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MERCURY 317
2. HEALTH EFFECTS
Other potential biomarkers of exposure include renal dysfunction parameters, neurological effects, and
increased urinary porphyrins, and are discussed below in Section 2.7.2.
2.7.2 Biomarkers Used to Characterize Effects Caused by Mercury
Several potential biomarkers of effect for mercury have been evaluated, usually for neurological and renal
dysfunction. Many of these toxic effects have been correlated with blood and urine levels (see
Table 2-13). However, most indicators are nonspecific and may have resulted from other influences. As
discussed in Section 2.2, many studies have examined the relationship between urine mercury levels and
specific renal and neurological effects. Renal dysfunction has been studied extensively as a potential
sensitive measure of mercury exposure. Signs of renal dysfunction at mercury air concentration of
0.1 mg/m 3 were reported by Stewart et al. (1977). Case reports have associated the therapeutic use of
inorganic mercury salts with the occurrence of nephrotic syndrome (Kazantzis et al. 1962).
Several different biomarkers have been evaluated for assessing renal damage; however, renal parameters
are interdependent (Verschoor et al. 1988). Furthermore, these markers are not specific for mercury
exposure and may be a consequence of other concurrent chemical exposures. Markers for renal toxicity
may indicate decreased function, cytotoxicity, or biochemical changes (Cardenas et al. 1993). Biomarkers
for decreased function include increases in urinary proteins and elevation of serum creatinine or
β2-microglobulin. Biomarkers for renal cytotoxicity include increases in urinary excretion of antigens and
enzymes located within renal tissues. Biomarkers for biochemical changes occurring within the kidneys
include eicosanoids, fibronectin, kallikrein activity, and glycosaminoglycans in urine. Glomerular changes
resulting from mercury exposure have predominantly been reported as increases in high-molecular weight
proteinuria (Buchet et al. 1980; Kazantzis et al. 1962; Stonard et al. 1983; Tubbs et al. 1982). Renal
tubular changes in workers exposed to mercury include increased urinary excretion of N-acetylβ-D-glucosaminidase
(NAG), β-galactosidase, and retinol binding protein (Barregard et al. 1988;
Langworth et al. 1992b; Rosenman et al. 1986). Elevated urinary NAG levels occurred with urinary
mercury levels of 100–250 µg/L in a study population of mixed ethnic background (Rosenman et al.
1986), with urinary levels of 35 µg/g creatinine in chloralkali workers (Barregard et al. 1988), with urinary
mercury levels >25 µg/g creatinine in chloralkali workers (Langworth et al. 1992b), and with urinary
mercury levels >50 µg/g creatinine in another group of chloralkali workers (Cardenas et al. 1993). NAG
levels were not affected in chloralkali workers with urinary mercury levels of 15 µg/g creatinine (Piikivi
and Ruokonen 1989). No significant increase of proteinuria, albuminuria, and other indicators of renal