Handbook of Solvents - George Wypych - ChemTech - Ventech!

1408 Kaye H. Kilburn
Sensitivity’s main dimensions are time and mapping. For example, balance is measured
using the classic Romberg stance (1850) standing feet together with eyes ahead open
and then closed and using a force (displacement) platform or even simpler the position of
the head from a sound emitter secured to a headband and recorded by two microphones to
inscribe the distance swayed and the speed, in centimeters per second. 19 From three performances
for 20 seconds with the eyes closed alternating with the eyes open the minimal
speed of sway is selected. The inscribed path, the map, may provide more information but
how to interpret this is unclear.
Eye-hand choice reaction time is tested as the speed to cancel by tapping a keypad, a 4
inch letter that appears on the screen of a laptop computer. 20 Twenty trials repeated twice
and the median time of last 7 trials in each run is recorded. Simple, same letter, reaction time
takes 1/4 of a second, 250 ms while choice between 2 letters takes twice as long, 500 ms.
Many tests are faster in women, most deteriorate with aging after 25 years and for people
with more years of educational attainment scores are higher. 21
Vision is measured by mapping for color perception which is a central retinal cone
function. This consists of placing 15 pale colors in a spectral array, the Lanthony
desaturated hue test. Retinal rod function which is light perception was mapped for the central
30 o of each visual field at 80 points using an automated perimeter recording to a laptop
computer. 22 This standardized and speeded up the fields that had been done by the tangent
screen and a skilled operator for 100 years.
It was logical to consider the 12 nerves of the head, cranial nerves as the scaffold for
organizing tests and for reviewing brain functions that are adversely affected by chemicals.
Smell (Nerve I, olfactory), is tested by recognition of familiar odors and of threshold concentration
for detecting them. Smell disorders include loss and disturbed perception. Nerve
II, the optic was described above. Nerves III, IV and VI move the eyes and rarely show effects
of chemicals. An exception is the optokinetic effects of styrene. In contrast the faces
sensory nerve, the trigeminal, number V and motor nerve, the facial, number VII are
needed to blink and are tested by blink reflex latency which is measured
electromyographically in milliseconds (10 to 15 ms) after stimulation by a tap, that is mechanical
or an electrical impulse. Blink is slowed by exposures to chlorinated solvents like
trichloroethylene (TCE), by chlorine and by arsenic. Nerve VIII has hearing and vestibular
(balance) divisions which are tested by audiometry and by sway speed for balance. Nerve
IX, the glossopharyngeal innervates the throat and is needed for the gag reflex and
baroreceptor. Nerve X, the vagus X is evaluated by recording variations of heart rate with
breathing. Nerves XI, spinal accessory is tested as strength of neck muscles and XII
tongue’s hypoglossal nerve by speech.
Using these tests implies comparing scores observed to a standard, an expected value.
Ideally that would be to the same subject which is rarely possible, although it works for before
and after exposures of workers. The next best comparisons are to suitable unexposed
normal subjects who can be called controls. 21 We developed over several years a national
sample of unexposed people, tested their performance and calculated expected values using
prediction equations with coefficients for age, sex, education and other factors such as
height and weight that affected some tests. Thus individual observed values for each subject
are compared to predicted values (observed/predicted x100) equal percent predicted. Frequently,
we needed to be sure that comparison groups of apparently unexposed control people
were normal because adverse effects are widespread. Next from the standard deviations