Hazards + exposures
Fifty-four chemicals on the new national list have no exposure number, and that is the point
When workplace exposure limits take legal effect on
1 December 2026, most entries on the list will carry a concentration you
can measure against. Fifty-four will not. They have no eight-hour average,
no short-term limit and no peak limitation, and each is flagged with the register's note
k, which Safe Work Australia defines as a non-threshold genotoxic
carcinogen
. The absence is the finding: for these substances no safe airborne
concentration has been identified, so there is no number to comply with.
Twenty-four of the fifty-four are hexavalent chromium species.
We have been reading the new Hazardous Chemical Information System since Safe Work Australia published it on 4 August, most recently to confirm that the nine chemicals ministers deadlocked on carry their old values. This is a different question, and it came out of reading the whole approved list rather than a shortlist.
The register holds 1,173 approved exposure limit records, covering 1,113 distinct substances. The gap between those two numbers is substances that carry more than one limit because they take more than one physical form, which we have written about before. This piece is about a different gap: records with no value in them at all.
What note k means
Fifty-four approved records carry no concentration of any kind. Every one of them is
flagged with the note k, and the register's own reference page defines that
note in a single sentence: This chemical is a non-threshold genotoxic carcinogen (NTGC)
.
A non-threshold carcinogen is one for which no exposure level has been identified below which the cancer risk is considered absent. If there is no threshold, there is no number to set, and the blank in the register is a statement rather than an omission.
This matters practically, and in a direction people get backwards. A duty-holder who
searches the register for one of these substances, finds no limit, and concludes the
substance is therefore unregulated or low-risk has drawn precisely the wrong inference. Safe
Work Australia states the general principle plainly on the same reference page: A substance
should not be assumed to be safe just because it does not have an exposure limit.
Nearly half the list is one family of chemicals
Twenty-four of the fifty-four are hexavalent chromium compounds: chromic acid and its salts, the chromates of lead, zinc, strontium, barium, calcium, magnesium and potassium, sodium and potassium dichromate, chromium (VI) trioxide, and the general class entries for chromium (VI) compounds.
That concentration matters because of who meets them. Hexavalent chromium is generated in stainless steel welding and produced in chrome plating, and it is present in some primers and coatings. These are not exotic laboratory reagents; they are the everyday output of common trades. The other thirty include vinyl chloride monomer, ethylene oxide, 1,3-butadiene, acrylamide, benzidine, hydrazine and coal tar pitch volatiles.
The full list
Every approved record in the new register that carries no time weighted average, short-term exposure limit or peak limitation, and is flagged note k. Read on 6 August 2026. Names and CAS numbers are the register's own, including the entries it records as chemical classes rather than single substances, which is why some carry no CAS.
| Substance, as the register names it | CAS |
|---|---|
| (bis)chloromethyl ether | 542-88-1 |
| 1,2-Dibromoethane | 106-93-4 |
| 1,3-butadiene | 106-99-0 |
| 3,3'-Dichlorobenzidine | 91-94-1 |
| 4,4’-Methylene bis(2-chloroaniline) | 101-14-4 |
| Acrylamide | 79-06-1 |
| Acrylonitrile | 107-13-1 |
| Allyl chloride | 107-05-1 |
| Allyl glycidyl ether | 106-92-3 |
| Anisidine | 29191-52-4 |
| Barium chromate | 10294-40-3 |
| Benzidine | 92-87-5 |
| beta-Chloroprene | 126-99-8 |
| Calcium chromate | 13765-19-0 |
| Catechol | 120-80-9 |
| Chromic acid (H2Cr2O7), diammonium salt | 7789-09-5 |
| Chromic acid (H2Cr2O7), disodium salt, dihydrate | 7789-12-0 |
| Chromic acid (H2CrO4) | 7738-94-5 |
| Chromic acid (H2CrO4), chromium(3+) salt (3:2) | 24613-89-6 |
| Chromic acid (H2CrO4), diammonium salt | 7788-98-9 |
| Chromic acid (H2CrO4), dilithium salt | 14307-35-8 |
| Chromic acid (H2CrO4), disodium salt, tetrahydrate | 10034-82-9 |
| Chromium (VI) compounds | not assigned |
| Chromium (VI) compounds, with the exception of barium chromate and of compounds specified elsewhere in this database | not assigned |
| Chromium (VI) trioxide | 1333-82-0 |
| Chromium, dichlorodioxo- | 14977-61-8 |
| Coal tar pitch volatiles (as benzene solubles) | 65996-93-2 |
| Diethyl sulfate | 64-67-5 |
| Dimethyl sulfate | 77-78-1 |
| Dimethylcarbamoyl chloride | 79-44-7 |
| Dinitrotoluene | 25321-14-6 |
| Ethylene dichloride | 107-06-2 |
| Ethylene oxide | 75-21-8 |
| Ethylenimine | 151-56-4 |
| Hydrazine | 302-01-2 |
| Iron (III) chromate | 10294-52-7 |
| Lead chromate | 7758-97-6 |
| Lead chromate oxide (Pb2(CrO4)O) | 18454-12-1 |
| Magnesium chromate | 13423-61-5 |
| o-Anisidine | 90-04-0 |
| p-Anisidine | 104-94-9 |
| Polycyclic aromatic hydrocarbon (PAH) mixture when containing benzo[a]pyrene | 50-32-8 |
| Potassium chromate | 7789-00-6 |
| Potassium dichromate | 7778-50-9 |
| Propane sultone | 1120-71-4 |
| Silicic acid, chromium lead salt | 11113-70-5 |
| Sodium chromate | 7775-11-3 |
| Sodium dichromate | 10588-01-9 |
| Strontium chromate | 7789-06-2 |
| Tetranitromethane | 509-14-8 |
| Urethane | 51-79-6 |
| Vinyl bromide | 593-60-2 |
| Vinyl chloride, monomer | 75-01-4 |
| Zinc chromate | 13530-65-9 |
Three more records have no number and no explanation
Three further approved records carry no value and no note k either: 2-Nitrotoluene (CAS 88-72-2), fused silica (CAS 60676-86-0) and subtilisins, the proteolytic enzymes (CAS 1395-21-7), the last of which carries the advisory notation RSEN.
We are not calling these an error. A blank with no note may be deliberate for reasons the register does not surface, and we have not asked Safe Work Australia. We are recording them because a reader looking up any of the three will find nothing and deserves to know that the nothing is not explained, unlike the fifty-four above where it is.
Our view, labelled as such
The register handles this well. Flagging a blank with a note that says why is better design than leaving a reader to guess, and better than inventing a number nobody can defend.
The risk sits in how the information travels. A search interface returns "no exposure limit" the same way whether the reason is that no safe level exists or that nobody has assessed the substance yet, and those are opposite meanings. With six weeks until these limits carry legal force, anyone building a chemical register, an air monitoring plan or a training package from this data should be reading the note field, not just the number field.
How we checked this
We read every approved workplace exposure limit record in the new register, 1,173 of them, and examined the limit values held on each. The 54 reported here are those with no time weighted average, no short-term exposure limit and no peak limitation, cross-checked against the note field, which carries k on all 54. The definition of note k, the caution about substances without an exposure limit, and the 1 December 2026 commencement are quoted from Safe Work Australia's own reference pages for the register. The count of hexavalent chromium species is ours, taken by reading the 54 names.
What we have not done. We have not put any of this to Safe Work Australia, and we are not reporting a defect: for the 54, the blank is explained by the note and appears deliberate. We have not read the per-chemical evaluation reports the register references, so we cannot say why any individual substance was assessed as non-threshold. We have not checked whether these same substances carried numbers under the outgoing exposure standards, so nothing here says the position has changed. The three unexplained records are reported as unexplained, not as errors. This is general information about what the register states, not advice on compliance for any workplace, and the limits take legal effect on 1 December 2026 rather than today.
Sources
- Safe Work Australia, Hazardous Chemical Information System (the new HCIS, published 4 August 2026; all approved workplace exposure limit records queried directly and read 6 August 2026): the 1,173 approved records and 1,113 distinct substances, the 54 records carrying no limit value, their names, CAS numbers and note flags, and the three further records with neither value nor note.
- Safe Work Australia, Workplace exposure limits reference (read 6 August 2026): the definition of note k as a non-threshold genotoxic carcinogen, the caution that a substance should not be assumed safe merely because it has no exposure limit, the three types of exposure limit, and that the limits come into effect from 1 December 2026.
- Australian Workplace Safety, the nine deadlocked chemicals checked against the same register: our earlier reading of the approved records, and the multiple-records-per-substance point referred to above.