Air pollution, it is said,  is the bane of modern 20th-century civilization. The ushering in of the Industrial Age in the late 19th-century saw the rise of  mighty industries and nations steep-ped in science and technology, that also brought in unparalled convenience and    comfort   to mankind in general.  Sadly, however, this human industrio-tecnological  revolution has seriously degraded the environment. Belatedly recognized only in the early 70s, air pollution  has proved to be a menace to man's health. But what exactly is air pollution ? Where does it come from ? What are its deterious health effects? How do we prevent  or control them ? The U.S. State of  California was considered one of the most-polluted regions in the 1970s . What were its find-ings? Click here to find out  - Air Pollution Sources, Health Effects and Controls .

   Dry, un-polluted air has the following chemical composition:

   Composition of dry unpolluted air
 

                                         Source :  The CRUCIAL WEBSITE, a Hong Kong Education project.

    The ratio of motor vehicles to people ranges from around 23 persons to a vehicle here in the Philippines, to about 1.5 people per vehicle in the United States. With millions of these vehicles burning more than  99% fossil-based fuel or petroleum fuel, it's no wonder we're really and lit-erally breathing hazadous air pollutants, especially those of us who dwell in large   urban cities where the bulk of trucks, buses, automobiles, and jeepneys (not to mention large factories and machineries) are concentrated.

Hazardous Air Pollutants and the Motor Vehicle

    Automobiles and trucks are significant sources of several hazardous air pollutants, among them :

• Nitrogen Oxides - These pollutants are produced whenever fuel is burnt. These emissions contribute to the formation of photochemical smog and acid rain. In the United Kingdom, for instance, traffic is responsible  for almost  half of the total NOx emissions.    Another study by the U.S. Environmental Agency (EPA) cites  mobile sources as accounting   for 44% of  "NOx emissions nationally."
• Hydrocarbons - These are chemicals containing hydrogen and carbon atoms and are pre-sent in the combustion product of fossil fuels. HC emissions are released from motor ve-hicle  exhaust and is usually the result  of unburnt or partially burnt fuel . Hydrocarbons also contribute to the formation of  photochemical smog.
• Carbon Monoxide - This is a toxic gas produced when fuel is burnt incompletely. It is estimated that road transport account for more than 90% of CO emissions in the world's major cities.
• Carbon Dioxide - CO2 is a by-product of the combustion of fossil fuels. Unfortunately though,  CO2 in large quantities (such as are produced in traffic conditions) contribute to global warming.
• Sulfur Dioxide - Sulfur is present in gasoline (or, petrol)  and diesel fuels, however sulfur concentrations are higher in diesels than in gasoline  (although legislations in the industria-lized countries, and, more recently, in the Philippines, have reduced the levels permissible). Sulfur dioxide is an acidic gas and contributes to acid rain and wintertime smog.

•  Lead  - This metal has been added to gasoline (petrol) to improve engine performance. When burnt, lead is emitted from the exhaust. Lead is a known poison which accumulates in humans and affects the development of children. However, emissions of lead are falling due to reduced lead content in leaded gasoline and the widespread use (at least in the ind-ustrialized countries)   of unleaded fuel.  Diesel fuel  has no lead content.
• Benzene - is naturally present in crude oil and, like lead, acts as an octane enhancer, which prevents the fuel from igniting prematurely and damaging the engine. Benzene is  present in gasoline exhaust, and to a lesser extent, evaporates into the air durng refuelling or operation of the vehicle. Benzene is a known carcinogenic (a cancer-causing substance).
• Aldehydes - a group of chemicals emiited from car exhaust as a result of incomplete com-bustion. Although all aldehydes are suspected carcinogens, formaldehyde is the most significant.
• Particulate Matter - Tiny (10 microns or less) airborne particles that can carry toxic substances, including heavy metals and chemicals, and cause irritation to the lungs. In the cities, exhaust from diesel trucks and buses is a significant source of particulate. Other ef-fects of suspended particulate matter,  PM10, include reduced visibility, soiling through deposition, and the formation of acid aerosols.
• Polycyclic Aromatic Hydrocarbons (PAHs) - Found in exhaust emissions from internal combustion engines (both gasoline and diesel engines), though more so in diesels. Some PAHs adhere to particulate matter. PAHs are highly toxic to aquatic organisms and   are thought to be human carcinogens.
• Ozone - Produced by the reaction of oxygen gas with free atoms of oxygen which are formed from the reactions between nitrogen oxides and hydrocarbon in sunlight. Ground-level Ozone, O3, is the same as that ozone blanket found in the upper layers (stratosphere) of the earth and which serves to protect us from ultra-violet rays of the sun. Ozone reacts with hydrogen to produce aldehydes and smog.
• Peroxyacetyl Nitrate (PAN) - a product of the complex reaction between oxygen gas and unburned hydrocarbons, PAN is a toxic and lachmatory (ie, produces tears) substance  that make up some of the chemicals in photochemical smog.

Vehicle Emissions Control Technology- A Comparison

       Which  emit more (or, less) harmful air pollutants - a diesel or a gasoline vehicle ? This question has been the subject of much debate among proponents and government environ-mental agencies. Click here for one such  interesting article on the topic.

    The article, quoting sources from the both the British government and private think-tank groups, was cautious in its conclusion that :
 

".... there is no clear-cut winner in the environmental stakes, as both cars have          their advantages and disadvantages, which are further complicated by the var-          ious new emission technologies which may become standard in the near future."

    These "new emission technologies" run the gamut of upgraded  enginedesigns , engine lubricating oils, multi-point injection systems, the continuing search for     alternative fuels, desulfurization of diesel fuel, use of additives to mitigate harmful emissions,  water-based fuel emulsification,  dual-fuel fumigation system, particulate traps and catalytic converters,    EGR systems,  and so on.

     The bottom-line is that -  unless an alternative fuel to present-day internal combustion eng-ines is found that is economical to produce, technologically efficient, in abundant  supply, and is allowed to "phase in" into the  worldwide infrastructure of the current manufacturing    and distribution complex of fossil fuel - petroleum fuels(i.e., gasoline and diesel fuel) will continue to be the transport fuel well into the next century. And everyone will continue to be challenged by its concomittant polluting effect,
for better or for worse.

Emission from MobileSources in Metro Manila - Preliminary Findings

     Air pollution due to the heavy concentration of motor vehicles and industries in Metro Manila is a major environmental problem. Of the more than 3.8 million registered vehicles in the country in 2001,  roughly 40% are found in Metro Manila. Almost a third of the total registra-tions (about a million) are diesel-powered.

     Present levels of air pollutants  in Metro Manila from mobile sources are estimated at 116,000 tons of particulate matter of less than 10 microns (PM10),  39,000 tons of sulfur oxide (SOx), 140 tons of lead - as well as undetermined amounts of carbon monoxide (CO), hydro-carbons (HC), nitrogen oxides (NOx), and volatile organic compounds (VOC).  This, accor-ding to an Asian Development Bank (ADB)  1998 study entitled "Report on Metro Manila Air Quality Improvement Sector Development Program" and cited by SwissContact in its recent pre-feasibility study.

    By way of comparison, in  the U. S., per Internet documents made available  from the Federal Register Online via GPO Access (wais. access.gpo.gov), the "diesel contribution to emission inventories" may be summarized as follows:

 Unleaded gasoline

    The use of tetra-ethyl lead as an additive for gasoline was first tested in the 1920s by Charles Kettering  in the Research facilities of General Motors. Kettering wanted to get rid of what he called the "noisy bugbear" of knock, the rackety sound that was the sign of a poorly running car engine. Later, mounting evidence of lead poisoning and deaths occuring among the workers of Standard Oil and  DuPont Company prompted U.S. health officials to suspend the produc-tion of this new fuel compound. The U.S. Surgeon General was tasked to consider its pros and cons at a series of public hearings.

    But corporate interests dominated the hearings, and it was shown that the men who died had been exposed to concentrations far greater than the motoring public ever would in using leaded gasoline. So, in the end, the ban on leaded gasoline was lifted.

    In the Philippines prior to 1993, lead values exceeded  WHO standards by 200%. But  since the introduction of "unleaded gasoline" (actually still containing lead at 0.15gms/ltr.) in Metro Manila and in some parts of the country, emissions have abated.  However, unleaded gasoline  accounts for only 1/5 of total gasoline sales throughout the country, despite its price advantage over premium (leaded) fuel. Under the 1999 Clean Air Act, it shall be unlawful to sell or use leaded gasoline after 18 months after its enactment. (Note: Complied with as of mid-2000-IJR)

    On the other hand, the dangers of CO poisoning from gasoline exhaust continue to be very real. It has been determined  that an adult exposed to an atmosphere of 1000 ppm for 4 hours is likely to die from CO fumes, while that of one exposed to 4000 ppm would cause his death in an hour. Ozone, HC,  VOCs, and to a lesser extent, NOx, contribute to respiratory and lung diseases.     By far, though, the most insidous form of gasoline toxicity appears to be from the aromatic content of gasoline. Benzene, a component of gasoline, is the most significant bec-ause it is now established to be carcinogenic, or,  cancer-causing.

Diesel Fuel

    Meanwhile, diesel fuel - and its attendant diesel smoke emissions spewed by trucks, buses, and jeepneys along the major thoroughfares of Metro Manila - is bearing the brunt of a con-certed effort by the government and other multi-sectoral entities like the Asian Develoment Bank (ADB), the Philippine Business for Social Progress (PBSP)  foundation, and concerned private advocacy groups, among others.

    The greatest pollution threat, of course, from diesels is from NOx (about twice that of a gasoline car equipped with a catalytic converter) and particulate matter, PM10, from black smoke.  Particulates, because of its small size (about 10 microns or less in diameter) penetrate deeper into the lung tissues. In 1998, the U.S. Environmental Protection Agency (EPA) declared PM as "toxic." However, this ruling is currently on appeal by the Engine Manufacturer's Association (EMA), fol lowing admissions by the HEI - an industry  health watchdog - that the study was based on insufficient data.

    Locally, two(2) reasons are commonly cited for the abundance of diesel units with smoky exhausts, namely:  the fuel quality available here in the Philippines, and, the poor state of main-tenanceof our mass-transport system. Fuel - its characteristics and quality - is treated elsewhere in this report (see Automotive Fuels) . On the other hand,  much has been written or talked a-bout on how poor  the maintenance is of a typical Philippine bus or jeepney. The average pas-senger bus plying the EDSA (Epifanio de los Santos Avenue) route and other major thorough-fares of Metro Manila are 10 to 15 years old, having been imported tax-free as "reconditioned" buses under 1988 Executive fiat of Pres. Cory Aquino. The durable jeepney descended   from the World War II "jeep" converted into a passenger vehicle during the early Liberation years but has now metamorphosed into a locally-assembled or fabricated body with imported second -hand diesel engine and drive line components.

    The older engine technologies (some reaching as far back as the 1960s yet) installed in most Philippine diesel vehicles are mainly responsible for the unabated road pollution that we witness today. They are, in fact, the rai-son d'etre for the tough  anti-pollution legislations enacted by the industrialized countries in the 70s. Recently, the Philippines followed suit with its own enactment of the 1999 Clean Air Act.

    Other than the engine itself,  the fuel injection  system is a vital, though, separate, component that needs attention also. Many diesel fleet operators (and almost all of the individual jeepney operator/ drivers, for that matter) contrive to "get by"   with injection pump repairs  done by 'hole-in-the-wall' calibration shops that prolilferate in the streets of the metropolis. For some useful tips on diesel engine maintenance, please click (/) to this section.

        What Fuel changes Might Help?

    "What fuel changes might help?"  This is the title of a very informative segment of the Adm-inistrator's report of the United States Environmental Protection Agency filed May 6, 1999 under Billing Code 6560-50-P, extensively quoted  here.