Solar radiation

Ultraviolet (UV) radiation is emitted from a number of sources, both natural and artificial. Some artificial sources include: phototherapy, bactericidal, fluorescent, neon and halogen lighting, welding equipment, ‘black lights’, and counterfeit currency detectors. This section, however, will cover UV radiation from the sun.

Some UV exposure is essential for good health, stimulating vitamin D production in the body. Excessive exposure to ultraviolet radiation, however, is associated with different types of skin cancer, sunburn, accelerated skin aging, as well as cataracts and other eye diseases. The severity of the effect depends on the person, the wavelength, intensity, and duration of exposure.

Recognizing the Potential for UV Radiation

Solar UV radiation is the most significant source of UV radiation and can reach a person on the ground from three sources, directly from the sun, scattered from the open sky and reflected from the environment. This means that even if a person is shaded from the direct sun they can still receive substantial UV radiation exposure. Also some ground and building surfaces reflect UV radiation including water, snow, white paint, light coloured concrete and metallic surfaces. These surfaces can reflect UV radiation onto the skin and eyes and reduce the effect of protective measures. UV Radiation exposure does not depend on temperature, can be high even on cool and cloudy days, can pass through clouds, and through loosely woven material.

Photosensitisers: Certain substances, chemicals, and medications can cause abnormally high sensitivity to UV radiation through ingesting, inhaling, or coming in contact with the skin.

Common substances that cause photosensitivity include (not intended to be a comprehensive list):

• Plants such as citrus, bergamot, fennel, St John’s Wort, chrysanthemum, bind weed, fig, dill, buttercup, carrots and celery.

• Medications such as thiazide diuretics (drugs which cause excessive urine production), drugs used in the treatment of high blood pressure, certain antibiotics (tetracyclines, sulfonamides), cosmetics, and thiazine tranquilizers. Workers should review the medications they are or have been taking for photosensitivity side-effects.

• Coal tar and derivatives, certain dyes, and chlorinated hydrocarbons.

The total exposure to solar UV radiation during outdoor work depends on: 

• Geographical location: UV rays are stronger in locations nearer to the equator.

• Altitude: UV rays are much stronger at higher altitudes.

• Time of year: UV rays are strongest during summer months. The nearer the equator, the stronger UV rays are year round.

• Time of the day: highest levels are between 11 AM and 2 PM or when your shadow is shorter than you are.

• Cloud cover: over 90% of UV rays can pass through light cloud cover and still cause sunburn.

• Pattern and length of exposure – exposure can occur in an ongoing episode or via a series of shorter episodes which accumulate over time.

• Availability and use of control measures

• The presence of reflective surfaces

• The presence of photosensitisers

Everybody is different when it comes to susceptibility to harmful UV radiation. You should take more care in the sun if you have one or more of the following:

• skin that burns easily

• light or fair colored skin, hair, or eyes

• lots of moles or freckles

• a history of sunburn

• a personal or family history of skin cancer

You’re the best person to know how your skin reacts in the sun. The more easily you get sunburnt, the more careful you need to be. Remember, you don’t need to peel - if you skin has gone red or pink in the sun, that’s sunburn, and it’s dangerous

People with naturally dark brown or black skin burn less easily and have lower risk of skin cancer, but people with darker skin can still burn. It doesn’t need to peel - if your skin feels irritated, tender, or itchy, that’s sunburn.

Health Effects of UV Radiation

Exposure to solar UV radiation is known to cause adverse health effects on the skin, eyes and immune system. People who are overexposed to UV radiation may be unaware of their injury as it cannot be immediately seen or felt. The more UV exposure, the worse the sunburn becomes. A person’s cumulative exposure to UV radiation along with the number of severe sunburns they have received, especially during childhood, increases their risk of developing skin cancer. Sun exposure causes the outer layers of the skin to thicken and long-term exposure can cause skin to wrinkle, sag and become leathery. 

SKIN CANCER

The most serious health effect of exposure to solar UV rays is skin cancer. The top layer of the skin contains three different types of cells. Skin cancers are named after the skin cell where the cancer develops. The three types of skin cancer are:

1. Basal cell carcinoma (BCC) is the most common type of skin cancer. It grows slowly over months and years and may damage nearby tissues and organs if left untreated.

2. Squamous cell carcinoma (SCC) is less common but grows faster. It may spread to other parts of the body if left untreated.

3. Melanoma is the least common but most dangerous type of skin cancer. Most skin cancer deaths are from melanoma. It is often fast growing and can spread to other parts of the body where it can form a new cancer. Melanoma may be related to severe exposure to solar UV radiation at an early age. Malignant melanomas may appear without warning as a dark mole or a dark spot on the skin.

The amount of exposure required to cause skin cancer varies from one person to another. In most people the risk of skin cancer increases with increasing amounts of exposure to the sun. Exposure to solar UV radiation is the cause of about 99 percent of non-melanoma skin cancers and 95 percent of melanoma. A small number of skin cancers are from a genetic predisposition. Both melanoma and non-melanoma skin cancers can appear anywhere on the body, not just sun exposed areas.

SUNBURN

Sunburn can occur in as little as 15 minutes. Sunburn, whether serious or mild, can cause permanent and irreversible skin damage. Mild sunburn that reddens and inflames the skin is known as first-degree sunburn. Second-degree sunburn occurs with more serious reddening of the skin and water blisters. Third-degree sunburn requires medical attention.

EYE DAMAGE

The eyes are particularly sensitive to UV radiation. 

Acute effects of exposure to solar radiation on the eye include: 

• photokeratitis—inflammation of the cornea and the iris 

• photoconjunctivitis—inflammation of the conjunctiva membrane lining the inside of the eyelids and white of the eye. It is commonly known as snow blindness or welder’s flash.

Ongoing exposure to solar UV radiation contributes to age-related macular degeneration and cataracts. Both of which, without intervention, lead to blindness.

Action Plan to Reduce UV exposure:

• Engineering controls: instal a sun shade. 

• Administrative controls: rotating jobs and varying tasks. Saving the work indoors or under shade for the hottest part of the day.

• Taking rest breaks in cooler, shaded, or indoor areas

• Personal protective equipment (PPE): sun protective work clothing, hats, sunglasses (polaroid are better) and sunscreen (check the sun protection factor (SPF) is high enough and apply sunscreen regularly). You should select material and a design that provides sun protection while keeping you cool in hot conditions.

• Where available, consider the UV Index Alert each day, for example printing out the forecast and leaving it in shared areas and encouraging workers to check the alert on their phone or in the newspaper. 

• Use a combination of the above.

Implement the most effective control measures that are reasonably practicable in the circumstances and review control measures to ensure they are working as planned. Make sure any control measures to reduce UV exposure don’t increase the risk of other hazards. For instance, loose fitting clothing can be dangerous when using power tools; heavy clothing worn for sun protection can contribute to the risk of overheating. 

External links for more information:

Canadian Centre for Occupational Health and Safety - UV Radiation

Safe Work Australia - Guide to Solar UVR

Australian Radiation Protection and Nuclear Safety Agency - UV Radiation

Cancer Research UK - Sun, UV, and Cancer

OSHA - Working in Warm Climates