Interstate 405 in Los Angeles (photo: Reed Saxon, Associated Press)
It’s been decades since health concerns were first raised about the ultrafine particles (UFP) spewed out by vehicles and other combustion-producing sources, but unlike the fine particles that accompany them, it is not felt that enough is known about the pollutant to regulate it.
This might help.
A new report (pdf) published in the journal Environmental Health Perspectives found a stronger association in some cases between heart disease deaths and long-term exposure to UFPs than with fine particles, which are subject to both state and federal emissions regulations. Some particulate constituents, including copper, iron, other metals and elemental carbon (soot), were strongly associated with death from heart attacks.
“Our findings suggest that ultrafine particles may have a significant impact on public health,” lead author Dr. Bart Ostro, former chief of OEHHA’s Air Pollution Epidemiology Section, said in a press release.
Ultrafine particles are about 0.1 micron in diameter, which is one-thousandth the width of human hair. Their tiny size allows them to pass through the lungs and into the bloodstream.
A number of studies have looked at the effect of short-term exposure. In fact, there has been such a “substantial body of literature” on the subject—“their spatial and temporal distribution in ambient air, their inhalation and fate in the body, their mechanisms of toxicity, and their adverse effects in animals and in humans”—that in January 2013, the Health Effects Institute (HEI) published a report (pdf) pulling it all together.
Although scientists “expect that UFPs may have specific or enhanced toxicity relative to other particle size fractions and may contribute to effects beyond the respiratory system,” the report concluded, “the considerable body of research has not provided a definitive answer to this question.”
So the verdict is out on short-term exposure, according to HEI, which is an independent non-profit corporation jointly funded by the U.S. Environmental Protection Agency (EPA) and the worldwide motor vehicle industry.
But what about long-term exposure? It was an easy answer in 2013. “No epidemiologic studies of long-term exposures to ambient UFPs have been conducted,” the report noted.
Now, they have one to add to the next roundup of studies.