Air pollution promotes constant cold

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Fine dust, soot, exhaust gases - there are many pollutants in the air. These irritate not only the eyes and the lungs, but also the nose. With unpleasant consequences: a runny, blocked nose, headaches and a feeling of pressure on the face at any time of the year.

Studies show that chronic inflammation of the nose and sinuses, also called chronic rhinosinusitis, often occurs when there is high air pollution. But the exact mechanisms behind it were so far unclear. Murugappan Ramanathan of the Johns Hopkins University School of Medicine in Baltimore and his colleagues have now examined them.

16 weeks of thick air

To do this, the researchers exposed 19 mice to polluted air - for 16 weeks, six hours a day. During this time, the animals inhaled concentrated Baltimore air: the researchers had enriched them to 61 micrograms of particles per cubic meter and processed them so that they only contained particles with a maximum size of 2.5 micrometers. This is so tiny that most allergens such as pollen or dust particles could not be found in the animals' breath.

Despite this considerable particulate matter load, the air still contained 30 to 60 percent fewer particles during the experiment than the air in New Delhi, Cairo or Beijing. As a control, the researchers also kept 19 mice in filtered air. All mice were allowed to breathe fresh air two days a week.

To what extent the pollution affected the upper respiratory tract of the mice, the researchers examined by rinsing the animals' noses and sinuses with water so that the cells could be examined under a microscope.

Inflammatory cells on the rise

In the samples from mice that had inhaled polluted air, they found a significantly increased number of white blood cells. This is a clear indication of inflammation.The number of phagocytes - the white blood cells that destroy pathogens and foreign bodies for the immune system - was almost four times as high as in the mice that were kept in filtered air.

In addition, the scientists discovered that the fine dust mice had concentrations of cytokines that were five to ten times higher. These chemical messengers play an important role in inflammation because, among other things, they attract a certain form of white blood cells, the eosinophils. These in turn fulfill important tasks in the immune system, but are also involved in the development of asthma. "Chronic exposure to air pollution triggers a kind of asthma of the nose in mice," says Ramanathan, summarizing the mechanism.

Thick epithelium as a marker of inflammation

The researchers also looked at the epithelial cells of the nasal passages and sinuses under the microscope. This is the outer layer of the mucous membrane cells. They found that the epithelium in the fine dust mice was 30 to 40 percent thicker than in conspecifics who had only breathed filtered air. This is another sign of inflammation, said Ramanathan.

In addition, air pollution caused so-called protein serum albumin to rise. This is proof that the mucous membrane barriers in the nasal passages and sinuses were attacked.

Damaged barrier

"We have found a lot of evidence that inhaling polluted air has a direct negative impact on the integrity of the nasal passages and sinuses," says Ramanathan. However, keeping this barrier functional is essential in order to protect the cells of the tissue from irritation and infection, for example To protect pollen or germs.

Chronic sinusitis is when the cold persists for twelve weeks. In addition to a runny or blocked nose, many sufferers also have headaches, as well as pain and a feeling of pressure below the eyes. Numerous studies also suggest that chronic runny nose severely affects the quality of life. Depression, social isolation, and chronic fatigue can all result.

Sources:

Press release from Johns Hopkins Medicine of April 18, 2017: Air Pollution May Directly Cause Those Year-Round Runny Noses, According to a Mouse Study

Murugappan Ramanathan et al .: Airborne Particulate Matter Induces Non-allergic Eosinophilic Sinonasal Inflammation in Mice. American Journal of Respiratory Cell and Molecular Biology. DOI: 10.1165 / rcmb.2016-0351OC

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