What is the UV Index? – An Important Health Parameter
The Ultraviolet (UV) Index is an internationally recognized scale developed by the World Health Organization (WHO), World Meteorological Organization (WMO), and United Nations Environment Programme (UNEP). It measures the intensity of the sun’s UV rays and informs people about their risk so they can take appropriate protective measures.
The UV Index scale ranges from 0 to 11+. It is a linear scale, meaning as the index increases, the intensity of UV radiation increases proportionally.
UV Index Classification and Safety Guidelines
| UV Index | Category | Risk Level | Protection Required |
|---|---|---|---|
| 0-2 | Low (Green) | Minimal risk | No special protection needed; safe to be outdoors |
| 3-5 | Moderate (Yellow) | Some risk | Stay in shade during noon, use sunscreen, hat, glasses |
| 6-7 | High (Orange) | High risk | Limit outdoor time between 10AM-4PM, protection essential |
| 8-10 | Very High (Red) | Very high risk | Extra precautions, minimize sun exposure |
| 11+ | Extreme (Violet) | Severe risk | Avoid going out, all protective measures mandatory |
According to WHO, when the UV Index is 3 or above, safety measures become necessary.
India’s UV Index: Global Status and Regional Variation
India is among the top 10 countries in the world where the UV Index is recorded at the highest levels. In summer, many regions in India experience dangerous levels of UV Index:
UV Index in Major Indian Cities (2025):
Hyderabad: 15 (Extreme) during midday
Delhi: 12 (Extreme) in peak summer
Mumbai: 13 (Extreme) in summer
Bengaluru: Consistently 14 (Extreme)
High-risk States:
Rajasthan: Desert region, high UV levels
Madhya Pradesh: High UV during summer
Jharkhand: High UV radiation levels
Chhattisgarh: High UV Index in summer
Kerala’s Palakkad and Malappuram districts recorded a UV Index of 11 in 2025, leading the State Disaster Management Authority to issue a red alert.
Global UV Index Comparison: India’s Position
Countries with Highest UV Index:
Australia: 12+ (Extreme)
New Zealand: 12+ (Extreme)
Peru: 11+ (Extreme)
Bolivia: 11+ (Extreme)
Chile: 11+ (Extreme)
Countries with Lowest UV Index:
Iceland: 2-3 (Low to Moderate)
Finland: 2-4 (Low to Moderate)
Russia: 1-5 (Low to Moderate)
Canada: 3-5 (Moderate)
India’s position is due to its tropical location, high-altitude regions, and seasonal conditions, which allow intense sunlight to reach the surface.
Health Risks of UV Radiation
Immediate Effects:
Sunburn: Skin irritation, redness, pain, and blisters
Photokeratitis: Swelling and pain on the eye’s surface
Immune System Impact: Can weaken the body’s immunity
Long-term Effects:
Skin Cancer: Causes 90% of non-melanoma and 65% of melanoma cases
Skin Aging: Wrinkles, spots, loss of skin elasticity
Eye Damage: Cataracts, pterygium, retinal impact
DNA Damage: Cellular mutations, increasing cancer risk
According to WHO, in 2020, UV radiation caused 1.2 million new cases of non-melanoma and 325,000 melanoma cases. 15 million people are blind due to cataracts, 10% of which are caused by UV radiation.
Essential UV Protection Measures
Primary Protection:
Stay in Shade: Especially between 10AM and 4PM
Protective Clothing: Full-sleeve clothes, wide-brimmed hats, UPF fabric
Sunglasses: With 100% UV protection
Sunscreen: Broad-spectrum SPF 30+, apply at least 30 minutes before exposure
Advanced Guidelines:
Reapply Frequently: Every 2 hours or after sweating/swimming
Adequate Quantity: About 2 tablespoons of sunscreen for full body
Avoid Tanning: Both artificial and natural
Regular Check-ups: Self-examination every month, annual dermatologist visit
Special Attention:
Children: Childhood sunburn increases future cancer risk
High-risk Individuals: Fair skin, family history of cancer, weak immunity
Outdoor Workers: Require special protection
UV Index Measurement and Forecasting
Key Measurement Factors:
Ozone Layer Thickness: Measured by satellite
Cloud Cover: Amount and type of clouds
Altitude: Higher altitude means higher UV intensity
Seasonal Changes: Sun angle and Earth-Sun distance
Monitoring Systems:
Ground Instruments: Spectrometers, radiometers
Satellite Technology: Global monitoring
Weather Services: Daily forecasts
Climate Change and UV Radiation
Effects:
Temperature Rise: 2°C increase may cause 11% rise in skin cancer cases by 2050
Ozone Depletion: 1% ozone loss can increase skin cancer by 1-2% (melanoma) and 3-4.6% (squamous cell)
Weather Changes: Variations in cloud and atmospheric conditions
Impact in India:
More Days of High UV: Extended periods of high UV in summer
Increase in Urban Areas: Urban heat island effect intensifies UV impact
“Why this matters for your exam preparation”
Geography and Environment:
Atmospheric science, ozone layer, seasonal changes
India’s global UV ranking and state-wise variation
Science and Technology:
Electromagnetic spectrum, UV ray properties
Health impacts and prevention
Current Affairs:
Public health policy, government awareness campaigns
International cooperation (WHO, Montreal Protocol)
Policy and Governance:
Disaster management (e.g., Kerala red alert)
Safety rules for outdoor workers
Statistics:
Health statistics, global comparison
This topic is frequently asked in geography, environment, science, policy, and current affairs sections of UPSC and other competitive exams. A deep understanding of related facts and concepts will make your answers more analytical and factually strong. This subject is often discussed in UPSC prelims, mains, and interviews.
External References:
World Meteorological Organization – UV Index
Why this matters for your exam preparation:
Facts and concepts related to UV Index and radiation are frequently asked in geography, environment, science, policy, and current affairs questions. This will enhance your conceptual clarity, analytical ability, and answer quality. This topic often features in UPSC prelims, mains, and interviews.
