Health and Environmental Effects
Combustion engines have been traditionally used as the primary means of transportation and industrial power. These types of engines have historically provided the most cost-effective power plants for many applications, explaining their popularity. The way we see it, this will not likely change in the near future. Unfortunately, however, the exhaust byproducts from the combustion process have had serious detrimental effects not only on public health, but also the overall environment. Controlling the harmful emissions of these engines has become increasingly urgent. Many governmental and regulatory bodies are now recognizing this need particularly for diesel engines.
Diesel exhaust includes Nitrogen Oxides (NOx), Carbon Monoxide (CO), and fine particulates, including unburned hydrocarbons, commonly referred to as “soot”. These contaminants cause a multitude of serious health issues when inhaled into the lungs, including respiratory infections, asthma, emphysema, and cancer.
The poisonous chemicals found in diesel exhaust soot can lodge deep into the lungs, bypassing the natural defenses of the body due to their small size (less than 2.5 micrometers in diameter). There they impair the healthy functioning of the lungs, and aggravate respiratory diseases such as asthma, bronchitis, and emphysema. Many studies also link these airborne fine particles to chronic obstructive lung disease, pneumonia and heart disease. In urban areas, studies suggest that diesel exhaust may contribute to as much as 70 percent of the cancer risk from toxic air pollution which would make diesel emissions more harmful than all other toxic air contaminants combined (1).
Ground-level ozone, caused when nitrogen oxides (NOx) and hydrocarbons from combustion combine, is also a powerful respiratory irritant. It causes shortness of breath, chest pain, wheezing, coughing, and exacerbation of respiratory illnesses. Long-term and repeated exposures may lead to large reductions in lung function and inflammation of the lung lining.
Children, residents of urban areas and the elderly are particularly vulnerable to the effects of soot. Children have immune and respiratory systems that are still developing, and breathe up to 50 percent more air per pound of body weight than adults. Breathing in soot from diesel exhaust can cause both acute and chronic respiratory problems such as asthma. Asthma is the most common chronic illness among children and the leading cause of school absenteeism (2). The elderly and others with weakened immune systems or health problems such as cardiopulmonary diseases, are also especially affected by diesel soot.
In the U.S. alone, thousands of premature deaths occur each year as a result of the combination of these health factors. Regulators, notably in California among other authorities, are responding with stricter emissions standards.
Diesel emissions also affect the health of the environment on a broader scale. Diesel exhaust includes:
- Nitrogen oxides (NOx), which combines with hydrocarbons to form ground-level ozone, which forms smog. NOx emissions are also a major cause of acid rain, as the nitrogen oxide oxidizes in the air and forms nitric acid (HNO3).
- Sulfur oxides (SOx), is also a cause of acid rain as it combines with hydrogen-oxygen molecules in the air to form sulfuric acid (H2SO4). Low-sulfur and ultra-low-sulfur fuels now in common use in North America and Europe have helped to reduce this problem, however it remains an issue worldwide.
- Carbon dioxide (CO2), is a major greenhouse gas widely acknowledged to be contributing to global climate change.
Cancer Risk Assessment Map
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