Environmental Engineering Reference
In-Depth Information
water. These can be either observational epidemiological studies, or what Lilienfield
and Lilienfield ( 1980 ) called “natural experiments”.
12.4.5.1 Hazard Identification
Epidemiology has a number of potential advantages over animal toxicology in the
area of Hazard Identification:
it directly assesses human health risk;
absorption, metabolism, detoxification and excretion may vary between the
human species and the animal species studied and does not need to be taken
into account in epidemiological studies;
sample sizes for human studies may be much larger than those feasible for animal
studies;
genetic diversity may be greater in humans compared to the selected animal
strains used in toxicological studies;
epidemiological studies may include different groups (e.g., the young, old and
susceptible) that may not be included in the usually relatively homogeneous
groups used in toxicological studies;
effects on some aspects of mental function or behaviour, and more subjective
effects such as nausea or headache, can be better assessed in human studies.
Roseman ( 1998 ) and Samet et al. ( 1998 ) provide further advantages:
reduced uncertainty about interspecies variability in metabolism, lifespan, and
genetic diversity;
complex temporal patterns of exposure and doses in situations requiring Risk
Assessment may be impossible to replicate in animal studies; whereas some
epidemiological studies may be more useful for understanding these complex
dose-response relationships;
the ability to assess large numbers of people exposed to low levels of a contam-
inant. The doses from exposure to a hazardous contaminant in epidemiological
studies are often considerably less than in toxicological studies. This may have
the advantage of providing information about the exposure range of interest
although, if they are the result of (prolonged) adult occupational exposures, the
exposures are likely to be considerably more than those experienced by people in
the general population. With appropriate tools small differences in relative risk in
large populations may be able to be assessed.
However, epidemiological studies are often limited by the amount and quality of
data available on dose and tend to address exposure-response relationships (i.e., they
are based on whether or not exposure occurred) rather than dose-response relation-
ships. Saunders et al. ( 1997 ) reviewed 14 key relevant studies selected from a short
list of 43 analytical studies assessing human health effects in relation to hazardous
waste sites, and found that poor exposure measurement was a major factor in the
overall lack of convincing evidence of causation from these studies. It is often the
Search WWH ::




Custom Search