The immediate effects of air pollution are hard to ignore. Watery eyes, coughing and difficulty breathing are acute and common reactions.

An estimated 92 percent of the world’s population live in areas with dangerous levels of air pollution and, even at seemingly imperceptible levels, air pollution can increase one’s risk of cardiovascular and premature death.

Air pollution is almost as deadly as tobacco. In 2016, it was linked to the deaths of 6.1 million people, according the University of Washington’s Institute for Health Metrics and Evaluation.

And it might harm you even before you take your first breath.

Exposure to high levels of air pollution during pregnancy has been linked to miscarriages as well as premature birth, autism spectrum disorder and asthma in children.

Air pollution may damage children’s brain development, and pneumonia, which kills almost 1 million children under the age of 5 every year, is associated with air pollution. Children who breathe in higher levels of pollutants also face a greater risk of short-term respiratory infections and lung damage.

Other conditions associated with high levels of air pollution include emphysema and chronic bronchitis, as well as lung cancer.

Pollutants can affect cardiovascular health by hardening the arteries and increase the risk of heart attack and strokes, and there is even emerging evidence that air pollution may be linked to mental health conditions and degenerative brain diseases such as Alzheimer’s disease, Parkinson’s disease and schizophrenia.

How Air Pollution Damages The Body

While air pollution’s link to respiratory disease may seem obvious, its relationship to heart, brain and fetal health is less so. There are at least two possible mechanisms by which air pollution can harm parts of the body besides the nasal cavity and lungs, said Anthony Gerber, a pulmonologist at National Jewish Health in Denver.

The first has to do with inflammation, which is the body’s way of repairing itself after an injury or illness.

When the toxic soup of chemical particles and liquid droplets emitted by cars, power plants, fires and factories known as particulate matter is inhaled, the microscopic toxic dust can irritate nasal passages and result in an allergic-type response to the pollution, with symptoms like coughing and a runny nose.

Scientists believe that as the particles make their way deeper into the airways and into the lungs, the body may mistake it for an infection, triggering an inflammatory response.

“When you have a bad head cold, you feel sick everywhere and your muscles might ache,” Gerber said. “The same thing can happen when you breathe in pollution.”

Scientists also suspect that some toxic particles can escape the lungs and enter the bloodstream.