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, you still see what exists: which regulator sets a value, for which reference period, and how many values we hold for that substance. The value itself is in DOHSBase Online. That applies to foreign regulators, to Gezondheidsraad and German DFG recommendations, and to DNELs.
A DNEL is a derivation a REACH registrant made for their own dossier, which ECHA publishes. It is not an exposure limit, because nobody set it and nobody enforces it. You see here that we hold one; the difference is set out in DNEL vs OEL. For the concepts themselves, TWA, STEL and ceiling, see what an exposure limit is.
Where nothing is shown, DOHSBase holds no exposure limit for that substance. That is not the same as exposure being safe: most substances have no exposure limit anywhere, including harmful ones.
An example
Toluene, CAS 108-88-3. The Dutch statutory 8-hour TWA is 150 mg/m³ and the short-term value 384 mg/m³, both from annex XIII and so binding on a Dutch employer. Alongside them you see that the United States sets a ceiling value, without the figure. For toluene DOHSBase holds 27 regulator values and 12 biological limit values in total, 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.
The values themselves, including foreign regulator values and DNELs, sit alongside the biological limit values, measurement methods and historical values in DOHSBase Online.
For developers and AI assistants
The same data is available as an open API at data.dohsbase.nl.
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. Only an annex XIII value (binding: true) carries a figure; everything else comes back with withheld: true and value: null, naming the regulator, period and unit. withheld means a limit exists, not that one is missing.
The annex XIII values are public law and free to use. Beyond those we ask for attribution; the response carries an attribution field. A limit of 20 requests per 10 seconds per IP applies.
As an MCP server
claude mcp add --transport http dohsbase https://mcp.dohsbase.nl/mcp
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.
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.