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Auto emissions roadmaps: A comparison
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p68.jpg (19069 bytes)Diesel vehicles emit extremely carcinogenic particulates that significantly damage our health. Diesel particles are coated with extremely toxic chemicals — about 40 known carcinogenic substances have been identified in diesel exhaust. In 1998, the California Air Resources Board, USA, branded diesel particles as toxic air contaminants. Subsequently, the US Environment Protection Agency (EPA) also accepted diesel particles as carcinogens.

In its assessment of new emission regulations for heavy-duty diesel vehicles, slated to come into force in 2007, USEPA states that "the most compelling information that suggests a carcinogenic hazard is the consistent association observed between lung cancer and diesel exhaust exposure in occupationally exposed workers". EPAreviewing published literature, and found that about 30 different epidemiological studies showed an increased risk of lung cancer associated with diesel emissions. EPA evaluated 22 studies most relevant for risk assessment; 16 reported significant increase in lung cancer risks — 20 to 167 per cent — due to exposure to diesel exhaust.

The only study available on Indian cars, by Swedish consultancy Ecotraffic, shows that the cancer potency of diesel exhaust is more than twice that of petrol cars. If only particulate emissions are considered, the carcinogenic effect of one new diesel car is equivalent to 24 new petrol cars and 84 new CNG cars on the road. According to a study conducted by the German Federal Environment Agency, diesel is "several dozen" times more cancer-causing than petrol.

The problem: small particles that harm
Nearly all diesel particles fall into the fine particle size range (less than 2.5 microns); 50-90 per cent fall into the ultra-fine particle size range (less than 0.1 micron). Small size and large numbers offer greater surface area that allows toxic organic compounds to get adsorbed easily. In this way, diesel particles can go deep into the lower respiratory tract and, damaging lungs.

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DPM is just about 6 per cent of US’ total ambient fine particulate matter inventory. Yet, the US wishes to control it

dot3.gif (72 bytes) In urban areas such as California, Colorado and Arizona DPM is 10-36 per cent of ambient fine particulate level.

dot3.gif (72 bytes) Exposure from diesel vehicles (mid 1990s estimate) — 0.5 to 0.8 micrograme DPM/cum of inhaled air in rural and urban areas, respectively.

dot3.gif (72 bytes) For localised urban areas where people spend a large portion of their time outdoors — 4.0 micrograme DPM/cum of inhaled air.

US is investing aggressively to cut diesel emissions by nearly 95 per cent with the most stringent standards ever.

Why? Some particles are more deadly and therefore, a special cause of concern. These are diesel particulates and sulphate particles that are formed by the release of sulphur dioxide when diesel is burnt. These are responsible for serious health problems including a large number of premature deaths worldwide.


Source: Health Assessment Document for Diesel Engine Exhaust, US EPA, May 2002

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Studies have proved that diesel vehicles emit fine and ultra-fine particles in very large quantities. According to the California Air Resources Board, 94 per cent of the particle mass diesel vehicles emit is smaller than 2.5 microns. Another study in the UK found that 85 per cent of particles were less than a micron in size.

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Diesel is injurious to health

Particulate Air Pollution and Morbidity in the California Central Valley, 2002: Observed a strong and consistent increase in the rate of hospitalisation and/or emergency room visits for acute or chronic respiratory conditions associated with exposure to PM2.5. Every 10 per cent increase in the level of PM2.5 was associated with a 4.1 per cent increase in acute respiratory hospitalisations, a 7.5 per cent increase in chronic respiratory hospitalisations, a 5.2 per cent increase in acute respiratory emergency room visits and a 6.5 per cent increase in chronic respiratory emergency room visits.

National Environmental Trust released a report in 2002: This calculates the cancer risk to children in the five most populated air basins in California. The report found that exposure to DPM will cause infants to reach the U.S. EPA’s one-in-one-million lifetime cancer limit in 17-32 days, depending on the air basin they live in. By the age of one, children will have exceeded this benchmark by 11 to 21 times, and by age 18, by 121 to 252 times. Adults reach the US EPA’s one-in one- million-lifetime cancer limit in 35-71 days from exposure to DPM. The California EPA’s cancer unit risk estimates were used in this study.

US Public Interest Group (US PIRG) released a report in 2002: This estimates the lifetime excess cancer risk to the U.S. public from hazardous air pollutants. The report was based on population exposure levels from the EPA’s NATA report, and DPM toxicity estimates from the California EPA. The report concluded that throughout the U.S. the lifetime excess cancer risk from breathing hazardous air pollutants was 1 in 1,200, with DPM accounting for 89 per cent of this risk. Of the cancer risk from breathing DPM, 32 per cent is from emissions from on-road sources, and 68 per cent is from off-road sources.

The World Health Organisation used four different studies: The studies were about the carcinogenic impact of diesel exhaust on rats. WHO used it to estimate unit risk values for cancer. Its conclusion was that the lifetime excess cancer risk ranged between 1.6 and 7.1 in 100,000 excess cancer cases per g/m3 of DPM. This translates into one excess cancer case in a million from a lifetime diesel exhaust exposure of 0.014 to 0.0625 g/m3 of DPM.

Puget Sound Clean Air Agency released a draft report in 2002: This compared local air toxics monitoring data with data from the EPA’s NATA modeling estimates for the Puget Sound region. The Agency’s review confirmed the NATA modeling data and concluded that DPM accounted for 70-85 per cent of the total excess lifetime cancer risk from all air toxics in the region, with mobile sources of DPM contributing 85-95 per cent of the total risk.

California’s South Coast Air Quality Management District released the results from their Multiple Air Toxics Exposure Study (MATES-II) in 1999: MATES-II was a comprehensive urban air toxics monitoring and evaluation study. Using the California EPA’s lifetime excess cancer unit risk estimate of 3 in 10,000 per g/m3 of diesel particulate matter, the MATES-II study concluded that this was responsible for 70 per cent of the excess lifetime cancer risk resulting from air pollution in Los Angeles and the surrounding area, leading to an added average lifetime cancer risk of 980 in one million from exposure to diesel particulate matter.

WHAT EVERYONE KNOWS: Disel is carcinogenic

Year  Organisation Conclusion
2002 US Environmental Protection Agency Likely human carcinogen
2001 American Council of Government Industrial Hygienists (proposal) Suspected human carcinogen
2001 US Department of Health and Human Services Reasonably anticipated to be a human carcinogen
1998 California Air Resources Board Toxic air contaminant
1996  WHO International Programme on Chemical Safety Probable human carcinogen
1995  Heath Effects Institute Potential to cause cancer
1990 State of California Known to cause cancer
1989 International Agency for Research on Cancer Probable human carcinogen
1988 National Institute for Occupational Safety and Health Potential occupational carcinogen
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Source: January 2004, Patricia Monahan and David Friedman, The Diesel Dilemma, Diesel’s role in the race for clean cars, Union of Concerned Scientists

As part of the Risk Reduction Plan to Reduce Particulate Matter Emissions from Diesel-Fueled Engines and Vehicles the California Air Resources Board compared the lifetime excess cancer risk from diesel particles with the cancer risk from the top ten air toxic risk contributors, using exposure information from its statewide air toxics monitoring network, and the California EPA’s cancer unit risk estimate. CARB’s conclusion was that exposure to air toxics in the state resulted in an average excess lifetime cancer risk of 758 in one million, and that diesel particles were responsible for more than 70 per cent of this added lifetime cancer risk.

A study published by the US based Natural Resources Defence Council in January 2001: It points out that schoolchildren suffer from sustained exposures to diesel exhaust while travelling in school buses for 1-2 hours every day during a school year of 180-200 days over a schooling period of 10 years. It concludes that a child riding a diesel school bus is being exposed to as much as 46 times the cancer risk considered significant by the USEPA.


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