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First national-scale reconnaissance of neonicotinoid insecticides in streams across the USA


Abstract and Figures

To better understand the fate and transport of neonicotinoid insecticides, water samples were collected from streams across the United States. In a nationwide study, at least one neonicotinoid was detected in 53% of the samples collected, with imidacloprid detected most frequently (37 %), followed by clothianidin (24 %), thiamethoxam (21 %), dinotefuran (13 %), acetamiprid (3 %) and thiacloprid (0 %). Clothianidin and thiamethoxam concentrations were positively related to the percentage of the land use in cultivated crop production and imidacloprid concentrations were positively related to the percentage of urban area within the basin. Additional sampling was also conducted in targeted research areas to complement these national-scale results, including determining: (1) neonicotinoid concentrations during elevated flow conditions in an intensely agricultural region; (2) temporal patterns of neonicotinoids in heavily urbanised basins; (3) neonicotinoid concentrations in agricultural basins in a nationally important ecosystem; and (4) in-stream transport of neonicotinoids near a wastewater treatment plant. Across all study areas, at least one neonicotinoid was detected in 63% of the 48 streams sampled.
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First national-scale reconnaissance of neonicotinoid
insecticides in streams across the USA
Michelle L. Hladik
and Dana W. Kolpin
US Geological Survey, California Water Science Center, 6000 J Street, Placer Hall, Sacramento,
CA 95819, USA.
US Geological Survey, Iowa Water Science Center, 400 S. Clinton Street, Iowa City, IA 52240,
Corresponding author. Email address:
Environmental context. Neonicotinoids are under increased scrutiny because they have been implicated in
pollinator declines and, more recently, as potential aquatic toxicants. Nevertheless, there is currently little
information on concentrations of multiple neonicotinoids in surface water. This paper presents a summary of
concentrations of six neonicotinoids in streams from across the United States in both urban and agricultural
areas. These environmental data are important in determining the potential risk of neonicotinoids to non-target
aquatic and terrestrial organisms.
Abstract. To better understand the fate and transport of neonicotinoid insecticides, water samples were collected from
streams across the United States. In a nationwide study, at least one neonicotinoid was detected in 53 % of the samples
collected, with imidacloprid detected most frequently (37 %), followed by clothianidin (24 %), thiamethoxam (21 %),
dinotefuran (13 %), acetamiprid (3 %) and thiacloprid (0 %). Clothianidin and thiamethoxam concentrations were
positively related to the percentage of the land use in cultivated crop production and imidacloprid concentrations were
positively related to the percentage of urban area within the basin. Additional sampling was also conducted in targeted
research areas to complement these national-scale results, including determining: (1) neonicotinoid concentrations during
elevated flow conditions in an intensely agricultural region; (2) temporal patterns of neonicotinoids in heavily urbanised
basins; (3) neonicotinoid concentrations in agricultural basins in a nationally important ecosystem; and (4) in-stream
transport of neonicotinoids near a wastewater treatment plant. Across all study areas, at least one neonicotinoid was
detected in 63 % of the 48 streams sampled.
Received 21 March 2015, accepted 15 April 2015, published online 18 August 2015
There is increasing concern about neonicotinoid insecticides
not only to pollinators
but also to other organisms such as
those residing in aquatic environments.
Elevated surface-
water concentrations of imidacloprid have been correlated with
direct effects on invertebrates
and indirect effects on insec-
tivorous birds
and some fish.
Recent research has focussed
on not only acute toxicity of neonicotinoids but also chronic
toxicity, especially to aquatic invertebrates that may be exposed
to neonicotinoids by water.
Neonicotinoid use has continued to increase both in the
United States
and worldwide.
They are applied in
both agricultural (foliar sprays, in-furrow treatments and
seed coatings) and urban (lawn and garden foliar sprays,
granular, tree injections; companion animal flea treatment)
settings. Neonicotinoids are highly water-soluble (octanol–
water partition coefficients, log K
, range from 0.55
to 1.26)
with fairly long soil degradation half-lives
3 to 545 days),
making them both mobile and
persistent with the potential for offsite transport to adjacent
water bodies.
The lack of surface-water data is considered an important
knowledge gap for neonicotinoids.
This information is
needed to accurately assess potential environmental effects from
neonicotinoid exposures from stream concentrations. Current
surface-water data exist primarily for imidacloprid, the mostly
widely use neonicotinoid globally.
More recent studies, how-
ever, have documented mixtures of neonicotinoids in wet-
and surface water.
example of such research documented that neonicotinoid mix-
tures were prevalent in streams in the Midwestern US, even in
the largest systems (i.e. Missouri and Mississippi Rivers), with
substantial temporal pulses of neonicotinoids in streams follow-
ing rainfall events during crop planting likely attributed to seed
treatment applications.
The current study provides the first national-scale assess-
ment of neonicotinoids in USA streams that has been con-
ducted to date. In addition, targeted research studies were
conducted to complement these national-scale results to
enhance our understanding of the contributions of both agri-
cultural and urban neonicotinoid use to stream concentrations.
Such national- and regional-scale data sets provide important
geographic and temporal data that can be used to provide
important baseline concentration information for determining
potential environmental effects from exposure to stream neo-
nicotinoid concentrations.
Environ. Chem.
Journal compilation ÓCSIRO 2015
Research Paper
National study
To obtain the first nationwide data set on neonicotinoids, 38
streams across 24 US states and Puerto Rico were sampled one
time for neonicotinoids between November 2012 and June 2014
(Fig. 1; Table S1). These samples were collected as part of larger
project to assess the human and ecological health risks associated
with exposure to complex chemical mixtures.
Thirty-four of
the streams were specifically selected owing to a wide range of
contaminant sources within their watersheds (e.g. agricultural and
urban sources). In addition, four streams were selected as
biological reference sites because they are considered to have
fish and aquatic macroinvertebrate communities that have been
minimallydisturbed by human development. The sampled water-
sheds range in size from12 to 16 200 km
(median ¼170 km
All water samples were collected from the centroid of flow.
Additional information on the site characteristics can be found
in Table S1.
Streams during elevated hydrologic conditions:
Iowa, 2014
To determine neonicotinoid concentrations in streams during
elevated hydrologic conditions in an intensely agricultural
region, grab samples from six sites in Iowa (Table 1;Fig. 2a)
Nationwide study site
Targeted research site
0 250
Puerto Rico
0 250 500 km
500 miles
Fig. 1. Map showing sample locations for the nationwide study (2012–14) and targeted research studies
Table 1. Site information, neonicotinoid concentrations and instantaneous loads for samples collected from Iowa stream and rivers after heavy rains
and flooding in 2014
Samples collected in 2013 for these sites are also included
site ID
Date Discharge
(ng L
(ng L
(ng L
load (g s
Missouri River at Omaha, NE 06610000 836 000 19-Jun-13 1150 18 4.4 11 0.038
18-Jun-14 2080 25 11 18 0.11
North Fork Maquoketa River
near Fulton, IA
05418400 1310 24-Jun-13 28 74 4.8 40 0.003
19-Jun-14 77 98 11 40 0.011
Old Mans Creek near Iowa City,
05455100 521 26-Jun-13 36 84 23 26 0.005
01-Jul-14 157 68 25 20 0.018
Iowa River at Wapello, IA 05465500 32 400 01-Jul-13 1420 62 15 30 0.15
03-Jul-14 3030 53 19 20 0.28
Big Sioux River at Sioux City, IA 06485950 24 400 20-Jun-14 1821 77 20 38 0.25
Turkey River at Garber, IA 05412500 4000 20-Jun-14 708 132 26 73 0.16
M. L. Hladik and D. W. Kolpin
were collected from the centroid of flow following heavy
rainfall and after most row crops (corn and soybeans) had been
planted in these watersheds. Four out of the six sites were above
flood stage and all samples were collected near the crest of the
hydrograph. The drainage area for the basins sampled ranged
from 521 to 836 000 km
Temporal patterns in urban streams in the Southeast
Two urban-affected streams (Sope Creek, 80 km
urban; Chattahoochee River, 6300 km
, 18 % urban) were
frequently sampled (67 total samples) in Georgia to better
understand temporal variations in stream neonicotinoid con-
centrations derived from urban sources (Fig. 2b). All water
samples from these sites were collected through depth and
width-integrated composites.
Samples were collected
from Sope Creek every 2 weeks on a set schedule for 2 years
starting in October 2011 (48 samples collected). Samples were
collected from the Chattahoochee River on an alternating once
or twice per month set schedule (19 samples collected). No
samples from these two sites were collected in relation to any
specific flow conditions.
Streams in a nationally important ecosystem:
Chesapeake Bay
As part of a larger study to determine if chemical exposure is
contributing to fish health issues being observed in the Chesa-
peake Bay watershed,
water samples were collected from
three sites in this watershed (Fig. 2c): six samples from Antietam
Creek (725 km
, 25 % cultivated crops, 10 % urban); seven
samples from Big Pipe Creek (270 km
, 41 % cultivated crops,
2 % urban); and four samples from Chillisquaque Creek,
(290 km
, 32 % cultivated crops, 2 % urban). Automatic sam-
plers were used to collect water.
In-stream transport: Fourmile Creek, Iowa
To better understand the contributions of neonicotinoids to
streams from wastewater treatment plant (WWTP) discharge
and their in-stream fate, a 4.8-km reach of Fourmile Creek,
located near Ankeny, Iowa, was investigated (Fig. 2a). The
study reach extends from 1.9 km above the WWTP outfall
(46 10
L day
; activated sludge treatment) to 2.9 km down-
stream of the WWTP outfall. In addition to a WWTP effluent
sample, stream samples were collected at 1.9, 1.6, 0.08,
0.05, 0.05, 0.33 and 2.9-km distance in relation to WWTP
outfall. Samples were collected in a Lagrangian approach, in
which the same approximate parcel of water was tracked as it
moved downstream, as was conducted previously in this study
All samples were collected at the centroid of flow.
The proportion of stream flow derived from WWTP effluent
below the outfall varies depending on antecedent moisture
conditions. The first sampling of this study reach occurred from
5 to 6 December 2012 during a time of prolonged drought
conditions. Thus, the stream flow below the outfall was
0.17 m
, with 99 % of this flow derived from effluent. The
second sampling occurred on 20 June 2013 during more normal
early-summer flow conditions, with the stream flow below the
outfall at 1.7 m
, with 11 % of this flow derived from
Analytical method
All samples were placed in 1-L amber glass bottles and chilled at
48C until extraction. The six neonicotinoids (acetamiprid,
clothianidin, dinotefuran, imidacloprid, thiacloprid and thia-
methoxam) were measured in the water samples using a previ-
ously published method.
Samples were filtered with a
0.7-mm glass-fibre filter (Whatman, Piscataway, NJ), spiked
with a surrogate (imidacloprid-d
; Cambridge Isotope,
Andover, MA), and passed through an Oasis HLB solid-phase
Turkey River
Big Sioux River North Fork Maquoketa River
Fourmile Creek
Missouri River
Sope Creek
Chattahoochee River
Chillisquaque Creek
Antietam Creek
Chesapeake Bay
Big Pipe Creek
Iowa River
Old Mans Creek
Targeted research site
Targeted research site
Targeted research site
Fig. 2. Sites sampled as part of targeted research studies: elevated
hydrologic conditions and in-stream transport in an intense agricultural
region in Iowa (a); urban streams in the south-eastern USA (b); and
Chesapeake Bay (c).
Neonicotinoids in US surface water
extraction (SPE) cartridge (6 mL, 500 mg; Waters Corporation,
Milford, MA). The cartridge was eluted with 10 mL of 50 : 50
dichloromethane : acetone, reduced under nitrogen and an
internal standard,
-caffeine, was then added. Extracts were
analysed on an Agilent 1260 bio-inert liquid chromatograph
(LC) coupled to an Agilent 6430 tandem mass spectrometer
(MS-MS) (Santa Clara, CA). The theoretical level of detection
(LOD) was 2 ng L
and the method detection limits (MDL)
ranged from 3.6 to 6.2 ng L
Neonicotinoid concentrations were validated against a set of
quality control parameters including: field blanks (9), replicate
samples (17), matrix spikes (8) and surrogate recovery. No
compounds were detected in any of the blanks, field replicates
had relative percentage differences (RPD) between the regular
and replicate sample of ,25 %. Matrix spike recoveries ranged
from 70 to 102 %. Recovery of the surrogate (imidacloprid-d
ranged from 70 to 120 % for all samples; data presented here
were not recovery-corrected.
Results and discussion
A total of 149 stream samples were collected and analysed for
six neonicotinoids in one national-scale and four complemen-
tary research studies. A summary of the results of these efforts
National study
Five of the six neonicotinoids measured were detected in this
first ever national-scale study (Table S1). Although these sam-
ples represent only a single snapshot in time for the 38 sites
sampled, they do represent spatial variations in stream neoni-
cotinoid concentrations across the USA (Fig. 1). At least one
neonicotinoid was detected in 53 % of the 38 sites sampled.
Imidacloprid was the most frequently detected neonicotinoid
(37 %, maximum concentration 140 ng L
), followed by clo-
thianidin (24 %, 66 ng L
), thiamethoxam (21 %, 190 ng L
dinotefuran (13 %, 130 ng L
) and acetamiprid (3 %, 40 ng L
(Fig. 3, Table S1). Thiacloprid was not detected in any of the
samples collected. Of the 37 detectable concentrations of indi-
vidual neonicotinoids, 92 % were ,100 ng L
with the median
detected concentration of 19 ng L
. When summed, the highest
total neonicotinoid concentration for a given sample was 450 ng
(Fig. 4). Mixtures of multiple neonicotinoids in a single
sample were common; two or more were detected in 26 % of the
samples, three or more were detected in 11 % of the samples, and
one sample (3 %) had five neonicotinoids detected (Table S1).
To provide a better understanding of neonicotinoid sources,
an examination of the relationship between concentration and
land-use (Table S1) was conducted (Table S2). This analysis
determined a significant, positive relation (using Spearman’s
rank correlation) to cultivated crops for clothianidin (r¼0.465,
P¼0.003) and thiamethoxam (r¼0.472, P¼0.003) and a
positive relation to urban land-use for imidacloprid (r¼0.474,
P¼0.003). These were expected relations to land-use based on
the primary use of these neonicotinoids. In addition, a signifi-
cant positive relation was observed between the two principal
agriculturally used neonicotinoids, clothianidin and thia-
methoxam (r¼0.668, P,0.001). Their co-occurrence can at
least partially be explained by the fact that both neonicotinoids
37 %
24 %
21 %
13 %
3 %
Concentration (ng L1)
Sum of
Fig. 3. Box plot of total neonicotinoids detected at 38 sites in a nationwide study from 2012 to 2014. Scatterplots show the
range of individual neonicotinoid concentrations for the five compounds detected (out of six measured); overall detection
frequency is listed underneath the compound names.
Total neonicotinoid concentration (ng L1)
400 Imidacloprid
Fig. 4. Concentrations of neonicotinoid insecticides at 38 individual sites
collected as part nationwide study from 2012 to 2014. The site number
corresponds to the full names given in Table S1.
M. L. Hladik and D. W. Kolpin
are primarily used on cultivated crops and that clothianidin is
also a transformation product of thiamethoxam.
There were
no significant relations among the other neonicotinoids under
investigation (Table S2).
Streams during elevated flow conditions: Iowa, 2014
Because of the generally wet conditions across much of Iowa
during the spring and early summer of 2014, a set of water
samples from six sites were collected (Fig. 2a) to determine the
effect such elevated flow conditions would have on stream
neonicotinoid concentrations in an intensely agricultural region.
Neonicotinoids were present in all six samples collected
(Table 1). These 2014 results were similar to those collected
during this same general time period in 2013
; median indi-
vidual neonicotinoid concentration was 23 ng L
in 2014 and
25 ng L
in 2013 for sites with samples collected during both
years. Although stream concentrations were similar between
2013 and 2014, the wet conditions in 2014 did cause substan-
tially higher stream flows compared with 2013, which translated
to higher instantaneous neonicotinoid loads (Table 1); thus,
neonicotinoid loads were two to four times higher in 2014 than
in 2013. These results confirm that precipitation is an important
driver of neonicotinoid transport to streams following periods of
use; even when such precipitation is heavy enough to cause
substantial stream flooding, the neonicotinoid concentrations
were not reduced.
Temporal patterns in urban streams in the Southeast
For this research component, stream samples were collected
from two urban-affected streams (Fig. 2b): Sope Creek and the
Chattahoochee River on a fixed sampling schedule. Not sur-
prisingly, imidacloprid was the dominant neonicotinoid present
Chattahoochee River near Whitesburg, GA
Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct
Total neonicotinoid concentration (ng L1)
e (m3 s1)
Sope Creek near Marietta, GA
Oct Jan Apr Jul Oct Jan Apr Jul Oct
imidacloprid concentration (ng L1)
2013 2011
Fig. 5. Concentrations of imidacloprid and the corresponding stream discharge from October 2011 to
October 2013 for Sope Creek (a). Concentrations of imidacloprid, dinotefuran and acetamiprid along with
the corresponding stream discharge from September 2011 to September 2012 for Chattahoochee River (b).
Black bars represent samples where no neonicotinoids were detected.
Neonicotinoids in US surface water
in these urban-affected streams, being detected in 87 % of 67
samples collected. Dinotefuran (10 %) and acetamiprid (7 %)
were detected sporadically and were found along with imida-
cloprid (Table S3).
Imidacloprid was present in almost every sample (90 %)
collected from the heavily urbanised Sope Creek (39 % urban)
(Fig. 5a). Unlike what has been observed in agricultural streams
in the Midwest,
there was no significant relation between
imidacloprid concentrations and stream flow (r¼0.21,
P¼0.17). This may have been at least partially due to the lack
of a distinct use period for imidacloprid in such an urban-
affected basin and the lack of a distinct growing season in the
warmer climate of the south-eastern United States. In addition,
the frequent events (e.g. frequent flushing of the system)
observed in Sope Creek (Fig. 5a) and the warmer climate
(possibly leading to increased degradation rates) may also have
contributed to differences when comparing these urban-affected
results with agricultural areas of the Midwest.
For the Chattahoochee River, which includes the Sope Creek
drainage, one or more neonicotinoids were detected in 79 % of
samples, two or more in 37 %, and three or more in 16 % of the
samples collected. Imidacloprid was the most frequently
detected neonicotinoid (79 %), followed by dinotefuran (32 %)
and acetamiprid (5 %; Table S3). The more varied neonicotinoid
detections in the Chattahoochee River compared with Sope
Creek were likely a reflection of the more diverse land-use
because the larger Chattahoochee watershed is 18 % urban and
includes 9 % pasture (no cultivated crops, however). As with
Sope Creek, there were frequent runoff events (Fig. 5b), with no
significant relation between imidacloprid concentrations and
stream flow (r¼0.05, P,0.87).
Streams in a nationally important ecosystem:
Chesapeake Bay
For this research component, stream samples were collected
from three agriculturally affected streams (Fig. 2c): Antietam
Creek, Big Pipe Creek and Chillisquaque Creek, with a specific
emphasis on collection of runoff samples during the planting
season of cultivated crops. Overall, neonicotinoids were
detected in 59 % of the stream samples. Clothianidin was the
most frequently detected neonicotinoid (59 %), followed by
thiamethoxam (29 %), and imidacloprid (6 %) (Table S4,
Fig. 6). The thiamethoxam and imidacloprid detections were all
found in the presence of clothianidin.
Similar to previous research on agricultural streams in the
Midwestern USA,
an increase in neonicotinoid concentra-
tions was observed in these streams during runoff conditions
associated with the planting season of cultivated crops (Fig. 6).
Although there were not enough samples to test statistically, the
concentrations of clothianidin and thiamethoxam (the two
neonicotinoids primarily used for agricultural purposes) gener-
ally increased as the amount of land used in cultivated crops
increased. The highest concentrations for each site occurred on
16 May 2014 and sites ranked the same with respect to percent-
age cultivated crops and clothianidin plus thiamethoxam con-
centration: Big Pipe Creek (41 %; 93 ng L
Creek (32 %; 64 ng L
).Antietam Creek (21 %; 11 ng L
The measurement of neonicotinoids is one component in deter-
mining if chemical exposures are contributing to fish health
issues being observed in the Chesapeake Bay watershed. Future
work will seek to determine the relative effects from various
chemicals (e.g. neonicotinoids) and additive or synergistic
effects from chemical mixtures (e.g. pesticides, hormones,
pharmaceuticals) on fish health.
In-stream transport: Fourmile Creek, Iowa
The two different sampling events of the 4.8-km study reach for
this research component captured two vastly different WWTP-
derived flow scenarios (99.5 and 11.0 % flow-derived effluent
below the WWTP). The December 2012 sampling occurred
during a time of prolonged drought conditions and months after
any agricultural use of neonicotinoids had taken place. Thus, the
flow of Fourmile Creek below the WWTP outfall was 99 %
effluent at this time. Only imidacloprid and clothianidin were
detected during this December sampling (Table S5). During this
time, the input of WWTP effluent into Fourmile Creek caused an
increase in stream concentration for imidacloprid and a decrease
Antietam Creek near Sharpsburg, MD
Apr May Jun
Big Pipe Creek at Bruceville, MD
Apr May Jun
Total neonicotinoid concentration (ng L1)
e (m3 s1)
Chillisquaque Creek at Chillisquaque, PA
Apr May Jun
Fig. 6. Concentrations of clothianidin, imidacloprid and thiamethoxam
and the corresponding stream discharge at three sites in the Chesapeake Bay
area sampled in 2014. Black bars represent samples where no neonicotinoids
were detected.
M. L. Hladik and D. W. Kolpin
in stream concentration for clothianidin (Fig. 7). This trend was
not unexpected owing to the primary uses for these neonicoti-
noids (i.e. agricultural use for clothianidin and urban use for
imidacloprid). These neonicotinoids appear to be transported
conservatively through this study reach because similar con-
centrations were found from the uppermost sampling point to
just above the WWTP outfall and from just below the WWTP
outfall to the lowermost sampling point (Fig. 7).
The June 2013 sampling occurred during a time of normal,
early-summer flow conditions (i.e. median flow) and soon after
the primary period of the agricultural use of neonicotinoids had
taken place in the headwaters. Correspondingly, the flow of
Fourmile Creek below the WWTP outfall was 11 % effluent at
this time. During this sampling, clothianidin, imidacloprid and
thiamethoxam were detected (Table S5). Given the strong
agricultural use for clothianidin and thiamethoxam, the higher
stream concentrations in the upper portion of the reach, derived
from row-crop production in the headwaters, compared with that
observed during the December 2012 sampling were expected.
As was observed previously, only clothianidin and imidacloprid
were detected in the WWTP effluent, with clothianidin being
present at lower concentrations than imidacloprid. In addition,
the input of WWTP effluent into Fourmile Creek again caused
an increase in stream concentrations for imidacloprid and a
slight decrease in stream concentrations for clothianidin (Fig. 7).
This trend, however, was dampened by the much lower influ-
ence of the WWTP on stream flow below the outfall (11 %
effluent-derived stream flow) compared with the December
December 2012 June 2013
Fig. 7. Concentrations (ng L
) of clothianidin and imidacloprid collected along Fourmile Creek near
Ankeny, Iowa, at two sampling times, December 2012 and June 2013. The concentrations in red are those
found at the outfall of the wastewater treatment plant (WWTP).
Neonicotinoids in US surface water
2012 sampling (99 % effluent-derived stream flow). As with the
December sampling, conservative transport of neonicotinoids
was observed, with similar concentrations from the uppermost
sampling point to just above the WWTP outfall and from just
below the WWTP outfall to the lowermost sampling point
(Fig. 7).
In this first wide-scale investigation of neonicotinoids, they were
frequently detected in streams across the USA, with 63 % of the
48 streams samples having a detection of at least one neonicoti-
noid. Both urban and agricultural uses contributed to stream
neonicotinoid concentrations, with imidacloprid occurrence
significantly related to the amount of urban land-use and clo-
thianidin and thiamethoxam significantly related to the amount of
cultivated crops. Similarly to previous research, transport to
streams in agriculturally affected basins is driven by use and
precipitation. The present study,however, has documented this to
be true even when precipitation is heavy enough to cause sub-
stantial flooding. Research within a 4.8-km study reach of
Fourmile Creek found that the input of WWTP effluent into the
system caused stream concentrations of imidacloprid to increase
and clothianidin to decrease. Both neonicotinoids, however,
were found to be transported conservatively throughout the
study reach. Although the present research provides important
baseline data on neonicotinoid concentrations in streams and
helps expand our understanding of their sources and environ-
mental fate, more research is needed to understand the potential
direct effects to aquatic organisms and indirect effects to both
aquatic and terrestrial organisms from these stream neonicoti-
noid concentrations.
We thank Dan Calhoun and Pat Phillips for providing samples and site
information for Georgia and Chesapeake Bay respectively; Jim Orlando for
generating maps and the land-use data; Megan McWayne and Corey Sanders
for sample processing; and all of the field crews from across the United
States who collected the various stream samples. Funding or support was
provided by the US Geological Survey (USGS) Toxic Substances Hydrology
Program, USGS Priority Ecosystems Science, USGS National Water
Quality Assessment Program and the Georgia Department of Agriculture.
Any use of trade, firm or product names is for descriptive purposes only and
does not imply endorsement by the US Government.
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Neonicotinoids in US surface water
... Concerns are particularly growing due to the presence of the widely used insecticide, imidacloprid, and neonicotinoids in general, in unintentionally treated areas in the form of dust generated by the operation of seed sowing machines, thereby affecting non-target beneficial insects [1,2]. Also, as it is soluble in water, imidacloprid has been observed in lakes and streams which presents a danger for various types of aquatic organisms [2][3][4][5]. Numerous studies have been conducted with the aim of studying the consequences of the use of imidacloprid on various species of bees and ladybugs. The studies showed an increase in mortality, damage to nervous system tissues, vision, and smell, as well as slowed growth and development of these insects. ...
Full-text available
The aim of this work was to develop hybrid TiO2/ZIF-8 photocatalysts and test their activity for the removal of agricultural pollutants in water. The hybrid photocatalysts were prepared by an innovative method involving hydrothermal synthesis at 150 °C using a mechanochemically synthesized zeolitic imidazolate framework (ZIF-8) and titanium tetraisopropoxide as a titanium dioxide (TiO2) precursor. Three composite photocatalysts with different mass fractions of titanium dioxide (5, 50, and 95 wt%) were synthesized and characterized, and their adsorption and photocatalytic properties investigated for the removal of imidacloprid. The equilibrium adsorption test showed that ZIF-8 is a good adsorbent and can adsorb 65% of the model component under the working conditions used in this work, while the hybrid photocatalysts can adsorb 1–3% of the model component. It is assumed that the adsorption is hindered by the TiO2 layer on the surface of ZIF-8, which blocks the interactions of ZIF-8 and imidacloprid. A significant decrease in band gap energies (3.1–3.6 eV) was observed for the hybrid TiO2/ZIF-8 photocatalysts compared to the values obtained with ZIF-8 (5 eV), depending on the mass fractions of TiO2. The highest removal efficiency of imidacloprid was achieved with the hybrid photocatalysts containing 5 wt% TiO2.
... The possible accumulation of the neonicotinoids in the environment has been found and reported. A study on 48 streams in the USA found that more than 50% of them had more than one neonicotinoid (Hladik and Kolpin 2015). In the Pearl River of Guangzhou, China, the insecticides of acetamiprid, thiamethoxam, imidacloprid, and clothianidin were detected in all 14 sampling sites with a concentration ranged 93-321 ng/L (Yi et al. 2019). ...
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The adsorption and degradation of seven commercially available neonicotinoid insecticides in four types of agricultural soils from three states (Mississippi, Arkansas, and Tennessee) in the USA were studied. The adsorptions of all the neonicotinoids fit a linear isotherm. The adsorption distribution coefficients (Kd) were found to be below 2.0 L/kg for all the neonicotinoids in all the soils from Mississippi and Arkansas. Only in the Tennessee soil samples, the Kd ranged from 0.96 to 4.21 L/kg. These low values indicate a low affinity and high mobility of these insecticides in the soils. The soil organic carbon–water partitioning coefficient Koc ranged from 349 to 2569 L/kg. These Kd values showed strong positive correlations with organic carbon content of the soils. The calculated Gibbs energy change (ΔG) of these insecticides in all the soils ranged from − 14.6 to − 19.5 kJ/mol, indicating that physical process was dominant in the adsorptions. The degradations of all these neonicotinoids in the soils followed a first-order kinetics with half-lives ranging from 33 to 305 days. The order of the insecticides with decreasing degradation rate is as follows: clothianidin > thiamethoxam > imidacloprid > acetamiprid > dinotefuran > thiacloprid > nitenpyram. The moisture content, clay content, and cation exchange capacity showed positive effects on the degradation rate of all the neonicotinoids. The Groundwater Ubiquity Score (GUS) calculated from the adsorption distribution coefficient, organic content, and half-life indicates that, except for thiacloprid, all the neonicotinoids in all the soils are possible leachers, having potentials to permeate into and through groundwater zones.
... In addition, temporally increasing pesticide detection has been reported in urban streams and attributed to increased home and garden use in the urban landscape. 91 Previous studies of effluent and stormwater have documented overall smaller prescription pharmaceutical loadings from stormwater. 9,13,110 Although the overall prescription pharmaceutical load from effluent was greater than from stormwater (34 g) in our study, the individual total metformin load to surface water from stormwater (22 g) was more than 2 times greater than the metformin load contribution from effluent (9.8 g). ...
Global demand for safe and sustainable water supplies necessitates a better understanding of contaminant exposures in potential reuse waters. In this study, we compared exposures and load contributions to surface water from the discharge of three reuse waters (wastewater effluent, urban stormwater, and agricultural runoff). Results document substantial and varying organic-chemical contribution to surface water from effluent discharges (e.g., disinfection byproducts [DBP], prescription pharmaceuticals, industrial/household chemicals), urban stormwater (e.g., polycyclic aromatic hydrocarbons, pesticides, nonprescription pharmaceuticals), and agricultural runoff (e.g., pesticides). Excluding DBPs, episodic storm-event organic concentrations and loads from urban stormwater were comparable to and often exceeded those of daily wastewater-effluent discharges. We also assessed if wastewater-effluent irrigation to corn resulted in measurable effects on organic-chemical concentrations in rain-induced agricultural runoff and harvested feedstock. Overall, the target-organic load of 491 g from wastewater-effluent irrigation to the study corn field during the 2019 growing season did not produce substantial dissolved organic-contaminant contributions in subsequent rain-induced runoff events. Out of the 140 detected organics in source wastewater-effluent irrigation, only imidacloprid and estrone had concentrations that resulted in observable differences between rain-induced agricultural runoff from the effluent-irrigated and nonirrigated corn fields. Analyses of pharmaceuticals and per-/polyfluoroalkyl substances in at-harvest corn-plant samples detected two prescription antibiotics, norfloxacin and ciprofloxacin, at concentrations of 36 and 70 ng/g, respectively, in effluent-irrigated corn-plant samples; no contaminants were detected in noneffluent irrigated corn-plant samples.
... Fewer MICs have been reported for the other neonicotinoid compounds, which can be explained by smaller market shares, later market introduction, limited geographical application area (e.g., dinotefuran is authorized in eight countries only) and generally less scientific attention (Simon-Delso et al., 2015;Borsuah et al., 2020). Also, imidacloprid, clothianidin and thiamethoxam are widely applied as seed coatings in major crops with high concentrations of active ingredients (Hladik and Kolpin, 2016;Goulson, 2013;Douglas and Tooker, 2015), which, in concert with their increased environmental persistence (Table S1), fosters their occurrence in agricultural surface waters. ...
Neonicotinoids are the most widely used insecticides worldwide. However, the widespread usage of neonicotinoids has sparked concerns over their effects on non-target ecosystems including surface waters. We present here a comprehensive meta-analysis of 173 peer-reviewed studies (1998-2022) reporting measured insecticide concentrations (MICs; n = 3983) for neonicotinoids in global surface waters resulting from agricultural nonpoint source pollution. We used compound-specific regulatory threshold levels for water (RTLSW) and sediment (RTLSED) defined for pesticide authorization in Canada, the EU and the US, and multispecies endpoints (MSESW) to assess acute and chronic risks of global neonicotinoid water-phase (MICSW; n = 3790) and sediment (MICSED; n = 193) concentrations. Results show a complete lack of exposure information for surface waters in >90 % of agricultural areas globally. However, available data indicates for MICSW overall acute risks to be low (6.7 % RTLSW_acute exceedances), but chronic risks to be of concern (20.7 % RTLSW_chronic exceedances); exceedance frequencies were particularly high for chronic (63.3 %) MSESW. We found RTLSW exceedances to be highest for imidacloprid and in less regulated countries. Linear model analysis revealed risks for global agricultural surface waters to decrease significantly over time, potentially biased by the lack of sensitive analytical methods in early years of neonicotinoid monitoring. The Canadian, EU and US RTLSW differ considerably (up to factors of 223 for RTLSW_acute and 13,889 for RTLSW_chronic) for individual neonicotinoids, indicating large uncertainties and regulatory challenges in defining robust and protective RTLs. We conclude that protective threshold levels, in concert with increasing monitoring efforts targeting agricultural surface waters worldwide, are essential to further assess the ecological consequences from anticipated increases of agricultural neonicotinoid uses.
Avian decline is occurring globally with neonicotinoid insecticides poised as a potentially contributing factor. Birds can be exposed to neonicotinoids through coated seeds, soil, water, and insects, and experimentally exposed birds can show varied adverse effects including mortality and disruption of immune, reproductive, and migration physiology. However, few studies have characterized exposure in wild bird communities temporally. We hypothesized that neonicotinoid exposure would vary temporally and based on avian ecological traits. Birds were banded and blood sampled at eight non-agricultural sites across four Texas counties. Plasma from 55 species across 17 avian families was analyzed for the presence of 7 neonicotinoids using high performance liquid chromatography-tandem mass spectrometry. Imidacloprid was detected in 36 % of samples (n = 294); this included quantifiable concentrations (12 %; 10.8-36,131 pg/mL) and concentrations that were below the limit of quantification (25 %). Additionally, two birds were exposed to imidacloprid, acetamiprid (18,971.3 and 6844 pg/mL) and thiacloprid (7022.2 and 17,367 pg/mL), whereas no bird tested positive for clothianidin, dinotefuran, nitenpyram, or thiamethoxam, likely reflecting higher limits of detection for all compounds compared to imidacloprid. Birds sampled in spring and fall had higher incidences of exposure than those sampled in summer or winter. Subadult birds had higher incidences of exposure than adult birds. Among the species for which we tested more than five samples, American robin (Turdus migratorius) and red-winged blackbird (Agelaius phoeniceus) had significantly higher incidences of exposure. We found no relationships between exposure and foraging guild or avian family, suggesting birds with diverse life histories and taxonomies are at risk. Of seven birds resampled over time, six showed neonicotinoid exposure at least once with three showing exposures at multiple time points, indicating continued exposure. This study provides exposure data to inform ecological risk assessment of neonicotinoids and avian conservation efforts.
Neonicotinoids are widely used pesticides that contaminate aquatic environments. Although these chemicals can be photolyzed under sunlight radiation, it is unclear for the relationship between photolysis mechanism and toxicity change in aquatic organisms. This study aims to determine the photo-enhanced toxicity of four neonicotinoids with different main structures (acetamiprid, and thiacloprid for cyano-amidine structure, imidacloprid and imidaclothiz for nitroguanidine). To Achieve the goal, photolysis kinetics, effect of dissolved organic matter (DOM) and reactive oxygen species (ROSs) scavengers on photolysis rates, photoproducts, and photo-enhanced toxicity to Vibrio fischeri were investigated for four neonicotinoids. The results showed direct photolysis plays a key role in the photo-degradation of imidacloprid and imidaclothiz (photolysis rate constants are 7.85 × 10-3 and 6.48 × 10-3 min-1, respectively), while the photosensitization process of acetamiprid and thiacloprid was dominated by ·OH reactions and transformation (photolysis rate constants are 1.16 × 10-4 and 1.21 × 10-4 min-1, respectively). All four neonicotinoid insecticides exerted photo-enhanced toxicity to Vibrio fischeri, indicating photolytic product(s) posed greater toxicity than their parent compounds. The addition of DOM and ROS scavengers influenced photo-chemical transformation rates of parent compounds and their intermediates, leading to diverse effects on photolysis rates and photo-enhanced toxicity for the four insecticides as a result of different photo-chemical transformation processes. Based upon the detection of chemical structures of intermediates and Gaussian calculations, we observed different photo-enhanced toxicity mechanisms for the four neonicotinoid insecticides. Molecular docking was used to analyze the toxicity mechanism of parent compounds and photolytic products. A theoretical model was subsequently employed to describe the variability of toxicity response to each of the four neonicotinoids.
The widespread use of neonicotinoid (neonic) insecticides in China's agricultural sector has led to high residual concentrations in the agroecosystem. Since soil is the primary source of direct pesticide exposure, soil contamination is a significant concern, particularly in regions with extensive agricultural production. This study aims to determine the spatial distribution of neonics in farmlands from four southern provinces that are home to China's crucial commercial grain bases. By combining eight neonics into imidacloprid-equivalent total neonics (IMIRPF) using the relative potency factor method, the ecological risks to humans were also assessed. The results showed that imidacloprid had the highest detection rate (96%-100%), followed by thiamethoxam and clothianidin, which ranged from 44% to 64%. Maximum and average IMIRPF values in soil samples from Zhejiang Province were 277.02 and 46.05 μg kg-1 (dry weight), respectively. Guangdong (maximum = 191.62 μg kg-1, mean = 39.70 μg kg-1) and Jiangxi (maximum = 199.13 μg kg-1, mean = 28.95 μg kg-1) had comparable IMIRPF while Jiangsu had the lowest level of total neonics, with a maximum of 86.07 μg kg-1 and a mean of 19.49 μg kg-1. A significant positive correlation between IMIRPF and total organic carbon in soils was also found. The average daily doses of neonics from soil-borne exposure through food intake, soil ingestion, inhalation, and dermal contact calculated for adults and children in each province were all lower than the reference dose (RfD, 57 μg kg-1 d-1) of imidacloprid. However, the potential health risk to human health cannot be disregarded, given their increasing use and pervasiveness in the environment. Our results help to raise concerns about the safety of the agroecological environment under neonic exposure in the major agricultural provinces of southern China.
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Neonicotinoids (NEOs) are a class of insecticides that have high insecticidal activity and are extensively used worldwide. However, increasing evidence suggests their long-term residual in the environment and toxic effects on nontarget organisms. NEO residues are frequently detected in water and consequently have created increasing levels of pollution and pose significant risks to humans. Many studies have conducted surveys of NEO concentrations in water; however, few studies have focused on global systematic reviews or meta-analyses of NEO concentrations in water. In the present study, 43 published papers from 10 countries were indexed for a meta-analysis of the global NEO distribution in water. Among these studies, most focus on eastern Asia and North America, which are involved in intensive agricultural activities. The order of mean concentrations is identified as imidacloprid (119.542 ± 15.656 ng L ⁻¹ ) > nitenpyram (88.076 ± 27.144 ng L ⁻¹ ) > thiamethoxam (59.752 ± 9.068 ng L ⁻¹ ) > dinotefuran (31.086 ± 9.275 ng L ⁻¹ ) > imidaclothiz (24.542 ± 2.906 ng L ⁻¹ ) > acetamiprid (23.360 ± 4.015 ng L ⁻¹ ) > thiacloprid (11.493 ± 5.095 ng L ⁻¹ ). Moreover, the relationship between NEO concentrations and some environmental factors is analyzed. NEO concentrations increase with temperature, oxidation-reduction potential and the percentage of cultivated crops but decrease with stream discharge, pH, dissolved oxygen and precipitation. NEO concentrations show no significant relations to turbidity and conductivity. The purpose of this review is to conduct a meta-analysis on the concentration of NEOs in global waters based on published detections from several countries to extend knowledge on the application of NEOs.
A pilot study among farming households in eastern Iowa was conducted to assess human exposure to neonicotinoids (NEOs). The study was in a region with intense crop and livestock production and where groundwater is vulnerable to surface-applied contaminants. In addition to paired outdoor (hydrant) water and indoor (tap) water samples from private wells, urine samples were collected from 47 adult male pesticide applicators along with the completions of dietary and occupational surveys. Estimated Daily Intake (EDI) were then calculated to examine exposures for different aged family members. NEOs were detected in 53% of outdoor and 55% of indoor samples, with two or more NEOs in 13% of samples. Clothianidin was the most frequently detected NEO in water samples. Human exposure was ubiquitous in urine samples. A median of 10 different NEOs and/or metabolites were detected in urine, with clothianidin, nitenpyram, thiamethoxam, 6-chloronicotinic acid, and thiacloprid amide detected in every urine samples analyzed. Dinotefuran, imidaclothiz, acetamiprid-N-desmethyl, and N-desmethyl thiamethoxam were found in ≥70% of urine samples. Observed water intake for study participants and EDIs were below the chronic reference doses (CRfD) and acceptable daily intake (ADI) standards for all NEOs indicating minimal risk from ingestion of tap water. The study results indicate that while the consumption of private well tap water provides a human exposure pathway, the companion urine results provide evidence that diet and/or other exposure pathways (e.g., occupational, house dust) may contribute to exposure more than water contamination. Further biomonitoring research is needed to better understand the scale of human exposure from different sources.
Neonicotinoid insecticides (NEOs) are widely used in many urban regions. Studies on NEOs residues in urban tidal streams and the associated ecological risks are limited. In this study, the occurrence, spatiotemporal distribution, and ecological risks of seven selected NEOs in the Wuchong Stream in Guangzhou, China were investigated. Moreover, the correlation between typical urban factors and the ecological risk of NEOs was discussed. In the Wuchong Stream, the concentrations of NEOs in the water samples ranged from 0.97 to 175.92 ng. L⁻¹ in the dry season and 3.15 to 312.92 ng. L⁻¹ in the wet season.The most commonly used neonicotionoids were acetamiprid and imidacloprid in the Wuchong Sream basin. The concentrations of NEOs in the midstream were higher than that in the downstream and upstream. The results of the ecological risk indicated that NEOs were likely to biologically impair the urban stream ecosystem, especially in the dry season. For three typical aquatic organisms, the current concentrations of NEOs posed a significant threat to aquatic insects. Compared to other urban factors, residentidal district and farmland area were the main socioeconomic factors affecting the ecological risk of NEOs in the Wuchong Stream basin. Therefore, the correct and reasonable application of NEOs and continuous improvement of the applicant methods can reduce the environmental risks of urban streams.
Technical Report
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Assessment and management of the risks of exposure to complex chemical mixtures in streams are priorities for human and environmental health organizations around the world. The current lack of information on the composition and variability of environmental mixtures and a limited understanding of their combined effects are fundamental obstacles to timely identification and prevention of adverse human and ecological effects of exposure. This report describes the design of a field-based study of the composition and biological activity of chemical mixtures in U.S. stream waters affected by a wide range of human activities and contaminant sources. The study is a collaborative effort by the U.S. Geological Survey and the U.S. Environmental Protection Agency. Scientists sampled 38 streams spanning 24 States and Puerto Rico. Thirty-four of the sites were located in watersheds impacted by multiple contaminant sources, including industrial and municipal wastewater discharges, crop and animal agricultural runoff, urban runoff, and other point and nonpoint contaminant sources. The remaining four sites were minimally development reference watersheds. All samples underwent comprehensive chemical and biological characterization, including sensitive and specific direct analysis for over 700 dissolved organic and inorganic chemicals and field parameters, identification of unknown contaminants (environmental diagnostics), and a variety of bioassays to evaluate biological activity and toxicity.
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Neonicotinoids are the most widely used class of insecticides worldwide, but patterns of their use in the U.S. are surprisingly poorly documented, constraining attempts to understand their role in pest management and potential non-target effects. We synthesized publicly available data to estimate and interpret trends in neonicotinoid use since their introduction in 1994, with a special focus on seed treatments, a major use not captured by the national pesticide-use survey. Neonicotinoid use increased rapidly between 2003 and 2011, as seed-applied products were introduced in field crops, marking an unprecedented shift toward large-scale, preemptive insecticide use: 34-44% of soybeans and 79-100% of corn hectares were treated in 2011. This finding contradicts recent analyses, which concluded that insecticides are used today on fewer corn hectares than a decade or two ago. If current trends continue, neonicotinoid use will increase further through application to more hectares of soybean and other crop species and escalation of per-seed rates. Alternatively, our results, and other recent analyses, suggest that carefully targeted efforts could considerably reduce neonicotinoid use in field crops without yield declines or economic harm to farmers, reducing the potential for pest resistance, non-target pest outbreaks, environmental contamination, and harm to wildlife, including pollinator species.
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Neonicotinoid insecticides have come under scrutiny for their potential unintended effects on non-target organisms, particularly pollinators in agro-ecosystems. As part of a larger study of neonicotinoid residues associated with maize (corn) production, 76 water samples within or around the perimeter of 18 commercial maize fields and neighbouring apiaries were collected in 5 maize-producing counties of southwestern Ontario. Residues of clothianidin (mean = 2.28, max. = 43.60 ng/mL) and thiamethoxam (mean = 1.12, max. = 16.50 ng/mL) were detected in 100 and 98.7% of the water samples tested, respectively. The concentration of total neonicotinoid residues in water within maize fields increased six-fold during the first five weeks after planting, and returned to pre-plant levels seven weeks after planting. However, concentrations in water sampled from outside the fields were similar throughout the sampling period. Soil samples from the top 5 cm of the soil profile were also collected in these fields before and immediately following planting. The mean total neonicotinoid residue was 4.02 (range 0.07 to 20.30) ng/g, for samples taken before planting, and 9.94 (range 0.53 to 38.98) ng/g, for those taken immediately after planting. Two soil samples collected from within an conservation area contained detectable (0.03 and 0.11 ng/g) concentrations of clothianidin. Of three drifted snow samples taken, the drift stratum containing the most wind-scoured soil had 0.16 and 0.20 ng/mL mainly clothianidin in the melted snow. The concentration was at the limit of detection (0.02 ng/mL) taken across the entire vertical profile. With the exception of one sample, water samples tested had concentrations below those reported to have acute, chronic or sublethal effects to honey bees. Our results suggest that neonicotinoids may move off-target by wind erosion of contaminated soil. These results are informative to risk assessment models for other non-target species in maize agro-ecosytems.
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Since their discovery in the late 1980s, neonicotinoid pesticides have become the most widely used class of insecticides worldwide, with large-scale applications ranging from plant protection (crops, vegetables, fruits), veterinary products, and biocides to invertebrate pest control in fish farming. In this review, we address the phenyl-pyrazole fipronil together with neonicotinoids because of similarities in their toxicity, physicochemical profiles, and presence in the environment. Neonicotinoids and fipronil currently account for approximately one third of the world insecticide market; the annual world production of the archetype neonicotinoid, imidacloprid, was estimated to be ca. 20,000 tonnes active substance in 2010. There were several reasons for the initial success of neonicotinoids and fipronil: (1) there was no known pesticide resistance in target pests, mainly because of their recent development, (2) their physicochemical properties included many advantages over previous generations of insecticides (i.e., organophosphates, carbamates, pyrethroids, etc.), and (3) they shared an assumed reduced operator and consumer risk. Due to their systemic nature, they are taken up by the roots or leaves and translocated to all parts of the plant, which, in turn, makes them effectively toxic to herbivorous insects. The toxicity persists for a variable period of time — depending on the plant, its growth stage, and the amount of pesticide applied. Awide variety of applications are available, including the most common prophylactic non-Good Agricultural Practices (GAP) application by seed coating. As a result of their extensive use and physicochemical properties, these substances can be found in all environmental compartments including soil, water, and air. Neonicotinoids and fipronil operate by disrupting neural transmission in the central nervous system of invertebrates. Neonicotinoids mimic the action of neurotransmitters, while fipronil inhibits neuronal receptors. In doing so, they continuously stimulate neurons leading ultimately to death of target invertebrates. Like virtually all insecticides, they can also have lethal and sublethal impacts on non-target organisms, including insect predators and vertebrates. Furthermore, a range of synergistic effects with other stressors have been documented. Here, we review extensively their metabolic pathways, showing how they form both compound-specific and common metabolites which can themselves be toxic. These may result in prolonged toxicity. Considering their wide commercial expansion, mode of action, the systemic properties in plants, persistence and environmental fate, coupled with limited information about the toxicity profiles of these compounds and their metabolites, neonicotinoids and fipronil may entail significant risks to the environment. A global evaluation of the potential collateral effects of their use is therefore timely. The present paper and subsequent chapters in this review of the global literature explore these risks and show a growing body of evidence that persistent, low concentrations of these insecticides pose serious risks of undesirable environmental impacts.
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We assessed the state of knowledge regarding the effects of large-scale pollution with neonicotinoid insecticides and fipronil on non-target invertebrate species of terrestrial, freshwater and marine environments. A large section of the assessment is dedicated to the state of knowledge on sublethal effects on honeybees (Apis mellifera) because this important pollinator is the most studied non-target invertebrate species. Lepidoptera (butterflies and moths), Lumbricidae (earth-worms), Apoidae sensu lato (bumblebees, solitary bees) and the section "other invertebrates" review available studies on the other terrestrial species. The sections on freshwater and marine species are rather short as little is known so far about the impact of neonicotinoid insecticides and fipronil on the diverse invertebrate fauna of these widely exposed habitats. For terrestrial and aquatic invertebrate species, the known effects of neonicotinoid pesticides and fipronil are described ranging from organismal toxicology and behavioural effects to population-level effects. For earthworms, freshwater and marine species, the relation of findings to regulatory risk assessment is described. Neonicotinoid insecticides exhibit very high toxicity to a wide range of invertebrates, particularly insects, and field-realistic exposure is likely to result in both lethal and a broad range of important sublethal impacts. There is a major knowledge gap regarding impacts on the grand majority of invertebrates, many of which perform essential roles enabling healthy ecosystem functioning. The data on the few non-target species on which field tests have been performed are limited by major flaws in the outdated test protocols. Despite large knowledge gaps and uncertainties, enough knowledge exists to conclude that existing levels of pollution with neonicotinoids and fipronil resulting from presently authorized uses frequently exceed the lowest observed adverse effect concentrations and are thus likely to have large-scale and wide ranging negative biological and ecological impacts on a wide range of non-target invertebrates in terrestrial, aquatic, marine and benthic habitats.
Developed to replace organophosphate and carbamate insecticides, neonicotinoids are structurally similar to nicotine. The three main neonicotinoid insecticides, imidacloprid, clothianidin, and thiamethoxam, are being re-evaluated by Health Canada's Pest Management Regulatory Agency (PMRA). An important aspect of the re-evaluation is the potential for effects in non-target organisms, including aquatic organisms. Leaching into surface waters is one of the major concerns surrounding extensive use of neonicotinoids, especially in close proximity to water bodies. The PMRA has classified IMI as ‘persistent’ with a ‘high’ leaching potential. Globally, neonicotinoids have been detected in a variety of water bodies, typically at concentrations in the low μg/L range. While IMI has been included in some monitoring exercises, there are currently very few published data for the presence of CLO and THM in Canadian water bodies. The majority of neonicotinoid toxicity studies have been conducted with IMI due to its longer presence on the market and high prevalence of use. Aquatic insects are particularly vulnerable to neonicotinoids and chronic toxicity has been observed at concentrations of IMI below 1 μg/L. Acute toxicity has been reported at concentrations below 20 μg/L for the most sensitive species, including Hyalella azteca, ostracods, and Chironomus riparius. Fish, algae, amphibians, and molluscs are relatively insensitive to IMI. However, the biological effects of THM and CLO have not been as well explored. The Canadian interim water quality guideline for IMI is 0.23 μg/L, but there is currently insufficient use, fate, and toxicological information available to establish guidelines for CLO and THM. Based on concentrations of neonicotinoids reported in surface waters in Canada and globally, there is potential for aquatic invertebrates to be negatively impacted by neonicotinoids. Therefore, it is necessary to address knowledge gaps to inform decisions around guidelines and registration status for neonicotinoid insecticides in Canada to protect our aquatic ecosystems.
Neonicotinoids are now the most widely used insecticides in the world. They act systemically, travelling through plant tissues and protecting all parts of the crop, and are widely applied as seed dressings. As neurotoxins with high toxicity to most arthropods, they provide effective pest control and have numerous uses in arable farming and horticulture.However, the prophylactic use of broad-spectrum pesticides goes against the long-established principles of integrated pest management (IPM), leading to environmental concerns.It has recently emerged that neonicotinoids can persist and accumulate in soils. They are water soluble and prone to leaching into waterways. Being systemic, they are found in nectar and pollen of treated crops. Reported levels in soils, waterways, field margin plants and floral resources overlap substantially with concentrations that are sufficient to control pests in crops, and commonly exceed the LC50 (the concentration which kills 50% of individuals) for beneficial organisms. Concentrations in nectar and pollen in crops are sufficient to impact substantially on colony reproduction in bumblebees.Although vertebrates are less susceptible than arthropods, consumption of small numbers of dressed seeds offers a route to direct mortality in birds and mammals.Synthesis and applications. Major knowledge gaps remain, but current use of neonicotinoids is likely to be impacting on a broad range of non-target taxa including pollinators and soil and aquatic invertebrates and hence threatens a range of ecosystem services.
Recent studies have shown that neonicotinoid insecticides have adverse effects on non-target invertebrate species. Invertebrates constitute a substantial part of the diet of many bird species during the breeding season and are indispensable for raising offspring. We investigated the hypothesis that the most widely used neonicotinoid insecticide, imidacloprid, has a negative impact on insectivorous bird populations. Here we show that, in the Netherlands, local population trends were significantly more negative in areas with higher surface-water concentrations of imidacloprid. At imidacloprid concentrations of more than 20 nanograms per litre, bird populations tended to decline by 3.5 per cent on average annually. Additional analyses revealed that this spatial pattern of decline appeared only after the introduction of imidacloprid to the Netherlands, in the mid-1990s. We further show that the recent negative relationship remains after correcting for spatial differences in land-use changes that are known to affect bird populations in farmland. Our results suggest that the impact of neonicotinoids on the natural environment is even more substantial than has recently been reported and is reminiscent of the effects of persistent insecticides in the past. Future legislation should take into account the potential cascading effects of neonicotinoids on ecosystems.