Airport Insecurity

airplane
Courtesy of Yuna via Creative Commons

As you know, there was an aborted attempt to bomb Northwest Airlines Flight 253 last Christmas. The explosive (a.k.a., “crotch bomb”) was hidden in Mr. Abdulmutallab’s underwear to avoid detection. In the wake of this attempted terrorist attack, there was a lot of press on using full-body scanners at airport security checkpoints because such a scanner would have revealed the bomb. The news coverage focused primarily on the issue of privacy invasion weighed against the benefit of increased airport security.

Usually the news coverage included a frequent flier pleading for us to spend the money on full-body scanners to improve safety. However, I saw very little coverage on the potential health effect of frequent full-body scans. Now as a research scientist, I know just how much paperwork is required to scan humans even for medical purposes. So I know that these airport security scanners must pose very little health risk to humans. However, all the hype did get me curious about the technology used. There are two different technologies used for airport security full-body scanners — millimeter wave technology and backscatter technology.

Millimeter wave technology uses low-level electromagnetic waves. The millimeter wave is transmitted from two antennas simultaneously as they rotate around the body at high speed. A person walks into a large portal that resembles a glass elevator, pauses, and lifts his arms while being scanned for about 2 seconds. The wave energy reflected back from the body is then used to construct a 3-D image, which resembles a fuzzy photo negative that is displayed on a monitor in a nearby room. According to the Transportation Security Administration, the energy projected by a millimeter wave system is thousands of times less intense than a cell phone transmission.

Backscatter technology projects a very weak ionizing X-ray beam over the body surface. A person stands against a refrigerator-sized backscatter machine as a narrow, low-intensity X-ray beam scans his entire body at high speed. The beam of X-rays is sequentially scanned at a very high rate in the horizontal direction across the person’s body, while simultaneously moving down at a lower rate of speed. The entire scan takes a few seconds. The reflection ( “backscatter”) of the beam is detected, digitized and displayed on a monitor in a nearby room. The images look like a chalk drawing.

Many reports have erroneously stated that the X-rays from this backscatter technology penetrate clothing but not skin. In fact, the X-rays penetrate the skin but not much beyond it. However, the dose from the X-ray beam is truly negligible by any standard. It is equal to the dose that you receive from 15 minutes of natural background radiation (such as the sun’s rays). The dose from each scan is less than 10 microrem, which is equivalent to the dose you receive from two minutes of flying in an airplane at 30,000 feet. Or put in another way, the dose from the backscatter scan is less than 0.2% of the radiation received from a medical chest X-ray. Doctors and radiation experts argue that such a dose is inconsequential even for pregnant women.

The American College of Radiology states, “An airline passenger flying cross-country is exposed to more radiation from the flight than from screening by one of these devices.”  However, these scans do have some limitations in terms of security effectiveness. For instance, these backscatter scanners cannot find weapons hidden in body cavities since the X-rays don’t penetrate much beyond the skin. Presumably the terrorists will adapt to account for the technology.

U.S. Fuel Usage

When thinking about energy alternatives to fossil fuels, we need to keep in mind how the United States uses its current fuel supplies. Based on a report by the Lawrence Livermore National Laboratory,

28% is used for transportation (gasoline and jet fuel)

40% is used to generate electric power

20% is used for direct heating (natural gas, coal)

32% is used by industry.

(Someone of you will immediately notice that this list adds up to more than 100% — that is because of overlap. For instance, some of the electric power is used by industry.)

The reported numbers vary, but the bottom line is that we use fuel for transportation, electricity, heat and industry in comparable amounts. We need to keep this in mind when discussing energy policies. If we miraculously replace all gasoline with biofuels (alcohol made from plants), we will affect only 28% of the total. So we need to address several “sectors” or uses if we want to significantly reduce fossil fuel emissions.

Health News Blog

For those interested in health news blogs, I highly recommend “Health News from NHS.” This science blog looks at the science behind the international news headlines. The unique thing about this blog is its format:

  • Summary of news reports
  • Where did the story come from?
  • What kind of research was this?
  • What did the research involve?
  • What were the basic results?
  • How did the researchers interpret the results?
  • Conclusion
  • Links to Headlines
  • Links to Science

Given the long list above, you’ll justifiably conclude that the blog is a little bit longer than the average science news blog. However, you’ll come away with a more thorough understanding of the topic as a result. It may appeal particularly to scientists, but it could appeal to everyone on topics of specific interest.

The Future of Freelancing: Redefining Journalism. Reinventing Yourself.

Freelance writers and editors in the SF Bay Area may want to check out an upcoming 2-day seminar, co-sponsored by Stanford and the American Society of Journalists and Authors. It will cover a range of topics relevant to freelancing in a changing world, including social media, digital media, the future of investigative reporting, grants, fellowships, publishing books, and pitching magazines. Check it out on their website.

Jet Lag? Sleepless Nights?

woman laying on bed awake
Courtesy of Wiros via Creative Commons

A while back I used melatonin supplements in order to help with jet lag, since I was traveling for work to Germany. A friend that travels a lot had recommend melatonin to me, and it did seem to help me re-establish a normal sleep cycle when dealing with a large time shift.

Occasionally I have trouble sleeping through the night at home also. I usually fall asleep right away, but I wake up in the middle of the night and sometimes have trouble falling back to sleep. I have allergies and regularly take antihistamines, so the popular over-the-counter sleep aids like Tylenol PM (which has the same active ingredient as Benadryl as the sleep aid) don’t really work for me. So I wondered if I should take melatonin instead. Although melatonin is an herbal supplement, I did a little research to determine if I think it is safe to take as a normal sleep aid. This is what I found.

Melatonin is a hormone naturally produced by your pineal gland, which is a small pea-sized structure located deep inside your brain between the two hemispheres. Melatonin regulates your circadian rhythm, or basically your 24-hour internal clock. When the sun sets and darkness falls, you begin to naturally secrete increased levels of melatonin.  As the melatonin levels rise in your blood, you start to feel sleepier. This hormone level is highest in your blood around bedtime and stays elevated for about 12 hours, then it falls back to the low daytime level around 9 am. Although nighttime melatonin levels remain at least an order of magnitude higher than at daytime throughout your life span, the concentration of melatonin continually decreases as you age. This helps explain why many older adults have problems with frequent insomnia.

Melatonin supplements have been shown to help “reset” the body’s internal clock in those suffering from jet lag, shift workers who work nights and sleep during the day, and blind people. There have been many studies on melatonin use, including studies on its effect to reduce insomnia for older adults. One such research study was performed by Richard Wurtman at the Department of Brain and Cognitive Sciences at MIT. He studied two groups of elderly subjects; one group had frequent insomnia and the other slept normally. Each subject received either a placebo or a melatonin dose about 30 minutes prior to bedtime, and those who received the melatonin were given a dose of either 0.1, 0.3, or 3.0 mg. Each subject was medicated for 7 days, followed by a “washout” period of 7 days. Wurton found that taking the hormone significantly improved the quality of sleep for the older adults. More importantly, he found that they were able to sleep through the night best when taking the 0.3 mg dose. Now perhaps this shouldn’t be surprising, because the body naturally produces melatonin at this “physiological” level. However, the typical over-the-counter melatonin dose is 3 mg and this was determined to be less effective in helping insomnia.

Despite the many studies that have demonstrated melatonin to be an effective sleep aid, there is still controversy about melatonin use though. Some doctors consider it harmless and others potentially harmful. This is true, in part, because the function of the melatonin hormone may not be fully understood. What is understood is that melatonin does more than just regulate the internal clock, such as affecting the onset of puberty. It is also clear that melatonin is only available as a prescription in many European countries and Canada (although this seems to be due more to ingredient regulatory issues than medical concerns), whereas in the US it is an herbal supplement that isn’t regulated by the FDA.

So what does this all mean? Mostly it means that the human body is a complicated system that we don’t entirely understand. But from what I’ve read, I’ve concluded that melatonin is probably a safe and effective sleep aid for adults (at least those over age 50). Of course, I’m a scientist and not a medical doctor. All in all, it is probably best to speak with your physician before taking it regularly as a sleep aid. If you consider taking melatonin, you do need to remember that it is a sleep regulator rather than a sleep inducer. It isn’t the same as taking something like Ambien or Tylenol PM. You also probably want to somehow chop up the over-the-counter pills into smaller pieces (doses) without getting a crumbled mess. For now, I’m just going to stick with daily exercise, relaxing before bedtime, Advil for sore muscles, and the World Finest Ear Plugs for peace and quiet. Sweet dreams.

Why Is Solar Power Expensive?

sun setting in palm of hand
Courtesy of nothingsogoodphotography via Creative Commons

President Obama has mandated a new energy plan that requires 10% of electricity consumed in the U.S. come from renewable energy sources, such as solar power, by the year 2012. Can we make that goal? Should we with the current technologies?

Just about everyone likes the idea of using solar power to heat and cool their homes. The sun is a potentially clean, free source of energy. What’s not to like about that? We even already have working residential solar power systems on the market. So why isn’t everyone doing it already? Why is only 0.01% of the United State’s electricity generated from solar power? The answer, of course, gets down to cost.

The basic problem is that standard solar cells are expensive and not very efficient. Solar cells are typically 15% efficient. However, the sun is not always out and it is directly overhead only rarely. If you take into account these factors, the average solar cell efficiency is only a few percent. That means that the average solar cell will deliver about 4% of a kilowatt of electric power, if it has an area of 1 square yard. The average household in the U.S. uses about 1 kilowatt of electric power (or 24 kilowatt-hrs per day of energy), which is the equivalent of having 10 100-watt light bulbs turned on. So the average household would need about 25 square yards of solar cells (i.e., 25 sq yds x 0.04 kilowatt/sq yd = 1 kilowatt). Placing this many solar cells on the roof is feasible for many homes, so some people are doing it. It is environmentally clean and politically “green.” Sounds great, right? The problem for most people is the up-front and overall cost.

The price of residential solar power is variable, of course. For the sake of discussion though, I’ll use some 2008 numbers based on California usage (without worrying about issues like tax savings). For a home that uses 1 kilowatt, it costs about $14,000 to have a sufficient residential solar system installed. That means that if you invest $14,000 up-front, you don’t have to pay monthly bills for electricity (except possibly some minor fees for maintenance, but lets ignore those). The amount that an electric power company would charge you for that energy varies, but it averages about 10 cents for 1 kilowatt for 1 hour which translates into $876 per year. If you never have to replace your solar cells, that would mean that you are getting a 6.2% average on your $14,000 investment. Pretty good. The problem is that the solar cells don’t really last forever. To break even, an actuarial calculation shows that the cells would have to last 22 years. If they require repair or replacement sooner than 22 years, which is likely, then you’re actually losing money.

There is some good news though. Currently turning solar power into electricity is expensive, but using the heat directly can be highly efficient without requiring expensive solar cells. As a result, solar-powered water heaters or swimming pool heaters are more popular and economically viable. So you might want to consider those alternatives, if you want to lower your carbon footprint.

Hopefully residential solar heating and cooling will become more attractive in the future, when significantly less expensive and more efficient solar cells have been developed and mass-produced. Stay tuned for future blogs on the science of solar power, since there is a lot of interesting research currently underway.