Introduction to Health and Safety at Work

Introduction to Health and Safety at Work
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into the body. These contaminants may be chem-
ical (e.g. solvents or welding fume) or biological (e.g. 
bacteria or fungi) and become airborne by a variety 
of modes, such as sweeping, spraying, grinding 
and bagging. They enter the lungs where they have 
access to the bloodstream and many other organs
➤
absorption through the skin
– the substance comes 
into contact with the skin and enters either through 
the pores or a wound. Tetanus can enter in this way 
as can toluene, benzene and various phenols
➤
ingestion
– through the mouth and swallowed into 
the stomach and the digestive system. This is not a 
signifi cant route of entry to the body. The most com-
mon occurrences are due to airborne dust or poor 
personal hygiene (not washing hands before eating 
food).
Another very rare entry route is by 
injection
. The abuse 
of compressed air lines by shooting high pressure air 
at the skin can lead to air bubbles entering the blood-
stream. Accidents involving hypodermic syringes in a 
health or veterinary service setting are rare but illustrate 
this form of entry route.
The most effective control measures which can 
reduce the risk of infection from biological organisms 
are disinfection, proper disposal of clinical waste Routes 
of entry to the human body (including syringes), good 
personal hygiene and, where appropriate, personal 
protective equipment. Other measures include vermin 
control, water treatment and immunization.
There are fi ve major functional systems within the 
human body – respiratory, nervous, cardiovascular 
(blood), urinary and the skin.
14.5.1 The respiratory system
This comprises the lungs and associated organs (e.g. 
the nose). Air is breathed in through the nose, passes 
through the trachea (windpipe) and the bronchi into the 
two lungs. Within the lungs, the air enters many smaller 
passageways (bronchioli) and thence to one of 300 000 
terminal sacs called alveoli. The alveoli are approximately 
0.1 mm across, although the entrance is much smaller. 
On arrival in the alveoli, there is a diffusion of oxygen 
into the bloodstream through blood capillaries and an 
effusion of carbon dioxide from the bloodstream. While 
soluble dust which enters the alveoli will be absorbed 
into the bloodstream, insoluble dust (respirable dust) 
will remain permanently, leading to possible chronic 
illness.
The whole of the bronchial system is lined with hairs, 
known as cilia. The cilia offer some protection against 
insoluble dusts. These hairs will arrest all non-respirable 
dust (above 5 
µ
m) and, with the aid of mucus, pass the 
dust from one hair to a higher one and thus bring the dust 
back to the throat. (This is known as the ciliary escalator). 
It has been shown that smoking damages this action. 
The nose will normally trap large particles (greater than 
20 mm) before they enter the trachea.