Environmental Engineering Reference
In-Depth Information
In cases where bioavailability data are not available, important clues may
be gained from the physical and chemical properties and physical state of the
contaminant (e.g., liquid, solid or gas) (NHMRC
1999
, p. 65).
12.3.5.10 Other Factors in Scaling of Doses
For inhalational exposure, doses expressed as mg/m
3
or ppm must be converted to mg/kg
bw
in the test species by calculations based on the physical properties of the contaminant and
minute volumes and respiration rates of the animal (NHMRC
1999
, p. 66).
12.3.5.11 Extrapolating Occupational Data to the General Public
Occupational data is often derived from a relatively homogeneous group: usually
male, aged between 20 and 65 years and relatively healthy. When applying this data
to the general population the differences between the exposed populations should be
taken into account as the general population will contain females, and people who
are not in the workforce because of their age (young or old) or poor health.
12.3.5.12 Statistical Tests
The objective of a toxicology study is to demonstrate responses of biological impor-
tance. Where statistical analyses are used in the assessment process, an awareness
of the validity of the test and the degree of certainty (confidence) within the context
of the study should be demonstrated.
There are limitations associated with the use of statistics in toxicology (Gad and
We i l
1986
):
•
statistics cannot make poor data better;
•
statistical significance may not imply biological significance;
•
an effect that may have biological significance may not be statistically significant;
•
the lack of statistical significance does not prove safety.
The importance and relevance of any effect observed in a study must be assessed
within the limitations imposed by the study design and the species being stud-
ied (see also Section
12.2
; “Hazard Assessment Part 2: Hazard Identification -
Epidemiology”).
If statistical tests have not been used, if inappropriate tests appear to have been
used, or if tests not commonly employed have been used, then this should be noted
and action taken, e.g., data re-analysis.
A number of textbooks and papers on the application of statistics in experi-
mental toxicology and the life sciences are available; these include Dickens and
Robinson (
1996
), Gad and Weil (
1986
), Gad and Weil (
1989
), Lee (
1993
), Tallarida
and Murray (
1987
) and Waner (
1992
).
Findings should be considered on the basis of both statistical significance
and likely biological significance. The variability of biological data must be
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