Handbook of Solvents - George Wypych - ChemTech - Ventech!

1406 Kaye H. Kilburn
Differences between exposure at work and in the community are important, Table
20.9.2. Most worker groups were younger and healthier, met job-entry criteria, have more
reserve function so are less likely to manifest damage. Workers have had selective attrition
of affected or less fit people to accentuate the difference. 3 In contrast community people are
unselected and include more susceptible groups: infants, children, the aged and the unwell. 1
Some differences in exposure are obvious, work exposure is rarely longer than 40 of the
weeks 168 hours. This time away allows work acquired body burdens of chemicals (and
their effects) to diminish or disappear while workers are at home. In contrast, home exposures
may be continuous or nearly so. 4 At work the time that elapsed between exposure and
effect is short, making measurement of the dose of a toxic agent easy. It is less obvious what
should be measured in community exposures.
Good detective work is needed to specify the chemicals to search for and measure in
air, water or soil. Community effects may take years to be recognized as a problem. Opportunities
for pertinent environmental measurements were overlooked and have disappeared
with time, often simply evaporated. Thus measurement of relevant doses are seldom possible
and dose-response curves can rarely be constructed. The logical surrogates for dose such
as distance and direction from a chemical source and duration are rarely satisfactory. 1 Thus
plausible estimates of dose are needed to focus the association of measured effects and the
chemicals that are probably responsible.
The realistic starting place is people’s symptoms-complaints that indicate perception
of irritation from chemicals. 3 These serve as sentinels to alert one to a problem but cannot be
interpreted as impairment or damage without measurements of brain functions. The inability
to characterize exposure should not postpone or prevent adequate investigation for adverse
human health effects. It is intuitive and ethical to suggest that absent of adverse human
effects should be the only reason for stopping inquiry. People’s complaints and upset moods
(anxiety, depression, anger, confusion and fatigue) frequently reflect or parallel impairment.
The question then becomes how to measure effects on the brain to decide whether it is
damaged and if so how much, Table 20.9.3.
Table 20.9.3. Useful tests of evaluation of brain damage from solvents
Tests Part of brain measured
Simple reaction time & visual two choice reaction time
Sway-balance
Blink reflex latency
Color confusion index
retina, optic nerve and cortex integrative radiation to
motor cortex
inputs: ascending proprioceptive tracts, vestibular division
8th cranial nerve, cerebellum, vision, visual integrative
and motor tracts
sensory upper division trigeminal nerves (V), pons, facial
nerves (VII)
center macular area of retina, with optic cones, optic
nerve, optic occipital cortex
Visual fields retina-optic nerve-optic cortex occipital lobe
Hearing auditory division of 8th cranial nerve
Verbal recall memory limbic system of temporal lobe, smell brain
Problem solving culture fair & digit symbol cerebral cortex: optic-occipital and parietal lobe cortex