permaculture

["Lawrence F. London, Jr." <lfl@intrex.net>]

Subject: atrazine poisoning worse than suspected
Date: Sat, 9 Nov 2002 09:12:24 -0500
From: jcummins <jcummins@UWO.CA>
To: SANET-MG@LISTS.IFAS.UFL.EDU

Controversy erupted over new findings that atrazine may be linked to
global demise of frogs. Prof. Joe Cummins and Dr. Mae-Wan Ho review the
evidence on the endocrine-disrupting and carcinogenic effects of
atrazine, especially in the light of the non-linearity of biological
activities, and call for a global ban of the herbicide.

Atrazine Poisoning Worse Than Suspected

Controversy erupted over new findings that atrazine may be linked to
global demise of frogs. Prof. Joe Cummins and Dr. Mae-Wan Ho review the
evidence on the endocrine-disrupting and carcinogenic effects of
atrazine, especially in the light of the non-linearity of biological
activities, and call for a global ban of the herbicide.

Atrazine is an herbicide registered in the United States for the control
of broadleaf weeds and some grassy weeds. It is currently used on corn,
sorghum, sugarcane, wheat (to get rid of wheat stubble on fallow land
following wheat harvests; wheat is not the target crop), guava,
macadamia nuts, orchard grass and hay, range grasses, and southern turf
grasses. Atrazine is most widely used on corn followed by sorghum and
sugarcane. Atrazine is registered for use on range grasses for
establishing permanent grass cover on rangelands and pastures under the
Conservation Reserve Program (CRP) in four states: Oklahoma, Nebraska,
Texas, and Oregon. The CRP is administered by the US Department of
Agriculture (USDA).

There are prohibitions against grazing on these CRP lands, and cutting
the grasses for hay, except in national emergencies, such as severe
drought, and there are "right-of-way" uses with grazing restrictions.
Atrazine is also registered for use on the following non-agricultural
sites: lawns, golf courses, and sod farms. Worlwide, atrazine is a
leading agricultural chemical, and so extensively used that it has been
identified as a significant pollutant in surface water, groundwater, in
offshore areas and in the atmosphere.

Atrazine acts by inhibiting photosynthesis. Many atrazine-tolerant
mutations have begun to appear in weeds, and this tolerance is
predominantly based on detoxifying atrazine by binding it to
glutathione, a mechanism in naturally atrazine-tolerant corn. Efforts
have been made to select or produce atrazine-tolerant mutants crops such
as soybean that is otherwise difficult to rotate with atrazine-treated
corn or potato.

Most of the crop-plant mutants had impaired productivity, but in potato,
an atrazine-binding photosynthetic protein is mutated, and this makes it
tolerant to the herbicide without impaired productivity. Transgenic
potato containing a complex of human cytochrome p450 genes was found to
be tolerant to atrazine, and was proposed for phytoremediation of
chemically polluted croplands. Unfortunately, the cytochrome p450
enzymes are very important in metabolism of man-made chemicals, they
both inactivate many carcinogens, and in some instances, activate
pollutants to form carcinogens. Atrazine is used worldwide, but its
continued application is hampered by appearance of atrazine-tolerant weeds.

Atrazine was in the news recently in connection with the global demise
of frogs. Frogs were reported to be demasculinized or became
hermaphrodite after being exposed at low ecologically relevant doses of
the herbicide in the laboratory. Levels as low as 0.1 parts per billion
atrazine induced hermaphroditism. This was confirmed by fuller
ecological evidence that atrazine is associated with hermaphroditism in
frogs at levels an order of magnitude below the currently accepted standard.

Those findings were criticized on several grounds, but mainly on the
basis that very low levels of atrazine produced a stronger impact than
levels 250 times higher, and that the low levels of atrazine did not
induce the cytochrome p450 enzyme aromatase. Such criticism is
significant, but should be considered in the light that endocrine
disrupting chemicals often have more marked effect at lower doses, and
the enzyme aromatase, though important in producing the feminizing
hormone estrogen, shows complex cellular patterns of activation in
animals exposed to feminizing pollutants.

The endocrine-disrupting effects of atrazine are not restricted to
frogs. Atrazine reduced olfactory-mediated endocrine functions in salmon
at levels commonly observed in polluted water. And it was found to
inhibit testosterone production in prepubertal rats.

The impact of atrazine on endocrine disruption is very serious. A study
of aquatic ecosystems concluded that a single universal maximum on
atrazine in catchments does not provide adequate environmental
protection, and suggests flexible limits be set. However, it may be far
more reasonable to discuss eliminating further atrazine input into the
aquatic environment altogether.

Another important factor that is almost never considered in
environmental risk assessment is that biological activities are
predominantly nonlinear: weak forces or extremely low concentrations of
a chemical may have disproportionately large effects at times, and
conversely, strong forces or high concentrations of the chemical may
have no effects at all.

The debate over the biological effects of trace chemical pollutants,
which Rachel Carson began some fifty years ago, is getting to resemble
the debate over the biological effects of weak electromagnetic fields
that erupted in the 1970s, and more recently the effects of microwaves
emanating from mobile phones and antennas. It is symptomatic of the
basic inadequacy of the linear, mechanistic model of living systems that
still dominates the scientific establishment, at a time when scientists
across the disciplines are already working with non-linear dynamical
models and even quantum coherent models of living systems.

It has not escaped our notice that in homeopathy, more dilute
concentrations of substances are said to be ‘potentised’, and expected
to produce stronger effects, or in any case, effects opposite to what
the same substance would produce at high concentrations. That, too,
could fall within the spectrum of nonlinear behaviour of living systems,
although it is much more difficult to explain.

Andrew Marino and his coworkers in LSU Health Science Center,
Shreveport, Louisiana, have recently devised nonlinear statistical
methods for analyzing the biological effects of weak electromagnetic
fields that may be relevant to a range of data including the
endocrine-disrupting effects of atrazine and other environmental pollutants.

The International Agency for Research on Cancer determined that there is
sufficient evidence for the carcinogenicity of atrazine in animals, but
not in humans. The United States Environmental Protection Agency (EPA)
concluded that the cancer studies showing atrazine carcinogenic in
animals were not applicable to human but EPA did make minor adjustments
to the regulatory framework for atrazine based on the elevated pollution
by that herbicide. Recently, atrazine was found to potentiate arsenic
toxicity in human cells, a result that causes concern in areas where
drinking water is polluted with both toxins. Even though cancer has been
a focus of regulatory action on the herbicide, impacts such as the
intra-uterine growth retardation observed in communities with
atrazine-polluted drinking water supplies have been given scant
consideration.

Atrazine can be present in parts per million in agricultural run-offs
and can reach 40 parts per billion in precipitation. The global impact
of atrazine is staggering. Significant atrazine pollution has been found
in the Lio-He and Yangtse rivers of China, and a review of the
atmospheric dispersion of atrazine shows impacts of the herbicide even
in isolated areas of the globe.

Prompt action to limit further pollution from atrazine may be delayed by
the development of "super weeds" from current herbicide tolerant GM
crops, and volunteer crops or weeds that develop multiple-herbicide
tolerance by gene flow between commercial varieties. Some authorities
and government regulators advise that herbicides such as atrazine should
be used to control superweeds. This is the height of lunacy and
irresponsibility. There should be a global ban on atrazine.
This article can be found on the I-SIS website at
http://www.i-sis.org.uk/atrazine.php