Technically there is no safe exposure to asbestos and the official guidance would be never to scrape or sand artex unless tested.
But in reality we know that the body is better at clearing white asbestos than blue or brown.If you have damaged lungs e/g smoking paralyses the hairs that work like an escalator lifting dust to the back of the throat then you may be more at risk.
Asbestos causes a variety of lung diseases - asbestosis is similar to silicosis which you can get from long term exposure to industrial dusts and will cause progressive breathing problems and shortness of breath. We know that people who smoke and have significant asbestos exposure are *more likely* to develop asbestosis.
Mesothelioma is less linked to smokers and presents late because the tumor is pretty big and spreads by the time you get symptoms. There appears to be a genetic component - so just because two people have the same exposure it doesn't mean if one gets it the other will not (some wives of asbestos workers died of mesothelioma presumably from dusting their overalls, but not always their husbands).
Artex is a tricky one. Even if you chip or scrape top off the asbestos 1-2% is likely still bonded to the 'plaster' component of artex. Given that the artex mix was originally powder you would expect the greatest risk to be at mixing stage.
However if you sand it then you are much more likely to release millions of particles.
You don't want to expose home owners to ongoing risks especially children who appear to be much more susceptible.
If you think you have had a lot of exposure in the past particularly to lagging or other nasty types then a chest xray might reveal 'pleural plaques' which are an indicator of previous asbestos exposure that was not cleared- they are not a disease in themeselves but clearly you are more at risk of developing abestosis or mesothelioma if they are noted.
The idea that a single shard of asbestos can kill you needs to be taken with a pinch of salt as there are asbestos particles in the air we breathe in cities and even in the drinking water.
There have been studies into showers to see if the spray of water (which will have some asbestos in it) could end up in the lungs (probably not).
So..... after all that there seem to be a bit of luck or bad luck associated with say mesothelioma.
But why take any unnecessary risk. You have to assume that a single exposure to the blue/brown asbestos puts you at significant risk and white asbestos may do if you are unlucky with your genes.
There's no point worrying after exposure, you are still more likely to die of a fatal heart attack or suicide or a road traffic accident.
