Dj. Paustenbach et al., URINARY CHROMIUM AS A BIOLOGICAL MARKER OF ENVIRONMENTAL EXPOSURE - WHAT ARE THE LIMITATIONS, Regulatory toxicology and pharmacology, 26(1), 1997, pp. 23-34
Public concern has mounted recently about environmental exposures to c
hromium in soil, tap water, and ambient air. In response, agencies cha
rged with protecting public health have attempted to study exposure by
monitoring urinary chromium levels among potentially exposed populati
ons. While urinary biomonitoring of occupationally exposed workers has
been successfully used to assess high-level inhalation exposures in t
he workplace, evaluating low-level environmental exposures has been pr
oblematic. Due to these problems, before an extensive biological monit
oring study is conducted of those exposed to low levels of environment
al chromium, several issues must be resolved. First, exposures to chro
mium must occur at the same time as sampling, because the biological h
alf-life of chromium in urine is very short (less than 2 days). Second
, reduced bioavailability and bioaccessibility via the oral and dermal
routes of exposure limit the capacity of urinary monitoring to measur
e environmental exposures (e.g., systemic dose is too small to be meas
ured). Third, the dose of chromium must be sufficient such that it may
be reliably measured above background levels in urine (range of 0.2 t
o 2 mu g/liter) and above the analytical limit of detection (0.2 mu g/
liter). Fourth, the inter-and intrapersonal variability in background
levels of urinary chromium is known to be significant and influenced b
y food and beverage intake, smoking, and exercise. Thus, the role of e
ach factor must be carefully understood. Finally, it is imperative to
have developed a complete understanding of the clinical significance o
f elevated urinary chromium levels before a study is performed, becaus
e higher than background levels, in and of themselves, are not indicat
ive of a significant health concern. The route of exposure, valence of
chromium to which people were exposed, exposure time, and duration mu
st all be understood before the biological data can be implemented. We
have conducted a total of nine human exposure studies over the past 3
years in an attempt to understand the kinetics of chromium and the im
pact on urinary, red blood cell (RBC), and plasma biomonitoring progra
ms. The results of these studies are described here and our recommenda
tions are offered for how to design and implement a urinary chromium b
iomonitoring study. In our view, given some evidence that the dose of
hexavalent chromium [Cr(VI)] is sufficient to be measurable above back
ground concentrations of total chromium [Cr(III) and Cr(VI)], duplicat
ed measurements of chromium in plasma and RBCs are, in most cases, a m
ore definitive gauge of environmental exposure than urinary biomonitor
ing. (C) 1997 Academic Press.