In the previous post, we discussed about the detrimental and beneficial effects of the sun's ultraviolet rays. In this post, we'll take a look into the factors that determine how much of the UV rays is absorbed by each individuals.
Know thy skin type
Your genes is, foremost, the most important factor that you should take note of before exposing yourself to the sunlight. Experts have identified six different skin types based on the colors of the hair and eye, and the reactions caused by being under a strong sun. Refer to the diagram and the categories to know your type. [1]
Type I - Often burns, rarely tans. Tends to have freckles, red or fair hair, and blue or green eyes.
Type II - Usually burns, sometimes tans. Tends to have light hair, and blue or brown eyes.
Type III - Sometimes burns, usually tans. Tends to have brown hair and eyes.
Type IV - Rarely burns, often tans. Tends to have dark brown eyes and hair.
Type V - Naturally black-brown skin. Often has dark brown eyes and hair.
Type VI - Naturally black-brown skin. Usually has black-brown eyes and hair.
Depending on the UVI of the day, you should take the necessary precautions according to the severity imposed given in the following table,[1] which is very much dependent on your skin type.
The UV Index is a general indicator. Depending on where you are specifically and various other conditions, the following rules should be factored in as well. [2,3]
The recommendation for safe level of sun exposure hence, can be summed up by the following:
Of course, logic applies depending on the various other conditions as highlighted in this article. If you are at the peak of Mount Everest or K2 when the sun is at its peak hour, no minimal amount of sun exposure without sunscreen, I'd say, is advised.
As it clearly shows that we are not getting enough Vitamin D3 from sun exposure, which I'd rather stay away than suffer the many health and skin issues due to excessive exposure as we discussed in Part 2 of this series, the quest to find balanced alternatives to the sun UVR continues in Part 4. Stay in tune for Part 5 for sunscreen recommendations.
Related posts:
Part 1 - Introduction
Part 2 - The good and bad of UV rays exposure
Check the UV Index
The UV Index (UVI) indicates how strong the UV rays (UVR) from the sun is at a particular place. The index is reported by various local weather forecasts worldwide. Refer to the list in the WHO website for your local weather forecasts link or go to www.uvawareness.com and type in your location.Depending on the UVI of the day, you should take the necessary precautions according to the severity imposed given in the following table,[1] which is very much dependent on your skin type.
Terrestrial UVR
The UV Index is a general indicator. Depending on where you are specifically and various other conditions, the following rules should be factored in as well. [2,3]
* Time of the day. Peak hours for UVR are from 10am to 4pm.
* Altitude. The higher you are above the sea level, the more exposed you are to the sun's radiation. Each 1 km increase in altitude increases the ultraviolet flux by about 6%.
* Clouds. Light cloud virtually makes no difference to the UVR intensity. Heavy cloud reduces the UVR but not by much therefore do not assume that you are protected from the strong sun. Only very heavy storm clouds will shield us from the rays.
* Surface reflection. You are not completely protected even when in the shades. The snow, sand, and ground/water reflect 30%-80%, 15%-30%, and <5% of UVR respectively.
* Geographical latitude. Annual UVR flux decreases with increasing distance from the equator.
* Altitude. The higher you are above the sea level, the more exposed you are to the sun's radiation. Each 1 km increase in altitude increases the ultraviolet flux by about 6%.
* Clouds. Light cloud virtually makes no difference to the UVR intensity. Heavy cloud reduces the UVR but not by much therefore do not assume that you are protected from the strong sun. Only very heavy storm clouds will shield us from the rays.
* Surface reflection. You are not completely protected even when in the shades. The snow, sand, and ground/water reflect 30%-80%, 15%-30%, and <5% of UVR respectively.
* Geographical latitude. Annual UVR flux decreases with increasing distance from the equator.
Safe level of sun exposure
A 2007 study submitted by the University of Ottawa to the Department of Health and Human Services in Washington, D.C. reports that there is not enough information to determine a safe level of sun exposure. More recently, a research to model the seasonal variation of Vitamin D due to sun exposure [4] summarised that the current advice of about 10-20 minutes of daily sun exposure during the summer months does little in boosting the Vitamin D3 level in our body. Yet, sufficient sun exposure to achieve a worthwhile benefit could adversely impact skin's health. To this effect, many independent sites and research are recommending that we stick to the advisable sun exposure level [6] and fill in the missing Vitamin D3 dosage from other safer nutritional sources [5].The recommendation for safe level of sun exposure hence, can be summed up by the following:
* Fair skin people should spend no more than 10 minutes in the midday sun in shorts and tank top without sunscreen. This produces 10,000 international units (IU) of the vitamin. As this amount is more than the recommended level of 2,000 IUs per day - published in various health sites and by researchers such as Dr. Edward Giovannucci, Professor of Nutrition and Epidemiology of the Harvard School of Public Health [6,7,8] - soaking up the summer sun for 10 minutes should be done 3-4 times a week, not everyday.
* Dark skin people requires around 15-20 minutes under the sun.
* Dark skin people requires around 15-20 minutes under the sun.
Of course, logic applies depending on the various other conditions as highlighted in this article. If you are at the peak of Mount Everest or K2 when the sun is at its peak hour, no minimal amount of sun exposure without sunscreen, I'd say, is advised.
As it clearly shows that we are not getting enough Vitamin D3 from sun exposure, which I'd rather stay away than suffer the many health and skin issues due to excessive exposure as we discussed in Part 2 of this series, the quest to find balanced alternatives to the sun UVR continues in Part 4. Stay in tune for Part 5 for sunscreen recommendations.
Related posts:
Part 1 - Introduction
Part 2 - The good and bad of UV rays exposure
0 comments:
Post a Comment