Drift
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pyraclostrobin and tebuconazole, and the herbicide, simazine. The data indicated that amphibian populations in remote counties are accumulating pesticides, and tissue concentrations correlated with pesticides used upwind. The
evidence shows that the frogs may be more reliable indicators of exposure
that water or sediment.
The mountain ranges in the western United States are ideal for study given
they are located near both agricultural and urban sources of toxics and have
fragile ecosystems with sensitive wildlife. Our work and that of others have
clearly shown that pesticides are transported through air to remote locations, and these residues are accumulated by sensitive biota such as frogs.
The urgency of current and future work is to connect these residues with
health. Studies need to focus on the current use and persistent pesticides
to assess biological impact. Bioassays, including cholinesterase inhibition
(e.g., related to chlorpyrifos and parathion exposures), and endocrine disruption (e.g., related to chlordane and other chlorinated residues, possibly
trifuralin exposures), should be routinely analyzed. Coupling transect studies to mesocosms and in vitro testing that measures tissue levels of pesticides
under different waterborne exposures would enable correlation with what is
measured in transect studies, particularly in areas where wildlife are experiencing adverse effects. Additional targets may be found in fragile ecosystem
for birds, fsh, bees, and other wildlife.
Chlorpyrifos is more toxic to aquatic organisms than diazinon (amphipods
LC 50 : 110 vs 200 ng/mL), and moving up the food chain, organisms are more
tolerant (LC 50 for chlorpyrifos in fathead minnow: 0.1 vs in lake trout 98 ng/
mL), however, chlorpyrifos bioaccumulates (Eisler, 1986; Odenkirchen and
Eisler, 1988). If measured residues in water and sediment are too low to cause
toxicity, we need to look higher in the food chain such as lake trout. Such
an undertaking will require the close coordination of public agencies that
study water sources, recreational areas, and wildlife habitat, an example of
such study is the Sierra Nevada–Southern Cascades study that includes air
monitoring and other research projects still in progress. This may address
questions such as those raised in this and other chapters.
10.3 Pesticide Drift to Nontarget Crops
Pesticide drift through air to nearby or downwind areas can cause damage
to nontarget crops sensitive to the chemical. This can include visible damage (scorched, burnt, dead) vegetation, such as occurs in some uses of contact herbicides, for example, herbicides like the phenoxy class (MCPA, 2,4-D)
bipyridyls (paraquat), glyphosate, dicamba, and others.
In the case of systemic herbicides like glyphosate, drift to nontarget crops
can cause death to the crops (annuals and/or perennials) and thus incur
183
pyraclostrobin and tebuconazole, and the herbicide, simazine. The data indicated that amphibian populations in remote counties are accumulating pesticides, and tissue concentrations correlated with pesticides used upwind. The
evidence shows that the frogs may be more reliable indicators of exposure
that water or sediment.
The mountain ranges in the western United States are ideal for study given
they are located near both agricultural and urban sources of toxics and have
fragile ecosystems with sensitive wildlife. Our work and that of others have
clearly shown that pesticides are transported through air to remote locations, and these residues are accumulated by sensitive biota such as frogs.
The urgency of current and future work is to connect these residues with
health. Studies need to focus on the current use and persistent pesticides
to assess biological impact. Bioassays, including cholinesterase inhibition
(e.g., related to chlorpyrifos and parathion exposures), and endocrine disruption (e.g., related to chlordane and other chlorinated residues, possibly
trifuralin exposures), should be routinely analyzed. Coupling transect studies to mesocosms and in vitro testing that measures tissue levels of pesticides
under different waterborne exposures would enable correlation with what is
measured in transect studies, particularly in areas where wildlife are experiencing adverse effects. Additional targets may be found in fragile ecosystem
for birds, fsh, bees, and other wildlife.
Chlorpyrifos is more toxic to aquatic organisms than diazinon (amphipods
LC 50 : 110 vs 200 ng/mL), and moving up the food chain, organisms are more
tolerant (LC 50 for chlorpyrifos in fathead minnow: 0.1 vs in lake trout 98 ng/
mL), however, chlorpyrifos bioaccumulates (Eisler, 1986; Odenkirchen and
Eisler, 1988). If measured residues in water and sediment are too low to cause
toxicity, we need to look higher in the food chain such as lake trout. Such
an undertaking will require the close coordination of public agencies that
study water sources, recreational areas, and wildlife habitat, an example of
such study is the Sierra Nevada–Southern Cascades study that includes air
monitoring and other research projects still in progress. This may address
questions such as those raised in this and other chapters.
10.3 Pesticide Drift to Nontarget Crops
Pesticide drift through air to nearby or downwind areas can cause damage
to nontarget crops sensitive to the chemical. This can include visible damage (scorched, burnt, dead) vegetation, such as occurs in some uses of contact herbicides, for example, herbicides like the phenoxy class (MCPA, 2,4-D)
bipyridyls (paraquat), glyphosate, dicamba, and others.
In the case of systemic herbicides like glyphosate, drift to nontarget crops
can cause death to the crops (annuals and/or perennials) and thus incur