ARPANSA - Australian Radiation Protection and Nuclear Safety Agency

The following is meant as a general guide to the amount of protection various materials will provide against solar UV radiation. In general, the higher the protection the better, but often it is also important to consider other factors such as ventilation and comfort in the design of any structures. The table below relates Ultraviolet Protection Factor (UPF) for the amount of effective UV radiation transmitted and absorbed, and will be useful as a reference when discussing protection against UV radiation.

% UV radiation Transmitted	% UV radiation Absorbed	UPF	Protection Category
10	90.0	10	Moderate Protection
5	95.0	20	High Protection
3.3	96.7	30	Very High Protection
2.5	97.5	40	Excellent Protection
2.0	98.0	50+	Excellent Protection

 

Shade Cloth

Shade cloth acts as a physical barrier to incident solar UV radiation and transmits as much UV radiation as visible radiation. So the more you can see through it, the more UV radiation can get through. The amount of transmission depends on the shade factor, that is;

• if the shade cloth is rated at 50%, it absorbs 50% (and transmits 50% and has a UPF of 2),
• if the shade cloth is rated at 90%, it absorbs 90% (and transmits 10% and has a UPF of 10), and so on.

The Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) has measured double knit shade cloths with UPFs as high as 20 (that is, they absorb more than 95% UV radiation).

Staying out of the direct sun (that is, in the shade) will reduce the amount of solar UV radiation you get by at least 50% or more. It is important to remember that half of the ambient solar UV radiation is scattered UV radiation from the sky while the remainder is direct from the sun.

Awnings

These are usually made from fairly solid, closely woven material and therefore provide very good protection. Most of the awning materials measured at ARPANSA have UPFs of 50+ and therefore provide excellent protection.

Umbrella Materials

The amount of protection depends critically on the type of material. As with clothing, the denser the weave the higher the UPF. Some materials are plastic coated and may therefore provide more protection, since plastics generally absorb UV radiation strongly. To be certain, any umbrella made with fabric should be UPF rated, since the lowest umbrella UPF measured was 6, the highest 50+.

Outdoor Roofing Materials

Sometimes outdoor living areas are covered with various forms of plastic sheeting. There are many different types of plastic with different UV radiation absorption properties. Plastics generally absorb UV radiation strongly, and can provide very good protection (it is possible for some clear plastic to completely absorb UV radiation). Most materials measured at ARPANSA have UPFs in the 50+ excellent protection category. Some roofing materials are labelled with the UV radiation transmittances instead of UPFs. Opaque materials (such as aluminium or tin) naturally provide excellent protection UPF 50+.

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Window Glass>

There are many different types of glass. Most are indistinguishable to the human eye, but they provide very different amounts of protection against solar UV radiation. The Protection Factor (PF) measures the decrease in UV light transmitted by a material. A PF of 50 means there is a 50-fold reduction in the amount of UV radiation transmitted. Some examples are:

Window Glass Protection Factors

Glass	PF	UPF
Car side windows	12	12
Car windscreen (laminated)	75	50+
Window glass (house)	10	10
Office building glass	80	50+

 

Tinting can increase the protection against solar UV radiation considerably. Measurements made at ARPANSA indicate that most tints applied to glass areas in cars provide excellent protection UPF 50+. There are even clear tints which rate at UPF 50+.

Personal Protection

When outdoors, it is advisable to use the various items which provide personal protection against solar UV radiation, for example, hats, sunscreen, sunglasses and clothing, even when under some sort of protective structure.

Hats

Wearing a hat with a brim of about 8 cm reduces the solar UV radiation dose to most areas of the face by a factor of 3. The amount of protection depends on the design of the hat, but the materials can also vary the protection provided. A very open weave straw hat may not provide much in the way of protection, but closely woven straw and canvas hats would provide UPF 50+ protection. Legionnaire style caps with flaps covering the neck and ears can also provide excellent protection. Hats made from fabric should be UPF rated as some of the lightweight modern materials have low UPFs, although most made with closely woven materials would provide UPF 50+ excellent protection.

Sunglasses

All sunglasses sold in Australia must comply with the Australian Standard AS 1067, and therefore provide good protection against solar UV radiation. Side shields reduce the amount of UV radiation entering from the side and are essential. Sunglasses rated with EPF 10 provide additional protection against solar UV radiation above the requirements of the Australian standard for situations where solar UV radiation may be more intense (for example, at altitude). The Information Page on sunglasses has more details.

Clothing

The more closely woven the material, the greater the protection. The darker colours invariably absorb more solar UV radiation than the lighter colours in the same sort of fabric. If in doubt look for UPF rated clothing for summer outdoor activities.

Sunscreens

Sunscreens are always useful in summer and are an important adjunct to natural protection (hats & clothing) and should be applied to areas not otherwise protected. Sunscreens of less than SPF 15+ offer only moderate to low protection. Apply to clean, dry skin 15 minutes before going out into the sun.

Reapply regularly, but remember that reapplication only keeps up the protection of the first application, it doesn't give you extra protection. If applying sunscreen of SPF 15+ gives you 2 hours in the sun without burning, then reapplying the sunscreen after 2 hours does not protect you for another 2 hours. You have already received a sunburn dose after the first 2 hours! Also, the UV radiation you get even through the sunscreen adds to your lifetime total UV radiation exposure and increases the risk of skin cancer.

 

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