19
Oct
Atrazine Exposure Leads to Fewer Male, More Female Frogs
(Beyond Pesticides, October 19, 2017) Exposure to the second most commonly used herbicide in the U.S., atrazine, results in a lower proportion of male frogs in populations of Blanchard’s 
cricket frogs, according to researchers from Ohio’s Miami University. While it may be ostensibly easy to dismiss the results of this study as limited to a single frog species, the Blanchard cricket frog, with its populations concentrated in heavily farmed Midwestern states, is likely an important indicator of broader ecological impacts. Ultimately, only a transition away from toxic herbicides and towards integrated organic systems will successfully address the ongoing effects of industrial agrichemicals on amphibians.
Miami researchers exposed frogs to varying concentrations of atrazine, 0.1, 1, and 10 μg/L, in the laboratory, in order to investigate sex ratios and potential effects on survival of the population. Although no significant effects were seen on survival rate during the course of the study, sex ratios were significantly altered at the 0.1 and 10 μg/L exposure concentrations. At these levels, populations developed 51 and 55% fewer males respectively than control frogs.
Researchers point out that such significant results seen at such low concentrations likely indicates that sex ratios are also skewed in the wild. It is noteworthy that effects seen at 0.1 μg/L, the lowest concentration tested, are lower than the range that the U.S. Environmental Protection Agency (EPA) estimates atrazine will alter sex ratios. EPA indicates that a range between 0.92 and 124 μg/L is likely to skew amphibian sex ratios. This discrepancy, scientists hypothesize, is likely related to the current study’s use of a formulated atrazine product, rather than technical grade atrazine. At the present time, EPA only tests the effects of the active ingredient in a pesticide formulation, and does not consider the impacts of formulations, which often include other active ingredients alongside ‘inert’ ingredients, all of which can increase or decrease the toxicity of the active ingredient. Not only have environmental groups criticized EPA for its repeated failure to test the impacts of pesticide formulations, but earlier this year the agency’s Inspector General called for additional testing of pesticide mixtures.
Skewed sex ratios negatively alter population dynamics, as they influence the maximum rate of population growth and the allocation of ecological resources to either males or females over the course of evolution. The study explains, “EDC [endocrine disrupting chemical]-mediated sex reversal may have important implications for the persistence of wild amphibians, which are facing rapid global declines.”
This is far from the first study showing atrazine’s ability to influence the sex of amphibians. Renowned scientist Tyrone Hayes, PhD, of the University of California Berkeley, has published extensive research documenting a range of impacts to various amphibian species. Results have shown the ability for atrazine not only to skew sex ratios, but also hermaphrodize male frogs, and in some cases make male frogs completely female with the ability to lay eggs.
Scientists, like Dr. Hayes, pushing for the elimination of atrazine in the environment have been attacked by the chemical industry. Syngenta, the main manufacturer of atrazine, has harassed and attempted to discredit his work, as documented in an extensive 2014 report in The New Yorker.
While the adverse effects of this chemical on amphibians are alarming, they are not limited to amphibians. Research on atrazine has found impacts relating to cancer, birth defects, reproductive impacts, kidney/liver damage, and neurotoxicity in humans. A study published just last month found that atrazine hazards affect health across multiple generations, with the grandchildren of rats exposed to atrazine, but never exposed themselves, displaying increased rates of testicular diseases, early onset puberty, and mammary tumors.
Beyond health and the environment, studies show that atrazine use doesn’t even make economic sense. Peer-reviewed research finds that eliminating atrazine in corn production would increase on-farm revenues by 3.2%, resulting in a net benefit of $1.7 billion to farmers. And organic agriculture provides a viable alternative to chemical-intensive food production systems that often employ atrazine or other toxic herbicides. Rather than use hazardous products, organic agriculture focuses on improving soil biology and uses mechanical and cultural weed management, including weed whacking, solarization, cover cropping, and crop rotation to manage weed intrusion.
For more information about the effects of atrazine on amphibian populations, see Dr. Hayes talk to Beyond Pesticides 33rd National Pesticide Forum in Orlando, FL. Or read an abridged version of his presentation on atrazine published in Beyond Pesticides’ journal, Pesticides and You.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source: Phys.org
