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ALARP (As Low As Reasonably Possible)

By Graphic Products Editorial Staff

ALARP (As Low As Reasonably Possible)

What is ALARP?

ALARP is the acronym for “As Low As Reasonably Possible,” a principle primarily used in the United Kingdom. In other parts of the world, safety and environmental legislation tends to require that absolute standards be met. The principles of ALARP are used in the United States in the area of nuclear radiation protection, where it is usually called “As Low As Reasonably Achievable” (ALARA.) The Nuclear Regulatory Commission (NRC) defines this term as:

Making every reasonable effort to maintain exposures to ionizing radiation as far below the dose limits as practical, consistent with the purpose for which the licensed activity is undertaken, taking into account the state of technology, the economics of improvements in relation to state of technology, the economics of improvements in relation to benefits to the public health and safety, and other societal and socioeconomic considerations, and in relation to utilization of nuclear energy and licensed materials in the public interest.

In this article we'll be talking about the use of ALARP in the United Kingdom.


In the U.K., the term “SFAIRP” is also commonly used, standing for “So Far As Is Reasonably Practicable.” It has the same essential meaning as ALARP, and is the term most commonly used in safety regulations, and for health and safety at work. ALARP, on the other hand, is commonly used by risk specialists and duty holders. A “duty holder” is the person or organization that has a legal duty to ensure there is compliance with laws, regulations, and codes.

In common use, the terms ALARP and SFAIRP are used interchangeably. However, they do have specific legal meanings, so when used in legal documents one or the other will specifically be used.

ALARP – What Does “Reasonably Practicable” Mean?

The term “reasonably practicable” was defined in the UK by the Court of Appeal in its judgment in Edwards v. National Coal Board, in 1949. It stated:

'Reasonably practicable’ is a narrower term than ‘physically possible’ … a computation must be made by the owner in which the quantum of risk is placed on one scale and the sacrifice involved in the measures necessary for averting the risk (whether in money, time or trouble) is placed in the other, and that, if it be shown that there is a gross disproportion between them – the risk being insignificant in relation to the sacrifice – the defendants discharge the onus on them.

What this means is that the risk is weighed against the sacrifice (cost) that is necessary to reduce the risk. The decision is weighted in favor of safety and health, because it must be shown that the sacrifice is hugely disproportionate to the safety and health benefits.

The advantage of ALARP is that it allows employers to choose the methods for mitigating hazards that work best in their circumstances. This encourages innovation as well as using the best practices. How is the ALARP approach working out in the U.K., compared with the U.S. approach of establishing absolute standards? The following gives the most recent fatality and injury rates in the U.S. and U.K.:

United Kingdom (2012/2013 HSE Data)

  • 312 non-fatal injuries per 100,000 workers
  • 0.5 fatalities per 100,000 workers

United States (2012 fiscal year BLS Data)

  • 1,120 non-fatal injuries per 100,000 workers
  • 3.2 fatalities per 100,000 workers

There are other differences between the U.K. and the U.S. safety and health systems that impact the above numbers. However, these numbers do show that ALARP is a reasonable approach to enforcing safety in the workplace.

What Is a Hazard? What Is a Risk?

If we are to balance the seriousness of a hazard or risk, against the cost of further mitigation of that hazard, we need to know the definition of the terms “hazard” and “risk.”

In the U.K., the Health and Safety Executive (HSE) is the equivalent of the Occupational Health and Safety Administration (OSHA) in the United States. The HSE defines a hazard as:

A hazard is something (e.g. an object, a property of a substance, a phenomenon or an activity) that can cause adverse effects. For example:
Water on a staircase is a hazard, because you could slip on it, fall and hurt yourself; loud noise is a hazard because it can cause hearing loss; or breathing in asbestos dust is a hazard because it can cause cancer.

The HSE defines a risk as:

A risk is the likelihood that a hazard will actually cause its adverse effects, together with a measure of the effect.

The likelihood can be given as a probability. The probability can be expressed as being, for example, a 0.1% chance (1 in a 1000). The probability can also be expressed as a statistic, such as 1000 cases per year.

In addition to identifying the hazard and understanding the risk, we'll need to know the “effect.” The “measure of the effect” is a measure of the impact on humans. The question that needs to be answered is: How serious is the health impact or the injury that results?

Let's look at some examples that show how these three terms apply:

  • In the US in fiscal year 2012 there were 668 workers (risk) who died (effect) as a result of a fall, slip or trip (hazard) in the workplace.
  • “Struck-by” injuries (hazard) resulting in time off from work (effect) are the most common (risk) type of injury in the logging industry.

How Do You Know a Risk is ALARP?

Determining if a risk is ALARP involves applying one of two approaches:

  1. In most situations an existing good practice can be applied. In this situation, the risk, hazard, and effect are known and have already been addressed by others. The HSE defines “good practice” as:

    “those standards for controlling risk that HSE has judged and recognised as satisfying the law, when applied to a particular relevant case, in an appropriate manner.”

    These are generally consensus standards that have been developed in cooperation with employers, trade associations, unions, suppliers, and government departments.

  2. In some cases there may not be established good practices that apply. In these cases areas in which good practices apply should be identified and addressed using established practices. This will address part of the hazard, or partially reduce the risk or effect.

    Next determine what additional steps can be taken to further reduce the risk, or mitigate the hazard. There is an assumption that duty-holders will use first principles to compare the risk with the sacrifice that is required to further reduce it, and then take action based on that evaluation.

ALARP and Carrot Diagrams

One useful tool that helps map risks is the carrot diagram. The diagram is shaped like a carrot, wider at the top and pointed at the bottom, and is divided into three regions: generally unacceptable, tolerable, and acceptable. It allows industries to visually represent risks, as well as recognize risks that should be further reduced. ALARP principles apply to all regions until it is demonstrated that further risk reduction in infeasible or that the cost of reducing the risk further is disproportionate to the benefit.

The carrot diagram is one useful tool to help map risks as part of ALARP.

When using the carrot diagram to determine risk levels, a situation might involve multiple “acceptable” risks. This could move the total risk to “tolerable” or even “unacceptable.” Look at risks individually and as part of the total situation to ensure that ALARP is used correctly.

ALARP – The Role Of Labels and Signs

Effective, clear, durable labels and signs are an important part of any plan to protect health and safety. They warn about hazards, and inform workers about the actions that need to be taken to avoid or mitigate those hazards. For example, signs direct people to follow pathways that avoid hazards, and remind them about ways to protect themselves from hazards.