Deliverable 28: Specification of low risk products REBECA ...

The multiplication of non-target risks with persistence and dispersal factors is in our
opinion the only appropriate way to account for the elevated risk resulting from
increased exposure of non-targets.
There are three factors at play which affect environmental pesticide risk: these are
label rates, formulation type, and application method. We consider it necessary to
calculate the risk indicator on an application basis for the end-use product, as label
rates, application method and formulation will strongly affect environmental exposure.
Scoring and rationales
Persistence. Persistence of an active ingredient in the environment is an important
factor in determining its risk because it strongly influences the likelihood for nontarget
organism exposure. However, it is a difficult task to define a scoring system
where conventional chemicals and microbials can be fairly compared. Clearly, living
organisms can have an entirely different behaviour in the environment than
chemicals in that they can proliferate in the environment. On the other hand microorganisms
often have a narrow host range and may, in the absence of a suitable host
for proliferation, degrade in the environment similarly to chemical substances.
Further, it is important to note that, from a risk assessment perspective, an organism
or substance naturally present in the environment must be regarded differently than a
new species or substance introduced into an ecosystem.
We postulate that a naturally occurring substance or organism will pose no additional
risk to the environment if introduced into a comparable system at similar
concentrations. For instance, the concentrations of entomopathogenic fungi often
heavily fluctuate depending on host densities and micro-climatic conditions, and
concentrations found during naturally occurring epizootics are often as high as those
found after artificial inoculations (Kessler, 2004; Laengle, 2005).
Therefore, a relatively high and persistent concentration of an indigenous organism in
the environment, even if a result of artificial inoculation, does not necessarily add an
environmental risk. Contrarily, persistence of non-indigenous micro-organism in the
environment also means prolonged exposure of potential non target organisms that
may never have been previously exposed to the micro-organism. Likewise, persistent
or increasing concentrations of a micro-organism in the absence of its natural host
could be an indicator of vegetative growth or even multiplication in non-target hosts.
To account for these considerations in a systematic manner, we propose to score the
persistence component in our risk indicator as laid out in Table 1. The persistence
score for both chemicals and microbials is dependent on its half-life in the absence of
the target host, where the half-life is the highest value from all environmental
compartments. The reduced risk for indigenous micro-organisms and naturally
occurring substances is taken into account by assigning a low persistence score if
concentrations return to levels comparable to natural concentrations within one or
two years of application.
Table 1 Scores assigned for persistence of the assessed active ingredient. Values
are assigned based on its half-life in the environmental compartment where the agent
is most stable, or based on the percentage of CFUs (colony forming units) of BCA
found one or two years post application (in target absence).
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