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Speaker 1: Welcome to brain Stuff from how Stuff Works. Hey, brain Stuff,

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Speaker 1: Lauren Vogel bomb here. When we think of air pollution,

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Speaker 1: we usually think of black clouds pouring out of smoke

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Speaker 1: stacks or the unsightly brown haze that hangs over many

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Speaker 1: of the world's cities. But in recent years, scientists have

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Speaker 1: found increasing evidence of health risks from a part of

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Speaker 1: air pollution that we don't see and that isn't yet

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Speaker 1: regulated under federal air quality standards. In addition to visible emissions,

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Speaker 1: the burning of fossil fuels and other types of combustions

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Speaker 1: create vast quantities of ultrafying particles somewhere around a thousand

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Speaker 1: of the width of a human hair, that we inhale

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Speaker 1: without ever realizing it. We spoke with Bart Astro, former

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Speaker 1: chief of Air Pollution Epidemiology for the California Environmental Protection

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Speaker 1: Agency and currently a researcher at University of California Davis.

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Speaker 1: He said that ultrafined particles come from an array of sources.

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Speaker 1: They're emitted from vehicles, especially ones that burned diesel fuel,

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Speaker 1: as well as smaller g selene burning engines such as

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Speaker 1: the ones in lawnmowers and leafblowers, but other types of

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Speaker 1: burning wood, fires, burning leaves, and secondhand smoke from cigarettes,

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Speaker 1: for example, also produce ultrafine particles. So does cooking meat

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Speaker 1: on the stove in your kitchen. Nevertheless, it's a challenge

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Speaker 1: to figure out the extent of our exposure to ultrafine particles.

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Speaker 1: Because the particles are so small and so transient, they

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Speaker 1: quickly disperse or else coagulate into bigger particles. They're a

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Speaker 1: type of air pollution that is especially difficult to measure.

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Speaker 1: Astro said. Ultrafine particles are very high in concentration next

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Speaker 1: to roadways, for example, but if you go three hundred

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Speaker 1: to five hundred yards away, that's about two hundred and

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Speaker 1: fifty to four fifty the ultrafines go down to almost

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Speaker 1: background levels. In recent years, scientists at University of California,

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Speaker 1: Davis have developed sophisticated modeling methods that combine sensing data

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Speaker 1: with knowledge about how chemical processes and meteorological conditions affect

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Speaker 1: these particles. That's allowed them to predict concentrations over several years,

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Speaker 1: which in turn makes it easier to study the particles

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Speaker 1: effects on human health. Austro was the lead author on

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Speaker 1: a study published in twenty fifteen The combined such modeling

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Speaker 1: with health data on one hundred thousand middle aged female

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Speaker 1: teachers and administrators that were recruited from the State Teachers

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Speaker 1: Retirement System. It found an association between ultrafined particles and

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Speaker 1: death from heart disease Since then. Seventeen study also found

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Speaker 1: that long term exposure to ultrafine particles around highways was

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Speaker 1: associated with cardiovascular diseases and hypertension, and eighteen study in

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Speaker 1: the journal Environmental Pollution suggests that simply moving a bus

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Speaker 1: stop forty to fifty away from an intersection that's about

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Speaker 1: a hundred and thirty and fifty feet can substantially reduce

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Speaker 1: transit users exposure to high levels of ultrafined particles. It

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Speaker 1: may seem strange that something so small could be so dangerous,

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Speaker 1: but because of their size, ultrafine particles have an easier

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Speaker 1: time getting into lung tissue and causing inflammation. Research has

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Speaker 1: found that even a brief amount of ultrafine particle exposure

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Speaker 1: can increase the allergic inflammation that makes asthma worse. But

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Speaker 1: that's not the only worry. Ultrafine particles are so tiny

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Speaker 1: that they can penetrate the blood brain barrier and be

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Speaker 1: absorbed in into brain tissue. Recent research suggests a possible

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Speaker 1: link between the tiny particles and Alzheimer's disease and other

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Speaker 1: forms of dementia. Scientists also have found that mice exposed

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Speaker 1: to ultrafine particles early in life had changes in their

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Speaker 1: brains that bore resemblance to those set in humans with

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Speaker 1: autism and schizophrenia. Despite all that, federal air pollution standards

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Speaker 1: don't yet set limits for ultrafined particles due to the

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Speaker 1: developing state of the scientific evidence about their health effects

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Speaker 1: and the current limitations on monitoring technology, but Ostro says

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Speaker 1: there are some measures that people can take to protect

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Speaker 1: themselves from ultrafine particles. If you have pre existing conditions

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Speaker 1: such as cardiovascular or respiratory diseases, it's a good idea,

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Speaker 1: for example, to limit your exposure to emissions such as

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Speaker 1: diesel fumes, car exhaust, and any sort of burning biomass.

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Speaker 1: And even if you're healthy, you'll probably want to avoid

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Speaker 1: such exposure as well, which means shifting your running routes

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Speaker 1: away from major roadways is a really good idea. Today's

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Speaker 1: episode was written by Patrick Jake Tiger and produced by

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Speaker 1: Tristan McNeil. And Tyler Clang. For more on this and

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Speaker 1: other topics. To help you breathe a little easier, visit

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Speaker 1: our home planet has stuff works dot Com