Have you tried EH40/2005 Workplace exposure limits? That's usually my first check when looking into exposure levels

Alan

I found "Protection of workers and the general public during development of contaminated land" on the HSE website - which (as usual) gives some good general guidance & asks the employer to risk assess the situation. There is a table at the end of that document that gives "Guidelines for classification of contaminated soils - suggested range of values (parts per million) on air dried soils, except for pH"

Taking 2 examples from that table for Arsenic & Cadmium

e.g. Parameter Typical values:
For uncontaminated soils Arsenic (0 to 30 ppm) & Cadmium (0 to 1 ppm)
Slight contamination Arsenic (30 to 50 ppm) & Cadmium (1 to 3 ppm)
Contaminated Arsenic (50 to 100 ppm) & Cadmium (3 to 10 ppm)
Heavy contamination Arsenic (100 to 500 ppm) & Cadmium (10 to 50 ppm)
Unusually heavy contamination Arsenic (>500 ppm) & Cadmium (>50 ppm)

EH40 (also published by HSE) gives a WEL Long Term 8 hours etc. etc. for Arsenic of 0.1mg/m3
- no ppm value or short term WEL specified
EH40 (also published by HSE) gives a WEL Long Term 8 hours etc. etc. for Cadmium of 0.025mg/m3
- no ppm value or short term WEL specified

There seems to be some water industry trigger values of Arsenic of 40mg/kg & Cadmium of 20mg/kg - whereby if this trigger value is exceeded we ask the client to remove the soil before we dig.

As you can see from the above the 3 guidelines are as clear as mud to me.

A typical dig may last 1 to 2 days so complicated laboratory analysis of exposure levels is deemed impracticable. Exposure levels will vary depending on weather - wind / rain and depth of excavation.

I want to give practical advice to our designers as to what values of contamination should trigger us to take action.

EH40 is mainly about inhalation risks and relates to concentrations in the atmosphere, which is why the values mentioned are ‘clear as mud’, evans38004.
The HPA information might be useful but you need to get a handle on what was on the site before. I have heard of allsorts of things being left in the ground from, chemicals like benzene, to old leather and animal skins( which might be contaminated with anthrax!) , to radioisotopes and even old gas cylinders.
As the number of things that you might come across on contaminated land is so wide there is no single set of guidance that you can use. Nor are there any trigger levels such as you get for inhalation risks with EH40. It is down, unfortunately to a risk assessment.

Thanks Jay - that link does give me another resource - albeit very vague again.

Thanks John - we are aware of the documents you stated & the various range of chemicals.

Thanks Kurdziel - as above, but we still do not understand how we can do a proper COSHH risk assessment?!?

Typical scenario:

House builder (client) wants to build new housing estate & as he contacts us to put water pipes in for human consumption. He / we walk the green/brownfield site & may notices a few patches of smelly/dirty soil. As a matter of course we ask the client to have some soils samples taken of the site and to send us the results with some history of the site for our contaminated soil risk assessment (this has 70+ common chemicals). We use the data to (i) the determine the types of pipes to use/not use and (ii) help us do the risk assessment. The data received is in mg/kg, but as mentioned previously the trigger levels for the pipe (landfill directive etc) is wide of the range for the COSHH assessment - take my Arsenic example previously whereby the contaminated soil trigger levels for laying a pipe (leaching) is 40,000mg/m3 and the EH40 inhalation WEL is 0.1mg/m3.

Based on this type of data - how do we do a valid COSHH assessment & protect the health of our employees in the filed?