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Diane Bailey’s Blog

Diesel Truck Pollution: The Truth is Lost in the Fumes

Diane Bailey

Posted April 24, 2014

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TruckPollution_UNECE.jpgA couple things about diesel truck pollution: there’s still a lot of it in California, truck drivers are suffering from it, and most truck owners oppose rolling back the statewide truck clean-up rule.  These facts have been obscured by all the fumes emanating from a tiny but vocal minority of trucktivists who want to do away with the Air Resources Board measure curbing diesel pollution from trucksTomorrow, ARB will consider allowing some additional delays to their statewide diesel truck and bus rule adopted six years ago.

The diesel truck rule was already delayed in 2010 in response to the recession, but it remains a pillar of public health, cutting toxic diesel soot from the state’s largest source by 80 percent.  When the rule is fully implemented, a total of 3,500 premature deaths will have been avoided, along with relief to thousands of families in high truck traffic areas, who are suffering from asthma rates that are twice as high as other areas.

While we’ve seen a lot of improvement in air quality over the past decade with many diesel clean-up regulations phasing in, thousands of polluting trucks remain on the road.  Diesel trucks are still the largest source of nitrogen oxide pollution in California, which contributes to smog and soot, and they emit more fine particulate soot directly than all of the cars on the road.  

The drivers of these trucks are on the front lines of exposure to diesel soot.  A 2007 NRDC study placing air monitors in the cabs of trucks, showed that drivers are exposed to increased diesel soot and health risks of roughly four times the average levels in urban areas.  While many drivers may feel fine in the short term, their lung and heart health is impacted in the long run, potentially leading to debilitating illnesses and shortening their lives.  (See this summary of the health impacts associated with diesel soot and fine particulate pollution)diesel_smokingtruck.jpg

We often talk about safeguarding the communities most impacted by diesel pollution. This remains a priority, but we need to recognize the drivers as part of those communities.   Cleaning up tailpipe emissions from trucks shouldn’t pit drivers against residents.  In fact, the vast majority of truck owners in California – at least 85 percent – are estimated to be in compliance with the truck rule. These owners have already made investments to clean up over 140,000 trucks and would be at an unfair disadvantage if the rule was weakened. This is why the California Trucking Association, which represents 2,000 companies, strongly opposes any roll backs to the rule. 

Various studies have shown key pollutants cut in half in recent years in some of the most polluted areas of the state (see here for example). While we celebrate these improvements, we need to stay on track to eliminate diesel pollution as quickly as possible, given the terrible health toll that it takes.  Our work is only halfway done.  If a cigarette was cut in half, smoking it would remain harmful to your health.   ARB should continue working to clear all the smoke, including diesel smoke, by moving forward with a strong diesel truck rule until every last tailpipe is cleaned up.

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Allen SchaefferApr 24 2014 10:07 AM

Transitioning California to clean diesel technology has been a success story and one that will and must continue.

While this issue may be labeled as controversial, it is not an issue of technology availability nor an options issue; there are plenty of both.

For existing engines, there are well over 40 level 3 verified and effective retrofit device solutions available for trucks.

At the same time, the most recent registration data shows that more CA truckers are embracing the new generation of clean diesel technology than ever before – as of the end of 2013, 25 percent of all CA registered trucks Class 3-8 are 2007 and newer with about 10 percent 2010 and newer. The new engines deliver not only near-zero emissions, but also real world fuel savings and other advantages. These should be significant motivators for truck fleets.

This year for the first time, California may reach clean air attainment status for particulate emissions for the federal clean air standard. As stated by CARB, this progress is largely due to the transformation to clean diesel technology in California.

Everyone in the state has an investment in clean diesel technology – from the truckers and manufacturers to the citizens and communities that depend on the delivery of goods and services, and the Air Resources Board itself.

Michael BerndtsonApr 24 2014 12:04 PM

Here's an example of when public/private work groups included schools, diesel engine manufacturers, regulators, oil refiners, enviro NGOs, diesel engine repair, and academics to git r' done:

"Reducing Diesel Emissions in the Denver Region: Report to the Regional Air Quality Council and the Air Quality Control Commission Diesel Stakeholders Work Group - May 2002"

Not finished, but at least taken seriously. Then again, this was before Colorado's fracking boom. So clean air may have taken a backseat. What's more important, hauling frackwater blowback in a vac truck running rich or clean air? [that was satire]

Gerald QuindryApr 25 2014 10:03 AM

I am flummoxed as to why there is not a bigger push to natural gas fueled trucks.

Stan ScobieApr 25 2014 05:18 PM

Two things:

1. You say: "The drivers of these trucks are on the front lines of exposure to diesel soot. A 2007 NRDC study placing air monitors in the cabs of trucks, showed that drivers are exposed to increased diesel soot and health risks of roughly four times the average levels in urban areas.

When I drive the the interstates between upstate NY and NJ in my low emission Prius, I get plenty of truck exhaust from the plenty of trucks on these roads.

I share your concern for the truckers; I would hope they and their masters would show concern for my health.

2. As far as natural gas fueled vehicles, CA folks did an extensive analysis several years ago and concluded there was no substantive difference between "clean" diesel and natural gas fueled vehicles. Europe has had clean diesel for years.
The push for natural gas fueled vehicles is part of a massive effort to increase demand for natural gas by creating the infrastructure that will serve to addict us all. GM did the same sort of thing when they went up against electric short-haul passenger trains and again when they promoted lead in gasoline.

Stan Scobie, Binghamton, NY

Alan KandelApr 26 2014 02:35 PM

I am curious how the improved diesel truck engines (2007 and newer models) compare diesel-exhaust-wise to diesel locomotives - those in the Tier 4 category - and which are more effective at reducing harmful diesel particulate matter (PM) exhaust.

I also read the article by Christine Cosgrove (linked from this page in the last paragraph above) and in the Cosgrove article, particulate matter and soot are listed separately. I had been under the impression - as I am sure others have too - these were one and the same. Apparently, this is not the case.

And in the Cosgrove article as well, it is mentioned that black smoke, otherwise known as black carbon, is one of particulate matter's major components, PM emissions also containing in them emissions of mineral ash and lubricating oil.

So there is much more to particulate matter (PM) emissions than what I was previously aware.

Diane BaileyApr 28 2014 01:35 AM

Last Friday, the Air Resources Board adopted amendments to the diesel truck and bus rule giving more time to small business and truck owners in rural areas to clean-up. See:,0,3351398.story?track=rss#axzz2zt5EKNLB

I appreciate all the good comments here. Allen Schaefer at the Diesel Technology Forum rightly points out that the clean-up of diesel engines over the past decade is a success story. There has been remarkable progress in engine and after-treatment technologies and we hope that progress continues to transition from fossil fuels to zero- and near-zero emission technology. Several people mention natural gas engines, so it’s worth pointing out that natural gas historically has been much cleaner than diesel, but with strict new standards in place, it’s uncertain whether that will continue. Both natural gas and diesel are fossil fuels, except in the rare instances where they’re derived from biogas (e.g. livestock waste) or bio-oil (e.g. soy).

The technology used by diesel trucks to meet tier 2 standards is similar to what is used by off-road equipment meeting tier 4 standards, including diesel particulate filters (DPFs) for PM control and selective catalytic reduction (SCR) for NOx control. We hope this is the case for locomotives meeting tier 4 standards as well, though it’s possible some may rely on engine adjustments and oxidation catalysts to meet PM standards (instead of using a DPF).

Stan wisely points out that we all are exposed to diesel pollution while driving or riding on the freeway, no matter how clean the vehicle we are riding in is. In answer to Alan K.’s question about PM vs. diesel, the diesel soot we breathe in from the freeway contains all of the things you mention – black carbon, ash including metals, plus other semi-volatile toxic constituents like polycyclic aromatic hydrocarbons. Particulate matter is a broader category of pollutants in solid form including diesel soot and many other types of particles including minerals but more typically being formed by combustion, such as wood smoke.

It’s great to see other regions outside of CA taking additional steps to clean up diesel pollution. I wasn’t aware of the effort in Denver – thank you Michael for pointing that out. One noteworthy statement from that 2002 Denver report on cleaning up diesel pollution: “…significant opportunities exist to introduce new technology into the in-use fleet and take advantage of these emission reduction gains sooner. (p. I-3) We agree. We’ve come a long way cleaning up diesel pollution in the U.S., but we still have quite a ways to go. As one Oakland resident put it at the ARB hearing last week (and is quoted in Tony Barboza’s LA Times article referred to above):
"We understand that cleaning up trucks is expensive, but somebody has to pay," said Pamela Tapia, a community college student from Oakland with asthma. "Right now we're paying with our health and that's not right."

Alan KandelApr 28 2014 10:25 AM

So, let me see if I have this correct: the diesel soot contains gaseous elements mostly and the particulate matter consists of those plus solid matter? So, in this sense the broad category of particulate matter pollution is more inclusive than that of diesel soot alone.

Moreover, thank you Diane for taking time to address the point I raised regarding diesel engine efficiencies.

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