in the rest of the process/product. List the required conditions for this function to perform adequately (temperature, acidity, pressure, chemical compatibility, etc). An alternative should fit these conditions, or the system/product will need to be changed, to a greater or lesser degree. Define what quality the substance gives to the process or to the final product. If that quality is not actually necessary needed (e.g. some commercial attributes) the substance may be eliminated. Otherwise, an alternative is needed.
- Setting substitution criteria
Set criteria for selecting possible alternatives. Initially, fewer (pre)screening criteria may be used. This would eliminate at an early stage those alternatives that are not safe enough CMRs and substances of equivalent concern, such as endocrine disruptors, also sensitisers or neurotoxicants should not be chosen as alternatives . Other criteria may be added to differentiate between alternatives that have passed the screening criteria. Cost, availability on the local market, and other advantages may be considered.
- Searching for alternatives
Solutions may be found inside the company. Searching other sources is also important. Alternatives already developed and implemented may lower innovation costs and risks. Internet sources, official reports, supplier chain, professional or sectorial associations or authority representatives may provide useful information. Another approach is to ask the supplier to formulate a safer alternative. Some companies offer support in selecting the right product, or may even be willing to reformulate the initial one (especially for important clients).
- Assessing and comparing alternatives
Assess all alternatives using the same method or tool to allow for comparison. Select those alternatives that best fit the nature and dimension of the problem and that provide indeed an overall risk reduction.
- Experimenting on pilot scale
Try substitution on a smaller scale to see if it lives up to expectations in terms of safety, technical and environmental performance. Compare costs against those initially forecast, and estimate if feasible when transposed at full scale.
- Implementing, re-evaluating
Plan carefully for full-scale implementation. Evaluate the risks (see also: Risk management tools for dangerous substances) and take appropriate measures. Review as necessary the supply chain, training needs, monitoring (see also: Monitoring, sampling and analysis of airborne dangerous substances), and other procedures.
Tools and information sources
Collecting and assessing data on alternatives are key elements in the substitution process. Several tools can be used in substitution . SMEs mostly benefit from tools that are easy to use and for which entry data can be obtained from the Safety Data Sheets of substances or products (e.g. the Column Model). Tools that require more detailed (eco)toxicological data are also freely available, but using them may require a specialist or experienced operator (Green Screen, P2Oasys).
Examples of tools that may be used for substitution:
- Column Model for Chemical Substitutes Assessment - an easy to use method that compares alternatives, ranking hazards according to severity levels, and considering emission factors, and considering the process employed. .
- Technical Rules for Hazardous Substances (TRGS 600) – is an easy to use guidance that structures information on: determination of substitution possibilities (with examples of information sources), criteria for pre-selecting substitutes (with examples of series that rank health/physicochemical hazards and release potential) and decision on substitution (criteria for technical suitability and criteria for health and physicochemical risk). TRGS 600 was developed by the German Committee on Hazardous Substances (AGS) and is available in German and English .
- Quick Scan – may be used by industry and authorities, but is not recommended to SMEs .It uses available or estimated data on hazards and levels of substance use, to rank chemicals on four levels of concern (from very high to low). Depending on the resulting level of concern substances management should be handled differently. Authorities should be in charge for substances of very high concern, those of lower concern being handled by industry. Quick Scan was elaborated by the Dutch Ministry of Housing, Spatial Planning and Environment and is available in Dutch and English .
- GISBAU- may be used to select safer products used in the construction sector based on a simple coding system that reflects the type of product (by letters) and its hazards ranking (by numbers). The approach is based on the idea that similar products with similar hazards could be addressed by similar control and prevention measures . Therefore GISBAU established 14 product groups like paints and varnishes, cementing admixtures, adhesives. Within each group the user may select the type of product that has a lower hazard ranking. Additional information for corresponding control measures is also available. GISBAU was elaborated by the Berufsgenossenschaft der Bauwirtschaft (the German Trade Association in the Construction Sector).
- Green Screen for Safer Chemicals - is a hazard based assessment tool that requires specialised training. It is increasingly used by companies in the USA and Canada and even by some in Europe to assess alternatives or to prove 12the comparative safety of their products . The tool sets threshold values for hazards (to humans and the environment) based on (eco)toxicological data (like NOEC - no observed effect concentration) or the hazard classification of substances. The tool sets threshold values for hazards to humans and environment based on (eco)toxicological data (like NOEC - no observed effect concentration) or hazard classification of substances. Combinations of different types of hazards and their level assigned according to the thresholds are used to rank a substance according to the following benchmarks:
- Benchmark 1: Avoid. Chemical of high concern
- Benchmark 2: Use but search for safer substitutes
- Benchmark 3: Use but still opportunity for improvement
- Benchmark 4: Safe chemical.
Green Screen was elaborated by Clean Production Action (US &Canada) and is available in English.
- Pollution Prevention Options Analysis System (P2OASys) - requires certain expertise that makes it unsuitable for SMEs . It is a complex tool that allows assessment of chemicals but also of processes and technology. P2OASys was designed by the Toxic Use Reduction Institute of Massachusetts (TURI) and is available in English.
- Information sources and databases:
- SUBSPORT – the Substitution Support Portal: All type of information needed in the substitution process is presented on the website of SUBSPORT, a Life project ( 2010-2012). The website provides links to substance lists, a case story database as well as basic guidance and training materials for substitution.
- CatSub is a catalogue with examples of substitution, self-assessed by the providers as being safer alternatives. Substitution cases are presented in English, German, Danish or French .
- Cleantool is a database with alternatives for parts cleaning, metal surface cleaning and degreasing, based on assessing processes used in various enterprises across Europe. It includes occupational, environmental and cost factors, and is available in English, German, French, and Spanish .
- RISCTOX includes a database on hazardous substances with substitution case studies (ALTERNATIVAS) and a tool to compare and assess alternatives. It is run by ISTAS and is available only in Spanish .
- Substitution-cmr is a database with examples of alternatives to CMR substances. It is available only in French .
- BASTA is a database for the construction sector, containing only products that pass BASTA criteria regarding health and environment. Products are self-assessed by the suppliers. It is available in Swedish and English .
The variety of substitutions and their context are presented in the examples below.
Construction sector - substitution by non-chemical alternative - personal initiative in an SME: A worker in a SME proposed the use of an electric, infrared (IR) heater to soften old paint, instead of the usual chemical procedure for stripping, based on dichloromethane. Initially, the proposal had nothing to do with occupational safety or environmental protection. The IR stripper was easier to transport, store and use than the chemicals. The substitution was well received by co-workers, who soon also noticed the OSH advantages. Moreover, unlike torch stripers, the IR device does not develop temperatures that volatilise hazardous components such as lead; nor does it create dusts, like mechanical methods (e.g. blasting). When the SME proposed it in its next subcontract offer as a “green solution’’, it made a good impression on the contractor and the beneficiary.
Health care sector - substitution by product changes (packaging) and organisational measures - part of a broader risk reduction plan. As part of the process to eliminate mercury in health care units, a hospital decided to use thimerosal free vaccines. Thimerosal (or thiomersal) is a mercury-containing preservative that stabilises vaccines. Using preservative free vaccines meant changing the supplying procedure: single vials instead of multiple vial vaccines were used, and the storing time was shortened. The hospital reduced chemicals risks and hazardous wasteswaste, and patients that rejected vaccines containing mercury were reassured.
Chemical industry - substitution by chemical - large company. One of the biggest manufacturers of chemicals synthesized 1,2-Cyclohexane dicarboxylic acid diisononyl ester (DINCH) as an alternative to phthalate plasticisers such as bis(2-ethylhexyl)phthalate (DEHP) which is classified as reprotoxicant and endocrine disruptor in the EU  and as possibly carcinogenic to humans by the International Agency for Research on Cancer . Released in 2002, it has been used successfully in sensitive applications such as medical devices, children’s products, and food. Today it is one of the most used alternatives to phthalate plasticisers.
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