Characteristics
Dioxins and furans are organic compounds that are harmful to human health. Chemically they are classed as halogenated aromatic hydrocarbons and are commonly produced by combustion of fossil fuels and incineration of municipal waste. They are also produced as a by-product of pulp and paper bleaching as well as in the production of other chemicals.
Gateshead lies across the River Tyne from the Byker incinerator. Ash from the Byker incinerator, found to be contaminated with dioxins, was spread on footpaths in allotments and other places in Newcastle upon Tyne, leading to an Environment Agency prosecution in the early years of this century.
Although studies showed dioxins from Byker ash were not present in Gateshead, other dioxin mixtures, dominated by furans, were discovered in Saltmeadows Riverside, Gateshead, and are thought to be present in waste materials produced by Gateshead's alkali chemical industry.
Hazardous properties
Dioxins and dioxin-like compounds cause conditions including:
- chloracne
- immune system suppression
- cancer
- reproductive and developmental toxicity
The potency of various dioxin compounds can vary over orders of magnitude.
Individual dioxins and furans are called congeners and are assigned a toxic equivalency factor (TEF) based on comparison with the most potent congener, which is 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD) (Environment Agency (2009)).
Pathway
Harm to human health can occur by eating or touching soil contaminated with dioxins or eating fatty fish fed on a diet containing dioxins.
Occurrence
In the past in Gateshead, the Saltmeadows area was a known source of dioxin-contaminated soils. BGR_calc includes an area known or suspected to have been affected by dioxin contamination. The area is associated with Christian Allhusen's chemical works that covered some 137 acres and had a kilometre-long river frontage. Allhusen's was a leading manufacturer of soda ash and crystals, bleaching powder and, later, sulphuric and hydrochloric acids.
Natural occurrences
Dioxins are a by-product of chemical manufacturing and waste incineration. There is no evidence they occur naturally in Gateshead.
Site investigation
Desk study
An understanding of the historical, industrial use of land and its vicinity is important in order to recognise the likelihood of dioxin soil contamination and to inform an appropriate soil sampling strategy. Sites within the BGR_calc dioxin-affected area should be investigated for dioxin contamination by specialist consultants.
Walkover
- Normal health and safety precautions should be taken.
- Dioxin-contaminated soil is not identifiable by eye.
Intrusive site investigation
Analysis of soil for dioxins is expensive, therefore carefully targeted sampling and analytical strategies are needed to ensure costs of investigation are controlled.
Foundations
Not relevant.
Remediation
Pathway interruption
Isolating dioxin-contaminated soils beneath a sufficiently thick and well-marked capping layer prevents human contact with the dioxins but does not prevent re-exposure of the soil by burrowing animals.
Source removal
Excavation and off-site disposal of dioxin-contaminated soil is a simple and widely used remediation technique.
Waste disposal
Dioxin-contaminated, excavated soils would be classified as hazardous waste.
Regulatory aspects
No dioxin-specific regulations are in place.
Glossary
Dioxin: a harmful by-product of burning materials including chlorine or bromines in which two benzene rings are linked via two oxygen atoms.
Furan: a harmful by-product of burning materials including chlorine or bromines in which two benzene rings are linked via one oxygen atom.
References
Saltmeadows Riverside Contaminated Land Plan.
Environment Agency. 2009. Contaminants in soil: updated collation of toxicological data and intake values for humans. Dioxins, furans and dioxin-like PCBs. Environment Agency Science Report SC050021/TOX 12.
Document contact
Dr Darren Beriro: darrenb@bgs.ac.uk