PRINCIPLES OF TOXICOLOGY

532 CONTROLLING OCCUPATIONAL AND ENVIRONMENTAL HEALTH HAZARDS
needed changes in the end product, and the industrial hygienist is called upon only after problems and
complaints become apparent.
For example, an electronics component manufacturing company, which was in the midst of building
a new plant, intended to use a chlorinated solvent to clean circuit boards as the final step in the
production process. An industrial hygienist successfully anticipated the problems in the use of the
particular solvent and asked the design engineers to investigate other cleaning options. Another
chlorinated solvent of lower toxicity could be used, but the designers concluded that this would not
clean the circuit boards effectively. The use of a water-based detergent was an alternative, but was also
considered ineffective. Finally, the use of ultrasonic agitation in distilled water was chosen. This
involved fitting a rather large piece of equipment into the production line, which would have been
difficult had the process been built as originally conceived. In addition, costs were dramatically
reduced, since water was much cheaper than the chlorinated solvent. Although the initial capital
expenditure for the ultrasonic agitator was large, the cost was recovered in a short time by the reduced
cleaner cost. Since no exhaust ventilation was required, heating and cooling costs for the plant were
also reduced. In this instance, the industrial hygienist simply asked questions. The industrial hygienist
had no knowledge of ultrasonic water cleaning for this particular production process. However, by
explaining the need to examine other possibilities, the potential health hazard was successfully
prevented.
By asking questions of those with more specialized knowledge, a potential health hazard can be
completely eliminated before it appears. All designs and design changes should be reviewed by an
industrial hygienist before implementation to avoid having to redress a problem later after exposures
and possible injuries have occurred.
Recognition Unfortunately, the opportunity to participate in design formulation remains the exception
rather than the rule for health professionals. In practice, health hazards are often recognized in
established work settings.
In 1984, the National Research Council (NRC) examined testing needs for toxic substances and
estimated that out of 5 million identified chemicals there were
• 48,523 chemicals in commerce
• 3350 pesticides
• 1815 drugs
• 8627 food additives
• 3410 cosmetics
Eliminating duplicates, the total was 53,500. By taking a randomized subset, the NRC stated that in
order to form a complete health hazard assessment, further toxicological testing was needed for
• 82 percent of all drugs
• 90 percent of all pesticides
• 95 percent of all food additives
• 98 percent of all cosmetics
• Nearly 100 percent of all commercial chemicals not included above
The prospect of recognizing the hazardous effects of all chemicals appears daunting as the number of
identified chemicals continues to grow. The American Chemical Society announced the identification
of the ten millionth chemical in 1990. OSHA has set PELs for only about 400 of these chemicals;
health standards for specific substances often take 10 years to promulgate, and the agency has been
able to promulgate only 13 in its first 25 year history. Thus, neither legal limits nor existing knowledge
can always be relied on to protect health. That is not to say existing knowledge should be ignored.