Breathing in Hazardous Substances 

Thousands of workers each year are affected by breathing in hazardous substances in the workplace, with long term exposure seriously impacting their health and wellbeing.

There are three common routes for occupational exposure to hazardous substances:

• Inhalation by breathing in airborne contaminants into the lungs
• Ingestion by hand to mouth contact
• Absorption through the skin such as exposure to chemicals

The respiratory system provides the quickest and most direct route of entry, which can be attributed to the fact that the respiratory system has a direct relationship with the circulatory system.

It's estimated that the average person takes 12-20 breaths a minute, that's an average of 23,000 breaths a day¹. Our lungs allow us to sustain life in the most unusual circumstances and we only get one set in a lifetime, therefore it's essential we look after them.

The respiratory system is made up of organs and tissue that when breathing in, allows oxygen into the body and when breathing out, removes carbon dioxide out of the body.

The lungs contain two primary bronchi, divided from the trachea or windpipe, referred to as the bronchial tree. The bronchi then split into smaller branches known as bronchioles which end in tiny balloon-like air sacs called alveoli. Alveoli is responsible for the primary function of the lungs where oxygen and carbon dioxide is exchanged with the circulatory system.

How Does the Respiratory System Clean the Air?

Because your lungs are so vulnerable, the respiratory system has some defence mechanisms to keep harmful things in the air from entering the body. Hairs in your nose help filter out large particles and can be cleared out by sneezing. Smaller hairs, called cilia, can be found in your air passage, and move from side to side to help keep the passage clean. Breathing in harmful substances, such as cigarette smoke can damage the cilia which can stop working and lead to health problems. Cells in the trachea and bronchial tubes also make mucus that keeps air passages moist to help keep the likes of dust, bacteria and viruses out of the lungs.

Particulates can come in the form of dusts, fibres, mists, aerosols, fumes and microfibres and are less than the width of a human hair in size. Particulate size is measured in micrometres or "microns" (μm) with one micron being 1/1000^th of a millimetre.

Breathing in hazardous substances that have particles larger than 10 microns can be captured by the nose, throat and trachea. The body traps these with hair and mucus, clearing them by sneezing and coughing. However, particles smaller than 10 microns can pass directly into the lungs and bronchial tree, which is where damage to the respiratory system takes place and can be the start of developing respiratory illnesses.

Dusts, Fibres and Fumes

Excessive exposure to hazardous solid particulates in the form of dusts, fibres and fumes in the workplace can create life-threatening respiratory problems. Breathing in hazardous substances such as silica dust, welding fumes or wood dust can all pose health risks if control measures are not correctly in place. Here are just some of the more common hazardous substances that we've explored.

Liquid particles (made up of small droplets) in the form of fine sprays, mists and aerosols can irritate the eyes, skin and respiratory system. Some substances can expose workers to more than one hazard, for example spray painting can cause respiratory diseases by breathing in paint mist but can also be caused from inhaling solvent vapours too.

Workers can be exposed to a variety of micro-organisms depending on the environment they work in. Depending on the type of micro-organism, whether a bacteria or virus, and what work is being done can vary the level of risk.

Even smaller particles of less than 2.5 microns can pass into the areas of the lung in which oxygen is transferred. If we look at the micron scale, we find that these 10 micron and smaller particles are not even visible to the human eye and yet pose the greatest risk. This means you can't even see the hazard.

Gases - a substance or matter in a state in which it will expand freely to fill the whole of a container, having no fixed shape (unlike a solid) and no fixed volume (unlike a liquid)

Vapours - A substance diffused or suspended in the air; normally as a gas or extremely small drops of liquid that result from the heating or evaporation of a liquid or solid.