Contamination in soil is often something we think of as being on an industrial scale, however, the soil in your garden can be contaminated, and can potentially impact the health of you and your family.
Modern housing developers and other bodies pay hundreds to thousands of pounds to make sure gardens in new properties, and the parks that surround them, are safe for use and in accordance with modern standards.
As the standards are relatively 'modern', most historical properties have never had such consideration and, therefore, many gardens and allotments built before this time may be unsuitable for their use in comparison to modern developments.
Soil Check can help you look into this and see if the soil you sample from your garden or allotment is safe!
History of Contamination
Land contamination has occurred throughout history. The very formation of the Earth has led to the creation and build-up of certain elements and compounds that, although naturally occurring, can pose a risk to the environment and also to us as humans.
The evolution of humans and our industrial practices have also led to the manufacture of numerous new chemical compounds, many of which also pose a risk to human health. Often as part of this, the naturally occurring contaminants have been abstracted, concentrated and utilised on massive scales worldwide. Heavy metals and hydrocarbons are an example of this.
From the use of lead in water pipes in Roman times, to iron foundries during the Victorian era, coal for locomotives, and the relatively modern use of hydrocarbons in trains, cars and planes, humans have affected the land around us. Of particular concern is the effect this has had on the land that we live on and often eat from.
One issue with land contamination is that it is often not visible, particularly when contaminants have slowly built up and interacted with other chemicals over time. Particles released from factories, highways, train lines and other industry travel with the direction of the prevailing wind and fall out of the air. Slowly over time this can change the shallow soils around us in our gardens and allotments. More acute contamination such as discarded fuels and chemicals, or building materials such as lead paint, asbestos and other commercial materials may also exist.
The land that homes are built on may also have been contaminated through previous use before the homes were constructed. Historical maps provide an insight into how the land around us has rapidly developed and changed from one economically beneficial use to another over time. Land within inner towns and cities has become more valuable for residential housing and as a result industry has moved further from the historical centres. The land blighted by the historical contamination source is then developed for residential use.
Whether it be gas works, power stations, landfills, or an old tannery, it is likely that all of us within towns, cities and some villages have been near former land uses that may have caused land contamination. This can also include road, railways, airports and other everyday bits of life that we take for granted.
Whilst in the countryside you may consider yourself to be far enough away from polution, however, prevailing winds can mean you may have been affected by factories in cities producing contamination that is blown on the wind.
Chernobyl is an extreme example of this on an international scale. It is an incident that everyone recognises and one that has had an impact on the United Kingdom from over 1,000 miles away. The atmospheric conditions, wind direction and the severity of the incident, led to radioactive material being deposited in the north and caused numerous issues: Click to view UK Parliamentary research document
Whilst thankfully not common, it does demonstrate that actions a long way away can have a significant affect locally.
The Science of Contamination
What is clear is that the soil in our gardens or allotments can have a significant and potentially long-term impact on our health if it contains certain contaminants. The soil can affect us in several ways:
Through the consumption of vegetables that have been grown in the soil. Vegetables may have accumulated contaminants from the soil that, if ingested, are introduced into our bodies.
Through the accidental ingestion of soil when gardening, playing or working in the soil and then eating or drinking without properly cleaning hands.
Through breathing in soil dust and/or particulates when gardening, playing or working in the garden. The dust and particulates can also be taken into the house on shoes and clothing that fall off and persist as dust in the house.
Over time the exposure models that have been developed by the scientific community have shown that low-levels of certain contaminants can have a cumulative effect on humans. We all know eating lead would be bad for us but small doses over a number of years can build up, just as poor dietary choices may lead to poorer health, for instance eating too much red meat, fatty foods, burnt food or regularly drinking alchohol.
The scientific models that land contamination risk assessments are built upon make assumptions on the anticipated length of exposure (i.e. the time spent gardening, playing, or working etc.) and how much soil dust is likely to be breathed in, or how much may be ingested from home-grown vegetables or dirty hands etc. The models then derive the ‘Generic Assessment Criteria’ which specify how much of a particular contaminant in soil is acceptable for a particular land use (i.e. residential gardens, allotments, parks, and industrial). Numerous bodies and organisations have developed and published their own Generic Assessment Criteria. Whilst there is some variation between the different sets of criteria, in general, they are relatively similar and accepted by the scientific community.
As science has evolved, the models have been refined and the acceptable levels have been adjusted accordingly. We can be sure that these models will continue to be augmented, therefore, what is acceptable now and, in the future, may be different.
Soil Check Interpretation
Soil Check compares levels of some of the most common potential contaminants within your soil samples against the most up to date and current scientifically derived Generic Assessment Criteria. Soil Check have adopted the Land Quality Management (LQM) Suitable for Use Levels (S4UL) as the values used for comparison, although other criteria do exist.
The process of how these models were developed is complex and further details can be found following the below links. In general, the models are based on the Environment Agency’s Contaminated Land Exposure Assessment (CLEA) tool, which takes into account numerous variables such as contaminant type, exposure time, and who is at risk, to derive the criteria.
Over time planning laws began to consider the science outlined above. This has meant that new developments, including homes, schools, parks, industrial estates etc., all need to be constructed not only to Building Regulations for the structures but also with suitably clean soils for use in gardens and communal spaces. This has reduced the risk from potentially contaminated soils.
Examples of how the United Kingdom Government and the National House Builders Council (who are the warranty provider for many new developments) review this are below.
Undoubtedly, the inclusion of such standards as part of planning conditions and warranties for new developments has helped enormously to reduce the risk, however, some challenges still persist.
The development and implementation of land contamination risk assessment generally began in the latter part of the 20th century. Whilst land contamination regulation through the planning regime is good, hundreds of thousands of homes and allotments were built in the United Kingdom before such regulation. For example, the terraced houses of the Victorian era were usually built close to industry, including on former worked land such as coal fields. Therefore, these older properties almost certainly have a higher potential to be affected by land contamination than newly built homes.
Whilst Building Regulations and warranty providers set a minimum standard for new homes, and the planning regime also supports this, the cost of making gardens and communal spaces safe is often significant, especially when developing brownfield sites (i.e. land associated with former industrial use and typically within towns or cities).
Developers of modern sites may need to import topsoil and/or subsoil for use in gardens and communal spaces. The source and quality of which may be impacted by budget constraints. In some cases, developers will import clean naturally occurring soil from another development site that has an excess, therefore, the clean soil is transferred from one site to another (following certain protocols and legislation). However, if such soil is not readily available at the time, developers may turn to manufactured soils processed and/or blended multiple sites to produce a ‘product’. This is undertaken in accordance with standards, and in most cases will be suitable for its intended use, however, the mixing and blending of soils and former wastes into new materials can lead to unintended inclusions.
The volume of laboratory testing of new developments built on contaminated land is likely to be based on low frequencies. Typically, regulators and warranty providers will require only the soil in one out of four gardens to be sampled and tested to ensure it is safe for use. Best practice necessitates this to be conducted by a third-party and on a random basis, which reduces the likelihood of foul play, however, not all gardens are tested.