SINimilarity shows if a substance is structurally similar to a substance on the SIN List, which in turn indicates similar problematic properties. The aim is to help avoid substituting one problematic chemical with another.
SINimilarity compares a substance with chemicals on the SIN List, a globally used database with chemicals that have been identified by ChemSec as Substances of Very High Concern (SVHC) based on the criteria established by the European Union chemicals regulation REACH. More than 130,000 chemicals can be investigated by name, CAS number or InChi(key).
How to use SINimilarity
The SINimilarity tool has a background database of more than 130,000 identified chemical structures available. This means that you can search for any of those structures by name, CAS number or InChi(key) and see if the substance you are looking for is similar to a substance on the SIN List.
SINimilarity looks for two things in the molecular structure. And all substances found in SINimilarity have at least one part in common with substances on the SIN list:
- The overall structural resemblance to SIN List substances. You will see which, if any, substances on the SIN List that has 70% or more structural resemblance to your substance. Matches with the SIN List show in yellow colour. You can also click to view the corresponding substances in the SIN database.
- Specific elements of importance to the toxicity. These elements are the same as the ones used to group the SIN List. If your substance contains this structural element, you will see the name of the corresponding SIN group. Matches with groups on the SIN List will also show in yellow colour.
If a substance turns up in orange, it will contain both an overall structural similarity with at least one SIN substance AND also belong to at least one SIN group.
How did we create the SINimilarity database?
As a baseline and a starting point, all substances on the SIN list were used. They were then divided into groups based on the structure of the substances and a so called “digital fingerprint” was created for each substance, whenever possible.
To identify similar substances, we used a database with 13 million unique substances which are commercially available “off the shelf”. A tailor-made search engine used the “digital finger prints” for all SIN substances and processed them one-by-one to identify all substances with more than 70% overall resemblance to every SIN substance.
After this individual substance identification, we performed a similar process to identify all group members containing the specific structural elements identified for each individual SIN-group. All these substances were combined in the SINimilarity database and were also connected to the SIN List to allow cross referencing from individual SIN substances and SIN groups towards SINimilarity.
How to interpret the result?
SINimilarity provides a first good indication and can be helpful as a first screening tool. An answer from SINimilarity, indicating similar structure and/or grouping, is a very good reason to ask for more information; given the structural similarity, have the corresponding hazardous properties been carefully investigated?
If a substance both has the similar structure and the structural element there is a good reason to proceed with additional caution.
If you have only either resemblance or the structural element, the result is more ambiguous to interpret. A substance with similar structure, but without the specific structural element could, after careful investigation, turn out to be a functional alternative to a known hazardous chemical.
Please note that SINimilarity builds on structural similarity only. To verify potential hazardous properties, further evaluation is needed. If a chemical has no similarity to SIN chemicals it can still have hazardous properties.
SINimilarity is based on the division of the SIN List into 15 main groups, which in turn might have more detailed sub-groups. The base for the grouping is specific molecular structural elements, which have been identified to be important for the toxicity of the substance.
Some chemicals on the SIN List belong to more than one group, as they contain more than one of these structural elements. All substances have been included in at least one group, however for some substances where a common structural element can’t be properly defined they have been placed in the group “Others”.
The SIN groups “Others”, “Petroleum” and “Mineral fibres” contain substances of very complex chemical composition. Substances in these groups are for this reason not used to identify groups in the SINimilarity tool.
Inorganic compounds and many salts are not suited for the similarity methods used in SINimilarity. This is especially true for many compounds in the metal groups. The similarity will be too low to be shown. If the substance contains a group specific metal, it will be identified with regard to that group, which is most often the most useful information on metals.