Study on toxic exposures in urban en...( y designed backpack with a battery-oper...),Health

Comparing the samples collected from each of these locations showed that the vast majority of the personal samples had higher Fe, Cr and Mn levels that could not be explained by levels observed inside of the subjects' homes or in outdoor locations. Looking at elemental ratios allowed the team to conclude that while the indoor and outdoor samples appeared to obtain their Fe and Mn primarily from re-suspended dirt particles, the personal samples were primarily exposed to a single type of steel that was ground into a fine dust. This was evident since both Fe and Cr concentrations had a strong tendency to follow Mn concentrations and the personal ratios of these metals, that is the Fe to Mn and Cr to Mn ratios were significantly different from the ratios naturally found in dirt. Several clues made the research team suspect the subway system as a potential source of the steel dust. For example, the data from the winter samples showed that all of the students who had to commute a long distance to school were included in the group with the elevated levels of Fe, Mn and Cr. During the summer, when the students were not commuting to school, the geographic pattern of elevated levels was more random.

The subway hypothesis was tested by sending a Columbia University student underground with two personal monitoring pumps and a particle counter for a total of eight hours. The airborne levels of Fe, Mn, and Cr in these two subway samples were more than two orders of magnitude higher than indoor and outdoor levels measured in the TEACH study. Just as important, the samples collected by the student backpacks had the same 'source signature' as the samples collected during the subway study in that they had the same ratio of Fe to Mn and Cr to Mn.

"All indicators for the increased exposure levels point to the
'"/>


5-Jan-2004