Geotechnical and
Environmental Services

Specialists in the investigation, assessment and reclamation
of development land.

Human Health

If land has been polluted, then assessing the potential impact on human health is always of concern. BRD's expertise in risk assessment can make sense of the numbers.

Once a soil sample has been analysed by a laboratory, the concentrations for up to a couple of hundred different chemicals are presented in a table.  How do we understand all these numbers?

The first step  to appreciate is that when assessing risk to human health from soil contamination it is considered on a suitable for use basis. In other words, whether the concentration of a particular chemical is of concern or not will depend upon what the land is to be used for. To some extent this is common sense, as most people can appreciate that a small child playing in a residential garden is a far more sensitive land use than an adult working in an office with limited landscaping.

For each broad category of land use and for over a hundred chemicals that are commonly tested for, government organisations and industry bodies have published what are called generic assessment criteria. These generic assessment criteria (GAC) may be called SGV (Soil Guideline Values), LQM CIEH GAC or CLAIRE AGS EIC GAC depedning upon their source.  There are also other consultancies that have developed their own GAC, but this is not something that BRD endorses as they do not always show how the values have been derived and so it is not possible for third parties to verify these values. If anybody quotes ICRCL numbers at you then they are well out of date!

In simple terms, if the concentration is above the appropriate GAC then the soil may present a risk to human health. In reality, the assessment is not as simple as a straightforward comparison of numbers with consideration of soil type, test method, statistical analysis, and professional judgement based on experience all required.

If a result does pose a potential risk to human health, it may be appropriate to undertake a more detailed  site specific quantative risk assessment. This commonly invloves employing the Contaminated Land Exposure Assessment (CLEA) model developed by the government to produce SGVs, but altered to employ different input parameters that are specific to the site. This technqiue can also be employed for chemicals for which no GAC exists.

Whatever the numbers are, BRD can advise you not only what they mean, but more importantly what you need to do.