(iii) Describe briefly why / how the metal and/or its compounds are harmful to organisms and/or environment.

How lead is harmful to humans?

 Lead affects almost every organ system but mostly the central nervous system, particularly the developing brain.
  Lead ion has highly disruptive properties. It replaces other metals (e.g., zinc, calcium and iron) in reactions.
  Lead interferes with the proteins by displacing other metals in the molecules. This changes the shape of the protein molecule.
  Damaged proteins lead to disruption of cellular function and cell death. Lead ²⁺ ions can substitute for calcium ions or displace calcium in the reactions that transmit electrical impulses in the brain.
There is also no means of removing metal ions from the body, so they tend to accumulate.

The symptoms of lead poisoning may include:

• Abdominal pain and cramping
• Constipation
• Difficulty sleeping
• Irritability
• Loss of developmental skills (in young children)
• Reduced sensations

Very high levels of lead may cause vomiting, muscle weakness, seizures, or coma.

Consequences of Lead poisoning

 How is lead harmful to other organisms and the environment

  Lead can remain in the environment as dust indefinitely.

  It can enter the environment through mining practices, steel industry, crop enhancers, improperly disposed of batteries, or improperly stored metal parts that leech into the surroundings.

  Atmospheric lead is deposited in vegetation, ground and water surfaces. In certain chemical environ­ments it will be transformed to increase its solubility (e.g., the formations of lead sulfate in soils),

  Lead in vegetation and animal surfaces can prevent the processes that purifies the calcium pool in animals and decomposer organisms.

Lead in the environment

Effects of lead on soil

  Lead accumulates in the soil, especially soil with a high organic content 

Lead displaces other metals in the soil and become more soluble, thus is more readily taken up by plants.

  Soils near highways, freeways, and smelting facilities have higher levels of lead because of exposure to lead dust.

Effects of lead on plants

  Plants on land tend to absorb lead from the soil and retain most of this in their roots. 

Lead coats the surface of the leaf and reduces the amount of light reaching it. lead can affect population genetics.

Effects of lead on micro-organisms

  Evidence also suggests that micro-organisms can make lead more soluble and hence more easily absorbed by plants.

Effects of lead on animals

  Aquatic organisms take up inorganic and organic lead through a transfer of lead from water and sediments

Done by:

Lim Li