3-step guide to chemical substitution

Substitution is rarely only about switching one chemical for another. A successful substitution requires an in-depth analysis to make sure that all possible solutions are thought through. Depending on the situation, chemical substitution can be an easy process or prove to be a more difficult task. But in the end, it will be worth it because both your product and your working conditions will be safer.

To give you some guidance on the issue, we’ve simplified the process and boiled it down into a 3-step guide to steer you in the right direction and help you avoid pitfalls along the way.

1. Use, function and need

The very first step in a substitution process is, of course, to identify the chemical that needs to be removed. After that, it’s important to understand what function it has in the production process or what properties it gives the final product. In best case it may not be needed at all, or it can easily be swapped with only a slight modification of the process.

Let’s look at the use of phthalates in PVC printing on textiles as an example. The function of the phthalate, in this case, is to make the PVC plastic soft. If you only consider the function you may find an alternative non-phthalate plasticiser to substitute the phthalate for.

Looking at the use – which is PVC for textile printing – you may consider changing to another type of printing paste that does not require plasticisers, such as polyurethane or silicone.

The “need” in this case is to produce clothes that are attractive. This can also be achieved by means other than printing, such as embroidery.

Depending on the question you ask, you might end up with several possible alternatives. Our recommendation is to take a broad perspective and look at all the possibilities so that you have as many solutions as possible at this stage.

Before moving on to assessing and comparing alternatives it is important to think through what you want from an alternative. What would you like to achieve in terms of hazard profile and functionality: Is there a cost limit? How urgent is the substitution? Are there already legal requirements in place or do you have time to wait for an alternative that is currently at the research stage?

2. Evaluate and compare alternatives

After you have defined the criteria and you have found a couple alternatives that match these, you need evaluate and compare the alternatives.

Assessing alternatives is about making sure you choose the best of the available alternatives, given the criteria you have set, and taking extra care not to introduce other hazardous chemicals in the process. The following aspects can be considered when assessing alternatives:

• Hazard assessment
• Functionality of alternatives
• Availability of alternatives
• Costs
• Changes to processes
• Life-cycle considerations: energy, waste/discharge, CO²emissions, etc.

If the aim of substitution is to reduce hazardous chemicals, then the hazard assessment is where you should start. Once you are sure you have one or more alternatives that are less hazardous than the substance you are substituting, you can look at the other aspects.

Assessment of alternatives is widely discussed, and new and better methodologies are under development. Some regulations – such as the European chemicals regulation REACH – require that alternatives are assessed before hazardous chemicals can be routinely used. There are a number of available methods, some are simple and require only information from Material Safety Datasheets, while others require information from scientific publications or even re-testing of chemicals.

The OECD has worked with stakeholders to create a toolbox that is designed to help you choose a method of alternatives assessment that suits your competence and requirements.

The most comprehensive method for assessing alternatives is called the GreenScreen for safer chemicals. This was developed by the organisation Clean Production Action and provides a rigorous comparative hazard assessment based on 18 different hazardous endpoints. Chemicals are benchmarked on a scale of 1 to 4, which makes the comparison visible and easy. The GreenScreen is also a part of some US regulatory initiatives and standards for the building and electronics sector.

One common problem when assessing alternatives is the lack of data, especially for newer chemicals. For chemicals where little or no data is available, one can estimate hazardous properties based on chemical structure. The most popular methodology for this is called q-SAR, but this requires chemicals expertise and training.

For use with the SIN List, ChemSec has developed a tool called SINimilarity. This online tool gives you the opportunity to type in a chemical’s CAS number and find out if it is structurally similar to any of the substances on the SIN List. If so, it is likely that the chemical has similar problematic properties.

3. Pilot test and implementation

Even after thorough assessments, evaluations and comparisons of alternatives, certain things may occur that you could not foresee. It is therefore always wise to do a practical pilot test before implementing full-scale substitution.

But if all works well with the pilot test, you are good to go!

However, be aware that you might not yet have found the final and ultimate solution. Substitution is an ongoing process, since new scientific findings and regulations may turn up. But having done a proper alternative assessment, you are prepared in the best possible way for this.

Good luck, and don’t forget to share your substitution success stories with us!