The major categories of hazardous substances that are likely to be found contaminating land are:
Arsenic: Used in some pesticides, presence of metalliferous mines. Effects: Toxic and carcinogen to humans.
Lead: Leaded petrol fumes, sewage sludge, some industrial waste, including batteries.
Effects: Toxic and carcinogen to humans. It is absorbed into the blood stream and finally accumulates in the bones
Cadmium: Used in paints. Often present as a contaminant in zinc ore.
Effects: Toxic and carcinogen to humans
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Mercury: Used as pesticides. Also present in sewage sludge and some industrial waste.
Effects: Toxic and carcinogen to humans.
Petroleum hydrocarbons: Pollution levels are due to activities such as coal gasification, petroleum refining, storage and dispensing, and combustion of fossil fuels.
Effects: Toxic and carcinogen to humans.
Microbiological, Animal or human sewage contamination: Pathogenic bacteria may be harmful to humans. Landfill gases. Refuse disposal sites.
Effects: Methane is highly explosive and carbon dioxide is an asphixiant. Both gases in the soil can restrict plant growth.
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