The enhancement of biological ocular UV radiation on beaches compared to the radiation on grass.

BACKGROUND

The influence of albedo on ocular UV exposure has seldom been reported. This paper aimed to explore the enhancement effect on measured ocular UV radiation due to a sand surface compared to measured ocular UV radiation due to a grass surface.

METHODS

We measured ambient and ocular UV radiation over the beach and grass surface in Sanya City of China (18.4°N, 109.7°E). The experimental apparatus was composed of a manikin and a dual-detector spectrometer. Integration of both UVA and UVB radiation was used to denote UV radiation. Then biologically effective ocular UVB radiation (UVBE) and the ratios of UVBE of two surfaces were calculated.

RESULT

Maximum of ocular UV radiation versus time over the two surfaces is bimodal. UVBE on the beach is significantly larger than UVBE on the sand, and UVBE peaked at different solar elevation angle (SEA) over the two surfaces (about 53° and 40° on the beach and grass, respectively, according to Bayesian regression). The maximum of ocular UVBE ratios is greater than two, which peaked SEA was about 50°. One hour's cumulative radiation under sunny weather exceeds thresholds for photokeratitis, conjunctivitis and lens damage.

CONCLUSIONS

Higher albedo significantly increased biological ocular UV radiation. Tourists on tropical beaches should take protective measures and avoid facing the sun directly, especially when SEA is around 50°.