Environmental Engineering Reference
In-Depth Information
induce inflammation, which does not occur with metallic Pt. This effect has no
consequence for the allergenic potential of Pd, or its compounds, which are
absorbed via the respiratory tract. Notwithstanding, recent studies indicate that the
allergenic potential of Pd compounds may have been underestimated (Schuster et al.
2000). A case of Ir allergies from occupational exposure was also reported
(Merget and Rosner 2001; Ravindra et al. 2004; Cristaudo et al. 2005).
Pt was found not only in the blood and urine of occupationally exposed persons,
but also in the body fluids of individuals who were not occupationally exposed.
Average levels of 0.6 ng L
−1
were found in blood of people living in Sydney,
Australia (Vaughan and Florence 1992). Benemann et al. (2005) tried to identify
and quantify the main exposure pathways of gold and Pt in the general adult popu-
lation. Their studies were based on results obtained from the analysis of urine
samples collected from 1,080 people aged 18-69. The results of these studies were
that exposure correlated with the number of teeth that had noble metal dental alloy
restorations.
A growing point of interest among scientists is the recent observation that small
amounts of Pt have been found in silicone implants. Concerns have been raised that
Pt may enter the body and cause adverse effects, by diffusing either through the
intact implant shell or from an implant rupture. The recent data demonstrate that Pt
leaks from intact implants and accumulates in lipid-rich fat or fibrous tissues
(Maharaj 2004). Although the appearance of Pt residues in tissues is a good indica-
tor for defective implants, there is no certainty that it causes health problems in
women with implants (Flassbeck et al. 2003).
6
Concentration Levels of PGEs in the Environment
Scientists have warned that PGEs may negatively affect human health, not only
from direct exposure via road dust and inhalation of airborne particles (about 30%
of particles emitted from car catalytic converters are <10 µm in diameter, and are
inhalable) (Gomez et al. 2001), but also through consumption of food and water
(Rosner and Merget 2000; Artelt et al. 1999b). Therefore, it is important to define
the human health risks associated with the presence of PGEs in the workplace;
environmental monitoring of these elements at their emission sources is needed.
Bosch Ojeda and Sanchez Rojas (2007) have reported a trend toward PGEs
increasingly being discovered in environmental samples. Rh, Pd, and Pt are known
to accumulate in soils along roadsides. From the results of Morton et al. (2001), we
clearly see that PGE concentrations in soils exposed to high traffic densities signifi-
cantly exceed natural background values. The minor, but nonetheless significant,
accumulation of Ir in soils is strong evidence of its increasing use in catalytic converters
(Fritsche and Meisel 2004). Scientific results indicate that PGE concentrations in
roadside soils are directly influenced by traffic conditions and are proportionate to
distance from the road. The research of Morcelli et al. (2005) shows that the pattern
of PGE residue distribution in roadside soil was similar to that of other traffic-related
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