[Due to the increasing size of the archives, each topic page now contains only the prior 365 days of content. Access to older stories is now solely through the Monthly Archive pages or the site search function.]
Study finds engines emit exhaust nanoparticles even when not fueled during engine braking
January 19, 2014
A new study finds that as much as 20–30% of the number of vehicle engine exhaust particles larger than 3 nm may be formed during engine braking conditions—i.e., during decelerations and downhill driving while the engine is not fueled. However, the authors note, these particles have not been taken into account in emission regulations and in the assessment of associated health risks.
The study by researchers in Finland and Greece, published in the ACS journal Environmental Science & Technology, suggests that both the characteristics of these particles and the mechanism by which they form seem to differ significantly from those of soot and nucleation particles. The study also indicates that the particles were non-volatile, formed before the catalyst, and originating from engine oil. Results thus indicate that the emissions of engine braking particles can be reduced using exhaust particle filtration systems.
Researchers identify new nitrated PAH compounds from combustion that are hundreds of times more mutagenic than parent PAHs
January 06, 2014
A team led by researchers at Oregon State University has discovered novel nitrated polycyclic aromatic hydrocarbon (NPAH) compounds produced by combustion sources or formed in the atmosphere that are hundreds of times more mutagenic than their parent PAHs, which are known carcinogens. The findings were published in the ACS journal Environmental Science and Technology.
These new compounds were not previously known to exist, and raise additional concerns about the health impacts of heavily-polluted urban air or dietary exposure. It has not yet been determined in what level the new compounds might be present, and no health standards now exist for them.
Analysis finds air-quality justification for CNG vehicle conversion in developing cities, despite negative climate impact
December 03, 2013
|Impact pathway approach for modeling policy interventions in (a) air quality and (b) climate impacts. Credit: ACS, Zia and Tanzila. Click to enlarge.|
An analysis by a team in Bangladesh found large air quality and associated health benefits accruing to the residents of Dhaka (the capital of Bangladesh) as a result of the rapid conversion of the motor vehicle fleet to CNG. Around 2,045 avoided premature deaths in greater Dhaka can be attributed to air quality improvements from the CNG conversion policy in 2010, resulting in a saving of around US$400 million, they found.
However, CNG conversion was apparently detrimental from a climate change perspective, as CH4 emissions increased. (There is some uncertainty over the impact of ultrafine particulates.) As the greenhouse gas impacts (costs or benefits) are much smaller than the health benefits, the conversion of petroleum vehicles to CNG can be justified on the basis of local air pollution benefits alone, they concluded. Their paper is published in the ACS journal Environmental Science & Technology.
Study estimates 6% of lung cancer deaths in US and UK attributable to diesel exhaust
November 28, 2013
In 2012, the International Agency for Research on Cancer (IARC), which is part of the World Health Organization (WHO), classified diesel engine exhaust (DEE) as carcinogenic to humans (Group 1). (Earlier post.)
Now, a study by researchers from the Netherlands, the US, and France estimates that approximately 6% of annual lung cancer deaths in the US and UK—combining both environmental and occupational exposures—may be due to DEE exposure. This translates to about 9,000 annual lung cancer deaths in the US and about 2,000 annual lung cancer deaths in the UK that may be attributable to DEE.
UC Berkeley study quantifies LD gasoline on-road emissions
November 27, 2013
Based on on-road measurements in their study, a team from the University of California Berkeley has estimated that, as of 2010, light-duty (LD) gasoline vehicles were responsible for 85% of CO; 18% of NOx; 18% of organic aerosol (OA); and 6% of black carbon (BC) emissions from on-road motor vehicles in the United States. Correspondingly, the study, reported in the ACS journal Environmental Science & Technology, also concluded that, as of 2010, diesel engines were the dominant on-road source of BC, OA, and NOx.
The researchers measured vehicle emissions of NOx, CO, fine particulate matter (PM2.5), OA and BC in bore 2 of the Caldecott tunnel in the San Francisco Bay Area. In bore 2, light-duty (LD) vehicles accounted for more than 99% of total traffic; heavy-duty trucks were not allowed.
Study finds biodiesel use in HD trucks in Canada will result in very minimal changes in air quality and health benefits
November 07, 2013
Results of a study by a team from Health Canada and Environment Canada suggest that the use of B5 and B20 biodiesel fuel blends (5% and 20% biodiesel, respectively) compared to ULSD in on-road heavy-duty diesels in Canada will result in very minimal changes in air quality and health benefits/costs across Canada, and that these were likely to diminish over time.
Health Canada is the Canadian Federal department responsible for helping Canadians maintain and improve their health; Environment Canada is the Federal agency tasked with, among other things, protecting the environment. An open-access paper on the study has been accepted for publication in the ACS journal Environmental Science & Technology.
ICCT report finds global implementation of advanced emissions and fuel-quality regs could cut early deaths from vehicle emissions by 75% in 2030
November 06, 2013
|Global trends in vehicle-kilometers traveled (VKT) and early deaths from vehicle-related fine particle exposure (2000–2030). Chambliss et al. Click to enlarge.|
Although many countries have adopted emission control regulations patterned on the European regulations, the significant majority of these have not implemented the latest and most stringent Euro 6/VI stage. A study by a team at the the International Council on Clean Transportation (ICCT) finds that if that lag persists and present trends in vehicle activity continue, early deaths from vehicle-related PM2.5 exposure in urban areas will increase 50% by 2030, compared to 2013.
Conversely, the report finds, if all countries were to follow an accelerated roadmap to Euro 6/VI-level regulations, in tandem with fuel-quality regulations limiting sulfur content to 10 to 15 parts per million (ppm), early deaths globally from road vehicle emissions would fall by 75% (200,000) in the year 2030, representing a cumulative savings of 25 million additional years of life.
UC Irvine study finds organic constituents of UFP play important role in heart disease; suggestions for more effective emission control
October 12, 2013
|Particle scale. Inset: 4 polydisperse modes of traffic-related ambient particulate matter span approximately 4 orders of magnitude from below 1 nm to above 10 μm. Source: Kleinman presentation. Click to enlarge.|
Results of a study funded and released by the California Air Resources Board (ARB) suggest that the organic constituents of ultrafine PM (UFP, particles ≤ 0.18 μm aerodynamic diameter) resulting from internal-combustion engine exhaust and from chemical reactions in the air play an important role in the progression of heart disease, the leading cause of death in the US. The findings thus suggest a direction for mor effective emission control measures—i.e., technology for the removal of the organic constituents as well as the reduction of the number of particles.
Led by Dr. Michael T. Kleinman of the University of California Irvine, the new study used a novel approach to determine whether or not the toxicity of UFP particles depends on the concentration and composition of semi-volatile and non-volatile fractions of the PM.
Study finds biodiesel blend reduces total particle mass in emissions but may have greater adverse health effect per mass than diesel
October 10, 2013
Findings from a study by researchers from the Department of Medicine and the School of Engineering at the University of Vermont suggest that the addition of biodiesel to diesel fuels will reduce the total particle mass of PM emissions—but that the biodiesel blend particles may contribute to greater biological effects per mass than B0, leading to potentially greater health risks.
As reported in a paper published in the ACS journal Environmental Science & Technology, the team first characterized exhaust particles produced by combustion of pure petrodiesel (B0) and B20 (20% soy biodiesel/ 80% B0) fuels using the same engine and running conditions, and then conducted experiments in two human cell lines representing bronchial epithelial cells and macrophages as well as in female mice. (Studies in cells alone do not necessarily reflect the integrated response of a whole animal, they noted.)
Italian study finds raised levels of PM10, even below current Euro limits, associated with increased acute cardiac events
October 09, 2013
Results of a study by a research team from Brescia and Parma, Italy, to be presented at the Acute Cardiac Care Congress 2013 by Dr. Savina Nodari from Spedali Civili Hospital of Brescia, support the hypothesis that raised levels of PM10—even below the current limits set by the European Environmental Protection Agency—are associated with increased admission rates for acute cardiac events, especially in males, older patients and those with previous cardiovascular hospitalizations.
The study evaluated the rate of hospitalizations for acute coronary syndrome (ACS); acute heart failure (AHF); malignant ventricular arrhythmias (MVA); and atrial fibrillation (AF) and the average daily concentrations of PM10 in Brescia over the period 2004-2007. The associations between average levels of PM10 and daily hospitalization for acute cardiovascular (CV) events were analyzed by a generalized linear model.
USC researchers find car ventilation setting critical to in-cabin exposure to particulate pollutants; new model for aiding exposure assessments
September 15, 2013
|In-vehicle-to-outside (I/O) ratios for four pollutants under different ventilation settings. Credit: ACS, Hudda and Fruin (2013). Click to enlarge.|
Researchers at USC have found that using recirculation rather than outside air ventilation in a car can effectively reduce in-cabin exposure to on-road particle pollution. In a study published in the ACS journal Environmental Science & Technology, they also report that in addition to the benefits of recirculation settings, exposures are lower in newer cars; at slower speeds; and on arterial roads, where pollutant concentrations are lower than on freeways.
Scott Fruin, assistant professor of preventive medicine, and Neelakshi Hudda, research associate in environmental health, both of the Keck School of Medicine of USC, performed a systematic study of in-vehicle exposure to include a full range of car types and operating conditions, as well as all types of particulate pollution. According to the researchers, concentrations of particle pollutants on freeways are often five to 10 times higher than elsewhere.
Researchers identify new pathways in low-temp oxidation of hydrocarbons; important to fuel combustion, atmospheric chemistry and biochemistry
September 05, 2013
|The diagram illustrates the newly-described reaction that transforms molecules of ketohydroperoxide into acids and carbonyl molecules, after going through intermediate stages. Credit: ACS, Jalan et al. Click to enlarge.|
Researchers at MIT, with colleagues at the University of Minnesota, have provided evidence and theoretical rate coefficients for new pathways in the low-temperature oxidation of hydrocarbons. Their paper is published in the Journal of the American Chemical Society.
The newly explained reaction—the basic outlines of which had been first hypothesized by Korcek and co-workers more than 30 years ago but the workings of which had never been understood in detail—is an important part of atmospheric reactions that lead to the formation of climate-affecting aerosols; biochemical reactions that may be important for human physiology; and combustion reactions in engines. The new study provides theoretical confirmation of Korcek’s hypothesis that ketohydroperoxide molecules (KHPs) are precursors to carboxylic acid formation.
MIT study says combustion emissions cause ~200,000 premature deaths/year in US; vehicles and power generation top sources
August 29, 2013
Researchers from MIT’s Laboratory for Aviation and the Environment have concluded that ground-level PM2.5 emissions from combustion sources such as industrial smokestacks, vehicle tailpipes, marine and rail operations, and commercial and residential heating throughout the United States cause about 200,000 (90% CI: 90,000–362,000) premature deaths each year, with another 10,000 (90% CI: −1,000 to 21,000) deaths due to changes in ozone concentrations.
Emissions from road transportation are the most significant contributor, causing ∼53,000 (90% CI: 24,000–95,000) PM2.5-related premature deaths and ∼5,000 (90% CI: −900 to 11,000) ozone-related early deaths per year. Power generation follows closely, causing ∼52,000 (90% CI: 23,000–94,000) PM2.5-related and ∼2,000 (90% CI: −300 to 4,000) ozone-related premature mortalities per year. Industrial emissions contribute to ∼41,000 (90% CI: 18,000–74,000) early deaths from PM2.5 and ∼2000 (90% CI: 0–4,000) early deaths from ozone, according to the study.
Environment Canada study finds vehicle exhaust a significant source of isocyanic acid; suggests consideration of new emission standard
July 12, 2013
Researchers at Environment Canada have found that vehicle exhaust is a significant source of isocyanic acid (HNCO), a toxic gaseous acid that is a product of various forms of combustion and a potential health concern. HNCO and its aqueous anion isocyanate (CNO−) have been linked—at exposure levels as low as 1 ppbv (parts-per-billion by volume)—to health issues such as atherosclerosis, cataracts, and rheumatoid arthritis (Roberts 2011).
In a paper published in the ACS journal Environmental Science & Technology, the team found that emission factors for HNCO ranged from 0.69 to 3.96 mg kgfuel–1 and were significantly higher than previous biomass burning emission estimates. Canada-wide, up to 770 tonnes of HNCO may be emitted annually from on-road vehicles, they concluded—likely representing the dominant source of exposure in urban areas.
ARB researchers evaluate in-use heavy-duty NOx aftertreatment systems, find elevated levels during certain lower-temperature operations
July 09, 2013
A team from the California Air Resources Board (ARB) reports on their evaluation of the in-use emissions performance of four different heavy-duty diesel engines certified to the MY 2010 or interim MY 2010 NOx standards over a wide range of driving conditions in California in a paper published in the ACS journal Environmental Science & Technology.
One of the trucks was equipped with exhaust gas recirculation (EGR); three were equipped with EGR and a selective catalytic reduction (SCR) device. The results indicated that brake-specific NOx emissions for the truck equipped only with an EGR were independent of the driving conditions—and exceeded the certification value over each segment of the entire test route. Results also showed that for typical highway driving conditions, the SCR technology is proving to be effective in controlling NOx emissions. However, they also found that under operations where the SCR systems do not reach minimum operating temperature—e.g., cold starts and some low-load/slow-speed driving conditions—NOx emissions are still elevated.
Abt life-cycle analysis of different Li-ion chemistries for PHEVs and EVs identifies opportunities for improving environmental profile of batteries
June 30, 2013
|Generic process flow diagram for lithium-ion batteries for vehicles (color coded to present LCI data sources). Source: “Application of LCA to Nanoscale Technology”. Click to enlarge.|
A recent Abt Associates, Inc. life-cycle study of three Li-ion battery chemistries for plug-in hybrid (PHEV) and battery-electric (BEV) vehicles generated a number of findings and identified opportunities for improving the environmental profile of Li-ion batteries for use in plug-in and electric vehicles.
The study, carried out through a partnership with EPA, the US Department of Energy, the Li-ion battery industry, and academicians, was the first life-cycle assessment to bring together and to use data directly provided by Li-ion battery suppliers, manufacturers, and recyclers. It assessed three currently manufactured Li-ion battery technologies for EVs and two for a PHEV with a 40-mile all-electric range: lithium-manganese oxide (LiMnO2); lithium-nickel-cobalt-manganese-oxide (LiNi0.4Co0.2Mn0.4O2, Li-NCM); and lithium-iron phosphate (LiFePO4). In addition, a single-walled carbon nanotube (SWCNT) anode technology for possible future use in these batteries was assessed.
Hansen paper emphasizes importance of retention and expansion of nuclear power for health and climate reasons
April 04, 2013
|Mean number of deaths prevented annually by nuclear power, 1971-2009. Credit: ACS, Hansen et al. Click to enlarge.|
A new study by James Hansen and Pushker Kharecha from the NASA Goddard Institute for Space Studies and Columbia University Earth Institute has found that global nuclear power has prevented an average of 1.84 million air pollution-related deaths and 64 gigatonnes of CO2-equivalent (GtCO2-eq) greenhouse gas (GHG) emissions that would have resulted from fossil fuel burning. The estimated human deaths caused by nuclear power from 1971 to 2009 were far lower than the avoided deaths: 4,900, or about 370 times lower than the result for avoided deaths.
Projecting ahead, on the basis of global projection data that takes into account the effects of the Fukushima accident, Hansen and Kharecha also calculated that nuclear power could additionally prevent an average of 420,000−7.04 million deaths and 80−240 GtCO2-eq emissions due to fossil fuels by mid-century, depending on which fuel it replaces. Large-scale expansion of unconstrained natural gas use would not mitigate the climate problem and would cause far more deaths than expansion of nuclear power, according to their analysis, which is published in the ACS journal Environmental Science & Technology.
UC Davis study identifies toxicity of particulate matter from specific sources
February 19, 2013
The California Air Resources Board and the Electric Power Research Institute (EPRI) released a report they commissioned by investigators at the University of California, Davis that looks at how to distinguish health effects caused by different types of fine and ultrafine airborne particulate matter (PM) from different sources. This is among the first studies to examine the toxicology of particles according to their source origin. Previous research has linked fine and ultrafine particles to asthma, heart disease and other adverse health effects.
These particles—produced by emissions from many different sources, including traffic, industrial processes, wood-burning fireplaces and gas- and coal-fired power plants—combine in the atmosphere and are affected by sunlight and other meteorological variables. National Ambient Air Quality Standards do not distinguish between these source since they are based solely on mass in given particle size rang. Further, the mixing makes it difficult to determine which compounds in particulate matter may be responsible for specific health effects.