Inhaling polluted air damages intestinal bacteria, increases the risk of obesity, diabetes, stomach and intestinal problems and other chronic diseases, the University of Colorado in Boulder found.
The study, published in the scientific journal Environment International, is the first to find a link between contamination and changes in the structure and function of the human gut microbiome.
The intestinal tract is home to many bacteria. It is my gut microbiome, that is, the totality of the myriad microorganisms that live here that aid digestion and interact with the immune system.
Gaseous pollutant ozone is particularly dangerous because, according to the study, young adults who are exposed to more ozone have less microbial diversity and have more bacterial species associated with obesity and disease.
“We know from previous research that air pollutants have a whole range of health effects,” said Tanya Alderete, lead author of the research, referring to studies that have linked smog to type 2 diabetes, obesity and inflammatory bowel disease. According to the expert, the results of the research suggest that changes in the intestine cause diseases.
The study couldn’t be more topical: air quality in U.S. cities began to deteriorate again after decades of improvement. Regions in several states in the country – California, Texas, Illinois, Connecticut, Indiana, New Jersey, New York and Wisconsin – have also been penalized for excessive ozone levels for failing to comply with national limits.
According to a study published this month, polluted air kills 8.8 million people worldwide each year, more than smoking or wars.
According to Alderete’s previous research, air pollution impairs the body’s ability to regulate blood sugar levels and affects the development of obesity. Other studies show that on days with high levels of air pollution, the number of people admitted to hospitals due to intestinal and stomach problems increases.
To find out what’s going on in the gut, Alderete’s research team analyzed the stool samples of 101 young adults in Southern California using the most advanced genome sequencing methods.
The scientists also analyzed data from air monitoring stations near the people’s homes to calculate the amount of ozone, particulate matter and toxic nitrous oxide from burning fossil fuels in the year before the study.
Of the pollutants studied, ozone has the greatest effect on the intestinal tract: those who have been exposed to higher levels of ozone have experienced less bacterial variation in their intestinal system.
“This is very important because decreased bacterial diversity can be linked to overweight and type 2 diabetes,” Alderete noted.
One special bacterial species, Bacteroides caecimuris, on the other hand, is found in larger amounts in the intestines of those who inhale more ozone. The growth of this bacterium has been linked to overweight, according to several studies.
A total of 128 bacterial species were found to be negatively affected by ozone exposure. Some, for example, affect insulin secretion – this hormone that transports sugar to the muscles.
Other bacterial species produce metabolites, such as fatty acids, that help maintain the integrity of the intestinal tract and prevent inflammation.