Loading...
HomeMy WebLinkAboutLife of Soot Life of Soot: Diesel Pollution, Emissions, and Health Effects Page 1 of5 , # UNION OF CONCERNED SCIENTISTS Citiuns and Scientists for Environmental Solutions www.ucsusa.org Clean Vehicles B Ma U this to a frie nd backgrounder Diesel Pollution Primer soot formation, emissions, dispersal, and health effects At some point or another, we've all gotten caught behind an l8-wheeler, a garbage truck, a tractor, or a bulldozer and seen, smelled, and even felt the clouds of soot coming from their tailpipes. But how and why does diesel fuel produce this haze of soot, or particulate . matter (PM), and how does it affect the bodies of those who ~"'- ~ breathe it in? In this backgrounder we take a look at the lifecycle of soot and. explore its implications.for your family's health. The Birth of Soot Soot, or particulate matter (PM), begins its life in the belly of both gasoline and diesel-powered engines. These engines create chemical and organic compounds from the combustion of hydrocarbon-based fuels (fossil fuels). These compounds then cluster together in particle form to create soot, which is released into the air as exhaust. Soot may also come to life as the indirect byproduct of nitrogen oxides (NOx) and sulfur dioxides (SOx) reacting in the atmosphere. Soot) s composition often includes hundreds of different chemical elements, including sulfates, ammonipm, nitrates, elemental carbon, condensed organic compounds, and even carcinogenic compounds and heavy metals such as arsenic, selenium, cadmium and zinc.l One of reasons conventional diesel engines release more soot than their conventional -' gasoline counterparts has to do with the '" ~iLATEO Ll~KS way fuel is injected and ignited: on gas in, clean vehicles engines, fuel is injected during the intake R~.Q1't: Sick Q(S.~19J stroke and ignited with a spark; on diesels, fuel is injected during the compression ,Analys1~-= Ilean~uty_ stroke, and the fuel ignites spontaneously Dies_el from the pressure. As a result, gas engines CA_,Diesel Ri_s_k_Reduct~JJ have two emissions advantages: The :PblD ignition process is more carefully Diesel_E.ugines & P.l.tbJ,i~ controlled and the air and fuel are more B~.;llth thoroughly mixed before ignition occurs, thereby reducing the amount of unburned o ff.site fuel. In a conventional diesel, fuel is injected CleanS~_hoolBus.org late in the cycle and the air is not as well Campaign mixed as in a gasoline engine. As a result of this less homogeneously mixed fuel and air, there are fuel-dense pockets in the combustion chamber. The consequence is that diesel engine exhaust contains incompletely burned fuel (soot) known as http://www.ucsusa.org/clean_vehicleslbig_ rig_ cleanup/life-of-soot-diesel..pollution-emissions-and-heaI... 5/1/2006 Life of Soot: Diesel Pollution, Emissions, and Health Effects Page 2 of5 "- , particulate matter. ~ But it's not "engine-out" pollution that really matters-if's what comes out of the tailpipe. Gasoline engines have gotten a lot cleaner over time through the use of add-on pollution controls, . like catalytic converters. The environmental Protection Agency (EPA) has passed increasingly stricter standards for gasoline engines, and as a result, catalytic converters are now standard on every new gas car. The real reason diesels pollute more soot is that EP A has not forced them to meet the stricter standards facing gasoline engines. The soot standard for diesel cars under EP A's Tier 1 regulation is at least ten times the average emission from a gasoline car. But under the new Tier 2 regulations, which will phase in between 2004 and 2009!1 diesels will fmally have to meet the same strict standard as gasoline cars. A diesel engine particulate filter Diesel cleanup technology has come a system long way. From diesel particulate traps to oxidation catalysts, there are now various methods of catching or converting much of diesel pollution before it escapes the tailpipe. Starting in 2009, all diesel light trucks and cars will have to meet the same tailpipe standards as gasoline vehicles. But new engine standards alone are not enough to protect the public from diesel pollution. New standards for diesel engines will be slowly phased in over the next 10 years. Plus, the durability of diesel engines means that older, high- polluting vehicles can continue to operate for decades. Diesel soot emissions are furthered by the fuel itself, as today's conventional diesel fuel contains significantly more sulfur than does gasoline~J Soot's exact composition is difficult to characterize because different engine technologies and conditions produce different types of soot. Indeed, the smoke clouds coming from diesel engines can even have different colors. For example, blue smoke (mainly oil and unbumt fuel) can indicate a poorly serviced and/or tuned engine; black smoke (soot, oil and unburnt fuel) can indicate a mechanical fault with the engine; and white smoke (water droplets and unburnt fuel) is produced when the engine is started from cold and may disappear when the en~ine warms up.4 The soot in. your neighborhood may be different than the soot in someone else's hometown, but no matter the source and type, soot can present a grave health threat. oot's Journey Across the Land s previously mentioned, soot particles either come irectly from the tailpipe, or can be formed when tailpipe missions of NO x and SOx react with atmospheric agents. nee formed, soot comes in many sizes, though all just a fraction of the width of a human hair, from coarse PM (less than 10 microns in 'diameter) to fine PM (less than 2.5 microns) to ultrafine PM (less than 0_1 microns)_ Most soot is in the fine and ultrafine categories, with ultrafine particles making up 80-95%, of soot. Ultrafine particles are the most dangerous!I however, as they are small enough to penetrate the cells of the lungs. Soot particles can have an environmental lifetime of one to three weeks, and they can travel long distances, journeying to communities in far regions. Soot particles have even been found at the South Pole, where no major emission source exists for thousands of miles. 5 But in general, soot tends to fall out of the atmosphere close to the source of the pollution. The further you are away from diesel exhaust sources, the better for http://www.ucsusa.org/clean_vehicleslbig_ rig_ cleanup/life...of-soot-diesel-pollution-emissions-and-heal... 5/1/2006 Life of Soot: Diesel Pollution, Emissions, and Health Effects Page 3 of5 '~ ~ your health, and vice-versa. In California, the home of the nation's largest fleet of diesel vehicles, roughly 80 percent of the state's diesel pollution sources are found in 5 of the 15 air basins. Showing that the effects of diesel soot are, mostly close to the source, about 87% of California's over $21.5 billion yearly diesel exhaust-related health care costs come from the same 5 air basins.Q Estimated Premature Deaths by Diesel Exposure by CA Air Basin ?_Nonheast Plateau (3)> (~}::\..;.:: ~sacramonto V;JIlloy (172) North Coaat (9) ~ .'. . Mo nta. Co t'.. (7J \ , ,~i ~"'a~ u en un , uko COllnty (<1)'j~;~~.~, Cd. LaM 1"ahoo (1) ,\: .~" .~. nJoaQulnValley(2601 .. " "<, ."''';- "',~~ ~ ~~~~ Sa... Fr.anc:,"o ~ ,) , f*1l.~ 9'17 ~ I!r~ (6GO) " ':::~ ~ ' _ ~"'~"'-1,~ ~ ii}~~, k~P4 NorIb Central .. ':>!i'!:~ .1t~ CoaS:;;~~7;.i~,,~!;~~{Ii,MO~VO Desert (23) _-:c,;-....;.<:<<__.;: ..~~~,..._... .":;:. , ._ South' Coast (1~415) J,':' -;~;.' -~.~/:--'\~\\<.:'~~.~'.':\.~ San Diogo (244) ~ ~ Salton Sea (31) NOTE: Premature deaths are a result of exposure to diesel particulate matter, . both direct from the tailpipe and from the conversion of NOx emissions to particulates in the atmosphere. Estimates for indirect particulate exposure for each air basin are based on a conversion of NOx emissions to particulates. SOURCE: Image courtesy of CARB. Soot's Trip Through Y oor Body As soot travels through the air in your community, you breathe it in, and so it starts the next phase of its journey: a trip through your body's respiratory system. Large soot particles (> 10 microns) deposit in your nose, throat, and lungs, causing coughing and sore throat, and are ejected from your body through sneezing, coughing, and nose blowing. Coarse particles (10 microns) are inhaled into your windpipe and settle there, causing irritation and more coughing. Fine and ultrafine particles (less than 2.5 microns) are the most successful in invading your body, small enough to travel all the way down deep into your lungs. , IDi~~~IS~~t-~h;;ti~~.-- I Once there, these soot particles can 1 irritate and mutate the most sensitive tissues in your lungs: your alveoli. These air sacs line your lung's alveolar ducts and are the primary gas exchange units of the lungs. Surrounded by networks of 'blood capillaries, alveoli exchange oxygen and carbon dioxide from the air you breathe in with blood in your capillaries, thus allowing your circulatory system to carry oxygen to the rest of your body. Soot particles, however, make this task more difficult as they cause inflammation and scarring of these alveoli. 7. Scar tissue builds up and slows oxygen flow to your capillaries, Click the image above to see how soot straining your heart because it must work travels through the body in this harder to compensate for oxygen loss. http://www.ucsusa.org/clean_vehicleslbig_ rig_ cleanup/life-of-soot-diesel-pollution-emissions-and-heal... 5/1/2006 Life of Soot: Diesel Pollution, Emissions, and Health Effects Page 4 of5 l- animation (courtesy of the Long Beach Soot also finds other ways to harm your Press Telegram's Toxic Air Se.rie~) body, including causing chronic bronchitis and asthma. These conditions occur when the linings of your lung's bronchioles (air passageways) become irritated and swollen, in turn causing your lungs to create mucus to soothe the irritation. These conditions prevent your bronchioles from moving oxygen to the rest of your body. Symptoms can range from coughing and shortness of breath to severe and fatal attacks of oxygen loss.. In addition, soot particles also reduce your respiratory system's ability to fight infections and remove other foreign particles. Soot particles can also act as carriers of carcinogenic compounds into your body.. Compounds in soot such as polycyclic arOmatic hydrocarbons (P AHs) are carcinogenic, and diesel soot itself is classified by many government agencies as either a probable or known cancer-causing agent. For example, the California Air Resources Board has concluded that diesel soot is responsible for 70 percent of the state's risk of cancer from airborne toxies. Lastly, diesel pollution can be deadly, causing premature mortality through cancer or heart and respiratory illnesses. In the population as a whole, studies have shown a 26% increase in mortality in people living in soot-polluted cities. Soot's Harms Vulnerable Populations Most Although all human beings are susceptible to soot's journey through their body, individuals with preexisting respiratory conditions, children, and the elderly are the most vulnerable to soot's lasting and deadly effects. People with heart disease, emphysema, asthma, and chronic bronchitis suffer from increased hospital adm~ssions and emergency room visits as a result of exposure to soot. Children-and their developing ~ungs-may also suffer more acutely from breathing in diesel soot. Outdoors more often and breathing in more air per body weight than adults do, children suffer disproportionately from asthma and other respiratory conditions. Asthma is the most common chronic disease of childhood and a leading cause of disability among children; today about one in thirteen children have asthma. Elderly persons also bear a large burden when coming in contact with soot. Studies estimate that tens of thousands of elderly people die prematurely each year from exposure to ambient levels. of fine PM.8. A Costly Journey In the end, soot travels far and wide to affect thousands of communities and millions of people, including you and your family. It begins in the combustion of an engine and ends up in the innermost reaches of individuals' lungs. Society pays a heavy price for soot's journey.. Billions of dollars in health cwe costs, the loss of work and school days, and-the loss of human lives create an enormous burden for society to shoulder. This burden is not a necessary one, however, as it can be lifted from off our backs with the help of stricter air regulations and cleaner engine technology . Notes 1) Minnesota Pollution Control Agency: Particulate Matter (TSP and PM-I0) in , Minnesota..- !Y..ww.ll-~.MjJ1e.mn~!ls/air/eD1l~sions/pmlfl,-b1ml 2) Diesel Technology Forum: New 'Teclmologies: Diesel Filters-.. httD:llwww.dies~lforum..9xg{factsh~eJ/tr~.llLm-1 3) Sierra Club: Health Effects Associated with Diesel Emissions-.. http://wwjy~i~J:n~xl]tb.!-Q.rgLcle~nair/facJsheets/ diesel.~p- http://www.ucsusa..org/clean_ vehicles/big_rig_ cleanup/life..of-soot-diesel-pollution...emissions-and-heal... 5/1/2006 Life of Soot: Diesel Pollution, Emissions, and Health Effects Page 5 of5 ~.l- .. 4) Health & Safety Executive: Diesel Engine Exhaust Emissions .- h!tp:/lwww .-'lS~~9.Y._Jtkl~\lbns/j ndg186. bim 5) Environmental Health Perspectives: Seeing Through Soot-... bttn:II~~Djehs.niJLgpv Im~mb~.rs/2001l11 0-8/in~ov aJIQDs. html 6) Union of Concerned Scientists: Sick of Soot, pp. x-xi 7) Long Beach Press Telegram: Toxic Air: How Poor Air Quality Affects the Respiratory System .... J1ttp:/ /la_W1-~,~stel~nlm!com/projects/tQ~kairI.IDedi~.&l~ic~kJqgg~~wf . 8) US Environmental Protection Agency: Health and Environmental Effects of Particulate Matter -- bttp_~!Jwww.~.~ov Ittn/ oa-wgLMJlq!.tIDLp_mhJ~}!lth....btml Page Last Revised: http://www..ucsusa.org/clean_ vehicleslbig__rig_ cleanup/l ife-of-soot-diesel-pol lution-emissions-and-hea 1... 5/1/2006 l .. :J ;If" throat ~e. At ~le"the th the ik, and front. , about lewhat ing is >r, the '8ge to :r," but l swaI- .w 8cnd Itrates Illy" ' if or Dot Jmodic ('swaI- :8 con~ dpipe~ inches apsing tilage, gerup of the ~e the 3 very teadily ake an ;0 per- pass a larynx he top It, the .i," one" to the , more anda )f for- ed the t bron- ~ lung, ever- -.. tree" lJ into warmed pdoor, " 8.,01 air l). The tI to the r I..... Big Rig Cleanup i~ex Page 1 of 1 UNION OF CONCERNED SCIENTISTS Citizens and Scientists for Environmental Solutions www.ucsusa.org Clean Vehicles EJ Ma il1:his 1:0 a 1rie nd big rig cleanup "Big rigs" haul our goods. They dig our ditches. They harvest our crops. They drive our children to school. But these OD- and off-road vehicles- trucks, buses, tractors, and combines, just to name a few-are often forgotten when discussing the health, energy security, and environmental impact of transportation in America. Diesel engines, which power a majority of big rigs, release a mixture of smog-forming pollutants, particulate matter (soot) that can penetrate deep into our lungs, and other toxic constituents such as arsenic, cadmium, dioxin, and mercury. Children, because their lungs are developing, are particularly vulnerable to diesel exhaust, which has been linked to a host of severe health problems including asthma, cancer, and even premature death. Cleaning up big rigs has been an extremely slow and difficult task. DeS is working to raise awareness of the severity and importance of this issue, as well as creating and preserving the solutions that will ensure a healthier future for us and our children. Our cleanup strategy includes: . advocating strict emission standards for new highway and off-highway engines . providing incentives and passing regulations to clean up existing engines . replacing and retrofitting older school buses with cleaner alternatives Page La~ http://www.ucsusa..org/clean_vehicles/big_rig_cleanup/?print=t 4/25/2006