Kerala is no longer safe from heat-related issues caused by ultraviolet (UV) rays, suggest the findings of a study that appeared in the journal Environmental Monitoring and Assessment.
The study by researcher Ninu Krishnan Modon Valappil in collaboration with the Kerala State Disaster Management Authority (KSDMA) observed higher variability of ultraviolet index (UVI) characteristics in the State, with more than 79% of the UV measurements falling in the very high and extreme UVI categories, suggesting the need for urgent measures to reduce the resultant health risks.
The UVI is a tool to quantify the potential harm caused by direct exposure to UV radiation. The spatial and temporal dynamics of daily UVI for a period of 18 years (2004–2022) over Kerala were statistically characterised in the study.
The daily, monthly, and seasonal UV indices prepared as part of the study showed high variability. The UVI in the region varies from 1.13 to 14.48 depending upon season and atmospheric conditions, with the lowest value during the study period on December 8, 2007 and the highest on August 26, 2020.
It was observed that more than 79% of the daily UVI had higher values (>8), indicating the strength of the radiations. Notably, among the four dominant seasons, the higher value was observed during the southwest monsoon season followed by summer. A total of 6,574 readings measured by the Ozone Monitoring Instrument (OMI) of the AURA satellite were subjected to the study. Classification of these daily measurements into different indices shows that more than 46% of the total daily observations fall in the category of high UVI (8-10) followed by 33% in the extreme UVI (> 11) category, indicating the high risk of UV radiation in the State.
Vulnerable districts
Among the districts, Thrissur, Palakkad, parts of Ernakulam, Idukki, parts of Kollam, and Thiruvananthapuram are more vulnerable in terms of high UV exposure. The monthly UVI shows a cyclical increasing and decreasing pattern, with peaks in March, April and September and lower indices in June, July and December.
The higher UVI measured in the study area indicates that clear skies or clouds with lower thickness are present for a longer period, although parameters like rainfall, air temperature, cloud optical depth (COD), and solar zenith angle (SZA) will have a bearing on the strength of UV rays reaching the surface.
The World Health Organisation (WHO) classified UVI from 0 (minimal) to 10+ (very high) in 1994. Later, it revised the UVI from 1 (low) to 11+ (extreme) in 2002 to improve its usefulness in raising public awareness.
Common effects
Prolonged exposure to UV radiation beyond 8 will cause acute and chronic health impacts on the skin, eye, and immune system. Sunburn and tanning are among the common acute effects of excessive UVR exposure. In the long term, UVR may lead to skin aging and development of cataract and other eye diseases. Abnormal skin reactions due to light sensitivity such as photodermatoses and phototoxic reactions to drugs can also occur, the study noted.
Though higher UVI was observed during the study period, the daily mean UVI in the study area showed a slight decrease during the analysis period.
The study was co-authored by Pratheesh C. Mammen, José Francisco de Oliveira‑Júnior, Kelvy Rosalvo Alencar Cardoso, and Vijith Hamza.
