There are many types of dust that can cause respiratory problems to workers on construction sites.
In all workplaces the Control of Substances Hazardous to Health Regulations 2002 state that dust levels must not exceed the Work Exposure Limit (WEL) specified for "dust of any kind".
The WEL has been set at 10mg/m3 total inhalable dust or 4mg/m3 respirable dust and this should not be exceeded.
These are limits placed on the amount of dust in the air, averaged over an eight hour working day. Notwithstanding these limits, employers must reduce exposure to dust to as low "as reasonably practicable".
For respirable crystalline silica dust, which emanates from construction processes involving set concrete or stone (kerb/block cutting, drilling, chasing, laying concrete rubble as hardcore) the work exposure limit is set as 0.1mg/m3 (which is 40 times less than the WEL for general dust).
Exposure to silica dust can cause Silicosis and Chronic Obstrusive Pulmonary disease. This interferes with air movement in and out of the lungs and causes breathlessness, often with a chronic cough and spuntum (phelegm).