Toxicology Notes

Metric Prefixes

• Milli (m): 10^-3 (one thousandth)

  • Example: millimeter (mm)

• Micro (μ): 10^-6 (one millionth)

  • Example: micrometer (μm)

• Nano (n): 10^-9 (one billionth)

  • Example: nanometer (nm)

Water Mass Comparisons

• Question: How many milligrams (mg) of water are in 1 Liter of water?

  • Density of water = 1 g/mL

  • 1 L = 1000 mL

  • Mass of water = 1000 g (because density is 1 g/mL)

  • Each gram = 1000 mg, hence:

    • Total = 1000 g × 1000 mg/g = 1,000,000 mg

• Micrograms (μg) in 1 L of water:

  • 1 mg = 1000 μg

  • Thus, 1,000,000 mg = 1,000,000,000 μg

Concentration Definitions

• Parts per million (ppm):

  • 1 mg/L = 1 ppm

• Total mg in 1 L of water:

  • 1,000,000 mg

• Parts per billion (ppb):

  • A solution of 1 μg solute/L = 1 ppb

Serial Dilution

• Definition: A stepwise dilution of a substance

  • E.g., diluted to 1/10th concentration, then next step leads to 1/100th concentration after thorough mixing.

• Visual Resource: Video here

Serial Dilution Discussion

• After 6 rounds of 10-fold serial dilution (1 mL transferred into 9 mL), discuss the comparison of the concentration to the original.

Types of Toxins

• Mutagens:

  • Substances that increase the risk of mutations, potentially leading to cancer. Examples include ethyldiazonium ion and others.

• Carcinogens:

  • Factors causing or promoting cancer cell growth; includes mutagens among other agents.

• Teratogens:

  • Substances increasing birth defect risks, e.g., alcohol during pregnancy.

• Neurotoxins:

  • Causes neurological damage. Examples: PCBs, methyl mercury, lead, arsenic.

  • EPA estimate: 1 in 6 women of childbearing age in the U.S. has harmful mercury levels.

Endocrine System Overview

• Hormones:

  • Chemical messengers with examples like insulin and estrogen

• Endocrine System:

  • Produces and regulates hormones; includes the pancreas, ovaries, etc.

• Normal Hormone Process:

  • Hormones bind to receptors on target cells to transmit messages.

Endocrine Disruptors

• Chemicals can:

  • Mimic hormones, triggering hormonal signals.

  • Block hormone receptors.

• Impact on Hormones:

  • Disruptors can affect hormones functioning at low concentrations.

  • Examples include antiandrogen and estrogen-like chemicals.

  • Video Resource: here

Main Types of Hormones Affected by Disruptors

• Thyroid Hormones:

  • Regulate growth, metabolism, energy availability.

  • Disruptors may slow metabolism.

• Estrogen:

  • Mimics can induce female characteristics in males; blockers can cause reproductive issues in females.

• Androgens (Testosterone):

  • Mimics induce masculine characteristics in females; blockers cause reproductive issues in males.

Toxicity Assessment and Analysis

• LD50 (Median Lethal Dose):

  • The dosage that kills 50% of exposed individuals.

• Extrapolation of Data:

  • Can data be applied to humans?

• Toxicity Ratings:

  • Lower LD50 = more toxic.

Dose-Response Curves

• Nonlinear vs. Linear Dose-Response:

  • Understanding effect threshold levels, dose-response models, and how toxins harm at varying levels.

Semilog Graph Paper Usage

• Used for large range values, such as in serial dilutions.

• Cycles increase exponentially (powers of 10) to accommodate value ranges.

Epidemiological Studies

• Focus on disease frequency, distribution, causes in populations.

  • Limitations include linking results to chemicals, focusing on new hazards, and randomizing groups.

• Spurious Correlations:

  • Example: Divorce rate in Maine vs. per capita consumption of margarine.

Chemical Exposure in Daily Life

• Common sources of harmful chemicals in everyday items, such as toys, food, and water containers.

Protecting Children from Toxic Chemicals

• Children more susceptible due to higher exposure levels relative to body weight, behavioral factors, and less developed systems for detoxification.

Pollution Prevention Principle

• New chemicals considered harmful until proven safe.

  • Push to eliminate significant harms from existing chemicals.

  • Related to POPs treaty to phase out harmful substances.

CERCLA (Superfund) Overview

• Legislation aimed at identifying and cleaning up hazardous waste sites.

  • Provides federal authority for cleanup of hazardous substances impacting health/environment.