FROGS GIVE WARNING
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FROGS GIVE WARNING
The WASHINGTON POST reported September 30 that frogs with severe
birth defects have been discovered during the past two summers in
54 of Minnesota's 87 counties, across Wisconsin, and up into
the St. Lawrence River Valley in Quebec, Canada.
According to the POST, herpetologists (scientists who study
amphibians and reptiles) have reported finding frogs with missing
legs, extra legs, misshapen legs, paralyzed legs that stuck out
from the body at odd places, legs that were webbed together with
extra skin, legs that were fused to the body, and legs that split
into two half-way down. They have also found frogs with missing
eyes. One one-eyed frog had a second eye growing inside its
Robert McKinnell, a geneticist and cancer researcher at
University of Minnesota (St. Paul, Minn.), said he initially
thought the reports of deformed frogs didn't amount to much.
Frogs have a small number of birth defects naturally. Then
McKinnell began visiting various sites in Minnesota and finding a
large proportion of deformed frogs (96% at one site). Now he
says, "The whole state appears to be affected. We should be
Frogs are amphibians. They spend their lives both in the water
and on dry land. Beginning life as eggs floating on the surface
of still waters, they develop into swimming tadpoles, eventually
changing completely, becoming frogs. These major changes in form
occur under the control of hormones, which are chemical
messengers that travel throughout the organism, turning on and
off bodily processes.
Since August, 1995, when the first deformed frogs were found in
south-central Minnesota, researchers have been searching for the
cause, without success. So far, they say, they believe inherited
genetic mutations are not involved. This would mean the
deformities are being caused by something that affects the frogs
during early life, when they are eggs or tadpoles. Judy Helgen,
the research scientist who is leading the investigation on behalf
of the Minnesota Pollution Control Agency says she thinks the
cause will eventually be discovered to be chemicals of some kind,
though it could take several years to pin it down.
Little research has been done to study the effects of
environmental chemicals on amphibians. It seems that most
researchers have been focused on confirming or refuting the
reported worldwide decline in populations of frogs, toads and
salamanders. (See REHW #246, #380.) Indeed, some of the
recently-reported declines are large, mysterious and compelling.
For example, a study published in April compared amphibian
populations in 1915 vs. 1992 in Yosemite Park in California. The
study found that seven kinds of amphibians are declining in
numbers, and three have disappeared entirely from Yosemite.
Yosemite isn't truly pristine because of air pollution from
distant cities, but it is about as clean an environment as you
can find in the lower 48 states. Dr. Ronald Heyer, a researcher
with the Smithsonian Institution (and chair of the Declining
Amphibian Populations Task Force [DAPTF] of the World
Conservation Union's Species Survival Commission) says, "It's
kind of chilling in its effect. Here we have what we consider to
be a relatively protected place, and amphibian declines are
occurring even there."
Amphibians are particularly sensitive to chemical pollution
because they live both in water and on land. Furthermore, they
breathe through their skin. Some researchers suspect that toxic
heavy metals and pesticides building up in aquatic food chains,
plus serious air pollution, may be what's killing some frogs,
toads, and salamanders.
Many researchers now believe that increased ultraviolet radiation
may be affecting frogs' eggs, which float on the surface of the
water, absorbing sunlight.
Despite scientists' intense focus on population decline and
extinction, recent studies have begun to try to find the causes
of birth defects in frogs in Minnesota and Wisconsin.
At the Great Lakes Declining Amphibians Conference in Milwaukee
March 30, Robin E. Jung from the University of Wisconsin at
Madison described new studies indicating that leopard frogs
collected at a PCB-contaminated site on the Fox River in
Wisconsin had more spinal deformities than frogs collected at a
cleaner Green Bay site.
A few previous studies had linked frog deformities to
pesticides.[5,6,7] Still, to date, remarkably little testing has
been done to see if environmental chemicals cause birth defects
On the other hand, a recent large study has linked birth defects
in humans to pesticide use in Minnesota.
Researchers from the University of Minnesota and the U.S.
Environmental Protection Agency (EPA) linked the Minnesota birth
registry for the years 1989-1992 with information about pesticide
use across the state.
Two pictures emerged: (1) the birth defect rate for all birth
defects was significantly increased in children born to private
pesticide appliers, compared to the general population; and (2)
births in the general population of western Minnesota (the area
of highest use of pesticides) showed a significant increase in
birth defects, compared to the rest of the state. This second
effect was most pronounced among children conceived during the
Researchers from the University of Minnesota and the U.S.
Environmental Protection Agency (EPA) examined 210,723 birth
records in the state of Minnesota covering the four-year period
They first focused on 4935 children born to state-licensed
private pesticide appliers in Minnesota (of which there are
34,772). They found statistically significant elevations in the
occurrence of all birth defects taken together, as well as in
specific subcategories of birth defects: circulatory/respiratory
defects, musculoskeletal defects; and urogenital defects.
Secondly, they focused on the general public. They divided the
state into two regions, agricultural and non-agricultural. They
found that "data show that families residing in predominantly
agricultural regions of Minnesota are more likely to have
children with birth anomalies." This finding was statistically
Third, they subdivided the agricultural part of Minnesota into
smaller areas, based on the kinds of crops that dominate. They
then examined 12 specific herbicides. The most consistent
results were obtained for the herbicides 2,4-D and MCPA
[4-chloro-2-methylphenoxyacetic acid]. Areas designated by the
Minnesota Department of Agriculture as "high use" areas for these
herbicides, when compared against "low use" areas, had
significantly increased birth defects (about an 86% increase) for
defects of the central nervous system, circulatory/respiratory,
urogenital, and musculoskeletal systems, as well as a 51%
increase for all birth defects combined.
In regions where chlorophenoxy herbicides are in use (such as
2,4-D and MCPA), infants conceived in the spring had about 30%
more birth defects than infants conceived in other seasons. This
effect was not noted in regions reporting low or no use of
The researchers reported that in the five counties with the
highest reported use of 2,4-D herbicide, registered appliers gave
birth to only half as many children in 1990 as did the general
population. The researchers noted that this finding was
consistent with an earlier study showing that 2,4-D is toxic to
sperm in pesticide appliers.
Finally, the researchers observed that the sex ratio of live
births is usually in the range of 104 to 107 males born for each
100 females. In Minnesota in 1989-1992, the sex ratio was 105
males to 100 females for normal births and 138 males to 100
females for births with defects. The researchers say they believe
something in the pesticides used in Minnesota is suppressing the
births of female children or favoring the births of males.
Interestingly, a recent study examined the sex ratio among the
first 74 children born to parents exposed to dioxin during an
industrial accident at Seveso, Italy. Among highly
dioxin-exposed parents, female children outnumbered males (26
males vs. 48 females, a ratio of 54 males for every 100 females).
This skewed sex ratio lasted for 8 years after the Seveso
accident, then returned to normal.
Children may be the victims of pesticides and dioxin, yet they
still offer hope. The first deformed frogs were discovered in
Minnesota in August 1995 by middle school children --10 year olds
--on a field trip to a farm. After they noticed a one-legged
frog, they started collecting others. In a morning they
collected 22 frogs, 11 of them with major birth defects. "I
think the kids got kind of scared," says their teacher, Cindy
Reinitz. "They immediately started asking me what the cancer rate
was in the area." Now that's an impressive question from a group
of 10 year olds. When all our health officials and corporate
CEOs are as alert, insightful and concerned as those children,
we'll no longer have to rely on frogs to give us warning.
(National Writers Union, UAW Local 1981/AFL-CIO)
 William Souder, "Hundreds of Deformed Frogs Pose
Environmental Warning," WASHINGTON POST September 30, 1996, pg.
 C.A. Drost and G.M. Fellers, "Collapse of a Regional Frog
Fauna in the Yosemite Area of the California Sierra Nevada,"
CONSERVATION BIOLOGY Vol. 10 No. 2 (1996), pgs. 414-425.
 Carol Kaesuk Yoon, "Eerie Quiet of Frogs and Toads Isn't Part
of Normal Cycle, Study Says," NEW YORK TIMES April 30, 1996, pg.
 Robin E. Jung and others, "Amphibian Ecotoxicology in Green
Bay, Wisconsin: are toxicants influencing amphibian
distributions?" a paper presented at the Great Lakes Declining
Amphibians Conference March 30, 1996, at the Milwaukee
[Wisconsin] Public Museum. An abstract of this paper is available
on the world wide web:
 Gerald S. Schuytema and others, "Teratogenesis, Toxicity and
Bioconcentration in Frogs Exposed to Dieldrin," ARCHIVES OF
ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY Vol. 21 (1991), pgs.
332-350. Schuytema reports that he could produce "gross spinal
deformities" by exposing African clawed frogs to 1.3 parts per
billion (ppb) of dieldrin in water and in bullfrogs at 25.4 ppb.
See pg. 341.
 G.S. Schuytema and others, "Toxicity of Guthion and Guthion
2S to XENOPUS LAEVIS Embryos," ARCHIVES OF ENVIRONMENTAL
CONTAMINATION AND TOXICOLOGY, Vol. 27 No. 2 (August 1994), pgs.
250-255. In this study, Schuytema says he believes it is the
"inert" ingredients in the pesticides that cause the toxicity of
Guthion (an organophosphate) to frogs. So-called "inerts" are
secret ingredients in pesticides; many "inerts" are not inert at
all, but are chemically active and toxic. By federal law the
public (including scientific researchers) are prohibited from
knowing what "inert ingredients" have been added to a pesticide.
 R. Alvarez and others, "Skeletal Malformations Induced by the
Insecticides ZZ-Aphox and Folidol During Larval Development of
RANA PEREZI," ARCHIVES OF ENVIRONMENTAL CONTAMINATION AND
TOXICOLOGY Vol. 28 (1995), pgs. 349-356.
 Vincent F. Garry and others, "Pesticide Appliers, Biocides, and Birth
Defects in Rural Minnesota," ENVIRONMENTAL HEALTH PERSPECTIVES Vol. 104, No.
4 (April, 1996), pgs. 394-399.
 Paolo Mocarelli, Paolo Brambilla, Pier Mario Gerthoux, Donald
G. Patterson, Jr., Larry L. Needham, "Change in Sex Ratio with
Exposure to Dioxin," THE LANCET Vol. 348 No. 9024 (August 10,
1996), pg. 409.
Descriptor terms: frogs; amphibians; wildlife; birth defects;
teratogens; pesticides; pcbs; species loss; yosemite; california;
air pollution; ultraviolet radiation; fox river; wi; mn; green
bay; children; dioxin; sex ratio; seveso; italy; extinction;
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