EPA \ TAQMN \ UV Monitoring \ Information


What are UV Rays?

Sunlight and UV Rays

Sunlight is the source of energy for the majority of living organisms on earth, and is also the original force that forms the ozone. Before discussing the forming of the ozone, we must first describe the various types of rays in sunlight. According to physics, different characteristic rays are due to their difference in wavelength. The various rays in the light spectrum from shortest to longest are cosmic rays, γ rays, X rays, UV rays, visible light, infrared, microwaves (the rays used in the home appliance, the microwave), radio shortwaves, radio waves, and radio long waves. These waves are differentiated by length but they also overlap slightly with each other, so we must decide according to their actual attributes. For instance, cosmic rays have a wavelength of 0.00005nm, while the longest ray can reach lengths over 220,000nm. Wavelengths visible to the naked eye are between 400 to 700nm, but the clearest type of light is at 556nm, which is in the range of green, close to yellow which is why green is an especially clear color for humans. The spectrum of sunlight ranges from UV rays to infrared, with the longest wavelength being 4,000nm. In terms of energy however, the rays range mostly in the spectrum of visible light at about 50%, with ultraviolet rays taking 7%, and infrared rays being 43%.

Types of UV Rays

UV rays are a type of electromagnetic wave from the sun, and UV rays are categorized by 3 types according to wavelength:

UV Ray Types Wavelength (nm)
UV-C 100-280
UV-B 280-315
UV-A 315-400

UV Rays and the Weather

With the changes in season, sunlight shines at different regions in different angles, which is why the strength of UV rays on earth's surface will differ. In the northern hemisphere, the strongest UV rays occur in June, while the weakest occur in December. Similarly, due to the different angles of sunlight, regions closer to the equator will have a higher UVI.

In terms of the weather, clouds are an obstacle to prevent UV rays from reaching earth's surface; therefore, the thicker the clouds the more difficult it is for UV rays to reach the surface.

The Shifting Ozone

What is the Ozone

(1) The Earth's Ozone

The ozone that surrounds earth does not have a set boundary. The further from earth, the thinner the ozone becomes to the point of becoming a vacuum until reaching galactic space. In 1962 the WMO divided the ozone by temperature into four layers, which includes the troposphere, stratosphere, mesosphere, and warming layer.

The troposphere includes the 1.5~2.0 km area near the surface caused by irregular friction with the ground reaching upwards from the boundary layer. The stratosphere is approximately 7~8 km above the poles and can reach up to 16~19 km above the equator. Temperature within the troposphere decreases by approximately 6.5 ℃ per kilometer and almost all human activity is centered in this layer of the ozone.

The stratosphere mainly exists between 15~50 km above ground and the temperature decrease described above stops at this layer and gradually increases after this layer.

Above the stratosphere is the mesosphere which exists between 50~100 km above ground, and at this layer the temperature lowers with the altitude. Above this is the warming layer which is 100~400km above ground, at which the temperature once again increases with the altitude.

(2)What is the Ozone

Ozone (O3)is a light blue gas with an irritating odor made up of three oxygen atoms with a molecular formula of O3. In the stratosphere, oxygen molecules break down into oxygen atoms due to high energy ultraviolet radiation and the oxygen atom combines with one oxygen molecule O2 to form ozone. In the stratosphere, the ozone is formed through the process below:

  1. O2+UV (wavelength less than 240nm) → O+O (produces oxygen atoms)
  2. O+O2 → O3 (Becomes ozone)

In the troposphere, ozone can be formed through man-made pollution, including nitrogen oxide, hydrocarbons and others, which after being exposed to sunlight form a chemical reaction and create ozone. Furthermore, ozone can also be created through man-made methods by combining high voltage electricity with air or pure oxygen.

As ozone possesses strong oxidation properties, it is sometimes used to purify air or to sanitize and kill germs in drinking water, or to remove odors. However, ozone irritates the upper respiratory tract mucosa, the eyes, asthma, and causes respiratory functions to decrease and is detrimental to human health which is why ozone created from secondary reactions in air pollutants have become a target of regulation by environmental protection agencies. Methods of regulation include the reduction of nitrogen oxides and hydrocarbons, so when using man-made ozone one must be in constant control to prevent additional ozone from escaping into the air and affecting human health.

(3) Ozone Layer and UV Rays

Oxygen molecules in the stratosphere absorbs ultraviolet and is broken down into oxygen atoms and oxygen atoms combine with oxygen molecules into ozone. UV absorption of ozone at this time and then broken down into oxygen molecules and atomic oxygen, the oxygen atoms combine with oxygen to form ozone molecules. Throughout the process ozone absorption and consumption of ozone not only to ultraviolet light is absorbed into heat energy, which is why in the stratosphere, with a high degree of temperature rise and the main reason. Ozone absorption of ultraviolet energy into the process, which is to protect the earth's surface from excessive ultraviolet injury mechanism, we have said in the stratospheric ozone for the ozone layer.

How thick is the ozone layer? According to estimates, if the ozone in our stratosphere is in an environment of 0 degrees Celsius and pressure is applied, the thickness of the ozone layer would be a mere few millimeters. Therefore when calculating the thickness of the ozone layer it is compressed in a 0 degree Celcius environment with 1 millimeter of thickness equaling 1 DU (Dobson Unit), with 1 DU being approximately 2.7x1016 molecules/square cm.

A Hole in the Ozone

According to studies, starting from 1978 and counting ten years forward the average ozone content at all longitudes has decreased by approximately 1.2% to 10%, with the area above the south pole being the most severe and showing what is commonly known as the “ozone hole” during spring time. If the human activities and industrial pollution which cause holes in the ozone layer continue to persist, the ozone content of the stratosphere will drastically decrease in the 21st century and pit mankind in an unprecedented disaster!

If industrial pollution and human activities such as the hole in the ozone layer caused by the persistence of factors, in the twenty-first century, stratospheric ozone concentration will be greatly reduced, then, will be facing an unprecedented human catastrophe!

1.The damage condition of the ozone layer

From the reports of World Meteorological Organization we have discovered that in the past 20 years, ozone observation instruments in Canada, middle Europe, and Japan have observed an annual average 1% decrease in the ozone content of the stratosphere, with the decrease in ozone being different at various altitudes. In 1995 a hole in the ozone layer the size of Europe formed above the south pole; in a report dated March of 1996, it was pointed out that the density of ozone in the northern hemisphere was also rapidly decreasing; between September and October of 1996, a hole in the ozone layer with an area of 220 million square km, twice the size of Europe, appeared over the south pole; in April of 1997, a report pointed out that the north pole's ozone layer had decreased by approximately 15%~25% compared to a year ago, with the most severely affected areas being the north pole and Siberia. The ozone layer is earth's protection, so what effects will it bring to earth's organisms and environment when it is thinned?

2.Why is there a hole in the ozone layer?

The ozone layer resides in the stratosphere and is formed through the radiation of ultraviolet rays to form the ozone layer which protects our earth, but how is it being damaged?

In 1970 Dutch scientist Paul Crutzen pointed out that some durable man made substances could be damaging the ozone layer. In 1974 American scientist Mario Molina and Sherwood Rowland proved that aerosol spray cans and chlorofluorocarbons (CFCs) in consumer appliances such as the refrigerator were severe enough to damage the ozone layer. Using freon-12, the substance used to keep refrigerators cold, as an example, its' molecular formula is CCI2F2. After being broken down by sunlight, it produces chlorine atoms (CI) as below:

CCl2F2 +hn →CCIF2+Cl.

Ccl2F2 +hn →・CCIF2+Cl

The chlorine atom destroys the ozone and produces nitric oxide:

CI+O3 →・ClO+O2

The nitric oxide and oxygen atom have the following reaction, return to chlorine atoms and can repeat the task of damaging the ozone:


It is estimated that in the average lifespan of a chlorine atom, it can damage 10,000 ozone molecules. If this situation persists, by 2050 the ozone layer will decrease by 16% and diseases due to severe radiation exposure will greatly increase. If the ozone layer is damaged by 30%, all types of radiation mentioned above will be able to reach earth's surface which will lead to dire consequences.

Table 1 shows CFCS and related substances that are currently in use. In terms of lifespan, the longest is freon115 which lasts 280 years, and substances with shorter life spans such as halon-1211 still last 52 years, giving them ample time to float into the ozone layer. Table 2.2.2 shows that the destructive force of these compounds aren't equal, with some being ten times as powerful as others.

CFCS are mainly produced by industrial countries in the northern hemisphere and it is true that the density of CFCS is higher in the northern hemisphere, but why has the biggest hole in the ozone layer appeared in the south pole and not in other places? Apparently the unique geography and climate of the south pole is closely related to the forming of the south pole.

During winter the vortex formed in the stratosphere above the poles obstructs the exchange of air, creating extreme conditions of low temperature (less than -80 degrees Celsius), which is beneficial for the formation of polar ice clouds. Through chemical reactions, CFCs form compounds such as CIONO2, BrONO2, and HCI which attach themselves to the surface of ice. When the spring sun appears, these compounds are converted to active CI, Br, or CIO. BrO causes surprising damage to O3. Although the north pole has similar conditions of O3 destruction, but it is not as sever as the south pole due to two reasons:

  1. The temperature of the stratosphere above the north pole is not usually less than -80 degrees Celsius.
  2. The stratospheric vortex over the north pole usually dissipates before spring, allowing air with O3 to enter to replenish lost O3.

3. What are CFCs

CFCs are the culprit that damage the ozone layer. Freon, a common compound that began production in the 1930s has permeated various industrial uses and items used in daily life due to its' strengths such as high stability, non self combustion, does not aid in combustion, does not easily produce chemical reactions, and is not as harmful to the human body. As it is highly stable, it must rise to the stratosphere before it can break down, which results in damage to the ozone layer.

The biggest use for CFCs is in refrigerants for appliances such as air conditioners and refrigerators. Another use is in aerosol cans, such as beauty products, pesticides, or paint. It can also be used as a foaming agent, such as styrofoam or as a cleaner for electronic products. The most used are CFC-11, CFC-12, and CFC-113 which are used in products such as:

  1. Foaming agent:
    Hard PU foam, soft PU foam, polystyrene (PS) foam and PE foam, such as CFC-11
  2. Refrigerant:
    Freezers, refrigerators, cars, air conditioner refrigerants such as CFC-11, CFC-12.
  3. Cleaning agents:
    Cleaner for circuit boards, semi-conductor materials, electronic and optical components such as CFC-113.
  4. Aerosols:
    Aerosol devices for make-up, medical supplies, and cleaning supplies such as CFC-11 and CFC-12.

Furthermore, halon is a full-halogenated CFC that is often used as an fire extinguishing agent due to its fire proofing abilities. However, the damage halon causes to the ozone is even higher than CFCs, requiring the use of halon to be closely monitored.

4. Montreal Protocol

As an understanding was reached in the fact that the continuous use of CFCs and other chemical substances will lead to the destruction of the earth's ozone layer, the U.N.'s environmental planning administration called on countries around the world to discuss strategy. In 1985 there were 28 countries who established an agreement to protect the ozone layer at the Vienna Convention and decided to create a set of international regulations to supplement the treaty. On September 16th of 1987, another international committee convened in Montreal, Canada at which 26 countries signed the Montreal Protocol on Substances that Deplete the Ozone Layer to regulate the use of CFCs and began in January of 1989. Subsequently in order to save the deteriorating condition of the ozone layer, the committee reconvened on June, 1990 to make amendments to the Montreal Protocol, focusing on expanding the list of regulated materials aside from the original (CFC-11, CFC-12, CFC-113, CFC-114, CFC115 and 3 types of halon) to add CFC-13 and ten others, carbon tetrachloride, and methyl chloroform to total twelve chemical substances. The time table for regulation was also sped up with plans to completely prohibit the use of CFCs, carbon tetrachloride, and halon in 2000. However, the conditions of the ozone layer continued to deteriorate which is why in November of 1992 the committee reconvened in Copenhagen to ban the use of CFCs starting January of 1996 to cut usage to zero (aside from necessary usage). As Taiwan is a part of the international community, a time table is in place to cut usage while strengthening the regulated use of chemicals while aggressively seeking substitutes to follow the global environmental trend.

With the collaborative efforts from government and industries, Taiwan's usage of restricted materials have been in step with the Montreal Protocol. Since 1994, usage of halon is zero and from 1996, the usage of restricted CFCs has also been reduced to zero.


Human Activity and Shifts in the Environment

Since the economic growth of the industrial revolution, the living standards of humans have continued to increase, as have our demands for energy. The pollution produced from various industrial processes have also continued to destroy the environment and habitats that humans rely on to survive. We have previously introduced problems that we as humans have to face, such as the use of CFCs causing the destruction of the ozone layer and causing harmful UV rays to reach the earth's surface. In reality, the pollution caused by humans is a global problem that causes the greenhouse effect and acid rain. These are all problems that we should be deeply concerned with.

1.Greenhouse Effect

The greenhouse effect is caused by atmospheric gases such as carbon dioxide, methane, fluorocarbon and other compounds and it is estimated that half to three quarters of the greenhouse effect is from carbon dioxide. Since the 1980s, scientists have gradually confirmed that the long term use of fossil fuels has gradually increased the density of greenhouse gases in the atmosphere to destroy the balance of natural heat on earth, raising average temperatures and causing climate shifts, the melting of the polar ice caps and the rise of sea water levels. Coastal lands, towns, or islands now face the threat of being drowned by the sea. In 1992 the United Nations passed a climate shift treaty and in the same year at the Earth Summit in Rio, Brazil 155 countries signed the treaty which began effect in March of 1994. Currently there are over 165 countries who have approved of this treaty. In 1995 and 1996 the first and second meeting of treatise countries were held in Berlin and Geneva. Most recently in 1997 during the third meeting, the Kyoto Protocol was proposed to reduce the emission of greenhouse gases in order to stop the deteriorating conditions of the global climate.

2.Acid Rain

The problem of acid rain is not foreign to Taiwan. The normal pH of rain water is 5.6, but due to air pollution caused by the oxidation of nitrogen and sulfur oxides the pH value of rain water has dropped below 5.6, which is at the levels of acid rain. Acid rain can cause problems such as the acidification of earth's surface, the death of fish and shellfish, obstruct the growth of vegetation, damage forests, and the corrosion and discoloration of buildings. It is estimated that two thirds of acid rain is caused by sulfur dioxide, while one third is caused by nitrous oxides. Aside from rain, acidic matter in the air can also settle through other means which is why acidic settlements include the settlement of all acidic matter. As acidic settlement moves with the atmosphere and can create international problems, cooperation between countries is essential to reduce the emission of air pollutants. Normally speaking, reducing the usage of sulfur dioxide is easier and less costly while the regulation of nitrous oxides is more difficult.

Other problems such as decreasing rain forests, desertification, the spread of harmful substances and the loss of biological diversity are all man-made global environmental problems that need to be addressed by mankind as a whole for a sustainable future.


Characteristics of Common CFCs

Name Lifespan (Years) Relative Ozone Destruction Index
Refrigerant Freon11 (CFC13) 62 1
Freon12 (CF2C12) 130 1
Freon113(C2F3CI3) 90 0.8
Freon114(C2F4CI2) 180 1
 Freon115(C2F5CI) 380 0.6
Halon1211(CF2BrCl) 52 3
Halon1301(CF3Br) 110 10

Relationship Between UV Rays and Health

Body Growth

1.Vitamin D3

Appropriate exposure to ultraviolet rays is positive for health, as UV rays react with cholesterol stored in our skin to create vitamin D3. What is the purpose of vitamin D3? It can strengthen our absorption of calcium and phosphor, which are both elements that create our bone structure. A person who lacks vitamin D3 (light synthetic vitamin) is white and is not often exposed to the sun and will have bad bones which are possibly too soft, increasing their probability of bone fracture. A small amount of exposure to sunlight is good! Have you remembered to sunbathe?

2.Medical Uses

Ultraviolet rays can also be used in medical environments to kill germs, reduce inflammation, help wounds heal, treat tuberculosis, and other uses. Usually UV rays with short wavelengths (about 250~260nm) have characteristics of breaking down chromosomes to sterilize or disinfect. Some drinking water can also be sterilized with UV rays using these characteristics.



1.Sun burn

The continuous destruction of the ozone layer has increased the amount of harmful UV rays (UV-B) and the amount of patients with skin cancer in Europe, America, and other regions have been increasing. When the skin is directly exposed to UV rays without any protection, if the UVI index is above standard values and you are active under the sun wearing short sleeves without any protection such as sun screen, a hat, or an umbrella, you can be sun burnt within 20 minutes. However, different people react differently to UV rays. Usually fair skinned Caucasians are easily damaged by UV rays. In May of 1997 America pushed the principle that “sunlight during childhood creates skin cancer during adulthoo”being that damage caused from exposure to sunlight at the agof 18 leads to skin cancer at a later age.


2.Skin lesions

Exposure to sunlight and UV rays can easily lead to lesion of the skin cells and solar foliation, causing the skin to become thick, red, and rough. These symptoms often occur on the hands, fore arms, and neck. When exposure time and frequency is extended, solar foliation can further form squamous cell carcinoma, basal cell carcinoma, or melanoma.


1.Protective Measures of the Eyes

In terms of eyes, exposure to UV rays offer no benefits but chronic or acute effects can be prevented. The eyes are naturally protected against the effects of UV rays by the ways eyes are set and the depression of the eye sockets which both effectively reduce the radiation from UV rays. When bright light is shone on the face, the eyes react involuntarily and blink to provide another source of protection.

2.Damage to the Eyes

When UV rays cause damage to eyes, the affected area is usually in the lens and around the eyes which can lead to skin cancer around the eyes or mutation and deterioration of the retina. In severe cases the transparency of the lens can be damaged and lead to blindness. Acute corneal epithelial lesions caused by UV rays often occur within 6 hours of exposure. This can occur in cases such as not wearing appropriate protective goggles during welding or chronic activities on snow plains or waterfronts where UV rays are reflected. The eyes will suffer from pain, tearing, photo phobia, redness and swelling, blurred visibility, and other symptoms.

3. Cataract

The relationship between UV rays and cataracts are often discussed. Cataracts refer to the turbidity of the lens which leads to obstructed vision. Over exposure to UV rays will lead to the oxidation of protein within the lens of the eye causing the lens to become murky and obstruct vision.

Patients who have endured cataract surgeries are more likely to gain retinal and macular lesions as they lack the original lens which filters the effects of UV rays. Although man-made lenses can now be implanted in the eye, surgery patients should remain vigilant to protect themselves from UV rays.

Immune System

UV rays suppress the immune abilities of cells, leading to the destruction of DNA, isomeric amino acids, and the fast metabolism of vitamins. White blood cells are reduced in effectiveness when exposed to sunlight as UV rays causes them to fail, which leads to damage of the immune system. Even those with dark skin can easily harm the immune mechanisms of their body.

Damage to the immune system will show locally in the skin, and sometimes systematically all over the body. In severe cases, cancer may occur.

How to Avoid UV Ray Damage

UVI Index

1.UVI Index

The radiation of UV rays is closely linked to the sun's angle. At noon (when the sun is at 0 degrees), the strength of UV radiation peaks. In order to protect the public from UV radiation damage, daily UVI index is defined by radiation calculated at noon.

2.UVI Index Levels

Currently Taiwan has categorized UVI into levels according to their effect on human health: Levels lower than 2 are micro, 3~5 are low, 6~7 are medium, 8~10 are high, while values more than 11 are at the dangerous level.

The Weather and UVI Index

1.Elements that affect the strength of UV rays

The sun's angle will differ with the seasons, with summer being the season with the highest radiation because the sunlight shines from a higher angle. In the northern hemisphere, June to August are the months with highest UV ray strength levels; the weakest occur from December to February. According to geographical position, as the sun's angle is different, areas closer to the equator have a higher UVI index. Also, cloud volume, ozone layer thickness, and air pollution are all factors that affect the strength of UV rays.

2.Cloud volume and UVI index levels

From long term monitoring results, it's known that during summer weather the relationship with UVI index is as follows: heavy rain and overcast days are micro levels, overcast to cloudy days are low, cloudy to scattered clouds is medium, scattered clouds to little clouds is high, while cloudless days are at the dangerous level. As the sun's angle is larger during spring and autumn, UV radiation levels are weaker than the summer months and the relationship between weather and UVI index should be lowered 1-2 indexes, with winter months being only 1 level: heavy rain and overcast days are micro level, cloudy days to scattered clouds are low, and so on.

Preventative Measures Against UV Rays

1.UV levels and preventative measures

When the UVI index is between micro and low, there is no need to take preventative measures for outdoor activities between 1-2 hours, medium level UVI index will harm the body, such as the skin or eyes, within 30 minutes so it is necessary to wear a hat, use an umbrella, wear sunglasses, or use suntan lotion while staying under shade. High or dangerous levels of radiation will harm the body within 15-20 minutes so the preventative measures listed above should be taken while avoiding direct exposure of the skin by wearing long sleeves and avoiding going outdoors between the hours of 10 AM and 2 PM.

The Environmental Protection Administration uses UVI to categorize the strength of UV rays to educate the public. Starting in July of 1998 next day forecast of the UVI index was begun to remind the public to take appropriate preventative measures.

2.Common sense in UV ray protection

Noon is when the UVI index is at its strongest and by wearing hats, t-shirts or thick clothing 90% of the UV rays can be reduced; furthermore, when doing outdoor activities by the beach, even when using high SPF suntan lotion, you must re-apply suntan lotion after awhile or avoid long hours of outdoor activities.

Wearing a hat, sunglasses, using an umbrella, or wearing long sleeves is the optimal outfit to prevent UV ray damage. When working under the scorching sun, avoid direct exposure to the skin and wear long sleeved shirts and large brimmed hats to defend against UV rays. Also, UV protected sunglasses are best for the eyes, especially when working long hours under the sun.

When going out under the scorching sun, remember to use suntan lotion and if continuous activity is required under the sun remember to re-apply every 2-3 hours; furthermore, sweat reduces the effectiveness of suntan lotion so remember to routinely reapply lotion, especially when in beach areas. Remember that any item that prevents damage only works partially, and suntan lotion only works for a short period. Take preventative measures diligently or avoid activities under the sun.

The UV rays reflected by snow plains and beaches are even more harmful for the eyes. Snowy plains reflect 80% and beaches reflect 17%, so wear sunglasses with UV filtering properties to protect the eyes against UV ray damage.

3.Personal risk assessment of UV rays

There is an old proverb that says prevention is better than curing. Here are guidelines to use as reference for personal examination to understand the health risks of exposure to the sun and to detect symptoms before they occur in the skin.

[Personal Risk Assessment of UV Rays Table]

Risk of skin cancer depends on personal skin type, degree and total exposure under the sun. Would you like to understand your skin sensitivity? Answer “Yes” or “No” for the questions below.

1.My skin is very white

2.I grow freckles easily

3.When I was a child, I grew blisters from being sunburned(more than twice)

4.I lived mostly in middle and southern Taiwan as a child

5.I served in the military and often stayed outdoors

6.I used to help in the field planting crops

7.I work outdoors

8.I partake in many outdoor activities

9.I expose my sunlight as frequently as possible

10.A family member has had skin cancer

“Yes” answers receive 10 points.

If you have done any kind of artificial tanning add another 10 points.

80~100 – High danger: Avoid sunlight as much as possible in the future, use suntan lotion outdoors, and wear clothes to reduce exposure.

40~70 – Dangerous: Use suntan lotion often, wear hats, and avoid exposure to sunlight at noon.

10~30 – Slightly dangerous: Often keep in mind the UVI index report.

4.Care products to protect against UV rays

UV-B in UV rays can cause the skin to be burned, red, and swollen. The SPF of in make-up with sunscreen is often expressed with the extend time it takes for UV-B to damage the skin; lately, as it has been discovered that UV-A can penetrate the dermis to cause skin to become black, age, lose firmness, and grow wrinkly which is why protection against UV-A rays has become a growing concern. As UV-C can barely reach the surface, it is negligible.

The skin care products on the market that defend against UV rays can be categorized into two major types depending on their mechanism. Chemical based sunscreen is often composed such as amino acid esters, cinnamate and diphenyl ketone are mainly used to absorb UV rays; physical based sunscreen is often composed of titanium dioxide and zinc oxide which are mainly used to reflect or scatter UV rays. When using physical based sunscreen, it is less irritating to the skin and suitable for children. Products on the market that only rely on physical based defense is in the minority, as most products mix chemical and physical based protection to increase effectiveness against UV-A.

There are no global standard indexes in determining effectiveness of sunscreen, so be wary when purchasing. Below are descriptions of common indexes:

1.SPF: Sun Protection Factor is the American index.Sunscreen effects are SPF*10 (minutes), so SPF15 is 15*10=150 minutes.

2. IP: Indicia Protection is the European index. IP*1.5=SPF, so IP10=SPF15.

3. PA+: Protection Grade of UVA is the mandatory label for all Japanese products describing their UV-A protection abilities. PA+ is light protection, PA++ is medium protection, and PA+++ is strong protection.

The Role of UV Rays in Nature

Remote satellites have discovered that the ozone layer has been depleting for the past twenty years, leading to an increase in UV radiation which destroys the primitive balance of nature and aside from being harmful for the health of humans, the increase of harmful UV rays has gradually affected the balance of nature.

UVI Index Categories, Preventative Measures for Sun Exposure

UVI Index Level Time Preventative Measures
0~2 Low    
3~5 Moderate    
6~7 High Within 30 min hat/umbrella +sunscreen +sunglasses +stay under the shade
8~10 Very high Within 20 min hat/umbrella +sunscreen +sunglasses +shade +long sleeved clothing +avoid going outdoors between 10 AM and 2 PM
11+ Extreme Within 15 min hat/umbrella +sunscreen +sunglasses +shade +long sleeved clothing +avoid going outdoors between 10 AM and 2 PM

The Role of UV Rays in Nature

UVI Index

1.Preventative measures for animals

In order to avoid the human UV exposure, you can take the necessary protective measures, while other land-based animals sunscreen does not have the knowledge of mankind, but they can also take refuge in caves or underground, to adapt to the environment or into the surface of the body With the scales, fur and other protective measures to block ultraviolet rays.

2.UV Ray damage to animals

UV rays mostly affect the surface skin cells of animals and cannot penetrate deep to their biological tissue. There is usually no need to worry when cells are exposed to UV rays as they can repair themselves, but over exposure to UV rays can destroy the auto repair functions in DNA cells, cause cells to age, become cancerous, or die. Other chemical substances in the atmosphere such as polycyclic aromatic hydrocarbons (PAH) can cause photochemical reactions with UV rays to cause the phototoxic phenomenon, which when animals are exposed to for extended periods of time can lead to sickness or death. UV rays not only directly affect animals but also causes them indirect harm.

3.Benefit of UV rays for animals

Although UV rays harm animals, but that is not all they do. If an animal is wounded, their wounds can be infected by bacteria but UV rays can kill the bacteria on their wounds to reduce infection; the eyes of some insects have a wider range for detecting light, making UV rays a visible light for them that can help them in finding prey. Humans also use these characteristics in insects to create UV light traps to capture insects.


The Effects of UV rays on plants

1.Effects of UV rays on photosynthesis

Plants require constant photosynthesis to create nutrients when they are growing, and in doing so they are exposed to UV rays. In normal environments plants can get accustomed to exposure to UV rays but if UV rays continue to increase in nature, or if harmful UV rays grow in strength they will affect the biology of plants and obstruct their growth. However, UV rays do not only destroy, as plants will use this type of radiation to change their growth type and biological process. For instance, when the leaves of a plant is exposed to radiation a compound that absorbs UV rays and protects the leaf may appear on its' surface.

2.UV ray damage to plants

The energy from UV rays can affect the DNA structure of plants to cause abnormal combinations which can continue to exist in DNA to cause cells to split and obstruct growth. In terms of UV ray wavelength, shorter waves have a larger effect on the growth of plants.

3.UV ray preventative measures for plants

As plants require exposure to UV rays to perform photosynthesis, in order to grow accustomed to this environment they usually take appropriate methods. In nature, plants change by growing taller or shorter, growing thicker leaves, or reducing the surface area of their leaves to decrease the contact and absorption of UV rays in order to protect themselves.

4.Plant forms under UV rays

When the weather is sunny, one can observe all the changes of plant forms by observing outdoor vegetation. Plants grow taller or shorter, the surface area of leaves can change, leaf curvature can change, and a thicker collection of cells can be found on leaves. Other change such as increased density of pigmentation and changes in chlorophyll dispersion can also occur.

5.Effects of UV rays on agriculture

An increase in UV rays can have adverse effects on the growth of vegetations. Agricultural experts are more concerned with whether an increase in UV rays will lead to a decrease in production. Using Taiwan's main staples such as water crops, current tests indicate that UV rays do not have a significant effect on water crops. What should be noted is that the habitat around fields such as weeds and pests can increase due to UV rays and can indirectly affect the production of agricultural goods.


Effects of UV rays on water life forms

1.Lifestyle of water life forms

70% of the earth's surface is covered by water and life forms under water are much more diverse than those on land. UV rays in the atmosphere can also affect the lifestyle of water life forms, for instance aquatic invertebrates are often more active at night which is why it is theorized that these life forms have poorer self healing abilities against UV ray damage; as for tilapia fish which can heal themselves from UV ray damage, they are active near the surface of water. In contrast, the loach often live under muddy waters to avoid damage from UV rays.

2.Preventative measures for water life forms

Certain water life forms use night activity or hide in shady areas to reduce their exposure to UV rays. Some organisms such as coral, sea anemones, or jellyfish use seaweed or their food sources to gain substances that absorb UV rays to avoid UV ray damage, but some life forms such as worms are highly sensitive to UV rays. If UV rays strengthen slightly, it could lead to a massive amount of death for worms.

3.Increase in UV rays leading to a decrease of life forms underwater

Plankton are categorized as producers in the habitat and is a source of food for fish, shrimp, and other aquatic life forms. The increase of UV rays will lead to a significant drop in plankton which will cause food shortages for fish and shrimp while photosynthesis in seaweed is also obstructed by UV rays. According to studies, 30% of protein eaten by humans are from ocean life such as fish, shrimp, and shellfish. If the decrease of life forms in the sea due to UV rays continues, it will affect a source of nutrients for humans.

The Effect of UV Rays on Material Substances

We often observe plastic products mutating in shape after spending long periods of time exposed to the sun, signifying that the internal structure of the item has changed. According to current studies, UV rays heavily affect outdoor polymers, especially in hot desert regions. The study also discovered that the elasticity of polyethylene is reduced with exposure to UV rays. Scientists conducting studies in this field are still currently ongoing.

UV Ray Monitoring and Forecast

UV Ray Monitoring

1.Principle of UV ray monitoring instruments

In sun radiation, the wavelength of UV rays is under 400nm and divided into three types, including UV-A which freely penetrates the atmosphere and is unaffected by the ozone layer; UV-B, which is absorbed by the ozone, meaning a decrease of the ozone signifies an increase in UV-B; and UV-C which is completely absorbed by the atmosphere and cannot be detected on earth' surface. As the energy of the short wavelength radiation from sunlight that reaches the earth is mostly concentrated in visible light wavelengths, UV ray waves only account for less than 10% of energy. Most of the radiation energy detected on earth are UV-As which begin at 400nm and gradually decrease to UV-B waves, which are 315nm and absorbed by the ozone. The energy level then rapidly decreases to UV-C waves which are 280nm and low in energy level, nearing zero. As the energy in UV rays are small but change drastically, chronic and precise monitoring of the various radiation energy waves in the atmosphere is a difficult task.

Instruments measuring UV rays use two basic methods, one being using a special light spectrum for reactions, which is practical and can be provided for the publics reference. The second method precisely measures actual radiation levels in each light spectrum and is geared towards scientific research uses. The instruments currently produced to measure UV rays can be categorized into three types (scanning spectrometer, non-continuous spectrometer, and broad wavelength instrument) according to their sensors. Taiwan has installed instruments of the first and third types.

2.Scanning spectrometer

The current scanning spectrometers used around the world, the Brewer photoelectron spectrometer for instance uses the UV light absorption qualities of the ozone and observation of UV radiation strength in sun radiation to calculate total volume of ozone in air pillars. A supplementary monitoring device can be added to monitor UV radiation wavelengths between 290nm to 325nm.

This instrument can precisely observe UV waves between 290nm and 325nm. Using software, an observation is taken ever 0.5nm starting from 290nm until 325nm, where it returns to 290nm by repeating observations at 0.5nm intervals. The matter density of radiation from each wavelength is calculated and weighted by the erythema action spectrum to obtain the damaging UV values (DUV). 280Nm~298nm is the UV wavelength that causes skin to become red, so the DUV obtained after passing the radiation through the erythema action spectrum should be lower than the original value of radiation. In DUV values, UVB waves are the most important.

This instrument is extremely precise and uses intervals of 0.5nm to precisely obtain values of each wavelength, but it takes several minutes to make one monitor run. When clouds move swiftly, the observation results become obviously affected. The Brewer photoelectron spectrometer can separately perform monitoring of the total ozone and UV ray value at different times and can automatically calibrate the mercury and standard lamp daily, which is why it is expensive. In addition, operation, adjustments, and maintenance is expensive making this spectrometer unsuitable for mass installation. Currently there are only a little more than 100 units in service around the world, with two currently in Taiwan which routinely exchange data with the ozone and UV ray center in Canada.

3.Broad wavelength UV ray radiation monitoring instrument

Common broad wavelength UV ray radiation monitoring instruments can be used as a response spectrum instrument to measure UV erythema. This type of broad wavelength UV ray instrument has the advantages of being simple to control and inexpensive. Furthermore, its' response time (0.1 second) enables it to operate under any type of weather conditions. However, this instrument is affected by temperature and lower stability. The principle of this instrument uses light waves to pass through a quartz dome and filter to measure the desired UV rays in the sensor, whose temperature is adjusted by the amplifier and output through DC voltage. There is a temperature stabilizer designed into the instrument that enables it to operate with a response deviation of less than 1% at every degree in environments where temperatures range from -40 to -50 Celsius. The response range of the wave spectrum in this instrument is 280nm to 400nm, and is in tune with the reactive curve of erythema, making it a practical tool for taking measurements.

Since 1997, the EPA has completed installation of 5 sets with another 10 sets of this equipment planned in 1998, simultaneously using two sets of monitoring equipment to take readings to ensure the quality of the data.

4.Updated Results of UV Ray Monitoring

The energy levels of UV rays are low and significantly affected with time, making the task of precisely measuring radiation of various wavelengths in the atmosphere over a long period of time a difficult task. Taiwan has not monitored for a long time and cannot display the long term trend of UV radiation, but according to the results from the EPA commissioned monitoring tasks given in Taipei, Alishan, Chengong, and Henchuen, it was discovered that aside from Taipei, during the summer the other stations had high probabilities of reaching levels above 10 (dangerous).

In the autumn 50% of the readings from each station were between levels 5~9 (medium and high) while during the winter, UVI index levels were never more than 10. It is notable that Alishan is the only station that has a rate of more than 50% for UVI index levels to surpass 7 (high). Accumulated radiation at each station showed summer to be the highest, followed by autumn and spring, then winter. Daily accumulated radiation was stronger from May to August. The accumulated radiation of those who worked at noon in the spring, autumn, and winter accounted for 64% to 72% of their daily accumulated radiation, while white collar workers (those who commute from 8~10 in the morning and 16~18 in the afternoon) are at 15%~24%. Those who jog in the morning (6~8 AM) are at 3%~1%. Exposure to radiation of white collar workers and noon workers is approximately the same during the summer, with morning joggers much lower at second. In terms of the entire year, those who work at noon receive approximately 60% of daily accumulated radiation energy, white collar workers receive 20%, while morning joggers show different figures according to geographical location (those in the north are lower, those in the south are higher while those on plains are lower than those on mountains).


UV Forecast

Since the summer of 1994, America's weather bureau and EPA have provided a new experimental product ---- UVI index forecast. Weather reporters announce this figure every day with the usual weather report for the general public, and this index simulates the strongest hour of sunlight during the noon of the next day for the UV ray radiation that reaches the earth's surface.

To get the value of the UV Index (UVI) must first obtain ultraviolet radiation (DUV, Damaging UV values). DUV for the B-band ultraviolet light (280nm ~ 320nm) multiplied by the weighting function (erythema role of the spectrum) and should not, because of the strong ultraviolet UVB for the band, it has been referred to as the result of the dangerous ultraviolet radiation (mW/M2) . DUV be the value of time points and the definition of the cumulative amount per hour 100J/m2 = 1 UVI. For example, the value of the daily noon DUV for 1000 J/m2, while the UVI on the relative value of 10. UVI is an estimate of an hour to facilitate the sun's ultraviolet rays to reach the ground capacity to provide a reference for the index. Environmental Protection Department since July 1998 to take over from the Taiwan region UV Index forecast, made available to the public for information to do in order to take protective measures to reduce the harm caused by ultraviolet light.

1.Calculation of the UV Index forecast

The estimation of UV rays is related to the sun's movement path, atmospheric conditions, and ozone profile. The related elements include the solar zenith angle, day sequence, atmospheric water vapor value, total atmospheric ozone pillar value, suspended micro particles in the atmosphere, cloud cover, and other elements which is why radiation value models are needed to fully consider the elements described above to simulate theoretical radiation values. The EPA's next day forecast of UVI is commissioned to National Taiwan University's global migration center's environmental quality foundation. The forecast process is similar to the American UVI index calculating method detailed above using that day's weather, ozone, and atmospheric profile data and solar zenith angle to simulate that day's UVI.

  1. Calculating the total ozone value of the next day
    The EPA forecast requires that day's total ozone pillar volume which is obtained by the ozone profile data produced by the Central Weather Bureau's Banchiao station. That figure is multiplied by the total ozone volume to ozone ratio and the result is that day's figures for ozone profile density.
  2. Calculating the maximum value of UV radiation at ground level on cloudless days
    The EPA uses radiation models input with weather and ozone profile data with that day's solar zenith angle to calculate the radiation energy that reaches the ground at noon on a cloudless day without micro particles.
  3. Applying weighted functions to solve for DUV at noon
    The EPA multiplies the UV-B radiation strength with the relative weighted function to convert into DUV value
  4. Categorizing the results and adding decimals to solve for UVI at noon
    The EPA's forecast model simulates one DUV strength every 15 minutes, meaning the hourly accumulated radiation value is composed of four radiation values. The categorization follows American methods, dividing values according to size into levels 0 to 15.
  5. Using forecast cloud cover to adjust radiation value of noon
    Using the cloud forecast of sunny, scattered clouds, dense clouds, and overcast and then making adjustments with professionals.

2.UVI forecast process

The EPA's UVI forecast can be divided into the four portions of data transfer, data processing, estimate adjustments and forecast release. The majority of these operations have been automated, with only the final stage closely monitored by forecast personnel to ensure forecast quality. When releasing the UVI forecast, UV ray data, total ozone volume, ozone profile monitoring value, atmospheric profile value, ground weather monitoring and weather forecast information must be obtained for input in the forecast model to obtain the next day forecast. Meteorologist experts then use their professional knowledge to determine how the weather will affect the UVI index before the forecast is released to the public.

3.UV ray monitoring station dispersion

Currently the EPA and the Central Weather Bureau (CWB) set monitoring stations for UVI. Since April 30,2013, integration of both resource to 34 stations.

There are 14 stations run by the EPA, Banqiao, Danshuei, Taoyuan, Miaoli, Shalu, ChangHua, Nantou, Douliu, Puzi, Ciaotou, Pingtung, Alishan and Lulin(Tataka). And 20 stations run by the CWB, Keelung, Taipei, Xinwu, Hsinchu, Taichung, Chiayi, Tainan, Kaohsiung, Hengchung, Yilan, Hualien, Chenkung, Taitung, Lanyu, Penghu, Kinmen, Matsu, Anbu, Sun Moon Lake and Yushan.

4.UVI forecast dispersion

In order to improve service to the public, as of July 1998 the EPA released forecasts for 49 locations.

  1. Northern forecast locations: Keelung City, Taipei City, Taipei County, Taoyuan City, Hsinchu City, Hsinchu County, Miaoli City, Miaoli County
  2. Middle forecast locations: Taichung City, Taichung County, Changhwa City, Changhwa County, Douliu City, Yunlin County, Nantou City, Nantou County
  3. Southern forecast locations: Chiayi City, Chiayi County, Tainan City, Tainan County, Kaoshiung City, Kaoshiung County, Pingtung City, Pingtung County
  4. Eastern forecast locations: Taitung City, Taitung County, Hualian City, Hualian County, Yilan City, Yilan County
  5. Island forecast locations: Matsu, Penghu, Green Island, Lanyu, Little Okinawa
  6. Vacation forecast locations: Yang Ming Mountain, Longdong, Shito, Yushan, Hehuanshan、Lishan, Taroko, Alishan、Sun Moon Lake, Taipingshan、Sanhsientai, Kenting.


How to obtain updated UV index information

1. EPA forecast release schedule

  1. Current Value
    The EPA will post the current hour’s UV index on the website for the public every day.
  2. Forecast Value
    The EPA will post the next day forecast of UV index for all regions on the web site for the public at 5 p.m. every day, that updated with the forecast weather condition at 10:30 a.m. next day.

2.How to obtain UV ray information

  1. EPA web site homepage at http://www.epa.gov.tw
  2. Newspaper, radio broadcast, television, and other media

Are there no UV rays if there is no exposure to sunlight?

UV rays are one of the electromagnetic waves from the sun's radiation, so if there is no exposure to sunlight there should be no exposure to UV rays (not including man-made). As for whether window blinds defend against UV rays, it depends on the strength and penetration rate of UV rays. It also depends on the material and thickness of the window blinds, but generally speaking they should be suitable for blocking UV rays.

last update : 2014/03/12