Ultraviolet how is it made

Exposure to fluids from these plants, especially if crushed, followed by exposure to sunlight can cause dermatitis. Citrus fruit handlers and vegetable harvesters, gardeners, florists and bartenders are at risk for experiencing dermatitis following exposure to certain plants and then to sunlight phytophotodermatitis.

Effects of repeated exposures chronic effects include skin aging and skin cancer. There is a strong causal link between skin cancer and prolonged exposure to solar UV and from artificial sources. The eyes are particularly sensitive to UV radiation. Even a short exposure of a few seconds can result in a painful, but temporary condition known as photokeratitis and conjunctivitis. Photokeratitis is a painful condition caused by the inflammation of the cornea of the eye. The eye waters and vision is blurred.

Conjunctivitis is the inflammation of the conjunctiva the membrane that covers the inside of the eyelids and the sclera, the white part of the eyeball ; see Figure 3 which becomes swollen and produces a watery discharge.

It causes discomfort rather than pain and does not usually affect vision. Examples of eye disorders resulting from UV exposure include "flash burn", "ground-glass eye ball", "welder's flash" and "snow blindness" - depending on the source of the UV light causing the injury.

The symptoms are pain, discomfort similar to the feeling of sand in the eye and an aversion to bright light. Maximum absorption by the cornea occurs around nm. Absorption of UV-A in the lens may be a factor in producing cataract a clouding of the lens in the eye.

A variety of instruments are commercially available for measuring UV radiation in the laboratory and in the workplace. Specifications and purchasing information can be obtained from suppliers of workplace monitoring equipment.

There are no Canadian regulatory occupational exposure limits for UV radiation. These limits are given below:. For the UV-A or near ultraviolet spectral region to nm , exposure to the eye should not exceed 1 milliwatt per square centimeter 1. For exposure times less than seconds, the dose total energy should not exceed 1. Additional exposure limits apply to the amount of UV light exposure to the skin and the eyes. The amount of UV exposure a person can receive on their skin or eyes during an 8-hour period varies with the wavelength of the UV radiation.

UV radiation is invisible and therefore does not stimulate the natural defenses of the eyes. Workers must use eye and skin protection while working with UV radiation sources which present the potential of eye harmful exposure. The selection of eye protection depends on the type and intensity of the UV source. UV radiation is easily absorbed in a variety of materials. Shielding is usually easy to design.

Mercury lamps and metal halide lamps have an outer glass cover to stop UV radiation, and are designed such that if the outer glass is broken, the lamp ceases to function. Certain industrial chemical pollutants in the atmosphere are gradually eroding earth's protective shield ozone layer which stops the sun's UV radiation from reaching the earth.

In recent years, there has been growing concern about increasing levels of UV radiation in the sunlight, especially during the summer months.

Excessive exposure to ultraviolet rays can cause skin cancer and eye cataracts. However, only about 10 percent of sunlight is UV, and only about one-third of this penetrates the atmosphere to reach the ground, according to the National Toxicology Program NTP.

No measurable UVC from solar radiation reaches the Earth's surface, because ozone, molecular oxygen and water vapor in the upper atmosphere completely absorb the shortest UV wavelengths. A suntan is a reaction to exposure to harmful UVB rays. Essentially, a suntan results from the body's natural defense mechanism kicking in.

This consists of a pigment called melanin, which is produced by cells in the skin called melanocytes. Melanin absorbs UV light and dissipates it as heat. When the body senses sun damage, it sends melanin into surrounding cells and tries to protect them from sustaining more damage.

The pigment causes the skin to darken. However, continued exposure to UV radiation can overwhelm the body's defenses. When this happens, a toxic reaction occurs, resulting in sunburn.

UV rays can damage the DNA in the body's cells. The body senses this destruction and floods the area with blood to help with the healing process. Painful inflammation occurs as well. Usually within half a day of overindulging in the sun, the characteristic red-lobster look of a sunburn begins to make itself known, and felt. Sometimes the cells with DNA mutated by the sun's rays turn into problem cells that don't die but keep proliferating as cancers. The difference in how the galaxies appear is due to which type of stars shine brightest in the optical and ultraviolet wavelengths.

Ultraviolet images of galaxies show mainly clouds of gas containing newly formed stars that are many times more massive than the Sun and glow strongly in ultraviolet light. In contrast, visible light images of galaxies show mostly the yellow and red light of older stars. By comparing these types of data, astronomers can learn about the structure and evolution of galaxies. Chemical processes in the upper atmosphere can affect the amount of atmospheric ozone that shields life at the surface from most of the Sun's harmful UV radiation.

Each year, a "hole" of thinning atmospheric ozone expands over Antarctica, sometimes extending over populated areas of South America and exposing them to increased levels of harmful UV rays. The image above shows the amount of atmospheric ozone in Dobson Units—the common unit for measuring ozone concentration. These data enable scientists to estimate the amount of UV radiation reaching the Earth's surface and forecast high-UV-index days for public health awareness.

Aurorae are caused by high-energy waves that travel along a planet's magnetic poles, where they excite atmospheric gases and cause them to glow. Photons in this high-energy radiation bump into atoms of gases in the atmosphere causing electrons in the atoms to excite, or move to the atom's upper shells.

When the electrons move back down to a lower shell, the energy is released as light, and the atom returns to a relaxed state. The color of this light can reveal what type of atom was excited.

Green light indicates oxygen at lower altitudes. Red light can be from oxygen molecules at a higher altitude or from nitrogen. On Earth, aurorae around the north pole are called the Northern Lights. Therefore, exposure to a high dose or prolonged low dose of radiation from some UVC lamps can potentially contribute to effects like cataracts or skin cancer that are caused by cumulative exposure to UVB radiation.

Additionally, some UVC lamps generate ozone which could cause irritation to breathing passages that is nose, throat, and lungs , particularly for those who have respiratory sensitivity such as asthma or allergies.

Exposure to high levels of ozone gas may also worsen chronic respiratory diseases, such as asthma, or increase vulnerability to respiratory infection. Sunburn is a sign of short-term overexposure, while premature aging and skin cancer are side effects of prolonged UV exposure. Certain oral and topical medicines, such as antibiotics, birth control pills, and benzoyl peroxide products, as well as some cosmetics, may increase skin and eye sensitivity to UV in all skin types.

Check the label and ask your doctor for more information. More information on the Risks of Tanning. Exposure to UVB radiation helps the skin produce a type of vitamin D, vitamin D3 , which plays an important role - along with calcium - in bone and muscle health.

However, the amount of UVB exposure needed to obtain a benefit depends on several factors, such as: the amount of vitamin D in your diet, skin color, sunscreen use, clothing, where you live latitude and altitude , time of day, and time of year. UV radiation, in the form of lasers, lamps, or a combination of these devices and topical medications that increase UV sensitivity, are sometimes used to treat patients with certain diseases who have not responded to other methods of therapy.

Also known as phototherapy, this method of UV exposure is performed by a trained healthcare professional under the supervision of a dermatologist. Studies suggest that phototherapy can help treat unresponsive and severe cases of several diseases, including:.

Phototherapy involves exposing a patient to a carefully monitored dose of UV radiation on a regular schedule. While this type of therapy does not eliminate the negative side-effects of UV exposure, treatment is carefully supervised by a doctor to ensure that the benefits outweigh the risks.

UV rays are strongest in areas close to the equator. Because the sun is directly over the equator, UV rays only travel a short distance through the atmosphere to reach these areas. UV radiation is also the strongest near the equator because ozone in these areas is naturally thinner, so there is less to absorb the UV radiation. UV exposure is lower in areas further from the equator because the sun is farther away.