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 throat.
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
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
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
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,
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 in frogs.
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 spring.
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 1989-1992.
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
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 significant.
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 chlorophenoxy herbicides.
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.
--Peter Montague (National Writers Union, UAW Local 1981/AFL-CIO)
 William Souder, "Hundreds of Deformed Frogs Pose Environmental
Warning," WASHINGTON POST September 30, 1996, pg. A1.
 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. C4.
 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
 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;