Why does the arsenic occur?
There are some areas of Daventry district where the natural geology consists of Northampton Sand with Ironstone. This ground may contain elevated levels of naturally occurring arsenic. Often these areas have been quarried or mined for ironstone in the past.
Is this a problem?
Arsenic is a naturally occurring material and in low concentrations should not cause any adverse health effects. However in this area it is sometimes present in concentrations above the guideline values set by the government.
There is a theoretical health risk from arsenic based upon the total levels found. However liaison with the Health Protection Agency has not revealed any evidence of people suffering health effects from living in this area. It may be that the chemistry of how arsenic is naturally fixed to other minerals within the soil (bio-accessibility) that explains that while it is present the health effects are less than could be expected.
It is not present in the soil at levels likely to lead to the acute effects often associated with arsenic poisoning.
Where is it found?
The general areas where it is found can be identified from a geological map. Small lumps of orange / brown stone are often evident in the soil. However the actual concentration that is present in the ground can only be determined by sampling the soil.
If Arsenic is in the soil how could it affect humans?
Arsenic in soil would be taken into the body via the mouth through direct ingestion, by eating vegetables grown in the soil and by eating soil attached to any vegetables eaten.
The first route is most significant for very young children who have a tendency to put soil and other objects into their mouths. Children are considered to be the most vulnerable group when carrying out assessments of risk from the presence of arsenic.
Many gardens are not large enough for residents to grow vegetables and this would reduce the risk. However for anyone who has a garden or an allotment on the affected soil these concerns apply, particularly if children have access.
What do you advise?
All development sites on potentially affected soil are required to carry out a risk assessment. The risk assessment will either prove that there is not a problem or identify that remediation works are required.
If you are buying a new house the developer can advise what steps they have taken to ensure the site doesn’t present a risk to the health of the sites end users.