1. Why electromagnetic waves can be hazardous
Electromagnetic waves can carry different amounts of energy depending on their frequency. Low-frequency waves (like radio waves) carry very little energy per photon, while high-frequency waves (like X-rays and gamma rays) carry a lot. Because of this, not all EM waves affect living tissues in the same way.
The main concern arises with ionising radiation, which has enough energy to remove electrons from atoms. Non-ionising radiation can cause heating effects but typically does not damage DNA directly.
1.1. Ionising vs non-ionising radiation
- Non-ionising radiation: Radio, microwaves, infrared, visible light (mostly causes heating).
- Ionising radiation: Ultraviolet, X-rays, gamma rays (can damage cells and DNA).
2. Hazards of low-frequency EM waves
Low-frequency and long-wavelength EM waves (radio, microwaves, infrared) generally do not ionise atoms. Their main effect on living tissue is heating.
2.1. Radio waves
At normal levels, radio waves are considered safe. However, very intense exposure can cause heating of tissues. This is rare in everyday situations.
2.2. Microwaves
Microwaves can heat water-containing tissues. This is why microwave exposure must be avoided outside controlled devices like ovens. Microwave radiation leaks from appliances are typically very small.
2.3. Infrared radiation
Strong infrared exposure can cause burns or heat stress. Prolonged exposure to high-intensity IR sources can damage skin and eyes.
3. Hazards of visible light
Visible light is safe at normal intensities, but high-intensity sources can still cause harm.
3.1. Bright light and lasers
High-power laser beams can damage the retina. Staring at very bright lights (like the Sun) can also cause eye injury.
4. Hazards of ultraviolet radiation
Ultraviolet (UV) radiation has enough energy to break chemical bonds. It is the lowest-frequency ionising radiation and can cause significant biological effects.
4.1. Skin and DNA damage
UV rays can damage DNA in skin cells, causing sunburn, premature aging, and increasing the risk of skin cancer.
4.2. Eye damage
Excessive UV exposure can damage the cornea and lens, increasing the risk of cataracts.
4.3. Environmental concerns
Reduction in the ozone layer allows more UV radiation to reach the Earth's surface, increasing potential harm to living organisms.
5. Hazards of X-rays
X-rays penetrate deep into tissues and can ionise atoms, causing cellular damage. Medical imaging uses controlled doses, but repeated or unnecessary exposure must be avoided.
5.1. Health risks
- Damage to cells and DNA
- Increased cancer risk with repeated exposure
- Possible tissue burns at very high doses
5.2. Safety measures
- Using lead aprons and shields
- Minimizing exposure time
- Proper calibration of X-ray equipment
6. Hazards of gamma rays
Gamma rays are the most energetic and penetrating EM waves. They can easily ionise atoms and damage biological tissues even at low doses.
6.1. Health risks
- Severe damage to DNA and cells
- Radiation sickness at high exposure
- Increased risk of cancer
- Organ damage with prolonged exposure
6.2. Protection measures
- Lead or thick concrete shielding
- Limiting exposure time
- Maintaining safe distances
- Regular monitoring using radiation badges
7. Regulation and safe exposure limits
Different countries have guidelines for safe exposure limits to different EM waves. Medical and industrial use of X-rays and gamma rays is tightly regulated. Everyday devices like mobile phones and microwave ovens are designed to stay well below harmful levels.
7.1. Safety principles
- Exposure should be as low as reasonably possible
- Use shielding wherever needed
- Limit time spent near strong EM sources
- Maintain safe distances from radiation sources
8. Example: Sunburn from excessive UV exposure
Spending too much time in strong sunlight exposes the skin to high levels of UV radiation. This damages DNA in skin cells, causes inflammation and redness, and may even lead to long-term risks like skin cancer. Sunscreens help by absorbing or reflecting UV rays before they can reach and damage living tissues.