Current Course - Level 2 award in COSHH

What are ‘Substances Hazardous to Health’?

Many substances, both natural and chemically produced, can be harmful to human health, or toxic. In today’s industrialised world, as we focus on producing goods and undertaking services as efficiently and cheaply as possible, we often encounter a number of toxic substances in the course of our working day. These substances can be chemicals we bring into our workplace, they can be the by-products of work we do (for instance, sawdust or brick dust) or they can be present in our working environment (such as asbestos). As discussed in the previous chapter, we are all responsible for ensuring that all substances are used safely and responsibly, in order to protect health, lives and our environment.

Think of some examples of substances you use in your working life, and in your business as a whole. For instance, most businesses use cleaning products of some type, to keep equipment running well or just to keep their office space clean. Used in the wrong way, cleaning products can cause irritation to the skin. As a baker, you may use fine flour or icing sugar - whilst these wouldn’t be harmful to touch, inhaling very fine particles over a period of time can lead to breathing problems, and fine powders are also at risk of causing explosion. As a fish and chip van owner, think about the acetic acid that you dilute to create consumable vinegar, which is highly corrosive when undiluted.

The examples above should begin to show you that substances hazardous to health can take many forms, including:

  • Liquids, including chemical products
  • Fumes, vapour and gases
  • Dust
  • Micro-organisms (for instances viruses)
  • Nanotechnology (microscopic molecules or atoms generally found in laboratories)

Substances found in many different workplaces can be hazardous to health


How can these substances cause harm?

The body can be exposed to toxic substances in a number of ways, for instance:

  • Breathing in (inhalation)
  • Contact with the skin
  • Injection into the body
  • Swallowing
  • Contact with the eyes

The most common health conditions caused by harmful substances in the workplace are:

  • Skin problems, such as dermatitis
  • Respiratory problems
  • Asthma
  • Occupational cancer
  • Lung disease

These in general are ‘chronic’ conditions, that is to say conditions that develop over time and continue to affect the sufferer for a period of time.

Examples of chronic health conditions caused or made worse by substances in the workplace are:

  • A worker in a repair garage who develops respiratory (breathing) problems following repeated inhalation of spray paint
  • A cleaner who develops dermatitis on the hands and arms from daily use of cleaning products

In some cases, the health conditions that can occur from exposure to substances can be acute - that is, they happen quite suddenly, or after a short exposure to the substance. This is not to say that they are not serious - examples of acute health conditions that occur include burns caused by splashes of corrosive chemicals to the skin or eyes, which could lead to permanent disfigurement, impairment or loss of sight.

Another type of substance that can cause harm to health, particularly in food related businesses, is an allergen. Allergens are specific proteins found in foods and ingredients that cause the body’s autoimmune response to react in an extreme way in certain individuals. Reactions can happen when the allergen is touched, eaten, or in extreme cases when particles of the ingredient are breathed in. Whilst most allergic reactions result in uncomfortable or painful symptoms (sore eyes, asthma, rash, sneezing, abdominal pain), allergens can also cause anaphylactic shock in sufferers, which can ultimately lead to death.


The 14 most common allergens are listed in the course downloads. If you work in a food related business, you will need to consider these ingredients as potentially hazardous to health. If you would like to learn more about food allergy, the science behind it and how to protect your business, you might want to take a look at a specific allergy awareness course.

Click to download

The 14 Allergens Poster


In some cases, an individual can become ‘sensitised’ to a substance. This means that, although they may have worked with a substance for a period of time without any ill effect, they suddenly start to react to this product.

Often this happen in reaction to a product that is inhaled (breathed in) and will cause problems related to breathing, including:

  • Wheezing
  • Breathlessness
  • Tight chest and coughing
  • Runny or itchy nose
  • Watering eyes

Examples of substances that may cause sensitisation include:

  • Flour, dust, moulds
  • Latex Resins, glues and solder
  • Paints and lacquers
  • Sawdust
  • Antibiotics
  • Animal proteins, fur

Because of risks of sensitisation, and because some health issues can take a number of years to develop, health records of employees need to be retained by employers for at least 40 years.

Groups of people at high risk

Different groups of people within your business will have different levels of risk - for instance, an office worker may not be exposed to the same chemicals that a cleaner or machine operator could be - you will need to think about different groups and roles when undertaking a risk assessment, and we’ll talk you through this process in a later chapter.
Certain people are at particular risk of hazardous substances. This can often be relevant for a limited time only, but it is important to think about these types of people when you are considering the risks of exposure.

This group includes:

  • Young or new workers, who may be untrained
  • Pregnant women
  • People who are recovering from illness
  • Visitors to the business, who may be unfamiliar with good practice

Learning outcomes

Now you understand what ‘substances hazardous to health’ are and how they can harm individuals exposed to them:

  • You should be able to recognise some of the substances within your business that might cause harm.
  • You should be able to describe the different forms hazardous substances take, how they enter the body and some of the most common health problems they cause.
  • You should be able to recognise the difference between acute and chronic conditions, and know the meaning of ‘sensitisation’.
  • You should understand that risks are greater in certain groups of people and be able to identify these groups.
Click to go to Chapter 2 Practice Questions