From Title 21, Volume 8 of the Code of Federal Regulations.

Part 1040 — Performance Standards for Light-emitting Products

Sec. 1040.10 Laser Products

(http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/cfrsearch.cfm?fr=1040.10)

The following information will be used:

• Detailed descriptions of Class Levels
• Definitions (Collateral radiation, human access, integrated radiance, safety interlock, etc.)
• Federal regulations/guidelines for laser use/operation
• Several Cautions

J. Marshall, Br. J. Ophthalmol. 82, 1335 (1998).

• Why the eye is of primary interest in laser safety
  • The three primary damage mechanisms of over(eye)exposure to laser light
  • This is dependent on wavelength, pulse duration, and energy
• The history of laser safety and when codes of practice entered the laser realm
  • This began within 5 years of the first demonstration of a laser, 1960
• Definitions
  • Median Effective Dose (ED)
    • Dose which results in irreversible retinal damage
  • Maximum Permissible Exposure Levels (MPE)
    • Maximum exposure length that results in no damage
• Layman descriptions of laser classes
  • International concerns
    • World Health Organisation (WHO)
    • International Committee for Non-ionising Radiation Protection (ICNRP)
    • International Electro-technical Comission (IEC)
  • The development of laser pointers
    • Beginning with early laser pointers:
      • class 2 systems that used helium-neon laser sources with and emission wavelength at 632.8 nm
• Original intent of lasers for the public
  • For use in lecture theaters or boardrooms
• The visual effect of making eye-contact with laser light
  • In order of increasing brightness:
    • Dazzle
    • “After image” formation
    • Flash blindness
    • Irreversible damage

Dan Vergano. “Powerful laser pointers create risks: Lights deliver strong beams that can damage eyes.” USA TODAY 18 Nov. 2010

This article discusses the dangers of laser pointers sold via the internet. Points made are:

• These laser pointers contain greater strength than what is FDA approved, and the FDA only has jurisdiction over our producers and not our buyers
• Possible retinal damage (they cite the New England Journal of Medicine)
• Dangers of green colored laser pointers
• * this article is somewhat dramatized and contributes as a supporting element to the article by John Marshall

W. M. Steen and J. Mazumder, Laser Material Processing, 4th ed. (Springer, London, 2010).

• Chapter 13 of main interest
• Page 519 outlines main danger of lasers- damage to the eye, damage to the skin, electrical hazards, and fume hazards
• Danger to eye
  • Damage to retina in back of eye and damage to cornea in front
  • Radiation on retina focused by eye’s lens to amplify power by about 10^5 (100,000)
    • Laser at the visible or near-visible waveband are much more dangerous compared to outside the band
  • Eye damaged through explosive evaporation (cooking and boiling)
  • Safe exposure limit indicated by maximum permissible exposure (MPE) levels
    • Levels very low, especially as lasers become more powerful
• Danger to skin
  • Laser classes 3R, 3B, and 4 are dangerous to the skin, with 3R least dangerous and 4 most dangerous
  • Safety arrangements
    • 1) Beam terminated with material able to withstand beam for several minutes
    • 2) Stray reflections minimized
    • 3) All personnel must wear goggles
    • 4) Must seek approval for entry
    • 5) Warning lights and hazard notices
    • 6) Care taken in beam alignment
    • 7) Laser safety officer to check on guidelines
• Electrical danger
  • “A typical CO2 laser may have a power supply capable of firing the tubes with 30,000V with 400mA” (W. M. Steen and J. Mazumder 2010:525)
    • Fatal discharge possible at this level
  • Earthing system must be present
• Fume danger
  • High temperature of laser able to volatilise most materials, creating potentially dangerous fume
  • Organic materials particularly dangerous; laser might create radical groups highly dangerous to people

A. L. McKenzie, J. Radiol. Prot. 8, 209 (1988)

• “It would seem that no organ of the body is immune from incision, resection, coagulation or ablation by laser” (McKenzie 1988:209)
• Laser types and characteristics
  • Carbon dioxide laser
    • 20-100 W of far-infrared (wavelength of 10.6 μm)
    • Usually continuous, sometimes pulsed between several hundred and several thousand hertz
      • Radiation at this level easily absorbed in water- explosive disruption of cells as water becomes steam (tissue ablation by vaporisation)
    • Heat damage under the ablated surface is minimal
    • Because of tissue coagulation between 60-80 degrees Celsius, tissue is denatured and blood vessels are constricted; bloodless operation
      • Used in gynaecology procedures, especially treatment of cervical intra-epithelial neoplasia
  • Argon lasers
    • 3-6 W of blue-green light (usually several wavelengths at one time, usually 488 nm and 514.5 nm most common)
    • Highly scattered, diffuses a few hundred microns below tissue; good for surface use such as coagulation
  • Nd:YAG lasers
    • Neodymium-doped yttrium aluminium garnet
      • Nd:Y3Al5O12
    • Near-infrared radiation (wavelength of 1.06 μm)
      • Either continuous at 60-100 W or pulses at tens of nanoseconds at several mJ per pulse.
        • When pulsed, known as Q switched lasers as opposed to continously working (cw) mode
    • Beam scatters less than argon laser light, and absorbed less than carbon dioxide laser radiation
      • Can coagulate more volume (several mm of soft tissue) than both argon and carbon dioxide lasers
  • Other lasers
    • Krypton laser
      • 647 nm or 568 nm; can be tuned to any wavelength in visible spectrum
• Eye hazard
  • Sight impairment through retina, cornea, and/or lens damage
  • Cataract induced by absorption of near-infrared or ultraviolet radiation
    • Thermal damage present long before cataract, however
  • Cornea affected by heat like egg white- will “cook” the cornea and create opaque patch where laser impacts
  • Visible and near-infrared radiation at 1.06 μm can travel through ocular media to retina
    • ~ 40% of Nd:YAG laser radiation hits retina; ¾ will be transmitted or reflected (only ~10% absorbed in retina)
  • MPE
    • Carbon dioxide- 560 t^-0.75 mW cm^-2
    • Argon- 9 t^-0.25 mW cm^-2
    • Nd:YAG- 1.8 t^-0.25 mW cm^-2
    • Eye blink reflex time is usually cited as 0.25s
• Eye protection
  • Different types of eye protection are needed for different types of lasers in medicine
• Other hazards
  • Skin burns
    • Maximum permissible exposure tables are also calculated for skin contact, like for eye contact
    • Laser-proof protection is impractical to wear, however
      • Safety controlled by prevention of skin contact instead
  • Smoke
    • “Smoke is produced when cell water has been removed from soft tissue, leaving the dried framework to char and burn” (McKenzie 1988:217)
  • Fire
    • Cited by Fisher as a greater hazard than eye injury (McKenzie 1988:217)
• Laser theatre
  • Windows need to be shielded according to power of laser
• Laser Protection Adviser and Laser Protection Supervisor (LPA and LPS)
  • LPA in control of installation, training, and usage
  • LPS a subordinate of LPA; in charge of supervision and observation of the rules

We are going to work with cell phones, microwaves, laptop computers, and mp3 players, along with other possible technological devices. Different misconceptions about each item will be researched/tested for validity. Data collection for some experiments can be taken with the megawatt pro. We will also be using the video camcorder to record a short, creative film capturing our findings from these debunked myths. All group members will play as actors in the film and will also work closely on the script; all members will also be involved in researching to prove/disprove the myths. Michael will record. We expect a majority of Vassar students to be aware of the falsity of these common misconceptions. Dates for meetings TBA.

Some possible myths to be tested:

• Cell phones- cause brain cancer; interfere with medical equipment in hospitals
• Microwaves- give off unsafe levels of radiation
• Laptop computer- turning off computer vs. keeping it asleep; keeping charger plugged in runs down battery; is it best to run down a battery before charging
• Mp3 Players- linked to cancer

Project Plan

Purpose:

Can the average consumer perceive the difference between high fidelity analog recording and compressed digital formats?

Hypothesis:

If we present a subject with a blind sample of the same audio recording on two different formats then it is assumed that they will be able to notice a difference and prefer the higher fidelity audio recording. The reason being that there is not the distortion caused by clipping when an analog source is converted to digital.

Materials:

-High-fidelity recording headphones

-Computer

-Quality analog recording (format: long playing record)

-Associated record player

-blindfold

-coin (for randomization)

Procedure:

-Acquire a sample pool of subjects, have a mix of age and gender.

-Induce the subject to be blindfolded

-flip the coin to decide if the MP3 format or the record will be played first.

-play the recordings back to back to the subject.

-Ask the subject which format A or B he/she preferred

-Ask the subject to guess which of the two recording was on the higher quality

-Repeat this process for all members of your subject pool.

-Compare the data

– Our group will be explaining the physics behind mag stripes using Faraday’s Law and the principles of induced magnetic fields, induced current, and induced Electromotive Force. We will attempt to explain the complex mechanisms in a fairly simple way.

– In the experimental part of our project, we will be swiping vcards at varying velocities using different types of data storage (swiping for building access and swiping for food). We will record the minimum and maximum swipe velocities that are accepted by the card readers. Because we won’t be able to determine the various speeds by eye, we will have to use Logger Pro to do that.

-We will also explore the difference between magstripes on different types of cards (subway cards, credit cards, vcards etc.) and how different data is stored on the magnetic stripe. We will attempt to contact the card office on campus to see the process in which our ID cards are created

-There aren’t necessarily certain outcomes because our project is mostly theoretical, and it’s just explaining a mechanism that’s already known extensively. We do not have any expectations for what swiping speeds will be accepted by the card readers on campus.

• Tim will be doing the theoretical aspect of the project. He will be explaining the physics behind the mechanisms in magstripes and magnetic data storage.
• Dan will be recording video and plotting data tables on LoggerPro and assisting with investigating the physics.

• Alex will be doing the experimental aspect of the project – he will be going around campus swiping student ID cards at varying speeds.

Technology used:  vcards, camera, loggerpro

Meeting times: MWF 5-6pm, location (TBA) –

Kento: Will gather and research published data on radiation levels
Andrew: Will gather information about standardized levels of normal radiation that are deemed safe, dangerous, or lethal and compare it to the published known radiation level data sets
David: Will conduct an experiment to see how radiation levels are measured and explain the functions behind it.

Science and Technology Involved: We will be taking a close look at the process of creating nuclear power, which involves 1) controlled (non-explosive) nuclear reactions. When producing nuclear energy, nuclear fission reactions heat water and produce steam, creating electricity. As the nuclear plant explosion in Fukushima has shown, there are times when this process of creating energy can be harmful to humans and the environment. We want to study the radiation levels that are associated when there is a failure of the cooling systems, resulting in a nuclear emergency.

Activity Plan: Our data will consist of radiation reports by Tepco, The Tokyo Electric Power Company, who publishes and monitors radiation levels from its failing power stations. We will also seek to report radiation levels that exist in surrounding areas, including the land and water, in an effort to learn more about the relative exposure levels and its effects. We also plan to conduct an experiment using the lab at Vassar College to better understand how radiation measurement works.

Data on daily radiation exposure levels at Fukushima Power Plant:

http://www.tepco.co.jp/en/nu/monitoring/index-e.html

Our meeting times will be on Monday at 1:00 p.m. and Wednesdays at 3:00 p.m.

Outcomes: We assume that due to the concentration to radiation levels in close proximity to the plant, exposure levels will be most significant there and expand as radiation continues to leak. We want to compare these radiation levels in Fukushima with what is deemed as safe/dangerous/lethal and make predictions about the effects on the people situated in and around the power plant now.

Roles:

Robin– Robin will be the actor in the film, and will also write the theme song for the presentation. The theme song will be a light-hearted take discussing lasers and laser science. Bianca– Bianca will be the cinematographer and the editor of the film.  We will co-write the script, and also both conduct the necessary research.

Science/Technology:

Lasers will, unsurprisingly, play a main role as the technology within our film. The science behind how lasers can cause injury to body parts and why one should not play around with lasers will also be covered. Video editing software will be used for Bianca’s role in the project, and music editing software will be used for my portion of the project.

Activity Plan:

We will first write the script together, with filming occurring after we finish the script. The theme song’s lyrics will be written after the script is complete, but while the movie is being filmed and edited; the musical part will be constructed beforehand.  The finished product will be a refined, produced short film highlighting why one shouldn’t play around lasers (along with why messing around with anything potentially dangerous is a bad, bad idea).

Outcome:

We hope that this project will be highly educational and teach the class about lasers and laser safety, while also being entertaining, interesting, and hopefully funny. Hopefully.