Study validates concerns about chlorothalonil

by Michael Howell –

Back in the mid 1990s local wildlife rehabilitator Judy Hoy raised a cry of alarm about the high incidence of developmental malformations in local wildlife that she was observing. She had begun to observe and document a rising incidence of malformations in White-tailed deer in the Bitterroot Valley. The malformations included a high incidence of brachygnathia superior, or under bite, and malformations of the male genitalia including undescended testicles and misaligned hemiscota (that is one scrotal sac aligned behind the other rather than side by side).
Her efforts to bring the situation to the attention of state wildlife authorities fell on deaf ears, however, as FWP biologists disputed her claims about the deer. But Hoy was also observing and documenting deformations among birds and domesticated mammals including horses, goats and cattle and it bothered her tremendously. So she persisted and brought in a physician and veterinarian from Wisconsin, William Croft, who agreed to examine the case and then backed up Hoy’s assessment that out of 144 whitetail deer bucks examined 70 showed signs of abnormal development.
Hoy teamed up with some local scientists and other professionals and authored an article published in the Journal of Environmental Biology in 2001 (Hoy, J.A., Hoy, R.D., Seba, D. & Kerstetter, T.H. 2002. Genital  abnormalities in White-tailed deer (Odocoileus virginianus) in 
west-central Montana: Pesticide exposure as a possible cause. J Environ  Biol 23: 189-197. PMid:12602857) describing the documented malformations and establishing that these were all similar to the type of deformations seen in cases of  hyperthyroidism. This was their clue to look for potential endocrine disprupters, according to Hoy. The scientific article pointed to the possibility that the fungicide chlorothalonil could be involved.
Since that time reports from across the nation and around the world have been published documenting a high incidence of deformations among various wildlife populations, especially amphibians.  Endocrine disprupting chemicals in the environment have been identified as a possible cause.
Hoy said that a sample of snow water taken in the Bitterroot in 1999 had tested positive for the chemical chlorothalonil, which studies indicate may be an endocrine disruptor. Discovered in the sample was 0.03 ppb of chlorothalonil and 9 times that much of a metabolite and 4 times that much of another metabolite, for about 0.42 ppb total or actually more because the recovery rate was low according to the Billings Energy Laboratory where the testing was done.
The mystery, according to Hoy, was that nobody was using chlorothalonil at that time in the valley, according to the local Agricultural Extension agent. But as she looked into its use she discovered that the valley was surrounded by fields where the chemical was being used in Washington, Oregon and Idaho. (see graph)
This hypothesis, that the fungicide being sprayed on potato fields in neighboring states might be drifting into Montana was also met with a great deal of skepticism. It took another study, done in 2008 by a team headed by Diane Henshel of Indiana University (Frost, K.D., Ruhter, M. & Zhang, D. 2008. Baseline Risk Assessment  Bitterroot Valley, Montana, Indiana University, Bloomington, IN, May 2008), to confirm that particulates such as pesticides and fungicides are carried, along with dust, great distances before being deposited on landscapes far from their place of application. The prevailing winds and the amount of chemicals being sprayed almost assure that some deposit is occurring in the Bitterroot from Washington, Idaho and Oregon, according to the study.
Hoy notes that chlorothalonil is made up of four chlorine molecules and two molecules of cyanide. When the chemical burns the cyanide molecules are released.
“If the chemical is drifting in and settling on our forests, when they burn it would make the smoke toxic,” said Hoy. She said that cyanide is a known carcinogen and causes cancer.
Another criticism often raised in the past was that the amount of chlorothalonil that might be drifting in would not be enough to have any harmful effects. Recent studies suggest, however, that very low doses can have significant effects.
A study of the effects of chlorothalonil on amphibians was recently published in April 2011 in Environmental Health Perspective, a publication of the National Institute of Environmental Health Sciences, a division of the National Institutes of Health at the U.S. Department of Health and Human Services. (The Fungicide Chlorothalonil is Nonlinearly Associated with Corticosterone Levels, Immunity, and Mortality in Amphibians; Taegan McMahon, Neal Halstead, Steve Johnson, Thomas R. Raffel, John M. Romansic, Patrick W. Crumrine, Raoul K. Boughton, Lynn B. Martin, and Jason R. Rohr doi: 10.1289/ehp.1002956 (available at http://dx.doi.org/) Online 4 April 2011)
The study set out to “quantify amphibian responses to chlorothalonil, the most commonly used synthetic fungicide in the United States.”
The conclusion: “Chlorothalonil killed nearly every amphibian at EEC  (expected environmental contamination levels) and, at concentrations to which humans are commonly exposed, it increased mortality and was associated with elevated corticosterone levels and changes in immune cells. Future studies should directly quantify the effects of chlorothalonil on amphibian populations and human health.”
Four separate experiments were conducted, three in the laboratory and one in the field.
“Together, these four experiments indicate that amphibians, in general, are susceptible to the EEC of chlorothalonil and that even low concentrations can cause amphibian mortality and physiological stress responses. Given that chlorothalonil caused nearly 100% mortality at the EEC, caused significant mortality four orders of magnitude below the EEC, and caused immunomodulation in surviving individuals, exposure to this chemical has the potential to both directly and indirectly cause amphibian declines. Indeed, frog die-offs have been reported after chlorothalonil applications to cranberry bogs (Winkler et al. 1996) and, in neotropical montane regions where amphibians are declining, chlorothalonil has been regularly detected at levels causing significant mortality in this study (Daly et al. 2007). This makes chlorothalonil a plausible contributor to declines, though additional work is needed to demonstrate a causal link. Given these findings and similarities between the vital systems of amphibians and humans, we encourage future studies to quantify the effects of chlorothalonil on amphibian populations and human health.”
Hoy is hoping, of course, that many additional studies will be done. She even has a few of her own devised if she can get the funding.
“And then there’s the problem of getting people, especially people in the government, to take these studies seriously,” said Hoy.
Hoy said that the percentages of abnormalities that she has documented in the White-tailed deer population in the Bitterroot present on ongoing mystery. She said that incidences of no scrotal sac have declined significantly, but incidences of misalignment of the hemiscrota are increasing again after undergoing a steady decline for years.
It is mysterious, but Hoy has her suspicions. It involves a new batch of chemicals that is coming into popular use, called neonicatinoids.
“Neonicotinoids  have been shown to be deadly to bees and other beneficial insects and when the insects are exposed to both chlorothalonil and neonicotinoids simultaneously, the combination is even more deadly. The same is likely true of developing young exposed to both simultaneously,” she said.
Hoy said that if things keep going in this direction that in ten or twelve years someone might finally do a study on the effects of these new nicotine based chemicals and maybe even the combination of a few of these chemicals on humans.
“It would be nice if we did it before we go extinct,’ said Hoy.