In reply to BolderLicious:
The main key health risk drivers with a climbing wall scenario would be:
1. The nuisance/irritant issues associated with Inhalable Dust [HSE term] (total airborne dust/particulate-matter[PM]) from all dust sources
2. Chronic (long term) health risks associated with respirable dust [HSE term] (typically taken as the PM10 fraction of inhalable dust). The finer PM2.5 fraction is typically thought to be of most concern.
3. Chronic health risks associated with substances in the PM10 fraction, which would include substances in climbing chalk (primarily MgCO3)
I'd expect acute risk associated with 1 & 2 to be negligible (when compared with the chronic risk).
The primary sensitive receptors would be:
1. Workers at the wall
2. Users of the wall
There is a legal duty (Health & Safety at Work Act etc) on employers to protect the health safety and welfare of workers and the public (which would include wall users).
The main workplace H&S regulation (relevant for workers at a business such as a wall) that covers dust is COSHH (Control of Substances Hazardous to Health Regulations), which uses a set of legally binding Workplace Exposure Limits (WELs) laid out in EH40 (most recently updated in 2011):
http://www.hse.gov.uk/pubns/priced/eh40.pdf
Under COSSH/EH40, dust levels would become legally unacceptable for a workplace at the following concentrations:
- Inhalable dust 8 Hour TWA (time weighted average): 10 mg/m³
- Respirable dust 8 Hour TWA: 4 mg/m³
EH40 also contains a number of dust WELs for specified substances, but not currently MgCO3(though CaCaO3 is listed and uses the same 10 & 4 mg/m³ WELs). There are also 5 WELs for different types of silica/silicon dust. Although there is a WEL for 'rubber process dust', this does not apply to dusts arising from the abrasion of cured rubber and the general dusts WELs should be adopted for dust containing abraded rubber.
It wouldn't be best practice to automatically adopt WELS for users of the wall (essentially an 'involuntary risk' to a member of the public) and this would be a good topic of discussion with the HSE and Health Protection Agency (HPA). My view is that it would probably require a separate assessment to demonstrate acceptable risk to users, given the lower level of acceptable risk typically afforded to the public, compared with workers. For example, the UK PM10 air quality standard is 0.05 mg/m3 (2 orders of magnitude lower than the WEL)
However, if the wall levels are below EH40 levels, then I'd be surprised if a typical user would be at unacceptable risk (from a HPA standpoint, not a climbers world view) given the relatively limited exposure time for most wall users. Wall rats 'may' be a different issue (again, from a HPA standpoint).