Air pollution
One possible source of PHM is the fine particulate matter component of
air pollution from burning fossil fuels. In many studies, microbes are
only identified to the genus level. Interestingly, studies of crude oil
reveal diverse microbiotas, including at least some genera that are the
same as those found in humans, such as Pseudomonas and Mycobacteria. It
seems possible that some studies might fail to detect microbes
originating from fossil fuels.
A recent study found the proportion of pathogenic species increased with
air pollution levels associated with urbanization[14]. A study also
found that there were changes in the pharyngeal microbiota following a
severe air pollution event, including detection of 142 new genera in the
pharynx[15]. Some of the microbes found in cigarette smoke also
might be considered to be PHM and might play a role in
tobacco-associated diseases.
A number of studies have linked fine particulate matter exposure to
increased rates of allergic diseases[1]4, respiratory
infections[16] and overall mortality[17]. Air pollution has been
associated with evidence of stress effects as measured by blood
pressure, heart rate, and heart rate variability.