Cm. Shy, EPIDEMIOLOGIC STUDIES OF NEUROTOXIC, REPRODUCTIVE, AND CARCINOGENIC EFFECTS OF COMPLEX-MIXTURES, Environmental health perspectives, 101, 1993, pp. 183-186
Neurotoxic, reproductive, and carcinogenic effects are potentially imp
ortant health end points in epidemiological studies of complex mixture
s, particularly when such mixtures contain volatile organic compounds
or trace metals. Epidemiological studies of neurotoxicity often will r
equire direct clinical, behavioral, and/or physiological testing of st
udy subjects, because these effects are likely to be subtle and not id
entifiable as clearly defined diseases. Peripheral nervous system toxi
city can be assessed by clinical neurologic examinations, by electroph
ysiological tests of nerve conduction, and by physiological tests of t
hresholds for neurosensory perception, though these tests require cons
iderable standardization for use outside the clinical setting, and mos
t of the available tests have not been assessed for their utility in d
etecting effects of neurotoxic exposures. Neurobehavioral effects of e
xposures to solvents, as examples of complex mixtures, have been studi
ed widely; but batteries of tests are often used, and these have not b
een well standardized and are generally unfamiliar to most research in
vestigators in this area. Recently standardized neurobehavioral test s
ystems developed by the World Health Organization and by a U.S. group
for use in field studies, show promise in detecting neurobehavioral ef
fects at relatively low environmental exposures. Similarly, new and se
nsitive measures of disturbed reproductive function, such as time-to-c
onception and biochemical indices of early pregnancy loss, are affecte
d by some low-concentration environmental agents; but those measures h
ave not yet been applied to studies of complex mixtures. Because of th
e long latency problem and small expected relative risks, population-o
r community-based studies of the carcinogenic effects of complex mixtu
res are unlikely to yield data of adequate quality to justify more tha
n exploratory studies of carcinogens in ambient air.