Toxicity and Environmental Fate of Metals and Persistent Chemicals

Toxicity of Metals

  • Why Metals are a Priority: Metals are on the Priority List of Substances, as indicated by ATSDR in 20192019. The Periodic Table of Elements includes various classifications of metals.
  • Classification of Metals:
    • Metalloids
    • Essential Metals
  • Sources of Metal Pollution:
    • Uranium Mining: A significant source, with a legacy impacting Native American health.
    • Electronic Waste (E-Waste):
      • Arises from the recycling of metal-containing products and E-waste itself.
      • Electrical and electronic equipment contains various metallic elements.
      • E-waste has a specific composition of materials.

E-Waste: International Issues and Impacts

  • Global Concerns: E-waste poses international challenges.
  • Case Study: Ghana: In Ghana, children are sometimes employed to dismantle electronic equipment, which directly affects their health due to metal exposure.

Mechanisms of Metal Toxicity

  • Metal-Binding Molecules: Metals can interact with and bind to biological molecules.
  • Mimicry: Toxic metals can mimic essential metals, interfering with normal biological processes.
  • Interference with Essential Metals: They can disrupt the functions of necessary essential metals in the body.
  • Mutagenic and Genotoxic Effects: Some metals can cause mutations and genetic damage.
  • Epigenetic Effects: Metal compounds can induce epigenetic changes (modifications to gene expression without altering the DNA sequence, mentioned twice).
  • Biotransformation: The metabolic alteration of metal compounds within the body.
  • Form and Innate Chemical Activity: The chemical form and inherent reactivity of a metal determine its toxicity.

Factors Influencing Metal Toxicity

  • Age and Gender: Susceptibility to metal toxicity can vary with age and gender.
  • Interactions and Mixtures: Exposure to multiple metals or other substances can lead to varied toxicological outcomes.

Metal Exposure and Health Risks

  • Exposure Biomarkers & Metal Pharmacology: These are used to assess metal exposure and understand their effects.
  • Modes of Exposure:
    • Lungs: Through inhalation of metal dusts, fumes, and vapors.
    • Skin: Via direct contact with metal-containing dusts.
    • Mouth: By ingestion of contaminated substances.
  • Metal Exposure Media:
    • Air
    • Soil/dust
    • Water
    • Biota/Food
  • Metal Emissions: Metals are emitted into the soil.
  • Toxic Metals in Food: Food can be a significant source of toxic metal exposure.
  • Transport and Distribution in the Body: Metals are absorbed, transported, and distributed to various tissues and organs.
  • Toxicity of Several Metals or Metalloids: Different metals and metalloids exhibit varying levels of toxicity.
  • Risks of Metal Exposure:
    • Cardiovascular Disease
    • Effects on Reproduction and Development

Case Studies on Toxic Metals (Part 2 - Self-study)

  • Arsenic (As), a Metalloid:
    • Potential Sources: Various environmental sources. > 2 million people in the U.S. use wells with high As levels (USGS).
    • Adverse Health Effects: Arsenic poisoning is a global public health crisis, notably in Bangladesh. Toxic groundwater threatens 6060 million people in Pakistan. Ghana also experiences As contamination from mining areas.
    • Arsenic in Food: Another route of exposure.
  • Lead in the Environment:
    • CDC Information: The CDC provides data on lead in the environment.
    • Policy Debates: Pennsylvania officials debated mandating lead poisoning blood tests for children (August 2929, 20192019).
    • Local Issues: Recent concerns about lead in Pittsburgh's water supply.
    • Educational Outcomes: Studies show a correlation between lead exposure and educational outcomes.
    • Flint, Michigan Crisis: A significant case study of toxic lead in water, with a widely publicized timeline of events.
    • Blood-Pb Levels: Significant reductions in blood-Pb levels were observed between 1976−20041976-2004, partly due to the Clean Air Act of 19701970.
    • Surveillance: U.S. total blood Pb surveillance data from 1975−20151975-2015 by the CDC.
    • Health Effects: Lead exposure can cause renal effects and cardiovascular disease.
    • Global Impact: Lead poisoning crisis in Nigeria, 20102010.

Biomagnification and Mercury

  • Biomagnification: The process by which the concentration of a chemical increases in organisms at successively higher trophic levels.
  • Mercury in the Bering Sea: An example of increasing mercury levels due to biomagnification.
  • Key Toxicological Principle: