Freeway Air Pollution Triggers ‘Fight Or Flight’ Response In Human Body

Scientists have known for quite some time that highway air pollution has many harmful effects. As we noted a few weeks ago, it can cause premature births and DNA damage. Also among the established effects are heart attack and stroke. But a new study sheds light on what’s actually happening, and why pollution causes high blood pressure. The culprit, it turns out, is the small particulate stuff spewed out in large quantities by trucks.

An article in Time today announces the findings:

Scientists at the University of Michigan, led by Dr. Robert Brook, found that [polluted air] can increase your blood pressure, and cause unhealthy changes in your blood vessels that last for hours and perhaps even days. […] [Study] participants were exposed in the lab to the same amount of particulates and ozone that would be found near a local highway. People who breathed in polluted air registered higher blood-pressure readings a short time after exposure and their blood vessels showed impairment as long as 24 hours later.

The scientists developed a rather granular, so to speak, understanding of what’s happening in these cases–the air pollution is, oddly enough, automatically setting off a fear reaction in the body:

First, the fine matter triggers changes in the central nervous system, causing a switch from the more controlled regulation of body processes to a more instinctive, automatic fight-or-flight response. This revs up the heartbeat and causes blood pressure to spike as the body may be responding to the presence of foreign, potentially dangerous particles in the air.

It’s all fairly graphic stuff, and the effects are persistent:

Once the immediate onslaught of pollution is gone, blood pressure drops back down. But the damaging effects persist. Particulates can lodge deep in the lungs, where they activate another process - inflammation, which kicks in over the 24 hours after exposure. The inflammatory response can stiffen blood vessels and cause longer-term damage to blood-vessel flexibility and their ability to absorb changes in blood flow from the heart. Weakened blood vessels can increase the risk of heart disease or stroke.

Now, of course, the point is not to rev up urban hypochondriacs into an inconsolable tizzy. Most healthy people can deal with this kind of low-grade physical stress. But a lot of people–young, old, infirm, or simply vulnerable for whatever reasons–can’t, and the fact remains that the more we understand, the worse this stuff seems to be. Regulations and pollution trends are moving in the right direction, fortunately. But the steady trickle of unnerving studies like this is just impetus to move that process along faster.