Benzene
CAS 71-43-2
CarcSk
8h TWA
1 ppm · 3.25 mg/m³
Cross-ref: BMGV none; sprint5 surveillance + sprint13 leukaemia
🇬🇧 United Kingdom 🇬🇧 United Kingdom · HSE EH40/2005 · COSHH reg 7 · ALARP for carcinogens
WELs + BMGVs (EH40/2005)
Workplace Exposure Limits (WELs) — legally binding under COSHH reg 7, expressed as 8-hour TWA and 15-min STEL. Biological Monitoring Guidance Values (BMGVs) — non-binding review levels (Table 2). UK units: µmol/mol or mmol/mol creatinine + breath CO.
23 WELs listed 14 BMGVs EH40 2018/2020 ed.
ALARP — for carcinogens, mutagens, asthmagens
For substances marked Carc, Muta, or any asthmagen (notably RCS, benzene, MbOCA, formaldehyde, isocyanates), the duty is to reduce exposure as low as reasonably practicable — beyond simply meeting the numeric WEL. ALARP applies even if you are well below the limit.
Separate regimes — not in EH40
- Lead — Control of Lead at Work Regs 2002 (CLAW), Appointed Doctor scheme, blood lead suspension 30/50/60 µg/dL (women repro / under 18 / others).
- Asbestos — Control of Asbestos Regs 2012 (CAR), control limit 0.1 f/cm³ over 4h, medical surveillance for licensed work.
Workplace Exposure Limits (WELs) — binding under COSHH
Formaldehyde
CAS 50-00-0
Carc 1BMuta 2
Historic (pre-CMD3)
2 ppm
EU CMD3
0.3 ppm 8h · 0.6 ppm STEL
Verification flag: FLAGGED — secondary sources state EU CMD3 0.3/0.6 ppm + 5-yr healthcare/funeral 0.5 ppm transition adopted in UK; v1.1 'no change needed' claim was hallucinated not verified. FOM reviewer: confirm against CURRENT EH40 PDF directly.
Cross-ref: sprint13 occupational asthma + nasopharyngeal
Respirable crystalline silica (RCS)
CAS 14808-60-7
Carc (classified 2020)
8h TWA
0.1 mg/m³
UK WEL 0.1 mg/m3 — HALF as strict as US OSHA 0.05 mg/m3 (50 µg/m3). Carcinogen → ALARP. Control of dust crucial.
Cross-ref: sprint14g silica/COPD + sprint13 silicosis
Toluene
CAS 108-88-3
Sk
8h TWA
50 ppm · 191 mg/m³
15-min STEL
100 ppm · 384 mg/m³
Cross-ref: BMGV: o-cresol/hippuric (see Table 2 below)
Chromium metal, Cr(II) and Cr(III) compounds (as Cr)
CAS 7440-47-3
8h TWA
0.5 mg/m³
Cr(VI) hexavalent has separate stricter limits — see uk-wel-005b. Cr(VI) carcinogenic.
Cross-ref: uk-wel-005b Cr(VI); uk-bmgv chromium VI
Chromium (VI) compounds (hexavalent)
Carc
Non-process generated
0.01 mg/m³
Process generated
0.025 mg/m³
Reduced from 0.05 mg/m³ on 17 Jan 2020. Process-generated (e.g. welding fume): 0.025 mg/m³. Non-process: 0.010 mg/m³. Verified sanity-check 2026-05-30.
Cross-ref: uk-bmgv chromium VI (10 μmol/mol creatinine post-shift)
MbOCA (2,2'-dichloro-4,4'-methylenedianiline)
CAS 101-14-4
CarcSkBMGV
8h TWA
0.005 mg/m³
Cross-ref: uk-bmgv MbOCA (15 μmol/mol creatinine)
Dust — general (no specific WEL assigned)
Inhalable
10 mg/m³
Respirable
4 mg/m³
COSHH 'substance hazardous to health' control benchmark for dusts without a specific WEL: inhalable 10 mg/m3, respirable 4 mg/m3 (8-hr TWA)
Mercury and divalent inorganic compounds (as Hg)
CAS 7439-97-6
Sk
8h TWA
0.02 mg/m³
Cross-ref: uk-bmgv mercury (sprint19 + sprint20)
Cadmium oxide fume (as Cd)
CAS 1306-19-0
Carc
8h TWA
0.025 mg/m³
Cross-ref: uk-bmgv-013 not applicable
Cadmium sulphide + cadmium sulphide pigments (respirable dust as Cd)
Carc
8h TWA
0.03 mg/m³
Ammonia (anhydrous)
CAS 7664-41-7
8h TWA
25 ppm · 18 mg/m³
15-min STEL
35 ppm · 25 mg/m³
Verify against current EH40 PDF before clinical use.
Carbon monoxide
CAS 630-08-0
8h TWA
20 ppm · 23 mg/m³
15-min STEL
100 ppm · 117 mg/m³
Revised down from 30 ppm to 20 ppm 8h TWA from 17 January 2020 (CMD3). BMGV measured in end-tidal breath (sprint19 Table 2). Verify against current EH40 PDF before clinical use.
Hydrogen sulphide
CAS 7783-06-4
Sk
8h TWA
5 ppm · 7 mg/m³
15-min STEL
10 ppm · 14 mg/m³
Olfactory fatigue: smell unreliable above ~100 ppm. Verify against current EH40 PDF before clinical use.
Glutaraldehyde
CAS 111-30-8
Sen
8h TWA
0.05 ppm · 0.2 mg/m³
15-min STEL
0.05 ppm · 0.2 mg/m³
Asthmagen and skin/respiratory sensitiser. UK healthcare endoscope decontamination has largely substituted to peracetic acid / ortho-phthalaldehyde. Verify against current EH40 PDF before clinical use.
Isocyanates (all, as -NCO)
SenCarc
8h TWA
0.02 mg/m³
Covers TDI, MDI, HDI, IPDI. Leading UK cause of occupational asthma (PD D7). BMGV: 1 µmol isocyanate-derived diamine/mol creatinine (sprint19 Table 2). REACH restriction on diisocyanates training in force since 24 Aug 2023. Verify against current EH40 PDF before clinical use.
Methanol
CAS 67-56-1
Sk
8h TWA
200 ppm · 266 mg/m³
15-min STEL
250 ppm · 333 mg/m³
Skin absorption significant. Verify against current EH40 PDF before clinical use.
Sulphuric acid (mist)
CAS 7664-93-9
Carc
8h TWA
0.05 mg/m³
Strong inorganic acid mists — IARC 1 carcinogen (larynx). ALARP duty applies. Verify against current EH40 PDF before clinical use.
Trichloroethylene
CAS 79-01-6
CarcSk
8h TWA
100 ppm · 550 mg/m³
15-min STEL
150 ppm · 820 mg/m³
REACH Annex XVII restriction — authorisation required for industrial use. Verify against current EH40 PDF before clinical use.
Tetrachloroethylene (perchloroethylene)
CAS 127-18-4
Sk
8h TWA
50 ppm · 345 mg/m³
15-min STEL
100 ppm · 689 mg/m³
Dry-cleaning solvent. Verify against current EH40 PDF before clinical use.
n-Hexane
CAS 110-54-3
Sk
8h TWA
20 ppm · 72 mg/m³
Peripheral neuropathy via 2,5-hexanedione metabolite (BMGV exists in EH40 Table 2). Verify against current EH40 PDF before clinical use.
Nitrogen dioxide
CAS 10102-44-0
8h TWA
0.5 ppm · 0.96 mg/m³
15-min STEL
1 ppm · 1.91 mg/m³
Revised in 2018 (CMD3 transposition). Combustion-related (welding, diesel exhaust, mining). Verify against current EH40 PDF before clinical use.
Ozone
CAS 10028-15-6
8h TWA
0.2 ppm · 0.4 mg/m³
15-min STEL
0.2 ppm · 0.4 mg/m³
Welding (esp. MIG/TIG aluminium), photocopying, water treatment. Verify against current EH40 PDF before clinical use.
Biological Monitoring Guidance Values (BMGVs) — non-binding, EH40 Table 2
Set at the 90th percentile of good-practice workplaces. Exceeding does not breach the law, but triggers investigation. UK units differ from US/ES — convert carefully.
Butan-2-one (MEK)
70 μmol butan-2-one/L in urine
Sampling: Post shift
2-Butoxyethanol
240 mmol butoxyacetic acid/mol creatinine in urine
Sampling: Post shift
Carbon monoxide
30 ppm carbon monoxide in end-tidal breath
Sampling: Post shift
UK uses end-tidal breath CO, not US COHb % — different matrix
Chromium VI
10 μmol chromium/mol creatinine in urine
Sampling: Post shift
Chlorobenzene
5 mmol 4-chlorocatechol/mol creatinine in urine
Sampling: Post shift
Cyclohexanone
2 mmol cyclohexanol/mol creatinine in urine
Sampling: Post shift
Dichloromethane (DCM)
30 ppm carbon monoxide in end-tidal breath
Sampling: Post shift
DCM metabolises to CO — measured as breath CO
N,N-Dimethylacetamide
100 mmol N-methylacetamide/mol creatinine in urine
Sampling: Post shift
Glycerol trinitrate (nitroglycerin)
15 μmol total nitroglycols/mol creatinine in urine
Sampling: End of period of exposure
Isocyanates (HDI, IPDI, TDI, MDI)
1 μmol isocyanate-derived diamine/mol creatinine in urine
Sampling: End of period of exposure
Cross-ref: sprint13 occupational asthma — isocyanates leading cause UK
Lindane (γ-HCH)
35 nmol/L (10 μg/L) lindane in whole blood (≈70 nmol/L in plasma)
Sampling: Random
MbOCA (2,2'-dichloro-4,4'-methylenedianiline)
15 μmol total MbOCA/mol creatinine in urine
Sampling: Post shift
4,4'-Methylenedianiline (MDA)
1 µmol MDA/mol creatinine in urine
Sampling: Post shift
MDA = urinary biomarker of MDI (methylene diphenyl diisocyanate) exposure when metabolites are chemically hydrolysed
Cross-ref: sprint14g isocyanate asthma; sprint13 PD D7
Pentachlorophenol (PCP)
see EH40 Table 2
UK ↔ US ↔ ES structural differences
UK
WELs (binding, COSHH) + BMGVs (non-binding, EH40 Table 2) in μmol/mol or mmol/mol creatinine + breath CO; carcinogens to ALARP
US
OSHA PELs (binding) + NIOSH RELs (advisory) + ACGIH BEIs (copyright); biomonitoring in µg/g creatinine
ES
INSST VLA (ambiental) + VLB (biológico) in µg/g creatinine; RD 374/2001; INSST adopts ACGIH-derived values
Key structural notes
- ▸WELs are LEGALLY BINDING under COSHH; BMGVs are NOT binding (review/investigation levels)
- ▸UK biomonitoring units: μmol/mol or mmol/mol creatinine, or analyte in breath — convert carefully when mapping to US/ES µg/g
- ▸RCS UK WEL 0.1 mg/m3 is LESS strict than US OSHA 0.05 mg/m3 — flag for risk assessment
- ▸Lead + asbestos NOT in EH40 WEL list — separate regs (CLAW/CAR)
- ▸Carcinogens (benzene, RCS, MbOCA, formaldehyde): ALARP duty beyond the numeric WEL
To re-verify against current EH40 edition
- ●Mercury + cadmium WEL exact values (not fully captured in extraction)
- ●Confirm against CURRENT EH40 edition (2020+) for carcinogen WEL updates
- ●Formaldehyde: EU CMD later set 0.3 ppm — confirm whether current UK edition adopted lower value
Devolved implementation
EH40/COSHH apply across Great Britain (HSE) and Northern Ireland (HSENI publishes EH40 in parallel). GB-wide — no nation-specific WEL divergence.