Agriculture Reference
In-Depth Information
Hazard Identification
PNEC
PEC
Risk characterization
Refined risk
characterization
PEC/PNEC
1?
Current risk minimal
(no further testing)
No
Can ratio PEC/PNEC be lowered by:
1. Refinements of information
2. Further testing?
Risk
reduction
measures
No
Yes
1. Chronic tests / field tests
2. Bioaccumulation tests
3. Extended representation of
trophic levels
and/or
Refined exposure assessment
incorporating biomarkers and
bioavailability levels
and/or
Long-term monitoring (including
use of biomarkers to assess
changing bioavailability)
FIGURE 16.3
A risk assessment scheme indicating how biomarkers may in the future be incorporated in the
assessment process. PEC = predicted environmental concentration; PNEL = predicted no effect concentration.
DECISIONS ON MANAGING ESTIMATED RISK OF
CHEMICALS TO EARTHWORMS
Once a regulatory scheme has been developed and it seems likely that earthworms are adversely
affected by a chemical, the obvious next step is to protect earthworm populations. Most agricultural
pesticides are used in soils in which earthworms may be affected. Because this is unavoidable, the
second-best option would be to decide whether the effects will be Ñacceptably low.Ò Another
possibility is to decide if any effects will be reversible within a reasonably short period of time
and thus not affect the earthworm population too severely in the long term. Knowledge of earthworm
life cycles and reproduction rates becomes relevant if population recovery is to be considered, but
unfortunately knowledge of life cycles is available for relatively few species. Kokta and Rothert
(1992) advocated that at least the pretreatment earthworm population level should be restored before
the next application of the same chemical is undertaken, but this assumes that populations are at
a steady level, which is usually not the case. Whatever the approach may be, making decisions will
remain difficult even when a more scientific basis for decision making on pollutants is provided
