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There is now a greater awareness of the dangers of lead and the need for risk assessments of lead hazard. However, guidelines are vague on how to measure the risk. Here we outline why we use dust wipe sampling to determine lead contamination.
What lead risk assessment should be carried out?
The Control of Lead at Work Regulations 2002 (CLAW) place a duty on employers to prevent or where this is not reasonably practicable, to control employee exposure to lead.
CLAW suggests that airborne lead levels should be checked regularly while working. Although, you could argue this is more relevant to factory environments, rather than building sites.
Common sense, and indeed some US studies, show that fine lead dust will drop out of the air within the hour. This dust will then settle on exposed surfaces and create a different lead hazard. One now more likely to be walked around or picked up on hands, rather than inhaled.
How can dust wipes confirm lead hazard?
Dust wipe samples are taken using a small fibre wipe. This is then analysed in a laboratory, by first dissolving it in acid. The analysers are very sensitive, registering tiny amounts of lead, but the thresholds are also very low (see below).
In 2019 the EPA reduced the domestic thresholds:
Floors down from 40 µg/ft² to 10 µg/ft²
Window sills down from 250 µg/ft² to 100 µg/ft²
Note that the units of measure are for American µg/square foot, while the Europeans use µg/30cm²
In the US, you cannot be in receipt of certain federal grants for renovations, unless you have the property clearance tested using dust wipes. The UK is currently someway behind this, not formally using these dust measurements, even in domestic properties. But, it makes good sense to have an idea of dust contamination, as incoming occupants deserve a pristine environment.
How can we use dust wipes?
Dust wipes can be used before work starts, to indicate whether you are inheriting a contaminated building. This is called baselining.
When work is completed, dust wipes can be used to show the client that you are handing back a building free of lead contamination. This is called clearance testing.
So, while destructive paint chip sampling or non-destructive XRF sampling can determine whether there is a passive lead paint hazard in situ, dust wipe sampling will reveal if there is a more active lead hazard, such as dust present.
Further information on lead legislation