UV Light: Protecting our DNA - In Depth Notes

Electromagnetic Spectrum

• Definition: The electromagnetic spectrum consists of all types of electromagnetic radiation, organized by wavelength and frequency.

• Types of Electromagnetic Waves:

  • Radio waves

  • Microwaves

  • Infrared radiation

  • Visible light

  • Ultraviolet radiation

  • X-rays

  • Gamma rays

• Wavelength Measurement: Wavelength is measured in nanometers (nm) and represents the distance between identical points in adjacent waves.

• Energy Relationship: The shorter the wavelength, the higher the frequency, meaning the more energy the wave carries.

• Visible Light: Contains wavelengths of 380-750nm, which humans can see.

• Infrared Light: Wavelengths from 780nm to 1mm that transmit heat.

• Ultraviolet Light: Contains shorter wavelengths (100nm – 400nm) that are invisible to humans but can be harmful.

Earth's Atmosphere

• Function: The atmosphere supports life by allowing certain types of electromagnetic radiation to reach the Earth, while blocking harmful radiation (like X-rays and gamma rays).

• Layers of the Atmosphere:

  • Troposphere

  • Stratosphere (contains the Ozone Layer)

  • Mesosphere

  • Thermosphere

  • Exosphere

• Ozone Layer: Protects Earth from harmful UV radiation. Pollutants like chlorofluorocarbons are depleting ozone, increasing UV exposure and related health risks.

Ultraviolet Radiation

• Definition: A form of non-ionizing radiation emitted by the sun and tanning beds.

• Types:

  • UVA (320-400 nm): Longest wavelength; penetrates skin deeply; linked to wrinkles and skin cancer.

  • UVB (280-320 nm): Important for Vitamin D production; causes DNA mutations and skin cancer; only 5% of UV rays.

  • UVC (100-280 nm): Shortest and most energetic; completely blocked by the ozone layer.

Harmful Effects of UV Radiation

• DNA Damage: UV radiation, particularly UVB, can cause mutations that lead to skin cancer.

  • Pyrimidine Dimers: Caused when UV photons induce bonds between adjacent DNA bases, creating structural kinks that can lead to errors during DNA replication.

• Cancer Development:

  • Skin Cancer: Most common cancer type in the US, including melanoma and non-melanoma types (e.g., Basal Cell Carcinoma, Squamous Cell Carcinoma).

  • Cumulative Damage: Repeated UV exposure increases skin cancer risk over time.

  • Other Conditions: Can lead to premature aging of skin, and cataracts (eye lens damage).

Protection from UV Radiation

• Best Practices:

  • Avoid the sun during peak hours (10am-4pm).

  • Wear protective clothing and sunglasses.

  • Use broad-spectrum sunscreen with SPF (Sun Protection Factor).

  • Understand SPF: How long it would take to burn using that sunscreen compared to without.

  • Fun Fact: Melanin provides some natural protection against UV exposure.