Friday, May 16, 2003

Passive smoking: report rejects cancer link

Researchers have reanalysed data produced by the American Cancer Society and concluded that no risk from environmental tobacco smoke (ETS) can be demonstrated from the figures.

What the paper illustrates is the difficulty of drawing firm conclusions from such a longitudinal study. Although the numbers of people involved are very large, there are so many different factors to be taken into account that any result may just be 'noise'. For example, it would be impossible to measure the effect of ETS on smokers, because the effect would be drowned out by the known relation between smoking and cancer. So, the focus is people who have never smoked who live with a partner that does smoke. The problem is that there is no accurate measure of how much smoke someone consumes, there can only be an estimate. How do you compare these estimates both with each other and with reality? Then there is the problem of whether the 'never smokers' really do abstain completely. Is it really possible to find people who have no exposure to smoke? Thus, it is difficult to know just how much exposure there really is to ETS.

Then, there is the problem of working out a rate of cancer that takes into account class, diet, age, sex etc. Many of these factors are themselves subject to discussion about the level of risk associated with them. So, it is difficult to produce a definitive comparison.

Therefore, a longitudinal study can only be of much use if the result indicates a strong association. Hence, reported risk factors of less than 2.0 are usually ignored. Yet, the ETS debate has been driven by studies showing much weaker relationships, made statistically significant only by combining different studies together, a technique itself riddled with problems.

The only safe thing to say about ETS and ill-health is that a relationship has not been established, and if it is, it is likely to be weak. Which, given that non-smokers in smoky environments inhale only a fraction of the smoke that the smokers themselves inhale, seems to make sense.

Row over passive smoking effect, BBC News, 16 May 2003

Thursday, May 15, 2003

SARS update

Good news: Canada officially has SARS under control (e.g. report in The Toronto Star). The number of new cases in Hong Kong reported each day remains in single figures and there has been a continuing drop in cases in China. In fact, the outstanding number of cases in China has plateaued as recoveries begin to outpace new cases.

Bad news: cases in Taiwan have accelerated, with 31 new cases in 24 hours according to the last set of figures published.

Here is the latest Excel spreadsheet of total, Hong Kong, and mainland China cases.

SARS and cars

One reaction to the outbreak in China has been an increase in car purchases as people seek to avoiding using mass transit systems, according to a report on

'Reuters, citing state media, said that, in April, when China admitted it had covered up the extent of the epidemic that has now infected more than 5,000 people and killed more than 260, car sales in Beijing rose 21% to 34,000. Reuters noted that Shanghai Automotive Industry Corp said April nationwide sales jumped 33% year on year to 46,800. Guangzhou Honda Automotive Co said it sold 17,250 cars, more than double a year ago.'

Wednesday, May 14, 2003

Quote of the day

Leading experts on new variant CJD, the human form of BSE or 'mad cow' disease, have warned the current outbreak could get much worse. So far, 99 people have had the disease and nearly all of them have died. New evidence gathered from experiments on mice suggests this first batch of cases could be followed in a few years' time by a much larger 'second wave'.

'I don't want to be alarmist about this but it's entirely possible and we have to consider that what we are looking at, at the moment is, thankfully, a very small incidence of the disease amongst a small sub-section of the population. It may be five or ten years before the rest of the population of those at risk develop the disease.'

Professor John Collinge, one of the government's top advisors on vCJD and director of the Medical Research Council Prion Unit in London, quoted by the BBC on 14 May 2001.

'Now a study published in the online journal BMC Infectious Diseases by a team of epidemiologists at Imperial College, has shown a further decrease in the predicted magnitude of the epidemic, with an upper limit of 540 deaths, based on the current case data.'

Forecast of human BSE deaths cut again to 500, Daily Telegraph, 7 May 2003

Monday, May 12, 2003

Awareness campaigns

Further to the comment below about the Cancer Research UK report pointing out that cancer is the number one killer of men and women in the UK.

The number one killer is in fact old age. 78 percent of men and 87 percent of women who died in England and Wales in 2000 were over the age of 65. So, even if these awareness campaigns had some success, they won't greatly extend people's lives. But they will increase the amount of testicle-fondling, breast-squeezing and general navel gazing.

The GM Jeremiahs

Nick Cohen wrote an interesting piece for the Observer yesterday in which he looks at the misjudgement of risk. He uses two examples: the Y2K bug (the hugely expensive hunt for software bugs was the financial disaster, not the bug itself) and GM crops. He thinks denying GM to the third world is to impose first world niceties on people who are in desperate need of this technology.

Fair enough. Except that he blows his argument with comments like: 'Which isn't to say that the environmentalists have been proved wrong. Whatever the Royal Society says, absence of evidence isn't evidence of absence. Just because no one has proved that GM food can damage your health doesn't mean that it can't. Friends of the Earth and Greenpeace have a check list of dozens of tests they want carried out. Their spokesmen point out, reasonably, that it is very hard to find out if GM food has damaged Americans because there has been no proper monitoring of who eats what.'

What he misses is that one of the main reasons that countries like Zambia have avoided GM is that they can't export it to Europe. And if they grow any GM, European regulations will make it impossible to export even non-GM crops to Europe. So the niceties of consumers in Europe do have to be challenged, to protect the developing world and to challenge the anti-science views of NGOs like Greenpeace.

The GM Jeremiahs, Observer, 11 May 2003

Cancer is the number one killer of British men... says a report from Cancer Research UK. And they're going to launch a campaign to increase awareness about it. Great.

Except that their report suggests that cancer has hit top spot because death rates from cancer (down 15 percent in a decade) are falling less quickly than death rates from heart disease (down 30 percent in a decade).

So, nobody thought that the headline of the article could be something like, 'Nation getting healthier says report'?

Cancer number one killer of men, BBC News, 12 May 2003

Sunday, May 11, 2003

Global warming: why the fuss?

I attended an interesting session at spiked's Panic Attack conference on Friday about global warming. The three speakers all had slightly different views on whether there was such a thing as man-made global warming. Sallie Baliunas from Harvard suggested that there was nothing out of the ordinary with the current phase of warming, and that there were much more significant events in the last 1000 years. Bjorn Lomborg felt that the IPCC reports were the best attempt at understanding the science we had, and these predicted anthropogenic warming. However, he argued that while the cost of coping with such warming was considerable, the cost of attempting to stop it would be greater and probably pointless. Mark Saunders of University College London argued that, while there was warming occuring, any increase in extreme weather events was far less significant than the ordinary year-on-year variation.

What I thought was: why the fuss? The human race as a whole is certainly not threatened by global warming. For developed countries, the impact is likely to be neutral. Developing countries may well have difficulty in dealing with some aspects of the problem, but those countries have much bigger problems on their plates right now. Simply providing the world's population with clean drinking water or freeing them from easily tackled diseases, seems much more important than tackling an effect which may or may not be happening, may or may not be under our control and whose effects are likely to beneficial in some areas.

Can we cope with a warmer planet? Of course we can. One only has to look at the range of situations that humans live in at present to see that this must be so. I have friends living in Norway in average temperatures of -20 degrees Celsius, and in Ghana with summer temperatures well in excess of 40 degrees Celsius. Even with a single city, there can be wide variations. New York is frequently covered in snow in winter but also hits 38 degrees Celsius regularly in the summer. Yet, New York is prepared and can cope.

So, the issue is surely not whether we can cope with variation in average temperatures but having the resources to deal with it. Hence, many parts of the developing world do not yet have the wealth to cope with the consequences of global warming. That's not a surprise, when the developing world doesn't have the resources to cope with many other problems either. Let us focus on the problems we have here and now before we start to fret about what might happen in the future.

SARS update

Things in general continue to improve. The number of new cases reported each day in China is falling quite sharply now. The average new cases reported per day now stands at 143 per day for the last five days:

New cases per day for Hong Kong are now running in single figures. The number of people in Hong Kong who have now recovered greatly outnumbers the outstanding cases.

Excel file of SARS cases to 10 May 2003.