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Are we polluting children's brains?

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  • Are we polluting children's brains?

    There is a growing debate about the harmful effects of airborne neurotoxins – just how good is the science?

    Let’s do a reality check. There is not a lot of evidence that we have a toxic brain disaster on our doorstep. For many decades, with each new generation we've seen a significant rise in the average IQ of the population. It’s not at all clear why, but our kids are truly smarter than us, and it isn’t just about better knowledge through wider education.

    Second, there are few, if any, signs that we’re in the middle of an autism or Attention Deficit Hyperactivity Disorder (ADHD) epidemic. The only epidemic is in diagnosis, but that’s a topic for a future column. When it comes to dementia there is emerging evidence from Scandinavia that the incidence is topping out, suggesting that brain health is improving in lockstep with our general health.

    Having said that, statistics can hide gaps and it doesn’t mean that we can stop worrying about potential risks from exposure to possibly neurotoxic pollutants. The most important neurotoxins are still tobacco smoke, alcohol, lead and mercury, all of which affect developing brains. In the early 1980s, Australian research known as the Port Pirie Cohort study showed significant developmental problems arising for children living close to a lead smelter. Children’s health also was a major driver for lead-free petrol. But what about pollution from traffic exhausts and coal-burning?
    A fascinating study on babies born near a coal-fired power station in Tongliang County, China, was published this March in PLoS One by researchers at Columbia University. Some toxins found in coal emissions are polycyclic aromatic hydrocarbons (PAH), which tend to form damaging chemical bonds with DNA known as adducts.

    Using cord blood from the newborns, the researchers measured levels of PAH adducts and levels of the protein "brain-derived neurotrophic factor" (BDNF), which serves as a marker of developing brains. The children’s development was assessed at the age of two. These measures were carried out on babies born in 2002 and 2005, before and after the power station was shut down. Cord blood of babies born after the shutdown showed lower levels of the adducts, higher levels of BDNF, and the children scored higher in developmental tests.

    Traffic exhaust also contains PAH, but the most concerning pollutants are very fine particles that are thought to find their way into our bloodstreams via the lungs. The evidence that small-particulate air pollution from traffic exhaust is bad for adult brains is reasonably strong with links to stroke, possibly through inflammatory effects on arteries. And it’s this idea of inflammation, especially in developing brains, that has people worried about links to autism spectrum disorder (ASD).

    Bottom line: ASD now joins the club of diseases, including stroke, heart disease and respiratory problems, that are associated with exposure to tiny particles in the air we breathe.
    Is it 100% proven? Not yet. But it is nevertheless worrying and means that efforts to reduce traffic-related pollution should be maintained if not enhanced.

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    Last edited by Higenindo; 02-10-15, 10:10.