revised final - Agency for Toxic Substances and Disease Registry ...

MERCURY
2. HEALTH EFFECTS
A worker (age, mid-40s) exposed to mercury in a thermometer factory for approximately 3.5 years
experienced acute, intermediate, chronic, and delayed neurological effects (White et al. 1993). During his
employment, he performed a variety of functions, including sweeping mercury off floors with a vacuum
cleaner or hose blower, repairing and cleaning machines, disassembling machines containing mercury, and
operating a machine that crushed instruments so that he could then separate the mercury from other
materials for reuse. From approximately the beginning of his employment at the factory, he experienced a
number of symptoms, including blurred vision, ocular pain, rash, a strange taste in the mouth, weakness,
memory loss, rage, and irrational behavior. The month following his release by the factory, his urine
mercury concentration was measured at 690 µg/L, which confirmed a diagnosis of mercury poisoning. He
was treated by chelation with penicillamine over a 2-month period; approximately 2 months after the
completion of treatment, his urine mercury level was only 17 µg/L. Approximately 21months after
termination of his employment, neurological examination revealed nystagmus on upward gaze, bilateral
manual tremor, diminished sensation to pain, peripheral neuropathy, and abnormalities in nerve conduction.
An magnetic resonance imaging (MRI) examination revealed mild central and cortical atrophy, with
punctiform foci of T2 in both frontal regions, especially underlying the precentral gyri and in the white
matter (both subcortical and gyri). The MRI data were interpreted as consistent with diffuse and focal
white matter disease. Neuropsychological testing conducted during the same time period revealed problems
with cognitive function, fine manual motor coordination, visuospatial analysis and organization, memory
for visuospatial information, affect, and personality almost 2 years after cessation of employment at the
factory.
In contrast with the long-term (perhaps permanent) effects noted in the previous study, Yang et al. (1994)
reported that recovery from chronic elemental mercury intoxication may be complete when patients are
removed early from the exposure environment. A 29-year-old worker in a Taiwanese lampsocket­
manufacturing facility, with an initial urinary mercury concentration of 610 µg/L (in a 24-hour sample) and
a blood mercury concentration of 237 µg/L (reference range,