Troopers spending long shifts in their patrol cars may be more vulnerable to heart problems stemming from traffic pollution, a new study shows.

The possible risk was noted in a small study of nine healthy male highway patrol troopers in North Carolina’s Wake County. All were nonsmokers aged 23-30. They abstained from alcohol, caffeine, and medications for the four-day study, plus an extra day before the study began.

The officers’ patrol cars were equipped with air monitors and their heart rates were tracked while they worked. The policemen also provided blood samples after their shifts to look for blood levels of inflammation markers, which are linked to heart disease risk. The researchers also looked at blood clotting factors associated with higher risks of heart attacks.

The data was reviewed by researchers including Michael Riediker of Switzerland’s Institute of Occupational Health Sciences. Switzerland is a long way from North Carolina, but it’s not the first time Riediker has focused on American officers.

Previously, Riediker noticed signs of inflammation, increased clotting, and abnormal heart rate changes among highway patrolmen exposed to small-sized air pollutant particulates. Studies have shown that exposure to fine particulate matter increases daily death rates and hospitalizations for heart disease.

Now, he and his colleagues report that speed-changing traffic — traffic in which cars speed up and slow down — generated the most heart-damaging fine particulate matter for these troopers.

Riediker’s study showed that the troopers’ exposure to air pollutants affected heart rhythm and was associated with an increased frequency of abnormal heartbeats. It also showed that fine particulate matter, originating from speed changing, elicited changes in clotting and inflammatory markers in these healthy young men.

Speeding up and slowing down kicks up the worst pollution, Riediker’s team notes. Brake use gives off copper, fuel combustion by engines emits fine particles, and sulfur is generated by secondary aerosols and perhaps also from accelerating diesel trucks.

You don’t have to stand on the side of a highway to inhale fine particulate matter. It can also be found inside moving vehicles. Fine particles generally come from vehicle exhaust, industrial processes, and residential fireplaces and wood stoves.

An estimated 800,000 deaths worldwide per year are due to fine particulate matter, say the researchers in the journal Particle and Fibre Toxicology.

The study only had a handful of participants, tracking them for just a few days. That’s probably too short to draw conclusions about the long-term consequences of fine particulate matter from vehicle exposure. Most drivers spend far less time in their cars than highway patrolmen, so their exposure to traffic pollutants may differ from the moderate levels seen in the study.

By Miranda Hitti, reviewed by Brunilda Nazario, MD

SOURCES: Riediker, M. Particle and Fibre Toxicology, Dec. 9, 2004; vol 1. News release, BioMedCentral.