HARMFUL RADIATIONS THAT CAUSES CANCER

Ultraviolet (UV) radiation is a form of electromagnetic radiation that comes from the sun and man-made sources like tanning beds and welding torches.

There are different types of radiations, ranging from very high radiation like gamma and X-rays to very low-energy radiation like radio waves. UV rays have more energy than visible light, but not as much as x-rays and in the middle of this spectrum.

Higher-energy UV rays are a form of ionizing radiation. This means they have enough energy to remove (ionize) an electron from an atom or molecule. Ionizing radiation can damage the DNA (genes) in cells, which in turn may lead to cancer. The highest-energy UV rays though don’t have enough energy to penetrate deeply into the body, so they mainly effect the skin.

UV radiation is divided into 3 main groups:

• UVA rays have the least energy among UV rays. These rays can cause skin cells to age and can cause some indirect damage to cells’ DNA. UVA rays are mainly linked to long-term skin damage such as wrinkles, but they are also thought to play a role in some skin cancers.
• UVB rays have slightly more energy than UVA rays, and can damage directly the DNA in skin cells. They are the main rays that causes sunburns. And also most skin cancers.
• UVC rays have more energy than the other types of UV rays. Fortunately, because of this, they react with ozone layer in the atmosphere and don’t reach the ground, so they are not normally a risk factor for skin cancer. Some man-made sources, such as arc welding torches, mercury lamps, and UV sanitizing bulbs used to kill bacteria and other germs also produce UVC rays.

Exposure to UV Radiation

Sunlight

Sunlight is the main source of UV radiation, even though UV rays make up only a small portion of the sun’s rays. Different types of UV rays reach the ground in different amounts. About 95% of the UV rays from the sun that reach the ground are UVA rays, with the remaining 5% being UVB rays.

UV rays reaching the ground depends on a number of factors, such as:

• Time of the day: UV rays are strongest between 10 am and 4 pm.
• Time of the year: UV rays are stronger during spring and summer months. This is less of a factor near the equator.
• Expanse from the equator (latitude): UV exposure goes down as you get farther from the equator.
• Height above sea level: More UV rays reach the ground at higher elevations.
• Clouds:  UV rays can get through to the ground, even on a cloudy day.
• Reflection off surfaces: UV rays can bounce off surfaces like water, sand, snow, pavement, or even grass, leading to an increase in UV exposure.
• Contents of the air: Ozone in the upper atmosphere, for example, filters out some UV radiation.

The amount of UV exposure a person gets depends on the strength of the rays, the length of time the skin is exposed, and whether the skin is protected with clothing or sunscreen.

Man-made sources of UV rays

Man-made sources can also be expose people to of UV rays. They include:

• Sunbeds and sunlamps (tanning beds and booths): The amount and type of UV radiation someone is exposed to from a tanning bed (or booth) depends on the specific lamps used in the bed, how long a person stays in the bed, and how many times the person uses it. Most modern UV tanning beds emit mostly UVA rays, with the rest being UVB.
• Phototherapy (UV therapy): Some skin problems (such as psoriasis) are helped by treatment with UV light. For a treatment known as PUVA, a drug called a psoralen is given first. The drug collects in the skin and makes it more sensitive to UV. Then the patient is treated with UVA radiation. Another treatment option is the use of UVB alone (without a drug).
• Black-light lamps: These lamps use bulbs that give off UV rays (mostly UVA). The bulb also gives off some visible light, but it has a filter that blocks most of that out while letting the UV rays through. These bulbs have a purple glow and are used to view fluorescent material. Bug-zapping insect traps also use “black light” that gives off some UV rays, but the bulbs use a different filter that causes them to glow blue.
• Mercury-vapor lamps: Mercury-vapor lamps can be used to light large public areas such as streets or gyms. They do not expose people to UV rays if they are working properly. They are actually made up of 2 bulbs: an inner bulb that emits light and UV rays, and an outer bulb that filters out the UV. UV exposure can only occur if the outer bulb is broken. Some mercury-vapor lamps are designed to turn themselves off when the outer bulb breaks. The ones that don’t have this feature are only supposed to be installed behind a protective layer or in areas where people wouldn’t be exposed if part of the bulb breaks.
• High-pressure xenon and xenon-mercury arc lamps, plasma torches, and welding arcs: Xenon and xenon-mercury arc lamps are used as sources of light and UV rays for many things, such as UV “curing” (of inks, coatings, etc.), disinfection, to simulate sunlight (to test solar panels, for example), and even in some car headlights. Most of these, along with plasma torches and welding arcs, are mainly of concern in terms of workplace UV exposure.

UV causes cancer

Most skin cancers are a result of exposure to the UV rays in sunlight. The risk of melanoma, a more serious but less common type of skin cancer, is also related to sun exposure, although perhaps not as strongly. Skin cancer has also been linked to exposure to some man-made sources of UV rays as discussed above.

Many studies have found that basal and squamous cell skin cancers are linked to certain behaviors that put people in the sun, as well as a number of markers of sun exposure, such as:

• Spending time in the sun for recreation
• Spending a lot of time in the sun in a swimsuit
• Living in an area that gets a lot of sunlight
• Having had serious sunburns in the past (with more sunburns linked to a higher risk)
• Having signs of sun damage to the skin, such as liver spots, actinic keratoses (rough skin patches that can be precancerous), and solar elastosis (thickened, dry, wrinkled skin caused by sun exposure) on the neck

Studies have also found links between certain behaviors and markers of sun exposure and melanoma of the skin, including:

• Activities that lead to “intermittent sun exposure,” like sunbathing, water sports, and taking vacations in sunny places
• Previous sunburns
• Signs of sun damage to the skin, such as liver spots, actinic keratoses, and solar elastosis

Because UV rays don’t penetrate deeply into the body, they wouldn’t be expected to cause cancer in internal organs, and most research has not found such links. However, some studies have shown possible links to some other cancers, including Merkel cell carcinoma, which is a less common type of skin cancer and melanoma of the eye.

Studies have found that people who use tanning beds (or booths) have a higher risk of skin cancer, including melanoma and squamous and basal cell skin cancers. The risk of melanoma is higher if the person started indoor tanning before age 30 or 35, and the risk of basal and squamous cell skin cancer is higher if indoor tanning started before age 25.

The International Agency for Research on Cancer (IARC) is part of the World Health Organization (WHO). One of its major goals is to identify causes of cancer. Based on the available data, IARC has made the following determinations:

• Solar radiation is carcinogenic to humans.
• Use of UV-emitting tanning devices is carcinogenic to humans.
• UV radiation (including UVA, UVB, and UVC) is carcinogenic to humans.

The FDA has also proposed a new rule to ban the use of indoor tanning devices by anyone under age 18, to require tanning facilities to inform adult users about the health risks of indoor tanning, and to require a signed risk acknowledgment from all users.  Some US states have already banned indoor tanning by all people younger than 18, while others have banned use by younger teens and children.

UV rays and vitamin D

Your skin makes vitamin D naturally when it is exposed to UV rays from the sun. The amount of vitamin D the skin makes depends on many things, including the age, how dark the skin is, and how strong the sunlight is.

Vitamin D has many health benefits. It might even help lower the risk of some cancers. At this time, doctors aren’t sure what the optimal level of vitamin D is, but a lot of research is being done in this area.

Ways to Help Reduce Exposure to UV Radiation

Some of the ways to help ensure you’re not getting too much sun:

• If you’re going to be outside, simply staying in the shade, especially during midday hours, is one of the best ways to limit your UV exposure from sunlight.
• Protect your skin with clothing that covers your arms and legs.
• Wear a hat to protect your head, face, and neck.
• Wear sunglasses that block UV rays to protect your eyes and the skin around them.
• Use sunscreen to help protect skin that isn’t covered with clothing.