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Ethylene Oxide Sterilisation SWMS: ALARP Controls for an NTGC Sterilant

Ethylene oxide (EtO, oxirane) is the primary chemical sterilant used in Australian hospitals and medical device manufacturing for heat-sensitive instruments, single-use devices, and implantable products that cannot be processed by steam autoclave or dry heat. EtO is highly effective as a sterilant because it kills bacterial endospores, but the same reactivity that makes it lethal to microorganisms also makes it acutely toxic and genotoxically carcinogenic to humans. The International Agency for Research on Cancer (IARC) classifies ethylene oxide as a Group 1 carcinogen — a confirmed cause of lymphoma, leukaemia, and breast cancer in workers with occupational EtO exposure. On 1 December 2026, Safe Work Australia will reclassify ethylene oxide as a Non-Threshold Genotoxic Carcinogen (NTGC), replacing the existing numerical Workplace Exposure Limit (1 ppm TWA, 5 ppm STEL) with an ALARP requirement. Ethylene oxide is also a reproductive toxin (Category 1B — known human reproductive toxicant), an explosive in air between 3% and 100% by volume, and a severe acute inhalation hazard causing respiratory tract injury, neurological effects, and pulmonary oedema at high concentrations. No other sterilant chemical in routine clinical use combines this toxicological profile with the regulatory burden of the December 2026 NTGC transition. Ethylene oxide sterilisation in Australian hospitals is concentrated in Central Sterilising Supply Departments (CSSD), where EtO is used for flexible endoscopes, ophthalmic instruments, pace-maker leads, and complex surgical instruments that require low-temperature sterilisation. Contract sterilisation facilities serve medical device manufacturers. EtO cylinder handling, chamber loading and unloading, the aeration period, routine maintenance, and filter/absorbent changes are the primary exposure tasks. Each task has a distinct exposure profile — cylinder change presents the highest acute risk; aeration presents a prolonged low-level exposure risk that is easy to underestimate. This SWMS is developed in accordance with the WHS Regulations 2017 (Part 7.1 — Hazardous Chemicals), the revised Workplace Exposure Standards for Airborne Contaminants (SWA, effective 1 December 2026), AS/NZS ISO 11135:2019 (Sterilisation of health-care products — EtO), the Model Code of Practice: Managing Risks of Hazardous Chemicals in the Workplace, and AS/NZS 60079-10-1 (Explosive atmospheres — classification of areas). It must be customised for the specific steriliser model, facility layout, ventilation design, and cylinder storage configuration, and reviewed with workers before use.

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Legal Requirements

regulation

WHS Regulations 2017, Part 7.1 (Hazardous Chemicals), regulations 356–383 (Health monitoring); Workplace Exposure Standards for Airborne Contaminants (SWA, amended effective 1 December 2026): ethylene oxide reclassified as NTGC — ALARP obligation replaces numerical WEL (previously 1 ppm TWA / 5 ppm STEL)

hrcw category

Category 10 — Work involving hazardous material (WHS Regulation r291(1)(j)); ethylene oxide is a Schedule 10 hazardous chemical with mandatory health surveillance under r356; potentially Category 5 (confined space — steriliser chamber during unloading)

code of practice

Model Code of Practice: Managing Risks of Hazardous Chemicals in the Workplace (SWA 2021); AS/NZS ISO 11135:2019 (EtO sterilisation); Dangerous Goods legislation (ethylene oxide UN 1040, Class 2.3 / Class 2.1); state EPA requirements for EtO atmospheric emissions

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Hazards

HazardConsequenceLikelihood
Inhalation of ethylene oxide gas during cylinder change, connection, and disconnection at the steriliserEtO cylinder change is the highest single-event acute exposure task. Connection and disconnection of the EtO supply at the cylinder manifold or steriliser port can release EtO at concentrations exceeding 100 ppm if not controlled. Acute effects: respiratory tract irritation, coughing, dyspnoea, nausea, vomiting, dizziness, and — at high concentrations — pulmonary oedema, neurological depression, and loss of consciousness. Acute overexposure must be treated as a medical emergency. Under the NTGC framework, the chronic carcinogenic risk from EtO makes every avoidable exposure at any concentration a legal compliance failure.Almost Certain (A) during cylinder change without supplied-air RPE and positive-pressure engineering controls
Inhalation of ethylene oxide during chamber door opening after cycle completionWhen the steriliser chamber door is opened at the end of a cycle, residual EtO that has not been fully removed by the aeration/evacuation cycle is released. The concentration immediately behind the door can be high, especially if the aeration phase was abbreviated or the vacuum pump is underperforming. Workers who open the chamber without RPE and without waiting for LEV to clear the door zone receive an acute bolus exposure. Repeated low-level exposures during chamber opening over a career represent a significant cumulative carcinogenic risk under the NTGC framework.Likely (B) without continuous EtO air monitoring at the chamber door and mandatory RPE during door opening
Skin and eye contact with liquid ethylene oxide or high-concentration EtO gas condensateLiquid EtO can cause severe chemical burns on skin and corneal damage on eye contact. At concentrations below liquefaction, EtO vapour absorbed through the skin contributes to the overall systemic dose. EtO is a direct alkylating agent — it reacts with DNA in skin cells as well as in the lung epithelium, giving dermal contact a carcinogenic dimension beyond the acute burn hazard.Possible (C) during cylinder handling, maintenance, or line breakage — highest risk during confined space maintenance tasks
Explosion and fire risk from ethylene oxide in the flammable range (3–100% by volume in air)Ethylene oxide has an exceptionally wide flammable range — 3% to 100% by volume in air — meaning virtually any EtO–air mixture can ignite. The autoignition temperature is 429°C but static electricity from standard clothing, UV lights, and many common ignition sources are sufficient to initiate combustion. A cylinder leak, burst connection, or steriliser seal failure can create an explosive atmosphere in seconds. Cylinder storage areas must comply with AS/NZS 60079-10-1 (hazardous area classification) and use only certified Ex equipment.Unlikely (D) with correct engineering but consequences are catastrophic (E) — risk matrix score: HIGH regardless
Chronic reproductive toxicity from ongoing EtO exposure in workers of reproductive ageEthylene oxide is classified as a Category 1B reproductive toxin (known human reproductive toxicant). Epidemiological evidence links occupational EtO exposure to spontaneous abortion and adverse birth outcomes in female CSSD workers. Male reproductive effects are less well characterised but in vitro evidence shows EtO causes sperm DNA strand breaks. Workers who are pregnant, planning pregnancy, or breastfeeding must be removed from EtO work and offered alternative duties under WHS Regulation r356 health monitoring obligations.Possible (C) with current WEL-based controls; risk persists even at exposures below the former numerical WEL
Atmospheric emissions of ethylene oxide from the steriliser exhaust and aeration cabinet, creating neighbourhood exposure riskEtO sterilisers vent exhaust gas — including residual EtO — through the facility's exhaust system to the external atmosphere. In urban hospitals and densely populated areas, this creates a community exposure concern and state EPA reporting and licence obligations. Failure to comply with EtO emission limits under state EPA licences can result in licence suspension, community complaints, and secondary regulatory action by the EPA in addition to WHS enforcement.Likely (B) without an EtO catalytic converter or scrubber on the exhaust stack

Controls (Hierarchy of Controls)

[Elimination] Evaluate clinical and device specifications to identify instruments that can be reprocessed by steam sterilisation (134°C/3 min or 121°C/15 min) or hydrogen peroxide plasma (Sterrad) sterilisation, eliminating EtO use — steam and H2O2 plasma are preferred where instrument compatibility allows
[Elimination] Specify single-use (SUD) alternatives for disposable instruments and implants currently sterilised by EtO where clinical equivalence and cost permit — eliminates the reprocessing cycle and EtO exposure risk entirely
[Substitution] Evaluate low-temperature hydrogen peroxide plasma (Sterrad), vaporised hydrogen peroxide (VH2O2), and ozone sterilisation as alternatives for heat-sensitive instruments — validated for most flexible endoscopes, power tools, and electronic components
[Engineering] Install fully enclosed, purpose-designed EtO sterilisers with integral aeration in a dedicated, negative-pressure sterilisation room exhausted directly to the external atmosphere via a catalytic converter or acid-water scrubber complying with state EPA licence conditions
[Engineering] Install continuous real-time EtO air monitoring at the steriliser door zone, cylinder connection point, and room boundary — fixed sensors calibrated 6-monthly; audible and visual alarm at 0.1 ppm (10% of the former WEL); evacuate room on alarm
[Engineering] Achieve and maintain negative pressure in the EtO sterilisation room (minimum −12.5 Pa relative to adjacent areas) verified by quarterly air pressure measurement — prevents EtO migration to adjacent areas
[Engineering] Install a local exhaust ventilation (LEV) slot extract at the chamber door opening position — captures EtO released on chamber opening before it disperses into the work zone; minimum 0.5 m/s face velocity
[Engineering] Store EtO cylinders in a dedicated external or semi-external cylinder store complying with AS 1596 (LPG storage) and AS/NZS 60079-10-1 hazardous area classification; use only certified Ex-rated electrical equipment in the store
[Administrative] ALARP assessment documented before commencement and reviewed annually and whenever steriliser model, process, or throughput changes — EtO NTGC status requires demonstration that no further reasonably practicable reduction is achievable
[Administrative] Personal exposure air monitoring — 8-hour TWA sampling using validated method (NIOSH 1614) on NATA-accredited laboratory tubes, before commencement, after any process change, and 6-monthly during ongoing operations; compare to ALARP reference and investigate any detectable result
[Administrative] Biological monitoring programme — urinary mandelic acid (metabolite monitoring, used where available) and haemoglobin adduct (hydroxyethyl-valine in Hb — specific for EtO) — 6-monthly; retain records 30 years under WHS Reg r356; refer to occupational physician for results above action level
[Administrative] Restrict access to the EtO sterilisation room to trained and medically cleared workers only; maintain access register; workers who are pregnant, planning pregnancy, or breastfeeding must be redeployed
[Administrative] EtO emergency procedure covering: cylinder leak (isolate, evacuate, call 000), overexposure (remove casualty, fresh air, supplemental oxygen, hospital transfer), and fire/explosion (evacuate, call 000, do not re-enter) — trained at induction and rehearsed 6-monthly
[PPE] Supplied-air respirator (SAR) Class 5D or higher (EN 14594 / AS/NZS 1716 equivalent) for cylinder change and connection/disconnection — the only acceptable RPE for peak-exposure tasks; PAPR with organic vapour + P3 cartridges for chamber door opening on monitors that confirm <1 ppm at the door
[PPE] Chemical-resistant gloves Category III (butyl rubber or neoprene ≥0.5 mm) for all EtO cylinder and manifold work; face shield (AS/NZS 1336) for cylinder connection tasks
[PPE] Antistatic garments and footwear in EtO cylinder storage and handling areas — EtO explosive range (3–100%) means ignition by static discharge is a real risk
[PPE] EtO emergency escape set (stored at room entry) — self-contained escape unit providing ≥10 minutes air supply for emergency egress if the room alarm activates during chamber maintenance

Recent Prosecutions

WorkSafe Victoria enforcement action — hospital CSSD EtO sterilisationImprovement and prohibition notices; undertaking to commission LEV upgrade and biological monitoring programme

A metropolitan hospital's CSSD was found to have inadequate EtO air monitoring (annual sampling only), no biological monitoring programme, and relied on disposable half-face respirators (not supplied-air) during cylinder change. Two CSSD workers reported symptoms consistent with EtO overexposure — headache, nausea, and paraesthesia — following a cylinder change. WorkSafe issued prohibition and improvement notices, required immediate installation of continuous EtO monitoring, SAR procurement, and engagement of an occupational hygienist for a full exposure assessment. The hospital was required to commission haemoglobin adduct biological monitoring for all workers with EtO exposure history.

2023 — WorkSafe Victoria enforcement register

NTGC transition enforcement — hospital and contract sterilisation sectorsCategory 1 (reckless exposure to NTGC): up to $11.8M body corporate; Category 2: up to $3.8M; EPA penalties for unlicensed EtO emissions are separate and additional

Following the December 2026 NTGC reclassification of ethylene oxide, state WHS regulators and health department safety branches announced targeted EtO sterilisation audits. Facilities without documented ALARP assessments, without continuous EtO air monitoring, and without biological monitoring programmes using haemoglobin adduct testing face Category 1 prosecution risk. The combination of NTGC status, reproductive toxin classification, and explosive hazard gives EtO the highest overall WHS risk profile of any chemical sterilant in clinical use.

2026 — Safe Work Australia NTGC Transition Guidance; state EPA enforcement registers

What Your SWMS Must Include

✓Ethylene oxide identified as NTGC and reproductive toxin with explicit reference to the ALARP obligation effective 1 December 2026 and the reproductive toxin redeployment obligation for pregnant workers
✓Task-by-task hazard identification covering cylinder change, chamber loading/unloading, aeration, maintenance, and scrubber/absorbent change — each task has a distinct exposure profile
✓ALARP assessment demonstrating all reasonably practicable engineering, administrative, and RPE controls have been implemented — reviewed annually and on process change
✓Continuous EtO air monitoring specification — sensor type, alarm setpoint (0.1 ppm or 10% of former WEL), calibration schedule, and evacuation procedure on alarm
✓Personal exposure air monitoring plan — sampling method (NIOSH 1614), NATA-accredited laboratory, sampling frequency, and investigation protocol for any detectable result
✓Biological monitoring programme — haemoglobin adduct (hydroxyethyl-valine) testing schedule, action levels, medical referral trigger, and 30-year records retention
✓Respiratory protection programme — SAR specification for cylinder change tasks; PAPR with OV+P3 for chamber operations; fit-testing records; maintenance schedule
✓Negative pressure room verification — measurement method, frequency, action level, and repair response if negative pressure is not maintained
✓EtO cylinder store hazardous area classification — reference to AS/NZS 60079-10-1; no ignition sources; antistatic PPE requirement
✓Emergency procedures for cylinder leak, overexposure, and fire — including evacuation, first-aid (remove, fresh air, oxygen, hospital), and 000 contact with EtO declaration
✓EPA compliance — EtO exhaust emission monitoring schedule and scrubber/converter performance verification frequency
✓Redeployment procedure for pregnant, planning-to-be-pregnant, and breastfeeding workers — offered alternative duties without income reduction

EtO NTGC from 1 December 2026 — ALARP, Continuous Monitoring, Haemoglobin Adduct Testing Required

This template pre-loads EtO-specific hazards, the NTGC ALARP obligation, cylinder change and chamber opening controls, biological monitoring requirements (haemoglobin adduct), confined space considerations, and EPA compliance checkpoints. CIH-reviewed, editable DOCX, 8 Australian state variants. $79 AUD.

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