Look up an exposure limit by CAS number
Search by CAS number or substance name and see at once whether a statutory limit applies — Dutch, European and international
A CAS number, with or without hyphens, or part of the substance name.
What you see here
A statutory limit comes from annex XIII of the Dutch Arbeidsomstandighedenregeling and binds employers in the Netherlands. It is shown here with its value, because it is public law.
Where there is no Dutch statutory value, we show what foreign regulators set: Germany, the United Kingdom, Belgium, France and others. Those do not apply in the Netherlands, but they are useful as comparison when the Dutch regulator is silent. Every value is labelled with its regulator and whether it binds.
Values from the Gezondheidsraad and the German DFG are recommendations, not law, and are marked as such. For the concepts themselves, TWA, STEL and ceiling, see what an exposure limit is.
Where no regulator has set a value, we show the DNEL: a derivation a REACH registrant made for their own dossier, which ECHA publishes. That is not an exposure limit, because nobody set it and nobody enforces it. It is often the only thing to go on, so it is shown and marked separately. The difference is set out in DNEL vs OEL.
An example
Toluene, CAS 108-88-3, returns three values. The Dutch statutory 8-hour TWA is 150 mg/m³ and the short-term value 384 mg/m³. Both come from annex XIII and so bind a Dutch employer. Alongside them sits a US ceiling value of 1147 mg/m³, which does not apply here and is marked as non-binding. For toluene DOHSBase holds a further 27 regulator values and 12 biological limit values, which are in DOHSBase Online.
Why some values are not shown here
DOHSBase derives an exposure limit for many substances itself, from a related substance or from the classification. That is the work the subscription pays for, and those values are not shown here. We do say that we hold them and what they were derived from, so you know there is more than this page shows.
DNEL detail, biological limit values, measurement methods and historical values are in DOHSBase Online rather than here.
For developers and AI assistants
The same data is available as an open API at data.dohsbase.nl. No key, no account.
curl https://data.dohsbase.nl/v1/substance/108-88-3
GET /v1/substance/{cas} returns the values for a substance, GET /v1/search?q= searches by name. The origin field says who set the value: regulatory for a regulator, dnel for a REACH registrant. Read origin, do not infer it from binding. A DNEL and a British WEL are both non-binding, and they are not the same kind of value: nobody set the DNEL.
The annex XIII values are public law and free to use. Beyond those we ask for attribution to DOHSBase; the response carries an attribution field for that. A limit of 20 requests per 10 seconds per IP applies.
As an MCP server
If you work with an AI assistant, you can connect DOHSBase to it directly. The MCP server runs at mcp.dohsbase.nl, with no key and no account.
claude mcp add --transport http dohsbase https://mcp.dohsbase.nl/mcp
There are two tools. search_substances finds a substance by name, synonym, CAS number, EC number or molecular formula; lookup_occupational_exposure_limit then returns the exposure limits for that CAS number. The tool descriptions carry the same warnings as this page, so an assistant does not report a DNEL as a statutory limit.
Further reading
- What is an exposure limit? — TWA, STEL, ceiling and biological limit values.
- DNEL vs OEL — why a DNEL is not an exposure limit.
- EN 689 compliance assessment — testing measurements against the limit you find here.
- DOHSBase Online — the database itself, with everything this page does not show.