Built and deployed UV-RHEUM, an experimental environmental UV exposure estimator

Technical summary

I designed, implemented, tested, and deployed UV-RHEUM as part of RheumaScore’s Experimental section. The tool estimates ambient erythemally weighted UV exposure from the UV Index and exposure duration, reporting results in J/m² and Standard Erythema Doses. The calculation follows the CIE and WHO definitions:

• Erythemal irradiance: E = UVI / 40 W/m²
• Constant-UVI exposure: SED = UVI × minutes / 66.67
• 1 SED = 100 J/m²

UV-RHEUM records location, date, time, altitude, Fitzpatrick phototype, photosensitive disease, and photosensitizing medication as research context. It does not convert phototype into an individual MED, apply unvalidated disease or medication multipliers, estimate flare probability, or provide a “safe exposure time.” The implementation runs entirely in the browser and does not transmit or store user data. It includes strict input validation, bounded altitude estimation, fail-closed handling of invalid values, responsive desktop and mobile layouts, and explicit clinical safety language. The release passed 120 automated tests, browser-based functional testing, source and deployment parity checks, and an independent clinical and code review. Live release: https://rheumascore.xyz/uv-rheum.html