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Re: Roundup information
Dave Riches wrote:
>
> <snip>
>
> I have no experience with your other points, thus am unqualified to
> comment. However, I would like to point out that glyphosate will
> probably go down in history as modern farming's safest and most
> effective single product. End of story.
Independent studies show roundup just as bad as the others.
Glyphosate, Part 2: Human Exposure and
Ecological Effects. Caroline Cox. Journal of
Pesticide Reform, Volume 15, Number 4, Winter
1995. Northwest Coalition for Alternatives to
Pesticides, Eugene, OR.
Glyphosate, Part 2: Human Exposure and Ecological Effects
by Caroline Cox
OVERVIEW
Residues of the commonly-used herbicide glyphosate have been
found in a variety of fruits and vegetables. Residues can be
detected long after glyphosate treatments have been made.
Lettuce, carrots, and barley planted a year after glyphosate
treatment contained residues at harvest.
In California, where reporting of pesticide-caused illnesses
is more comprehensive than in other states, glyphosate
exposure was the third most commonly-reported cause of
pesticide illness among agricultural workers. For landscape
maintenance workers, glyphosate ranked highest.
Glyphosate can drift away from the site of its application.
Maximum drift distance of 400 to 800 meters (1300-2600 feet)
have been measured.
Glyphosate residues in soil have persisted over a year.
Although not expected for an herbicide, glyphosate exposure
damages or reduces the population of many animals, including
beneficial insects, fish, birds, and earthworms. In some
cases glyphosate is directly toxic; for example,
concentrations as low as 10 parts per million can kill fish
and 1/20 of typical application rates caused delayed
development in earthworms. In other cases, (small mammals and
birds, for example) glyphosate reduces populations by
damaging the vegetation that provides food and shelter for
the animals.
Glyphosate reduces the activity of nitrogen-fixing bacteria.
These bacteria transform nitrogen, an essential plant
nutrient, into a form that plants can use. Glyphosate reduces
the growth of mycorrhizal fungi, beneficial fungi that help
plants absorb water and nutrients. Glyphosate also increases
the susceptibility of plants to diseases, including
Rhizoctonia root rot, take-all disease, and anthracnose.
-------------------------------------------------------
Glyphosate is a widely-used, broad-spectrum herbicide that is
used to kill unwanted plants in a wide variety of
agricultural, lawn and garden, aquatic, and forestry
situations. It ranks among the top ten herbicides used in the
U.S., both in agricultural and nonagricultural situations.
Common brand names are Roundup, Rodeo, Accord, and Vision.
This is the second part of a summary of glyphosate's hazards.
Part 1 (JPR 15(3):14-20) discussed the toxicology of
glyphosate, its breakdown products, and the other ingredients
in glyphosate-containing products. This part discusses human
exposure to glyphosate and its ecological effects.
Human Exposure
The most important ways that people are exposed to glyphosate
are through workplace exposure (for people who use glyphosate
products on the job), eating of contaminated food, exposure
caused by off-target movement following application (drift),
contact with contaminated soil, and drinking or bathing in
contaminated water. The next five sections of this factsheet
summarize information about these five routes of exposure.
The third section, discussing drift, also covers impacts on
plants.
Contamination of Food
Analysis of glyphosate residues is "in general laborious,
complex, and costly."1 For this reason, it is not included in
government monitoring of pesticide residues in food.1 The
only information available about contamination of food comes
from research situations. Such studies demonstrate several
important points:
* First, glyphosate can be taken up by plants and moved to
parts of the plant that are used for food. For example,
glyphosate has been found in strawberries,2 wild blueberries
and raspberries,3 lettuce, carrots, barley,4 and fish5,6
following treatment.
* Second, pre-harvest use of glyphosate on wheat (to dry out
the grain prior to harvest) results in "significant residues
in the grain,"1 according to the World Health Organization.
Bran contains between 2 and 4 times the amount on whole
grains. Residues are not lost during baking.1
* Third, glyphosate residues can be found in food long after
treatments have been made. For example, lettuce, carrots, and
barley contained glyphosate residues at harvest when planted
a year after treatment.4
Occupational Exposure
Workers in a variety of occupations are exposed to
glyphosate. Researchers have documented exposure for forestry
workers in Finland7 and the southeastern U.S., palm
plantation workers in Malaysia1 and conifer nursery workers
in Mississippi and Oregon.8 All of these studies generally
found low, but consistent, exposure rates.
Physicians, however, paint a different picture. In
California, the state with the most comprehensive program for
reporting of pesticide-caused illness, glyphosate was the
third most commonly-reported cause of pesticide illness among
agricultural workers.9 Among landscape maintenance workers,
glyphosate was the most commonly reported cause.10 (Both
these statistics come from reviews of illness reports
collected between 1984 and 1990.) Even when glyphosate's
extensive use in California is considered, and the illness
statistics presented as "number of acute illnesses reported
per million pounds used in California," glyphosate ranked
twelfth.9
Drift
In general, movement of a pesticide through unwanted drift is
"unavoidable."11 Drift of glyphosate is no exception.
Glyphosate drift, however, is a particularly significant
problem. Its wide use means that there is a correspondingly
large potential for drift.12 When drift does occur, "damage
is likely to be much more extensive and more persistent than
with many other herbicides."13 This is because glyphosate
translocates (moves) within plants readily so that even
unexposed parts of a plant can be damaged. Damage to
perennial plants (when not exposed to enough glyphosate to
kill them) is persistent, with some symptoms lasting several
years.13 In addition, plant susceptibility varies widely.
Some wildflowers are almost a hundred times more sensitive
than others; small amounts of drift will damage these
species.14
A fundamental question about drift is "How far can I expect
glyphosate to travel off-site?" Unfortunately, the question
is difficult to answer, since drift is "notoriously
variable."15 Factors that increase drift are aerial
application techniques, high wind speeds (over 10 kilometers,
or 6 miles, per hour), spray nozzles that produce a high
proportion of fine droplets, and calm conditions (without
enough turbulence to drive the glyphosate droplets onto plant
foliage).15 Drift distances that have been measured for the
major application techniques include the following:
* Ground Applications: Between 14 and 78 percent of
glyphosate applied as ground sprays moves off-site.15
Seedling mortality has been demonstrated 20 meters (66 feet)
downwind when using a tractor-mounted sprayer. Sensitive
species were killed at 40 meters (131 feet).16 Models
indicate that even more sensitive species would be killed at
distances approaching 100 meters (328 feet).14 Glyphosate
residues have been measured 400 meters (1312 feet) downwind
from ground applications.17
* Helicopter applications: Between 41 and 82 percent of
glyphosate applied from helicopters moves off the target
site.15 Two studies done in Canada18,19 measured glyphosate
residues 200 meters (656 feet) from target areas following
helicopter applications to forest sites. In both studies, 200
meters was the farthest distance at which samples were taken,
so the longest distance glyphosate travelled is not
known.18,19 A third study (from California) found glyphosate
800 meters (2624 feet) downwind following a helicopter
application. Again, this was the farthest distance at which
measurements were made. Plant injury was recorded 400 meters
(1312 feet) downwind.17
Fixed-wing aircraft: Long drift distances occur following
applications of glyphosate made from fixed-wing airplanes.
Three studies on forested sites conducted by Agriculture
Canada (the Canadian agricultural ministry) showed that
glyphosate was consistently found at the farthest distance
from the target areas that measurements were made (200, 300,
and 400 meters, or 656, 984, and 1312 feet).20-22 A
California study found glyphosate 800 meters downwind of an
airplane application. Again, this was the farthest distance
at which measurements were made. Plant injury was observed at
100 meters (328 feet). Unlike the first three studies, this
study used a grass field as the test site.17
One of the Canadian studies22 calculated that buffer zones of
between 75 and 1200 meters (246 feet - 0.75 miles) would be
required to protect nontarget vegetation.
Soil Contamination
Persistence: Glyphosate's persistence in soil varies widely,
so giving a simple answer to the question "How long does
glyphosate persist in soil?" is not possible. Half-lives (the
time required for half of the amount of glyphosate applied to
break down or move away) as low as 3 days and as long as 141
days have been measured by glyphosate's manufacturer.4
Initial degradation (breakdown) is faster than the subsequent
degradation of what remains, resulting in long persistence.23
Long persistence has been measured in the following studies:
55 days on an Oregon Coast Range forestry site24; 249 days on
Finnish agricultural soils25; between 259 and 296 days on
eight Finnish forestry sites23; 335 days on an Ontario
(Canada) forestry site26; 360 days on 3 British Columbia
forestry sites27; and, from 1 to 3 years on eleven Swedish
forestry sites.28 These are minimum estimates because, in all
but two of these studies, glyphosate was detected on the last
date samples were analyzed.
Glyphosate is thought to be "readily bound to many soils and
clay minerals"1 and therefore "immobile or slightly immobile
in many soils."1 This means that the glyphosate will be
unlikely to move away from the application site and
contaminate water or soil elsewhere. However, a new study29
paints a different picture. The researchers found that
glyphosate bound readily to the four soils studied. However,
desorption, when glyphosate unbinds from soil particles, also
occurred readily. In one soil, 80 percent of the added
glyphosate desorbed in a two hour period. The study concludes
that "this herbicide can be extensively mobile in the soil
environment.."29
Water Contamination
Based on the prevailing view that glyphosate binds readily to
soil particles, it does not have the chemical characteristics
of a pesticide that is likely to leach into either ground or
surface water.1 (If it readily desorbs, as described above,
this picture would change.) In either case, glyphosate can
move into surface water when the soil particles to which it
is bound are washed into streams or rivers.4 How often this
happens is not known, because routine monitoring for
glyphosate in water is infrequent.1
However, glyphosate has been found in both ground and surface
water. Examples include two farm ponds in Ontario, Canada,
contaminated by run-off from an agricultural treatment (one
pond) and a spill (the other pond)30; the run-off from a
watersheds treated with Roundup during production of no-till
corn and fescue31; contaminated surface water in the
Netherlands1; and seven U.S. wells (one in Texas, six in
Virginia) contaminated with glyphosate.32
Glyphosate's persistence in water is shorter than its
persistence in soils. Two Canadian studies found glyphosate
persisted 12 to 60 days in pond water following direct
application.33,34 Glyphosate persists longer in sediments.
For example, a study of Accord applied to forest ponds found
glyphosate residues in sediment 400 days after application.1
The half-life in pond sediments in a Missouri study was 120
days; persistence was over a year in pond sediments in
Michigan and Oregon.4
Ecological Effects
Glyphosate can impact many organisms not intended as targets
of the herbicide. The next two sections describe both direct
mortality and indirect effects, through destruction of food
or shelter.
Effects on Nontarget Animals
Beneficial insects: Glyphosate-containing products pose
hazards to insects that are economically beneficial because
they kill pest insects. The International Organization for
Biological Control found that exposure to freshly dried
Roundup killed over 50 percent of three species of beneficial
insects: a parasitoid wasp, a lacewing, and a ladybug.35 Over
80 percent of a fourth species, a predatory beetle, was
killed.
Similar impacts on beneficial insects have been shown in
field studies. In North Carolina winter wheat fields,
populations of large carabid beetles declined after treatment
with a commercial glyphosate product and did not recover for
28 days.36 A study of Roundup treatment of pasture hedgerows
in the United Kingdom showed a similar decline in carabid
beetles.37
Roundup treatment of a Maine clear-cut caused an 89 percent
decline in the number of herbivorous (plant-eating) insects.
While these are not usually considered beneficial insects,
they serve as an important food resource for birds and
insect-eating small mammals.38
Aquatic insects can also be affected by glyphosate. Midge
larvae (important food for breeding waterfowl39) are killed
by glyphosate in amounts that vary widely. For example, one
study found that 55 parts per million (ppm) of glyphosate
killed midge larvae6 while other studies found that 65040
-560039 ppm of Rodeo (containing glyphosate and water) were
required to kill the larvae. Part of the variability is
related to water hardness.39
The U.S. Fish and Wildlife Service has identified one
endangered species of insect, a longhorn beetle, that would
be jeopardized by use of glyphosate.41
Other arthropods: Glyphosate and glyphosate-containing
products kill a variety of other arthropods. For example,
over 50 percent of test populations of a predatory mite that
is an important predator of pest mites was killed by exposure
to Roundup.35 In another laboratory study, Roundup exposure
caused a decrease in survival and a decrease in body weight
of woodlice. These arthropods are important in humus
production and soil aeration.42 Roundup treatment of pasture
hedgerows reduced the number of spiders, probably by killing
the plants they preferred for web-spinning.37 The water flea
Daphnia pulex is killed by concentrations of Roundup between
3 and 25 ppm.6,43,44 Young Daphnia are more susceptible than
mature individuals, and suspended sediments in the water
increased the toxicity.43 The red swamp crawfish, a
commercial species, was killed by 47 ppm of Roundup.45
Fish: Both glyphosate and the commercial products that
contain glyphosate are acutely toxic to fish. In general,
glyphosate alone is less toxic than the common glyphosate
product, Roundup, and other glyphosate products have
intermediate toxicity. Part of these differences in toxicity
to fish can be explained by the toxicity of the surfactant
(detergent-like ingredient) in Roundup. It is about 30 times
more toxic to fish than glyphosate itself.44
Acute toxicities of glyphosate vary widely: median lethal
concentrations (LC50s; the concentrations killing 50 percent
of a population of test animals) from 10 ppm to over 1000 ppm
have been reported depending on the species of fish and test
conditions.1 In soft water there is little difference between
the toxicities of glyphosate and Roundup.
Acute toxicities of Roundup to fish range from an LC50 of 3.2
ppm to an LC50 of 52 ppm.1 Acute toxicities of Rodeo (used
with the surfactant X-77 per label recommendations) vary from
120 to 290 ppm.46
Factors important in determining the toxicity of glyphosate
or glyphosate-containing products to fish include the
following:
* First, different species of fish have different
susceptibilities. For example, coho and chinook salmon are
more tolerant of glyphosate than pink or chum salmon.47
* Water quality is important: glyphosate in soft water was 20
times more toxic to rainbow trout than was glyphosate in hard
water. For Roundup, the reverse is true: it is more toxic in
hard water than in soft.47,48
* Age affects the susceptibility of fish because juveniles
are often more susceptible than adults. For example, Roundup
was four times more toxic to rainbow trout fry and
fingerlings than it was to larger fish.6
* Nutrition also can determine toxicity. Hungry fish are more
susceptible to glyphosate than fed fish. For example, fed
flagfish were 10 times more tolerant of glyphosate than unfed
fish.49
* Finally, glyphosate toxicity increases with increased water
temperature. In both rainbow trout and bluegills, toxicity
about doubled between 7 and 17!C (45 and 63!F).6 Treatment of
riparian areas with glyphosate causes water temperatures to
increase for several years following treatment50 because the
herbicide kills shading vegetation. This means that repeated
use of glyphosate in a watershed could favor its increased
toxicity to fish. In addition, the temperature increase
itself could be critical for fish, like juvenile salmon, that
are sensitive to water temperature.
Sublethal effects of glyphosate on fish are also significant
and occur at low concentrations. Studies of rainbow trout and
Tilapia found that concentrations of about 1/2 and 1/3 of the
LC50 (respectively) caused erratic swimming.51,52 The trout
also exhibited labored breathing.51 Behavioral effects can
increase the risk that the fish will be eaten, as well as
affecting feeding, migration, and reproduction.52
Birds: Glyphosate is acutely toxic to birds, but only in
large amounts. The LC50, the amount in food that kills 50
percent of a population of test animals, is often above 4000
milligrams per kilogram of food.1
Glyphosate also has indirect impacts on birds. Because
glyphosate kills plants, its use creates a dramatic change in
the structure of the plant community. This affects bird
populations, since the birds depend on the plants for food,
shelter, and nest support.
For example, a study of four glyphosate-treated clear-cuts
(and an unsprayed control plot) in Nova Scotia found that the
densities of the two most common species of birds (white-
throated sparrow and common yellowthroat) decreased for two
years after glyphosate treatment. By the fourth year post-
spray, densities had returned to normal for these two
species. However, the unsprayed plot had by then been
colonized by new species of birds (warblers, vireos, and a
hummingbird). These species did not appear on the sprayed
plots.53
An earlier three year study of songbird abundance following
glyphosate treatment of clear-cuts in Maine forests showed
similar results. Abundances of the total number of birds
(Figure 2) and three common species decreased. The decrease
in bird abundance was correlated with decrease in the
diversity of the habitat.54
Black grouse avoided glyphosate-treated clear-cuts in Norway
for several years after treatment.55 Researchers recommended
that the herbicide not be used near grouse courtship areas.
Small mammals: In field studies, small mammals have also been
indirectly affected when glyphosate kills the vegetation they
(or their prey) use for food or shelter. This was first shown
in studies of clear-cuts in Maine.38 Insect-eating shrews
declined for three years post-treatment; plant-eating voles
declined for two. A second study in Maine56 found similar
results for voles, but not shrews. A British Columbia study
found that deer mice populations were dramatically (83
percent) lower following glyphosate treatment.57 While some
other studies have found no affect on mice, this may have
occurred because treated areas were small.1 This suggests
that effects are more severe when large areas are treated.
In Norway, there was a "strong reduction" in use of sprayed
clear-cuts by mountain hare.58
Earthworms: A study of the most common earthworm found in
agricultural soils in New Zealand showed that glyphosate
significantly affects growth and survival of earthworms.
Repeated biweekly applications of low rates of glyphosate
(1/20 of typical rates) caused a reduction in growth, an
increase in the time to maturity, and an increase in
mortality.59
Effects on Nontarget Plants
As a broad-spectrum herbicide, glyphosate has potent acutely
toxic effects on most plant species. However, there are other
kinds of serious effects. These include effects on endangered
species, reduction in the ability to fix nitrogen, increased
susceptibility to plant diseases, and reduction in the
activity of mycorrhizal fungi.
Endangered species: Because essentially all plants are
susceptible to glyphosate-caused damage or mortality,
glyphosate can seriously impact endangered plant species. The
U.S. Fish and Wildlife Service has identified 74 endangered
plant species that it believes could be jeopardized by use of
glyphosate. This list is based on the use of glyphosate on 9
crops, and does not include over 50 other uses.41
Nitrogen fixation: Nitrogen is important because of its "near
omnipresence" in membranes, proteins, and genetic material of
living things. Most living things cannot use nitrogen in its
common form and instead use ammonia and nitrates, much rarer
compounds. The processes by which ammonia and nitrates are
created are called nitrogen fixation and nitrification. They
are carried out by certain bacteria.60
A number of studies (from Iowa,61 Australia,62 eastern
Canada,63 and Ontario (Canada)64,65) have shown that
commercial glyphosate products can reduce nitrogen-fixing or
nitrification activity of soils. The amount of glyphosate
that produces inhibitory effects varies from 262 to 200063
ppm. Effects can be persistent; the formation of nitrogen-
fixing nodules on clover roots was inhibited 120 days after
treatment. 62
In addition, tests of cultured nitrogen-fixing bacteria have
also shown that glyphosate inhibits nitrogen-fixation. These
studies included the nitrogen-fixing species in roots of
soybeans66 and clover.67-68
Given the importance of nitrogen-fixation to agriculture,
more research is crucial.
Mycorrhizal fungi: Mycorrhizal fungi are beneficial fungi
that live in and around plant roots. They help plants absorb
nutrients and water and can protect them from cold and
drought.69 Glyphosate is toxic to many species of mycorrhizal
fungi. Effects, mostly growth inhibition, have been observed
at concentrations between 1 and 100 ppm.70-73
Plant diseases: Glyphosate treatment increases the
susceptibility of crop plants to a number of diseases. For
example, glyphosate reduced the ability of bean plants to
defend themselves against the disease anthracnose.74
Glyphosate increased the growth of take-all disease in soil
from a wheat field. In addition, the proportion of soil fungi
which was antagonistic to the take-all fungus decreased.75
Bean seedlings also survived glyphosate treatment when grown
on sterile soil, but not when grown on normal (not
sterilized) soil.76 Spraying of Roundup prior to planting
barley increased the severity of Rhizoctonia root rot and
decreased barley yield.77 In addition, Roundup injection of
lodgepole pine inhibited the defensive response of the tree
to blue stain fungus.78
References
1. World Health Organization, United Nations Environment
Programme, International Labour Organization. 1994.
Glyphosate. Environmental Health Criteria #159. Geneva,
Switzerland.
2. Cessna, A.J. and N.P. Cain. 1992. Residues of glyphosate
and its metabolite AMPA in strawberry fruit following spot
and wiper applications. Can. J. Plant Sci. 72: 1359-1365.
3. Roy, D.N. et al. 1989. Uptake and persistence of the
herbicide glyphosate (Vision?) in fruit of wild blueberry and
red raspberry. Can. J. For. Res. 19: 842-847.
4. U.S. EPA. Office of Pesticide Programs. Special Review
and Reregistration Division. 1993. Reregistration eligibility
decision (RED): Glyphosate. Washington, D.C. (September.)
5. Wang, Y., C. Jaw, and Y. Chen. 1994. Accumulation of 2,4-
D and glyphosate in fish and water hyacinth. Water Air Soil
Pollut. 74: 397-403.
6. Folmar, L.C., H.O. Sanders, and A.M. Julin. 1979.
Toxicity of the herbicide glyphosate and several of its
formulations to fish and aquatic invertebrates. Arch.
Environ. Contam. Toxicol. 8:269-278.
7. Jauhiainen, A., et al. 1991. Occupational exposure of
forest workers to glyphosate during brush saw spraying work.
Am. Ind. Hyg. Assoc. J. 52(2):61-64.
8. Lavy, T.L. et al. 1993. Measurements of year-long
exposure to tree nursery workers using multiple pesticides.
Arch. Environ. Contam. Toxicol. 24:123-144.
9. Pease, W.S. et al. 1993. Preventing pesticide-related
illness in California agriculture: Strategies and priorities.
Environmental Health Policy Program Report. Berkeley, CA:
University of California. School of Public Health. California
Policy Seminar.
10. Robinson, J.C. et al. 1994. Pesticides in the home and
community: Health risks and policy alternatives.
Environmental Health Policy Program Report. Berkeley, CA:
University of California. School of Public Health. California
Policy Seminar.
11. Ware, G.W. et al. 1983. Reducing pesticide application
drift-losses. Tucson, AZ: University of Arizona. College of
Agriculture. Cooperative Extension Service.
12. Payne, N.J. 1992. Off-target glyphosate from aerial
silvicultural applications and buffer zones required around
sensitive areas. Pestic. Sci. 34:1-8.
13. Atkinson, D. 1985. Glyphosate damage symptoms and the
effects of drift. Appendix I. In Grossbard, E. and D.
Atkinson. The herbicide glyphosate. London: Butterworths.
14. Breeze, V., G. Thomas, and R. Butler. 1992. Use of a
model and toxicity data to predict the risks to some wild
plants from drift of four herbicides. Ann. Appl. Biol.
121:669-677.
15. Freedman, B. 1990-1991. Controversy over the use of
herbicides in forestry, with particular reference to
glyphosate usage. J. Envir. Sci. Hlth. C8(2):277-286.
16. Marrs, R.H. et al. 1993. Determination of buffer zones to
protect seedlings of non-target plants from the effects of
glyphosate spray drift. Agric. Ecosys. Environ. 45:283-293.
17. Yates, W.E., N.B. Akesson, and D.E. Bayer. 1978. Drift of
glyphosate sprays applied with aerial and ground equipment.
Weed Sci. 26(6):597-604.
18. Riley, C.M., C.J. Weisner, and W.A. Sexsmith. 1991.
Estimating off-target spray deposition on the ground
following the aerial application of glyphosate for conifer
release in New Brunswick. J. Environ. Sci. Health B26(2):185-
208.
19. Payne, N.J., J.C. Feng, and P.E. Reynolds. 1990. Off-
target depositions and buffer zones required around water for
aerial glyphosate applications. Pestic. Sci. 30:183-198.
20. Payne, N.J. and D.G. Thompson. 1992. Off-target
glyphosate deposits form aerial silvicultural applications
under various meteorological conditions. Pestic. Sci. 34:53-
59.
21. Payne, N.J. 1993. Spray dispersal from aerial
silvicultural applications. Crop Protec. 12(6):463-469.
22. Payne, N.J. 1992. Off-target glyphosate from aerial
silvicultural applications, and buffer zones required around
sensitive areas. Pestic. Sci. 34:1-8.
23. Torstensson, L. and Stark, J. 1979. Persistence of
glyphosate in forest soils. In Weeds and weed control. 20th
Swedish Weed Conference. Uppsala. 31 January - 2 February
1979. Uppsala, Sweden: Swedish University of Agricultural
Sciences.
24. Newton, M. et al. 1984. Fate of glyphosate in an Oregon
forest ecosystem. J. Agric. Food. Chem. 32:1144-1151.
25. Mller, M. et al. 1981. Fate of glyphosate and its
influence on nitrogen-cycling in two Finnish agricultural
soils. Bull. Environ.. Contam. Toxicol. 27:724-730.
26. Feng, J.C. and D.G. Thompson. 1990. Fate of glyphosate in
a Canadian forest watershed. 2. Persistence in foliage and
soils. J. Agric. Food. Chem. 38: 1118-1125.
27. Roy, D.N. et al. 1989. Persistence, movement, and
degradation of glyphosate in selected Canadian boreal forest
soils. J. Agric. Food. Chem. 37:437-440.
28. Torstensson, N.T.L., L.N. Lundgren, and J. Stenstrm.
1989. Influence of climate and edaphic factors on persistence
of glyphosate and 2,4-D in forest soils. Ecotoxicol. Environ.
Safety 18:230-239.
29. Piccolo, A. et al. 1994. Adsorption and desorption of
glyphosate in some European soils. J. Environ. Sci. Health
B29(6): 1105-1115.
30. Frank, R. et al. 1990. Contamination of rural ponds with
pesticide, 1971-1985, Ontario, Canada. Bull. Environ. Contam.
Toxicol. 44:401-409.
31. Edwards, W.M., G.B. Triplett, Jr., and R.M. Kramer. 1980.
A watershed study of glyphosate transport in runoff. J.
Environ. Qual. 9(4):661-
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- From: nntp-xfer.ncsu.edu!gatech!www.nntp.primenet.com!nntp.primenet.com!cs.utexas.edu!news-peer.sprintlink.net!news-west.sprintlink.net!Sprint!news.sprintlink.net!news-ana-24.@ultra150.ncren.net
- Re: Roundup information
- From: unc-cs!ultra150.ncren.net!nntp-xfer.ncsu.edu!gatech!howland.erols.net!newsfeed.internetmci.com!news.telstra.net!sa.news.telstra.net!hermes.chariot.net.au!don%chariot.net.au@fddinewz.oit.unc.