65
Pesticide Exposure and Impact
to advise regulatory agencies in places where agricultural burning is
a common practice. The inhalation of aerosols bearing toxins, viruses,
and pathogens follows the same principles. COVID-19 has triggered a
new level of research into exposures to pathogenic microorganisms via
aerosols.
4.6 Exposures to Ecosystems
Once contaminants enter the air, they are out of our control (Woodrow et al.,
2018). They can travel in the wind and be dispersed to other places that may be
great distances from the source, often in fragile ecosystems (see Chapter 10).
Even when detected at trace levels, deposited chemicals impact the quality of
waters, in water bodies such as lakes, rivers, oceans including snow and ice
and water sheds. Oceanic residues of organochlorine pesticides that undergo
bioaccumulation affect top predators, for example, DDT at a concentration
below one part per billion in water can result in higher contamination in
fsh (2 ppm) and fsh-eating birds (25 ppm) (Woodrow et al., 2018). The same
goes for other nonpolar contaminants such as PCBs and some mercury- and
selenium-containing contaminants.
In the 1970s, there were frequent reports of sick or dying red-tailed hawks
largely in the orchards in the central and southern San Joaquin Valley of
California. A collaborative study was undertaken involving the research team
of Professor Barry Wilson of the University of California, Davis, Department
of Avian Science, Jim Seiber’s team in the Department of Environmental
Toxicology, and others. Wilson approached Seiber with a proposition: Can we
do analysis of hawks to see if they are being exposed to toxic levels of organophosphate (OP) pesticide? These teams analyzed hawk feathers, talons, and
excreta for OPs. They found residues of the OPs parathion and a few others.
But surprisingly high (“off the chart”) levels of paraoxon, a highly toxic environmental conversion product of parathion, were found in hawk feathers and
in orchard air. Was paraoxon the possible culprit? Wilson thought so, but
it was not until his group “connected the dots” and calculated exposure to
paraoxon the hawks would experience from feather preening. Samples from
feathers were markedly higher in oxon than other samples. Thus, the toxic
effects of oxons seen in orchards could be explained by hawk ingestion of
oxons during preening. Carol Weiskopf, a grad student in Seiber’s lab, used
forensic techniques to fnd the diagnostic metabolites of paraoxon in stomachs and excreta of red-tail hawks (Wilson et al., 1991).
Colony collapse disorder among honeybees is of current concern. It results
when adult worker bees die in and around the hive (Oldroyd, 2007; vanEngelsdorp et al., 2009). Some suspect pesticides, especially neonicotinoids (see
Chapter 2) (Gill et al., 2012; Kiljanek et al., 2016).
Pesticide Exposure and Impact
to advise regulatory agencies in places where agricultural burning is
a common practice. The inhalation of aerosols bearing toxins, viruses,
and pathogens follows the same principles. COVID-19 has triggered a
new level of research into exposures to pathogenic microorganisms via
aerosols.
4.6 Exposures to Ecosystems
Once contaminants enter the air, they are out of our control (Woodrow et al.,
2018). They can travel in the wind and be dispersed to other places that may be
great distances from the source, often in fragile ecosystems (see Chapter 10).
Even when detected at trace levels, deposited chemicals impact the quality of
waters, in water bodies such as lakes, rivers, oceans including snow and ice
and water sheds. Oceanic residues of organochlorine pesticides that undergo
bioaccumulation affect top predators, for example, DDT at a concentration
below one part per billion in water can result in higher contamination in
fsh (2 ppm) and fsh-eating birds (25 ppm) (Woodrow et al., 2018). The same
goes for other nonpolar contaminants such as PCBs and some mercury- and
selenium-containing contaminants.
In the 1970s, there were frequent reports of sick or dying red-tailed hawks
largely in the orchards in the central and southern San Joaquin Valley of
California. A collaborative study was undertaken involving the research team
of Professor Barry Wilson of the University of California, Davis, Department
of Avian Science, Jim Seiber’s team in the Department of Environmental
Toxicology, and others. Wilson approached Seiber with a proposition: Can we
do analysis of hawks to see if they are being exposed to toxic levels of organophosphate (OP) pesticide? These teams analyzed hawk feathers, talons, and
excreta for OPs. They found residues of the OPs parathion and a few others.
But surprisingly high (“off the chart”) levels of paraoxon, a highly toxic environmental conversion product of parathion, were found in hawk feathers and
in orchard air. Was paraoxon the possible culprit? Wilson thought so, but
it was not until his group “connected the dots” and calculated exposure to
paraoxon the hawks would experience from feather preening. Samples from
feathers were markedly higher in oxon than other samples. Thus, the toxic
effects of oxons seen in orchards could be explained by hawk ingestion of
oxons during preening. Carol Weiskopf, a grad student in Seiber’s lab, used
forensic techniques to fnd the diagnostic metabolites of paraoxon in stomachs and excreta of red-tail hawks (Wilson et al., 1991).
Colony collapse disorder among honeybees is of current concern. It results
when adult worker bees die in and around the hive (Oldroyd, 2007; vanEngelsdorp et al., 2009). Some suspect pesticides, especially neonicotinoids (see
Chapter 2) (Gill et al., 2012; Kiljanek et al., 2016).