Introduction

One of the most serious environmental problems confronting industrialised nations today is how to deal with hazardous waste generated by many product manufacturers and users.

In general the following criteria are used to judge whether substances have potential to cause problems with regard to contamination.

• Having a significant toxicity to humans
• Having a significant toxicity on the aquatic environment
• Having a significant toxicity on the ecosystem
• Having a significant effect on materials and structures used on sites
• Having a significant persistence in soil or a tendency to bio-accumulate
• Being likely to occur in significant quantities on many sites.

Contaminants such as chemicals, biological agents or combustion materials may present a variety of hazards to human health, the environment or to construction materials. Contamination may be of concern in respect of:

• Operating sites
• Development sites
• Infra-structure developments
• Sites already occupied by ‘sensitive’ uses such as housing or schools
• Problem sites such as old waste-disposal sites that are leaking
  contaminants into the environment.

There are various ways in which the environment becomes contaminated such as leaks, spills, accidents, on-site waste disposal, storage of materials and aerial and water-borne deposition.

The cost of restoring the global inventory of contaminated ecosystems is virtually incalculable. As a result, government, industry and the public have recognised the need for more cost-effective alternatives to traditional physical and chemical methods of contaminant remediation.