With the capital witnessing very high temperatures in the last month, an ultraviolet (UV) ray index developed by the Ministry of Earth Sciences has shown that from May 15 to June 1, Delhi received medium to high UV radiation during peak afternoon hours. Of these, 11 days were in the high-risk category. Scientists started measuring UV rays in the capital and categorising values according to the index from May 15.
According to the index, UV ray values between 5-7 are in the medium-risk category, where only “sensitive people” who are susceptible to skin and eye reactions from sun exposure are at risk. Values between 7-10 are identified as high-risk on the index, putting the public at risk.
The highest index value, 8.6, was seen on May 26, followed by 8.2 on May 27 and 8.1 and 8.0 on May 21 and May 17 respectively.
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Last weekend, UV ray values reduced marginally to 7.9 and 7.8 on Saturday and Sunday. It was recorded at 7.7 on Monday. May 15 and 19 saw the least values on the index at 5.5 and 5.6.
Scientists from the Indian Institute of Tropical Meteorology‘s System of Air Quality and Weather Forecasting and Research (SAFAR) — who developed the index in 2013 — said in the former category, it is advisable to avoid direct sun exposure for more than two hours. In the latter, indirect sun exposure should also be avoided.
Dr Gufran Beig, project director of SAFAR, said, “High-risk means the suns rays are harmful. Direct and continuous exposure to the sun for just an hour is sufficient to get a sun burn… Prolonged exposure to solar UV radiation may result in acute and chronic health effects.”
The UV index is a “rough measure” of the amount of harmful ultraviolet radiation in sunlight reaching the earth’s surface at a given location — where 0 indicates no risk, 1-4 indicates a low risk of overexposure and above 10 signifies an extreme risk, he said.
Scientists have observed that peak values of UV rays on the index are observed between 12-3 pm, with the maximum being at 1 pm. “In Delhi, the index is mapping UV rays in Lodhi Road. “It is sufficient to study UV rays received by every state at one location, because they will be more or less uniform across the state. We are also studying the same in Pune in one location,” Dr Beig said.