Occupational epidemiology
The epidemiological literature for assessing risk in many, if not
most, modern
occupations has now become sufficiently obsolete that it can no
longer be depended
upon to guide either prevention or adjudication of compensation.
This obsolescence
must be dealt with by developing new sources of information
pertinent to occupational
hazards and the risks associated with most occupations. Ideally, a
comprehensive
surveillance mechanism that would be automatically updated for
the changing risk in a
changing economy would be ideal and may be attainable with
further developments in
health information technology. The characteristics of such a
system are described.
However, there are many obstacles to such a system which
appear insurmountable in
the short term. A more eclectic plan for cooperation and datasharing would help in the
short term and would establish a pattern of collaboration that could
both place
adjudication on a more solid foundation and avoid allegations of
collusion in business.
The general outline for a practical programmed of collaboration
along these lines is
presented.
Occupational medicine depends on a vast and sophisticated
database of epidemiological information to inform
decisions and conclusions based on causation.1 However,
the epidemiological basis for assessing risk in many,
if not most, modern occupations has now become
sufficiently obsolete that it can no longer be depended
upon to guide either prevention or adjudication of
compensation. This obsolescence must be dealt with by
developing new sources of information pertinent to
occupational hazards and the risks associated with most
occupations.
This problem is more serious that is generally realized.
Occupational epidemiology is critical to the practice of
occupational medicine in many ways:
• evidence-based medical dispute resolution (such as
adjudication in workers' compensation, third-party
litigation and insurance settlements),2
• setting priorities in occupational health and safety
practice,
• designing periodic health surveillance protocols,
• supporting worker education,
• identifying possible aetiological mechanisms,
• supporting prevention-related interventions,
• identifying occupational hazards.
If this vast database is obsolete, the practice of
occupational medicine will eventually be misled. In
particular, the critical functions for the resolution of
evidence-based medical disputes, which now act to
protect the interests of both worker and employer, will
become disconnected from reality. Scheduled diseases
and systems based on presumption may find their
assumptions to be out of date. Claims for disability or
mortality related to previously unrecognized risks may be
unfairly rejected. Decisions on individual cases which are
based on an interpretation of the literature will become
increasingly difficult to defend.
THE OBSOLESCENCE OF THE BODY OF KNOWLEDGE
In the early years of the 20th century, when chronic
disease epidemiology was still evolving and most
occupational health studies were anecdotal reports or
case series, exposure levels were relatively high. The
occupations documented to be at greatest risk tended to
be those that were historically recognized as hazardous,
such as mining or forest harvesting. The introduction of
modern methods of epidemiology allowed the detection
of increasingly subtle risks and their documentation for
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purposes of control and compensation. This led to the
documentation of contemporary hazards, such as asbestos
and vinyl chloride, and permitted a body of literature
to develop which largely reflected the experience of
workers who sustained their exposures in mid-century.
Following the pioneering studies of occupational
mortality and morbidity in the 1960s, the 1970s were a
sort of 'golden age', especially for studies of cancer and
for the application of both cohort and case-referent
study designs. Cross-sectional studies largely passed
from the scene because they cannot infer causation and
are prone to bias. However, cohort studies, especially, are
expensive and the current methods of chronic disease
epidemiology required persona] identifiers, which made
them difficult to reconcile with privacy legislation in
Europe. Funding declined in the 1980s and occupational
epidemiology became targeted more narrowly to answer
specific questions. The era of the large-scale 'fishing
expedition', which generated numerous hypotheses but
was prone to report associations arising by chance alone,
was largely over.
Hypothesis-testing studies, to link exposure with
outcome and to suggest mechanism, have been conducted
on occupations with high visibility or economic
importance, such as firefighters and machinists. However,
these studies have not begun to explore all the
possible associations hinted at in the surveillance
literature. Associations suggested but not proved by the
extant literature mostly have been investigated piecemeal,
not in a systematic fashion with due attention to
changing risk profiles. In addition, they have seldom
examined exposures that may lead to future evaluation of
risks that may be anticipated as a result of changing work
practices.