Metal exposure for residents near diesel transport routes.
For the past few years, a large number of diesel vehicles carrying gravel and sand have shuttled back and forth every day on the main route (Tai-16 and Tai-21 highways) from Shuili to Shinyi in Nantou County, Taiwan, in support of a river-dredging project. Five stations along Tai-16 and three stations along Tai-21 were selected as the exposure sites. Two very small villages located about 9 and 12 kilometers, respectively, away from the diesel transport routes were selected as the control sites. In this study, five exposure pathways, i.e., ingestion from drinking water, household dust, rice, non-rice dishes, and inhalation from airborne particles, were considered. The daily intake doses of metals varied significantly among the five exposure pathways. There was a significant difference between the exposure and control sites regarding the doses of metals obtained from the exposure pathways of household dust and aerosols. However, regarding the exposure pathways of rice, non-rice dishes, and drinking water, no significant difference between the exposure and the control sites was observed for most metals. Residents who lived within 30 meters of diesel transport roads at the exposure sites were selected as the exposure groups for urine sampling, while residents of the control sites were selected as the control groups. The metal concentrations in the urine of the exposure groups were all higher than those of the control groups. With regards to the urinary metals Fe, Pb, Cu, Ni, and Mo, the levels of urinary metals in residents and the daily intakes of metals from the five exposure pathways showed that the exposure pathways from environmental media (i.e., drinking water, aerosols, and household dust) were a greater factor than food pathways (i.e., rice and non-rice dishes) in the resulting comparative differences between urinary concentration levels of Fe, Pb, Cu, and Mo in exposure groups and control groups. However, the food exposure pathways, rather than the environmental pathways, led to greater comparative differences between the urinary concentration levels of Mn within the two groups.