Pollution Messes with Metabolism

Air pollution is not good for lungs. Just ask anyone in Beijing where surgical masks are a fashion accessory.

How bad is air pollution? The World Bank reported in 2010 that 16 of the world’s top 20 most polluted cities are in China. Linfen City in Shanxi Province, China, which is known for its coal industry, was the world’s most polluted.

Developed countries are polluted too.

Despite decades of cleanup measures, the American Lung Association State of the Air 2012 revealed that nearly half the population of the United States still suffers pollution levels that are often dangerous to breathe. The report found that unhealthy air posed a threat to the lives and health of more than 127 million people—roughly 41 percent of the nation. Even cities like Salt Lake City, Utah, and North Pole, Alaska, which sound pristine, are choking with pollution—the first from automobiles and industry and the latter from burning coal and wood for warmth. At times the air quality readings in North Pole are twice as bad as that of Beijing, according to Kim Murphy writing in the Los Angeles Times in 2013.

Air is judged by ozone and particulate matter. Greenhouse gases including carbon dioxide, methane, and nitrous oxide are bad for respiratory systems, according to the EPA. But a new slyer villain has emerged: the small bits, called particulate matter (PM).

According to the World Health Organization, PM affects more people than any other pollutant. PMs are a jumble of solids, liquids, and organic and inorganic matter: mostly sulfate, nitrates, ammonia, sodium chloride, carbon, mineral dust, and water. The smaller ones at 2.5 µm are most dangerous because they easily invade the lungs.

And as you may have guessed by the recipe, these PM2.5s, which emerge from burning fuels, are linked to asthma, lung cancer and other respiratory diseases. People exposed to pollution don’t live as long. The mortality in cities with high levels of pollution exceeds that observed in relatively cleaner cities by 15 to 20 percent.

The link to obesity is new. How could this happen? The idea is that PM contributes to insulin resistance and adipose inflammation. In one experiment, mice exposed to PM2.5 showed insulin resistance and more visceral fat and inflammation among other defects.

In a new study published in Particle and Fibre Toxicology journal, special mice susceptible to Type 2 diabetes were exposed to either ambient PM2.5 or filtered air for 5 to 8 weeks.

Results:

  • O2, Co2, respiratory exchange and thermogenesis were all changed.
  • More insulin resistance
  • More visceral fat
  • More inflammation in spleen and visceral fat
  • Leptin levels increased
  • Gene expression in brown adipose tissue changed.

Air pollution may be adding to our obesity and diabetes numbers. Choking  on this epidemic is not an option.