Thursday, 22 November 2012

Correlation vs Causation

I recently came across this BBC article, which is a good example of correlation (most probably) without causation, but disappointingly, I feel the journalism lets it down slightly.

To quickly summarise the article, the BBC presents a graph of annual chocolate consumption and Novel price winners per capita, which demonstrates a very strong correlation, strong enough that there is only a one in ten thousand chance that the correlation doesn't exist. The BBC then presents several quotes from scientists saying that they believe chocolate helped them, before finally, right at the end, does it discuss the prospect that this is an example of correlation without causation, which is a common occurrence in science.

In a nutshell, just because a graph shows a correlation between two things, you can't conclude that one causes the other. Wikipedia offers a nice example: a correlation might exist between the number of deaths by drowning, and the number of ice creams sold. So one could conclude that ice cream consumption causes drowning. Obviously, this is ridiculous, a more likely explanation is that ice cream is sold more in the summer, the same time of year as more people are likely to go swimming in the sea. The more people swimming, the higher number of deaths by drowning. The rest of the wikipedia page deals quite nicely with the other types of correlation vs. causation, so is worth a read for anyone not familiar with the concept.

Back to the BBC article, by placing evocative quotes around the edge of the article, and saving the key scientific point until the end of the article, there's a risk that people who don't read to the end come away with completely the wrong message. Reading just a snippet of the article paints completely the wrong picture, which people could take the wrong way. Whilst there is some evidence to suggest chocolate can improve concentration, helping in study, taking it to extremes is obviously going to cause problems. Too much chocolate most likely has health implications that will far outweigh any gains in concentration.

Basically, this demonstrates the importance of effective communication in science, something I don't think the BBC have really succeeded with here. Leaving the main point to the end creates a significant chance of misleading people skim-reading the article, or not getting to the end. Now on a topic such as this, the risks are minimal, but take an important scientific issue, like nuclear fuel, for example. Say you want to tell people about new ways of dealing with spent nuclear fuel. Writing an article about the dangers of spent nuclear fuel, and the health issues it can cause, before finally concluding with "but actually, we've solved this now", runs the risk of giving people the wrong idea, and turning more people against nuclear power. Now the issue is not just people eating chocolate for the wrong reasons, you're impacting on public opinion of energy policy, which can have far reaching implications.

As always, comments, criticism and corrections are greatly appreciated. Thanks for reading.

Tuesday, 20 November 2012

Sports Drug Doping Part 2: How did we catch them?

So it's all well and good knowing what compounds are banned (part 1 is here for anyone who missed it), but how do the anti-doping agencies actually go about catching them? (Oh and if anyone would rather read about this in the literature, you'll find Chem. Soc. Rev. 2004, 33, p1-13 of interest, it's my main reference for the rest of this article)

Well firstly, cycling subjects athletes to more drug tests than any other sport. Drug tests are usually performed on urine and blood samples taken from athletes, either during events, or at random drug tests administered during breaks. Elite athletes have to constantly keep anti-doping agencies aware of their location at all times, so they can always be subjected to random drug tests. The first point worth making here is that the labs receiving the samples are given no indication as to who provided the sample. The samples are simply numbered, to ensure the integrity of the analysis. Also, when samples are collected, they are immediately split into 2 identical samples. The analysis is carried out on one vial, and only if there is significant evidence of a banned substance being used, is the second sample opened to confirm the result is genuine. As with forensic samples, there is a chain of paperwork associated with each sample, so that if suspicions are raised about tampering with the samples, everyone who has had contact with a sample is listed.

The labs themselves have to be up to an international standard. Wherever the Olympics are held, the IOC require that the host nation provide a dedicated drug testing facility, up to their exacting standards. For the 2012 Olympics, GlaxoSmithKline provided the state of the art facilities. By building a new facility every 4 years, a network of olympic-standard drug testing facilities is being established across the globe, providing testing facilities for other sporting events.

So once the samples are collected, and sent to the lab, what happens?

Well, urine samples allow detection of the majority of banned small to medium weight compounds, by fairly standard analytical chemistry techniques such as mass spectroscopy and gas chromatography. For larger molecules such as peptides and hormones (like growth hormones), a biological immuno-assay might be necessary.

Another complication is that to detect a molecule, and the amount at which it's present, an analysis has to take into account the effects the body has on the molecule. In some cases the molecule may be excreted intact, but others may be metabolised to smaller, or altered molecules, and of course some are between these two extremes. Once this is done, the work of an analytical chemist is to decide the best way to determine the quantity of each compound, and to accurately carry out the analysis. For most commonly detected performance enhancing drugs, standard operating procedures will exist to determine the amount present.

So how is the analysis itself carried out? Let's use stimulants as an example. Since taking stimulants can provide an instantaneous benefit in a race, they must be detected fairly quickly. Many stimulants are closely related structurally to amphetamine, giving them similar properties. By tailoring conditions to match these common properties, it is possible to extract most likely stimulants from a urine sample. In the standard protocol, this is achieved by extracting into a solution of ether at a pH above 9.5. This sample can be tested by GCMS (Gas Chromatography coupled to Mass Spectroscopy), to comfortably detect amphetamines at a concentration of 500 ng/mL.

What happens to athletes who test positive? Well, it depends on the sport. Currently, an athlete found guilty of doping by WADA receives a 2 year ban for a first major offence, with a life ban for a second offence. But WADA want to increase the ban for a first offence to 4 years. Different authorities however have different rulings and the recent events surrounding Lance Armstrong further complicate matters. Those who implicated Lance Armstrong in confessions to USADA appear to have been given significantly reduced bans, with some only receiving winter bans, which will have little effect on them competing. Whilst Armstrong himself was banned from professional cycling for life.

What about the future? Well the gains offered by doping will always appeal to some, but increasingly complicated doping programs will be necessary to outwit the authorities using the current drugs available. However, the idea of 'designer drugs' could make things very difficult for the testing agencies. A few years ago, Canadian customs officers seized bottles containing a drug called desoxy-methyl-testosterone (DMT). Analysis showed it to be a designer steroid, with similar effects to testosterone, but a drug which would never have shown up in a drugs test at the time. The spectre of this will always hang over elite sport. The development of new drugs can't be predicted, so testing agencies are reliant on obtaining samples of the new drug before they can begin to test for it. With enough money, it would be possible to both create a new drug, or obtain exclusive supply, and to rigorously keep it safe, so that drug testing will be kept in the dark, allowing those cheating to escape without detection.

So can we ever be sure sport is free of drugs? Well, the simple answer is no. The recent revelations about Lance Armstrong seem to have left a bad taste in the mouth of many elite athletes, such as Bradley Wiggins, and many teams too have come forward as being actively anti-doping, with hardline policies on it. But, whilst it is becoming increasingly difficult to dope, some will still keep trying.

Apologies for the delay in writing this, uni has kind of got in the way recently. As always, any comments/criticisms/corrections are greatly appreciated.

Friday, 2 November 2012

I couldn't resist tearing this to pieces...

"Rawforbeauty" uploaded this picture on facebook a while ago, but I've only just seen it:

Wow. So the first question is, where do we start? Oh, and actually, before I do, I should probably point out that I don't work for, or have any connections to, any large pharmaceutical, agrochemical, etc company, I'm just a chemistry student concerned about the propagation of chemical mis-information. Anyway...

I could argue that Pfizer don't (to my knowledge) own Nutrasweet, with Monsanto themselves stating that the business was sold to J.W. Childs Equity Partner. I could also argue the reason it was sold was purely economic as Aspartame has been off patent in the EU and USA since 1992, and it's perfectly logical to sell a business with little money left in it. But, this blog is about science not economics, so I'm going to focus on debunking the claims in the paragraph of lies at the bottom:

  1. Fluoride occurs naturally in a lot of tap water, and in some areas where the natural concentration is low, it is added. There is a lot of medium to poor quality research on this, but it has been analysed and what conclusions can be drawn are summarised in this paper. They conclude that the presence of fluoride in tap water helped to reduced caries and tooth decay in children. There was some evidence of increased fluorosis (normally harmless, and in most cases barely noticeable, white streaks in tooth enamel), and crucially, the study concludes "No clear evidence of other potential negative effects was found". Clearly, it is baseless to call fluoride in tap water a poison.
  2. Is Aspartame poisonous? In a word - no. If you want more than that, then this MSDS summarises it quite nicely: "A vast database exists regarding the safety of aspartame in man.  Oral doses of 75 mg/kg/day to human subjects for 6 months did not produce any clinical signs.  The Acceptable Daily intake (ADI) approved by the U.S. Food and Drug Administration (FDA) is 50 mg/kg/day.  The oral LD50 in rats is >5000 mg/kg (practically nontoxic).  Inhalation exposure of male and female rhesus monkeys to aspartame at concentrations up to 16 mg/m3, 6 hours per day for 14 consecutive days, did not produce any consistent treatment related effects" - I really don't think I need to say any more, but if you want even more reassurance, this is a pretty good read.
  3. If you're going to use 'scientific data' to back your claims up, at least make sure it stands up to scrutiny. For a start, only one study (without proper reference) is mentioned, and with a sample size of 7, it's hardly convincing. It's also interesting that when looking online, I can't find the paper itself, only lots of people damming aspartame and using it to support their case. Sadly, without the paper, I can't tell you just how well designed the experiment was, irrespective of the tiny sample size. But, let's take a look at the literature properly, and find a nice, recent, peer-reviewed article, which states: "The studies provide no evidence to support an association between aspartame and cancer in any tissue. The weight of existing evidence is that aspartame is safe at current levels of consumption as a nonnutritive sweetener." and "Critical review of all carcinogenicity studies conducted on aspartame found no credible evidence that aspartame is carcinogenic." Personally, I find that pretty reassuring.
  4. Yep, Aspartame is manufactured from phenylalanine, which is produced by genetically modified e-coli to produce it as a by-product. Well done- but that's as good as it gets. GM bacteria are used to produce a whole host of products, the most well known being insulin, I don't see too many people complaining about using GM bacteria (which are probably e-coli derived) to save the lives of hundreds of thousands of people, or calling for a return to the bad old days where insulin had to be extracted from cadavers of pigs and cows. This has a moral or religious concern for many people, as well as issues of rejection, and reduced efficacy. (Although, I'm getting away from my argument now). Back to E-coli. Firstly, most strains of e-coli are perfectly harmless, and many strains are found normally in the gut of healthy humans and animals. I don't have a problem with this being modified to produce my sweetener. Especially as heat treatment, purification, etc, will kill and remove the bacteria long before it gets anywhere near me.
  5. Defecating aspartame? Don't make me laugh. Defecating usually implies some kind of gastro-intestinal tract, which clearly bacteria don't possess. The process could be described as being equivalent to breathing or photosynthesis, but that doesn't make for quite such a catchy soundbite. Nobody is complaining that the oxygen we breath has been "defecated by plants", so quit moaning about this too, or at least be consistent in your opinions and eliminate oxygen from your daily diet too.

Basically, the whole image stinks of a 'chemicals are bad and should be banned' attitude. I'd be surprised if people who believe this ever read my argument above, even moreso if they follow the links to respectable sources, and be over the moon if realise that maybe their belief isn't supported scientifically, and should think about changing it. Sadly it wouldn't surprise me at all if they pay absolutely no attention and continue to advocate banning something there is little evidence to show is dangerous. Have these people heard of the risks of dihydrogen monoxide? It's possibly one of the biggest killers in the world today, and I guarantee you'll find it in every single human being on the planet.

This kind of post isn't really what the blog is about, but if one person reads this and changes their opinion, then it's worth it. I can't stand 'chemophobia' (a common theme amongst chemistry bloggers), so if anyone spots any other examples of this kind of rubbish then leave a comment, and I'm more than happy to tear each one to pieces (there's easily enough out there to make a series of posts out of this).

Oh, and as always, if you find a fault, want something explained further, or have anything else to say, leave a comment and I'll get onto it.