Many substances have been deemed ‘ Dangerous Goods’, and have been listed in the Australian Code for the Transport of Dangerous Goods (ACTDG). This code gives information on how Dangerous Goods should be packaged, stored and handled. The placarding requirements, and compatibilities of certain classes of materials based on the risk associated with each. It also gives information on handling disasters. It does not give information on method of use of Dangerous Goods or any other hazardous substance.

Many other substances are introduced into the workplace on a limited, and almost uncontrolled basis.

A registration scheme (NICNAS) for these materials (Workplace Hazardous Substances) has been introduced by the National Occupational Health and Safety Commission (NOHSC), and registration of new materials to be introduced into Australian workplaces, shall be a requirement, under proposed legislation, currently under development.

To use Workplace Hazardous Substances ‘safely’, i.e. in a way in which risk of injury to workers and the public is tolerable (minimal and acceptable), an organisation must provide a paradigm (and culture), which encourages workers to be risk conscious when implementing use of hazardous substances. This includes being proactive in implementing adequate controls. It should also empower them to make decisions where they are accountable and/or responsible for use of hazardous substances, and provide a mechanism for communicating to the Management Representative, and for him/her to formally address their concerns.

The proposed new legislation for hazardous substances being developed by NOHSC, has a very strong requirement for ‘Risk Assessments’ to be performed by employers, where hazardous substances are to be used.

This approach differs substantially from the one in previous legislation, where prescriptive laws based on generic risk assessments (often performed by bureaucrats), are used. These laws failed to provide adequate protection for workers, as the risks associated with hazardous substances are simply too numerous to respond satisfactorily to this approach. It is impossible to introduce the number of regulations required, to force employers to manage safely, with this type of legislation.

The new legislation is performance based, i.e. it specifies outcomes rather than giving direct instructions on risk control, for specific instances.

An example of use of performance based legislation may be seen, in the way Dangerous Goods of Class 3 with subrisk Class 6 are to be managed. This group includes most industrial solvents in common use.

The risks associated with solvents in the workplace are related to their physical and chemical properties, their flammability, and toxicity.

The physical properties include:

Flashpoint - the temperature at which a solvent will ignite in a closed or open cup under standard test conditions, when exp;osed to an ignition source

Boiling point – the temperature at which a solvent changes entirely from liquid to vapour at normal pressures.

Autoignition temperature – the temperature at which a solvent will spontaneously ignite.

Latent Heat of Vapourisation – the energy requred to convert a specific volume of solvent to vapour.

Vapour pressure at room temperature – the partial pressure of vapour above the solvent at normal and elevated temperatures.

Upper and Lower Explosive Levels - the limits of the concentration range within which the material will explode upon ignition, when mixed with air.

Chemical properties may be various, including simple hydrocarbon solvents such as petroleum ether, partially oxidised such as propylene , halogenated such as trichlorethylene, and many other variations. The differing (and, sometimes very minor changes to) chemical properties give rise to a wide range of acute and chronic toxicities.

Acute toxicities relate to immediate poisoning of exposed workers.

Chronic toxicites relate to effects induced through repeated exposure (to low levels). Information about the effects may be derived from epidemiological studies in which unexposed populations of workers are compared staistically with exposed populations, to detect effects such as cancer, brain damage etc.

In collecting the above information, it is possible to predict the risk profile of a solvent in various scenarios.

This risk profile is the basis for categorising the solvent in the Dangerous Goods Risk Classes. It can also be used as the basis of a ‘Risk Assessment’, and determination of appropriate ‘Risk Controls’ on a case by case basis, as required by the proposed new legislation.

While control of storage and transport of Dangerous Goods is important for prevention of large fires and environmental disasters, most workplace injuries caused by exposure to solvents are due to incorrect method of use, and inadequate ventilation in particular. Placarding, segregation of incompatible materials, correct packaging and other measures in the ACTDG will not provide protection against misuse in the workplace.

When performing a ‘risk assessment’, it is important to conduct a ‘WHAT IF’ study and consider as many scenarios as possible, considering the physical and chemical properties of the solvent, and the characxteristics of the workplace where it is to be used.

For example carbon disulphide is extremely toxic, causes brain damage and insanity, it has a very low autoignition temperature, that is , if it is spilt on a hot surface, it can cause a fire to start, and this may spread to other materials in the workplace. It is a ‘High Risk’ material. Using the hierachy of controls it should primarily be eliminated from the workplace.

If there is an extremely pressing requirement to use this solvent, precautions must be taken to minimise the risk to a level tolerable to workers. This would include provision of very efficient ventliation, removal of ignition sources and hot surfaces, use of personal protective equipment.

The workplace should be monitored for carbon disulphide vapour, however it should be recognised that the guideline for exposure in the workplace (TLV TWA), if it exists , would be very suspect for this material. Exposure at levels acceptable to the American Conference for Governmental Industrial Hygienists, who usually set TLV’s, may not be acceptable to workers in Australia. The values acceptable to the National Health and Medical Research Council (the responsible Australian Body), may not be stated, or may also present an unacceptable risk.

In evaluating a workplace hazardous substance, a material safety data sheet, may be consulted. It should be noted that in preparing these sheets, consultants in particular may be sensitive to their risk exposure by preparing the sheet. Often a single reference in literature may cause a chronic effect such as cancer to be attributed to a substance.

The phrase ‘ suspected tumorigen’ occurs quite often in MSDS’s, however there are actually only about twenty scheduled carcinogens in Victoria, under the existing Dangerous Good legislation. This means that where there is suspicion that a new material may be carcinogenic, an Occupational Hygienist should be consulted. (MSDS’s may often be unreliable as far as chronic effects are concerned, but usually err on the side of safety. This may be an expensive error in some cases, as an overkill situation may result.)

We cannot know the consequences (chronic effects) of repeated exposure in advance in most cases, and should always mitigate the risk associated with an identified hazard.

It is important that workers should know when to ask for help from a competent professional.

Alan Cotterell

2^nd August 1999