Managing the risks of hazardous chemicals 

As part of undertaking a hazardous chemicals assessment and implementing control measures, you must identify what the hazards are from the chemical(s). The most straightforward way to identify these is to obtain a safety data sheet (SDS) from the chemical manufacturer.  

A SDS contains information on the hazardous chemical relating to: 

Elements within a SDS


Manufactured chemicals will follow the UN Global Harmonised System of Classification and Labelling of Chemicals (GHS). It is not a formal treaty or a legally binding international agreement, so countries will create local or national legislation to implement the GHS.  

Reading a SDS 

The GHS contains a specification for SDS to follow a 16-section format: 

Section 1: identification of the chemical / mixture and of the organisation. An important consideration in this section is making sure that the name of the chemical matches up with the label on the chemical container. Many chemicals have similar names but have different properties. This section will also identify relevant uses of the chemical. Section 1 of the SDS must include manufacturer/supplier contact information and an emergency contact number. 

Section 2: hazard identification. This is one of the most important sections of the SDS for writing a hazardous chemical assessment. This section outlines the physical and health effects of the chemical. It will include any relevant hazard warning labels.  

Globally Harmonized System Classification Labelling and Packing symbols 


Section 3: composition / information in ingredients. This section provides information on the composition of the substance, including the percentages if its hazardous constituents. It does not give a full breakdown of all substances, but will include those that: 

  • contribute to the overall hazard classification 
  • are present at concentrations above certain levels of concern 
  • have indicative occupational exposure limit values (IOELVs). 

Section 4: first aid measures. This section is useful to identify initial first aid treatment if a worker is exposed to a chemical. First aiders also need to be made aware of the information contained in an SDS to allow them to respond in the correct way in the case of an emergency. 

Section 5: firefighting measures. Although not relevant to identifying the health hazards in a chemical, it is helpful in considering fire risk assessments, the storage of chemicals identified as flammable or explosive, and to identify any specific firefighting measures that may be required.  

Section 6: accidental release measures. This section is helpful for identifying different work activities with chemicals, this may include cleaning activities for spillages for example.  

Section 7: handling and storage. This section expands on previous information. 

Section 8: exposure controls / personal protection. This section identifies if there are exposure standards, such as indicative occupational exposure limit values or biological limit values set for the chemical. In relation to personal protection, it may include detail on the types of personal protection that may be required.  

Section  9: physical and chemical properties. Included for completeness. 

Section 10: stability and reactivity. Included for completeness. 

Section 11: toxicological information. This section is useful when determining the detailed potential health effects of the chemical. 

Section 12: ecological information. Included for completeness.

Section 13: disposal considerations. Included for completeness. 

Section 14: transport information. Included for completeness. 

Section 15: regulatory information. This section outlines the OSH (and environmental) legislation specific to the chemical that may not have been included in other sections. 

Section 16: other information. This section is used to provide any additional information the manufacturer considers important for the user to know. It may include information on revisions from earlier versions, relevant risk or hazard phrases, precautionary statements, or advice on training workers.  

Where hazardous chemicals are produced as part of a process or are naturally occurring, then advice should be sought from process engineers, industrial chemists or other guidance sources.  

Another way of identifying chemical hazards present in the workplace is by ensuring that occupational hygiene monitoring is undertaken, such as air sampling and personal dosimetry. Occupational hygienists can measure build-up of hazardous chemicals in the work atmosphere and worker exposure. Biological monitoring of workers can also identify chemical build-up in the body, by the use of blood and urine testing. 

Other sources of information 

It is critical to gather information about: 

  • how is the chemical used (or produced)? 
  • how much is used? 
  • for how long? 
  • Who is at risk? Particular groups of workers may be at higher risk from working with some chemicals.  

Together the information will enable appropriate controls or a combination of controls to be put in place.  

Assessment of chemical hazards and their use 

Assessing exposure to a hazardous chemical involves looking at the type, intensity, concentration, length, frequency and occurrence of exposure to workers, including the combined effects of hazardous chemicals used together and the related risk. This includes the amount of the chemical being used and any indicative occupational exposure limit values (IOELVs) associated with it.  

Assessment of a chemical is a subjective (or qualitative) process and is based on the assessor’s knowledge and experience of not only the chemical in question but also the activity and environment that it is being used in. Existing controls in place will influence how an assessor will decide on the level of risk.  

Methods for recording this decision-making process vary, but can be numerical, using a high, medium or low scale or using a red/ amber/green rating. 

Unlike most risk assessments, it is worth assessing the uncontrolled risk, as it helps to identify what exposure controls are needed for different routes and different groups of people. 

Workers at higher risk from working with chemicals 

As well as reviewing the chemical being used, it is important to consider any workers who may be particularly at risk and specify the measures to be taken to protect them, including any additional training and information they require. It is also important to consider workers who may not be routinely exposed to chemicals but who could be at risk during maintenance or repair work or accidentally exposed, for example to intermediary products in a chemical production process that is usually closed. Workers should know who to contact if things go wrong and how to protect themselves in the event of an incident. Certain groups of workers may be at increased risk when working with hazardous chemicals. This can be due to: 

  • susceptibility to certain chemicals-communication difficulties  
  • inexperience-workers undertaking nonroutine, high-risk duties.  

Workers at higher risk include: 

  • new and expectant mothers 
  • workers of reproductive capacity 
  • migrant workers 
  • shift workers 
  • young people 
  • older workers 
  • workers with medical conditions. 

Implementing controls  

This involves drawing up an action plan. It should list the steps to be taken, in order of priority, to reduce the risks to workers   and should specify how, by whom and by what date each step should be taken. In some countries, for standard working operations such as filling, pumping, drilling, grinding and welding, practical information on tested control techniques is available (direct advice or control guidance sheets).  

Control measures for hazardous chemicals (using the hierarchy of control) 

There are many measures that are used to control exposure from chemicals. Certain controls are more effective than others. This order of effectiveness is known as the hierarchy of control. 

Eliminating the risk 

  • Change the activity so that a hazardous chemical is not used.
  • Use a non-harmful substance instead of a hazardous one (known as elimination through substitution). 

Substituting the system of work, substance or plant 

  • Change the type of hazardous chemicals kept on site. 
  • Use a pelletised form of the hazardous chemical, rather than a powdered form.
  • Replace the chemical with a safer substitute. 
  • Vacuum or use an industrial sweeper to clean up concentrated dusts, rather than sweep them up manually. 
  • Apply the substance using a brush or roller instead of by spray gun application. 
  • Select a product with less volatile ingredients.

Engineering controls 

  • Use Local Exhaust Ventilation (LEV) to remove fumes. 
  • Increase ventilation.
  • Use spill containment. 
  • Use safety relief valves.
  • Use overfill protection. 
  • Automate processes to remove / reduce the worker interface. 

Administrative controls 

  • Introduce a restricted work area. 
  • Locate potentially hazardous materials or processes away from frequently-used thoroughfares and buildings. 
  • Separate goods from other hazards. 
  • Segregate incompatible substances. 
  • Use placards or hazard warning signs. 
  • Enhance housekeeping / cleaning.  
  • Provide specific training and work instructions. 
  • Provide spill clean-up equipment. 

Example of a hazardous chemical control measure 

The most common engineering control to prevent worker exposure to inhalable and respirable chemicals is local exhaust ventilation (LEV). Workplace New Zealand defines LEV as:  

“…an engineering system that captures dusts, vapours, and fumes at their source and transports them away from the worker’s breathing zone. This prevents workers from inhaling these substances and reduces contamination of the general workplace air.” 

 There are several designs of LEV that are used in the workplace: 

  • glove boxes-spray booths 
  • on-tool extraction 
  • flexible capturing hoods 
  • extracted workbenches.  

These generally consist of: 

  • an inlet/enclosure/hood to capture the contaminated air 
  • ducting to carry the air away from the point of extraction 
  • filters to clean the contaminated air  
  • a fan to draw the contaminated air from the hood to the filter via the ducting to an exhaust stack 
  • an exhaust stack that discharges filtered air outside the building.  

LEVs are only effective if they are well designed, maintained and used properly. 

Revising and updating  

The last part of a hazardous substance assessment is reviewing the risk assessment. This document should be regularly revised and updated. Effective risk assessment and prevention require organisations to keep themselves and their workers well informed and trained. Workers also need to be consulted on the risk assessment and any changes to the chemicals, products and work processes involved in their jobs.