Human Health Risk Assessment - Dealing with Contaminated Sites: From Theory Towards Practical Application - page 251

parameters for which it is generally known that they play a crucial role for the spe-
cific Risk Assessment (e.g., a vegetable-soil BioConcentrationFactor, when the Risk
Assessment focuses on the human health risk related to vegetable consumption from
a contaminated site) or ones that have a large influence on the outcome of the Risk
Assessment (e.g., on a Soil Quality Standard or a Risk Index). The first aspect, that
is, identifying the most crucial parameters for the specific Risk Assessment, mainly
is a matter of experience. An experienced model user knows from the contami-
nant characteristics which exposure pathways and corresponding input parameters
are the most relevant. The second aspect, that is, the assessment of the influence
of input parameters on the outcome of the Risk Assessment, can be investigated
by means of a sensitivity and uncertainty analysis . A sensitivity analysis investi-
gates the impact of a predefined change of an input parameter (e.g., a 10% increase)
on the outcome of the Risk Assessment. An uncertainty analysis investigates the
impact of an input parameter, given its distribution, on the outcome of the Risk
Assessment.
5.6.6 Ethical Issues
5.6.6.1 Human Beings
The most direct way to test the effects of contaminants in regard to human health
effects would be to expose humans to contaminants under controlled conditions.
This kind of experiment, for example, human volunteer studies in which the vol-
unteers are often paid, will also lead to the most accurate Critical Exposure values.
However, testing human beings has been recognised as a critical ethical issue for
centuries. In the last century, several codes of law were released on this topic, start-
ing with the Nuremberg Code, following the Nuremberg Military Tribunals after
World War II. The major question inherent to this debate is: 'under what circum-
stances is it morally and ethically acceptable to intentionally expose humans to
contaminants, for which it is known that they can experience adverse human health
effects?' There is recognition among the general public that human experimentation
is a critical aspect of the development of new drugs and approaches to treat dis-
eases (Roberts 2001 ). However, there is much more debate on human experimenting
in regard to Human Health Risk Assessment related to environmental issues such
as contaminated sites (e.g., McConnell 2001 ). Most certainly, when investigating
an effect dose, the experimental human beings must experience adverse effects by
definition.
Conditional supporters of human experiments refer to the human health effect
balance: by affecting a few, many may benefit. Koren and Seal ( 2001 ) noticed that
many of the public human health decisions, policies and practices in the USA have
benefited from, and have been based on, research wherein human beings are exposed
to some degree of risk. In the USA, a document was published with recommenda-
tions on circumstances when dosing of humans with contaminants would and would
not be acceptable (US Environmental Protection Agency 2000 ).