I've got some guys in the back garden cutting up the concrete with an angle grinder. The dust is just hanging in the air around them - most strange... 
[serious mode on] There are major concerns in the construction industry about silicosis, this is going to be the new asbestosis and strike many many more people. Stone cutting is the one that will get most, cos most do it
Silicosis
The commonest form of pneumoconiosis is due to the inhalation of free silica.
Free silica (SiOČ) or chrystalline silica occurs in three common forms in industry: quartz, tridymite and cristobalite. A cryptocrystalline variety occurs in which the 'free silica' is bound to an amorphous silica (non-crystalline). It includes tripolite, flint and chert. Diatomine is the most common form of amorphous silica capable of producing lung disease. Some of these forms can be altered by heat to the more dangerous crystalline varieties such as tridymite and cristobalite.
e.g.
Quartz 800°
Cryoptocrystalline
Tridymite
Cristobalite
Amorphous
Lung reaction
Industrial exposure occurs in mining, quarrying, stone cutting, sand blasting, some foundries, boiler scaling, in the manufacture of glass and ceramics and, for diatomite, in the manufacture of fluid filters. Particles of free silica less than 5 mm in diameter when inhaled are likely to enter the lungs and there become engulfed by scavenging cells (macrophages) in the walls of the tiniest bronchioles. The macrophages themselves are destroyed and liberate a fluid causing a localised fibrous nodule which will obliterate the air sacs. The nodules are scattered mainly in the upper halves of the lungs. They gradually enlarge to form a compressed mass of nodules. Sometimes a single large mass of tissue may occur, known as progressive massive fibrosis. If much of the lung is affected the remaining healthy tissue is likely to become over distended during inhalation.
Symptoms
There are no symptoms in the early stage. Later the initial complaint is of a dry morning cough. Next occurs some breathlessness, at first noticeable on exercise but, as destruction of the lung tissue proceeds, breathlessness worsens until it is present at rest. The interval between exposure and the onset of symptoms varies from a few months in some susceptible individuals to, more usually, many years, depending on the concentration of respirable free silica and the exposure time at work. Silicosis is the one form of pneumoconiosis that predisposes tuberculosis, when additional symptoms of fever, loss of weight, bloody sputum may occur. In the presence of gross lung destruction the blood circulation from the heart to the lung may be embarrassed and result in heart failure.
Diagnosis
This depends on a history of exposure and, in the early stages, a chest X-ray showing tiny radio opaque nodules and, later, a history of cough and breathlessness and sound in the chest detectable with a stethoscope. Lung function tests may be helpful, but usually not until the late stages.
Medical surveillance
Where exposure to free silica is a recognised hazard, a pre-employment medical is advised, which should enquire into previous history of dust exposure, of respiratory symptoms, with examination of the chest, lung function testing and chest X-ray. The medical should be repeated periodically as circumstances may demand.
Prevention
Reduction of the dust to the lowest level practicable and where necessary by the provision of personal respiratory protective equipment. [serious mode off]
