good ozone and bad ozone

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Good Ozone and Bad Ozone. MEES, March 5, 2008 Mort Sternheim, Rob Snyder, STEM Education Institute Center for Hierarchical Manufacturing University of Massachusetts Amherst. MEES, March 5, 2008 Mort Sternheim, - PowerPoint PPT Presentation


  • Our sponsorsNational Science Foundation grant to the UMass Center for Hierarchical Manufacturing, award # 0531171

    NASA grant to the STEM Education Institute (ended), award # NNG05GN64G

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  • Todays agendaOzone and ultraviolet (UV) lightNanoparticles and sunscreenHands on sunscreen activityOzone is a health problemMeasuring ozone handouts

    Todays materials on

  • The big ideasUltraviolet light causes skin damage and cancerOzone in the stratosphere blocks UV, partly Sunscreen blocks UV, partlyNanoparticles in sunscreen improve blockingTropospheric ozone is a major part of smog, damages plants, animals, and people

  • 1. Ozone and UVOrdinary oxygen gas: O2 (2 oxygen atoms)Ozone: O3 (3 oxygen atoms)Polar molecule, like waterOzone is much more reactive, unstablePale blue, poisonous gas Bad!Absorbs ultraviolet radiation! Good!

  • The Suns radiation spectrum~ 43% is in the visible range~ 49% is in the near infrared range~ 7% is in the ultraviolet range< 1% is x-rays, gamma rays, radio waves. Most of the suns radiation is Ultraviolet (UV), Visible & Infrared (IR) : Source: Adapted from

  • Some types of electromagnetic radiationThe sun emits several kinds of electromagnetic radiation: Visible (Vis), Infrared (IR) and Ultra Violet (UV). Note the split into UVA, UVB, UVC

    Each kind is distinguished by a characteristic wavelength, frequency and energyHigher energy radiation can damage our skinSource: Energy Low Energy

  • What is Radiation?Light radiation is often thought of as a wave with a wavelength (l), speed (c), and frequency (f) related by

    Source: c (the speed of light) is constant, the wavelength and frequency are inversely related

    This means that light with a short wavelength will have a high frequency and visa versa.

  • Radiation energy comes in packets or photonsThe size of an energy packet or photon (E) is determined by the frequency of the radiation (f)

    Radiation with a higher frequency has more energy in each packet The amount of energy in a packet determines how it interacts with our skin

  • Skin DamageVery high energy radiation (UVC) is currently blocked by the ozone layer High energy radiation (UVB) does the most immediate damage (sunburns)But lower energy radiation (UVA) can penetrate deeper into the skin, leading to long term damage

    Source: N.A. Shaath. The Chemistry of Sunscreens. In: Lowe NJ, Shaath NA, Pathak MA, editors. Sunscreens, development, evaluation, and regulatory aspects. New York: Marcel Dekker; 1997. p. 263-283.

  • Good ozoneIn the stratosphere, absorbs 97+ % of solar UV, protecting life from harm Produced by solar UV light from O2 :O2 + UV (radiation < 240 nm) 2 O O + O2 O3 Ozone oxygen cycle: O3 + UV (< 320 nm) O2 + OThis cycle heats the atmosphere slightly, so ozone is a greenhouse gas

  • *Ozone (parts per million)020406080100Altitude (km)TroposphereMesosphereThermosphereOzone In the AtmosphereAltitude (miles)100203040506090% of ozone is in the stratosphere0246810% of ozone is in the troposphere

  • *UVc - 100% AbsorptionUVb - 90% AbsorptionUVa - 50% Absorption & ScatteringOzone is the Earths natural sunscreenOzone (parts per million)020406080100Altitude (km)TroposphereMesosphereThermosphereAltitude (miles)100203040506002468

  • Ozone layerOzone in stratosphere, 10 to 50 km above surfaceOzone Can be depleted by free radical catalysts NO, OH, Cl, Br from natural sourcesAlso from chlorofluorocarbons (CFCs) (freons) and bromofluorocarbons (halons)UV light produces free Cl, Br radicalsCl, Br catalyze chain reactions destroying ~100,000 ozone moleculesUsed in aerosols, refrigerators, air conditioners, fire extinguishers

  • Chemicals that Destroy Stratospheric OzoneCl is much more abundant than BrBr is about 50 times more effective at O3 destructionFrom Ozone FAQ - see Ozone FAQ - see

  • Ozone depletionOzone levels decreasing ~4% per year since 70sMore skin cancer?Larger seasonal decrease in lower altitudes (troposphere) in polar regions: the ozone holeCFCs phased out globally by 1996 (Montreal Protocol, 1987) will take decades to leave atmosphereOzone levels have stabilizedRecovery will take decades

  • Low level (tropospheric) ozoneFormed by interaction of UV with hydrocarbons, nitrogen oxides from natural sources plus car exhausts, etc.Major air pollution (smog) componentCan cause serious damage to lungsFatal in very high concentrations for people, animalsDamage to plantsUNH Forest Watch looks at white pine needles which store data for 3 school projectMeasure with ozone sensitive paper, new meters

  • Ozone levels3 10 ppb: Threshold of perception. Typical indoor level when outdoor levels are low50 ppb: Maximum allowed indoor levels100 ppb: Maximum allowed in industrial work area150 - 500 ppb: Typical outdoor peak urban levels300 ppb: Threshold for nasal, throat irritation500 ppb: Smog alert #1 in Los Angeles. Can cause nausea, headaches; lead to lung edema.

  • Higher ozone levels1000 1500 ppb: Smog alerts #2, 3 in LA. Headaches, chest pains after 2 hours12,000 ppb: Lethal for guinea pigs after 3 hrs50,000 ppb: Lethal for humans after 60 minutes

  • 2. Nanoparticles and sunscreen

    1 nanometer = 10-9 meter ~ 10 atomic diameters Nanoparticles: 1 to 100 nm in diameter, or about 10 to 1000 atomic diametersSunscreen PowerPoint and activities based on NanoSense web site

  • Nano ProductsNumber of products using nanomaterials is growing very rapidlyDoubling every year?Clothing, food and beverages, sporting goods, coatings, cosmetics, personal careSunscreens: many use nanomaterialsSome labeled as containing nanoparticlesSome not labeled


  • Why Use Sunscreen?Too much unprotected sun exposure leads to:

    Premature skin aging (e.g. wrinkles)


    Skin cancer


  • Skin Cancer Rates are Rising FastSkin cancer:Is ~50% of all cancer casesHas > 1 million cases diagnosed each yearCauses 1 person to die every hour Probability of getting skin cancer:1930 : 1 in 5,0002004 : 1 in 652050 : 1 in 10; of the increase:Decrease ozone protectionIncreased time in the sunIncreased use of tanning beds

    Sources: ;

  • Sun Radiation SummaryIncreasing EnergyIncreasing Wavelength

  • Which Sunscreen Should You Use???New and ImprovedNow with Nano-ZSPF 50Goes on ClearSafe for ChildrenBroadband Protection

  • A Brief History of Sunscreens: The BeginningFirst developed for soldiers in WWII (1940s) to block sunburn causing rays


    Shorter wavelengths (more energy) called UVCLonger wavelengths (less energy) called UVA

    These were called UVB raysWWII soldier in the sun

  • A Brief History of Sunscreens: The SPF RatingSources: and

    SPF (Sunscreen Protection Factor) NumberMeasures the strength of UVB protection onlyHigher SPF # = more protection from UVB Doesnt tell you anything about protection from UVASunscreens first developed to prevent sunburnIngredients were good UVB blockers

  • A Brief History of Sunscreens: The UVA ProblemUVA rays have no immediate visible effects but cause serious long term damage CancerSkin agingSunscreen makers working to find UVA blockersNo official rating of UVA protection yet

    Source: different skin cancer lesions

  • How do you know if your sunscreen is a good UVA blocker?

  • Know Your Sunscreen:Look at the IngredientsLotion has inactive ingredientsDont block UV lightUV blocking agents are active ingredientsUsually have more than one kind presentSource: Original ImageUV blocking agents suspended in a lotionColloidal suspension

    Two kinds of active ingredientsOrganic ingredients and inorganic ingredients

  • Organic Ingredients: The BasicsOrganic = Carbon AtomsHydrogen, oxygen & nitrogen atoms are also often involvedStructureCovalent bondsExist as individual moleculesSize Molecular formula determines sizeTypical a few to several dozen (
  • Organic Ingredients: UV AbsorptionElectrons capture the energy from UV raysThey jump to higher energy levelsThe energy is released as infrared rays which are harmless (each ray is low in energy)

    Source: Adapted from eV3hf=2.48 eV

  • Organic Ingredients: Absorption RangeOrganic molecules only absorb UV rays whose energy matches difference between electron energy levels Different kinds of molecules have different peaks and ranges of absorptionUsing more than one kind of ingredient (molecule) gives broader protection

    One Ingredient Two Ing