Environmental Health Criteria 214

HUMAN EXPOSURE ASSESSMENT
equipment, and personnel who are both well educated and trained.
Studies need to be adequately designed and planned. Field and
laboratory procedures need to be well defined, so that they can be
carried out in the most appropriate way and in a consistent and
reproducible manner. Other key elements in performing and reporting
exposure studies include the final report and, lastly, the archiving
and retention of data (IPCS, 1992)
11.2 Quality assurance and quality control
It is important to distinguish between the related concepts of QA
and quality control (QC). QA refers to the overall management and
organizational systems instituted to assess and maintain the integrity
of the study. It includes independent monitoring that assures end
users of the data that facilities, equipment, personnel, methods,
practices, records and controls conform to accepted quality management
principles. An effective QA programme provides confidence that the
overall study meets the pre-established quality standards of accuracy,
precision, completeness and clarity. QA should be integrated within
the entire study so that the results are valid and that the final
report accurately reflects these results (IPCS, 1992). Assessing data
periodically is an essential aspect of QA.
QC is a valuable QA tool that is applied to individual components
of the study. Examples of such components are selection of study
participants, collection of environmental samples, chemical analysis
and analysis of data. The quality of an analytical measurement may be
evaluated, for example, by comparing analytical results against a
known standard, determining the sensitivity, accuracy, and precision
of the analysis and ensuring that the analytical equipment has been
properly maintained. These measurements would be part of a QC system
(IPCS, 1992).
Auditing procedures, on the other hand, are used to assess the
quality of other aspects of a monitoring operation such as sampling
procedure and transport of samples, as well as recording and reporting
data. These procedures, although not necessarily quantitative, will
generally promote vigilance by the operator against possible errors
(WHO, 1986).
11.3 Elements of a quality assurance programme
All exposure studies must have a QA programme with a
corresponding quality assurance plan that describes the implementation
of the programme. The US EPA, for example, requires the development of
detailed QA project plans that contain a complete description of all
elements of the QA programme associated with the collection,
measurement, validation and reporting of data. Common elements in QA
plans are given in Table 36.
Table 36. Common elements in quality assurance plans
Organization and personnel
Record keeping and data report
Standard operating procedures
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