Nanoparticles on the brain?

John Balbus, M.D., M.P.H., is Chief Health Scientist.

It’s been a worry for engineered nanoparticles. Now, a new study from the Harvard School of Public Health (Suglia et al., 2008) is the first to suggest that particulate air pollution not only damages the lungs and heart, but also may damage the developing brain.

Researchers measured cognitive function in over 200 children in Boston in relation to their residential exposure to traffic-related air pollution by measuring airborne carbon black particles. They found the IQ-lowering effect of higher exposure is comparable to a pregnant mother smoking 10 cigarettes a day or moderate lead exposure.

It’s important to note that carbon black is only used as an indicator for traffic-related particle pollution in this study, and the authors stress that it should not be concluded that pure carbon black is the causative agent here. The actual particles inhaled are likely to be contaminated by heavy metals and other toxins, and these may well be the culprits or at least greatly contribute to the actual damage to brain tissues. But it does suggest that some of the ultrafine fraction of air pollution finds its way into the brain and causes harm.

This study may not be making headlines in the nanoworld, but the nanoworld should be taking notice.

The authors hypothesize that the combustion particles make their way via the olfactory nerves from the children’s nasal passages directly into the children’s brains, as has been demonstrated for a variety of engineered nanoparticles in animal models (e.g., Oberdorster et al., 2004; Elder et al., 2006). Once there, the particles, including attached contaminants, may cause oxidative stress, ultimately leading to inflammation and cellular malfunction and/or damage. The study did control for potentially confounding factors like maternal cigarette smoking, lead levels in the children’s blood, mother’s educational level, low birth weight, and other factors.

This study should give pause to those who are making nanoparticles containing known neurotoxins, such as lead and manganese. And with growing understanding of the linkages between developmental and degenerative diseases of the brain, there’s reason to think that processes that lead to IQ loss in growing kids can impair brain functioning in aging adults. One more reason to avoid inhalation of nanoparticles, especially those with known capacity to cause oxidative stress.

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  1. Tim
    Posted February 21, 2008 at 5:46 pm | Permalink

    Please clarify what these comments so far have to do with nano technology. Are pollution particles really nano particles? I thought they were in the realm of ordinary gross particles. The topic is serious and most concerning. But is it nano?

    I appreciate NRDC.

  2. Posted February 22, 2008 at 1:45 pm | Permalink

    Thanks for your question, Tim.

    I posted this because a significant fraction of traffic-related carbon black pollution is in the form of ultrafine particles, or particles less than 100 nanometers. So that would be in the same size range of engineered nanoparticles. You’re right, not all of the traffic-related particles involved would be in the “nano” range, but the ones most likely to affect the brain probably would be.

    The authors of this study themselves refer repeatedly to animal studies of engineered nanoparticles to demonstrate the plausibility of transport of inhaled carbon black particles from the nasal passages to the brain. And a study published last fall in Environmental Health Perspectives attracted a lot of attention to the possibility of neurotoxicity from nanoparticles.

    I’m not at all trying to say this proves engineered carbon nanoparticles will display similar neurotoxicity, but this study, along with some other recent research (see reference below) certainly raises questions about the safety of brain deposition of nanoparticles.

    Reference: Sharma HS, Sharma A. Nanoparticles aggravate heat stress induced cognitive deficits, blood-brain barrier disruption, edema formation and brain pathology. Prog Brain Res. 2007;162:245-73.

  3. Hugo
    Posted April 27, 2009 at 8:34 pm | Permalink

    Hi my real name is not Hugo, currently I am being suppressed from publishing my results , but I can tell you that nanoparticles that cross the stratum corneum from sunscreens will definitely stress the cells, I have monitored this in vivo and is real concerning. The oxidative balance of the cells are shifted quite significantly even after 3 days post application. So if nanoparticles small enough to enter the blood stream via inhalation no doubt in my mind that some will end up in brain tissue along with liver lung and other vital organs.