Carbon emissions are horrifying little things, by which I mean tiny little particles of high octane nightmare fuel. Totally aside from any question of global warming, there are all sorts of ways that fine particulate emissions sink into the human body through the lungs and wreak havoc from the inside out.
Are you worried yet? You should be.
Let’s Talk about Lung Cancer
So, diesel emissions have been linked to an increased risk of heart attacks in healthy adults by researchers at the University of Edinburgh (as reported by sister site Gas2). They’ve also been positively correlated with lung cancer, according to a recent study backed by the U.S. federal government (which has been handing out subsidies for fossil fuels for decades). Participating in the study were the National Cancer Institute (NCI) and the National Institute for Occupational Safety (NIOSH).
The two-part study focused on non-metal miners — focused on miners because much of the equipment in mines runs on diesel and exhaust concentrations build up within the enclosed areas, and focused on non-metal because that more or less eliminates exposure to other carcinogens such as radon, silica, and asbestos. It’s the first study to positively correlate diesel exhaust and lung cancer based on estimates of quantitative historical exposure.
The first study focused on overall mortality rates. The basic numbers it came away with were that workers with lots of diesel exposure had five times the rate of lung cancer as those with very little. The second study focused only on deaths from lung cancer, collecting detailed information on other risk factors (think smoking, employment in other high risk jobs, or a history of respiratory diseases).
The numbers came back to say that the miners had three times the risk of lung cancer overall, with heavily exposed workers showing up to five times the mortality rate. Nonsmokers deserve a special note — the more they were exposed to diesel exhaust, the more likely they were to die.
Correlation Is Not Causation
We all know that a positive correlation does not prove causation. Just because there are both more storks and more babies in the spring doesn’t mean that the storks bring the babies. So, there’s a chance that particulate emissions aren’t really causing lung cancer or heart attacks. That’s not really something I want to bet my life on. Also, if something makes you choke when you breathe it, chances are it’s really not good.
Even if cause hasn’t been strictly established, I’d still like to avoid high levels of exhaust, which one might think is possible simply by staying out of mines…. One would be completely wrong.
A number of urban locations (including Los Angeles, the Bronx, cities all over China, Mexico City, and Estarrja) all expose their residents, over a lifetime, to the same concentrations of diesel exhaust as the miners with low exposure in the NCI/NIOSH study, not to mention the millions of American and European workers exposed to diesel exhaust who don’t work in mines.
Assuming that causal relationship, it can be inferred that living in polluted cities confers a higher risk of lung cancer. That brings with it some significant ramifications for public health. Lead author of the second study mentioned above, Debra Silverman (chief of the Occupational and Environmental Branch in the Division of Cancer Epidemiology and Genetics at NCI), summarized the results as follows:
“Because such workers had at least a 50% increased lung cancer risk, our results suggest that the high air concentrations of elemental carbon reported in some urban areas may confer increased risk of lung cancer. Thus, if the diesel exhaust/lung cancer relation is causal, the public health burden of the carcinogenicity of inhaled diesel exhaust in workers and in populations of urban areas with high levels of diesel exposure may be substantial.”
Sticky, Sticky Tar.. and It’s Inside You
One of those public health ramifications is how well those fine particles coming out of diesel tailpipes stick to each other and other things, like you and your internal organs.
Diesel exhaust (and other combustion engine exhaust as well) is partially composed of these things called SOAs, or secondary organic aerosols. They’re tiny little particles formed in air. Pollutants and biogenic precursor compounds oxidize into SOAs, which then proceed to account for around half of the aerosol mass in a city environment. You may be more familiar with SOAs under the name of “smog.” You want to watch out for these, because — as we said earlier — they can screw up both your heart and your lungs.
A recent study analyzed smog with a single particle laser ablation time-of-flight mass spectrometer (or SPLAT, which is basically a really precise machine to study particle physics and chemistry with a really fun acronym). The researchers, led by air chemist Barbara Finlayson-Pitts, used α-pinene (commonly found in household cleaners and outdoor emissions) combined with nitrogen and ozone oxides to mimic smog build-up.
What Finlayson-Pitts discovered is best explained in her own words:
“They check in, and they don’t check out. They cannot escape. The material does not readily evaporate and may live longer and grow faster in total mass than previously thought. This is consistent with related studies showing that smog particles may be an extremely viscous tar.”
Did I Mention This Stuff Isn’t Just Made of Diesel Fumes?
Although the NCI/NIOSH study focused primarily on diesel, diesel isn’t the only type of engine with harmful carbon emissions. Yet another study, carried out by researchers from the Cooperative Institute for Research in Environmental Sciences (CIRES) and NOAA’s (National Oceanic and Atmospheric Administration) Earth System Research Laboratory (ESRL), went to the LA area to measure SOA concentrations.
Los Angeles was an ideal location because of the ocean on one side and mountains on the other, plus more mountains in the north — not much air circulation there. So the CIRES and ESRL researchers took the NOAA P3 research aircraft, made three weekday and three weekend flights, and measured several airborne (and ground-based) aspects of air pollution.
The researchers looked at traffic patterns — more diesel trucks on the road during the week than on weekends, with gasoline-powered vehicles remaining constant no matter what day it was (this is what traffic in Chicago is like, too, not that they came here). The expectation was that SOA levels would correspond to diesel traffic — high on weekdays, much lower on weekends.
That’s not what happened.
The SOA levels confirmed by the researchers were pretty steady every single time, leading the researchers to conclude that diesel contributes no more than 20% of SOA levels. Those supposedly less damaging gasoline cars are responsible for 80% or more of that sticky tar in the air that’s been positively linked with heart attacks and lung cancer in otherwise healthy people.
In the words of CIRES research scientist Roya Bahreini:
“The surprising result we found was that it wasn’t diesel engines that were contributing the most to the organic aerosols in LA. This was contrary to what the scientific community expected.”
Stop Procrastinating and Listen!
If the CIRES/ESRL findings are applied to the rest of the world, lowering carbon emissions from gasoline engines could significantly reduce SOA concentrations on a global scale. If you need another reason to move away from combustion engines, here it is.
We’ve heard these ideas and correlations before. Similar studies exist. But gas-powered and diesel-powered vehicles still swarm the streets, and there is no sense that I can see among the general population that these vehicles have to go. Take up cycling. Get a hybrid. Get a scooter. Walk. Buy an electric car.
Carbon emissions are killing you.
Images: Wikimedia Commons.