Hazard - risk

Jargon is often used when talking about risk and some of this can be confusing. In the discussion about chemicals, the words "risk" and "hazard" are very often used as if interchangeable. In this section we offer our understanding of the difference between these expressions, appreciation of which is fundamental to any informed debate on the safety of chlorine and other chemical products or processes.

View a very interesting animated YouTube video on the differences between hazard and risk


A hazard is the way in which an object or a situation may cause harm. A hazard exists where an object (or substance) or situation has a built-in ability to cause an adverse effect. Such hazards include uneven pavements, unguarded machinery, an icy road, a fire, an explosion and a sudden escape of toxic gas.


The exposure is the extent to which the likely recipient of the harm is exposed to - or can be influenced by - the hazard. The presence of a potential target in the area and its distance from the hazard will determine the extent of the risk. For instance, a fire or explosion may cause damage to nearby buildings and their contents, or to vehicles and equipment, but will not harm people if there are no people present at the time.


Risk is the chance that harm will actually occur. As mentioned, a hazard exists where an object (or substance) or situation has a built-in ability to cause an adverse effect. Risk, on the other hand, is the chance that such effects will occur: the risk can be high or negligible.

Risks are all around us in our daily lives. Likewise, we all carry out risk assessments constantly, in one form or another, whether consciously or subconsciously. When deciding whether to cross the road, whether to eat healthily, and how to care for the family, we make judgements about the hazards involved, and assess the risks before taking action. Just as there are risks in our every day lives, so there are risks in activities that companies carry out, and in products they make.

BUT for harm to occur - in other words, for there to be a risk - there must be BOTH the hazard AND the exposure to that hazard; without both simultaneously, there is no risk.

View a very interesting animated YouTube video on the differences between hazard and risk

We can use an example of a dangerous animal. It can be seen as a "hazard". When the animal is free, people in the surroundings are exposed to it. Consequently, there is a risk that these people might be attacked. However, when the animal is closed in a cage, it remains "hazardous" but there is no exposure and, therefore, no risk.

Risks and hazards of chemicals

Does a hazardous chemical pose a risk? For there to be a risk there must be both the hazard and the exposure to that hazard present at the same time.

The hazard of a chemical means it has an intrinsic ability to cause an adverse effect for humans or environment. Risk is the chance that such effect will occur. Even if a chemical has hazardous properties, any risk to human health or environment is extremely low if the chemical is handled safely under controlled conditions.

Risk assessment is a management tool to determine whether, how and in what circumstances, harm might be caused. In order to assess risk, both hazard and exposure must be considered.

Although there may be several ways in which a risk assessment could be performed, it is important that the best way is chosen.

In the areas of human health and safety, research projects are underway on a wide range of topics, including:

Assessing the risks posed by individual products

Manufacturing emissions as well as monitoring data are being collected on chlorine-related chemicals with the aim of developing detailed risk assessments taking into account not only hazard but also exposure.
For further information on this go to our pages on REACH, high production volume chemicals and marine risk assessments (PDF documents).

This includes examining possible risks to human health (such as occupational exposure and impact on the general public) and to the environment, including the world's oceans. The physical properties of compounds are also studied.

Controlling pollution

International regulatory authorities continue to focus on the need to control chemicals which are persistent, toxic and liable to bioaccumulate (PTBs). Where these are prone to long-range transport and deposition, they are called persistent organic pollutants (POPs). Criteria to define, identify and manage these products are being developed by industry and the authorities.

Endocrine modulators

The debate continues on the possible causes of many human diseases and disorders, including cancer and birth defects, and on whether men's reproductive health is declining. A controversial hypothesis suggests that such health effects could be linked with exposure to environmental oestrogens, both natural and man-made; there is a lack of agreement between scientific experts on the grounds for this theory. This is a global issue which is of interest to the whole chemical industry. Some chlorine-based compounds are alleged to be involved. Recognising the importance of addressing any issue related to product safety, the chemical industry accepts the need to fund a complete scientific investigation to provide a sound basis for regulatory decisions.

Atmospheric changes

Research has been done to evaluate global production of natural organochlorines and to provide an inventory of changes in atmospheric emissions of major reactive types of chlorine derivatives. The research analyses samples of rain, snow and ice in remote regions of both hemispheres.