Why UV radiation during heat wave is BAD for you

Data show that the ultra-violet radiation index is dangerously high in Delhi, other Indian cities. Kundan Pandey writes for DownToEarth.org

High levels of ultra violet radiation pose a serious risk to people in Indian cities, including the national capital, according to information by a weather forecasting agency.
 
On Wednesday, Accuweather.com data showed people in Delhi, Ranchi, Hyderabad, Patna and several other cities of India are exposed to UV index of 9, which is quite dangerous for health. Prolonged exposure to UV rays is associated with skin cancers. 

The information is based on satellite data, which may not give the accurate measure of UV radiation people actually get exposed to. But ground checks also confirm that UV rays are on the higher side in India, which can have detrimental impact on health.

Chief programme scientist at the Indian Institute of Tropical Meteorology, Pune, Gufran Beig, says UV radiation in Delhi is definitely above normal.

IITM set up a monitoring system in Delhi about two weeks ago and found the UV index to be somewhere in the range of 6 to 9, which carries medium to high risk for health.

Beig says IITM prepared an index around two years back.

The scientists studied the impact of UV rays on humans in the Indian sub-continent to prepare the index. It may be different for other sub-continents.

UV index of 0 to 4 is classified as no risk category while 4-5 has low risk.

If the UV index reaches 5 to 7 range, it means it has medium health risk on health; and 7 to 10 carries high risk, he says, adding that if it crosses 10 it is dangerous.

Ranchi-based Birsa Agriculture University has also been registering higher UV-B rays for the past couple of years.

Scientist at the university, Abdul Wadud, says UV-B radiation almost doubles during day time from 11 am to 2 pm.

"Though it is not a proper study, but we keep monitoring minimal erythemal dose (MED, the amount of UV radiation that will produce minimal erythema or sunburn or redness of an individual's skin within a few hours following exposure) for the purpose of weather monitoring and found that it reached 1.7 units sometimes, which is almost double the safe level of 1," he said.

He explains that UV rays are of three types -- A, B and C. UV-C gets filtered due to ozone layer while A and B reach Earth.

UV-A is beneficial for health but B becomes dangerous when it crosses the limit. It causes sunburns and can lead to skin cancer and cataract.

Reason for high UV index, he says, may be that the sun is almost vertical in May.

If temperature increases, UV rays will also increase. It is possible that UV radiation in Andhra Pradesh and Telangana is also high, he adds.

Image: A woman rides a motorcycle with her face covered to protect herself from sun stroke on a hot summer day in Chandigarh. Photograph: Ajay Verma/Reuters