Hazard Assessment and Contaminated Sites - Dealing with Contaminated Sites: From Theory Towards Practical Application - page 520

human and mechanistic studies. Not only may the contaminant need to be assessed
but, in the case of contaminants, the breakdown products such as the four metabo-
lites of atrazine (desethylatrazine, desisopropylatrazine, diamonochlorotriazine and
hydroxyatrazine) when monitoring atrazine contamination of water.
Dose-response Assessment is the second component of Hazard Assessment
and considers both qualitative and quantitative toxicity information to determine
“the incidence of adverse effects occurring in humans at different exposure lev-
els” (US EPA 1989 , p. 1.6). Where available, human and animal evidence will be
assessed as part of this process. Risk Assessment cannot be done without good dose-
response information. Whereas constant doses can be used in animal studies, human
exposures may be variable over time. This may be a significant source of uncertainty.
Although directed at ambient air standards setting, the Australian Ambient
Air Quality Standards Setting: An Approach to Health-Based Hazard Assessment
(NHMRC 2006 ) provides much useful information on Hazard Identification, assess-
ing potential carcinogens and integrating animal and human data and the assessment
of association and causation and complements the Australian Environmental Health
Risk Assessment Guidelines.
For application of Toxicological reference values with regard to contaminated
site management ,see Chapter 5 by Swartjes and Cornelis, this topic.

12.2 Hazard Identification

Hazard Identification examines the capacity of a contaminant to cause adverse
health effects in humans and other animals (US EPA 1995 ). It is a qualitative
description based on the type and quality of the data, complementary information
(e.g., structure-activity analysis, genetic toxicity, pharmacokinetic), and the weight
of evidence from these various sources (ibid). Key issues include (ibid):

•

nature, reliability and consistency of human and animal studies;

•

the availability of information about the mechanistic basis for activity; and

• the relevance of the animal studies to humans.

The Dose-response Assessment examines the quantitative relationships between
exposure and the effects of concern. “The determination of whether there is a hazard
is often dependent on whether a dose-response relationship is present” (ibid , p. 7).
Important issues include:

• the relationship between the extrapolation models selected and available infor-

mation on biological mechanisms;

• how appropriate data sets were selected from those that show the range of

possible potencies both in laboratory animals and humans;

• the basis for selecting interspecies scaling factors to account for scaling doses

from experimental animals to humans;