Hazardous chemicals are substances, mixtures or articles that meet specified hazard classifications under the Globally Harmonized System of Classification and Labelling of Chemicals (GHS).
They can present health hazards, such as toxicity, respiratory sensitisation or carcinogenicity, as well as physical hazards, including fire, explosion and corrosion.
Hazardous chemicals are used or generated across construction, manufacturing, laboratories, healthcare, mining, agriculture and many other workplaces.
Examples can include:
solvents and paints;
acids and alkalis;
pesticides;
isocyanates;
formaldehyde;
lead and lead compounds;
crystalline silica;
welding and process contaminants; and
fuels and other flammable substances.
The important distinction is between hazard and risk. A chemical may have hazardous properties, but the actual risk to workers depends on how it is used, the amount present, how workers can be exposed and the controls in place.
How Are Hazardous Chemicals Classified?
Australia uses the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) for workplace hazardous chemicals.
Manufacturers and importers are responsible for determining whether a chemical is hazardous and assigning the appropriate classification. Australia currently uses the 7th Revised Edition of the GHS (GHS 7) for workplace hazardous chemical classification and labelling.
The classification determines information that appears on the chemical's:
label;
hazard pictograms;
signal word;
hazard statements;
precautionary statements; and
Safety Data Sheet.
Common GHS hazards include acute toxicity, skin or eye corrosion, respiratory sensitisation, carcinogenicity, reproductive toxicity and organ toxicity, together with physical hazards such as flammability and explosivity.
How Can Workers Be Exposed to Hazardous Chemicals?
The significance of a hazardous chemical depends heavily on the route and level of exposure.
Inhalation
Workers may inhale dusts, fumes, mists, vapours or gases.
Examples include:
respirable crystalline silica generated by cutting concrete or stone;
solvent vapours;
welding fumes;
spray-painting aerosols; and
airborne metal contaminants.
For many occupational hygiene investigations, inhalation is the primary exposure pathway being assessed.
Skin Contact and Absorption
Chemicals can contact or be absorbed through the skin.
This may occur during handling, mixing, cleaning, spills or contact with contaminated surfaces.
Chemical burns, irritation and sensitisation may occur, while some substances can also contribute to systemic exposure through dermal absorption.
Ingestion
Workplace ingestion usually occurs indirectly.
Contaminated hands, food, cigarettes, drink containers or work surfaces can result in chemicals being transferred to the mouth.
This pathway can be particularly important for contaminants such as lead where good workplace hygiene is essential.
Injection
Less commonly, hazardous substances can enter the body through puncture wounds, sharps or high-pressure equipment.
What Health Effects Can Hazardous Chemicals Cause?
Health effects depend on the chemical, concentration, duration and frequency of exposure and individual susceptibility.
Some chemicals can produce acute effects shortly after exposure, including:
irritation of the eyes, nose or throat;
headaches or dizziness;
nausea;
respiratory irritation;
skin irritation;
chemical burns; or
acute poisoning.
Other effects can develop following repeated or long-term exposure.
These can include:
occupational asthma;
respiratory disease;
neurological effects;
organ damage;
reproductive effects;
sensitisation; and
cancer.
Safe Work Australia notes that hazardous chemicals can cause immediate effects such as poisoning and burns as well as longer-term conditions including lung damage, nerve damage and cancer.
However, the presence of a hazardous chemical does not by itself establish that workers are experiencing a harmful exposure.
That requires consideration of how much exposure is actually occurring.
How Are Hazardous Chemicals Regulated in NSW?
In NSW, workplace hazardous chemicals are primarily regulated through the Work Health and Safety Act 2011 and Work Health and Safety Regulation 2025.
The WHS framework includes requirements relating to:
hazardous chemical classification;
labelling;
Safety Data Sheets;
hazardous chemical registers;
storage and handling;
worker information and training;
exposure standards;
air monitoring;
health monitoring;
placards and manifests for larger quantities; and
emergency planning.
The current NSW Work Health and Safety Regulation 2025 also requires PCBUs to ensure that people are not exposed to airborne substances above the applicable exposure standard and specifies circumstances in which air monitoring must be undertaken.
What Is a Safety Data Sheet?
A Safety Data Sheet (SDS) provides information about a chemical's hazards and how it should be safely used, handled, stored and managed.
An SDS typically provides information on:
chemical identification;
hazardous ingredients;
health and physical hazards;
first aid;
firefighting;
spill response;
handling and storage;
exposure controls;
PPE;
physical and chemical properties; and
disposal considerations.
Workplaces using, handling or storing hazardous chemicals must generally have access to the current SDS for those chemicals.
The SDS is an important starting point for a risk assessment, but it does not tell you the actual level of worker exposure under your particular workplace conditions.
Does a Workplace Need a Hazardous Chemical Register?
Generally, yes.
A workplace hazardous chemical register must identify the hazardous chemicals used, handled or stored at the workplace and include the current SDS for each chemical on the register.
There are some exemptions, including certain consumer products and chemicals in transit.
The register should be kept current and accessible to workers who may be affected by those chemicals.
Larger quantities of certain hazardous chemicals can also trigger separate placard and manifest requirements.
What Are Workplace Exposure Standards?
For many airborne contaminants, a legally enforceable occupational exposure value applies.
As at September 2026, Australia is in the final stage of transitioning from Workplace Exposure Standards (WES) to Workplace Exposure Limits (WEL).
Until 30 November 2026, workplaces must continue to comply with the existing Workplace Exposure Standards.
From 1 December 2026, the new Workplace Exposure Limits for Airborne Contaminants take effect.
The change is more than terminology. Safe Work Australia reviewed the exposure values, with a number of limits changed and additional substances included.
Exposure standards and limits should also not be interpreted as a line between "safe" and "unsafe" exposure.
Workplace risks still need to be eliminated or minimised so far as is reasonably practicable, including where a contaminant does not have a specified exposure value.
When Is Air Monitoring Required?
Air monitoring is not automatically required simply because a hazardous chemical is present.
Under the NSW WHS Regulation, air monitoring is required for a substance with an applicable exposure standard where:
there is uncertainty, on reasonable grounds, about whether the airborne concentration exceeds the relevant standard; or
monitoring is necessary to determine whether there is a risk to health.
This is an important distinction.
For some workplaces, the risks and controls are well understood and exposure can be adequately managed without routine monitoring.
In other situations, occupational hygiene monitoring may be needed to establish:
the worker's personal exposure;
whether an exposure standard or limit is being approached or exceeded;
which tasks are contributing most to exposure;
whether engineering controls are effective; or
whether additional controls are required.
Air monitoring should be designed and interpreted by a suitably competent person. Safe Work Australia specifically identifies occupational hygienists as an example of professionals with the skills to undertake and interpret this work.
Personal Monitoring Versus Static Monitoring
These two forms of monitoring answer different questions.
Personal exposure monitoring uses sampling equipment positioned within a worker's breathing zone while they undertake their normal activities. It is used to estimate that individual's occupational exposure.
Static or area monitoring measures airborne contaminant concentrations at a fixed location.
Static monitoring can be useful for investigating contaminant migration, assessing particular work areas or understanding how concentrations vary around a process, but it does not automatically represent a worker's personal exposure.
The monitoring strategy should therefore be selected according to the question being investigated.
When Is Health Monitoring Required?
Health monitoring is also not required for every worker who handles a hazardous chemical.
In NSW, it is required in specified circumstances where there is a significant risk to a worker's health from exposure to particular hazardous chemicals, including chemicals listed in Schedule 14 of the WHS Regulation. Other chemicals may also require health monitoring where suitable methods exist to detect the effects of exposure.
Examples of chemicals specifically addressed by the health-monitoring framework include:
crystalline silica;
inorganic arsenic;
benzene;
cadmium;
inorganic chromium;
isocyanates;
inorganic mercury;
organophosphate pesticides; and
polycyclic aromatic hydrocarbons.
Lead and asbestos have separate specific requirements.
Health monitoring must be undertaken or supervised by an appropriately experienced registered medical practitioner.
Importantly, health monitoring does not replace exposure controls. Its purpose is to help identify whether exposure may be affecting workers and whether existing controls remain effective.
How Should Hazardous Chemical Risks Be Managed?
The first step is to understand:
what chemical is present + how it is used or generated + who can be exposed + how exposure occurs + how significant that exposure may be.
Risk controls should then follow the hierarchy of controls.
Where reasonably practicable, this means prioritising measures such as:
eliminating the hazardous chemical or process;
substituting a less hazardous chemical;
isolating the process;
enclosing or containing the source;
local exhaust ventilation;
automated or wet processes;
changes to work practices; and
appropriate respiratory or personal protective equipment where residual risks remain.
Safe Work Australia requires risks associated with hazardous chemicals to be eliminated so far as reasonably practicable, or otherwise minimised using the hierarchy of controls.
PPE should therefore generally be considered as part of the overall control strategy rather than the default response to uncontrolled exposure.
Hazardous Chemicals and Occupational Hygiene
Chemical risk management becomes more complex where the extent of exposure cannot be established from an SDS or workplace inspection alone.
An occupational hygiene assessment can help determine:
what contaminants workers may be exposed to;
the important tasks and exposure pathways;
appropriate sampling methods;
personal exposure concentrations;
compliance with applicable exposure standards or limits;
effectiveness of existing controls; and
practical measures for reducing exposure.
This can include monitoring for contaminants such as:
respirable crystalline silica;
inhalable and respirable dust;
metals;
solvents and volatile organic compounds;
welding fumes;
lead;
formaldehyde; and
other task-specific airborne contaminants.
The objective should not simply be to collect air samples. A useful assessment connects the work activity, contaminant source, exposure pathway, monitoring results and control measures.
Hazardous Chemical and Exposure Assessments in NSW
Confluence Environmental provides occupational hygiene assessment and workplace exposure monitoring across NSW, including personal and static air monitoring, dust and respirable crystalline silica assessment, metals and lead monitoring and other hazardous chemical exposure investigations.
Monitoring programs are developed around the work activities and potential exposure pathways so that the results can be used to evaluate workplace conditions and inform appropriate controls.