The magnitude and duration of exposure is probably lower, since plastic is a western and relatively recent invention.

Moreover, it is precisely because transgenderism is primarily a cultural (rather than biological) phenomenon, that rates between two otherwise identical populations are going to differ based on the culture's attitude toward transgenderism and the likelihood that a doctor is to diagnose someone with gender dysphoria.

That latter point is severely understudied because transgenderism is one of the wests many recent sacred cows which are beyond criticism. But overdiagnosis should be a much greater concern than it is. Especially since puberty blockers and hormones given to adolescent boys will undoubtedly exacerbate any feelings of dysphoria and I am astounded that no one is talking about the reinforcing effects of these "treatments".

But I digress. Point being comparing rates of transgenderism between first and third worlds is like comparing apples to oranges because transgenderism is a cultural phenomenon.