Introduction to Health and Safety at Work

Respirable dust
tends to be long thin particles 
with sharp edges which puncture the alveoli walls. The 
puncture heals producing scar tissues which are less 
fl exible than the original walls – this can lead to fi brosis. 
Such dusts include asbestos, coal, silica, some plastics 
and talc.
Acute effects on the respiratory system include 
bronchitis and asthma and chronic effects include fi brosis 
Figure 14.2
The upper and lower respiratory system.
Pharynx
Epiglottis
Larynx
Trachea
Left primary br onchus
Ribs
Base of left lung
Aorta
Vertebral column
Nose
Right lung
Bronchiole
Alveoli
(air sacs)
Inferior
vena cava
Apex
Apex
Heart space
Diaphragm
Apex
Apex
Heart space

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Chemical and biological health hazards and control
227
and cancer. Hardwood dust, for example, can produce 
asthma attacks and nasal cancer.
Finally, asphyxiation, due to a lack of oxygen, is a 
problem in confi ned spaces particularly when MIG (metal 
inert gas) welding is taking place.
14.5.2 The nervous system
The nervous system consists primarily of the brain, the 
spinal cord and nerves extending throughout the body. 
Any muscle movement or sensation (e.g. hot and cold) is 
controlled or sensed by the brain through small electrical 
impulses transmitted through the spinal cord and ner-
vous system. The effectiveness of the nervous system 
can be reduced by 
neurotoxins
and lead to changes in 
mental ability (loss of memory and anxiety), epilepsy and 
narcosis (dizziness and loss of consciousness). Organic 
solvents (trichloroethylene) and heavy metals (mercury) 
are well-known neurotoxins. The expression ‘mad hat-
ters’ originated from the mental deterioration of top hat 
polishers in the 19th century who used mercury to pro-
duce a shiny fi nish on the top hats.