Archive for September, 2009

Do ‘safe’ levels of lead harm children?

September 30, 2009
Picture of some lead balls

Picture of some lead balls

The BBC reports that ‘Safe’ levels of lead levels are harming children. The article reports a study by researchers at Bristol University, the gist of the article can be summarised in this quote

After taking account of factors likely to influence the results, they found that blood lead levels at 30 months showed significant associations with educational achievement, antisocial behaviour and hyperactivity scores five years later.

With lead levels up to five microgrammes per decilitre, there was no obvious effect.

But lead levels between five and 10 microgrammes per decilitre were associated with significantly poorer scores for reading ( 49% lower) and writing (51% lower).

A doubling in lead blood levels to 10 microgrammes per decilitre was associated with a drop of a third of a grade in their Scholastic Assessment Tests (SATs).

The italics and emboldening of the text are mine. I have highlighted this text because it is at the heart of the reason that I simply don’t believe this story. Before you make up your mind you may wish to see the extensive documentation on this issue of the US CDC. There you will find extensive survey data, and if you look for ‘tips’ you may find the following text:

How are children exposed to lead?

Lead-based paint and lead contaminated dust are the main sources of exposure for lead in U.S. children. Lead-based paints were banned for use in housing in 1978. All houses built before 1978 are likely to contain some lead-based paint. However, it is the deterioration of this paint that causes a problem. Approximately 24 million housing units have deteriorated leaded paint and elevated levels of lead-contaminated house dust. More than 4 million of these dwellings are homes to one or more young children.

Who is at risk?

All children under the age of 6 years old are at risk because they are growing so rapidly and because they tend to put their hands or other objects, which may be contaminated with lead dust, into their mouths. However, children living at or below the poverty line who live in older housing are at greatest risk. Additionally, children of some racial and ethnic groups and those living in older housing are disproportionately affected by lead.

Once again the highlighting is mine. The truth is that that there is an overwhelming correlation between poverty and poor educational and behavioural achievement. This is the case for all kinds of reasons. And despite the fact that people have tried to compensate for it in studies I simply don’t believe it can be compensated for. What this story is really about is this: poverty is bad for children’s development. Lead toxicity – at these ‘safe’ levels at least – is really the very least of these children’s problems.

P.S. If you do want to reduce your child’s exposure to lead then the CDC have the following advice for you:

  • avoid using traditional home remedies and cosmetics that may contain lead;
  • avoid eating candies imported from Mexico; (I read this as candles!)
  • shower and change clothes after finishing a task that involves working with lead-based products such as stain glass work, bullet making, or using a firing range.

Acknowledge Ignorance

September 28, 2009

Climate Change as a ‘news story’ will not go away as we approach the Copenhagen Conference in December. But even as news stories surface I find my skepticism stiffening. The fact is that while the evidence for anthropogenic climate change is strong and growing, we simply do not know what is going to happen next. We have projection after projection but in the short term >none< of the models have predicted the decade of relatvely stable temperatures we have just experienecd. And this is the uncomfortable reality we have to acknowledge: we don’t know what is going to happen. We really really really don’t know what will happen next, but we still have to act in the face of this ignorance.

I feel strongly that we need to acknowledge our ignorance. Only when we are clear about ‘where we are’ can we sensibly decide ‘where we want to go’.

Flying to Torino

September 28, 2009
Water vapour and droplets in the atmosphere

Water vapour and droplets in the atmosphere

I spent last week in Torino discussing experiments which will lead to a new estimate of the Boltzmann constant and eventually lead to a redefinition of the kelvin and the celsius, the units of temperature. I was crazily busy the week before – and most of the weekend before too – writing a paper and a talk. But as I sat on the plane out there, my anxiety was momentarily relieved. I gazed out the window in awe and reflected on what I saw.

Firstly I gazed at England and France and Italy, and reflected that there was not a single a single square centimetre of the land surface of Europe which had not been affected by humanity. Subsequently I have relented and I would acknowledge that there are regions of the Alps where this is not true. But I still contend that anywhere where anything grows, it is true. Broadly speaking, we have cut down all the trees and planted stuff or built houses. The scale of what humans had done to the surface of the Europe was overwhelming. I gazed down from a height of 38,000 feet and could see the hand of humanity writ large beneath me.

Secondly I gazed at the clouds. Their almost unbearable brightness told me about the amount of sunlight they reflected. I imagined how the temperature of the air would vary as one rose up from the ground into the clouds. I imagined the temperature falling and then – as the water vapour condensed, stabilising as the latent heat of the water was released. I imagined the impenetrability of the cloud to the infra red light being radiated from the Earth’s surface. I stared at the clouds fascinated by their endless variety. I saw cascading towers and the wisps of mist. I saw them form at different heights and I saw the gaps. And I felt acutely aware of how the water vapour in the atmosphere totally dominated the radiation balance of the Earth. But I reflected on the impossibility of accurately modeling the complexity that lay beneath me.

And I reflected on the 200 kg or so of carbon dioxide that was being released into the atmosphere as a result of my 650 mile trip. And the 200kg I would release on the way back. Later I travelled in a taxi with my colleagues and thought about just how efficient cars were at delivering people from one point to an exact location where they wanted to be. And I reflected that when four people travelled together in a  car,how little carbon dioxide was produced per person. But that it was just the requirement – or the desire – to travel hundreds or thousands of kilometres in  few hours that caused the carbon emissions. The mode of travel – plane or train or car – made relatively little difference to the amount of carbon emitted. With one exception. If I had travelled across France by TGV powered by electricity generated in a nuclear power station my carbon emissions would have been kilograms rather than hundreds of kilograms. And if the taxi to Torino had been electric and charged by nuclear or renewable energy then  it would have emitted negligible carbon on its journey. And I that imagined journeys such as the one I was making could still be made while emitting a tiny fraction of the carbon I had emitted.

And after my reverie I returned to a week of incredible busy-ness and meetings. But more of that on another evening.

I’ve been blogged!

September 17, 2009
Fun at the British Science Association Festival

Fun at the British Science Association Festival

Wow! Someone blogged about me! Wow! I have now entered the blogosphere and will return to planet Earth in due course…

Who will pay for Mobile Phone Safety Research?

September 16, 2009
Senate Sub-Committee hearings on mobile phone safety

Senate Sub-Committee hearings on mobile phone safety

An article on the register today referred to a story on CNET about senate hearings concerning mobile phone safety. The Register article is typically juvenile, but the CNET article is long and modestly well informed. Well at least it rather longwindedly reports what was said in what I now realise is a manner characteristic of american journalists. Its the kind of article which would never appear in a UK publication. There are a couple of interesting points.

Firstly there was the recommendation that people should only talk when the signal from the base station was strong. This implies (correctly) that safety would be improved (i.e. dose would reduced)  if we increased the number of cell phone masts. And I guess that would be just about as popular in the US as would be in the UK. So we have at the core of the issue a basic refusal of people to agree to simple measures that would improve their service level and safety. Why? I have not a clue.

The simplistic concept of ‘safe’ was again laughably introduced, but the report does not refer to any discussion of the need to weigh risks and benefits when the risks are not fully known. This is the case in many situations and if we could acknowledge the reality of the situation we would already be so far ahead of where we are now. We need to acknowledge our ignorance, the need to take time over research, and the probability being that at the very least that there would eventually probably be measureable ‘effects’ which might or might not be harmful.

Martin Blank’s comments that heating of the tissue was irrelevant is not quite right. It is a fair measure of dose. The problem with people arguing that there are effects caused by non-thermal mechanism is that there aren’t any that anyone can think of. Temperature is a measure of the level of jiggling that key molecules such as DNA experience within the body. Each photon of energy from the phone signal provides a force on the molecule around 10,000 times less violent than that which the molecule experiences normally in the body. It would be really surprising if DNA was that sensitive. That said, the precautionary principle is probably wise.

Finally the issue of putting in a place a mobile phone tax of one dollar per phone bill was not well received. But actually the level of funding required for this research is not so great. In the UK I believe we spend a few million pounds each year on this – a few pennies from each mobile phone customer. I would have thought a tax at a similar level – perhaps  1 cent per bill  – would raise many tens of millions of dollars which would be enough to get started.

And what do I learn from all this? That the issue rolls on, and I predict, will roll on and on for many years to come.

The North East Passage

September 12, 2009
Ships in the ice-free North East Passage

Ships in the ice-free North East Passage

Occasionally a newspaper gets it right and I find myself thinking ‘Yes, thank you for noticing that something was ‘news’ which no one else noticed’. So today The Independent devoted their front page to the news that two freighters were about to complete a voyage from South Korea to Rotterdam by sailing north of northern Russia through the Arctic Ocean. In recorded history this has never been possible even in the short Arctic summer. This marks a milestone in the progress of the Climate Change we are experiencing, and a likely end to the pristine nature of this region. As the independent aptly puts it: A triumph for man, a disaster for mankind:

News? UK ‘could face blackouts by 2016’

September 11, 2009

Another interesting ‘story’ on the BBC today. It concerns the possibility that collectively the UK will not ‘get itself together ‘ in order to plan new power stations. This possibility is interesting, – indeed alarming – but I have commented on the possibility (here and here) and the ‘story’ here is that there is actually no ‘news’. But how can there be a news story on the BBC if there is no news?

Professor David MacKay

‘News’ can also happen when someone says something. Professor MacKay is about to become a government advisor and radically he said

“There is a worry that in 2016 there might not be enough electricity. My guess is that what the market might do is fix that problem by making more gas power stations, which isn’t the direction we want to be going in,” he said.

“So we really should be upping the build rate of the alternatives as soon as possible.”

Professor MacKay blamed the public for opposing wind farms, nuclear power, and energy imports, whilst demanding an unchanged lifestyle. ‘You cannot oppose them all, he said, and hope to have a viable policy on energy and climate change. We’ve got to stop saying no to these things and understand that we do have a serious building project on our hands,” he said.

The ‘news’ story here is that this contradicts a hypothetical reality called ‘government policy’. So the ‘news’ story here is nothing to do with the reality of the technical, social, economic, engineering and ecological issues facing us all. This became a news story because there is a possibility of embarrassing the government. This is the nature of all news. The occurrence of a news story is not about the reality or significance of the content of the story, but of the proximate possibility of conflict. I have not had much in the way of media training (What? You can you tell?) but my one day course on writing press releases said simply – identify the conflict and you have your news story. So

  • A story about power cuts in the UK is not newsworthy. But a story about someone who says there will be power cuts and a person who says there won’t be is newsworthy.
  • A story about ecological damage caused by modern farming techniques is not news – until farmers have an argument with ecologists.
  • And the story of the century about Global Warming can drift to the back pages until some people find some aspect of it to argue about.

Sometimes I wish the BBC could step outside the dictates of the ‘news agenda’ and just focus on what I call ‘reality’.


Now the BBC have another story: Mr Miliband gives no acknowledgement of the reality of the problems highlighted by David Mackay, he just denies there will be power cuts. Personally I think Professor Mackay has a good point which goes unacknowledged by Mr Miliband. I do not think those who are fortunate enough – which generally means rich enough – to live in the windy places around our shores should be able to force the rest of us – who of necessity live in cities – to pollute the atmosphere massively rather than disturb their views. If it were up to me I would just build the wind farms and the barrages as quickly as possible.

Why do Helium balloons rise?

September 10, 2009
Druck DPI 150 Barometer

Druck DPI 150 Barometer

The standard answer to this question is that helium balloons rise because they are ‘lighter than air’. And this is true, but it is in some ways an unsatisfactory answer. When something experiences a force we can usually ascribe that force to some agency, but in the case of the helium balloon, the agent responsible appears to be rather mysterious. Gravity still pulls the helium balloon ‘downwards’ so what is it that pulls (or pushes) the balloon upwards?

The answer is pressure. The pressure of air above a helium balloon is less than the pressure of air below it. The difference in pressure gives rise to a net force on the balloon which lifts it upwards. This buoyancy force is present on all objects, but is so small we normally don’t notice it. Now most people’s response to this fact is simple disbelief. They will acknowledge that the pressure is indeed lower, but will argue that the difference is tiny. They are right, but then the forces lifting up a balloon are not that strong. I have done the maths on this, and amazingly the pressure change is just exactly sufficient to yield Archimedes law. But yesterday I went one step further.

We have a very sensitive barometer in the laboratory (a Druck DPI150 if you are interested) and normally it sits trapped in its rack, but a colleague asked to borrow it the other day (data on that escapade soon I hope). And since it was sitting on the bench I switched in on and lifted it up and despite the fact that I expected it to happen, I was amazed to see the pressure fall by around 10 Pascals as I lifted it up above my head, and then to increase again as I put it back on the bench. Now this fall is only 0.01% of atmospheric pressure and would not be noticed by most people or most pressure measuring equipment. And I thought this was an example where the ability to simply measure something directly really gave an extra insight into the way the world worked.

Sometimes, I really enjoy my work 🙂

What is happening to the Earth’s temperature?

September 9, 2009
Whole Earth Temperature: Past and future projections

Whole Earth Temperature: Past and future projections

The Register reports today with poorly hidden glee that scientists are now revising predictions for the future temperature of the Earth. The Register’s agenda is that the whole Climate Change Issue is a job creation scheme for scientists and a tool for bureaucrats to use to extend their control over our lives. Both these perspectives are interesting and not without an element of truth. But the Register’s attacks are juvenile in the extreme because they fail to really address the questions to which we all want the answers. And what are those questions?

Are we (human beings) affecting the climate?

The answer is simple. Almost certainly. It is not certainly. The answer is almost certainly.

What will happen to the temperature of the Earth in the future?

The answer is simple: we don’t know. We really don’t know. And just to make clear I will repeat that again. We really really really don’t know. And if the IPCC acknowledged that more clearly they would be in less trouble than they are now going to be in. The fact that the actual temperature of the Earth appears not to have changed in the last decade is, to say least, uncomfortable for climate ‘zealots’ and those who sense the nearness of the ‘end of days’. But for scientists – and indeed for people in general – who acknowledge the long times scales involved in climate change and the general complexity of the Earth’s climate, the fact that we have been unable to predict the correct temperature rise for the Earth is irrelevant. Presciently, I wrote about this issue last March and so I am going to allow myself to momentarily feel smug. …. OK.

The climate models used by the IPCC cannot include physics that we do not know about. And deep ocean circulation which shifts vast amount of warmed water into the deep oceans where they have relatively little climate impact in the short term is a completely plausible explanation for the data. The ‘problem’ here is political rather than scientific. Some scientists have seen the sharp rise in temperature of the last 30 years and extrapolated to ‘thermageddon’ and politicians have based their pitch to the public upon this. Motivating people to reduce their carbon emissions by 90% will not be easy if the Earth cools instead of warming. I predict ‘interesting times’ ahead.

Radioactive emissions from coal-fired power stations

September 8, 2009
A poorly child

A poorly child

Nothing is as simple as it seems.

A recent story in the Guardian has brought to the fore something many physicists have known for years: that radioactive emissions from coal-fired power stations dwarf radioactive emissions from nuclear power stations. The Guardian story is sad for two reasons. Firstly, it highlights the plight of disabled children in a desperately poor part of the world. However, the story is equally sad because its allegation that uranium poisoning from coal-fired power stations is to blame is simply an assertion and the Guardian journalist in question seems uninterested in clarifying the central question: are these children’s birth defects dues to uranium poisoning? Let me expand:

Thorium and Uranium metals are present in coal at the level of typically a few milligrams per kilogram of coal. After combustion, these radioactive metals become concentrated in the ash which is then disposed of. In the UK I believe, but have not been able to confirm, that most of this ash is used for the manufacture of building materials – breeze blocks and cement. In other parts of the world the ash is used for a variety of purposes and is occasionally spread on farmland, or just left in giant heaps. Because of the very large amount of coal which is burned for power generation in the UK and around the world, this results in a significant amount of radioactive material entering our environment, much more than would be allowed to enter our environment from nuclear power stations.

The Guardian article simply asserts that the plight of these children is caused by Uranium.  But in the whole article there is not a single argument for a connection. The trouble starts in paragraph 3 which states:

Health workers in the Punjabi cities of Bathinda and Faridkot knew something was terribly wrong when they saw a sharp increase in the number of birth defects, physical and mental abnormalities, and cancers. They suspected that children were being slowly poisoned.

This is critical. In every country on Earth children are born with abnormalities and it would be satisfying to be able to blame something or someone for each such case, but that is just not possible. Notice there is no indication of, for example, when they noticed, or how sharp the rise was, or what the level of birth defects is compared  to other places in India. This article simply asserts that the connection is obvious. Others disagree. This link describes the fact that no rational study has been undertaken, and that the person who runs the centre had recently asserted that the children’s problems were caused by Mercury, but this was unsuccessful. Asserting that Uranium is the problem is – according to this author –  simply another way to gain attention and hopefully money.

As I said at the start, nothing is as simple as it seems. In this case I would like to express my frustration at a Guardian article – from which I expect better – simply fails to address the salient point of this issue: that there is no known causal connection between these children’s plight and the levels of uranium in their hair.

In the UK

It is interesting that in the UK, the uranium in ash from power stations is considered potentially hazardous, but not for radiological reasons. It is considered hazardous because, like other heavy metals such as lead, it is chemically poisonous and accumulates slowly. And Uranium is probably not the most hazardous substance emitted from power stations and present in ash. This article on CNN mentions specifically mentions arsenic, lead, chromium, and selenium and I would not be surprised to find many others. I have asked my friend and colleague John Makepeace about this and I hope to have more information soon.

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