Contaminated Sites and Soil
A contaminated site is defined by the Ministry for the Environment as:
A site at which hazardous substances occur at concentrations above background levels and where assessment indicates it poses, or is likely to pose, an immediate or long-term risk to human health or the environment.
“Background levels” is generally defined as the “ambient levels of a contaminant in the local area of the site under consideration”. This basically refers to the concentrations of an element in soils attributed only to lithological processing (i.e. weathering of parental rock material etc.) and not linked to any identifiable event or activity.
Land can become contaminated through the manufacture, use, storage and disposal of hazardous substances. While contamination is usually associated with industrial activities, the use of hazardous substances in agriculture and residential settings can also cause contamination.
People can become exposed to contaminants in soil through contact with the soil, soil ingestion, eating produce grown on contaminated land and drinking contaminated ground or surface water. If a contaminant is volatile, people may also be exposed by inhalation. The health risk associated with contaminated soil will depend on the type of hazardous substance, the exposure route and the length of time a person is exposed.
For your information, Table 3 summaries general contaminants, their toxicity score, and principal sources.
| Contaminants | Toxicity Score | Predominant Sources |
|---|---|---|
| Arsenic | 5 | Timber treatment |
| Asbestos | 5 | Building, insulation |
| Benzene | 5 | Fuel combustion, fuel-service stations, ports and airports |
| Cyanide gas / hydrocyanic acids | 5 | Electroplating, gold mining, pest destruction, gas works |
| Lead (inorganic or organic) | 5 | Paint, batteries, plastics, leaded petrol additives |
| Mercury | 5 | Pulp and paper, dentistry, batteries, electronics, seed treatment |
| Phenols | 5 | Resin manufacturing |
| Poly-aromatic hydrocarbons (PAHs) | 5 | Fuel combustion |
| Polychlorinated biphenyls (PCBs) | 5 | Electrical |
| Polychlorinated dibenzodioxins and furans | 5 | chlorination/incineration, timber treatment |
| Cyanides (excluding gas or hydrocyanic acid) | 4 | Electroplating, gold mining, pest destruction, gas works |
| Volatile halogenated organics | 4 | Industrial solvents and cleaning |
| Bacterial/viral material | 3 | Hospital waste, animal waste, sewerage, organic / domestic waste |
| Cadmium | 3 | PVC, Ni-Cd batteries |
| Chromium (IV) | 3 | Timber, tanning |
| Formaldehyde | 3 | Glues, resins wood products |
| Landfill gases | 3 | Landfill |
| Nickel | 3 | Metal applications, batteries |
| Pesticides | 3 | Manufacture, storage, inappropriate disposal or use |
| Volatile non-halogenated organics (excluding phenols and PAHs) | 2 | Fuels and fuel combustion |
| Acids and alkalis | 1 | Cleaning, waste treatment, metal finishing |
| Chromium (VI) | 1 | Timber and tanning |
| Copper | 1 | Fungicides, timber, metal applications |
| Organic corrosives | 1 | Metal finishing, photographic |
| Semi-volatile non-halogenated organics (excluding phenols and PAHs) | 1 | Oil refining, gas production |
| Tar, oils and fats (that contain no high or medium ranking substances) | 1 | Oil refining, road construction, food by-products |
| Putrescible waste | 1 | |
| Zinc | 1 | Fungicide, animal remedies, PVC, metal |
*Source: modified from the Ministry of Health (1996).
The Healthy Environments Team has been working closely with the territorial and local authorities (TLAs) in the assessment and management of contaminated sites in the Auckland region.
Further information on contaminated sites is available from the websites of the Ministry for the Environment, Auckland Regional Council and Auckland City Council, and the Contaminated Land in the UK.
