Consensus published by American Conference of Governmental Industrial Hygienists (ACGIH)
for 265nm-275nm radiation
https://www.acgih.org/science/tlv-bei-guidelines/

Skin safety limit 10 mJ/cm2 per 8 hours
Eye safety limit 3 mJ/cm2 per 8 hours

The dose requirement is extremely conservative as the expected cancer rate is <0.3% after 20 years of daily exposure at the safety limit.