PRINCIPLES OF TOXICOLOGY

• Hazard-specific training to ensure they know how to work with the chemicals in ways which
will minimize their exposures
• Proper labeling of chemical containers, including the contents and the potential health
hazards, which enables workers to make the appropriate decisions
• Effective engineering controls and proper personal protective equipment
Hazard communication, or “right to know,” is considered the most far-reaching standard OSHA has
enacted, and, if fully implemented, will substantially increase the knowledge of toxic substances and
working conditions. Already, the right-to-know concept has been extended into the community setting,
and also, to some extent, into the public sector. However, although this standard has been in effect for
over 15 years, failure to comply with this rule is one of the most commonly cited OSHA violations.
Before the rule was in place, labels and MSDSs (Material Safety Data Sheets) were notoriously
incomplete, and substantial deficiencies remain today. For example, one recent MSDS limited the toxic
effects of a lead compound to “eye and skin irritation.” Indeed, since the labels and MSDSs are often
prepared by those marketing the toxic substance, there may be a short-term incentive to minimize the
degree of hazard as advertised on the MSDS. The opposite also occurs. The preparer includes so much
information and always specifies the protective measures for worst-case situations in which the readers
have difficulty determining the real hazards and appropriate levels of protection. In spite of these
problems, many labels and MSDSs have gradually improved to the point where they are excellent
quick reference guides to the current state of knowledge on a particular substance, including the latest
animal testing and epidemiological work. Ideally, the labels should be an abstract of what appears on
the MSDS, listing the important acute and chronic toxicity information (including target organs),
exposure routes, necessary personal protective equipment, and the manufacturer.
The right-to-know concept has been extended to include the more fundamental, and controversial,
concept of allowing employees to change the way they do their jobs to reduce a hazard. A Canadian
regulation, dubbed the “right to act,” extends the right-to-know concept accordingly.
Hazard Assessment
22.3 PROGRAM MANAGEMENT 531
Thus far in this chapter industrial hygiene has been described broadly as the applied science devoted
to understanding the interaction between exposure to chemicals and the potential hazardous effects.
In the environment the manifestation of adverse health effects is minimized by eliminating or reducing
exposure as much as possible. The multistep process of reducing exposures involves several distinct
phases, including anticipation, recognition, evaluation, and control of exposures.
Anticipation Anticipation of adverse health effects can be difficult. Successful anticipation usually
involves an examination of the production process while it remains in the design phase. However, it
can also be applied to modifications of existing process, changes in ventilation characteristics, or
increases in production levels. Control measures are often most cost-effective at the stage of new
process design, since disruptive retrofitting measures are avoided. Downtime is eliminated, and
machinery modifications can be included in space and other resource allocations. Opportunities for
substituting a less toxic substance for a more toxic one are also usually more realistic at this stage,
because changes in established, successful processes are resisted and capital costs may be high. In fact,
substitution of less toxic compounds for more toxic substances is likely an important means for future
improvements in both public health and environmental quality.
But how does one anticipate a potential overexposure? The answer is to ask questions of the other
disciplines involved in the design work. Engineers, architects, economists, and other planners are
typically focused on designing the most cost-effective means of production possible. Since the adverse
effects of chemical exposures are often not immediately obvious and stretch out over a number of
years, they are usually overlooked in preliminary designs. Changes in process are usually dictated by