Posted By Ken Taylor I'm sure that you are basically right and would even argue that some of your list are not particularly 'inert' - which is more to do with lack of chemical reaction than physical harm leading to disease.

Posted By Graham Sargeant Thanks again for all your comments, I must admit although I'm no expert I thought that the cement dust could be considered harmful. I think that section of my notes should be approached with caution.

Posted By Adrian Watson Graham, I would refer you to a good toxicology textbook such as Casarett & Doull's Toxicology or Principles of Toxicology Williams et al. Whilst all dusts should be controlled, not all exposures are harmful. The hazard posed by each dust depends upon the dose, its morphology, physical, chemical & toxicological properties and how the individual’s body interacts with it. Some dusts produce effects, such as iron that produces radiological opaque bodies, but does not appear to cause clinical disease. This type of dust was originally described as "nuisance dust". However in recognition of the fact that there are many dusts that have not been fully characterised and thus may cause disease this term is no longer used. Concrete dust is a complex mixture of substances. It is alkaline, hydroscopic & the particles tend to agglomerate when damp. It contains chromates; hexavelant chromium is a known lung carcinogen. The few studies carried out confirm that it effects the upper respiratory system, as is to be expected. However, no epidemiological studies have shown excesses of lung cancer. Another of the materials listed, smoke is definitely not a nuisance dust. Smoke is the product of burning carbonaceous materials. These materials contain known carcinogens. Epidemiological studies have consistently shown an excess of lung cancers in those exposed to smoke emissions. I hope that this is of some help. Regards Adrian Watson LLM MSc Dip Occ Hyg FBIOH ROH FIOSH RSP MCIEH

Posted By Jack and isn't clay dust silica which is certainly not harmless & from memory has an MEL of 0.3

Posted By Diane Warne Here's another interesting snippet on the subject of dusts! from the Guardian: The term monkey business has taken on a new meaning as hundreds of movie extras from Planet of the Apes sue Fox Entertainment for emotional distress. Fox Entertainment, a unit of Rupert Murdoch's News Corporation, faces lawsuits from the extras who say they were exposed to cancer-causing powder during the shooting of a dust storm scene in the remake of the 1968 classic. Court documents show the actors have filed a class action suit for fraud and deceit, battery and intentional infliction of emotional distress. The suit, first reported in the Hollywood Reporter, demands unspecified compensation and punitive damage and was filed in Los Angeles on Tuesday by Jeffrey Clark, representing other extras. The actors, who played apes and humans, claim they were exposed to around 80,000lbs of Fuller's Earth powder, containing - they say - a lung irritant and known carcinogen called crystalline silica. The scene was filmed over 10 to 12 days in a desert outside LA, during which the actors were exposed to the dust for six to eight hours a day without the use of face masks, which are recommended by the powder's makers, the suit said. In addition to compensatory and punitive damages, the extras are seeking any profits made from the movie, which was directed by Tim Burton.