A researcher: Tyrone Hayes at the University of California Berkeley was doing research on the environmental impact of herbicides
The video shows how experimentally genetic male frogs can be changed into females by exposure to a commonly used herbicide.
That this is possible probably seems very strange to those who don't know volumes about biology but this is not without precedent. There is the charnov-bull principle of sex determination that shows that some reptiles change sex while in the egg due to the ambient temperature because the physiology of the different sexes have different survival rates dependent on temperature Amphibans have long been known to be very sensitive to chemicals. I have heard it said that this is due to their thin and porous skin.
In fact back in the days before instant pregnancy tests they would take blood or urine from a woman and inject it into an african clawed frog Xenopus laevis and if it developed eggs then that means the human woman had these reproductive hormones at high levels and was likely pregnant.
Still, this is very striking because we usually think of sex as something set in stone.
This brings up some ecological questions such as what ecological effects this will have.
It is generally said that females are the limiting sex and that as long as there are a few males around the population can continue to survive. This probably does matter on the mating style. Amphibians for example often use the "big bang" method where there are just a few nights where actual mating takes place. Since it takes a while for sperm to mature it might not be possible for one male to fertilize more than one female's clutch of eggs.This will is just the sort of thing that produces interesting population genetic scenarios.
Also, maybe this could illustrate the Baldwin effect. Perhaps if males are largely turning into females that there could be a selective advantage to decreased sensitivity to whatever environmental factors are affecting sex ratios.
It should be said though that if you search for information on atrazine you will find astroturf, google bombed links and such sponsored by agribusiness-- reminiscent of big tobacco and climate deniers so be advised.