If silica dust has a WEL of 0.1 mg m3 over 8 Hours......would chasing and drilling into walls in domestic properties for approx 15 minutes per day likely exceed this WEL. I notice there is no short term exposure limit in EH40! We provide engineers with RPE but the Client is now going down the path of health surveillance for employees that carry out this work. What are peoples thoughts?

hi zoltangera Its highly unlikely that drilling into a wall or chasing out will yeild this level of silica, you have to produce an awful amount of silica dust to generate those kind of readings however the problem is that you cannot tell by looking at it. There in lies the problem with silica its the dust you cannot see that is harmful to you - generally sub 5 micro. The use of the correct face mask should obviate nearly all the risk of dust particles entering the breathing zone. This means to get a quantitative assessment of dust make the only real way would be to undertake a series of personal samples - this should give you a true picture of risk - it will give you both particulate sizes and also content. You will be able to then give a quantitative estimate of dust make say 0.05 mg m3 and take the efficiency factor from the selected mask to prove beyond doubt that the WEL is not being exceeded. This will back up any assessment you give to client that utilises masks as a control. Also do not forget the face fit testing. The Occupational Health route is not a control but simply an early warning system - it first baselines all your staff in terms of lung function and ensures you capture if they have external habits that may affect lung function (smoking). Then it gives you a regular timebound assessment of that lung function so that if this is deteriorating that person can be redeployed. The assessments would probably be three - five yearly unless the OHN picked up problems then they can be reduced according to the advice given by the Occupational Health provider. Regards Martin