Notes on Emerging Contaminants and Environmental Impact

Emerging Contaminants

  • Definition: Chemicals recently identified in the environment, studied for about 15-20 years. Not previously detected due to analytical limitations, now found at higher levels than expected and posing unknown risks to humans and ecosystems.

  • Categories of Emerging Contaminants:

    • Pesticides
    • New Persistent Organic Pollutants (POPs)
    • Pharmaceuticals and Personal Care Products (PPCPs)

Classical Contaminants

  • Previously Studied Contaminants:
    • Underground Storage Tanks: BTEX (Benzene, Toluene, Ethylbenzene, Xylene), chlorinated solvents
    • Persistent Organic Pollutants (POPs): Such as DDT, dioxins, and PCBs
    • Air Pollutants: Smog, Polycyclic Aromatic Hydrocarbons (PAHs)

Historical Context of Pesticides

  • Pesticides have been in use for over 4000 years, originating with elements like sulfur, lead, mercury, and later, DDT.
  • Impact of Pests: 20-40% of global crop yields lost to pests annually; up to 50% in tropical regions.
  • Expenditures: Global spending on pesticides was approximately $56 billion in 2012.

Issues with Pesticides

  • Persistence and Bioaccumulation: 90% of pesticides may not reach their target, resulting in diffuse environmental contamination.
  • Health Impact: Responsible for about 200,000 deaths per year, primarily in developing countries, due to acute human poisoning.

New Persistent Organic Pollutants (POPs)

  • Examples:
    • Perfluorooctane sulfonic acid (PFOS): Used in various products including furniture and textiles.
    • Decabromodiphenyl ether: Applied as a flame retardant, present in electronics and textiles.
    • Short-chain chlorinated paraffins & Hexachlorobutadiene: Utilized in plastics and textiles.

Pharmaceuticals and Personal Care Products (PPCPs)

  • Definition: Includes therapeutic drugs, personal care items. More than 4,000 distinct molecules are utilized.
  • Environmental Impact: Over 100 PPCPs detected in aquatic environments at concentrations in the range of ng to μg/L.
  • Sources of PPCPs:
    • Livestock treatments
    • Companion animal care
    • Aquaculture
    • Inappropriate disposal of pharmaceuticals.

Health and Ecological Concerns

  • Chronic Exposure Risks: PPCPs are designed to have biological effects at low doses; concerns include potential bioaccumulation and persistence in the environment, leading to endocrine disruption.
  • Notable Example: Diclofenac, used as a medication, caused a dramatic decline in vulture populations in India due to environmental effects from veterinary use.

Key Concepts Related to Pollution

  • PBT (Persistent Bioaccumulative Toxic): Chemicals that persist in the environment and accumulate in living organisms.
  • Controversial Microplastics: Included in regulations; microbeads banned in several countries due to environmental concerns.

Sewage Treatment and Chemical Release

  • Control Mechanisms: Sewage treatment processes are essential for controlling the release of these emerging contaminants into the environment.

Conclusion and Focusing Questions

  • Major Themes:
    • Understanding emerging contaminants and their implications.
    • Acknowledgment of historical pesticide reliance and the emergence of new POPs with similar issues.
  • Focusing Questions:
    • What defines the term “emerging contaminant”?
    • Can you provide examples of new POPs and their exposure pathways to humans?
    • What are the primary sources of PPCPs present in the environment?