WEL Substance Profile

Styrene — Workplace Exposure Limit Change

CAS: 100-42-5 | Notation: Probable carcinogen (IARC Group 2A), ototoxic

Current WES

ppm

New WEL (Dec 2026)

ppm

Change

-60%

reduction

Health Effects

Styrene was reclassified as a Group 2A probable carcinogen by IARC in 2019, based on limited evidence of lymphohaematopoietic malignancies in humans and sufficient evidence of tumours in experimental animals. Styrene is also ototoxic, meaning it damages hearing through a mechanism independent of noise exposure. Workers exposed to both styrene and noise experience synergistic hearing loss greater than either exposure would cause alone. Acute exposure causes central nervous system depression with symptoms including headache, fatigue, dizziness, and impaired concentration. Chronic exposure at levels below the current WES has been associated with colour vision impairment, decreased reaction time, and neurobehavioural effects. Respiratory irritation occurs at concentrations above 20 ppm, and dermatitis from direct skin contact with liquid styrene is common in laminating and moulding operations.

Where Exposure Occurs

Fibreglass reinforced plastics (FRP) laminating and mouldingPolystyrene and ABS plastics manufacturingFlexographic and screen printing with styrene-containing inksBoat building and marine manufacturingBathtub and shower enclosure manufacturingComposite repair operations in automotive and aerospace

What to Do Now

01Conduct personal air monitoring for styrene at all FRP laminating, moulding, printing, and plastics manufacturing workstations. Use charcoal tube sampling with GC analysis for accurate time-weighted average measurements. Real-time photoionisation detectors can supplement tube sampling for identifying peak exposure tasks during open-mould laminating and resin mixing.

02Upgrade ventilation in laminating and moulding areas. Downdraft tables and cross-draft ventilation systems positioned to draw styrene vapour away from the worker's breathing zone are effective engineering controls. For open-mould FRP processes, local exhaust ventilation must be supplemented with general dilution ventilation to maintain ambient levels below the WEL throughout the workspace.

03Evaluate process changes including transition from open-mould to closed-mould processes such as resin transfer moulding, vacuum infusion, or light resin transfer moulding. These processes reduce styrene emissions by 80 to 95 per cent compared to hand lay-up and spray-up techniques. Low-styrene and styrene-free resin formulations are available for many applications.

04Implement combined health surveillance for both styrene exposure and noise exposure, recognising the synergistic ototoxic interaction. The program should include audiometric testing, urinary mandelic acid biomonitoring for styrene metabolites, colour vision testing, and neurobehavioural assessment. Workers exposed to both styrene and noise above action levels should receive audiometric testing at six-month intervals.

05Review noise and styrene co-exposure management. The ototoxic effect of styrene means that hearing conservation programs based solely on noise levels will underprotect workers who are also exposed to styrene. Combined exposure risk assessment should inform hearing protection selection, noise reduction targets, and health surveillance frequency.

Monitoring Method

Personal air sampling using a calibrated pump at 0.05 to 0.2 L/min with coconut shell charcoal tubes (100/50 mg sections). Desorption with carbon disulphide and analysis by gas chromatography with flame ionisation detection following NIOSH Method 1501 or AS 2986. Biological monitoring of urinary mandelic acid and phenylglyoxylic acid at end of shift provides a complementary measure of absorbed dose.

Affected Industries

Printing →Auto Body →

Control Styrene Below the New 20 ppm Limit

EHS Atlas tracks styrene and noise co-exposure data, manages combined health surveillance programs, and documents ventilation system performance for FRP and printing operations.