1. Classification of Hazardous Waste
As there are a number of compounds, products and product combinations, which can be termed as toxic. They can be grouped majorly into five categories, viz. i) chemicals, ii) biological wastes, iii) flammable wastes, iv) explosives and v) radioactive wastes.
The table below gives some common examples of these different categories.
Table: Sources and some Examples of Toxic and Hazardous Wastes
Inorganic metals, salts, acids and alkalies
|Biological||Hospitals - malignant tissues, contaminated material like hypodermic needles, bandages, etc.
Wastes from biological research facilities.
|Flammable||Mostly in liquid form, but may exist along with solid chemicals, e.g. organic solvents, oils, plasticisers and organic sludges.|
|Explosive||Wastes from ordnance factories, etc.|
|Radioactive||Regulated by Atomic Energy Commission and separately disposed of|
2. Sources of Hazardous Waste
Toxic pollution occurs as a result of a variety of human activities. Some of them are listed below.
Industries and sewage treatment plants discharge wastes which contain toxic substances directly into waterways; these direct pipeline discharges are called point sources.
Air emissions from manufacturing; from fuel combustion in cars and other motors, homes and buildings; and from power plants contain numerous chemicals that drift in the atmosphere and rain down upon or absorb into the surface of the ocean and other bodies of water.
Plutonium processing plants, nuclear power plants, nuclear submarines and nuclear waste dumps are the sources of radioactive contamination. Incinerated, spilt and discharged wastes can also cause marine pollution.
Toxic pesticides are dispersed through the environment by rain running off chemical-treated land and flowing into lakes, rivers, estuaries and coastal waters.
Other sources of pollutants in rainwater run-off include material from numerous man-made surfaces - roads and parking lots, city streets and buildings, cars and houses. These sources of run-off pollution are called non-point sources.
Household cleaning and disinfecting products are flushed into sewage systems and out through treatment plant discharge, or are washed from property and septic tanks into groundwater and streams.
Oil drilling and transport, mining and maritime operations all result in the accidental introduction of significant amounts of toxic materials into the marine environment, as does leakage from storage tanks and pipelines, and seepage from waste dumps.