Thursday, February 07, 2013

Heavy traffic fumes could increase risk of having a small baby

If ever there were an old chestnut, this is it.  Just the usual correlational rubbish that fails to account for third factors.  Though I am pleased to see that the authors did adjust for maternal socioeconomic status.  The message about social class may be beginning to penetrate in these studies.  Income would be more relevant however and, given the small size of the reported effects, an income adjustment could well wipe any differences out entirely

The journal article is: "Maternal Exposure to Particulate Air Pollution and Term Birth Weight: A Multi-Country Evaluation of Effect and Heterogeneity" by Dadvand et al.

Heavy exhaust fumes produced in traffic-jammed cities increase the chances of women giving birth to small babies, researchers say.

A study involving millions of births around the world found that higher air pollution levels raised the risk of low birth weight.

Although small, the effect is said to be statistically significant. At national population scales it could have an important impact on child health, said the researchers.

Babies are underweight at birth if they tip the scales at less than 2,500 grams, or five pounds eight ounces.

They face an increased risk of dying in infancy, as well as chronic poor health and impaired mental development.

The new study, the largest of its kind ever conducted, focused on tiny sooty carbon particles called PM10s and even smaller PM2.5s which are known to be linked to heart and lung problems and early death.

They originate from a number of sources, including diesel exhausts and the chimneys of coal-fired power stations and factories.

Professor Tanja Pless-Mulloli, who led the UK arm of the study at the University of Newcastle, said: 'As air pollution increases we can see that more babies are smaller at birth which in turn puts them at risk of poor health later in life.

'These microscopic particles, five times smaller than the width of a human hair, are part of the air we breathe every day. What we have shown definitively is that these levels are already having an effect on pregnant mothers.'

The research, published in the journal Environmental Health Perspectives, examined the impact of a 10 microgram per cubic metre increase in average exposure to pollution particles over the course of a pregnancy.

For PM10s, this raised the chances of having a low birth weight baby by 0.03 per cent, which was said to be statistically significant. In the case of PM2.5s, a much larger 10 per cent risk increase was seen.

The research also showed a continual trend of elevated low birth weight risk with higher levels of air pollution.

Prof Pless-Mulloli added: 'The particles which are affecting pregnant mothers mainly come from the burning of fossil fuels. In the past the culprit may have been coal fires, now it is primarily vehicle fumes.

'Currently in some parts of London we see around 40 units of particulate air pollution and in Newcastle it is around 20 units but going back to the 1960s we saw around 700 units of air pollution.

'While much has been done to improve air quality, this study shows we can’t be complacent as we’ve shown that clean air is really important for the health of our newborns.'

The scientists collected data on more than three million births at 14 locations in the UK, North and South America, Asia and Australia.

They concluded: 'The estimated combined associations, although relatively small, could be of major public health importance considering the ubiquitous nature of particulate air pollution exposure and therefore the potential for considerable population attributable risk, particularly given evidence of perinatal (around the time of birth) and life-long effects of LBW (low birth weight) on health.'

Dr Tony Fletcher, senior lecturer in environmental epidemiology at the London School of Hygiene and Tropical Medicine, said: 'This new study is very helpful in establishing another health impact of air pollution. Because the average effect is quite small, it needs enormous multi-country studies such as these to quantify the effect.

'The study is of excellent quality and the conclusions are clear: while the average effect on each baby is small and so should not alarm individual prospective parents, for the whole population these small risks add up across millions of people.

'Another reason for London and other large cities to force traffic-related pollution down to lower levels.'


Swapping the butter for margarine 'may be bad for your health'. U.S. scientists claim polyunsaturated fat 'doubles heart risk'

I stopped buying margarine years ago  -- mainly on taste grounds -- but also because I saw medical wisdom as dubious -- JR

For the past 50 years, we have been advised to reduce our intake of saturated animal fats, and eat more of the polyunsaturated vegetable fats found in margarine.

But now scientists in the US claim to have turned that conventional wisdom on its head, with a new analysis of a study carried out between 1966 and 1973. Some of the data had been missing for decades.

The study, conducted in Sydney, followed 458 men aged 30 to 59 who had recently had a heart attack or suffered from angina.

Half were advised to cut their animal fat consumption and replace it with safflower oil – similar to sunflower oil – and safflower oil margarine.

The results, published in the British Medical Journal, showed that those who ate more of these products were almost twice as likely to die from all causes, including heart disease.

They chose the Sydney study because it was the only randomised controlled study to look at the impact of increasing consumption of omega 6 polyunsaturated fatty acid.

Most studies of dietary interventions have involved multiple changes, but the Sydney study looked solely at omega 6.

Omega 6, the most prevalent polyunsaturated fat in most Western diets, is also known as linoleic acid.

It is found in large quantities in vegetable oils such as corn, sunflower, safflower and soybean and in margarines made from these oils.

Once in the body, it is converted into a chemical called arachidonic acid which can trigger the release of other chemicals leading to inflammation, a leading cause of a host of chronic diseases – including heart disease.

The researchers, from the National Institutes of Health in the U.S., say their findings could have ‘important implications for worldwide dietary recommendations’.

But other scientists have criticised the results, saying they did not provide enough evidence to suggest people should change their diets.

Professor Tom Sanders, of King’s College London, said the study was ‘enormously underpowered’, of ‘little relevance to diets today’ and its findings had been refuted by recent better studies.

Professor Brian Ratcliffe, of  Aberdeen University, said: ‘This paper does not provide evidence for changes to the current recommendations for a healthy diet.’

And Victoria Taylor, senior dietician at the British Heart Foundation, said: ‘Our understanding of the effect of different fats on our heart develops all the time as new research into this complex issue is published.

‘Replacing saturated fats with unsaturated alternatives is a well-known recommendation for your heart, which is based on many large and in-depth studies.

‘However, this research highlights the need for us to further understand how different unsaturated fats affect our risk of heart disease.  ‘Whichever fats you use it  is important to be sparing with them.’

Vegetable oils and margarine are supposed to help lower cholesterol and blood pressure and increase weight loss and improve overall health.  But they are some of the most chemically altered foods in our diets, and critics say they should not be promoted as healthy.


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