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Guidance for development, or change of use, on land falling within the target area for lead (Pb) contamination

December 2007

DDDC Policy for development within the target area for lead (Pb) contamination v2

1. Aim The aim of this guide is to provide an overview of the current situation regarding development on land containing elevated soil lead (Pb) concentrations in Derbyshire Dales. Land contamination is usually the result of previous land use(s) or may, in certain cases, be due to contaminants being present due to natural geological conditions. This guide is primarily intended for developers or those applying for a new residential development within the District. It should be read in conjunction with the Guide for Developers, produced by the Derbyshire Contaminated Land Working Group. It remains the responsibility of the developer, and their consultant, to design, propose and undertake a suitable site investigation, risk assessment and remediation options. This guide is solely designed for use in developments within Derbyshire Dales, in areas of naturally occurring lead. It is not designed to be used by any consultant or developer to justify the alteration of the Soil Guideline Value for lead in any other area.

2. Lead: Elevated background concentrations in Derbyshire In Derbyshire, lead concentrations in soils are frequently elevated above the national average. This is primarily due to the natural underlying geology, with lead mineral veins being enclosed within the carboniferous limestone that underlies much of Derbyshire Dales.

Additionally, there will be manmade contributions to these already elevated background concentrations, arising from historical lead mining and smelting within the District. The number of former metalliferrous mines within the District is large, with the majority located in the northern part of the District. Lead mining ceased in the late 1800’s, and the majority of mines are now capped and spoil heaps are covered by vegetation. The principle ore mined was lead sulphide (PbS), also known as Galena. Today the main supply of lead comes from overseas, or from the recycling of lead.

A survey of soils in England and Wales by McGrath and Loveland (1992) reported lead concentrations ranging from 3 to 16338 mg/kg, with a median value of 40 mg/kg. Data supplied by the Geochemical Baseline Survey of the Environment (G-BASE) project, run by the British Geological Survey, reports average top soil (0 - 150 mm depth) lead concentrations in Derbyshire Dales of 996 mg/kg (median 314 mg/kg) and sub soil (300 - 450 mm depth) lead concentrations of 470 mg/kg (median 140 mg/kg). The highest recorded concentrations for top soil and sub soil were 35930 mg/kg and 24700 mg/kg respectively.

Through combining data arising from the Council’s inspection strategy, historical land uses, geological maps, and data supplied by the British Geological Survey the Council has identified a “target area” with respect to soil lead concentrations. This area is where the Council considers that soil lead concentrations are likely to exceed Government guidelines for lead in soil of 450 mg/kg, and may pose a risk to human receptors. Lead concentrations averaged solely within the “target area” discussed above have a mean top soil concentration of 1384 mg/kg and a mean sub soil concentration of 849 mg/kg.

The fate of lead in soil is determined by numerous factors, including soil pH, organic matter and the chemical and physical form of the lead compounds. Most lead is strongly retained in soil, with the bioavailability to plants and young children generally regarded as being low (DEFRA & Environment Agency 2002a). The absorption of lead ingested with food stuffs is

2 DDDC Policy for development within the target area for lead (Pb) contamination v2 around 5% for adults, although absorption is thought to be close to 50% for young children (DEFRA & Environment Agency 2002a).

3. Implications for development control Potentially contaminated land is an important planning consideration for any development, or change of use. The Council has identified a “target area” for lead, as discussed previously, which has resulted in extensive areas of the northern part of the District being identified as a site of potential concern with respect to soil lead contamination and the risks this may pose to human health. No bioaccessibility tests (see Section 6) were undertaken as part of this investigation.

For developments such as new buildings (residential and commercial), barn conversions to residential use or the creation of allotments within the “target area” for lead, the Council will require that a simplified Phase II site investigation is undertaken as a condition of any planning permission that is granted. In cases where the only contamination of concern is naturally occurring contaminants, no desk study (Phase I) will be required. Broad details of what a full Phase II report should include can be found in the Guide for Developers, produced by the Derbyshire Contaminated Land Working Group.

However, for the purposes of a Phase II site investigation solely to assess the risks posed by naturally occurring lead, the Council will accept a simplified site investigation report. This site investigation should focus on metalliferrous contaminants and at a minimum the report should contain:

• Justification for the location, depth and number of samples taken • A plan showing sample locations • A summary of the results of the soil chemical analysis, placed in the context of the current Soil Guideline Value (SGV) for lead (Section 4) and the Council SGV for naturally occurring lead (Section 7) • A statement of the risks posed by the concentration of the soil contaminants, based on the contaminant source - pathway - receptor model • Recommendations for remediation (if appropriate)

The Council considers that development on land that has elevated soil lead concentrations has the potential to affect receptors (e.g. residents or site users) via the pathways of inhalation, ingestion and plant uptake. Depending on the resulting concentrations of metalliferrous contaminants in the soil at the site of the proposed development, an appropriate remediation strategy will need to be agreed with Development Control (or the Planning Department at the Peak District National Park) and the Environmental Health Section of Derbyshire Dales District Council.

4. Soil Guideline Values (SGVs) Soil Guideline Values (SGVs) have been designed to represent “intervention values” for a range of different contaminants, above which further site assessment is likely to be required. They replace previously used ICRCL “trigger values”. All site investigations, remediation and validation reports are expected to take account of the currently published SGVs in assessing soil contaminant levels as part of the overall risk assessment. Soil Guideline Values mark the concentration of a substance (e.g. lead) in soil at, or below which human exposure can be considered to represent an acceptable or minimal level of risk, and are designed to be

3 DDDC Policy for development within the target area for lead (Pb) contamination v2 inherently conservative. They are solely designed for human health risks, and do not consider animals or the wider environment.

The SGV for lead (SGV 10; DEFRA & Environment Agency 2002b) is based on a blood lead concentration. The SGV is calculated to ensure that uptake of lead from soil, taking into account sources of lead other than soil and dust, in the general population, will not result in a blood lead concentration above 10 µg dL -1. This is the amount of lead in micrograms for each 100 millilitres of blood. The SGV applies to soil lead concentrations regardless of the origin of the lead. The UK Government considers that there is a minimum standard of health protection for all individuals, hence the inclusion of naturally occurring contaminants in the contaminated land regime. The standard SGVs for lead, for different land-use categories are presented in Table 1. Exposure to lead via the soil can arise via a number of pathways. The most likely exposure routes are presented in Table 2.

Table 1. Soil Guideline Values for lead as a function of land use Standard land-use Soil Guideline Value (mg/kg dry weight soil) Residential with / without plant uptake 450 Allotments 450 Commercial / Industrial 750 Reproduced from SGV 10

Table 2. Contribution to total exposure from soil for the relevant pathways expressed as a percentage of the mean exposure calculated by the CLEA model Exposure pathway Contribution to exposure from soil according to land-use (%) Residential with plant Residential without Commercial / uptake, and plant uptake Industrial allotments Ingestion of soil and 71 100 100 indoor dust Consumption of 22 - - home grown vegetables Ingestion of soil 7 - - attached to vegetables Inhalation of soil and <0.1 <0.1 <0.1 indoor dust Reproduced from SGV 10

5. Exceeding the Soil Guideline Value (SGV) for lead Consideration should be given to the results of the mean value test for lead when interpreting the results of soil lead concentrations and, where appropriate, the maximum value test (DEFRA & Environment Agency 2002c). If the results of a site investigation show that the mean value test for lead is failed, this may indicate that the soil lead concentrations pose a risk to human health.

4 DDDC Policy for development within the target area for lead (Pb) contamination v2 However, exceeding the SGV for lead is not a clear cut situation since SGVs are not used as cut off values above which remediation will automatically be required. At the current time, their use remains as a guide at the discretion of the Local Authority. Whilst soil contaminant concentrations below an SGV expose the public to what is considered an acceptable risk, exceedance does not correspondingly equate to an unacceptable risk. Indeed, recent Government guidance has suggested that exceedance of an SGV would not necessarily satisfy the legal test of “unacceptable risk” in a court of law (DEFRA 2005). Furthermore, the contaminated land regime does not differentiate between naturally occuring contaminants and anthropogenic (man-made) contaminants, and to date no guidance has been issued concerning land with naturally elevated concentrations of contaminants.

Naturally elevated concentrations of contaminants exceeding SGVs are also found in other areas of England, including soil arsenic levels in parts of Northamptonshire and Cornwall. Ultimately what constitutes an unacceptable risk to human health can only be decided on the basis of a site specific risk assessment that, in the case of lead contamination, may take into account bioavailability or bioaccessibility testing.

6. Bioaccessibility and bioavailability testing The Council will consider site-specific arguments when assessing exceedences of the SGV for lead. Such arguments should be scientific, and based on chemical analysis of the soil in question. Under certain circumstances the Council will consider the results of bioaccessibility tests such as the Physiologically Based Extraction Test (PBET) or Simplified Bioaccessibility Extraction test (SBET), which can be used to indicate whether or not the contaminant is present in a bioaccessible / bioavailable form and thus likely to present an unacceptable risk to human health. The oral bioaccessibility is the fraction that is soluble in the gastrointestinal tract, whereas bioavailability is the fraction of a chemical that can be absorbed by the body, through the gastrointestinal system, the skin and the pulmonary system, into the blood. Currently there is uncertainty regarding the robustness and repeatability of bioaccessibility tests, and as such the results should be treated with caution. Full details of any methodology used, and its associated assumptions will be required. Environment Agency guidance on the use of bioaccessibility testing can be found at: http://www.environment- agency.gov.uk/subjects/landquality/113813/1283985/?version=1&lang=_e

The Council will not accept results from leachability tests as evidence of reduced bioavailability. A reduction in apparent solubility within a particular solution is not considered reliable evidence of a reduction in bioavailability to the human body.

7. Interpreting the results of soil sampling When setting the residential SGV for lead two models were used to compute the SGV, one for adults and one for children. The worst case scenario exposure is that of children being exposed to soil borne lead. When calculating the residential SGV for lead the SEGH (Society for Environmental Geochemistry and Health) model was used, which is based on the response of blood lead in children. One of the key parameters (delta; δ) in the model is the variable derived from the observed empirical relationship between blood lead concentrations in children and exposure to soil and non-soil sources. The default delta value used when calculating the residential SGV for lead used is 5 µg/dL per 1000 µg/g. However, a range of values were considered to be acceptable for the model, ranging from 2 to 5 µg/dL per 1000 µg/g, depending on the particular situation. It was suggested that a delta value of three related to lead arising from mining contamination, due to its low 5 DDDC Policy for development within the target area for lead (Pb) contamination v2 bioavailability and a value or two if there is well-maintained vegetative cover. By using the value of two in the SEGH model the resulting residential soil guideline value for children, the most sensitive receptor, would be 1155 mg/kg. This is a similar value to that used by the United States Environmental Protection Agency (USEPA) for their Residential Lead Hazard Standards (TSCA Section 403), which is 1200 mg/kg for children’s play areas that are not bare soil (i.e for paved or grassed play areas).

To reflect the fact that the majority of soil lead contamination in the district is naturally occurring, or has arisen from mining contamination, and that gardens typically have well-maintained vegetative cover, soil lead concentrations (mean value test) less than 1155 mg/kg will not be required to be remediated for new developments. Soil lead concentrations above 1155 mg/kg will require remediation, or further evidence from bioaccessibility testing as part of a site specific risk assessment to evaluate the potential risks from soil lead concentrations above this value.

This guide is solely designed for use in developments within Derbyshire Dales, in areas of naturally occurring lead. It is not designed to be used by any consultant or developer to justify the alteration of the Soil Guideline Value for lead in any other area.

8. Remediation options The Council will consider all remediation or risk management options proposed by the applicant, their agent or consultant. It is considered that a remediation option for one site will not necessarily be suitable for a different site, and as such no single remediation option can be recommended.

9. Future work The Council is currently developing its strategy for investigating, and managing, any health risks that might be posed by exposure to naturally occurring soil borne lead. Consequently the view of the Council concerning acceptable soil lead concentrations in residential and commercial developments, and the role of bioaccessibility testing, will evolve through time as new guidance or techniques become available. Ultimately SGVs remain a guide, and it is at the discretion of an individual Local Authority to adopt their own position on what is deemed “unacceptable intake” and how to appropriately manage the risks posed by contaminated soils.

10. References Department for Environment, Food and Rural Affairs (DEFRA). (2005). Soil guideline Values and the Determination of Land as Contaminated Land under Part IIA. CLAN 2/05.

Department for Environment Food and Rural Affairs (DEFRA) and Environment Agency (EA) (2002a). Contaminants in Soil: Collation of Toxicological Data and Intake Values for Humans. Lead. R&D Publications. TOX6.

Department for Environment Food and Rural Affairs (DEFRA) and Environment Agency (EA) (2002b). Soil guideline values for lead contamination. R&D Publications. SGV10.

Department for Environment Food and Rural Affairs (DEFRA) and Environment Agency (EA) (2002c). Assessment of risks to human health from land contamination: An overview of the development of soil guideline values and related research. CLR 7. 6 DDDC Policy for development within the target area for lead (Pb) contamination v2

McGrath, S.P. and Loveland, P.J. (1992). The Soil Geochemical Atlas of England and Wales. Blackie Academic and Professional, Glasgow.

11.Additional information NERC Research Facilities http://www.nerc.ac.uk/using/capability/details.asp?cap=310&l2=52

Environment Agency SGV and TOX reports http://www.environment- agency.gov.uk/subjects/landquality/113813/672771/675330/?version=1&lang=_e

In-vitro methods for the measurement of the oral bioaccessibility of selected metals and metalloids in soil. R&D Technical Report P5-062/TR/01. Environment Agency 2002. http://www.environment-agency.gov.uk/commondata/acrobat/p5_062_tr01_1284167.pdf

Environment Agency’s Science Update on the use of Bioaccessibility Testing in Risk Assessment of Land Contamination. Environment Agency 2005. http://www.environment-agency.gov.uk/commondata/acrobat/science_update_1284046.pdf

Environment Agency Land Quality web pages http://www.environment-agency.gov.uk/subjects/landquality/113813/1283985/?lang=_e

Health Protection Agency http://www.hpa.org.uk/chemicals/compendium/Lead/

CLEA - Frequently Asked Questions. Oct 2003 http://www.environment-agency.gov.uk/commondata/103599/Q07

12. Contact details For further information please contact:

Pollution Control Officer Environmental Health and Housing Section Community Services Department Derbyshire Dales District Council Town Hall Matlock DE4 3NN

Tel: 01629 761227 Fax: 01629 761165 Email: [email protected]

7 DDDC Policy for development within the target area for lead (Pb) contamination v2

Printed by Community Services (Public Health and Housing Section) and published by Derbyshire Dales District Council, Town Hall, MATLOCK, Derbyshire DE4 3NN.

This leaflet is available free of charge in electronic, audio, Braille and large print versions, and in other languages on request. For assistance in understanding or reading this document please call 01629 761212.

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