Estimates of beneficial and harmful sun exposure times during the year for major Australian population centres.

Objective: To examine the influence of geographical and seasonal factors on duration of solar ultraviolet (UV) radiation exposure of skin to produce recommended vitamin D levels without producing erythema.

Design And Setting: An ecological study using daily Ultraviolet Index (UVI) data collected in major population centres across Australia for 1 year (1 January - 31 December 2001) to calculate sun exposure times for recommended vitamin D production and erythema.

Main Outcome Measures: Sun exposure times to produce either serum vitamin D concentrations equivalent to an oral intake of 200-600 IU/day or erythema for people aged 19-50 years with fair skin (Fitzpatrick type II skin) exposing 15% of the body.

Results: In January, across Australia, 2-14 minutes of sun three to four times per week at 12:00 is sufficient to ensure recommended vitamin D production in fair-skinned people with 15% of the body exposed. However, erythema can occur in as little as 8 minutes. By contrast, at 10:00 and 15:00, there is a greater difference between exposure time to produce erythema and that to produce recommended vitamin D levels, thereby reducing the risk of sunburn from overexposure. From October to March, around 10-15 minutes of sun exposure at around 10:00 or 15:00 three to four times per week should be enough for fair-skinned people across Australia to produce recommended vitamin D levels. Longer exposure times are needed from April to September, particularly in southern regions of Australia.

Conclusion: Our study reinforces the importance of existing sun protection messages for the summer months throughout Australia. However, fair-skinned people should be able to obtain sufficient vitamin D from short periods of unprotected sun exposure of the face, arms and hands outside of the peak UV period (10:00-15:00) throughout Australia for most of the year. The greater variability in sun exposure times during winter, means that optimal sun exposure advice should be tailored to each location.