FBT4005_Envi and Health Effects

1. Sources of Nanoparticles in the Environment

Nanoparticles (NPs) in the environment can be categorized into three main sources:

A. Engineered Nanoparticles (Intentional)

• Applications:

• Drug delivery

• Biomedical engineering

• Biosensors

• Groundwater remediation

• Example: Titanium dioxide (TiO₂) used in sunscreens and cosmetics.

B. Incidental Nanoparticles (Unintentional)

• Welding fumes

• Vehicle exhaust emissions

• Industrial processes

• Fuel combustion

• Example: Diesel exhaust particles contain carbon-based nanoparticles.

C. Natural Nanoparticles

• Volcanic eruptions

• Dust storms

• Forest fires

• Soil erosion

• Example: Viruses, which exist naturally at the nanoscale.

2. Environmental Impact of Nanoparticles

A. Nanoparticles in the Air

• NPs can travel large distances, leading to widespread exposure.

Effects:

• Inhaled nanoparticles may cause respiratory diseases.

• Deposition on water bodies may lead to ecotoxicological effects on marine life.

B. Nanoparticles in Soil

Entry Pathways:

• Pesticides and fertilizers

• Wastewater treatment sludge

Effects:

• Disrupt biogeochemical cycles (e.g., nitrogen cycle)

• Accumulate in plants, potentially affecting the food chain.

3. Interaction of Nanomaterials with Biological Systems

A. Reactive Oxygen Species (ROS) Formation

• Definition: ROS are chemically reactive molecules containing oxygen that can damage cells.

• Mechanism:

• NPs catalyze ROS production, leading to oxidative stress.

• Transition metals (Mn⁺) in NPs initiate Fenton-type reactions.

• Light-exposed metallic NPs further boost ROS production.

• Effects:

• Cellular damage: RNA/DNA mutations, apoptosis (cell death).

• Inflammation and toxicity in organs like the lungs and liver.

4. Absorption of Nanoparticles by Organisms

• Inhalation → Lungs → Bloodstream → Brain/Heart

• Ingestion → Digestive System → Liver/Kidneys

• Skin Penetration → Dermal absorption → Bloodstream

5. Possible Risks of Nanomaterials

6. Factors Influencing Nanoparticle Toxicity

• Size: Smaller NPs penetrate cell membranes more easily.

• Shape: Needle-like NPs cause more cell damage than spherical ones.

• Chemical Composition: Some NPs (ZnO, Ag, Cd) release toxic ions.

• Surface Charge: Positively charged NPs are more toxic than negatively charged ones.

• Solubility: Highly soluble NPs release more toxic ions.

7. Size-Dependent Toxicity

• Smaller NPs (<10 nm) enter cell nuclei and cause DNA damage.

• Larger NPs (10-100 nm) are trapped in organs but have lower cellular penetration.

• Immune System Response:

• Larger NPs are identified and removed more easily.

• Smaller NPs evade detection, increasing toxicity.

8. Shape-Dependent Toxicity

• Round-shaped NPs: Easily absorbed via endocytosis.

• Needle-like NPs: Cause mechanical damage to cells.

• Plate-like NPs: Cause higher necrosis rates.

9. Chemical Composition and Toxicity

• SiO₂ NPs: Cause oxidative stress.

• ZnO NPs: Damage DNA structure.

• Fe & Zn NPs: Useful in small amounts but toxic at high concentrations.

• Heavy Metal NPs (As, Pb, Hg, Cd): Highly toxic, causing organ failure.

10. Crystal Structure and Toxicity

• TiO₂ NPs exist in different forms:

• Rutile: Causes DNA damage and lipid peroxidation.

• Anatase: Less toxic, with minimal cellular impact.

11. Surface Charge and Toxicity

• Positively charged NPs: More toxic due to stronger electrostatic interactions with cells.

• Negatively charged NPs: Less toxic, harder to penetrate cell membranes.

12. Solubility and Toxicity

• Highly soluble NPs (CuO, NiO): Release toxic metal ions.

• Insoluble NPs (TiO₂, SiO₂): Cause mechanical stress in tissues.

13. Toxicity of Specific Nanomaterials

A. Titanium Dioxide (TiO₂) NPs

• Effects:

• Induce ROS formation, leading to oxidative stress.

• Attach to cell membranes, damaging organelles.

• Impact on Ecosystems:

• Inhibits microalgae growth.

• Causes DNA damage in marine species.

B. Silver (Ag) NPs

• Effects:

• Damage bacterial cell walls, causing cell leakage.

• Generate free radicals that disrupt cellular functions.

• Human Risks:

• Can bind to DNA, preventing proper replication.

• Toxic at high doses, leading to inflammatory responses.

C. Gold (Au) NPs

• Effects:

• Highly size-dependent:

• 1.4 nm Au NPs → Cause rapid cell death.

• >10 nm Au NPs → Less toxic.

• Influences DNA structure and gene expression.

D. Zinc Oxide (ZnO) NPs

• Safe in bulk form, but toxic at the nanoscale.

• Effects:

• Produces free radicals, disrupting metabolism.

• Causes cytotoxicity and oxidative stress.

E. Copper Oxide (CuO) NPs

• Toxic Mechanism:

• Induce oxidative stress and DNA damage.

• Cause cell death in kidney and lung tissues.

14. Toxicity Pathways of Nanoparticles

1. Oxidative Stress: ROS production damages DNA and proteins.

2. Genotoxic Effects: DNA mutations leading to cancer.

3. Signal Disruption: Interferes with cellular communication.

15. Key Takeaways

• Nanoparticles have diverse sources, including natural, incidental, and engineered origins.

• Their impact depends on size, shape, charge, composition, and solubility.

• Health risks include inflammation, organ toxicity, DNA damage, and neurotoxicity.

• Environmental concerns arise from their accumulation in soil, air, and water.

• Regulation and safety assessments are needed to minimize risks.