Air Pollution & Brain Cancer
Air Date: Week of October 3, 2003
Air pollution from diesel exhaust has been known to contribute to respiratory problems like asthma and lung cancer. Now, new research may show a link between tiny particles of pollution and brain cancer. Host Steve Curwood speaks with Dr. Keith Black, director of neurosurgery at Cedars-Sinai Medical Center.
CURWOOD: California state legislators say it’s their way or the highway when it comes to protecting school children from air pollution. Concerns over childhood asthma and lung cancer have led to the passage of a bill will block the building of new schools near major freeways and busy roads. Tiny particles from passing diesel vehicle pose some of the biggest dangers to health. Now, an emerging study may show that air pollution is not only linked to respiratory problems, but may also to brain cancer. Dr. Keith Black is heading up this study and directs neurosurgery at Cedar Sinai Medical Center. He joins me now from his Los Angeles office. Dr. Black, welcome.
BLACK: Thank you.
CURWOOD: Tell me, Doctor, what’s the best evidence to date that there may be a link between specific types of air pollution and brain cancer?
BLACK: Well, we know from animal studies that we’ve done, that when animals are exposed to toxins that we find in air pollution that they’re able to develop brain tumors. These toxins can include things that are released by diesel engines, such as ultra-fine particles that we know can readily cross the blood-brain barrier and get right into the brain. We also know that particular occupational exposure to high concentrations of diesel exhaust may result in a higher incidence of brain tumor development. Firemen, for example, that live in fire stations where the diesel engines for the fire engines are turned on. And this diesel exhaust is able to escape into the fire station, exposing firemen to very high concentrations of diesel exhaust, resulting in a higher development of brain tumors in fireman.
CURWOOD: Talk to us a bit about the blood-brain barrier. What’s its purpose and how effective is it ordinarily?
BLACK: Well, brain capillaries, or small blood vessels, are different from any other capillaries in the body, in that they essentially form a wall or a barrier. And that prevents most compounds from the blood from getting out of the blood into the brain. In fact, the main energy source for the brain, glucose, cannot get out of capillaries into the brain without being taken across by a special transport carrier in these brain capillaries. So most things that cannot be dissolved in lipids, or most water soluble molecules, will not cross this blood brain barrier. And that’s perfect as long as everything is normal and as long as the brain is healthy. But under abnormal circumstances, sometimes bad toxins can get into the brain that we don’t want to get into the brain. And it’s a very difficult barrier for us to deliver drugs and therapeutic molecules across, to treat diseases that may effect the human nervous system.
CURWOOD: Now tell me why you’re focusing on particulates. I can understand that chemicals, compounds can perhaps breach this blood-brain barrier, but why the special interest in particulates?
BLACK: Well, we know that, particularly along freeways, there’s a very high concentration of ultra-fine particles, that are released by diesel engines. And when we inhale these ultra-fine particles, they rapidly cross into our blood, and cross from blood into the brain.
CURWOOD: Now, how small are these ultra-fine particles?
BLACK: They’re extremely small. They’re in the range of what we would consider to be nanoparticles. And they’re so small, in fact, that they can rapidly cross almost any biological barrier, or any other barriers. You know you’re rolling up your windows, or your filtration system on your air conditioning unit will not filter out these particles.
CURWOOD: So what exactly is the mechanism of action here? How may air particulates, these ultra-fine particulates, cause tumors?
BLACK: What we’re speculating, at this point, is that they’re able to disrupt the molecular and genetic machinery in the cells, increasing the expression of bad genes, or cancer genes within these cells.
CURWOOD: Why start this study now? Why are you so suspicious of ultra-fine particulates?
BLACK: The unique opportunity that we have now is that we have a very well developed index of brain tumors in our population, particularly in southern California. And because of all the studies that have been done in southern California, we have very detailed analysis of our air pollution patterns. So, we can actually go address by address, zip code by zip code, and we can actually track the exposure into very detailed levels with how much time one has spent on the highway, how much time a child has spent riding the school bus, and so forth.
CURWOOD: To what extent do you think your study could revolutionize the perception of how dangerous particulates might be?
BLACK: I think that it’s easy to make the association between asthma and particulates, between lung cancer and particulates, because we’re breathing those in the lung. What we don’t understand readily is that these particulates are crossing from the lung into the blood system and they’re effecting other organs in the body. We’re focused on the development of brain tumors, but getting particulates into the brain may actually extend beyond brain cancer. We don’t know what the contribution of that may be to the development of Alzheimer’s disease, other neurological disorders, including autism and other disabilities.
CURWOOD: Dr. Keith Black is the director of neurosurgery at Cedar Sinai Medical Center. Thanks for taking this time with me today.
BLACK: Alright, well, thank you. It’s been a pleasure.
[MUSIC: Beastie Boys “Instant Death” HELLO NASTY (Capitol Records-1998)]
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