Skip to main content
Facebook PageDonate   EAA YouTube Channel
HomeEVAOSD Tailpipe Doc

What comes out of a tailpipe anyway?






  • NOx 

  • HC Hydrocarbons ,  

  • SO2 Sulfur Dioxide  

  • PM10, 2.5 

  • Benzene, other Aromatics 

Particulate Matter especially harmful for children and the elderly 

Human Health Effects
Lung cancer
Respiratory diseases
Premature deaths

ER visits
Lost days of work
Medical treatments
Loss of life

Driving one average car in the U.S. (12,000 miles at 25 mpg)
costs approximately 
$10,000/year to treat the diseases caused by these toxins.*



*American Lung Association State of the Air Report 2017



NOx (nitrogen oxides)

This is the nasty stuff that many diesel Volkswagen cars were emitting at up to 40 times the legal limit before the company got caught by regulators, and it has two problematic effects. First off, when inhaled, NOx can damage your lungs and increase your risk of respiratory infections. Long-term exposure can even lead to the development of asthma. Second, NOx interacts with other chemicals coming out of your tailpipe and in the air to create dangerous particulate matter — which we will cover in a bit — and smog.

HC (Hydrocarbons)

HC+NOx+sunlight=ozone. Now, ozone is a good thing in the upper atmosphere because it protects us from radiation from space. However, at ground level it’s problematic, causing lung issues and contributing to smog creation.

SO2 (Sulfur dioxide)

Even limited exposure to SO2 can make it hard to breathe and can hurt your respiratory system, especially if you’re very young, elderly, or have asthma. This chemical also contributes to particulate matter formation.

CO (carbon monoxide)

Concentrations can get high enough outdoors to pose problems to people who have heart disease or are exercising.

PM10, 2.5 (Particulate matter)

While some of the larger particles (PM10), aren’t overly harmful, smaller particles like PM2.5 and below can cause major health issues. Why? Because once PM gets small enough it can pass through the walls of your lungs into your bloodstream or through your olfactory nerve and into your brain. In your bloodstream, it can, according to the EPA cause “premature death in people with heart or lung disease, nonfatal heart attacks, irregular heartbeat, aggravated asthma, decreased lung function, increased respiratory symptoms, such as irritation of the airways, coughing or difficulty breathing.” In addition, there is a growing body of research that suggests PM exposure to the brain is harmful to the very young and the elderly by increasing the buildup of plaque. In the elderly this may increase the risk of dementia and accelerate cognitive decline. For babies in the womb, exposure may increase the risk of autism and ADHD. And with children it may contribute to neurobehavioral problems and lower IQ. Of all forms of air pollution, PM is arguably the most problematic and damaging.

Benzene and company (Aromatics)

When lead was phased out due to its myriad of damaging health effects, benzene and other aromatics like xylene and 1,3-butadiene began to be added to gasoline to replace lead as an octane booster. Benzene is a known carcinogen and is not safe to be exposed to.