The U.S. Environmental Protection Agency (EPA) regards diesel exhaust as one of the greatest public health risks. Exhaust from diesel engines contains many toxics and can be inhaled into the deepest parts of the lungs where it can enter the bloodstream. It is attributable to an increase in premature death, asthma attacks, and emergency-room visits and can exacerbate the symptoms of asthma as well as other chronic obstructive pulmonary diseases, including bronchitis and emphysema.  Scientists and health experts have been unable to identify a safe level of exposure to diesel exhaust, or a level below which exposure has no health effects.  The 2020 State of the Air Report, published by the American Lung Association, stated that there were 162,556 children with asthma, 442,787 adults with asthma, 361,074 persons with chronic obstructive pulmonary disease (COPD), and 3,938 persons with lung cancer within the Dallas-Fort Worth region, all of which are at risk of having exacerbated health problems due to excessive air pollution. 
In addition to particulate matter and air toxics, the EPA affirms that diesel exhaust is a major contributor to ozone formation due to excess emissions of NOx. Prolonged exposure to ozone can also have adverse health impacts, such as irritation of the airways and reduced lung function. It can also be attributable to coughing, irritation of the throat and chest, and an inability to breathe as deeply or vigorously as normal.