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Unregulated Nanoparticles from Diesel Engines Inhibit Lung Function

A new University of Michigan simulation shows that carbonaceous nanoparticles emitted by diesel engines and other combustion sources can get trapped in the lungs and inhibit the function of lung surfactant—a fluid that facilitates breathing.

Lung surfactant contains protein and lipid molecules. It reduces surface tension in the lungs, prevents them from collapsing and helps transport foreign particles that will ultimately be expelled from the lungs. Inhaled carbon nanoparticles, however, appear to behave differently than most foreign particles. Computer simulations indicated that they wouldn’t be expelled, but would become trapped in the surfactant, entangled with fatty lipid molecules that wrapped their “tails” around the nanoparticles and into their central cavities.

The presence of the nanoparticle can hinder the function of lung surfactant by affecting the interaction between the lipids and peptides,” said Angela Violi, assistant professor in the departments of Mechanical Engineering, Chemical Engineering and Biomedical Engineering. Violi presented her findings during an invited talk at the American Chemical Society meeting in Philadelphia.

This is believed to be the first time researchers have demonstrated how these nanoparticles can get caught in the lungs and affect the behavior of surfactant. Other studies have shown that buildup of nanoparticles in the lungs can lead to inflammation, blood clotting and changes in breathing and heart rates.

There is mounting evidence that very small particles have a greater negative impact on health than larger particles. Nanoparticles emitted by diesel engines and other combustion sources are a health concern because of both their size and the carcinogens with which they are associated. This problem is exacerbated by the fact that there is currently no effective regulatory control of these nanoparticles.

—Angela Violi

Current US and European diesel emissions regulations address particle sizes of 2.5 microns or larger (PM2.5, PM10)—up to three orders of magnitude larger than the nanoparticles Violi studies. Carbon nanoparticles make up only 0.1 to 1.5% of the total mass of particles diesel engines emit, but in terms of the number of particles, nanoparticles represent between 35% and 97% of the emissions, depending on the traffic.

The computer model Violi created to run this simulation can also predict how various combustible materials will burn, what nanoparticles will be created, how those particles will be shaped and how they could affect the lungs. This tool could be useful in predicting biofuel emissions, Violi says. “It could help us reach the goal of engineering biofuel molecules to reduce emissions,” Violi said. It’s conceivable that engineers could genetically modify plants to produce cleaner burning fuels, she said.

A related paper on this research titled “Molecular Dynamics Simulation Study of a Pulmonary Surfactant Film Interacting with a Carbonaceous Nanoparticle” will be published in the 15 Oct issue of Biophysical Journal.

Separately, a new review published in the 26 August issue of the Journal of the American College of Cardiology (JACC) highlights that unregulated ultrafine particles from tailpipe emissions may be translocated into the circulation and directly transported to the vasculature and heart where they can injure the heart and blood vessels, increase rates of hospitalization for cardiac illness, and can even cause death. Particulate pollution is categorized into three main classes: coarse particles with aerodynamic diameter (AD) 2.5 to 10 µm (PM10); fine particles (AD <2.5 µm; PM2.5), and ultrafine particles (AD <0.1 µm; UFPs). (Earlier post.)




Duuuuhhhh....surprise, surprise.....guess someone has to do research on the obvious.

Brian P

I was under the impression that gasoline engines produce more extremely fine particles than diesels do.


ejj: we've long known ultrafine PM is bad for you, what appears to be new here is the effect UF PM has on lung surfactant function.

Brian P: From the abstract:
The process of combustion is the dominant pathway through which mankind continuously injects particulate matter into the atmosphere at the present time. These combustion generated particles are present not only in a very large amount, but are produced, at the smallest scale, in the form of clusters with nanometric dimensions

Any combustion source works. Interestingly diesel (or any other fuel) is not mentioned in the abstract at all. But your point stands.


With the advent of common-rail injection, oxidation catalysts and DPFs, that may no longer be true.


With the advent of common-rail injection, oxidation catalysts and DPFs, that may no longer be true.

What do you mean, do these technologies increase or decrease the problem?

As far as I know high pressure injection decreases the amount (weight) of particles but increases the number of (ultrafine) particles. As far as I know DPF's do not filter these ultrafine particles.


It reminds me of tobacco smoking. Filters did not help. It took almost 400 years to realize it.

There is no such thing as good air pollution. All ICE machines, wood stoves & fire places pollute more or less under various conditions.

It best to avoid all sources.

Electrification (with clean electricity production) should be the common objective.


My parents knew way back in the 70s you dont raise children near freeways or industry.. granted we lived near ag and got sprayed with ddt and everything else... but we stayed away from the car exhaust.

The simple and easy solution is if you have kids stay well away from homes near freeways or bussy streets...

Frankin E. Fraitus

I drove a 1982 diesel rabbit for a while. It's exhaust would blow back into the car at traffic lights and such. I did not find the smell particularly annoying, but I felt sick after a long time driving the car. It got to the point where I hated driving it, as I equated the sick feeling to the car. It certainly affected my breathing.

Roger Pham

How about H2 FC or combustion, everone?


I'm not sure where this idea that DPFs are not effective for nanoparticles and/or ultrafines comes from, but all studies of which I'm aware show that DPFs are extremely effective across the entire particle size range. See, e.g., (from SAE paper 2007-01-112).

Some have shown that the particle numbers are reduced to below ambient (e.g., and, slides #10 and #11).

To address Brian P's point, the University of Minnesota (Kittleson) has shown that under common driving conditions, gasoline PM number emissions can equal or exceed uncontrolled diesel PM number emissions, only they're generally much smaller (and thus have little mass).

Diesel PM is being addressed by filters (DPF). Now the question becomes, what's being done about PM from gas engines?

Roger Pham

"What's being done about PM from gasoline engines?"

Let' consider the following,
"Diesel-powered vehicles, as expected, were often a major source of high UFP count concentrations, especially when being directly followed. However, gasoline-powered vehicles were also often observed to produce comparably high UFP counts, particularly when the vehicles were older; when vehicles were accelerating hard or from a standing start, such as after waiting at a stop light; and when vehicles were driven and/or accelerated at high speeds (Figure 8A). Because of the ubiquitous nature of gasoline-powered vehicles and the frequency of such types of driving, they may be the predominate source of in-vehicle, roadway, and near-roadway UFP concentrations." See:

The answer is obvious: More HEV's, smaller and newer cars, and drive more conservatively, use bikes, or mass transit, or reduce total driving miles.



Thanks for the info & link.


@ Anne - you're welcome. Glad you found it useful.

@ Roger - thanks for that reference. It actually supports my point that diesel engines aren't the only source of ambient ultrafine PM.

It seems every time a discussion comes up regarding PM, and air pollution in general, all fingers point to diesel as the culprit. In reality, diesel is becoming less and less a factor with the use of DPF (which in effect have been required on all new on-road diesel vehicles since January 2007 in the U.S.) and other emission controls.

Your suggestions are all fine, but the fact remains that gasoline engines prevail in light-duty vehicles and will likely become a larger and larger source of ultrafine PM. In my opinion, PM should be regulated by particle number in addition to, if not in lieu of, particle mass from all PM source categories.

Furthermore, car manufacturers have indicated that they will pursue small turbo DI gas engines in the near future, which have been shown to have even higher PM emissions (including UFP) than conventional gas engines.

Again, what's going to be done about UFP from gasoline engines?


OK, we are in agreement. Air pollution is bad.
No paticulate emissions are good.
Now what? Wave? Wind? Solar?
Try driving from Chicago to New York on wave, wind or solar energy.



You could use the Swiss e-taxis vehicle or the new Fosh Automotive e-vehicle in the near future.

Roger Pham

@Carl and Fuego,
The answer is Hydrogen and BEV. Wave, Wind and Solar can all be converted to hydrogen and electricity to power our energy future. No carbon, no UFP. This is one of the best argument for hydrogen and BEV.

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