In brief
Chemical substitution means replacing a hazardous product or process with a less hazardous one, and it sits at the top of the order of measures in the Chemical Substances Regulation. A good substitution decision answers three questions; does the new product do the job, are the hazard and exposure really reduced, and does it bring a new risk? These questions are answered with an SDS comparison, a controlled trial and a written decision.
What is chemical substitution, and what does the legislation require?
Chemical substitution means replacing a hazardous chemical or process used at work with an option that does the same job and is less hazardous. The concept is not new: Art. 5/1-e of Law No. 6331 on Occupational Health and Safety lists "replacing the dangerous by the non-dangerous or the less dangerous" among the principles of protection against risks.
The Regulation on Health and Safety Measures in Work with Chemical Substances ties this principle to an order. Under Art. 7/1-g, a non-hazardous or less hazardous chemical is used instead of a hazardous chemical by means of substitution. If substitution is not possible because of the nature of the work, the other steps, beginning with process and engineering measures, are applied according to the results of the risk assessment. The obligation is even stricter for carcinogenic and mutagenic substances; the search for substitutes must be documented. We explained this in our article on working with carcinogenic and mutagenic substances.
Substitution can take two forms:
- Substance substitution: The product itself changes. Example: water-based paint instead of paint containing toluene.
- Form or process substitution: The substance stays the same, but the form that causes exposure changes. Example: granular masterbatch instead of powder pigment, roller or brush instead of spraying, closed dosing instead of pouring from an open container.
We covered the place of substitution in the order of measures in general in our article on the hierarchy of controls. This article focuses on how the decision is made.
Substitution assessment step by step
A substitution assessment is carried out with documents, not with the supplier's claim that a product is "safer". Our suggested order:
- Define the current product: What function does the product serve, in which section, by whom, in what quantity and by what method is it used? Extract Sections 2, 8, 9 and 11 of the safety data sheet (SDS). For how to read it, see our article on how to read an SDS.
- Write down the technical requirements: Adhesion, drying time, working temperature, surface quality, customer specification and compatibility with existing equipment. A candidate that production will not accept is eliminated at the outset.
- Gather candidates: Ask suppliers for alternative products and the current Turkish-language SDS for each.
- Compare the hazards: Put the H statements side by side; carcinogenic, mutagenic, reprotoxic, respiratory or skin sensitiser statements carry the greatest weight.
- Compare exposure potential: Volatility (boiling point, vapour pressure), tendency to form dust, the quantity to be used and the application method. A less hazardous but much more volatile product may not reduce the overall risk.
- Look for new risks: Corrosiveness, allergy, fire, heat, ergonomics, waste and equipment compatibility.
- Trial, decide and record: After a controlled trial, the decision is put in writing.
For methods of scoring exposure, see our article on chemical risk assessment.
What can replace a hazardous chemical? Examples and new risks
The table below shows common substitution examples in metal, plastics and paint work, and the new risk that must not be overlooked in each. The actual classification of products must be verified from the supplier's SDS.
| Current practice | Candidate | Gain | New risk to watch |
|---|---|---|---|
| Paint containing toluene or xylene | Water-based paint | Highly flammable vapour and solvent exposure are reduced | Allergy warning due to preservatives (H317 or EUH208), equipment corrosion, drying heat |
| Degreasing with trichloroethylene | Aqueous alkaline washing | A carcinogenic (Category 1B) substance is eliminated | Corrosive product (H314), hot water, wet floors |
| Dichloromethane-based paint stripper | Stripper with less volatile solvents | A very volatile substance suspected of causing cancer is removed | Longer dwell time and skin contact; H statements on the new SDS |
| Powder pigment or additive | Granular masterbatch | Dust exposure during weighing and emptying is reduced | Dosing and colour trials |
| Adhesive containing n-hexane | Water-based or hot melt adhesive | A solvent with nervous system effects is removed | Burns and fumes with hot melt |
| Solvent-based mould release spray | Water-based mould release | Flammable aerosol is reduced | Slippery floors, residue on the mould |
The second row of the table shows the nature of substitution well: as a carcinogenic solvent is eliminated, a corrosive product and hot water come into play. This does not make substitution wrong; it simply requires the new risks to be brought under control in the same assessment. You can find the health effects of solvent vapour in our article on solvent vapour exposure.
Switching to water-based paint: technical suitability and trials
Switching to water-based paint is the most widely discussed substitution example in industry, and it also shows why the question of technical suitability comes first. Before switching, look for answers to these questions:
- Surface preparation: Water-based products are more sensitive to oil and dirt; the degreasing step must be reconsidered.
- Drying: Drying time depends on temperature and humidity. If additional heating is needed in the booth or oven, energy and hot surface risks are assessed.
- Equipment: The suitability of the pump, hoses and spray gun for a water-based product is confirmed with the supplier.
- Storage: Water-based products must be protected from freezing; store conditions are arranged accordingly.
- Quality: Adhesion, film thickness and appearance tests are carried out according to customer requirements.
Choose a line or product group for the trial and set its duration at the outset. We plan workplace measurements before and after the trial with authorised laboratories, so the change in exposure can be seen in figures. Throughout the trial, painters' skin, eye and headache complaints are monitored with the workplace physician; quality and scrap data are shared with production. For booth layout and painters' other risks, see our article on paint booth and painter risks.
Is a "solvent-free product" always safer?
No. The expression solvent-free product only means that it contains no volatile solvent; it does not show that the product is non-hazardous. Common situations:
- Two-component epoxy and polyurethane systems: They may be solvent-free, but the amines or isocyanates in the hardener may be skin or respiratory sensitisers. A sensitised worker can react even at very low exposure.
- "Natural" solvents: Solvents such as d-limonene, obtained from orange peel, are classified as flammable liquids and skin sensitisers.
- Hot melt products: There is no solvent, but molten material means burns and fumes.
Decision and record: what should a substitution file contain?
The substitution decision should be in writing, both when substitution is made and when it cannot be. A short substitution file contains:
- The name, place of use, quantity and SDS of the current product
- The candidates assessed and their SDSs
- A hazard and exposure comparison table
- The trial plan, duration and results (measurements, health complaints, quality)
- The decision and its rationale; if no substitution was made, the technical reason
- Implementation date and the documents updated
Example record: At a plastic injection moulding plant, operators spray a solvent-based mould release containing a flammable aerosol onto moulds. Two water-based candidates are selected in the assessment; because one's SDS contains a skin sensitiser statement, the other is taken to trial. In a trial on a single group of machines, part quality does not change, but the floor in front of the machines becomes slippery. The decision is recorded as "substitute"; drip trays, floor cleaning frequency and removal of the aerosol cans from the store are added as additional measures. The record shows not only the decision but also why it was made.
If substitution is not possible, the file does not close there. The order in the Regulation continues: closed systems and process measures, extraction at source, work organisation and, lastly, personal protection. Because new products come onto the market, review the decision every time the risk assessment is renewed; you can track the dates with the OHS calendar tool.
At paint, plastics and metalworking plants in Bursa and the surrounding provinces, Bursa Sistemer carries out substitution assessments together with SDS comparisons and trial plans as part of its risk assessment service. For other topics in the sector, see our chemicals and plastics page.
Frequently Asked Questions
Is chemical substitution mandatory?
The Chemical Substances Regulation places substitution at the top of the order of measures: where technically possible, a less hazardous chemical is used instead of a hazardous one. If this is not possible because of the nature of the work, the reason is written in the risk assessment and the next measures in the order are applied.
Is water-based paint completely safe?
No, but in most cases it markedly reduces flammable vapour and solvent exposure. Preservatives in some products can cause allergies; the new product's SDS should be examined and the switch confirmed by a trial.
Must the risk assessment be renewed after substitution?
Yes. A change in the substance used is one of the situations requiring the risk assessment to be renewed regardless of its validity period. Training, PPE selection, the inventory and labels are also updated accordingly.
How long should a substitution trial last?
The legislation sets no period. The trial should be long enough to see quality results, process steps such as drying, and workers' complaints, and its start and end dates should be set in advance.
A risk assessment that identifies and scores hazards on site, links each measure to an owner and a date, and has a clear renewal schedule.
Bursa SİSTEMER OSGB Technical Team — written from the field experience of our OHS specialists and workplace physicians. Legal information is valid as of the publication/update date; contact us for an assessment specific to your business.