WorkSafe Western Australia's ergonomists answer the most frequently asked manual handling question
WHAT IS A SAFE WEIGHT?

The WorkSafe Western Australia Commission's 1996 Manual Handling Code of Practice (Appendix G) provides the following guidance concerning the handling of heavy objects:

2.1 Heavy
The risk of injury increases as the weight of the load increases.

Evaluating the risk of weight of the object needs to take into account:
how long the load is handled 
how often the load is handled.

As a guide, the risk of back injury increases when loads over 16 kg are handled from a standing position. As weight increases from 16 kg to 55 kg the percentage of healthy adults who can safely lift, lower or carry decreases. 
Generally, no single person should be required to lift, lower or carry loads over 55kg.

On occasions, objects over 55 kg may be moved but not lifted, eg rolling a 200 litre drum.

A manual handling task identified as a hazard needs to be assessed so controls can be applied to reduce the risk of injury. The weight of a load is one of 24 common risk factors listed in the code of practice for assessing a manual handling task.

These risk factors fall into four basic categories:
1. actions and postures
2. the load (including its weight)
3. the work environment
4. employee characteristics.

It is not possible to accurately assess manual handling tasks considering only the weight of the load. For example, considering the weight of the load will not reduce the risks of manual handling tasks with highly repetitive movements and poor postures.

The percentage of healthy adults who can safely handle a load decreases as the weight of the load increases from 16kg to 55kg. This does not mean that all people in all circumstances can safely handle 55kg loads. In many circumstances 55kg is not a safe weight to handle. This weight range is a guideline giving an upper weight limit above which manual handling is unsafe, regardless of other factors.

Similarly, not all loads below 16kg are safe to handle in all circumstances. This weight is also a guideline, and in some circumstances loads weighing less than 16kg are unsafe to handle.

There are variations in people's height and weight, and there are variations in their lifting ability. Design tasks that are safe for all people in workplaces. The Occupational Safety and Health Act 1984, section 19, requires that the work environment does not expose workers to hazards.

Many researchers have developed safe lifting guidelines, including safe lifting limits, but no one has ever defined a single absolute safe lifting weight. This is simply not possible. Tables and formulae have been developed for a variety of task factors, including several internationally recognised tables and formulae giving maximum acceptable weights for lifting, lowering, carrying, pushing and pulling. Many of these are available in the WorkSafe Western Australia library.

CONCLUSION

As a definitive, absolute safe lifting weight is not possible, a common sense approach is required for assessing manual handling tasks. Weight should be considered, along with all other factors in the context of the task, such as actions or postures, other load characteristics, the work environment and human characteristics. 
Always consider weight as a risk factor for tasks with loads of 16kg to 55kg, and do not lift, lower or carry loads over 55kg.

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