The Nuances of Vaccination

anti-vaccine-movement-cartoon-sack
source: Steve Sack and Pat Bagley

Regardless of the issue at hand, there’s a price to pay when we dodge nuances. In recent decades parents have been in the spotlight for refusing to vaccinate their children. In chastising them, we reiterate that they have become suspicious of the “medical establishment” and have been influenced by fiction on the internet. There’s no doubt about the role of such causes, but in trying to change their minds, we also counter with a distorted picture of medical history, as if vaccination programs have placed us on a march towards the elimination of disease, as if modern medicine has enjoyed a record free of blemishes.

Thanks to Gerhard Adam,  I’ve probed into Statistics Canada, which reveals some surprising truths about life expectancy  and have scoured Jacalyn Duffin’s remarkable History of Medicine-A Scandalously Short Introduction. The author, a hematologist and historian from Queen’s,  mentions that in the 1970s Gerald Ford was prompted to start a huge campaign to vaccinate 45 to 50 million people. It was aimed at a flu virus that was perceived to be similar to the one which caused the 1918 pandemic and which claimed 20 to 40 million lives. More details are documented by the Center for Disease Control. Unfortunately, about two hundred vaccinated people contracted  Guillain-Barré syndrome, a rare disorder in which a person’s own immune system damages his nerve cells, leading to muscle weakness and at times paralysis. CDC acknowledged that although some of the cases could have been a coincidence, a small but definite cause and effect relationship was at work. The influenza never materialized either, and the vaccination program was scrapped.

The media at the time portrayed it as a fiasco, harshly accusing the government’s health bureaucracy of acting in self-interest. But there’s an important lesson to be learned, and it’s now included in Annex 11 of DHEW’s (Department of Health, Education, & Welfare) pandemic preparedness plan, which states,

“For policy Asclepiusdecisions and in communication, making clear what is not known is as important as stating what is known. When assumptions are made, the basis for the assumptions and the uncertainties surrounding them should be communicated.”

When such advice is ignored and people are kept in the dark and things go wrong, the ensuing loss of confidence in authority has repercussions far into the future.

Duffin explains the origin of the medical caduceus. In Greek mythology, after Medusa was slain, Athena was presented with the snake-tressed head. She then gave blood to the healer, Asclepios, who used it for cures and to raise the dead. But I learned from Robert Graves’ Greek Myths that Asclepios was given two vials of blood, one from each side of the monster. One vial gave life; the other took it away. It is a somber reminder of medicine’s occasional iatrogenic effects.

Swimming Pool NCl3: Not Innocuous As Once Assumed

ammoniaOnce used as a refrigerant and still made to produce fertilizer, ammonia (NH3) is also a chemistry teacher’s ally. Mix an ammonium chloride solution with base in a small test tube and as hydroxide accepts H+ from ammonium ion, the liberated ammonia gas can easily awaken a sleepy student. Kidding aside, the odor threshold for ammonia varies significantly from one individual to the next (Is there any correlation with the amount of spicy food eaten and insensitivity to NH3—great idea for a student project!)  The amount of ammonia present in sweat is also not constant among different people. Aside from attracting mosquitoes, ammonia released from skin pores gets into swimming pools where it reacts with hypochlorous acid from the chlorination process to produce various chloramines:

NH3 + HOCl → NH2Cl + H2O

NH2Cl + HOCl → NHCl2 + H2O

NHCl2 + HOCl → NCl3 + H2O

The mono and dichloramines, as shown, go on to react and produce the volatile trichloroamine or nitrogen trichloride(NCl3). An acidic pH can also accelerate the conversion to NCl3, which in small concentrations can cause red eyes and nose and throat irritations in swimmers, symptoms that become more pronounced in people working at indoor pools.Indoor-Swimming-Pool-1

Of course, ammonia isn’t the only source of NCl3. Sweat also contains urea, which is capable of reacting with OCl to eventually produce CNCl and NCl3. Another significant source of urea is urine. Any inappropriate relieving on the part of bathers will meet the same chemical fate.

Let’s look at the health evidence more closely. In a 2010 study published in the International Journal of Environmental Research and Public Health, investigators found an average concentration of 0.66 mg/m3 of NCl3 in the air above 20 indoor pools in northern Italy. Among 133 pool workers, those more in contact with the water (swim instructors and especially those who were both pool attendants and instructor) had higher odds ratios for itchy, watery eyes, infections and respiratory problems.

In a fair amount of internet writing, there is a current tendency to either cater to chemophobia or to fight it. In the latter case, writers fall into the trap of overusing the “too low a concentration to cause harm” argument. But here is a clear case of how a small concentration (less than 1 ppm on a per volume basis) of a poison like NCl3 isn’t as innocuous as previously assumed.

From a preventive viewpoint, the research reinforces the value of long standing recommendations to shower and use the bathroom before entering a pool, especially if it is an indoor one with a low ceiling and inadequate ventilation.

Sources:

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2872330/

http://www.chemicalbulletin.ro/Chemical-Bulletin-Article_BCaYw.html

http://link.springer.com/article/10.1007/BF00705070

https://www.jstage.jst.go.jp/article/jjphysiol1950/3/0/3_0_211/_article

http://answers.webmd.com/answers/1198618/why-does-my-sweat-smell-like-ammonia

http://onlinelibrary.wiley.com/doi/10.1046/j.1365-3032.2001.00227.x/abstract

My Favorite Nobel Prize and Why a Flower Beats Any Perfume

Capable of detecting faint traces of smoke, the nose can be a life saver.  Sensitive to esters of fruits and flowers, it can be a source of pleasure. Through its associations with the hippocampus, it can serve as a unique gateway to episodic memories. When the brain gathers information through the nose, it does not rely on the electromagnetic spectrum. Like touch and taste, smell is a sense that’s in direct contact with matter.

Decades ago, some chemists imagined that through its shape and functional groups, a particular odiferous molecule was interacting with a single type of receptor. But the simplistic speculation had its shortcomings. The mechanism’s truth turns out to be far more intricate.

Richard Axel and Linda B. Buck won the 2004 Nobel Prize in Physiology for their discoveries of odorant receptors and the organization of the olfactory system. Independent of each other’s work, they experimentally found evidence for the following bouquet of ideas:

(1) For every olfactory receptor cell, there is an odor-receptor, coded by a single gene. The related genes(about 400) that code for olfactory receptors probably make up of the largest gene families.odorants

(2) One receptor can respond to a variety of similar odorous substances, For example, receptor 2 in the diagram can interact with both hexanol(B) and heptanol(D). But the coupling-reaction from one molecule will not necessarily be identical in intensity to that of the other.

(3) There could be a main component of a particular smell, but more often than not, the smell will often be triggered by two or more compounds. For example a rose contains three major constituents: two different ketones and cis-rose oxide. But there are hundreds of more compounds, all of which contribute to its its fragrance. (In 5 decades, the number of odorous compounds discovered in the rose increased by a factor of 20.)

Now here comes my favorite part:

(4) A specific combination of receptor-interactions is needed for a stimulus, so a given receptor can play a role in various smells. Thus not surprisingly, for about 400 receptors, there are about  10 000 or so different odors that we recognize. For example, in the diagram, hexanol’s interactions with receptors 2 and 6 leads to a sweet, herbal smell.  The same receptors along with receptor 5, when interacting with heptanol, lead to a smell that’s sweet and violet-like. Returning to the rose, each of three main fragrant compounds is responsible for a key combination. Our perception is based on a mosaic of at least those three receptor-combinations along with a bouquet of all the other fragrant components of the rose.

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A rose and especially a citrus blossom are far more interesting than the most expensive perfumes. Flowers do not spray compounds into a mist; often the molecules are secreted from the surface of petals and other parts; at times they start as liquid and evaporate when air collides with them.  It takes thousands of flowers to yield a few hundred grams of the essential oils used in commercial products. In cheaper perfumes only a few of the fragrant compounds are synthesized. Instead, a single flower is sufficient to excite our senses. It synthesizes its perfume on location and does not have to deal with preservation issues.

Cheese_limburger_editThere is more odor science to to be revealed on the matter, to be sure. The year after the prize was awarded, after using vaporized odorants delivered either through the nose(orthonasal) or the mouth(retronasal), investigators measured brain responses with fMRI. They were not the same. This explains the Jekyll and Hyde signatures of the durian fruit and Limberger cheese. Both smell bad when they are not in your mouth; durian smells like rotten onions and Limberger is produced from the same bacteria that make sweaty socks reek. But while these foods are being ingested, the unpleasant smells are not perceived and replaced by a pleasant blend of taste and alternate aromas.

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