The main particulate fraction of diesel exhaust consists of small particles. Because of their small size, inhaled particles may easily penetrate deep into the lungs. The rough surfaces of these particles makes it easy for them to bind with other toxins in the environment, thus increasing the hazards of particle inhalation. Exposures have been linked with acute short-term symptoms such as headache, dizziness, light-headedness, nausea, coughing, difficult or labored breathing, tightness of chest, and irritation of the eyes and nose and throat. Long-term exposures can lead to chronic, more serious health problems such as cardiovascular disease, cardiopulmonary disease, and lung cancer.
Exposure to diesel exhaust and DPM is a known occupational hazard to truckers, railroad workers, and miners using diesel-powered equipment in underground mines. Adverse health effects have also been observed in the general population at ambient atmospheric particle concentrations well below the concentrations in occupational settings.
Recently, concerns have been raised in the U.S. regarding children's exposure to DPM as they ride diesel-powered schoolbuses to and from school. The Environmental Protection Agency (EPA) has established the Clean School Bus USA initiative in an effort to unite private and public organizations in curbing student exposures.
Health Effects of Diesel Exhaust Particulate Matter
Diesel engines emit a complex mixture of air pollutants, composed of gaseous and solid
material. The visible emissions in diesel exhaust are known as particulate matter or PM,
which includes carbon particles or "soot." Diesel exhaust also contains a variety of
harmful gases and over 40 other known cancer-causing substances. In 1998, California
identified diesel PM as a toxic air contaminant based on its potential to cause cancer,
premature death, and other health problems.
Each year in California, diesel PM contributes to 2000 premature deaths and thousands
of hospital admissions, asthma attacks and other respiratory symptoms, and lost
workdays. Overall, diesel engine emissions are responsible for the majority of
California's known cancer risk from outdoor air pollutants. In addition, diesel soot
causes visibility reduction and is a potent greenhouse agent involved in global warming.
Summary of the Health and Environmental Effects
of Diesel PM Exposure for California*
?? Premature deaths (2000 per year)
?? Lung cancer (250 per year)
?? Decreased lung function in children
?? Chronic bronchitis
?? Increased respiratory and cardiovascular hospitalizations
?? Aggravated asthma
?? Increased respiratory symptoms
?? Lost workdays
?? Reduction in visibility (10 to 75% of total)
?? Global warming (2nd to carbon dioxide) *Except for lung cancer, the health effects are based on the assumption that diesel exhaust PM is approximately as toxic as the general ambient PM mixture.
Diesel Particulate Matter (PM) Contributes to Premature Death
PM is a contributing factor to premature death from heart and/or lung diseases, based
on studies of over 500,000 people (Pope et al., 1995, 2002), and independently verified
with a reanalysis requested by industry and the U.S. Congress (Krewski et al., 2001).
Average life expectancy was reduced by about 1.5 years, comparing the cities with
highest and lowest high PM levels (Brunekreef, 1997). This translates to a loss of about
14 years of life for people who died from diseases associated with PM exposure
(USEPA, 1999). These studies serve as the basis for PM air quality standards by ARB,
U.S. EPA, the World Health Organization guidelines for Europe, and other countries.
