Evaluating the UV Index in Order to Determine Its

Relationship to Exposure Level and Health

NM HS Supercomputing Challenge 2001 NMT Summer Teacher Institute

Team Members: D.B. Gupta

Debbie Loftin

Dwight Thopmson

Beckey Raulie

Problem DefinitionProblem Definition

Although most people know the elevation of the city in Although most people know the elevation of the city in which they are living and they take notice of cloud cover which they are living and they take notice of cloud cover at different times of the day, they do not commonly equate at different times of the day, they do not commonly equate this information with a need to alter their behaviors in this information with a need to alter their behaviors in relation to the incoming solar radiation.relation to the incoming solar radiation.

Therefore, we chose to create a simple program Therefore, we chose to create a simple program

that would take this common knowledge and that would take this common knowledge and allow it to be input into a program that would give allow it to be input into a program that would give an accurate estimate of the incidence of UVR at an accurate estimate of the incidence of UVR at the surface for their current location.the surface for their current location.

IntroductionIntroduction

The Stratosphere Mechanics of Depletion Sunspot Cycle History Lack Of Action Action The Skin and UV Rates of Skin Cancer Types of Research Effects of the Sun Cancer Types

Exposure Level Scale Precautionary Measures Understanding SPF Tanning Determining UV Index Variables and

Assumptions Our Mathematical Model Results of Our Program Validating Our Model The Gene

The Stratosphere

How Is Ozone Depleted?

The main carriers of chlorine are products of the breakdown of CFC’s– HCl and ClONO2

These eventually percolate up into the stratosp;here where they are broken apart by solar radiation (energy)– the free chlorine atoms interrupt the natural ozone

formation by breaking apart O3

What is the Role of The Sunspot Cycle?

Every 11 years the sun begins a cycle moving from low to high solar activity (flares, sunspots etc.)

This solar flux significantly changes the ozone concentrations in the stratosphere– cannot be discounted for

minor global ozone variations over the past 2 decades

History of Ozone DepletionHistory of Ozone Depletion ~1957 - Canada begins recording surface UVR~1957 - Canada begins recording surface UVR 1970 - U.S. Congress cancels SST program*1970 - U.S. Congress cancels SST program* 1974 - Researchers at UC Irvine project CFC’s serious potential1974 - Researchers at UC Irvine project CFC’s serious potential 1978 - Nimbus 7 satellite 1978 - Nimbus 7 satellite Early 80’s - Agreement in theory that ozone depletion would affect Early 80’s - Agreement in theory that ozone depletion would affect

biological cycles disagreement to size of the effect biological cycles disagreement to size of the effect March 1985-Vienna Convention signed by international communityMarch 1985-Vienna Convention signed by international community late 1985 - “Hole” in ozone discovered over Antarcticlate 1985 - “Hole” in ozone discovered over Antarctic Sept 1987 - Montreal Protocol on Substances that Deplete the Ozone Sept 1987 - Montreal Protocol on Substances that Deplete the Ozone

Layer Layer 1990 & 1992- Increased level of emission reduction & reduced 1990 & 1992- Increased level of emission reduction & reduced

timelinetimeline as of 1999 -Canadian Researchers report that average thickness of as of 1999 -Canadian Researchers report that average thickness of

the ozone layer has declined by ~7% since 1980 the ozone layer has declined by ~7% since 1980

Reasons for Lack of Action

Industrial scientists Manufacturers Historical Data Industry officials 1992 Belgian Meteorologist Models used to predict future ozone depletion Lack of data for African continent

Reasons For Action

Media played on conscience of consumers

Individual convenience contrasted with health of the planet

Belief that actions taken in the present would affect the health of future generations

1970’s sales of aerosol products dropped to pre-1968 levels– Public support of precautionary principle “err on the side of caution

to prevent potential environmental destruction”

Despite problems with instruments and predictive models increasingly sophisticated & accurate measurements of ozone show a downward trend in daily readings

The Skin and UV UVA recently implicated in cutaneous melanoma Link between UVB and Non-Melanoma Skin Cancer

– based on Canadian short term data strong inverse relationship

Detection of long-term changes in UV trends remain difficult

– Austria & Switzerland show 7% increase in UVB from 1981-1991 but surface measures in U.S. show a decrease of 8% from 1974-1985

• a European station showed a decrease in UVR when ozone levels were decreased

– depends on latitude, cloud cover, surface albedo, tropospheric aerosols, & other pollutants as well as ground level ozone

Rates of Skin Cancer•Over the past 40 years the incidence of NMSC & MM have been rising Over the past 40 years the incidence of NMSC & MM have been rising substantially mainly in white populationssubstantially mainly in white populations

• Currently mortality may be leveling off likely due to changes in lifestyle & Currently mortality may be leveling off likely due to changes in lifestyle & behavioral practicesbehavioral practices

•Western developed countries show greatest increase due to the substantial Western developed countries show greatest increase due to the substantial high risk populationhigh risk population

•AustraliaAustralia

•melanoma in men increased 6.3% annually, but only 2.9% in women melanoma in men increased 6.3% annually, but only 2.9% in women between 1959 & 1985between 1959 & 1985

•this has plateaued at the highest levels in the worldthis has plateaued at the highest levels in the world

•Canada Canada

•incidence for women decreased -1.0% & has increased for men to 1.5% incidence for women decreased -1.0% & has increased for men to 1.5% from 1985-1992from 1985-1992

•A 1% decrease in stratospheric ozone results in a 20% increase in NMSCA 1% decrease in stratospheric ozone results in a 20% increase in NMSC

Types of Design in Epidemiological Research Descriptive Studies

– case studies & cross sectional surveys cannont control intervening variables

Analytic Studies– can show direct causal relationship

• randomized control trials

– Norway no change in ozone • Skin Cancer increases with decreasing latitude

– NY 1979-1982• subgroups without ability top tan & higher moles =higher risk.

• Health policy makers have defined skin cancer as a preventable disease under the control of the individual

Effects of the Sun

Sunburn Tanning Premature Wrinkling Skin Cancer Eye Damage Allergies Immune System Suppression and Disease

Skin Cancer Types

B asa l C e ll S q u am ou s C e ll M e lan om a

S k in C an cers

UV Exposure Level

INDEX NUMBER EXPOSURE LEVEL

0 - 2 MINIMAL

3 - 4 LOW

5 - 6 MODERATE

7 - 9 HIGH

10+ VERY HIGH

Precautionary Measures

UV INDEX

Burningtimewithoutprotection

SENSITIVE SKIN / CHILDREN Sun ProtectionFactor

10+Extreme

LESSthan15minutes

Do not expose yourself. Wear clothing, a broad-brimmedhat, sunglasses, and frequently apply sunblock cream withsun protection factor 40.

SPF 40every half hour

7 - 9Very high

20minutes

Do not expose children. Favor staying in the shade. Weara hat, sunglasses, a shirt, and apply sunblock cream withsun protection factor 40.

SPF 40every hour

5 – 6High

25minutes

Do not expose young children. Wear a hat, sunglasses, ashirt, and apply sunblock cream with sun protectionfactor 25.

SPF 25every hour

3 - 4Medium

40minutes

Wear a hat, sunglasses, and apply sunblock cream withsun protection factor 15.

SPF 15every hour

1 - 2Low

60minutes

Wear sunglasses and apply sunblock cream with sunprotection factor 8.

SPF 8every hour

SPF stands for Sun Protection Factor

Example: If you Burn in 10 minutes

SPF 8 8 x 10 = 80 minutes

SPF 15 15 x 10 = 150 minutes

Sunscreeen should be applied 15-30 minutes Before exposure and

reapplied after swimming. Waterproof generally means 80 minutes of ‘water resistant’ protection

WARNING! Sunblock and sunscreen products

are NOT meant to allow a longer

exposure time, but to limit the risks

of solar exposure.

Better ?

Which

is

“You have to expose yourself to UV for a short period of time to activate the melanocytes. They produce melanin over the course of hours. By repeating this process over 5 to 7 days pigment builds up in your cells to a level that is protective.” Marshall Brain

How UV Index is Determined

Latitude, Altitude, Time of day (hourly solar

zenith angle.

Time of Year (seasonal/vertical ozone profiles)

Orbital Eccentricity Ozone Conditions Daily Ozone Values Cloud Cover (hourly, ceiling height, visibility condition)

Variables and Assumptions Dose values calculated at the top of each hour

– local conditions vary on a shorter time scale & solar zenith angle constantly changing

Average incoming UVR takes into account– Ozone absorption seasonally averaged number density profiles at

increments of 1km in stratosphere and 0.5km in the troposphere were accurately interpolated to give typical surface-level mixing

– TOMS accurately normalized the number density profiles to the total Dobson unit values measured over the region to give seasonal profiles

– assumption that aerosol particles (whether natural or anthropogenic) are spherical

– SAMSON hourly station observations for 237 locations in the U.S. from 1961-90 correctly infer the type of cloud present,

– normalized action spectrum is accurately used

– a direct comparison of received dose amts.

– erythemal dose

Our Mathematical Model

UV INDEX =(290*(1+0.06*D)*E)– UVR range affected by ozone 100 to 315 nm

(weighted)

D = Elevation from sea level in Kilometers– UVR increases ~6%/km

E =EXPOSURE LEVEL (cloud cover) – 1 = Clear Skies (100% of UVR)

– 2 = Scattered Clouds (89% of UVR)

– 3 = Broken Clouds (73% of UVR)

– 4 = Overcast (31% of UVR)

Validating Our Model

We validated our model by using the example wavelengths given at the EPA site on How to Calculate the UV Index

Our program gave the same results each time

Results

Bases on 290 nm overcast skies give the most protection form UV

Incoming UVR only minimally affected by increased elevation

The Gene

“Sunlight and Skin Cancer” ScientificAmerican 1996, D.J. Leffell & D.E. Brash– This study suggest that early cellular damage to

the skin through sun damage (most often assunburns in childhood) can provide a pathwayfor later development of skin cancer

• This permanent damage can mutate the p-53 gene ina skin cell so that upon additional exposure to UVRthe skin cells surrounding the damaged gene die offand provide the opportunity for the mutated skincells to grow and multiply

Conclusion

There are many technical factors that mustbe considered when considering how the UVIndex is calculated– Scientific data are not extensive enough to be

conclusive, but evidence thus far indicates thatcaution is prudent when exposing yourself to thesun

More time is needed to collect data that canvalidate the effects of ozone depletion andits possible relationship to skin cancer

The Future

Listen to the UV Index reports.

– Take precautions to avoid overexposure to the sun'sultraviolet rays.

– Take special care with children.

– The simple actions listed above can reduce your risks ofdeveloping UV- related skin cancers and cataracts.

To improve the accuracy of the UV Index calculation

– We would like to have our Java program linked directly to theToms satellite so that the daily global image of daily erythemal UVexposure could be taken into account along with the other variables

• this would make our calculation more accurate in determining the riskof being in the sun at different locations

References

http://www.nws.noaa.gov/pa/secnews/uv/ http://www.epa.gov/ozone/uvindex http://howstuffworks.lycos.com http://www.mscsmc.ec.gc.ca/uvindex http://www.rollanet.org/~shady/sunlinks.html http://www.methodisthealth.com/Skin/ultravio.htm

Acknowledgements

Gina Fisk - our sponsoring teacher for helping us to debug our program

Eric Ovaska - for making us feel like we were doing a worthwhile project and the help with Java

Mike Davis - for teaching me how to use gnuplot Mike Topliff - for allocating more hard drive space

for our Powerpoint file. All of consult for this opportunity to learn all that we

did in order to complete this project