APES Toxicology Detailed Notes

APES Toxicology Overview

  • Toxicology Definition: The study of the interaction between chemical agents and biological systems.
  • Toxicity: The relative ability of a substance to cause adverse effects in living organisms.

Acute Toxicity

  • Definition: Toxicity that results from exposure to a substance which can cause harm or death, typically assessed within 24 hours.
  • Testing: Involves giving a single dose or multiple doses of a chemical, with observation continued for 21 days.
  • Example: An allergic reaction to ingesting a food item that one is sensitive to.

Chronic Toxicity

  • Definition: Results from frequent exposure to a toxic substance where effects may be delayed and often irreversible.
  • Example: Long-term effects of cigarette smoking leading to lung cancer.

Factors Influencing Toxicity

  • Duration and Frequency of Exposure
  • Route of Exposure: Oral, dermal, inhalation, injection.
  • Inter and Intra-species Variations: Differences in toxic response between species (e.g., humans vs. animals) and within species (e.g., male vs. female).
  • Age and Maturity
  • Gender and Hormonal Status
  • Genetic Makeup
  • State of Health

Synergistic Effects in Chemical Combinations

  • Synergists: Combination of chemicals results in a greater effect than the sum of their individual effects (e.g. Tylenol with caffeine).
  • Potentiation: One chemical enhances the toxicity of another (e.g., isopropanol increases hepatotoxicity of carbon tetrachloride).
  • Antagonists: One substance reduces the effect of another (e.g., aspirin and ibuprofen together).

Environmental Factors that Influence Toxicity

  • Temperature
  • Humidity
  • Elevation and Oxygen Concentration
  • Light/Dark Cycles
  • Radiant Heat

Routes of Entry for Toxins

  • Inhalation: Gases, vapors, aerosols.
  • Absorption: Through skin or membranes.
  • Ingestion: Through the mouth.
  • Injection: Intravenously or through cuts.

Common Toxicology Terms

  • Ceiling Values (CV): Max exposure level not to be exceeded.
  • Short Term Exposure Limit (STEL): A maximum exposure limit over 15 minutes.
  • Time Weighted Average (TWA): 8-hour average exposure limit.
  • Permissible Exposure Limit (PEL): Average exposure limit during an average workday.
  • Threshold Limit Value (TLV): Standards for airborne substances set by ACGIH.

Understanding LD-50

  • Definition: The lethal dose that causes death in 50% of a test population.
  • Mortality Curve: Graph plotting concentration (x-axis) against mortality (y-axis) to determine LD-50.
  • Lowest Observable Effects Concentration (LOEC): Concentration at which any mortality is observed.

Dosage vs. Concentration

  • Dosage: Amount of a pure substance relative to the mass of the organism (e.g., 368extmg/kg368 ext{ mg/kg} for caffeine).
  • Concentration: Amount of a substance in a mixture (e.g., 180extmg/L180 ext{ mg/L} for caffeine).

Units in Toxicology

  • ppm (parts per million), ppb (parts per billion), ppt (parts per trillion) to measure toxicity levels.

NOEC and LOEC

  • NOEC (No Observed Effect Concentration): Highest tested concentration with no significant effect compared to control.
  • LOEC (Lowest Observable Effect Concentration): Lowest concentration causing observable effect.

Hazardous Chemicals

  • Categories: Carcinogen, corrosive, irritant, sensitizer, highly toxic, toxic, and target organ effects.
  • Carcinogens: Chemicals that can cause cancer (e.g., certain pesticides, industrial chemicals).
  • Corrosives and Irritants: Damage living tissue (e.g., acids, bases).

Effects on Specific Organs

  • Liver: Common toxins include alcohol and certain chemicals; responses can be cirrhosis or liver failure.
  • Kidneys: Nephrotoxins lead to nephritis and renal failure.
  • Lungs: Pulmonary toxins can cause asphyxiation, embolism, and chronic conditions like emphysema.
  • Skin: Dermotoxins lead to inflammation, burns, and skin diseases.
  • Blood & Bone Marrow: Impacted by hemotoxins, leading to anomalies in blood cell counts.

Immunotoxicity and Endocrine Disruptors

  • Immunotoxins: Can weaken immune response and lead to diseases.
  • Endocrine Disruptors: Chemicals that interfere with hormone systems (e.g., BPA, phthalates).

Vector-Borne Diseases

  • Diseases: Include malaria, dengue, etc., transmitted by arthropods.
  • Factors Influencing Spread: Sanitation, climate, and geographical factors play a significant role.

Bioaccumulation and Biomagnification

  • Bioaccumulation: Accumulation of chemicals over time within a single organism.
  • Biomagnification: Increase of a substance's concentration in higher trophic levels of the food chain.

Case Studies

  • Bhopal Disaster: A significant release of methyl isocyanate causing fatalities and injuries.
  • Lead and Mercury: Case studies on persistent heavy metals and their environmental impacts.

Persistent Organic Pollutants (POPs)

  • Definition: Chemicals that persist in the environment and can bioaccumulate.
  • Effects: Associated with serious health impacts in humans and wildlife.

Conclusion

  • Toxicology Highlights: The importance of understanding chemical interactions with biological systems for public health, environmental safety, and regulatory standards.