A prior study in New York City observed that airborne concentrations of three metals
found in steel - iron, manganese, and chromium - are more than 100 times higher in
the subway system than in aboveground air. To investigate the potential for health
effects of exposure at these levels, we conducted a pilot study of subway workers
comparing personal exposures to steel dust with biomarkers of metal exposure, oxidative
stress, and DNA damage in blood and urine samples. Workers wore a personal air sampler
operating at 4L/m for one to three work shifts with blood and urine samples collected
at the end of the final shift. We found that PM(2.5) exposures varied among subway
workers on the basis of job title and job activity. The subway workers' mean time-weighted
PM(2.5) exposure was 52 microg/m3, with a median of 27 microg/m3, and a range of 6-469
microg/m3. The observed concentrations of PM(2.5), iron, manganese, and chromium fell
well below occupational standards. Biomarker concentrations among the 39 subway workers
were compared with a group of 11 bus drivers, and a group of 25 suburban office workers.
Concentrations of DNA-protein crosslinks and chromium in plasma were significantly
higher in subway workers than in bus drivers, but no significant difference was observed
for these biomarkers between subway workers and office workers. Urinary isoprostane
concentrations were significantly correlated with the number of years working in the
subway system, and were detected at higher, though not significantly higher, concentrations
in subway workers than in bus drivers or office workers. At the group level, there
was no consistent pattern of biomarker concentrations among subway workers significantly
exceeding those of the bus drivers and office workers. At the individual level, steel
dust exposure was not correlated with any of the biomarkers measured.