Radiological Protection Bulletin, No. 222, May 2000

Clothing Protection Factors

The text of the article is given here in full.

Incidences of skin cancer have increased in the UK and elsewhere over the last two decades. Long-term repeated exposure to ultraviolet radiation (UVR) from the sun has been implicated in these increases. Avoidance of exposure to strong sunlight is an important protective measure against the effects of ultraviolet radiation exposure. Several methods of personal protection can be effective in reducing exposure to solar ultraviolet radiation. One of these is clothing protection and this article looks at some of the protective properties of general clothing items.

People going on summer vacation or working or playing outside often want to know whether or not their general summer garments offer good protection against solar ultraviolet radiation or whether they need to invest in specially designed summer clothing. The first point to make is that the protection is only as good as the coverage, i.e. clothing will only protect the skin surface it covers from solar UVR exposure. Specially designed summer clothing may offer better body surface coverage and may also allow for stretch and water content in the assignment of its protection factor. Therefore, adequate protection will be provided during exercise or splashing on the beach if wearing specially designed items. These items should also be tested to a suitable standard and a label should be attached to the items to indicate the standard used in the test and the level of protection offered by the garment. Several standards exist, but in the UK the common standards to appear on UVR protective garments will be the British Standard, the Australian/New Zealand Standard and shortly the European Standard. The second point is that clothing protection is only one aspect of an integrated health information policy, which covers both skin and eye protection. Approaches to minimise sun-induced skin and eye damage are summarised in Table 1. These apply particularly during summer months (i.e. May to September inclusive for the northern hemisphere and November to March for the southern hemisphere) and all year for equatorial regions. The effectiveness of sunscreen protection depends on the quality of its application to the skin surface. For example, a factor 15 sunscreen weakly or incorrectly applied might result in only a factor 3 protection, which could easily result in sunburn in less than an hour. Clothing provides the means of attaining a more consistent level of protection for the skin against UVR. The third point relates to the required level of protection that should be sought. It is commonly felt that a protection factor of 15, which reduces the overall skin exposure to UVR to a fifteenth of its initial value, should be adequate to prevent sunburn globally. However, certain standards require higher protection factors up to 50 in their labelling and classification.

Table 1: Approaches to minimising sun-induced skin and eye damage

• Be aware that there is no such thing as a safe or healthy tan. UVR-induced skin-colour change means skin damage.
• Sensible precautions should be taken to avoid sunburn, particularly in children and those who readily sunburn.
• Unprotected personal exposure to the sun's rays should be reduced during the summer months, particularly during the four hours around noon.
• Shade should be sought wherever possible during the summer, but remember sunburn can occur even when in partial shade or when cloudy.
• Sunburn can occur while swimming and is more likely when there is a high level of reflected UVR, such as from snow and sand.
• Suitable head wear, such as a wide-brimmed or legionnaire's hat, should be worn during the summer to reduce exposure to the face, head and neck.
• Exposed skin should be covered with clothing giving good UVR protection, such as those that are loosely fitting with a close weave or knit with longer sleeves and collar.
• Sunscreens or sunblocks with high sun protection should be applied and reapplied generously and frequently to exposed or uncovered skin.
• Sunglasses should be used that exclude both direct and peripheral exposure to the eye. Avoid looking directly at the sun.
• People may be more sensitive to sun exposure if taking certain prescribed drugs, medicines, cosmetics and plant materials.

Protection factors of summer clothing

The specially designed UVR protective clothing items might offer standardised classification and labelling, but how protective are summer clothing items generally? This is impossible to answer fully, since there is such a wide variety of items available. However, the results of a study on 130 summer clothing items selected at random from commercial suppliers, as shown in Table 2, may offer some insight into the ranges of protection factor on offer. The percentages in each protection category may vary from table to table due to rounding uncertainties.

Table 2: Percentage of clothing samples in each UVR protection factor (PF) range

PF	Percentage of samples
?5	4
6-10	11
11-15	5
16-30	15
31-40	7
41-50	5
> 50	53

From this survey, over 50% of the samples have protection factors that are greater than 50 (i.e. the upper limit on some clothing protection standards). Nearly 60% of the samples have protection factors greater than 40 (i.e. the minimum requirement for the British Standard BS 7949 appropriate to children's clothing). Around 65% of the samples have protection factors greater than 30 (i.e. the minimum requirement proposed for Europe) and nearly 80% of the samples surveyed have protection factors greater than 15 (a commonly recommended level of protection for sunscreens). If this were to be correlated to the types of summer garments in a typical wardrobe, then there would be a one in five chance that a randomly selected item would have a protection factor of 15 or less (i.e. lower than that generally recommended to prevent sunburn globally). In the UK, a protection factor of 10 would generally provide adequate protection against sunburn during summer.

Effect of fabric type

The 130 clothing samples can be subdivided into various main fabric types, as shown in Table 3. For each fabric type, the percentage of samples in four protection factor ranges is shown. Fabrics offering least protection are generally the more open structured materials, such as cheesecloth, sarong fabrics and hosiery samples, and these are including in the other category of Table 3. Of the other fabrics, those offering least protection are cotton and cotton/polyester samples. However, cotton samples also have a high percentage in other protection categories, including those greater than 50. Samples which appear in the higher protection categories are nylon, nylon/lycra and polyester/lycra.

Table 3: Percentage of clothing samples in each UVR protection factor (PF) range for each fabric type

Fabric type	PF ?10	PF 11-30	PF 31-50	PF >50
100% cotton	7	9	6	8.5
cotton/lycra	0	3	1.5	4
cotton/polyester	4	5	1	1.5
100% polyester	0	2	1.5	4
polyester/lycra	0	0	1.5	17.5
100% nylon	0	0	0	2
nylon/lycra	0	0	1	14
other	3	0	0	3

Fabrics in the other category which offer high protection include those made from polyamide. Results from knitted and woven fabrics are compared in Table 4. Although there are no clear differences between the percentages in the lower protection categories for different fabric constructions, there is an indication that knitted fabrics could offer the chance of better protection overall.

Table 4: Percentage of clothing samples in each UVR protection factor (PF) range for each fabric construction

Fabric construction	PF ?10	PF 11-30	PF 31-50	PF >50
knitted	8.5	11.5	10	43
woven	6	8	2	11

Effect of colour

The effect of colour is shown in Table 5. Samples which are cream or 'off-white' (i.e. white with a hint of another colour) generally offer lower UVR protection. The stronger colours, such as red, green and black, offer higher protection. However, there are exceptions and colour alone may not be a clear indicator of the protection level afforded by the garment. This is shown for the results on the range of yellow and blue fabrics in Table 5. The absorption properties of the dyes and their method of incorporation into the fabric appear to be the major factors in determining the level of protection. White fabrics generally do offer a relatively high level of UVR protection. This is because such fabrics are often treated with fluorescent 'optical brightening agents' which produce the 'brilliant white' appearance.

Table 5: Percentage of clothing samples in each UVR protection factor (PF) range for each fabric colour

Colour	PF ?10	PF 11-30	PF 31-50	PF >50
white	1	6.5	4.5	9
off-white/cream	6	1.5	1.5	1
yellow	1.5	4	1.5	5
orange	0	1	1	1
pink	1	0	2	5
red	0	1	1	6.5
brown	2	0	0	1
purple	0	1	1	1
green	0	1.5	0	6.5
blue	1.5	3	1.5	8.5
grey	1	0	0	2
black	1	0	0	5

Summary

From a limited survey of 130 summer clothing samples, selected at random, from commercial suppliers, the following points emerge:

• 80% of the samples surveyed had protection factors greater than 15, which is a commonly recommended level of protection for sunscreens.
• 15% of the samples had protection factors less than or equal to 10, which is considered the minimum acceptable level of UVR protection during summer in the UK.
• 53% of the samples had protection factors greater than 50, a level which allows only 2% transmission of the solar UVR.
• Cotton-based fabrics offer a wide range of protection factors, even when lycra is added as part of the structure.
• Fabrics with the highest protection factors are those with artificial fibres containing lycra, which may not be totally suitable from considerations of comfort during summer.
• Both knitted and woven fabrics offer a wide range of protection, but generally knitted garments are likely to offer greater UVR protection.
• Light coloured fabrics, particularly those which are cream and 'off-white', offer lower levels of UVR protection than the darker colours.
• White fabrics often offer a higher level of UVR protection due to the addition of 'optical brightening agents'.

This may not answer the question whether or not general summer garments offer good protection against solar UVR, partly due to the wide range of variables that can affect the analysis. However, if clothing protection is used as part of an integrated health information programme, the overall UVR exposure should be reduced, which helps people avoid getting sunburnt. Further information about UVR exposure, clothing protection, real-time displays of the sun's UVR levels throughout the UK and information on the World Health Organization initiatives can be obtained.

Colin Driscoll
National Radiological Protection Board
Chilton

Last reviewed: 3 December 2008